xref: /freebsd/sys/netinet/tcp_input.c (revision 831ad37ef267beba5b1c0f04ad34e53255fc5fb9)
1c398230bSWarner Losh /*-
2e79adb8eSGarrett Wollman  * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
3df8bae1dSRodney W. Grimes  *	The Regents of the University of California.  All rights reserved.
4dbc42409SLawrence Stewart  * Copyright (c) 2007-2008,2010
5dbc42409SLawrence Stewart  *	Swinburne University of Technology, Melbourne, Australia.
6dbc42409SLawrence Stewart  * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org>
7dbc42409SLawrence Stewart  * Copyright (c) 2010 The FreeBSD Foundation
8fa046d87SRobert Watson  * Copyright (c) 2010-2011 Juniper Networks, Inc.
9dbc42409SLawrence Stewart  * All rights reserved.
10dbc42409SLawrence Stewart  *
11dbc42409SLawrence Stewart  * Portions of this software were developed at the Centre for Advanced Internet
12891b8ed4SLawrence Stewart  * Architectures, Swinburne University of Technology, by Lawrence Stewart,
13891b8ed4SLawrence Stewart  * James Healy and David Hayes, made possible in part by a grant from the Cisco
14891b8ed4SLawrence Stewart  * University Research Program Fund at Community Foundation Silicon Valley.
15dbc42409SLawrence Stewart  *
16dbc42409SLawrence Stewart  * Portions of this software were developed at the Centre for Advanced
17dbc42409SLawrence Stewart  * Internet Architectures, Swinburne University of Technology, Melbourne,
18dbc42409SLawrence Stewart  * Australia by David Hayes under sponsorship from the FreeBSD Foundation.
19df8bae1dSRodney W. Grimes  *
20fa046d87SRobert Watson  * Portions of this software were developed by Robert N. M. Watson under
21fa046d87SRobert Watson  * contract to Juniper Networks, Inc.
22fa046d87SRobert Watson  *
23df8bae1dSRodney W. Grimes  * Redistribution and use in source and binary forms, with or without
24df8bae1dSRodney W. Grimes  * modification, are permitted provided that the following conditions
25df8bae1dSRodney W. Grimes  * are met:
26df8bae1dSRodney W. Grimes  * 1. Redistributions of source code must retain the above copyright
27df8bae1dSRodney W. Grimes  *    notice, this list of conditions and the following disclaimer.
28df8bae1dSRodney W. Grimes  * 2. Redistributions in binary form must reproduce the above copyright
29df8bae1dSRodney W. Grimes  *    notice, this list of conditions and the following disclaimer in the
30df8bae1dSRodney W. Grimes  *    documentation and/or other materials provided with the distribution.
31df8bae1dSRodney W. Grimes  * 4. Neither the name of the University nor the names of its contributors
32df8bae1dSRodney W. Grimes  *    may be used to endorse or promote products derived from this software
33df8bae1dSRodney W. Grimes  *    without specific prior written permission.
34df8bae1dSRodney W. Grimes  *
35df8bae1dSRodney W. Grimes  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
36df8bae1dSRodney W. Grimes  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
37df8bae1dSRodney W. Grimes  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
38df8bae1dSRodney W. Grimes  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
39df8bae1dSRodney W. Grimes  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
40df8bae1dSRodney W. Grimes  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
41df8bae1dSRodney W. Grimes  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
42df8bae1dSRodney W. Grimes  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
43df8bae1dSRodney W. Grimes  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
44df8bae1dSRodney W. Grimes  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
45df8bae1dSRodney W. Grimes  * SUCH DAMAGE.
46df8bae1dSRodney W. Grimes  *
47e79adb8eSGarrett Wollman  *	@(#)tcp_input.c	8.12 (Berkeley) 5/24/95
48df8bae1dSRodney W. Grimes  */
49df8bae1dSRodney W. Grimes 
504b421e2dSMike Silbersack #include <sys/cdefs.h>
514b421e2dSMike Silbersack __FBSDID("$FreeBSD$");
524b421e2dSMike Silbersack 
53f9e354dfSJulian Elischer #include "opt_ipfw.h"		/* for ipfw_fwd	*/
541cfd4b53SBruce M Simpson #include "opt_inet.h"
55fb59c426SYoshinobu Inoue #include "opt_inet6.h"
563a2a9f79SYoshinobu Inoue #include "opt_ipsec.h"
570cc12cc5SJoerg Wunsch #include "opt_tcpdebug.h"
580cc12cc5SJoerg Wunsch 
59df8bae1dSRodney W. Grimes #include <sys/param.h>
6098163b98SPoul-Henning Kamp #include <sys/kernel.h>
6139bc9de5SLawrence Stewart #include <sys/hhook.h>
62df8bae1dSRodney W. Grimes #include <sys/malloc.h>
63df8bae1dSRodney W. Grimes #include <sys/mbuf.h>
64a29f300eSGarrett Wollman #include <sys/proc.h>		/* for proc0 declaration */
65df8bae1dSRodney W. Grimes #include <sys/protosw.h>
6657f60867SMark Johnston #include <sys/sdt.h>
67960ed29cSSeigo Tanimura #include <sys/signalvar.h>
68df8bae1dSRodney W. Grimes #include <sys/socket.h>
69df8bae1dSRodney W. Grimes #include <sys/socketvar.h>
70960ed29cSSeigo Tanimura #include <sys/sysctl.h>
71816a3d83SPoul-Henning Kamp #include <sys/syslog.h>
72960ed29cSSeigo Tanimura #include <sys/systm.h>
73df8bae1dSRodney W. Grimes 
74e79adb8eSGarrett Wollman #include <machine/cpu.h>	/* before tcp_seq.h, for tcp_random18() */
75e79adb8eSGarrett Wollman 
7612e2e970SAndre Oppermann #include <vm/uma.h>
7712e2e970SAndre Oppermann 
78df8bae1dSRodney W. Grimes #include <net/if.h>
7976039bc8SGleb Smirnoff #include <net/if_var.h>
80df8bae1dSRodney W. Grimes #include <net/route.h>
81530c0060SRobert Watson #include <net/vnet.h>
82df8bae1dSRodney W. Grimes 
83773673c1SAndre Oppermann #define TCPSTATES		/* for logging */
84773673c1SAndre Oppermann 
85dbc42409SLawrence Stewart #include <netinet/cc.h>
86df8bae1dSRodney W. Grimes #include <netinet/in.h>
8757f60867SMark Johnston #include <netinet/in_kdtrace.h>
88960ed29cSSeigo Tanimura #include <netinet/in_pcb.h>
89df8bae1dSRodney W. Grimes #include <netinet/in_systm.h>
90960ed29cSSeigo Tanimura #include <netinet/in_var.h>
91df8bae1dSRodney W. Grimes #include <netinet/ip.h>
928e8aab7aSAndre Oppermann #include <netinet/ip_icmp.h>	/* required for icmp_var.h */
93686cdd19SJun-ichiro itojun Hagino #include <netinet/icmp_var.h>	/* for ICMP_BANDLIM */
94df8bae1dSRodney W. Grimes #include <netinet/ip_var.h>
95ef39adf0SAndre Oppermann #include <netinet/ip_options.h>
96686cdd19SJun-ichiro itojun Hagino #include <netinet/ip6.h>
97686cdd19SJun-ichiro itojun Hagino #include <netinet/icmp6.h>
98686cdd19SJun-ichiro itojun Hagino #include <netinet6/in6_pcb.h>
99960ed29cSSeigo Tanimura #include <netinet6/ip6_var.h>
100960ed29cSSeigo Tanimura #include <netinet6/nd6.h>
101df8bae1dSRodney W. Grimes #include <netinet/tcp_fsm.h>
102df8bae1dSRodney W. Grimes #include <netinet/tcp_seq.h>
103df8bae1dSRodney W. Grimes #include <netinet/tcp_timer.h>
104df8bae1dSRodney W. Grimes #include <netinet/tcp_var.h>
105fb59c426SYoshinobu Inoue #include <netinet6/tcp6_var.h>
106df8bae1dSRodney W. Grimes #include <netinet/tcpip.h>
107c325962bSMike Silbersack #include <netinet/tcp_syncache.h>
108610ee2f9SDavid Greenman #ifdef TCPDEBUG
109df8bae1dSRodney W. Grimes #include <netinet/tcp_debug.h>
110fb59c426SYoshinobu Inoue #endif /* TCPDEBUG */
11109fe6320SNavdeep Parhar #ifdef TCP_OFFLOAD
11209fe6320SNavdeep Parhar #include <netinet/tcp_offload.h>
11309fe6320SNavdeep Parhar #endif
114fb59c426SYoshinobu Inoue 
115b2630c29SGeorge V. Neville-Neil #ifdef IPSEC
116b9234fafSSam Leffler #include <netipsec/ipsec.h>
117b9234fafSSam Leffler #include <netipsec/ipsec6.h>
118b2630c29SGeorge V. Neville-Neil #endif /*IPSEC*/
119b9234fafSSam Leffler 
120db4f9cc7SJonathan Lemon #include <machine/in_cksum.h>
121db4f9cc7SJonathan Lemon 
122aed55708SRobert Watson #include <security/mac/mac_framework.h>
123aed55708SRobert Watson 
124dbc42409SLawrence Stewart const int tcprexmtthresh = 3;
1250312fbe9SPoul-Henning Kamp 
126773673c1SAndre Oppermann int tcp_log_in_vain = 0;
127816a3d83SPoul-Henning Kamp SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
128eddfbb76SRobert Watson     &tcp_log_in_vain, 0,
129eddfbb76SRobert Watson     "Log all incoming TCP segments to closed ports");
130816a3d83SPoul-Henning Kamp 
13182cea7e6SBjoern A. Zeeb VNET_DEFINE(int, blackhole) = 0;
13282cea7e6SBjoern A. Zeeb #define	V_blackhole		VNET(blackhole)
133eddfbb76SRobert Watson SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
134eddfbb76SRobert Watson     &VNET_NAME(blackhole), 0,
135eddfbb76SRobert Watson     "Do not send RST on segments to closed ports");
13616f7f31fSGeoff Rehmet 
13782cea7e6SBjoern A. Zeeb VNET_DEFINE(int, tcp_delack_enabled) = 1;
138eddfbb76SRobert Watson SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
139eddfbb76SRobert Watson     &VNET_NAME(tcp_delack_enabled), 0,
1403d177f46SBill Fumerola     "Delay ACK to try and piggyback it onto a data packet");
141f498eeeeSDavid Greenman 
14282cea7e6SBjoern A. Zeeb VNET_DEFINE(int, drop_synfin) = 0;
14382cea7e6SBjoern A. Zeeb #define	V_drop_synfin		VNET(drop_synfin)
144eddfbb76SRobert Watson SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
145eddfbb76SRobert Watson     &VNET_NAME(drop_synfin), 0,
146eddfbb76SRobert Watson     "Drop TCP packets with SYN+FIN set");
147f8613305SDag-Erling Smørgrav 
14882cea7e6SBjoern A. Zeeb VNET_DEFINE(int, tcp_do_rfc3042) = 1;
14982cea7e6SBjoern A. Zeeb #define	V_tcp_do_rfc3042	VNET(tcp_do_rfc3042)
150eddfbb76SRobert Watson SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW,
151eddfbb76SRobert Watson     &VNET_NAME(tcp_do_rfc3042), 0,
152eddfbb76SRobert Watson     "Enable RFC 3042 (Limited Transmit)");
153582a954bSJeffrey Hsu 
15482cea7e6SBjoern A. Zeeb VNET_DEFINE(int, tcp_do_rfc3390) = 1;
155eddfbb76SRobert Watson SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW,
156eddfbb76SRobert Watson     &VNET_NAME(tcp_do_rfc3390), 0,
157da3a8a1aSJeffrey Hsu     "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
158da3a8a1aSJeffrey Hsu 
15909440655SAndre Oppermann SYSCTL_NODE(_net_inet_tcp, OID_AUTO, experimental, CTLFLAG_RW, 0,
16009440655SAndre Oppermann     "Experimental TCP extensions");
16109440655SAndre Oppermann 
16209440655SAndre Oppermann VNET_DEFINE(int, tcp_do_initcwnd10) = 1;
16309440655SAndre Oppermann SYSCTL_VNET_INT(_net_inet_tcp_experimental, OID_AUTO, initcwnd10, CTLFLAG_RW,
16409440655SAndre Oppermann     &VNET_NAME(tcp_do_initcwnd10), 0,
165b8b4cfcdSSergey Kandaurov     "Enable RFC 6928 (Increasing initial CWND to 10)");
16609440655SAndre Oppermann 
16782cea7e6SBjoern A. Zeeb VNET_DEFINE(int, tcp_do_rfc3465) = 1;
168eddfbb76SRobert Watson SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_RW,
169eddfbb76SRobert Watson     &VNET_NAME(tcp_do_rfc3465), 0,
17024cb0f22SLawrence Stewart     "Enable RFC 3465 (Appropriate Byte Counting)");
171eddfbb76SRobert Watson 
17282cea7e6SBjoern A. Zeeb VNET_DEFINE(int, tcp_abc_l_var) = 2;
173eddfbb76SRobert Watson SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_RW,
174eddfbb76SRobert Watson     &VNET_NAME(tcp_abc_l_var), 2,
17524cb0f22SLawrence Stewart     "Cap the max cwnd increment during slow-start to this number of segments");
17624cb0f22SLawrence Stewart 
1776472ac3dSEd Schouten static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, CTLFLAG_RW, 0, "TCP ECN");
178f2512ba1SRui Paulo 
17982cea7e6SBjoern A. Zeeb VNET_DEFINE(int, tcp_do_ecn) = 0;
180eddfbb76SRobert Watson SYSCTL_VNET_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_RW,
181eddfbb76SRobert Watson     &VNET_NAME(tcp_do_ecn), 0,
182eddfbb76SRobert Watson     "TCP ECN support");
183eddfbb76SRobert Watson 
18482cea7e6SBjoern A. Zeeb VNET_DEFINE(int, tcp_ecn_maxretries) = 1;
185eddfbb76SRobert Watson SYSCTL_VNET_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_RW,
186eddfbb76SRobert Watson     &VNET_NAME(tcp_ecn_maxretries), 0,
187eddfbb76SRobert Watson     "Max retries before giving up on ECN");
188eddfbb76SRobert Watson 
18982cea7e6SBjoern A. Zeeb VNET_DEFINE(int, tcp_insecure_rst) = 0;
19082cea7e6SBjoern A. Zeeb #define	V_tcp_insecure_rst	VNET(tcp_insecure_rst)
191eddfbb76SRobert Watson SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW,
192eddfbb76SRobert Watson     &VNET_NAME(tcp_insecure_rst), 0,
1936489fe65SAndre Oppermann     "Follow the old (insecure) criteria for accepting RST packets");
194a69968eeSMike Silbersack 
195fba0cea1SBjoern A. Zeeb VNET_DEFINE(int, tcp_recvspace) = 1024*64;
196873789cbSAndre Oppermann #define	V_tcp_recvspace	VNET(tcp_recvspace)
197ddd0c4a9SSergey Kandaurov SYSCTL_VNET_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_RW,
198873789cbSAndre Oppermann     &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size");
199873789cbSAndre Oppermann 
20082cea7e6SBjoern A. Zeeb VNET_DEFINE(int, tcp_do_autorcvbuf) = 1;
20182cea7e6SBjoern A. Zeeb #define	V_tcp_do_autorcvbuf	VNET(tcp_do_autorcvbuf)
202eddfbb76SRobert Watson SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW,
203eddfbb76SRobert Watson     &VNET_NAME(tcp_do_autorcvbuf), 0,
2048b615593SMarko Zec     "Enable automatic receive buffer sizing");
2056741ecf5SAndre Oppermann 
20682cea7e6SBjoern A. Zeeb VNET_DEFINE(int, tcp_autorcvbuf_inc) = 16*1024;
20782cea7e6SBjoern A. Zeeb #define	V_tcp_autorcvbuf_inc	VNET(tcp_autorcvbuf_inc)
208eddfbb76SRobert Watson SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW,
209eddfbb76SRobert Watson     &VNET_NAME(tcp_autorcvbuf_inc), 0,
2106489fe65SAndre Oppermann     "Incrementor step size of automatic receive buffer");
2116741ecf5SAndre Oppermann 
212b233773bSBjoern A. Zeeb VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024;
21382cea7e6SBjoern A. Zeeb #define	V_tcp_autorcvbuf_max	VNET(tcp_autorcvbuf_max)
214eddfbb76SRobert Watson SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW,
215eddfbb76SRobert Watson     &VNET_NAME(tcp_autorcvbuf_max), 0,
2168b615593SMarko Zec     "Max size of automatic receive buffer");
2176741ecf5SAndre Oppermann 
218eddfbb76SRobert Watson VNET_DEFINE(struct inpcbhead, tcb);
21944e33a07SMarko Zec #define	tcb6	tcb  /* for KAME src sync over BSD*'s */
22082cea7e6SBjoern A. Zeeb VNET_DEFINE(struct inpcbinfo, tcbinfo);
221df8bae1dSRodney W. Grimes 
2225a53ca16SPaul Saab static void	 tcp_dooptions(struct tcpopt *, u_char *, int, int);
223679d9708SAndre Oppermann static void	 tcp_do_segment(struct mbuf *, struct tcphdr *,
224252ca428SRobert Watson 		     struct socket *, struct tcpcb *, int, int, uint8_t,
225252ca428SRobert Watson 		     int);
226302ce8d6SAndre Oppermann static void	 tcp_dropwithreset(struct mbuf *, struct tcphdr *,
227302ce8d6SAndre Oppermann 		     struct tcpcb *, int, int);
2284d77a549SAlfred Perlstein static void	 tcp_pulloutofband(struct socket *,
2294d77a549SAlfred Perlstein 		     struct tcphdr *, struct mbuf *, int);
2304d77a549SAlfred Perlstein static void	 tcp_xmit_timer(struct tcpcb *, int);
231c068736aSJeffrey Hsu static void	 tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *);
232dbc42409SLawrence Stewart static void inline	cc_ack_received(struct tcpcb *tp, struct tcphdr *th,
233dbc42409SLawrence Stewart 			    uint16_t type);
234dbc42409SLawrence Stewart static void inline	cc_conn_init(struct tcpcb *tp);
235dbc42409SLawrence Stewart static void inline	cc_post_recovery(struct tcpcb *tp, struct tcphdr *th);
23639bc9de5SLawrence Stewart static void inline	hhook_run_tcp_est_in(struct tcpcb *tp,
23739bc9de5SLawrence Stewart 			    struct tcphdr *th, struct tcpopt *to);
238f2512ba1SRui Paulo 
239315e3e38SRobert Watson /*
2405da0521fSAndrey V. Elsukov  * TCP statistics are stored in an "array" of counter(9)s.
2415923c293SGleb Smirnoff  */
2425da0521fSAndrey V. Elsukov VNET_PCPUSTAT_DEFINE(struct tcpstat, tcpstat);
2435da0521fSAndrey V. Elsukov VNET_PCPUSTAT_SYSINIT(tcpstat);
2445da0521fSAndrey V. Elsukov SYSCTL_VNET_PCPUSTAT(_net_inet_tcp, TCPCTL_STATS, stats, struct tcpstat,
2455da0521fSAndrey V. Elsukov     tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)");
2465923c293SGleb Smirnoff 
2475923c293SGleb Smirnoff #ifdef VIMAGE
2485da0521fSAndrey V. Elsukov VNET_PCPUSTAT_SYSUNINIT(tcpstat);
2495923c293SGleb Smirnoff #endif /* VIMAGE */
2505923c293SGleb Smirnoff /*
251315e3e38SRobert Watson  * Kernel module interface for updating tcpstat.  The argument is an index
2525923c293SGleb Smirnoff  * into tcpstat treated as an array.
253315e3e38SRobert Watson  */
254315e3e38SRobert Watson void
255315e3e38SRobert Watson kmod_tcpstat_inc(int statnum)
256315e3e38SRobert Watson {
257315e3e38SRobert Watson 
2585da0521fSAndrey V. Elsukov 	counter_u64_add(VNET(tcpstat)[statnum], 1);
259315e3e38SRobert Watson }
260315e3e38SRobert Watson 
261dbc42409SLawrence Stewart /*
26239bc9de5SLawrence Stewart  * Wrapper for the TCP established input helper hook.
26339bc9de5SLawrence Stewart  */
26439bc9de5SLawrence Stewart static void inline
26539bc9de5SLawrence Stewart hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to)
26639bc9de5SLawrence Stewart {
26739bc9de5SLawrence Stewart 	struct tcp_hhook_data hhook_data;
26839bc9de5SLawrence Stewart 
26939bc9de5SLawrence Stewart 	if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) {
27039bc9de5SLawrence Stewart 		hhook_data.tp = tp;
27139bc9de5SLawrence Stewart 		hhook_data.th = th;
27239bc9de5SLawrence Stewart 		hhook_data.to = to;
27339bc9de5SLawrence Stewart 
27439bc9de5SLawrence Stewart 		hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data,
27539bc9de5SLawrence Stewart 		    tp->osd);
27639bc9de5SLawrence Stewart 	}
27739bc9de5SLawrence Stewart }
27839bc9de5SLawrence Stewart 
27939bc9de5SLawrence Stewart /*
280dbc42409SLawrence Stewart  * CC wrapper hook functions
281dbc42409SLawrence Stewart  */
282f2512ba1SRui Paulo static void inline
283dbc42409SLawrence Stewart cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t type)
284f2512ba1SRui Paulo {
285dbc42409SLawrence Stewart 	INP_WLOCK_ASSERT(tp->t_inpcb);
286f2512ba1SRui Paulo 
287dbc42409SLawrence Stewart 	tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th);
2885b648e79SLawrence Stewart 	if (tp->snd_cwnd <= tp->snd_wnd)
289dbc42409SLawrence Stewart 		tp->ccv->flags |= CCF_CWND_LIMITED;
290dbc42409SLawrence Stewart 	else
291dbc42409SLawrence Stewart 		tp->ccv->flags &= ~CCF_CWND_LIMITED;
292dbc42409SLawrence Stewart 
293dbc42409SLawrence Stewart 	if (type == CC_ACK) {
294dbc42409SLawrence Stewart 		if (tp->snd_cwnd > tp->snd_ssthresh) {
295dbc42409SLawrence Stewart 			tp->t_bytes_acked += min(tp->ccv->bytes_this_ack,
296dbc42409SLawrence Stewart 			     V_tcp_abc_l_var * tp->t_maxseg);
297dbc42409SLawrence Stewart 			if (tp->t_bytes_acked >= tp->snd_cwnd) {
298dbc42409SLawrence Stewart 				tp->t_bytes_acked -= tp->snd_cwnd;
299dbc42409SLawrence Stewart 				tp->ccv->flags |= CCF_ABC_SENTAWND;
300dbc42409SLawrence Stewart 			}
301dbc42409SLawrence Stewart 		} else {
302dbc42409SLawrence Stewart 				tp->ccv->flags &= ~CCF_ABC_SENTAWND;
303dbc42409SLawrence Stewart 				tp->t_bytes_acked = 0;
304dbc42409SLawrence Stewart 		}
305dbc42409SLawrence Stewart 	}
306dbc42409SLawrence Stewart 
307dbc42409SLawrence Stewart 	if (CC_ALGO(tp)->ack_received != NULL) {
308dbc42409SLawrence Stewart 		/* XXXLAS: Find a way to live without this */
309dbc42409SLawrence Stewart 		tp->ccv->curack = th->th_ack;
310dbc42409SLawrence Stewart 		CC_ALGO(tp)->ack_received(tp->ccv, type);
311dbc42409SLawrence Stewart 	}
312dbc42409SLawrence Stewart }
313dbc42409SLawrence Stewart 
314dbc42409SLawrence Stewart static void inline
315dbc42409SLawrence Stewart cc_conn_init(struct tcpcb *tp)
316dbc42409SLawrence Stewart {
317dbc42409SLawrence Stewart 	struct hc_metrics_lite metrics;
318dbc42409SLawrence Stewart 	struct inpcb *inp = tp->t_inpcb;
319dbc42409SLawrence Stewart 	int rtt;
320dbc42409SLawrence Stewart 
321dbc42409SLawrence Stewart 	INP_WLOCK_ASSERT(tp->t_inpcb);
322dbc42409SLawrence Stewart 
323dbc42409SLawrence Stewart 	tcp_hc_get(&inp->inp_inc, &metrics);
324dbc42409SLawrence Stewart 
325dbc42409SLawrence Stewart 	if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) {
326dbc42409SLawrence Stewart 		tp->t_srtt = rtt;
327dbc42409SLawrence Stewart 		tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
328dbc42409SLawrence Stewart 		TCPSTAT_INC(tcps_usedrtt);
329dbc42409SLawrence Stewart 		if (metrics.rmx_rttvar) {
330dbc42409SLawrence Stewart 			tp->t_rttvar = metrics.rmx_rttvar;
331dbc42409SLawrence Stewart 			TCPSTAT_INC(tcps_usedrttvar);
332dbc42409SLawrence Stewart 		} else {
333dbc42409SLawrence Stewart 			/* default variation is +- 1 rtt */
334dbc42409SLawrence Stewart 			tp->t_rttvar =
335dbc42409SLawrence Stewart 			    tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
336dbc42409SLawrence Stewart 		}
337dbc42409SLawrence Stewart 		TCPT_RANGESET(tp->t_rxtcur,
338dbc42409SLawrence Stewart 		    ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
339dbc42409SLawrence Stewart 		    tp->t_rttmin, TCPTV_REXMTMAX);
340dbc42409SLawrence Stewart 	}
341dbc42409SLawrence Stewart 	if (metrics.rmx_ssthresh) {
342dbc42409SLawrence Stewart 		/*
343dbc42409SLawrence Stewart 		 * There's some sort of gateway or interface
344dbc42409SLawrence Stewart 		 * buffer limit on the path.  Use this to set
345dbc42409SLawrence Stewart 		 * the slow start threshhold, but set the
346dbc42409SLawrence Stewart 		 * threshold to no less than 2*mss.
347dbc42409SLawrence Stewart 		 */
348dbc42409SLawrence Stewart 		tp->snd_ssthresh = max(2 * tp->t_maxseg, metrics.rmx_ssthresh);
349dbc42409SLawrence Stewart 		TCPSTAT_INC(tcps_usedssthresh);
350dbc42409SLawrence Stewart 	}
351dbc42409SLawrence Stewart 
352dbc42409SLawrence Stewart 	/*
3539ec4a4ccSAndre Oppermann 	 * Set the initial slow-start flight size.
354dbc42409SLawrence Stewart 	 *
355cf8f04f4SAndre Oppermann 	 * RFC5681 Section 3.1 specifies the default conservative values.
356cf8f04f4SAndre Oppermann 	 * RFC3390 specifies slightly more aggressive values.
357b8b4cfcdSSergey Kandaurov 	 * RFC6928 increases it to ten segments.
358cf8f04f4SAndre Oppermann 	 *
359cf8f04f4SAndre Oppermann 	 * If a SYN or SYN/ACK was lost and retransmitted, we have to
360cf8f04f4SAndre Oppermann 	 * reduce the initial CWND to one segment as congestion is likely
361cf8f04f4SAndre Oppermann 	 * requiring us to be cautious.
362dbc42409SLawrence Stewart 	 */
363cf8f04f4SAndre Oppermann 	if (tp->snd_cwnd == 1)
364cf8f04f4SAndre Oppermann 		tp->snd_cwnd = tp->t_maxseg;		/* SYN(-ACK) lost */
36509440655SAndre Oppermann 	else if (V_tcp_do_initcwnd10)
36609440655SAndre Oppermann 		tp->snd_cwnd = min(10 * tp->t_maxseg,
36709440655SAndre Oppermann 		    max(2 * tp->t_maxseg, 14600));
368cf8f04f4SAndre Oppermann 	else if (V_tcp_do_rfc3390)
369dbc42409SLawrence Stewart 		tp->snd_cwnd = min(4 * tp->t_maxseg,
370dbc42409SLawrence Stewart 		    max(2 * tp->t_maxseg, 4380));
37122efabd4SAndre Oppermann 	else {
37222efabd4SAndre Oppermann 		/* Per RFC5681 Section 3.1 */
37322efabd4SAndre Oppermann 		if (tp->t_maxseg > 2190)
37422efabd4SAndre Oppermann 			tp->snd_cwnd = 2 * tp->t_maxseg;
37522efabd4SAndre Oppermann 		else if (tp->t_maxseg > 1095)
37622efabd4SAndre Oppermann 			tp->snd_cwnd = 3 * tp->t_maxseg;
377dbc42409SLawrence Stewart 		else
37822efabd4SAndre Oppermann 			tp->snd_cwnd = 4 * tp->t_maxseg;
37922efabd4SAndre Oppermann 	}
380dbc42409SLawrence Stewart 
381dbc42409SLawrence Stewart 	if (CC_ALGO(tp)->conn_init != NULL)
382dbc42409SLawrence Stewart 		CC_ALGO(tp)->conn_init(tp->ccv);
383dbc42409SLawrence Stewart }
384dbc42409SLawrence Stewart 
385dbc42409SLawrence Stewart void inline
386dbc42409SLawrence Stewart cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type)
387dbc42409SLawrence Stewart {
388dbc42409SLawrence Stewart 	INP_WLOCK_ASSERT(tp->t_inpcb);
389dbc42409SLawrence Stewart 
390dbc42409SLawrence Stewart 	switch(type) {
391dbc42409SLawrence Stewart 	case CC_NDUPACK:
392dbc42409SLawrence Stewart 		if (!IN_FASTRECOVERY(tp->t_flags)) {
393f2512ba1SRui Paulo 			tp->snd_recover = tp->snd_max;
394f2512ba1SRui Paulo 			if (tp->t_flags & TF_ECN_PERMIT)
395f2512ba1SRui Paulo 				tp->t_flags |= TF_ECN_SND_CWR;
396f2512ba1SRui Paulo 		}
397dbc42409SLawrence Stewart 		break;
398dbc42409SLawrence Stewart 	case CC_ECN:
399dbc42409SLawrence Stewart 		if (!IN_CONGRECOVERY(tp->t_flags)) {
400dbc42409SLawrence Stewart 			TCPSTAT_INC(tcps_ecn_rcwnd);
401dbc42409SLawrence Stewart 			tp->snd_recover = tp->snd_max;
402dbc42409SLawrence Stewart 			if (tp->t_flags & TF_ECN_PERMIT)
403dbc42409SLawrence Stewart 				tp->t_flags |= TF_ECN_SND_CWR;
404dbc42409SLawrence Stewart 		}
405dbc42409SLawrence Stewart 		break;
406dbc42409SLawrence Stewart 	case CC_RTO:
407dbc42409SLawrence Stewart 		tp->t_dupacks = 0;
408dbc42409SLawrence Stewart 		tp->t_bytes_acked = 0;
409dbc42409SLawrence Stewart 		EXIT_RECOVERY(tp->t_flags);
4106157935fSLawrence Stewart 		tp->snd_ssthresh = max(2, min(tp->snd_wnd, tp->snd_cwnd) / 2 /
4116157935fSLawrence Stewart 		    tp->t_maxseg) * tp->t_maxseg;
412dbc42409SLawrence Stewart 		tp->snd_cwnd = tp->t_maxseg;
413dbc42409SLawrence Stewart 		break;
414dbc42409SLawrence Stewart 	case CC_RTO_ERR:
415dbc42409SLawrence Stewart 		TCPSTAT_INC(tcps_sndrexmitbad);
416dbc42409SLawrence Stewart 		/* RTO was unnecessary, so reset everything. */
417dbc42409SLawrence Stewart 		tp->snd_cwnd = tp->snd_cwnd_prev;
418dbc42409SLawrence Stewart 		tp->snd_ssthresh = tp->snd_ssthresh_prev;
419dbc42409SLawrence Stewart 		tp->snd_recover = tp->snd_recover_prev;
420dbc42409SLawrence Stewart 		if (tp->t_flags & TF_WASFRECOVERY)
421dbc42409SLawrence Stewart 			ENTER_FASTRECOVERY(tp->t_flags);
422dbc42409SLawrence Stewart 		if (tp->t_flags & TF_WASCRECOVERY)
423dbc42409SLawrence Stewart 			ENTER_CONGRECOVERY(tp->t_flags);
424dbc42409SLawrence Stewart 		tp->snd_nxt = tp->snd_max;
425672dc4aeSJohn Baldwin 		tp->t_flags &= ~TF_PREVVALID;
426dbc42409SLawrence Stewart 		tp->t_badrxtwin = 0;
427dbc42409SLawrence Stewart 		break;
428dbc42409SLawrence Stewart 	}
429dbc42409SLawrence Stewart 
430dbc42409SLawrence Stewart 	if (CC_ALGO(tp)->cong_signal != NULL) {
431dbc42409SLawrence Stewart 		if (th != NULL)
432dbc42409SLawrence Stewart 			tp->ccv->curack = th->th_ack;
433dbc42409SLawrence Stewart 		CC_ALGO(tp)->cong_signal(tp->ccv, type);
434dbc42409SLawrence Stewart 	}
435dbc42409SLawrence Stewart }
436dbc42409SLawrence Stewart 
437dbc42409SLawrence Stewart static void inline
438dbc42409SLawrence Stewart cc_post_recovery(struct tcpcb *tp, struct tcphdr *th)
439dbc42409SLawrence Stewart {
440dbc42409SLawrence Stewart 	INP_WLOCK_ASSERT(tp->t_inpcb);
441dbc42409SLawrence Stewart 
442dbc42409SLawrence Stewart 	/* XXXLAS: KASSERT that we're in recovery? */
443dbc42409SLawrence Stewart 
444dbc42409SLawrence Stewart 	if (CC_ALGO(tp)->post_recovery != NULL) {
445dbc42409SLawrence Stewart 		tp->ccv->curack = th->th_ack;
446dbc42409SLawrence Stewart 		CC_ALGO(tp)->post_recovery(tp->ccv);
447dbc42409SLawrence Stewart 	}
448dbc42409SLawrence Stewart 	/* XXXLAS: EXIT_RECOVERY ? */
449dbc42409SLawrence Stewart 	tp->t_bytes_acked = 0;
450dbc42409SLawrence Stewart }
4510312fbe9SPoul-Henning Kamp 
4522903309aSAttilio Rao #ifdef TCP_SIGNATURE
4532903309aSAttilio Rao static inline int
4542903309aSAttilio Rao tcp_signature_verify_input(struct mbuf *m, int off0, int tlen, int optlen,
4552903309aSAttilio Rao     struct tcpopt *to, struct tcphdr *th, u_int tcpbflag)
4562903309aSAttilio Rao {
4572903309aSAttilio Rao 	int ret;
4582903309aSAttilio Rao 
4592903309aSAttilio Rao 	tcp_fields_to_net(th);
4602903309aSAttilio Rao 	ret = tcp_signature_verify(m, off0, tlen, optlen, to, th, tcpbflag);
4612903309aSAttilio Rao 	tcp_fields_to_host(th);
4622903309aSAttilio Rao 	return (ret);
4632903309aSAttilio Rao }
4642903309aSAttilio Rao #endif
4652903309aSAttilio Rao 
466fb59c426SYoshinobu Inoue /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
467fb59c426SYoshinobu Inoue #ifdef INET6
468fb59c426SYoshinobu Inoue #define ND6_HINT(tp) \
469fb59c426SYoshinobu Inoue do { \
470fb59c426SYoshinobu Inoue 	if ((tp) && (tp)->t_inpcb && \
47197d8d152SAndre Oppermann 	    ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \
47297d8d152SAndre Oppermann 		nd6_nud_hint(NULL, NULL, 0); \
473fb59c426SYoshinobu Inoue } while (0)
474fb59c426SYoshinobu Inoue #else
475fb59c426SYoshinobu Inoue #define ND6_HINT(tp)
476fb59c426SYoshinobu Inoue #endif
477df8bae1dSRodney W. Grimes 
478df8bae1dSRodney W. Grimes /*
479262c1c1aSMatthew Dillon  * Indicate whether this ack should be delayed.  We can delay the ack if
48085536381SHiren Panchasara  * following conditions are met:
48185536381SHiren Panchasara  *	- There is no delayed ack timer in progress.
48285536381SHiren Panchasara  *	- Our last ack wasn't a 0-sized window. We never want to delay
48385536381SHiren Panchasara  *	  the ack that opens up a 0-sized window.
48485536381SHiren Panchasara  *	- LRO wasn't used for this segment. We make sure by checking that the
48585536381SHiren Panchasara  *	  segment size is not larger than the MSS.
48685536381SHiren Panchasara  *	- Delayed acks are enabled or this is a half-synchronized T/TCP
48785536381SHiren Panchasara  *	  connection.
488d8c85a26SJonathan Lemon  */
489c1e5a6e5SAndre Oppermann #define DELAY_ACK(tp, tlen)						\
490b8152ba7SAndre Oppermann 	((!tcp_timer_active(tp, TT_DELACK) &&				\
491a14c749fSJonathan Lemon 	    (tp->t_flags & TF_RXWIN0SENT) == 0) &&			\
492c1e5a6e5SAndre Oppermann 	    (tlen <= tp->t_maxopd) &&					\
493603724d3SBjoern A. Zeeb 	    (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN)))
494d8c85a26SJonathan Lemon 
495df8bae1dSRodney W. Grimes /*
4968d573cc1SAndre Oppermann  * TCP input handling is split into multiple parts:
4978d573cc1SAndre Oppermann  *   tcp6_input is a thin wrapper around tcp_input for the extended
4988d573cc1SAndre Oppermann  *	ip6_protox[] call format in ip6_input
4998d573cc1SAndre Oppermann  *   tcp_input handles primary segment validation, inpcb lookup and
5008d573cc1SAndre Oppermann  *	SYN processing on listen sockets
5018d573cc1SAndre Oppermann  *   tcp_do_segment processes the ACK and text of the segment for
5028d573cc1SAndre Oppermann  *	establishing, established and closing connections
503df8bae1dSRodney W. Grimes  */
504fb59c426SYoshinobu Inoue #ifdef INET6
505fb59c426SYoshinobu Inoue int
506ad3f9ab3SAndre Oppermann tcp6_input(struct mbuf **mp, int *offp, int proto)
507fb59c426SYoshinobu Inoue {
508ad3f9ab3SAndre Oppermann 	struct mbuf *m = *mp;
50933841545SHajimu UMEMOTO 	struct in6_ifaddr *ia6;
510fb59c426SYoshinobu Inoue 
511fb59c426SYoshinobu Inoue 	IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
512fb59c426SYoshinobu Inoue 
513fb59c426SYoshinobu Inoue 	/*
514fb59c426SYoshinobu Inoue 	 * draft-itojun-ipv6-tcp-to-anycast
515fb59c426SYoshinobu Inoue 	 * better place to put this in?
516fb59c426SYoshinobu Inoue 	 */
51733841545SHajimu UMEMOTO 	ia6 = ip6_getdstifaddr(m);
51833841545SHajimu UMEMOTO 	if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
519fb59c426SYoshinobu Inoue 		struct ip6_hdr *ip6;
520fb59c426SYoshinobu Inoue 
5218c0fec80SRobert Watson 		ifa_free(&ia6->ia_ifa);
522fb59c426SYoshinobu Inoue 		ip6 = mtod(m, struct ip6_hdr *);
523fb59c426SYoshinobu Inoue 		icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
524fb59c426SYoshinobu Inoue 			    (caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
5258f5a8818SKevin Lo 		return (IPPROTO_DONE);
526fb59c426SYoshinobu Inoue 	}
52777d396fdSMaksim Yevmenkin 	if (ia6)
52877d396fdSMaksim Yevmenkin 		ifa_free(&ia6->ia_ifa);
529fb59c426SYoshinobu Inoue 
5308f5a8818SKevin Lo 	return (tcp_input(mp, offp, proto));
531fb59c426SYoshinobu Inoue }
532b287c6c7SBjoern A. Zeeb #endif /* INET6 */
533fb59c426SYoshinobu Inoue 
5348f5a8818SKevin Lo int
5358f5a8818SKevin Lo tcp_input(struct mbuf **mp, int *offp, int proto)
536df8bae1dSRodney W. Grimes {
5378f5a8818SKevin Lo 	struct mbuf *m = *mp;
538b287c6c7SBjoern A. Zeeb 	struct tcphdr *th = NULL;
539ad3f9ab3SAndre Oppermann 	struct ip *ip = NULL;
540ad3f9ab3SAndre Oppermann 	struct inpcb *inp = NULL;
541302ce8d6SAndre Oppermann 	struct tcpcb *tp = NULL;
542302ce8d6SAndre Oppermann 	struct socket *so = NULL;
543e79adb8eSGarrett Wollman 	u_char *optp = NULL;
5448f5a8818SKevin Lo 	int off0;
54526f9a767SRodney W. Grimes 	int optlen = 0;
546b287c6c7SBjoern A. Zeeb #ifdef INET
547b287c6c7SBjoern A. Zeeb 	int len;
548b287c6c7SBjoern A. Zeeb #endif
549b287c6c7SBjoern A. Zeeb 	int tlen = 0, off;
550fb59c426SYoshinobu Inoue 	int drop_hdrlen;
551ad3f9ab3SAndre Oppermann 	int thflags;
552302ce8d6SAndre Oppermann 	int rstreason = 0;	/* For badport_bandlim accounting purposes */
5532903309aSAttilio Rao #ifdef TCP_SIGNATURE
5542903309aSAttilio Rao 	uint8_t sig_checked = 0;
5552903309aSAttilio Rao #endif
556b287c6c7SBjoern A. Zeeb 	uint8_t iptos = 0;
557c1de64a4SAndrey V. Elsukov 	struct m_tag *fwd_tag = NULL;
558c068736aSJeffrey Hsu #ifdef INET6
559302ce8d6SAndre Oppermann 	struct ip6_hdr *ip6 = NULL;
560c068736aSJeffrey Hsu 	int isipv6;
561c068736aSJeffrey Hsu #else
562a160e630SAndre Oppermann 	const void *ip6 = NULL;
563b287c6c7SBjoern A. Zeeb #endif /* INET6 */
564302ce8d6SAndre Oppermann 	struct tcpopt to;		/* options in this segment */
565a160e630SAndre Oppermann 	char *s = NULL;			/* address and port logging */
566252ca428SRobert Watson 	int ti_locked;
567252ca428SRobert Watson #define	TI_UNLOCKED	1
568fa046d87SRobert Watson #define	TI_WLOCKED	2
569f76fcf6dSJeffrey Hsu 
570610ee2f9SDavid Greenman #ifdef TCPDEBUG
571c068736aSJeffrey Hsu 	/*
572c068736aSJeffrey Hsu 	 * The size of tcp_saveipgen must be the size of the max ip header,
573c068736aSJeffrey Hsu 	 * now IPv6.
574c068736aSJeffrey Hsu 	 */
57514739780SMaxim Konovalov 	u_char tcp_saveipgen[IP6_HDR_LEN];
576410bb1bfSLuigi Rizzo 	struct tcphdr tcp_savetcp;
577610ee2f9SDavid Greenman 	short ostate = 0;
578610ee2f9SDavid Greenman #endif
579c068736aSJeffrey Hsu 
580fb59c426SYoshinobu Inoue #ifdef INET6
581fb59c426SYoshinobu Inoue 	isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
582fb59c426SYoshinobu Inoue #endif
583a0292f23SGarrett Wollman 
5848f5a8818SKevin Lo 	off0 = *offp;
5858f5a8818SKevin Lo 	m = *mp;
5868f5a8818SKevin Lo 	*mp = NULL;
587302ce8d6SAndre Oppermann 	to.to_flags = 0;
58878b50714SRobert Watson 	TCPSTAT_INC(tcps_rcvtotal);
589fb59c426SYoshinobu Inoue 
59004d3a452SHajimu UMEMOTO #ifdef INET6
591b287c6c7SBjoern A. Zeeb 	if (isipv6) {
5928d573cc1SAndre Oppermann 		/* IP6_EXTHDR_CHECK() is already done at tcp6_input(). */
59345747ba5SBjoern A. Zeeb 
59445747ba5SBjoern A. Zeeb 		if (m->m_len < (sizeof(*ip6) + sizeof(*th))) {
59545747ba5SBjoern A. Zeeb 			m = m_pullup(m, sizeof(*ip6) + sizeof(*th));
59645747ba5SBjoern A. Zeeb 			if (m == NULL) {
59745747ba5SBjoern A. Zeeb 				TCPSTAT_INC(tcps_rcvshort);
5988f5a8818SKevin Lo 				return (IPPROTO_DONE);
59945747ba5SBjoern A. Zeeb 			}
60045747ba5SBjoern A. Zeeb 		}
60145747ba5SBjoern A. Zeeb 
602fb59c426SYoshinobu Inoue 		ip6 = mtod(m, struct ip6_hdr *);
60345747ba5SBjoern A. Zeeb 		th = (struct tcphdr *)((caddr_t)ip6 + off0);
604fb59c426SYoshinobu Inoue 		tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
605356ab07eSBjoern A. Zeeb 		if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) {
60645747ba5SBjoern A. Zeeb 			if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
60745747ba5SBjoern A. Zeeb 				th->th_sum = m->m_pkthdr.csum_data;
60845747ba5SBjoern A. Zeeb 			else
60945747ba5SBjoern A. Zeeb 				th->th_sum = in6_cksum_pseudo(ip6, tlen,
61045747ba5SBjoern A. Zeeb 				    IPPROTO_TCP, m->m_pkthdr.csum_data);
61145747ba5SBjoern A. Zeeb 			th->th_sum ^= 0xffff;
61245747ba5SBjoern A. Zeeb 		} else
61345747ba5SBjoern A. Zeeb 			th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen);
61445747ba5SBjoern A. Zeeb 		if (th->th_sum) {
61578b50714SRobert Watson 			TCPSTAT_INC(tcps_rcvbadsum);
616fb59c426SYoshinobu Inoue 			goto drop;
617fb59c426SYoshinobu Inoue 		}
61833841545SHajimu UMEMOTO 
61933841545SHajimu UMEMOTO 		/*
62033841545SHajimu UMEMOTO 		 * Be proactive about unspecified IPv6 address in source.
62133841545SHajimu UMEMOTO 		 * As we use all-zero to indicate unbounded/unconnected pcb,
62233841545SHajimu UMEMOTO 		 * unspecified IPv6 address can be used to confuse us.
62333841545SHajimu UMEMOTO 		 *
62433841545SHajimu UMEMOTO 		 * Note that packets with unspecified IPv6 destination is
62533841545SHajimu UMEMOTO 		 * already dropped in ip6_input.
62633841545SHajimu UMEMOTO 		 */
62733841545SHajimu UMEMOTO 		if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
62833841545SHajimu UMEMOTO 			/* XXX stat */
62933841545SHajimu UMEMOTO 			goto drop;
63033841545SHajimu UMEMOTO 		}
631b287c6c7SBjoern A. Zeeb 	}
63204d3a452SHajimu UMEMOTO #endif
633b287c6c7SBjoern A. Zeeb #if defined(INET) && defined(INET6)
634b287c6c7SBjoern A. Zeeb 	else
635b287c6c7SBjoern A. Zeeb #endif
636b287c6c7SBjoern A. Zeeb #ifdef INET
637b287c6c7SBjoern A. Zeeb 	{
638df8bae1dSRodney W. Grimes 		/*
639df8bae1dSRodney W. Grimes 		 * Get IP and TCP header together in first mbuf.
640df8bae1dSRodney W. Grimes 		 * Note: IP leaves IP header in first mbuf.
641df8bae1dSRodney W. Grimes 		 */
642fb59c426SYoshinobu Inoue 		if (off0 > sizeof (struct ip)) {
643105bd211SGleb Smirnoff 			ip_stripoptions(m);
644fb59c426SYoshinobu Inoue 			off0 = sizeof(struct ip);
645fb59c426SYoshinobu Inoue 		}
646df8bae1dSRodney W. Grimes 		if (m->m_len < sizeof (struct tcpiphdr)) {
6474dfdffe9SAndre Oppermann 			if ((m = m_pullup(m, sizeof (struct tcpiphdr)))
6484dfdffe9SAndre Oppermann 			    == NULL) {
64978b50714SRobert Watson 				TCPSTAT_INC(tcps_rcvshort);
6508f5a8818SKevin Lo 				return (IPPROTO_DONE);
651df8bae1dSRodney W. Grimes 			}
652df8bae1dSRodney W. Grimes 		}
653fb59c426SYoshinobu Inoue 		ip = mtod(m, struct ip *);
654db4f9cc7SJonathan Lemon 		th = (struct tcphdr *)((caddr_t)ip + off0);
6558ad458a4SGleb Smirnoff 		tlen = ntohs(ip->ip_len) - off0;
656df8bae1dSRodney W. Grimes 
657db4f9cc7SJonathan Lemon 		if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
658db4f9cc7SJonathan Lemon 			if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
659db4f9cc7SJonathan Lemon 				th->th_sum = m->m_pkthdr.csum_data;
660db4f9cc7SJonathan Lemon 			else
661db4f9cc7SJonathan Lemon 				th->th_sum = in_pseudo(ip->ip_src.s_addr,
662c068736aSJeffrey Hsu 				    ip->ip_dst.s_addr,
6638f134647SGleb Smirnoff 				    htonl(m->m_pkthdr.csum_data + tlen +
664c068736aSJeffrey Hsu 				    IPPROTO_TCP));
665db4f9cc7SJonathan Lemon 			th->th_sum ^= 0xffff;
666db4f9cc7SJonathan Lemon 		} else {
6678f134647SGleb Smirnoff 			struct ipovly *ipov = (struct ipovly *)ip;
6688f134647SGleb Smirnoff 
669df8bae1dSRodney W. Grimes 			/*
670df8bae1dSRodney W. Grimes 			 * Checksum extended TCP header and data.
671df8bae1dSRodney W. Grimes 			 */
6728f134647SGleb Smirnoff 			len = off0 + tlen;
673fb59c426SYoshinobu Inoue 			bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
6748f134647SGleb Smirnoff 			ipov->ih_len = htons(tlen);
675fb59c426SYoshinobu Inoue 			th->th_sum = in_cksum(m, len);
67657f60867SMark Johnston 			/* Reset length for SDT probes. */
67757f60867SMark Johnston 			ip->ip_len = htons(tlen + off0);
678db4f9cc7SJonathan Lemon 		}
67957f60867SMark Johnston 
680fb59c426SYoshinobu Inoue 		if (th->th_sum) {
68178b50714SRobert Watson 			TCPSTAT_INC(tcps_rcvbadsum);
682df8bae1dSRodney W. Grimes 			goto drop;
683df8bae1dSRodney W. Grimes 		}
684fb59c426SYoshinobu Inoue 		/* Re-initialization for later version check */
685fb59c426SYoshinobu Inoue 		ip->ip_v = IPVERSION;
686fb59c426SYoshinobu Inoue 	}
687b287c6c7SBjoern A. Zeeb #endif /* INET */
688df8bae1dSRodney W. Grimes 
689f2512ba1SRui Paulo #ifdef INET6
690f2512ba1SRui Paulo 	if (isipv6)
691f2512ba1SRui Paulo 		iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff;
692b287c6c7SBjoern A. Zeeb #endif
693b287c6c7SBjoern A. Zeeb #if defined(INET) && defined(INET6)
694f2512ba1SRui Paulo 	else
695f2512ba1SRui Paulo #endif
696b287c6c7SBjoern A. Zeeb #ifdef INET
697f2512ba1SRui Paulo 		iptos = ip->ip_tos;
698b287c6c7SBjoern A. Zeeb #endif
699f2512ba1SRui Paulo 
700df8bae1dSRodney W. Grimes 	/*
701df8bae1dSRodney W. Grimes 	 * Check that TCP offset makes sense,
702df8bae1dSRodney W. Grimes 	 * pull out TCP options and adjust length.		XXX
703df8bae1dSRodney W. Grimes 	 */
704fb59c426SYoshinobu Inoue 	off = th->th_off << 2;
705df8bae1dSRodney W. Grimes 	if (off < sizeof (struct tcphdr) || off > tlen) {
70678b50714SRobert Watson 		TCPSTAT_INC(tcps_rcvbadoff);
707df8bae1dSRodney W. Grimes 		goto drop;
708df8bae1dSRodney W. Grimes 	}
709fb59c426SYoshinobu Inoue 	tlen -= off;	/* tlen is used instead of ti->ti_len */
710df8bae1dSRodney W. Grimes 	if (off > sizeof (struct tcphdr)) {
71104d3a452SHajimu UMEMOTO #ifdef INET6
712b287c6c7SBjoern A. Zeeb 		if (isipv6) {
7138f5a8818SKevin Lo 			IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE);
714fb59c426SYoshinobu Inoue 			ip6 = mtod(m, struct ip6_hdr *);
715fb59c426SYoshinobu Inoue 			th = (struct tcphdr *)((caddr_t)ip6 + off0);
716b287c6c7SBjoern A. Zeeb 		}
71704d3a452SHajimu UMEMOTO #endif
718b287c6c7SBjoern A. Zeeb #if defined(INET) && defined(INET6)
719b287c6c7SBjoern A. Zeeb 		else
720b287c6c7SBjoern A. Zeeb #endif
721b287c6c7SBjoern A. Zeeb #ifdef INET
722b287c6c7SBjoern A. Zeeb 		{
723df8bae1dSRodney W. Grimes 			if (m->m_len < sizeof(struct ip) + off) {
724c068736aSJeffrey Hsu 				if ((m = m_pullup(m, sizeof (struct ip) + off))
7254dfdffe9SAndre Oppermann 				    == NULL) {
72678b50714SRobert Watson 					TCPSTAT_INC(tcps_rcvshort);
7278f5a8818SKevin Lo 					return (IPPROTO_DONE);
728df8bae1dSRodney W. Grimes 				}
729fb59c426SYoshinobu Inoue 				ip = mtod(m, struct ip *);
730fb59c426SYoshinobu Inoue 				th = (struct tcphdr *)((caddr_t)ip + off0);
731fb59c426SYoshinobu Inoue 			}
732df8bae1dSRodney W. Grimes 		}
733b287c6c7SBjoern A. Zeeb #endif
734df8bae1dSRodney W. Grimes 		optlen = off - sizeof (struct tcphdr);
735fb59c426SYoshinobu Inoue 		optp = (u_char *)(th + 1);
736df8bae1dSRodney W. Grimes 	}
737fb59c426SYoshinobu Inoue 	thflags = th->th_flags;
738df8bae1dSRodney W. Grimes 
739e46cd3d4SDag-Erling Smørgrav 	/*
740df8bae1dSRodney W. Grimes 	 * Convert TCP protocol specific fields to host format.
741df8bae1dSRodney W. Grimes 	 */
7422903309aSAttilio Rao 	tcp_fields_to_host(th);
743df8bae1dSRodney W. Grimes 
744df8bae1dSRodney W. Grimes 	/*
745794235b7SAndre Oppermann 	 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options.
746755c1f07SAndras Olah 	 */
747fb59c426SYoshinobu Inoue 	drop_hdrlen = off0 + off;
748755c1f07SAndras Olah 
749755c1f07SAndras Olah 	/*
750fa046d87SRobert Watson 	 * Locate pcb for segment; if we're likely to add or remove a
751a7c7f2a7SJohn Baldwin 	 * connection then first acquire pcbinfo lock.  There are three cases
752fa046d87SRobert Watson 	 * where we might discover later we need a write lock despite the
753a7c7f2a7SJohn Baldwin 	 * flags: ACKs moving a connection out of the syncache, ACKs for a
754a7c7f2a7SJohn Baldwin 	 * connection in TIMEWAIT and SYNs not targeting a listening socket.
755df8bae1dSRodney W. Grimes 	 */
756a7c7f2a7SJohn Baldwin 	if ((thflags & (TH_FIN | TH_RST)) != 0) {
757603724d3SBjoern A. Zeeb 		INP_INFO_WLOCK(&V_tcbinfo);
758252ca428SRobert Watson 		ti_locked = TI_WLOCKED;
759fa046d87SRobert Watson 	} else
760fa046d87SRobert Watson 		ti_locked = TI_UNLOCKED;
761252ca428SRobert Watson 
7628d573cc1SAndre Oppermann 	/*
7638d573cc1SAndre Oppermann 	 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain.
7648d573cc1SAndre Oppermann 	 */
765b8056faeSGleb Smirnoff         if (
766b8056faeSGleb Smirnoff #ifdef INET6
767b8056faeSGleb Smirnoff 	    (isipv6 && (m->m_flags & M_IP6_NEXTHOP))
768b8056faeSGleb Smirnoff #ifdef INET
769b8056faeSGleb Smirnoff 	    || (!isipv6 && (m->m_flags & M_IP_NEXTHOP))
770b8056faeSGleb Smirnoff #endif
771b8056faeSGleb Smirnoff #endif
772b8056faeSGleb Smirnoff #if defined(INET) && !defined(INET6)
773b8056faeSGleb Smirnoff 	    (m->m_flags & M_IP_NEXTHOP)
774b8056faeSGleb Smirnoff #endif
775b8056faeSGleb Smirnoff 	    )
7769b932e9eSAndre Oppermann 		fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
7779b932e9eSAndre Oppermann 
778ce7ad664SEd Maste findpcb:
779ce7ad664SEd Maste #ifdef INVARIANTS
780ce7ad664SEd Maste 	if (ti_locked == TI_WLOCKED) {
781ce7ad664SEd Maste 		INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
782ce7ad664SEd Maste 	} else {
783ce7ad664SEd Maste 		INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
784ce7ad664SEd Maste 	}
785ce7ad664SEd Maste #endif
7868a006adbSBjoern A. Zeeb #ifdef INET6
7878a006adbSBjoern A. Zeeb 	if (isipv6 && fwd_tag != NULL) {
7888a006adbSBjoern A. Zeeb 		struct sockaddr_in6 *next_hop6;
7898a006adbSBjoern A. Zeeb 
7908a006adbSBjoern A. Zeeb 		next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1);
7918a006adbSBjoern A. Zeeb 		/*
7928a006adbSBjoern A. Zeeb 		 * Transparently forwarded. Pretend to be the destination.
7938a006adbSBjoern A. Zeeb 		 * Already got one like this?
7948a006adbSBjoern A. Zeeb 		 */
7958a006adbSBjoern A. Zeeb 		inp = in6_pcblookup_mbuf(&V_tcbinfo,
7968a006adbSBjoern A. Zeeb 		    &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport,
7978a006adbSBjoern A. Zeeb 		    INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m);
7988a006adbSBjoern A. Zeeb 		if (!inp) {
7998a006adbSBjoern A. Zeeb 			/*
8008a006adbSBjoern A. Zeeb 			 * It's new.  Try to find the ambushing socket.
8018a006adbSBjoern A. Zeeb 			 * Because we've rewritten the destination address,
8028a006adbSBjoern A. Zeeb 			 * any hardware-generated hash is ignored.
8038a006adbSBjoern A. Zeeb 			 */
8048a006adbSBjoern A. Zeeb 			inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src,
8058a006adbSBjoern A. Zeeb 			    th->th_sport, &next_hop6->sin6_addr,
8068a006adbSBjoern A. Zeeb 			    next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) :
8078a006adbSBjoern A. Zeeb 			    th->th_dport, INPLOOKUP_WILDCARD |
8088a006adbSBjoern A. Zeeb 			    INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif);
8098a006adbSBjoern A. Zeeb 		}
810c1de64a4SAndrey V. Elsukov 	} else if (isipv6) {
8118a006adbSBjoern A. Zeeb 		inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src,
8128a006adbSBjoern A. Zeeb 		    th->th_sport, &ip6->ip6_dst, th->th_dport,
8138a006adbSBjoern A. Zeeb 		    INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB,
8148a006adbSBjoern A. Zeeb 		    m->m_pkthdr.rcvif, m);
8158a006adbSBjoern A. Zeeb 	}
8168a006adbSBjoern A. Zeeb #endif /* INET6 */
8178a006adbSBjoern A. Zeeb #if defined(INET6) && defined(INET)
8188a006adbSBjoern A. Zeeb 	else
8198a006adbSBjoern A. Zeeb #endif
8208a006adbSBjoern A. Zeeb #ifdef INET
8218a006adbSBjoern A. Zeeb 	if (fwd_tag != NULL) {
8229b932e9eSAndre Oppermann 		struct sockaddr_in *next_hop;
8239b932e9eSAndre Oppermann 
8249b932e9eSAndre Oppermann 		next_hop = (struct sockaddr_in *)(fwd_tag+1);
825f9e354dfSJulian Elischer 		/*
8262b25acc1SLuigi Rizzo 		 * Transparently forwarded. Pretend to be the destination.
827f9e354dfSJulian Elischer 		 * already got one like this?
828f9e354dfSJulian Elischer 		 */
829d3c1f003SRobert Watson 		inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport,
830fa046d87SRobert Watson 		    ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB,
831d3c1f003SRobert Watson 		    m->m_pkthdr.rcvif, m);
832fa046d87SRobert Watson 		if (!inp) {
833fa046d87SRobert Watson 			/*
834fa046d87SRobert Watson 			 * It's new.  Try to find the ambushing socket.
835d3c1f003SRobert Watson 			 * Because we've rewritten the destination address,
836d3c1f003SRobert Watson 			 * any hardware-generated hash is ignored.
837fa046d87SRobert Watson 			 */
838fa046d87SRobert Watson 			inp = in_pcblookup(&V_tcbinfo, ip->ip_src,
839fa046d87SRobert Watson 			    th->th_sport, next_hop->sin_addr,
840fa046d87SRobert Watson 			    next_hop->sin_port ? ntohs(next_hop->sin_port) :
841fa046d87SRobert Watson 			    th->th_dport, INPLOOKUP_WILDCARD |
842fa046d87SRobert Watson 			    INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif);
843f9e354dfSJulian Elischer 		}
844b10fbdeaSAndre Oppermann 	} else
845d3c1f003SRobert Watson 		inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src,
846fa046d87SRobert Watson 		    th->th_sport, ip->ip_dst, th->th_dport,
847fa046d87SRobert Watson 		    INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB,
848d3c1f003SRobert Watson 		    m->m_pkthdr.rcvif, m);
8498a006adbSBjoern A. Zeeb #endif /* INET */
850f9e354dfSJulian Elischer 
851df8bae1dSRodney W. Grimes 	/*
852574b6964SAndre Oppermann 	 * If the INPCB does not exist then all data in the incoming
853574b6964SAndre Oppermann 	 * segment is discarded and an appropriate RST is sent back.
8548b07e49aSJulian Elischer 	 * XXX MRT Send RST using which routing table?
855df8bae1dSRodney W. Grimes 	 */
856816a3d83SPoul-Henning Kamp 	if (inp == NULL) {
857574b6964SAndre Oppermann 		/*
858574b6964SAndre Oppermann 		 * Log communication attempts to ports that are not
859574b6964SAndre Oppermann 		 * in use.
860574b6964SAndre Oppermann 		 */
861574b6964SAndre Oppermann 		if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) ||
862574b6964SAndre Oppermann 		    tcp_log_in_vain == 2) {
863b7d747ecSAndre Oppermann 			if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6)))
864df541e5fSAndre Oppermann 				log(LOG_INFO, "%s; %s: Connection attempt "
865df541e5fSAndre Oppermann 				    "to closed port\n", s, __func__);
8662e4e1b4cSGeoff Rehmet 		}
867574b6964SAndre Oppermann 		/*
868574b6964SAndre Oppermann 		 * When blackholing do not respond with a RST but
869574b6964SAndre Oppermann 		 * completely ignore the segment and drop it.
870574b6964SAndre Oppermann 		 */
871603724d3SBjoern A. Zeeb 		if ((V_blackhole == 1 && (thflags & TH_SYN)) ||
872603724d3SBjoern A. Zeeb 		    V_blackhole == 2)
8731929eae1SAndre Oppermann 			goto dropunlock;
874574b6964SAndre Oppermann 
875a57815efSBosko Milekic 		rstreason = BANDLIM_RST_CLOSEDPORT;
876a57815efSBosko Milekic 		goto dropwithreset;
877816a3d83SPoul-Henning Kamp 	}
878fa046d87SRobert Watson 	INP_WLOCK_ASSERT(inp);
87980cb9f21SKip Macy 	if (!(inp->inp_flags & INP_HW_FLOWID)
88080cb9f21SKip Macy 	    && (m->m_flags & M_FLOWID)
88180cb9f21SKip Macy 	    && ((inp->inp_socket == NULL)
88280cb9f21SKip Macy 		|| !(inp->inp_socket->so_options & SO_ACCEPTCONN))) {
88380cb9f21SKip Macy 		inp->inp_flags |= INP_HW_FLOWID;
88480cb9f21SKip Macy 		inp->inp_flags &= ~INP_SW_FLOWID;
88580cb9f21SKip Macy 		inp->inp_flowid = m->m_pkthdr.flowid;
8862f719932SAdrian Chadd 		inp->inp_flowtype = M_HASHTYPE_GET(m);
88780cb9f21SKip Macy 	}
888a2589465SKen Smith #ifdef IPSEC
889a2589465SKen Smith #ifdef INET6
890a2589465SKen Smith 	if (isipv6 && ipsec6_in_reject(m, inp)) {
8916794f460SAndrey V. Elsukov 		IPSEC6STAT_INC(ips_in_polvio);
892a2589465SKen Smith 		goto dropunlock;
893a2589465SKen Smith 	} else
894a2589465SKen Smith #endif /* INET6 */
895a2589465SKen Smith 	if (ipsec4_in_reject(m, inp) != 0) {
8966794f460SAndrey V. Elsukov 		IPSECSTAT_INC(ips_in_polvio);
897a2589465SKen Smith 		goto dropunlock;
898a2589465SKen Smith 	}
899a2589465SKen Smith #endif /* IPSEC */
900a2589465SKen Smith 
9018d573cc1SAndre Oppermann 	/*
9028d573cc1SAndre Oppermann 	 * Check the minimum TTL for socket.
9038d573cc1SAndre Oppermann 	 */
90434f83c52SGeorge V. Neville-Neil 	if (inp->inp_ip_minttl != 0) {
90534f83c52SGeorge V. Neville-Neil #ifdef INET6
90634f83c52SGeorge V. Neville-Neil 		if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim)
907302ce8d6SAndre Oppermann 			goto dropunlock;
90802707462SAndre Oppermann 		else
90934f83c52SGeorge V. Neville-Neil #endif
91034f83c52SGeorge V. Neville-Neil 		if (inp->inp_ip_minttl > ip->ip_ttl)
911302ce8d6SAndre Oppermann 			goto dropunlock;
91234f83c52SGeorge V. Neville-Neil 	}
913936cd18dSAndre Oppermann 
914340c35deSJonathan Lemon 	/*
915252ca428SRobert Watson 	 * A previous connection in TIMEWAIT state is supposed to catch stray
916252ca428SRobert Watson 	 * or duplicate segments arriving late.  If this segment was a
9170989f56cSRobert Watson 	 * legitimate new connection attempt, the old INPCB gets removed and
918252ca428SRobert Watson 	 * we can try again to find a listening socket.
919252ca428SRobert Watson 	 *
920fa046d87SRobert Watson 	 * At this point, due to earlier optimism, we may hold only an inpcb
921fa046d87SRobert Watson 	 * lock, and not the inpcbinfo write lock.  If so, we need to try to
922fa046d87SRobert Watson 	 * acquire it, or if that fails, acquire a reference on the inpcb,
923fa046d87SRobert Watson 	 * drop all locks, acquire a global write lock, and then re-acquire
924fa046d87SRobert Watson 	 * the inpcb lock.  We may at that point discover that another thread
925fa046d87SRobert Watson 	 * has tried to free the inpcb, in which case we need to loop back
926fa046d87SRobert Watson 	 * and try to find a new inpcb to deliver to.
927fa046d87SRobert Watson 	 *
928fa046d87SRobert Watson 	 * XXXRW: It may be time to rethink timewait locking.
929340c35deSJonathan Lemon 	 */
930883e9bc4SRobert Watson relocked:
931ad71fe3cSRobert Watson 	if (inp->inp_flags & INP_TIMEWAIT) {
932fa046d87SRobert Watson 		if (ti_locked == TI_UNLOCKED) {
933fa046d87SRobert Watson 			if (INP_INFO_TRY_WLOCK(&V_tcbinfo) == 0) {
934252ca428SRobert Watson 				in_pcbref(inp);
935252ca428SRobert Watson 				INP_WUNLOCK(inp);
936252ca428SRobert Watson 				INP_INFO_WLOCK(&V_tcbinfo);
937252ca428SRobert Watson 				ti_locked = TI_WLOCKED;
938252ca428SRobert Watson 				INP_WLOCK(inp);
939fa046d87SRobert Watson 				if (in_pcbrele_wlocked(inp)) {
940252ca428SRobert Watson 					inp = NULL;
941252ca428SRobert Watson 					goto findpcb;
942252ca428SRobert Watson 				}
943f681a5fdSRobert Watson 			} else
944252ca428SRobert Watson 				ti_locked = TI_WLOCKED;
945252ca428SRobert Watson 		}
946252ca428SRobert Watson 		INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
947252ca428SRobert Watson 
948340c35deSJonathan Lemon 		if (thflags & TH_SYN)
949f72167f4SAndre Oppermann 			tcp_dooptions(&to, optp, optlen, TO_SYN);
9508d573cc1SAndre Oppermann 		/*
9518d573cc1SAndre Oppermann 		 * NB: tcp_twcheck unlocks the INP and frees the mbuf.
9528d573cc1SAndre Oppermann 		 */
9532104448fSAndre Oppermann 		if (tcp_twcheck(inp, &to, th, m, tlen))
954340c35deSJonathan Lemon 			goto findpcb;
955603724d3SBjoern A. Zeeb 		INP_INFO_WUNLOCK(&V_tcbinfo);
9568f5a8818SKevin Lo 		return (IPPROTO_DONE);
957340c35deSJonathan Lemon 	}
958794235b7SAndre Oppermann 	/*
959794235b7SAndre Oppermann 	 * The TCPCB may no longer exist if the connection is winding
960794235b7SAndre Oppermann 	 * down or it is in the CLOSED state.  Either way we drop the
961794235b7SAndre Oppermann 	 * segment and send an appropriate response.
962794235b7SAndre Oppermann 	 */
963df8bae1dSRodney W. Grimes 	tp = intotcpcb(inp);
964a160e630SAndre Oppermann 	if (tp == NULL || tp->t_state == TCPS_CLOSED) {
965a57815efSBosko Milekic 		rstreason = BANDLIM_RST_CLOSEDPORT;
966a57815efSBosko Milekic 		goto dropwithreset;
96709f81a46SBosko Milekic 	}
968df8bae1dSRodney W. Grimes 
96909fe6320SNavdeep Parhar #ifdef TCP_OFFLOAD
97009fe6320SNavdeep Parhar 	if (tp->t_flags & TF_TOE) {
97109fe6320SNavdeep Parhar 		tcp_offload_input(tp, m);
97209fe6320SNavdeep Parhar 		m = NULL;	/* consumed by the TOE driver */
97309fe6320SNavdeep Parhar 		goto dropunlock;
97409fe6320SNavdeep Parhar 	}
97509fe6320SNavdeep Parhar #endif
97609fe6320SNavdeep Parhar 
977252ca428SRobert Watson 	/*
978252ca428SRobert Watson 	 * We've identified a valid inpcb, but it could be that we need an
979fa046d87SRobert Watson 	 * inpcbinfo write lock but don't hold it.  In this case, attempt to
980fa046d87SRobert Watson 	 * acquire using the same strategy as the TIMEWAIT case above.  If we
981fa046d87SRobert Watson 	 * relock, we have to jump back to 'relocked' as the connection might
982fa046d87SRobert Watson 	 * now be in TIMEWAIT.
983252ca428SRobert Watson 	 */
984fa046d87SRobert Watson #ifdef INVARIANTS
985a7c7f2a7SJohn Baldwin 	if ((thflags & (TH_FIN | TH_RST)) != 0)
986fa046d87SRobert Watson 		INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
987fa046d87SRobert Watson #endif
988a7c7f2a7SJohn Baldwin 	if (!((tp->t_state == TCPS_ESTABLISHED && (thflags & TH_SYN) == 0) ||
989a7c7f2a7SJohn Baldwin 	    (tp->t_state == TCPS_LISTEN && (thflags & TH_SYN)))) {
990fa046d87SRobert Watson 		if (ti_locked == TI_UNLOCKED) {
991fa046d87SRobert Watson 			if (INP_INFO_TRY_WLOCK(&V_tcbinfo) == 0) {
992252ca428SRobert Watson 				in_pcbref(inp);
993252ca428SRobert Watson 				INP_WUNLOCK(inp);
994252ca428SRobert Watson 				INP_INFO_WLOCK(&V_tcbinfo);
995252ca428SRobert Watson 				ti_locked = TI_WLOCKED;
996252ca428SRobert Watson 				INP_WLOCK(inp);
997fa046d87SRobert Watson 				if (in_pcbrele_wlocked(inp)) {
998252ca428SRobert Watson 					inp = NULL;
999252ca428SRobert Watson 					goto findpcb;
1000252ca428SRobert Watson 				}
1001883e9bc4SRobert Watson 				goto relocked;
1002f681a5fdSRobert Watson 			} else
1003252ca428SRobert Watson 				ti_locked = TI_WLOCKED;
1004252ca428SRobert Watson 		}
1005252ca428SRobert Watson 		INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1006252ca428SRobert Watson 	}
1007252ca428SRobert Watson 
1008c488362eSRobert Watson #ifdef MAC
10098501a69cSRobert Watson 	INP_WLOCK_ASSERT(inp);
101030d239bcSRobert Watson 	if (mac_inpcb_check_deliver(inp, m))
1011302ce8d6SAndre Oppermann 		goto dropunlock;
1012c488362eSRobert Watson #endif
1013a557af22SRobert Watson 	so = inp->inp_socket;
1014302ce8d6SAndre Oppermann 	KASSERT(so != NULL, ("%s: so == NULL", __func__));
1015610ee2f9SDavid Greenman #ifdef TCPDEBUG
1016df8bae1dSRodney W. Grimes 	if (so->so_options & SO_DEBUG) {
1017df8bae1dSRodney W. Grimes 		ostate = tp->t_state;
101810fe523eSMaxim Konovalov #ifdef INET6
10196f697424SBjoern A. Zeeb 		if (isipv6) {
1020540e8b7eSJeffrey Hsu 			bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6));
1021d30d90dcSMaxim Konovalov 		} else
10226f697424SBjoern A. Zeeb #endif
1023540e8b7eSJeffrey Hsu 			bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip));
1024fb59c426SYoshinobu Inoue 		tcp_savetcp = *th;
1025df8bae1dSRodney W. Grimes 	}
1026b287c6c7SBjoern A. Zeeb #endif /* TCPDEBUG */
1027db33b3e6SAndre Oppermann 	/*
1028db33b3e6SAndre Oppermann 	 * When the socket is accepting connections (the INPCB is in LISTEN
1029db33b3e6SAndre Oppermann 	 * state) we look into the SYN cache if this is a new connection
1030a7c7f2a7SJohn Baldwin 	 * attempt or the completion of a previous one.
1031db33b3e6SAndre Oppermann 	 */
1032540e8b7eSJeffrey Hsu 	if (so->so_options & SO_ACCEPTCONN) {
1033540e8b7eSJeffrey Hsu 		struct in_conninfo inc;
1034540e8b7eSJeffrey Hsu 
10357824d002SAndre Oppermann 		KASSERT(tp->t_state == TCPS_LISTEN, ("%s: so accepting but "
10367824d002SAndre Oppermann 		    "tp not listening", __func__));
10378bfb1918SAndre Oppermann 		bzero(&inc, sizeof(inc));
1038302ce8d6SAndre Oppermann #ifdef INET6
1039be2ac88cSJonathan Lemon 		if (isipv6) {
1040dcdb4371SBjoern A. Zeeb 			inc.inc_flags |= INC_ISIPV6;
1041be2ac88cSJonathan Lemon 			inc.inc6_faddr = ip6->ip6_src;
1042be2ac88cSJonathan Lemon 			inc.inc6_laddr = ip6->ip6_dst;
1043302ce8d6SAndre Oppermann 		} else
1044302ce8d6SAndre Oppermann #endif
1045302ce8d6SAndre Oppermann 		{
1046be2ac88cSJonathan Lemon 			inc.inc_faddr = ip->ip_src;
1047be2ac88cSJonathan Lemon 			inc.inc_laddr = ip->ip_dst;
1048be2ac88cSJonathan Lemon 		}
1049be2ac88cSJonathan Lemon 		inc.inc_fport = th->th_sport;
1050be2ac88cSJonathan Lemon 		inc.inc_lport = th->th_dport;
10517973fba3SJulian Elischer 		inc.inc_fibnum = so->so_fibnum;
1052be2ac88cSJonathan Lemon 
1053fb59c426SYoshinobu Inoue 		/*
10548d573cc1SAndre Oppermann 		 * Check for an existing connection attempt in syncache if
10558d573cc1SAndre Oppermann 		 * the flag is only ACK.  A successful lookup creates a new
10568d573cc1SAndre Oppermann 		 * socket appended to the listen queue in SYN_RECEIVED state.
1057fb59c426SYoshinobu Inoue 		 */
1058be2ac88cSJonathan Lemon 		if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) {
1059a7c7f2a7SJohn Baldwin 
1060a7c7f2a7SJohn Baldwin 			INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1061bf6d304aSAndre Oppermann 			/*
1062bf6d304aSAndre Oppermann 			 * Parse the TCP options here because
1063bf6d304aSAndre Oppermann 			 * syncookies need access to the reflected
1064bf6d304aSAndre Oppermann 			 * timestamp.
1065bf6d304aSAndre Oppermann 			 */
1066bf6d304aSAndre Oppermann 			tcp_dooptions(&to, optp, optlen, 0);
10679fa198beSAndre Oppermann 			/*
10689fa198beSAndre Oppermann 			 * NB: syncache_expand() doesn't unlock
10699fa198beSAndre Oppermann 			 * inp and tcpinfo locks.
10709fa198beSAndre Oppermann 			 */
1071bf6d304aSAndre Oppermann 			if (!syncache_expand(&inc, &to, th, &so, m)) {
10724195b4afSPaul Traina 				/*
1073e207f800SAndre Oppermann 				 * No syncache entry or ACK was not
1074be2ac88cSJonathan Lemon 				 * for our SYN/ACK.  Send a RST.
10758d573cc1SAndre Oppermann 				 * NB: syncache did its own logging
10768d573cc1SAndre Oppermann 				 * of the failure cause.
10774195b4afSPaul Traina 				 */
1078be2ac88cSJonathan Lemon 				rstreason = BANDLIM_RST_OPENPORT;
1079be2ac88cSJonathan Lemon 				goto dropwithreset;
1080be2ac88cSJonathan Lemon 			}
1081f76fcf6dSJeffrey Hsu 			if (so == NULL) {
1082be2ac88cSJonathan Lemon 				/*
1083e207f800SAndre Oppermann 				 * We completed the 3-way handshake
1084e207f800SAndre Oppermann 				 * but could not allocate a socket
1085e207f800SAndre Oppermann 				 * either due to memory shortage,
1086e207f800SAndre Oppermann 				 * listen queue length limits or
1087a160e630SAndre Oppermann 				 * global socket limits.  Send RST
1088a160e630SAndre Oppermann 				 * or wait and have the remote end
1089a160e630SAndre Oppermann 				 * retransmit the ACK for another
1090a160e630SAndre Oppermann 				 * try.
1091be2ac88cSJonathan Lemon 				 */
1092a160e630SAndre Oppermann 				if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1093a160e630SAndre Oppermann 					log(LOG_DEBUG, "%s; %s: Listen socket: "
10948d573cc1SAndre Oppermann 					    "Socket allocation failed due to "
10958d573cc1SAndre Oppermann 					    "limits or memory shortage, %s\n",
1096ac957cd2SJulian Elischer 					    s, __func__,
1097ac957cd2SJulian Elischer 					    V_tcp_sc_rst_sock_fail ?
1098ac957cd2SJulian Elischer 					    "sending RST" : "try again");
1099603724d3SBjoern A. Zeeb 				if (V_tcp_sc_rst_sock_fail) {
1100e207f800SAndre Oppermann 					rstreason = BANDLIM_UNLIMITED;
1101e207f800SAndre Oppermann 					goto dropwithreset;
1102a160e630SAndre Oppermann 				} else
1103a160e630SAndre Oppermann 					goto dropunlock;
1104f76fcf6dSJeffrey Hsu 			}
1105be2ac88cSJonathan Lemon 			/*
1106be2ac88cSJonathan Lemon 			 * Socket is created in state SYN_RECEIVED.
11078d573cc1SAndre Oppermann 			 * Unlock the listen socket, lock the newly
11088d573cc1SAndre Oppermann 			 * created socket and update the tp variable.
1109be2ac88cSJonathan Lemon 			 */
11108501a69cSRobert Watson 			INP_WUNLOCK(inp);	/* listen socket */
1111be2ac88cSJonathan Lemon 			inp = sotoinpcb(so);
11128501a69cSRobert Watson 			INP_WLOCK(inp);		/* new connection */
1113be2ac88cSJonathan Lemon 			tp = intotcpcb(inp);
11148d573cc1SAndre Oppermann 			KASSERT(tp->t_state == TCPS_SYN_RECEIVED,
11158d573cc1SAndre Oppermann 			    ("%s: ", __func__));
11162903309aSAttilio Rao #ifdef TCP_SIGNATURE
11172903309aSAttilio Rao 			if (sig_checked == 0)  {
11182903309aSAttilio Rao 				tcp_dooptions(&to, optp, optlen,
11192903309aSAttilio Rao 				    (thflags & TH_SYN) ? TO_SYN : 0);
11202903309aSAttilio Rao 				if (!tcp_signature_verify_input(m, off0, tlen,
11212903309aSAttilio Rao 				    optlen, &to, th, tp->t_flags)) {
11222903309aSAttilio Rao 
11232903309aSAttilio Rao 					/*
11242903309aSAttilio Rao 					 * In SYN_SENT state if it receives an
11252903309aSAttilio Rao 					 * RST, it is allowed for further
11262903309aSAttilio Rao 					 * processing.
11272903309aSAttilio Rao 					 */
11282903309aSAttilio Rao 					if ((thflags & TH_RST) == 0 ||
11292903309aSAttilio Rao 					    (tp->t_state == TCPS_SYN_SENT) == 0)
11302903309aSAttilio Rao 						goto dropunlock;
11312903309aSAttilio Rao 				}
11322903309aSAttilio Rao 				sig_checked = 1;
11332903309aSAttilio Rao 			}
11342903309aSAttilio Rao #endif
11352903309aSAttilio Rao 
1136be2ac88cSJonathan Lemon 			/*
1137302ce8d6SAndre Oppermann 			 * Process the segment and the data it
1138302ce8d6SAndre Oppermann 			 * contains.  tcp_do_segment() consumes
1139302ce8d6SAndre Oppermann 			 * the mbuf chain and unlocks the inpcb.
1140302ce8d6SAndre Oppermann 			 */
1141f2512ba1SRui Paulo 			tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen,
1142252ca428SRobert Watson 			    iptos, ti_locked);
1143603724d3SBjoern A. Zeeb 			INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
11448f5a8818SKevin Lo 			return (IPPROTO_DONE);
1145be2ac88cSJonathan Lemon 		}
1146a160e630SAndre Oppermann 		/*
11478d573cc1SAndre Oppermann 		 * Segment flag validation for new connection attempts:
11488d573cc1SAndre Oppermann 		 *
1149a160e630SAndre Oppermann 		 * Our (SYN|ACK) response was rejected.
1150a160e630SAndre Oppermann 		 * Check with syncache and remove entry to prevent
1151a160e630SAndre Oppermann 		 * retransmits.
115219bc77c5SAndre Oppermann 		 *
115319bc77c5SAndre Oppermann 		 * NB: syncache_chkrst does its own logging of failure
115419bc77c5SAndre Oppermann 		 * causes.
1155a160e630SAndre Oppermann 		 */
1156a160e630SAndre Oppermann 		if (thflags & TH_RST) {
115719bc77c5SAndre Oppermann 			syncache_chkrst(&inc, th);
1158a160e630SAndre Oppermann 			goto dropunlock;
1159a160e630SAndre Oppermann 		}
1160a160e630SAndre Oppermann 		/*
1161a160e630SAndre Oppermann 		 * We can't do anything without SYN.
1162a160e630SAndre Oppermann 		 */
1163a160e630SAndre Oppermann 		if ((thflags & TH_SYN) == 0) {
1164a160e630SAndre Oppermann 			if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1165a160e630SAndre Oppermann 				log(LOG_DEBUG, "%s; %s: Listen socket: "
1166773673c1SAndre Oppermann 				    "SYN is missing, segment ignored\n",
11678d573cc1SAndre Oppermann 				    s, __func__);
116878b50714SRobert Watson 			TCPSTAT_INC(tcps_badsyn);
1169a160e630SAndre Oppermann 			goto dropunlock;
1170a160e630SAndre Oppermann 		}
1171a160e630SAndre Oppermann 		/*
1172a160e630SAndre Oppermann 		 * (SYN|ACK) is bogus on a listen socket.
1173a160e630SAndre Oppermann 		 */
1174fb59c426SYoshinobu Inoue 		if (thflags & TH_ACK) {
1175a160e630SAndre Oppermann 			if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1176a160e630SAndre Oppermann 				log(LOG_DEBUG, "%s; %s: Listen socket: "
11778d573cc1SAndre Oppermann 				    "SYN|ACK invalid, segment rejected\n",
11788d573cc1SAndre Oppermann 				    s, __func__);
1179a160e630SAndre Oppermann 			syncache_badack(&inc);	/* XXX: Not needed! */
118078b50714SRobert Watson 			TCPSTAT_INC(tcps_badsyn);
1181a57815efSBosko Milekic 			rstreason = BANDLIM_RST_OPENPORT;
1182a57815efSBosko Milekic 			goto dropwithreset;
11834195b4afSPaul Traina 		}
1184a160e630SAndre Oppermann 		/*
1185a160e630SAndre Oppermann 		 * If the drop_synfin option is enabled, drop all
1186a160e630SAndre Oppermann 		 * segments with both the SYN and FIN bits set.
1187a160e630SAndre Oppermann 		 * This prevents e.g. nmap from identifying the
1188a160e630SAndre Oppermann 		 * TCP/IP stack.
1189a160e630SAndre Oppermann 		 * XXX: Poor reasoning.  nmap has other methods
1190a160e630SAndre Oppermann 		 * and is constantly refining its stack detection
1191a160e630SAndre Oppermann 		 * strategies.
11928d573cc1SAndre Oppermann 		 * XXX: This is a violation of the TCP specification
1193a160e630SAndre Oppermann 		 * and was used by RFC1644.
1194a160e630SAndre Oppermann 		 */
1195603724d3SBjoern A. Zeeb 		if ((thflags & TH_FIN) && V_drop_synfin) {
1196a160e630SAndre Oppermann 			if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1197a160e630SAndre Oppermann 				log(LOG_DEBUG, "%s; %s: Listen socket: "
1198773673c1SAndre Oppermann 				    "SYN|FIN segment ignored (based on "
11998d573cc1SAndre Oppermann 				    "sysctl setting)\n", s, __func__);
120078b50714SRobert Watson 			TCPSTAT_INC(tcps_badsyn);
1201302ce8d6SAndre Oppermann 			goto dropunlock;
1202ebb0cbeaSPaul Traina 		}
1203be2ac88cSJonathan Lemon 		/*
1204be2ac88cSJonathan Lemon 		 * Segment's flags are (SYN) or (SYN|FIN).
1205a160e630SAndre Oppermann 		 *
1206a160e630SAndre Oppermann 		 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored
1207a160e630SAndre Oppermann 		 * as they do not affect the state of the TCP FSM.
1208a160e630SAndre Oppermann 		 * The data pointed to by TH_URG and th_urp is ignored.
1209be2ac88cSJonathan Lemon 		 */
1210a160e630SAndre Oppermann 		KASSERT((thflags & (TH_RST|TH_ACK)) == 0,
1211a160e630SAndre Oppermann 		    ("%s: Listen socket: TH_RST or TH_ACK set", __func__));
1212a160e630SAndre Oppermann 		KASSERT(thflags & (TH_SYN),
1213a160e630SAndre Oppermann 		    ("%s: Listen socket: TH_SYN not set", __func__));
121433841545SHajimu UMEMOTO #ifdef INET6
121533841545SHajimu UMEMOTO 		/*
121633841545SHajimu UMEMOTO 		 * If deprecated address is forbidden,
121733841545SHajimu UMEMOTO 		 * we do not accept SYN to deprecated interface
121833841545SHajimu UMEMOTO 		 * address to prevent any new inbound connection from
121933841545SHajimu UMEMOTO 		 * getting established.
122033841545SHajimu UMEMOTO 		 * When we do not accept SYN, we send a TCP RST,
122133841545SHajimu UMEMOTO 		 * with deprecated source address (instead of dropping
122233841545SHajimu UMEMOTO 		 * it).  We compromise it as it is much better for peer
122333841545SHajimu UMEMOTO 		 * to send a RST, and RST will be the final packet
122433841545SHajimu UMEMOTO 		 * for the exchange.
122533841545SHajimu UMEMOTO 		 *
122633841545SHajimu UMEMOTO 		 * If we do not forbid deprecated addresses, we accept
122733841545SHajimu UMEMOTO 		 * the SYN packet.  RFC2462 does not suggest dropping
122833841545SHajimu UMEMOTO 		 * SYN in this case.
122933841545SHajimu UMEMOTO 		 * If we decipher RFC2462 5.5.4, it says like this:
123033841545SHajimu UMEMOTO 		 * 1. use of deprecated addr with existing
123133841545SHajimu UMEMOTO 		 *    communication is okay - "SHOULD continue to be
123233841545SHajimu UMEMOTO 		 *    used"
123333841545SHajimu UMEMOTO 		 * 2. use of it with new communication:
123433841545SHajimu UMEMOTO 		 *   (2a) "SHOULD NOT be used if alternate address
123533841545SHajimu UMEMOTO 		 *        with sufficient scope is available"
123633841545SHajimu UMEMOTO 		 *   (2b) nothing mentioned otherwise.
123733841545SHajimu UMEMOTO 		 * Here we fall into (2b) case as we have no choice in
123833841545SHajimu UMEMOTO 		 * our source address selection - we must obey the peer.
123933841545SHajimu UMEMOTO 		 *
124033841545SHajimu UMEMOTO 		 * The wording in RFC2462 is confusing, and there are
124133841545SHajimu UMEMOTO 		 * multiple description text for deprecated address
124233841545SHajimu UMEMOTO 		 * handling - worse, they are not exactly the same.
124333841545SHajimu UMEMOTO 		 * I believe 5.5.4 is the best one, so we follow 5.5.4.
124433841545SHajimu UMEMOTO 		 */
1245603724d3SBjoern A. Zeeb 		if (isipv6 && !V_ip6_use_deprecated) {
124633841545SHajimu UMEMOTO 			struct in6_ifaddr *ia6;
124733841545SHajimu UMEMOTO 
12488c0fec80SRobert Watson 			ia6 = ip6_getdstifaddr(m);
12498c0fec80SRobert Watson 			if (ia6 != NULL &&
125033841545SHajimu UMEMOTO 			    (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
12518c0fec80SRobert Watson 				ifa_free(&ia6->ia_ifa);
1252a160e630SAndre Oppermann 				if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1253a160e630SAndre Oppermann 				    log(LOG_DEBUG, "%s; %s: Listen socket: "
12548d573cc1SAndre Oppermann 					"Connection attempt to deprecated "
12558d573cc1SAndre Oppermann 					"IPv6 address rejected\n",
1256a160e630SAndre Oppermann 					s, __func__);
125733841545SHajimu UMEMOTO 				rstreason = BANDLIM_RST_OPENPORT;
125833841545SHajimu UMEMOTO 				goto dropwithreset;
125933841545SHajimu UMEMOTO 			}
126077d396fdSMaksim Yevmenkin 			if (ia6)
12618c0fec80SRobert Watson 				ifa_free(&ia6->ia_ifa);
126233841545SHajimu UMEMOTO 		}
1263b287c6c7SBjoern A. Zeeb #endif /* INET6 */
126465f28919SJesper Skriver 		/*
1265db33b3e6SAndre Oppermann 		 * Basic sanity checks on incoming SYN requests:
12668d573cc1SAndre Oppermann 		 *   Don't respond if the destination is a link layer
1267db33b3e6SAndre Oppermann 		 *	broadcast according to RFC1122 4.2.3.10, p. 104.
12688d573cc1SAndre Oppermann 		 *   If it is from this socket it must be forged.
12698d573cc1SAndre Oppermann 		 *   Don't respond if the source or destination is a
12708d573cc1SAndre Oppermann 		 *	global or subnet broad- or multicast address.
127193ec91baSCrist J. Clark 		 *   Note that it is quite possible to receive unicast
127293ec91baSCrist J. Clark 		 *	link-layer packets with a broadcast IP address. Use
127393ec91baSCrist J. Clark 		 *	in_broadcast() to find them.
1274be2ac88cSJonathan Lemon 		 */
12758d573cc1SAndre Oppermann 		if (m->m_flags & (M_BCAST|M_MCAST)) {
12768d573cc1SAndre Oppermann 			if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
12778d573cc1SAndre Oppermann 			    log(LOG_DEBUG, "%s; %s: Listen socket: "
12788d573cc1SAndre Oppermann 				"Connection attempt from broad- or multicast "
1279773673c1SAndre Oppermann 				"link layer address ignored\n", s, __func__);
1280302ce8d6SAndre Oppermann 			goto dropunlock;
12818d573cc1SAndre Oppermann 		}
1282db33b3e6SAndre Oppermann #ifdef INET6
1283b287c6c7SBjoern A. Zeeb 		if (isipv6) {
1284db33b3e6SAndre Oppermann 			if (th->th_dport == th->th_sport &&
1285a160e630SAndre Oppermann 			    IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) {
1286a160e630SAndre Oppermann 				if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1287a160e630SAndre Oppermann 				    log(LOG_DEBUG, "%s; %s: Listen socket: "
12888d573cc1SAndre Oppermann 					"Connection attempt to/from self "
1289773673c1SAndre Oppermann 					"ignored\n", s, __func__);
1290302ce8d6SAndre Oppermann 				goto dropunlock;
1291a160e630SAndre Oppermann 			}
1292be2ac88cSJonathan Lemon 			if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
1293a160e630SAndre Oppermann 			    IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) {
1294a160e630SAndre Oppermann 				if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1295a160e630SAndre Oppermann 				    log(LOG_DEBUG, "%s; %s: Listen socket: "
12968d573cc1SAndre Oppermann 					"Connection attempt from/to multicast "
1297773673c1SAndre Oppermann 					"address ignored\n", s, __func__);
1298302ce8d6SAndre Oppermann 				goto dropunlock;
1299a160e630SAndre Oppermann 			}
1300b287c6c7SBjoern A. Zeeb 		}
1301db33b3e6SAndre Oppermann #endif
1302b287c6c7SBjoern A. Zeeb #if defined(INET) && defined(INET6)
1303b287c6c7SBjoern A. Zeeb 		else
1304b287c6c7SBjoern A. Zeeb #endif
1305b287c6c7SBjoern A. Zeeb #ifdef INET
1306b287c6c7SBjoern A. Zeeb 		{
1307db33b3e6SAndre Oppermann 			if (th->th_dport == th->th_sport &&
1308a160e630SAndre Oppermann 			    ip->ip_dst.s_addr == ip->ip_src.s_addr) {
1309a160e630SAndre Oppermann 				if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1310a160e630SAndre Oppermann 				    log(LOG_DEBUG, "%s; %s: Listen socket: "
13118d573cc1SAndre Oppermann 					"Connection attempt from/to self "
1312773673c1SAndre Oppermann 					"ignored\n", s, __func__);
1313302ce8d6SAndre Oppermann 				goto dropunlock;
1314a160e630SAndre Oppermann 			}
1315be2ac88cSJonathan Lemon 			if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
1316be2ac88cSJonathan Lemon 			    IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
13172ca2159fSCrist J. Clark 			    ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
1318a160e630SAndre Oppermann 			    in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) {
1319a160e630SAndre Oppermann 				if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1320a160e630SAndre Oppermann 				    log(LOG_DEBUG, "%s; %s: Listen socket: "
13218d573cc1SAndre Oppermann 					"Connection attempt from/to broad- "
1322773673c1SAndre Oppermann 					"or multicast address ignored\n",
1323a160e630SAndre Oppermann 					s, __func__);
1324302ce8d6SAndre Oppermann 				goto dropunlock;
1325c068736aSJeffrey Hsu 			}
1326a160e630SAndre Oppermann 		}
1327b287c6c7SBjoern A. Zeeb #endif
1328be2ac88cSJonathan Lemon 		/*
1329db33b3e6SAndre Oppermann 		 * SYN appears to be valid.  Create compressed TCP state
1330db33b3e6SAndre Oppermann 		 * for syncache.
1331be2ac88cSJonathan Lemon 		 */
13323c653157SHartmut Brandt #ifdef TCPDEBUG
13333c653157SHartmut Brandt 		if (so->so_options & SO_DEBUG)
13343c653157SHartmut Brandt 			tcp_trace(TA_INPUT, ostate, tp,
13353c653157SHartmut Brandt 			    (void *)tcp_saveipgen, &tcp_savetcp, 0);
13363c653157SHartmut Brandt #endif
1337f72167f4SAndre Oppermann 		tcp_dooptions(&to, optp, optlen, TO_SYN);
133809fe6320SNavdeep Parhar 		syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL);
1339be2ac88cSJonathan Lemon 		/*
13404d6e7130SAndre Oppermann 		 * Entry added to syncache and mbuf consumed.
1341a7c7f2a7SJohn Baldwin 		 * Only the listen socket is unlocked by syncache_add().
1342be2ac88cSJonathan Lemon 		 */
1343a7c7f2a7SJohn Baldwin 		if (ti_locked == TI_WLOCKED) {
1344a7c7f2a7SJohn Baldwin 			INP_INFO_WUNLOCK(&V_tcbinfo);
1345a7c7f2a7SJohn Baldwin 			ti_locked = TI_UNLOCKED;
1346a7c7f2a7SJohn Baldwin 		}
1347603724d3SBjoern A. Zeeb 		INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
13488f5a8818SKevin Lo 		return (IPPROTO_DONE);
1349982c1675SAndre Oppermann 	} else if (tp->t_state == TCPS_LISTEN) {
1350982c1675SAndre Oppermann 		/*
1351982c1675SAndre Oppermann 		 * When a listen socket is torn down the SO_ACCEPTCONN
1352982c1675SAndre Oppermann 		 * flag is removed first while connections are drained
1353982c1675SAndre Oppermann 		 * from the accept queue in a unlock/lock cycle of the
1354982c1675SAndre Oppermann 		 * ACCEPT_LOCK, opening a race condition allowing a SYN
1355982c1675SAndre Oppermann 		 * attempt go through unhandled.
1356982c1675SAndre Oppermann 		 */
1357982c1675SAndre Oppermann 		goto dropunlock;
1358f76fcf6dSJeffrey Hsu 	}
1359db33b3e6SAndre Oppermann 
13602903309aSAttilio Rao #ifdef TCP_SIGNATURE
13612903309aSAttilio Rao 	if (sig_checked == 0)  {
13622903309aSAttilio Rao 		tcp_dooptions(&to, optp, optlen,
13632903309aSAttilio Rao 		    (thflags & TH_SYN) ? TO_SYN : 0);
13642903309aSAttilio Rao 		if (!tcp_signature_verify_input(m, off0, tlen, optlen, &to,
13652903309aSAttilio Rao 		    th, tp->t_flags)) {
13662903309aSAttilio Rao 
13672903309aSAttilio Rao 			/*
13682903309aSAttilio Rao 			 * In SYN_SENT state if it receives an RST, it is
13692903309aSAttilio Rao 			 * allowed for further processing.
13702903309aSAttilio Rao 			 */
13712903309aSAttilio Rao 			if ((thflags & TH_RST) == 0 ||
13722903309aSAttilio Rao 			    (tp->t_state == TCPS_SYN_SENT) == 0)
13732903309aSAttilio Rao 				goto dropunlock;
13742903309aSAttilio Rao 		}
13752903309aSAttilio Rao 		sig_checked = 1;
13762903309aSAttilio Rao 	}
13772903309aSAttilio Rao #endif
13782903309aSAttilio Rao 
1379fa22ce15SAdrian Chadd 	TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th);
138057f60867SMark Johnston 
1381302ce8d6SAndre Oppermann 	/*
13828d573cc1SAndre Oppermann 	 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later
13838d573cc1SAndre Oppermann 	 * state.  tcp_do_segment() always consumes the mbuf chain, unlocks
13848d573cc1SAndre Oppermann 	 * the inpcb, and unlocks pcbinfo.
1385302ce8d6SAndre Oppermann 	 */
1386252ca428SRobert Watson 	tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos, ti_locked);
1387603724d3SBjoern A. Zeeb 	INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
13888f5a8818SKevin Lo 	return (IPPROTO_DONE);
1389be2ac88cSJonathan Lemon 
1390302ce8d6SAndre Oppermann dropwithreset:
1391fa22ce15SAdrian Chadd 	TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th);
139257f60867SMark Johnston 
1393fa046d87SRobert Watson 	if (ti_locked == TI_WLOCKED) {
1394dd8ac7f9SRobert Watson 		INP_INFO_WUNLOCK(&V_tcbinfo);
1395252ca428SRobert Watson 		ti_locked = TI_UNLOCKED;
1396fa046d87SRobert Watson 	}
1397fa046d87SRobert Watson #ifdef INVARIANTS
1398fa046d87SRobert Watson 	else {
1399fa046d87SRobert Watson 		KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropwithreset "
1400fa046d87SRobert Watson 		    "ti_locked: %d", __func__, ti_locked));
1401fa046d87SRobert Watson 		INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1402fa046d87SRobert Watson 	}
1403fa046d87SRobert Watson #endif
1404014ea782SRobert Watson 
1405014ea782SRobert Watson 	if (inp != NULL) {
1406302ce8d6SAndre Oppermann 		tcp_dropwithreset(m, th, tp, tlen, rstreason);
1407014ea782SRobert Watson 		INP_WUNLOCK(inp);
1408dd8ac7f9SRobert Watson 	} else
1409014ea782SRobert Watson 		tcp_dropwithreset(m, th, NULL, tlen, rstreason);
1410302ce8d6SAndre Oppermann 	m = NULL;	/* mbuf chain got consumed. */
1411014ea782SRobert Watson 	goto drop;
1412014ea782SRobert Watson 
1413302ce8d6SAndre Oppermann dropunlock:
141457f60867SMark Johnston 	if (m != NULL)
1415fa22ce15SAdrian Chadd 		TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th);
141657f60867SMark Johnston 
1417fa046d87SRobert Watson 	if (ti_locked == TI_WLOCKED) {
1418252ca428SRobert Watson 		INP_INFO_WUNLOCK(&V_tcbinfo);
1419252ca428SRobert Watson 		ti_locked = TI_UNLOCKED;
1420fa046d87SRobert Watson 	}
1421fa046d87SRobert Watson #ifdef INVARIANTS
1422fa046d87SRobert Watson 	else {
1423fa046d87SRobert Watson 		KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropunlock "
1424fa046d87SRobert Watson 		    "ti_locked: %d", __func__, ti_locked));
1425fa046d87SRobert Watson 		INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1426fa046d87SRobert Watson 	}
1427fa046d87SRobert Watson #endif
1428252ca428SRobert Watson 
14299fa198beSAndre Oppermann 	if (inp != NULL)
14308501a69cSRobert Watson 		INP_WUNLOCK(inp);
1431014ea782SRobert Watson 
1432302ce8d6SAndre Oppermann drop:
1433603724d3SBjoern A. Zeeb 	INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1434a160e630SAndre Oppermann 	if (s != NULL)
1435a160e630SAndre Oppermann 		free(s, M_TCPLOG);
1436302ce8d6SAndre Oppermann 	if (m != NULL)
1437302ce8d6SAndre Oppermann 		m_freem(m);
14388f5a8818SKevin Lo 	return (IPPROTO_DONE);
1439302ce8d6SAndre Oppermann }
1440302ce8d6SAndre Oppermann 
1441679d9708SAndre Oppermann static void
1442302ce8d6SAndre Oppermann tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so,
1443252ca428SRobert Watson     struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos,
1444252ca428SRobert Watson     int ti_locked)
1445302ce8d6SAndre Oppermann {
1446302ce8d6SAndre Oppermann 	int thflags, acked, ourfinisacked, needoutput = 0;
1447302ce8d6SAndre Oppermann 	int rstreason, todrop, win;
1448302ce8d6SAndre Oppermann 	u_long tiwin;
144907dacf03SAndre Oppermann 	char *s;
145007dacf03SAndre Oppermann 	struct in_conninfo *inc;
1451c11a15bfSGleb Smirnoff 	struct mbuf *mfree;
1452302ce8d6SAndre Oppermann 	struct tcpopt to;
1453302ce8d6SAndre Oppermann 
145414739780SMaxim Konovalov #ifdef TCPDEBUG
145514739780SMaxim Konovalov 	/*
145614739780SMaxim Konovalov 	 * The size of tcp_saveipgen must be the size of the max ip header,
145714739780SMaxim Konovalov 	 * now IPv6.
145814739780SMaxim Konovalov 	 */
145914739780SMaxim Konovalov 	u_char tcp_saveipgen[IP6_HDR_LEN];
146014739780SMaxim Konovalov 	struct tcphdr tcp_savetcp;
146114739780SMaxim Konovalov 	short ostate = 0;
146214739780SMaxim Konovalov #endif
1463302ce8d6SAndre Oppermann 	thflags = th->th_flags;
146407dacf03SAndre Oppermann 	inc = &tp->t_inpcb->inp_inc;
1465d64a46eaSLawrence Stewart 	tp->sackhint.last_sack_ack = 0;
1466302ce8d6SAndre Oppermann 
1467252ca428SRobert Watson 	/*
1468252ca428SRobert Watson 	 * If this is either a state-changing packet or current state isn't
1469252ca428SRobert Watson 	 * established, we require a write lock on tcbinfo.  Otherwise, we
14700989f56cSRobert Watson 	 * allow the tcbinfo to be in either alocked or unlocked, as the
14710989f56cSRobert Watson 	 * caller may have unnecessarily acquired a write lock due to a race.
1472252ca428SRobert Watson 	 */
1473252ca428SRobert Watson 	if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 ||
1474252ca428SRobert Watson 	    tp->t_state != TCPS_ESTABLISHED) {
1475252ca428SRobert Watson 		KASSERT(ti_locked == TI_WLOCKED, ("%s ti_locked %d for "
1476252ca428SRobert Watson 		    "SYN/FIN/RST/!EST", __func__, ti_locked));
1477603724d3SBjoern A. Zeeb 		INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1478252ca428SRobert Watson 	} else {
1479252ca428SRobert Watson #ifdef INVARIANTS
1480fa046d87SRobert Watson 		if (ti_locked == TI_WLOCKED)
1481252ca428SRobert Watson 			INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1482fa046d87SRobert Watson 		else {
1483fa046d87SRobert Watson 			KASSERT(ti_locked == TI_UNLOCKED, ("%s: EST "
1484fa046d87SRobert Watson 			    "ti_locked: %d", __func__, ti_locked));
1485fa046d87SRobert Watson 			INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1486fa046d87SRobert Watson 		}
1487252ca428SRobert Watson #endif
1488252ca428SRobert Watson 	}
14898501a69cSRobert Watson 	INP_WLOCK_ASSERT(tp->t_inpcb);
1490679d9708SAndre Oppermann 	KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN",
1491679d9708SAndre Oppermann 	    __func__));
1492679d9708SAndre Oppermann 	KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT",
1493679d9708SAndre Oppermann 	    __func__));
1494df8bae1dSRodney W. Grimes 
1495df8bae1dSRodney W. Grimes 	/*
1496df8bae1dSRodney W. Grimes 	 * Segment received on connection.
1497df8bae1dSRodney W. Grimes 	 * Reset idle time and keep-alive timer.
1498e8949f74SAndre Oppermann 	 * XXX: This should be done after segment
1499e8949f74SAndre Oppermann 	 * validation to ignore broken/spoofed segs.
1500df8bae1dSRodney W. Grimes 	 */
15019b8b58e0SJonathan Lemon 	tp->t_rcvtime = ticks;
15027ff19458SPaul Traina 	if (TCPS_HAVEESTABLISHED(tp->t_state))
15039077f387SGleb Smirnoff 		tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
1504df8bae1dSRodney W. Grimes 
1505df8bae1dSRodney W. Grimes 	/*
1506464fcfbcSAndre Oppermann 	 * Unscale the window into a 32-bit value.
1507e8949f74SAndre Oppermann 	 * For the SYN_SENT state the scale is zero.
1508464fcfbcSAndre Oppermann 	 */
1509464fcfbcSAndre Oppermann 	tiwin = th->th_win << tp->snd_scale;
1510464fcfbcSAndre Oppermann 
1511464fcfbcSAndre Oppermann 	/*
1512f2512ba1SRui Paulo 	 * TCP ECN processing.
1513f2512ba1SRui Paulo 	 */
1514f2512ba1SRui Paulo 	if (tp->t_flags & TF_ECN_PERMIT) {
15159c251892SRui Paulo 		if (thflags & TH_CWR)
15169c251892SRui Paulo 			tp->t_flags &= ~TF_ECN_SND_ECE;
1517f2512ba1SRui Paulo 		switch (iptos & IPTOS_ECN_MASK) {
1518f2512ba1SRui Paulo 		case IPTOS_ECN_CE:
1519f2512ba1SRui Paulo 			tp->t_flags |= TF_ECN_SND_ECE;
152078b50714SRobert Watson 			TCPSTAT_INC(tcps_ecn_ce);
1521f2512ba1SRui Paulo 			break;
1522f2512ba1SRui Paulo 		case IPTOS_ECN_ECT0:
152378b50714SRobert Watson 			TCPSTAT_INC(tcps_ecn_ect0);
1524f2512ba1SRui Paulo 			break;
1525f2512ba1SRui Paulo 		case IPTOS_ECN_ECT1:
152678b50714SRobert Watson 			TCPSTAT_INC(tcps_ecn_ect1);
1527f2512ba1SRui Paulo 			break;
1528f2512ba1SRui Paulo 		}
1529dbc42409SLawrence Stewart 		/* Congestion experienced. */
1530dbc42409SLawrence Stewart 		if (thflags & TH_ECE) {
1531dbc42409SLawrence Stewart 			cc_cong_signal(tp, th, CC_ECN);
1532f2512ba1SRui Paulo 		}
1533f2512ba1SRui Paulo 	}
1534f2512ba1SRui Paulo 
1535f2512ba1SRui Paulo 	/*
1536f72167f4SAndre Oppermann 	 * Parse options on any incoming segment.
1537f72167f4SAndre Oppermann 	 */
1538302ce8d6SAndre Oppermann 	tcp_dooptions(&to, (u_char *)(th + 1),
1539302ce8d6SAndre Oppermann 	    (th->th_off << 2) - sizeof(struct tcphdr),
1540302ce8d6SAndre Oppermann 	    (thflags & TH_SYN) ? TO_SYN : 0);
1541f72167f4SAndre Oppermann 
1542f72167f4SAndre Oppermann 	/*
1543f72167f4SAndre Oppermann 	 * If echoed timestamp is later than the current time,
1544bf6d304aSAndre Oppermann 	 * fall back to non RFC1323 RTT calculation.  Normalize
1545bf6d304aSAndre Oppermann 	 * timestamp if syncookies were used when this connection
1546bf6d304aSAndre Oppermann 	 * was established.
1547f72167f4SAndre Oppermann 	 */
1548bf6d304aSAndre Oppermann 	if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) {
1549e16fa5caSJohn-Mark Gurney 		to.to_tsecr -= tp->ts_offset;
1550d8951c8aSBjoern A. Zeeb 		if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks()))
1551f72167f4SAndre Oppermann 			to.to_tsecr = 0;
1552bf6d304aSAndre Oppermann 	}
155307dacf03SAndre Oppermann 	/*
155407dacf03SAndre Oppermann 	 * If timestamps were negotiated during SYN/ACK they should
155507dacf03SAndre Oppermann 	 * appear on every segment during this session and vice versa.
155607dacf03SAndre Oppermann 	 */
155707dacf03SAndre Oppermann 	if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) {
155807dacf03SAndre Oppermann 		if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
155907dacf03SAndre Oppermann 			log(LOG_DEBUG, "%s; %s: Timestamp missing, "
156007dacf03SAndre Oppermann 			    "no action\n", s, __func__);
156107dacf03SAndre Oppermann 			free(s, M_TCPLOG);
156207dacf03SAndre Oppermann 		}
156307dacf03SAndre Oppermann 	}
156407dacf03SAndre Oppermann 	if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) {
156507dacf03SAndre Oppermann 		if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
156607dacf03SAndre Oppermann 			log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
156707dacf03SAndre Oppermann 			    "no action\n", s, __func__);
156807dacf03SAndre Oppermann 			free(s, M_TCPLOG);
156907dacf03SAndre Oppermann 		}
157007dacf03SAndre Oppermann 	}
1571f72167f4SAndre Oppermann 
1572f72167f4SAndre Oppermann 	/*
157397d8d152SAndre Oppermann 	 * Process options only when we get SYN/ACK back. The SYN case
157497d8d152SAndre Oppermann 	 * for incoming connections is handled in tcp_syncache.
15755396d0f8SAndre Oppermann 	 * According to RFC1323 the window field in a SYN (i.e., a <SYN>
15765396d0f8SAndre Oppermann 	 * or <SYN,ACK>) segment itself is never scaled.
157797d8d152SAndre Oppermann 	 * XXX this is traditional behavior, may need to be cleaned up.
1578df8bae1dSRodney W. Grimes 	 */
15790a389eabSSimon L. B. Nielsen 	if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
1580464fcfbcSAndre Oppermann 		if ((to.to_flags & TOF_SCALE) &&
1581464fcfbcSAndre Oppermann 		    (tp->t_flags & TF_REQ_SCALE)) {
1582be2ac88cSJonathan Lemon 			tp->t_flags |= TF_RCVD_SCALE;
158302a1a643SAndre Oppermann 			tp->snd_scale = to.to_wscale;
1584be2ac88cSJonathan Lemon 		}
15855396d0f8SAndre Oppermann 		/*
15865396d0f8SAndre Oppermann 		 * Initial send window.  It will be updated with
15875396d0f8SAndre Oppermann 		 * the next incoming segment to the scaled value.
15885396d0f8SAndre Oppermann 		 */
15895396d0f8SAndre Oppermann 		tp->snd_wnd = th->th_win;
1590be2ac88cSJonathan Lemon 		if (to.to_flags & TOF_TS) {
1591be2ac88cSJonathan Lemon 			tp->t_flags |= TF_RCVD_TSTMP;
1592be2ac88cSJonathan Lemon 			tp->ts_recent = to.to_tsval;
1593d8951c8aSBjoern A. Zeeb 			tp->ts_recent_age = tcp_ts_getticks();
1594be2ac88cSJonathan Lemon 		}
1595be2ac88cSJonathan Lemon 		if (to.to_flags & TOF_MSS)
1596be2ac88cSJonathan Lemon 			tcp_mss(tp, to.to_mss);
15973529149eSAndre Oppermann 		if ((tp->t_flags & TF_SACK_PERMIT) &&
15983529149eSAndre Oppermann 		    (to.to_flags & TOF_SACKPERM) == 0)
15993529149eSAndre Oppermann 			tp->t_flags &= ~TF_SACK_PERMIT;
16006d90faf3SPaul Saab 	}
16016d90faf3SPaul Saab 
1602df8bae1dSRodney W. Grimes 	/*
1603df8bae1dSRodney W. Grimes 	 * Header prediction: check for the two common cases
1604df8bae1dSRodney W. Grimes 	 * of a uni-directional data xfer.  If the packet has
1605df8bae1dSRodney W. Grimes 	 * no control flags, is in-sequence, the window didn't
1606df8bae1dSRodney W. Grimes 	 * change and we're not retransmitting, it's a
1607df8bae1dSRodney W. Grimes 	 * candidate.  If the length is zero and the ack moved
1608df8bae1dSRodney W. Grimes 	 * forward, we're the sender side of the xfer.  Just
1609df8bae1dSRodney W. Grimes 	 * free the data acked & wake any higher level process
1610df8bae1dSRodney W. Grimes 	 * that was blocked waiting for space.  If the length
1611df8bae1dSRodney W. Grimes 	 * is non-zero and the ack didn't move, we're the
1612df8bae1dSRodney W. Grimes 	 * receiver side.  If we're getting packets in-order
1613df8bae1dSRodney W. Grimes 	 * (the reassembly queue is empty), add the data to
1614df8bae1dSRodney W. Grimes 	 * the socket buffer and note that we need a delayed ack.
1615a0292f23SGarrett Wollman 	 * Make sure that the hidden state-flags are also off.
1616c5ad39b9SAndre Oppermann 	 * Since we check for TCPS_ESTABLISHED first, it can only
1617a0292f23SGarrett Wollman 	 * be TH_NEEDSYN.
1618df8bae1dSRodney W. Grimes 	 */
1619df8bae1dSRodney W. Grimes 	if (tp->t_state == TCPS_ESTABLISHED &&
1620c5ad39b9SAndre Oppermann 	    th->th_seq == tp->rcv_nxt &&
1621fb59c426SYoshinobu Inoue 	    (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
1622c5ad39b9SAndre Oppermann 	    tp->snd_nxt == tp->snd_max &&
1623c5ad39b9SAndre Oppermann 	    tiwin && tiwin == tp->snd_wnd &&
1624a0292f23SGarrett Wollman 	    ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
1625e407b67bSGleb Smirnoff 	    tp->t_segq == NULL && ((to.to_flags & TOF_TS) == 0 ||
1626c5ad39b9SAndre Oppermann 	     TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) {
1627df8bae1dSRodney W. Grimes 
1628df8bae1dSRodney W. Grimes 		/*
1629df8bae1dSRodney W. Grimes 		 * If last ACK falls within this segment's sequence numbers,
1630df8bae1dSRodney W. Grimes 		 * record the timestamp.
1631a0292f23SGarrett Wollman 		 * NOTE that the test is modified according to the latest
1632a0292f23SGarrett Wollman 		 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1633df8bae1dSRodney W. Grimes 		 */
1634be2ac88cSJonathan Lemon 		if ((to.to_flags & TOF_TS) != 0 &&
1635fb59c426SYoshinobu Inoue 		    SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1636d8951c8aSBjoern A. Zeeb 			tp->ts_recent_age = tcp_ts_getticks();
1637a0292f23SGarrett Wollman 			tp->ts_recent = to.to_tsval;
1638df8bae1dSRodney W. Grimes 		}
1639df8bae1dSRodney W. Grimes 
1640fb59c426SYoshinobu Inoue 		if (tlen == 0) {
1641fb59c426SYoshinobu Inoue 			if (SEQ_GT(th->th_ack, tp->snd_una) &&
1642fb59c426SYoshinobu Inoue 			    SEQ_LEQ(th->th_ack, tp->snd_max) &&
1643dbc42409SLawrence Stewart 			    !IN_RECOVERY(tp->t_flags) &&
1644fc30a251SAndre Oppermann 			    (to.to_flags & TOF_SACK) == 0 &&
1645dbc42409SLawrence Stewart 			    TAILQ_EMPTY(&tp->snd_holes)) {
1646df8bae1dSRodney W. Grimes 				/*
1647e8949f74SAndre Oppermann 				 * This is a pure ack for outstanding data.
1648df8bae1dSRodney W. Grimes 				 */
1649fa046d87SRobert Watson 				if (ti_locked == TI_WLOCKED)
1650252ca428SRobert Watson 					INP_INFO_WUNLOCK(&V_tcbinfo);
1651252ca428SRobert Watson 				ti_locked = TI_UNLOCKED;
1652252ca428SRobert Watson 
165378b50714SRobert Watson 				TCPSTAT_INC(tcps_predack);
1654252ca428SRobert Watson 
16559b8b58e0SJonathan Lemon 				/*
1656e8949f74SAndre Oppermann 				 * "bad retransmit" recovery.
16579b8b58e0SJonathan Lemon 				 */
16589b8b58e0SJonathan Lemon 				if (tp->t_rxtshift == 1 &&
1659672dc4aeSJohn Baldwin 				    tp->t_flags & TF_PREVVALID &&
16606dfb8b31SJohn Baldwin 				    (int)(ticks - tp->t_badrxtwin) < 0) {
1661dbc42409SLawrence Stewart 					cc_cong_signal(tp, th, CC_RTO_ERR);
16629b8b58e0SJonathan Lemon 				}
1663fa55172bSMatthew Dillon 
1664fa55172bSMatthew Dillon 				/*
1665fa55172bSMatthew Dillon 				 * Recalculate the transmit timer / rtt.
1666fa55172bSMatthew Dillon 				 *
1667fa55172bSMatthew Dillon 				 * Some boxes send broken timestamp replies
1668fa55172bSMatthew Dillon 				 * during the SYN+ACK phase, ignore
1669fa55172bSMatthew Dillon 				 * timestamps of 0 or we could calculate a
1670fa55172bSMatthew Dillon 				 * huge RTT and blow up the retransmit timer.
1671fa55172bSMatthew Dillon 				 */
1672fa55172bSMatthew Dillon 				if ((to.to_flags & TOF_TS) != 0 &&
1673fa55172bSMatthew Dillon 				    to.to_tsecr) {
1674d8951c8aSBjoern A. Zeeb 					u_int t;
1675d8951c8aSBjoern A. Zeeb 
1676d8951c8aSBjoern A. Zeeb 					t = tcp_ts_getticks() - to.to_tsecr;
1677d8951c8aSBjoern A. Zeeb 					if (!tp->t_rttlow || tp->t_rttlow > t)
1678d8951c8aSBjoern A. Zeeb 						tp->t_rttlow = t;
1679a0292f23SGarrett Wollman 					tcp_xmit_timer(tp,
1680d8951c8aSBjoern A. Zeeb 					    TCP_TS_TO_TICKS(t) + 1);
1681fa55172bSMatthew Dillon 				} else if (tp->t_rtttime &&
1682fa55172bSMatthew Dillon 				    SEQ_GT(th->th_ack, tp->t_rtseq)) {
1683eaf80179SAndre Oppermann 					if (!tp->t_rttlow ||
1684eaf80179SAndre Oppermann 					    tp->t_rttlow > ticks - tp->t_rtttime)
1685eaf80179SAndre Oppermann 						tp->t_rttlow = ticks - tp->t_rtttime;
1686c068736aSJeffrey Hsu 					tcp_xmit_timer(tp,
1687c068736aSJeffrey Hsu 							ticks - tp->t_rtttime);
1688fa55172bSMatthew Dillon 				}
1689dbc42409SLawrence Stewart 				acked = BYTES_THIS_ACK(tp, th);
169039bc9de5SLawrence Stewart 
169139bc9de5SLawrence Stewart 				/* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */
169239bc9de5SLawrence Stewart 				hhook_run_tcp_est_in(tp, th, &to);
169339bc9de5SLawrence Stewart 
169478b50714SRobert Watson 				TCPSTAT_INC(tcps_rcvackpack);
169578b50714SRobert Watson 				TCPSTAT_ADD(tcps_rcvackbyte, acked);
1696df8bae1dSRodney W. Grimes 				sbdrop(&so->so_snd, acked);
16979d11646dSJeffrey Hsu 				if (SEQ_GT(tp->snd_una, tp->snd_recover) &&
16989d11646dSJeffrey Hsu 				    SEQ_LEQ(th->th_ack, tp->snd_recover))
16999d11646dSJeffrey Hsu 					tp->snd_recover = th->th_ack - 1;
1700dbc42409SLawrence Stewart 
1701dbc42409SLawrence Stewart 				/*
1702dbc42409SLawrence Stewart 				 * Let the congestion control algorithm update
1703dbc42409SLawrence Stewart 				 * congestion control related information. This
1704dbc42409SLawrence Stewart 				 * typically means increasing the congestion
1705dbc42409SLawrence Stewart 				 * window.
1706dbc42409SLawrence Stewart 				 */
1707dbc42409SLawrence Stewart 				cc_ack_received(tp, th, CC_ACK);
1708dbc42409SLawrence Stewart 
17099d11646dSJeffrey Hsu 				tp->snd_una = th->th_ack;
17101645d090SJeff Roberson 				/*
1711e8949f74SAndre Oppermann 				 * Pull snd_wl2 up to prevent seq wrap relative
17121645d090SJeff Roberson 				 * to th_ack.
17131645d090SJeff Roberson 				 */
1714cb942153SJeffrey Hsu 				tp->snd_wl2 = th->th_ack;
1715b5addd85SJeffrey Hsu 				tp->t_dupacks = 0;
1716df8bae1dSRodney W. Grimes 				m_freem(m);
1717e8949f74SAndre Oppermann 				ND6_HINT(tp); /* Some progress has been made. */
1718df8bae1dSRodney W. Grimes 
1719df8bae1dSRodney W. Grimes 				/*
1720df8bae1dSRodney W. Grimes 				 * If all outstanding data are acked, stop
1721df8bae1dSRodney W. Grimes 				 * retransmit timer, otherwise restart timer
1722df8bae1dSRodney W. Grimes 				 * using current (possibly backed-off) value.
1723df8bae1dSRodney W. Grimes 				 * If process is waiting for space,
1724df8bae1dSRodney W. Grimes 				 * wakeup/selwakeup/signal.  If data
1725df8bae1dSRodney W. Grimes 				 * are ready to send, let tcp_output
1726df8bae1dSRodney W. Grimes 				 * decide between more output or persist.
1727e8949f74SAndre Oppermann 				 */
17283c653157SHartmut Brandt #ifdef TCPDEBUG
17293c653157SHartmut Brandt 				if (so->so_options & SO_DEBUG)
17303c653157SHartmut Brandt 					tcp_trace(TA_INPUT, ostate, tp,
17313c653157SHartmut Brandt 					    (void *)tcp_saveipgen,
17323c653157SHartmut Brandt 					    &tcp_savetcp, 0);
17333c653157SHartmut Brandt #endif
1734df8bae1dSRodney W. Grimes 				if (tp->snd_una == tp->snd_max)
1735b8152ba7SAndre Oppermann 					tcp_timer_activate(tp, TT_REXMT, 0);
1736b8152ba7SAndre Oppermann 				else if (!tcp_timer_active(tp, TT_PERSIST))
1737b8152ba7SAndre Oppermann 					tcp_timer_activate(tp, TT_REXMT,
1738b8152ba7SAndre Oppermann 						      tp->t_rxtcur);
1739df8bae1dSRodney W. Grimes 				sowwakeup(so);
1740df8bae1dSRodney W. Grimes 				if (so->so_snd.sb_cc)
1741df8bae1dSRodney W. Grimes 					(void) tcp_output(tp);
1742a14c749fSJonathan Lemon 				goto check_delack;
1743df8bae1dSRodney W. Grimes 			}
1744fb59c426SYoshinobu Inoue 		} else if (th->th_ack == tp->snd_una &&
1745fb59c426SYoshinobu Inoue 		    tlen <= sbspace(&so->so_rcv)) {
17466741ecf5SAndre Oppermann 			int newsize = 0;	/* automatic sockbuf scaling */
17476741ecf5SAndre Oppermann 
1748df8bae1dSRodney W. Grimes 			/*
1749252ca428SRobert Watson 			 * This is a pure, in-sequence data packet with
1750252ca428SRobert Watson 			 * nothing on the reassembly queue and we have enough
1751252ca428SRobert Watson 			 * buffer space to take it.
1752df8bae1dSRodney W. Grimes 			 */
1753fa046d87SRobert Watson 			if (ti_locked == TI_WLOCKED)
1754252ca428SRobert Watson 				INP_INFO_WUNLOCK(&V_tcbinfo);
1755252ca428SRobert Watson 			ti_locked = TI_UNLOCKED;
1756252ca428SRobert Watson 
17576d90faf3SPaul Saab 			/* Clean receiver SACK report if present */
17583529149eSAndre Oppermann 			if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks)
17596d90faf3SPaul Saab 				tcp_clean_sackreport(tp);
176078b50714SRobert Watson 			TCPSTAT_INC(tcps_preddat);
1761fb59c426SYoshinobu Inoue 			tp->rcv_nxt += tlen;
17621645d090SJeff Roberson 			/*
17631645d090SJeff Roberson 			 * Pull snd_wl1 up to prevent seq wrap relative to
17641645d090SJeff Roberson 			 * th_seq.
17651645d090SJeff Roberson 			 */
176660ee3bb2SAndre Oppermann 			tp->snd_wl1 = th->th_seq;
17671645d090SJeff Roberson 			/*
17681645d090SJeff Roberson 			 * Pull rcv_up up to prevent seq wrap relative to
17691645d090SJeff Roberson 			 * rcv_nxt.
17701645d090SJeff Roberson 			 */
17711645d090SJeff Roberson 			tp->rcv_up = tp->rcv_nxt;
177278b50714SRobert Watson 			TCPSTAT_INC(tcps_rcvpack);
177378b50714SRobert Watson 			TCPSTAT_ADD(tcps_rcvbyte, tlen);
1774e8949f74SAndre Oppermann 			ND6_HINT(tp);	/* Some progress has been made */
17753c653157SHartmut Brandt #ifdef TCPDEBUG
17763c653157SHartmut Brandt 			if (so->so_options & SO_DEBUG)
17773c653157SHartmut Brandt 				tcp_trace(TA_INPUT, ostate, tp,
17783c653157SHartmut Brandt 				    (void *)tcp_saveipgen, &tcp_savetcp, 0);
17793c653157SHartmut Brandt #endif
17806741ecf5SAndre Oppermann 		/*
17816741ecf5SAndre Oppermann 		 * Automatic sizing of receive socket buffer.  Often the send
17826741ecf5SAndre Oppermann 		 * buffer size is not optimally adjusted to the actual network
17836741ecf5SAndre Oppermann 		 * conditions at hand (delay bandwidth product).  Setting the
17846741ecf5SAndre Oppermann 		 * buffer size too small limits throughput on links with high
17856741ecf5SAndre Oppermann 		 * bandwidth and high delay (eg. trans-continental/oceanic links).
17866741ecf5SAndre Oppermann 		 *
17876741ecf5SAndre Oppermann 		 * On the receive side the socket buffer memory is only rarely
17886741ecf5SAndre Oppermann 		 * used to any significant extent.  This allows us to be much
17896741ecf5SAndre Oppermann 		 * more aggressive in scaling the receive socket buffer.  For
17906741ecf5SAndre Oppermann 		 * the case that the buffer space is actually used to a large
17916741ecf5SAndre Oppermann 		 * extent and we run out of kernel memory we can simply drop
17926741ecf5SAndre Oppermann 		 * the new segments; TCP on the sender will just retransmit it
17936741ecf5SAndre Oppermann 		 * later.  Setting the buffer size too big may only consume too
17946741ecf5SAndre Oppermann 		 * much kernel memory if the application doesn't read() from
17956741ecf5SAndre Oppermann 		 * the socket or packet loss or reordering makes use of the
17966741ecf5SAndre Oppermann 		 * reassembly queue.
17976741ecf5SAndre Oppermann 		 *
17986741ecf5SAndre Oppermann 		 * The criteria to step up the receive buffer one notch are:
1799f7469d3eSHiren Panchasara 		 *  1. Application has not set receive buffer size with
1800f7469d3eSHiren Panchasara 		 *     SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE.
1801f7469d3eSHiren Panchasara 		 *  2. the number of bytes received during the time it takes
18026741ecf5SAndre Oppermann 		 *     one timestamp to be reflected back to us (the RTT);
1803f7469d3eSHiren Panchasara 		 *  3. received bytes per RTT is within seven eighth of the
18046741ecf5SAndre Oppermann 		 *     current socket buffer size;
1805f7469d3eSHiren Panchasara 		 *  4. receive buffer size has not hit maximal automatic size;
18066741ecf5SAndre Oppermann 		 *
18076741ecf5SAndre Oppermann 		 * This algorithm does one step per RTT at most and only if
18086741ecf5SAndre Oppermann 		 * we receive a bulk stream w/o packet losses or reorderings.
18096741ecf5SAndre Oppermann 		 * Shrinking the buffer during idle times is not necessary as
18106741ecf5SAndre Oppermann 		 * it doesn't consume any memory when idle.
18116741ecf5SAndre Oppermann 		 *
18126741ecf5SAndre Oppermann 		 * TODO: Only step up if the application is actually serving
18136741ecf5SAndre Oppermann 		 * the buffer to better manage the socket buffer resources.
1814df8bae1dSRodney W. Grimes 		 */
1815603724d3SBjoern A. Zeeb 			if (V_tcp_do_autorcvbuf &&
18166741ecf5SAndre Oppermann 			    to.to_tsecr &&
18176741ecf5SAndre Oppermann 			    (so->so_rcv.sb_flags & SB_AUTOSIZE)) {
18188502ec25SAndre Oppermann 				if (TSTMP_GT(to.to_tsecr, tp->rfbuf_ts) &&
18196741ecf5SAndre Oppermann 				    to.to_tsecr - tp->rfbuf_ts < hz) {
18206741ecf5SAndre Oppermann 					if (tp->rfbuf_cnt >
18216741ecf5SAndre Oppermann 					    (so->so_rcv.sb_hiwat / 8 * 7) &&
18226741ecf5SAndre Oppermann 					    so->so_rcv.sb_hiwat <
1823603724d3SBjoern A. Zeeb 					    V_tcp_autorcvbuf_max) {
18246741ecf5SAndre Oppermann 						newsize =
18256741ecf5SAndre Oppermann 						    min(so->so_rcv.sb_hiwat +
1826603724d3SBjoern A. Zeeb 						    V_tcp_autorcvbuf_inc,
1827603724d3SBjoern A. Zeeb 						    V_tcp_autorcvbuf_max);
18286741ecf5SAndre Oppermann 					}
18296741ecf5SAndre Oppermann 					/* Start over with next RTT. */
18306741ecf5SAndre Oppermann 					tp->rfbuf_ts = 0;
18316741ecf5SAndre Oppermann 					tp->rfbuf_cnt = 0;
18326741ecf5SAndre Oppermann 				} else
18336741ecf5SAndre Oppermann 					tp->rfbuf_cnt += tlen;	/* add up */
18346741ecf5SAndre Oppermann 			}
18356741ecf5SAndre Oppermann 
18366741ecf5SAndre Oppermann 			/* Add data to socket buffer. */
18371e4d7da7SRobert Watson 			SOCKBUF_LOCK(&so->so_rcv);
1838c0b99ffaSRobert Watson 			if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
1839c1c36a2cSMike Silbersack 				m_freem(m);
1840c1c36a2cSMike Silbersack 			} else {
18416741ecf5SAndre Oppermann 				/*
18426741ecf5SAndre Oppermann 				 * Set new socket buffer size.
18436741ecf5SAndre Oppermann 				 * Give up when limit is reached.
18446741ecf5SAndre Oppermann 				 */
18456741ecf5SAndre Oppermann 				if (newsize)
18466741ecf5SAndre Oppermann 					if (!sbreserve_locked(&so->so_rcv,
18476c8286e4SRobert Watson 					    newsize, so, NULL))
18486741ecf5SAndre Oppermann 						so->so_rcv.sb_flags &= ~SB_AUTOSIZE;
1849fb59c426SYoshinobu Inoue 				m_adj(m, drop_hdrlen);	/* delayed header drop */
18501e4d7da7SRobert Watson 				sbappendstream_locked(&so->so_rcv, m);
1851c1c36a2cSMike Silbersack 			}
1852e8949f74SAndre Oppermann 			/* NB: sorwakeup_locked() does an implicit unlock. */
18531e4d7da7SRobert Watson 			sorwakeup_locked(so);
1854c1e5a6e5SAndre Oppermann 			if (DELAY_ACK(tp, tlen)) {
18553bfd6421SJonathan Lemon 				tp->t_flags |= TF_DELACK;
1856f498eeeeSDavid Greenman 			} else {
1857e612a582SDavid Greenman 				tp->t_flags |= TF_ACKNOW;
1858e612a582SDavid Greenman 				tcp_output(tp);
1859e612a582SDavid Greenman 			}
1860a14c749fSJonathan Lemon 			goto check_delack;
1861df8bae1dSRodney W. Grimes 		}
1862df8bae1dSRodney W. Grimes 	}
1863df8bae1dSRodney W. Grimes 
1864df8bae1dSRodney W. Grimes 	/*
1865df8bae1dSRodney W. Grimes 	 * Calculate amount of space in receive window,
1866df8bae1dSRodney W. Grimes 	 * and then do TCP input processing.
1867df8bae1dSRodney W. Grimes 	 * Receive window is amount of space in rcv queue,
1868df8bae1dSRodney W. Grimes 	 * but not less than advertised window.
1869df8bae1dSRodney W. Grimes 	 */
1870df8bae1dSRodney W. Grimes 	win = sbspace(&so->so_rcv);
1871df8bae1dSRodney W. Grimes 	if (win < 0)
1872df8bae1dSRodney W. Grimes 		win = 0;
187366e39adcSJohn Polstra 	tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
1874df8bae1dSRodney W. Grimes 
18756741ecf5SAndre Oppermann 	/* Reset receive buffer auto scaling when not in bulk receive mode. */
18766741ecf5SAndre Oppermann 	tp->rfbuf_ts = 0;
18776741ecf5SAndre Oppermann 	tp->rfbuf_cnt = 0;
18786741ecf5SAndre Oppermann 
1879df8bae1dSRodney W. Grimes 	switch (tp->t_state) {
1880df8bae1dSRodney W. Grimes 
1881df8bae1dSRodney W. Grimes 	/*
1882764d8cefSBill Fenner 	 * If the state is SYN_RECEIVED:
1883764d8cefSBill Fenner 	 *	if seg contains an ACK, but not for our SYN/ACK, send a RST.
1884764d8cefSBill Fenner 	 */
1885764d8cefSBill Fenner 	case TCPS_SYN_RECEIVED:
1886fb59c426SYoshinobu Inoue 		if ((thflags & TH_ACK) &&
1887fb59c426SYoshinobu Inoue 		    (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1888a57815efSBosko Milekic 		     SEQ_GT(th->th_ack, tp->snd_max))) {
1889a57815efSBosko Milekic 				rstreason = BANDLIM_RST_OPENPORT;
1890a57815efSBosko Milekic 				goto dropwithreset;
1891a57815efSBosko Milekic 		}
1892764d8cefSBill Fenner 		break;
1893764d8cefSBill Fenner 
1894764d8cefSBill Fenner 	/*
1895df8bae1dSRodney W. Grimes 	 * If the state is SYN_SENT:
1896df8bae1dSRodney W. Grimes 	 *	if seg contains an ACK, but not for our SYN, drop the input.
1897df8bae1dSRodney W. Grimes 	 *	if seg contains a RST, then drop the connection.
1898df8bae1dSRodney W. Grimes 	 *	if seg does not contain SYN, then drop it.
1899df8bae1dSRodney W. Grimes 	 * Otherwise this is an acceptable SYN segment
1900df8bae1dSRodney W. Grimes 	 *	initialize tp->rcv_nxt and tp->irs
1901df8bae1dSRodney W. Grimes 	 *	if seg contains ack then advance tp->snd_una
1902f2512ba1SRui Paulo 	 *	if seg contains an ECE and ECN support is enabled, the stream
1903f2512ba1SRui Paulo 	 *	    is ECN capable.
1904df8bae1dSRodney W. Grimes 	 *	if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1905df8bae1dSRodney W. Grimes 	 *	arrange for segment to be acked (eventually)
1906df8bae1dSRodney W. Grimes 	 *	continue processing rest of data/controls, beginning with URG
1907df8bae1dSRodney W. Grimes 	 */
1908df8bae1dSRodney W. Grimes 	case TCPS_SYN_SENT:
1909fb59c426SYoshinobu Inoue 		if ((thflags & TH_ACK) &&
1910fb59c426SYoshinobu Inoue 		    (SEQ_LEQ(th->th_ack, tp->iss) ||
1911fb59c426SYoshinobu Inoue 		     SEQ_GT(th->th_ack, tp->snd_max))) {
1912a57815efSBosko Milekic 			rstreason = BANDLIM_UNLIMITED;
1913a0292f23SGarrett Wollman 			goto dropwithreset;
1914a0292f23SGarrett Wollman 		}
191557f60867SMark Johnston 		if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) {
1916d9fae5abSAndriy Gapon 			TCP_PROBE5(connect__refused, NULL, tp,
1917fa22ce15SAdrian Chadd 			    mtod(m, const char *), tp, th);
1918df8bae1dSRodney W. Grimes 			tp = tcp_drop(tp, ECONNREFUSED);
191957f60867SMark Johnston 		}
19200ca3f933SAndre Oppermann 		if (thflags & TH_RST)
1921df8bae1dSRodney W. Grimes 			goto drop;
19220ca3f933SAndre Oppermann 		if (!(thflags & TH_SYN))
1923df8bae1dSRodney W. Grimes 			goto drop;
1924464fcfbcSAndre Oppermann 
1925fb59c426SYoshinobu Inoue 		tp->irs = th->th_seq;
1926df8bae1dSRodney W. Grimes 		tcp_rcvseqinit(tp);
1927fb59c426SYoshinobu Inoue 		if (thflags & TH_ACK) {
192878b50714SRobert Watson 			TCPSTAT_INC(tcps_connects);
1929845799c1SAndras Olah 			soisconnected(so);
1930c488362eSRobert Watson #ifdef MAC
193130d239bcSRobert Watson 			mac_socketpeer_set_from_mbuf(m, so);
1932c488362eSRobert Watson #endif
1933845799c1SAndras Olah 			/* Do window scaling on this connection? */
1934845799c1SAndras Olah 			if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1935845799c1SAndras Olah 				(TF_RCVD_SCALE|TF_REQ_SCALE)) {
1936845799c1SAndras Olah 				tp->rcv_scale = tp->request_r_scale;
1937845799c1SAndras Olah 			}
1938766282cbSJohn Baldwin 			tp->rcv_adv += imin(tp->rcv_wnd,
1939766282cbSJohn Baldwin 			    TCP_MAXWIN << tp->rcv_scale);
1940a0292f23SGarrett Wollman 			tp->snd_una++;		/* SYN is acked */
1941a0292f23SGarrett Wollman 			/*
1942a0292f23SGarrett Wollman 			 * If there's data, delay ACK; if there's also a FIN
1943a0292f23SGarrett Wollman 			 * ACKNOW will be turned on later.
1944a0292f23SGarrett Wollman 			 */
1945c1e5a6e5SAndre Oppermann 			if (DELAY_ACK(tp, tlen) && tlen != 0)
1946b8152ba7SAndre Oppermann 				tcp_timer_activate(tp, TT_DELACK,
1947b8152ba7SAndre Oppermann 				    tcp_delacktime);
1948a0292f23SGarrett Wollman 			else
1949a0292f23SGarrett Wollman 				tp->t_flags |= TF_ACKNOW;
1950f2512ba1SRui Paulo 
1951603724d3SBjoern A. Zeeb 			if ((thflags & TH_ECE) && V_tcp_do_ecn) {
1952f2512ba1SRui Paulo 				tp->t_flags |= TF_ECN_PERMIT;
195378b50714SRobert Watson 				TCPSTAT_INC(tcps_ecn_shs);
1954f2512ba1SRui Paulo 			}
1955f2512ba1SRui Paulo 
1956a0292f23SGarrett Wollman 			/*
1957a0292f23SGarrett Wollman 			 * Received <SYN,ACK> in SYN_SENT[*] state.
1958a0292f23SGarrett Wollman 			 * Transitions:
1959a0292f23SGarrett Wollman 			 *	SYN_SENT  --> ESTABLISHED
1960a0292f23SGarrett Wollman 			 *	SYN_SENT* --> FIN_WAIT_1
1961a0292f23SGarrett Wollman 			 */
19629b8b58e0SJonathan Lemon 			tp->t_starttime = ticks;
1963a0292f23SGarrett Wollman 			if (tp->t_flags & TF_NEEDFIN) {
196457f60867SMark Johnston 				tcp_state_change(tp, TCPS_FIN_WAIT_1);
1965a0292f23SGarrett Wollman 				tp->t_flags &= ~TF_NEEDFIN;
1966fb59c426SYoshinobu Inoue 				thflags &= ~TH_SYN;
19677ff19458SPaul Traina 			} else {
196857f60867SMark Johnston 				tcp_state_change(tp, TCPS_ESTABLISHED);
1969d9fae5abSAndriy Gapon 				TCP_PROBE5(connect__established, NULL, tp,
1970fa22ce15SAdrian Chadd 				    mtod(m, const char *), tp, th);
1971dbc42409SLawrence Stewart 				cc_conn_init(tp);
19729077f387SGleb Smirnoff 				tcp_timer_activate(tp, TT_KEEP,
19739077f387SGleb Smirnoff 				    TP_KEEPIDLE(tp));
19747ff19458SPaul Traina 			}
1975a0292f23SGarrett Wollman 		} else {
1976a0292f23SGarrett Wollman 			/*
1977c068736aSJeffrey Hsu 			 * Received initial SYN in SYN-SENT[*] state =>
1978153edc50SHiren Panchasara 			 * simultaneous open.
1979c068736aSJeffrey Hsu 			 * If it succeeds, connection is * half-synchronized.
1980c068736aSJeffrey Hsu 			 * Otherwise, do 3-way handshake:
1981a0292f23SGarrett Wollman 			 *        SYN-SENT -> SYN-RECEIVED
1982a0292f23SGarrett Wollman 			 *        SYN-SENT* -> SYN-RECEIVED*
1983a0292f23SGarrett Wollman 			 */
19844b8e98d6SQing Li 			tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
1985b8152ba7SAndre Oppermann 			tcp_timer_activate(tp, TT_REXMT, 0);
198657f60867SMark Johnston 			tcp_state_change(tp, TCPS_SYN_RECEIVED);
1987a0292f23SGarrett Wollman 		}
1988df8bae1dSRodney W. Grimes 
1989252ca428SRobert Watson 		KASSERT(ti_locked == TI_WLOCKED, ("%s: trimthenstep6: "
1990252ca428SRobert Watson 		    "ti_locked %d", __func__, ti_locked));
1991252ca428SRobert Watson 		INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
19928501a69cSRobert Watson 		INP_WLOCK_ASSERT(tp->t_inpcb);
19937cfc6904SRobert Watson 
1994df8bae1dSRodney W. Grimes 		/*
1995fb59c426SYoshinobu Inoue 		 * Advance th->th_seq to correspond to first data byte.
1996df8bae1dSRodney W. Grimes 		 * If data, trim to stay within window,
1997df8bae1dSRodney W. Grimes 		 * dropping FIN if necessary.
1998df8bae1dSRodney W. Grimes 		 */
1999fb59c426SYoshinobu Inoue 		th->th_seq++;
2000fb59c426SYoshinobu Inoue 		if (tlen > tp->rcv_wnd) {
2001fb59c426SYoshinobu Inoue 			todrop = tlen - tp->rcv_wnd;
2002df8bae1dSRodney W. Grimes 			m_adj(m, -todrop);
2003fb59c426SYoshinobu Inoue 			tlen = tp->rcv_wnd;
2004fb59c426SYoshinobu Inoue 			thflags &= ~TH_FIN;
200578b50714SRobert Watson 			TCPSTAT_INC(tcps_rcvpackafterwin);
200678b50714SRobert Watson 			TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
2007df8bae1dSRodney W. Grimes 		}
2008fb59c426SYoshinobu Inoue 		tp->snd_wl1 = th->th_seq - 1;
2009fb59c426SYoshinobu Inoue 		tp->rcv_up = th->th_seq;
2010a0292f23SGarrett Wollman 		/*
2011a0292f23SGarrett Wollman 		 * Client side of transaction: already sent SYN and data.
2012a0292f23SGarrett Wollman 		 * If the remote host used T/TCP to validate the SYN,
2013a0292f23SGarrett Wollman 		 * our data will be ACK'd; if so, enter normal data segment
2014a0292f23SGarrett Wollman 		 * processing in the middle of step 5, ack processing.
2015a0292f23SGarrett Wollman 		 * Otherwise, goto step 6.
2016a0292f23SGarrett Wollman 		 */
2017fb59c426SYoshinobu Inoue 		if (thflags & TH_ACK)
2018a0292f23SGarrett Wollman 			goto process_ACK;
2019c068736aSJeffrey Hsu 
2020df8bae1dSRodney W. Grimes 		goto step6;
2021c068736aSJeffrey Hsu 
2022a0292f23SGarrett Wollman 	/*
2023a0292f23SGarrett Wollman 	 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
2024c94c54e4SAndre Oppermann 	 *      do normal processing.
2025a0292f23SGarrett Wollman 	 *
2026c94c54e4SAndre Oppermann 	 * NB: Leftover from RFC1644 T/TCP.  Cases to be reused later.
2027a0292f23SGarrett Wollman 	 */
2028a0292f23SGarrett Wollman 	case TCPS_LAST_ACK:
2029a0292f23SGarrett Wollman 	case TCPS_CLOSING:
2030a0292f23SGarrett Wollman 		break;  /* continue normal processing */
2031df8bae1dSRodney W. Grimes 	}
2032df8bae1dSRodney W. Grimes 
2033df8bae1dSRodney W. Grimes 	/*
2034df8bae1dSRodney W. Grimes 	 * States other than LISTEN or SYN_SENT.
203580ab7c0eSGarrett Wollman 	 * First check the RST flag and sequence number since reset segments
203680ab7c0eSGarrett Wollman 	 * are exempt from the timestamp and connection count tests.  This
203780ab7c0eSGarrett Wollman 	 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
203880ab7c0eSGarrett Wollman 	 * below which allowed reset segments in half the sequence space
203980ab7c0eSGarrett Wollman 	 * to fall though and be processed (which gives forged reset
204080ab7c0eSGarrett Wollman 	 * segments with a random sequence number a 50 percent chance of
204180ab7c0eSGarrett Wollman 	 * killing a connection).
204280ab7c0eSGarrett Wollman 	 * Then check timestamp, if present.
2043a0292f23SGarrett Wollman 	 * Then check the connection count, if present.
2044df8bae1dSRodney W. Grimes 	 * Then check that at least some bytes of segment are within
2045df8bae1dSRodney W. Grimes 	 * receive window.  If segment begins before rcv_nxt,
2046df8bae1dSRodney W. Grimes 	 * drop leading data (and SYN); if nothing left, just ack.
2047df8bae1dSRodney W. Grimes 	 *
204880ab7c0eSGarrett Wollman 	 *
204980ab7c0eSGarrett Wollman 	 * If the RST bit is set, check the sequence number to see
205080ab7c0eSGarrett Wollman 	 * if this is a valid reset segment.
205180ab7c0eSGarrett Wollman 	 * RFC 793 page 37:
205280ab7c0eSGarrett Wollman 	 *   In all states except SYN-SENT, all reset (RST) segments
205380ab7c0eSGarrett Wollman 	 *   are validated by checking their SEQ-fields.  A reset is
205480ab7c0eSGarrett Wollman 	 *   valid if its sequence number is in the window.
205580ab7c0eSGarrett Wollman 	 * Note: this does not take into account delayed ACKs, so
205680ab7c0eSGarrett Wollman 	 *   we should test against last_ack_sent instead of rcv_nxt.
20571a244a61SJonathan Lemon 	 *   The sequence number in the reset segment is normally an
20581a244a61SJonathan Lemon 	 *   echo of our outgoing acknowlegement numbers, but some hosts
20591a244a61SJonathan Lemon 	 *   send a reset with the sequence number at the rightmost edge
20601a244a61SJonathan Lemon 	 *   of our receive window, and we have to handle this case.
206180dd2a81SMike Silbersack 	 * Note 2: Paul Watson's paper "Slipping in the Window" has shown
206280dd2a81SMike Silbersack 	 *   that brute force RST attacks are possible.  To combat this,
206380dd2a81SMike Silbersack 	 *   we use a much stricter check while in the ESTABLISHED state,
206480dd2a81SMike Silbersack 	 *   only accepting RSTs where the sequence number is equal to
206580dd2a81SMike Silbersack 	 *   last_ack_sent.  In all other states (the states in which a
206680dd2a81SMike Silbersack 	 *   RST is more likely), the more permissive check is used.
20678e5c87f4SBjoern A. Zeeb 	 * If we have multiple segments in flight, the initial reset
206880ab7c0eSGarrett Wollman 	 * segment sequence numbers will be to the left of last_ack_sent,
206980ab7c0eSGarrett Wollman 	 * but they will eventually catch up.
207080ab7c0eSGarrett Wollman 	 * In any case, it never made sense to trim reset segments to
207180ab7c0eSGarrett Wollman 	 * fit the receive window since RFC 1122 says:
207280ab7c0eSGarrett Wollman 	 *   4.2.2.12  RST Segment: RFC-793 Section 3.4
207380ab7c0eSGarrett Wollman 	 *
207480ab7c0eSGarrett Wollman 	 *    A TCP SHOULD allow a received RST segment to include data.
207580ab7c0eSGarrett Wollman 	 *
207680ab7c0eSGarrett Wollman 	 *    DISCUSSION
207780ab7c0eSGarrett Wollman 	 *         It has been suggested that a RST segment could contain
207880ab7c0eSGarrett Wollman 	 *         ASCII text that encoded and explained the cause of the
207980ab7c0eSGarrett Wollman 	 *         RST.  No standard has yet been established for such
208080ab7c0eSGarrett Wollman 	 *         data.
208180ab7c0eSGarrett Wollman 	 *
208280ab7c0eSGarrett Wollman 	 * If the reset segment passes the sequence number test examine
208380ab7c0eSGarrett Wollman 	 * the state:
208480ab7c0eSGarrett Wollman 	 *    SYN_RECEIVED STATE:
208580ab7c0eSGarrett Wollman 	 *	If passive open, return to LISTEN state.
208680ab7c0eSGarrett Wollman 	 *	If active open, inform user that connection was refused.
2087745bab7fSDima Dorfman 	 *    ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES:
208880ab7c0eSGarrett Wollman 	 *	Inform user that connection was reset, and close tcb.
2089e9bd3a37SJonathan M. Bresler 	 *    CLOSING, LAST_ACK STATES:
209080ab7c0eSGarrett Wollman 	 *	Close the tcb.
2091e9bd3a37SJonathan M. Bresler 	 *    TIME_WAIT STATE:
209280ab7c0eSGarrett Wollman 	 *	Drop the segment - see Stevens, vol. 2, p. 964 and
209380ab7c0eSGarrett Wollman 	 *      RFC 1337.
209480ab7c0eSGarrett Wollman 	 */
2095fb59c426SYoshinobu Inoue 	if (thflags & TH_RST) {
209695ad8418SQing Li 		if (SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) &&
209795ad8418SQing Li 		    SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
209880ab7c0eSGarrett Wollman 			switch (tp->t_state) {
209980ab7c0eSGarrett Wollman 
210080ab7c0eSGarrett Wollman 			case TCPS_SYN_RECEIVED:
210180ab7c0eSGarrett Wollman 				so->so_error = ECONNREFUSED;
210280ab7c0eSGarrett Wollman 				goto close;
210380ab7c0eSGarrett Wollman 
210480ab7c0eSGarrett Wollman 			case TCPS_ESTABLISHED:
2105603724d3SBjoern A. Zeeb 				if (V_tcp_insecure_rst == 0 &&
210695ad8418SQing Li 				    !(SEQ_GEQ(th->th_seq, tp->rcv_nxt - 1) &&
210795ad8418SQing Li 				    SEQ_LEQ(th->th_seq, tp->rcv_nxt + 1)) &&
210895ad8418SQing Li 				    !(SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) &&
210995ad8418SQing Li 				    SEQ_LEQ(th->th_seq, tp->last_ack_sent + 1))) {
211078b50714SRobert Watson 					TCPSTAT_INC(tcps_badrst);
211180dd2a81SMike Silbersack 					goto drop;
211280dd2a81SMike Silbersack 				}
2113564aab1fSAndre Oppermann 				/* FALLTHROUGH */
211480ab7c0eSGarrett Wollman 			case TCPS_FIN_WAIT_1:
211580ab7c0eSGarrett Wollman 			case TCPS_FIN_WAIT_2:
211680ab7c0eSGarrett Wollman 			case TCPS_CLOSE_WAIT:
211780ab7c0eSGarrett Wollman 				so->so_error = ECONNRESET;
211880ab7c0eSGarrett Wollman 			close:
2119252ca428SRobert Watson 				KASSERT(ti_locked == TI_WLOCKED,
2120252ca428SRobert Watson 				    ("tcp_do_segment: TH_RST 1 ti_locked %d",
2121252ca428SRobert Watson 				    ti_locked));
2122252ca428SRobert Watson 				INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2123252ca428SRobert Watson 
212457f60867SMark Johnston 				tcp_state_change(tp, TCPS_CLOSED);
212578b50714SRobert Watson 				TCPSTAT_INC(tcps_drops);
212680ab7c0eSGarrett Wollman 				tp = tcp_close(tp);
212780ab7c0eSGarrett Wollman 				break;
212880ab7c0eSGarrett Wollman 
212980ab7c0eSGarrett Wollman 			case TCPS_CLOSING:
213080ab7c0eSGarrett Wollman 			case TCPS_LAST_ACK:
2131252ca428SRobert Watson 				KASSERT(ti_locked == TI_WLOCKED,
2132252ca428SRobert Watson 				    ("tcp_do_segment: TH_RST 2 ti_locked %d",
2133252ca428SRobert Watson 				    ti_locked));
2134252ca428SRobert Watson 				INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2135252ca428SRobert Watson 
213680ab7c0eSGarrett Wollman 				tp = tcp_close(tp);
213780ab7c0eSGarrett Wollman 				break;
213880ab7c0eSGarrett Wollman 			}
213980ab7c0eSGarrett Wollman 		}
214080ab7c0eSGarrett Wollman 		goto drop;
214180ab7c0eSGarrett Wollman 	}
214280ab7c0eSGarrett Wollman 
214380ab7c0eSGarrett Wollman 	/*
2144df8bae1dSRodney W. Grimes 	 * RFC 1323 PAWS: If we have a timestamp reply on this segment
2145df8bae1dSRodney W. Grimes 	 * and it's less than ts_recent, drop it.
2146df8bae1dSRodney W. Grimes 	 */
2147be2ac88cSJonathan Lemon 	if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
214880ab7c0eSGarrett Wollman 	    TSTMP_LT(to.to_tsval, tp->ts_recent)) {
2149df8bae1dSRodney W. Grimes 
2150df8bae1dSRodney W. Grimes 		/* Check to see if ts_recent is over 24 days old.  */
2151d8951c8aSBjoern A. Zeeb 		if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) {
2152df8bae1dSRodney W. Grimes 			/*
2153df8bae1dSRodney W. Grimes 			 * Invalidate ts_recent.  If this segment updates
2154df8bae1dSRodney W. Grimes 			 * ts_recent, the age will be reset later and ts_recent
2155df8bae1dSRodney W. Grimes 			 * will get a valid value.  If it does not, setting
2156df8bae1dSRodney W. Grimes 			 * ts_recent to zero will at least satisfy the
2157df8bae1dSRodney W. Grimes 			 * requirement that zero be placed in the timestamp
2158df8bae1dSRodney W. Grimes 			 * echo reply when ts_recent isn't valid.  The
2159df8bae1dSRodney W. Grimes 			 * age isn't reset until we get a valid ts_recent
2160df8bae1dSRodney W. Grimes 			 * because we don't want out-of-order segments to be
2161df8bae1dSRodney W. Grimes 			 * dropped when ts_recent is old.
2162df8bae1dSRodney W. Grimes 			 */
2163df8bae1dSRodney W. Grimes 			tp->ts_recent = 0;
2164df8bae1dSRodney W. Grimes 		} else {
216578b50714SRobert Watson 			TCPSTAT_INC(tcps_rcvduppack);
216678b50714SRobert Watson 			TCPSTAT_ADD(tcps_rcvdupbyte, tlen);
216778b50714SRobert Watson 			TCPSTAT_INC(tcps_pawsdrop);
216807fd333dSMatthew Dillon 			if (tlen)
2169df8bae1dSRodney W. Grimes 				goto dropafterack;
21701ab4789dSMatthew Dillon 			goto drop;
21711ab4789dSMatthew Dillon 		}
2172df8bae1dSRodney W. Grimes 	}
2173df8bae1dSRodney W. Grimes 
2174a0292f23SGarrett Wollman 	/*
217580ab7c0eSGarrett Wollman 	 * In the SYN-RECEIVED state, validate that the packet belongs to
217680ab7c0eSGarrett Wollman 	 * this connection before trimming the data to fit the receive
217780ab7c0eSGarrett Wollman 	 * window.  Check the sequence number versus IRS since we know
217880ab7c0eSGarrett Wollman 	 * the sequence numbers haven't wrapped.  This is a partial fix
217980ab7c0eSGarrett Wollman 	 * for the "LAND" DoS attack.
218080ab7c0eSGarrett Wollman 	 */
2181a57815efSBosko Milekic 	if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
2182a57815efSBosko Milekic 		rstreason = BANDLIM_RST_OPENPORT;
2183a57815efSBosko Milekic 		goto dropwithreset;
2184a57815efSBosko Milekic 	}
218580ab7c0eSGarrett Wollman 
2186fb59c426SYoshinobu Inoue 	todrop = tp->rcv_nxt - th->th_seq;
2187df8bae1dSRodney W. Grimes 	if (todrop > 0) {
2188*831ad37eSXin LI 		if (thflags & TH_SYN) {
2189fb59c426SYoshinobu Inoue 			thflags &= ~TH_SYN;
2190fb59c426SYoshinobu Inoue 			th->th_seq++;
2191fb59c426SYoshinobu Inoue 			if (th->th_urp > 1)
2192fb59c426SYoshinobu Inoue 				th->th_urp--;
2193df8bae1dSRodney W. Grimes 			else
2194fb59c426SYoshinobu Inoue 				thflags &= ~TH_URG;
2195df8bae1dSRodney W. Grimes 			todrop--;
2196df8bae1dSRodney W. Grimes 		}
2197df8bae1dSRodney W. Grimes 		/*
2198dac20301SGarrett Wollman 		 * Following if statement from Stevens, vol. 2, p. 960.
2199df8bae1dSRodney W. Grimes 		 */
2200fb59c426SYoshinobu Inoue 		if (todrop > tlen
2201fb59c426SYoshinobu Inoue 		    || (todrop == tlen && (thflags & TH_FIN) == 0)) {
2202dac20301SGarrett Wollman 			/*
2203dac20301SGarrett Wollman 			 * Any valid FIN must be to the left of the window.
2204dac20301SGarrett Wollman 			 * At this point the FIN must be a duplicate or out
2205dac20301SGarrett Wollman 			 * of sequence; drop it.
2206dac20301SGarrett Wollman 			 */
2207fb59c426SYoshinobu Inoue 			thflags &= ~TH_FIN;
2208dac20301SGarrett Wollman 
2209df8bae1dSRodney W. Grimes 			/*
2210dac20301SGarrett Wollman 			 * Send an ACK to resynchronize and drop any data.
2211dac20301SGarrett Wollman 			 * But keep on processing for RST or ACK.
2212df8bae1dSRodney W. Grimes 			 */
2213dac20301SGarrett Wollman 			tp->t_flags |= TF_ACKNOW;
2214fb59c426SYoshinobu Inoue 			todrop = tlen;
221578b50714SRobert Watson 			TCPSTAT_INC(tcps_rcvduppack);
221678b50714SRobert Watson 			TCPSTAT_ADD(tcps_rcvdupbyte, todrop);
2217df8bae1dSRodney W. Grimes 		} else {
221878b50714SRobert Watson 			TCPSTAT_INC(tcps_rcvpartduppack);
221978b50714SRobert Watson 			TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop);
2220df8bae1dSRodney W. Grimes 		}
2221fb59c426SYoshinobu Inoue 		drop_hdrlen += todrop;	/* drop from the top afterwards */
2222fb59c426SYoshinobu Inoue 		th->th_seq += todrop;
2223fb59c426SYoshinobu Inoue 		tlen -= todrop;
2224fb59c426SYoshinobu Inoue 		if (th->th_urp > todrop)
2225fb59c426SYoshinobu Inoue 			th->th_urp -= todrop;
2226df8bae1dSRodney W. Grimes 		else {
2227fb59c426SYoshinobu Inoue 			thflags &= ~TH_URG;
2228fb59c426SYoshinobu Inoue 			th->th_urp = 0;
2229df8bae1dSRodney W. Grimes 		}
2230df8bae1dSRodney W. Grimes 	}
2231df8bae1dSRodney W. Grimes 
2232df8bae1dSRodney W. Grimes 	/*
2233df8bae1dSRodney W. Grimes 	 * If new data are received on a connection after the
2234df8bae1dSRodney W. Grimes 	 * user processes are gone, then RST the other end.
2235df8bae1dSRodney W. Grimes 	 */
2236df8bae1dSRodney W. Grimes 	if ((so->so_state & SS_NOFDREF) &&
2237fb59c426SYoshinobu Inoue 	    tp->t_state > TCPS_CLOSE_WAIT && tlen) {
2238252ca428SRobert Watson 		KASSERT(ti_locked == TI_WLOCKED, ("%s: SS_NOFDEREF && "
2239252ca428SRobert Watson 		    "CLOSE_WAIT && tlen ti_locked %d", __func__, ti_locked));
2240252ca428SRobert Watson 		INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2241252ca428SRobert Watson 
224207dacf03SAndre Oppermann 		if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
224307dacf03SAndre Oppermann 			log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data "
224407dacf03SAndre Oppermann 			    "after socket was closed, "
224507dacf03SAndre Oppermann 			    "sending RST and removing tcpcb\n",
2246e31d8aa3SMike Silbersack 			    s, __func__, tcpstates[tp->t_state], tlen);
2247773673c1SAndre Oppermann 			free(s, M_TCPLOG);
2248773673c1SAndre Oppermann 		}
2249df8bae1dSRodney W. Grimes 		tp = tcp_close(tp);
225078b50714SRobert Watson 		TCPSTAT_INC(tcps_rcvafterclose);
2251a57815efSBosko Milekic 		rstreason = BANDLIM_UNLIMITED;
2252df8bae1dSRodney W. Grimes 		goto dropwithreset;
2253df8bae1dSRodney W. Grimes 	}
2254df8bae1dSRodney W. Grimes 
2255df8bae1dSRodney W. Grimes 	/*
2256df8bae1dSRodney W. Grimes 	 * If segment ends after window, drop trailing data
2257df8bae1dSRodney W. Grimes 	 * (and PUSH and FIN); if nothing left, just ACK.
2258df8bae1dSRodney W. Grimes 	 */
2259fb59c426SYoshinobu Inoue 	todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd);
2260df8bae1dSRodney W. Grimes 	if (todrop > 0) {
226178b50714SRobert Watson 		TCPSTAT_INC(tcps_rcvpackafterwin);
2262fb59c426SYoshinobu Inoue 		if (todrop >= tlen) {
226378b50714SRobert Watson 			TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen);
2264df8bae1dSRodney W. Grimes 			/*
2265df8bae1dSRodney W. Grimes 			 * If window is closed can only take segments at
2266df8bae1dSRodney W. Grimes 			 * window edge, and have to drop data and PUSH from
2267df8bae1dSRodney W. Grimes 			 * incoming segments.  Continue processing, but
2268df8bae1dSRodney W. Grimes 			 * remember to ack.  Otherwise, drop segment
2269df8bae1dSRodney W. Grimes 			 * and ack.
2270df8bae1dSRodney W. Grimes 			 */
2271fb59c426SYoshinobu Inoue 			if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
2272df8bae1dSRodney W. Grimes 				tp->t_flags |= TF_ACKNOW;
227378b50714SRobert Watson 				TCPSTAT_INC(tcps_rcvwinprobe);
2274df8bae1dSRodney W. Grimes 			} else
2275df8bae1dSRodney W. Grimes 				goto dropafterack;
2276df8bae1dSRodney W. Grimes 		} else
227778b50714SRobert Watson 			TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
2278df8bae1dSRodney W. Grimes 		m_adj(m, -todrop);
2279fb59c426SYoshinobu Inoue 		tlen -= todrop;
2280fb59c426SYoshinobu Inoue 		thflags &= ~(TH_PUSH|TH_FIN);
2281df8bae1dSRodney W. Grimes 	}
2282df8bae1dSRodney W. Grimes 
2283df8bae1dSRodney W. Grimes 	/*
2284df8bae1dSRodney W. Grimes 	 * If last ACK falls within this segment's sequence numbers,
2285df8bae1dSRodney W. Grimes 	 * record its timestamp.
2286cf09195bSPaul Saab 	 * NOTE:
2287cf09195bSPaul Saab 	 * 1) That the test incorporates suggestions from the latest
2288a0292f23SGarrett Wollman 	 *    proposal of the tcplw@cray.com list (Braden 1993/04/26).
2289cf09195bSPaul Saab 	 * 2) That updating only on newer timestamps interferes with
2290cf09195bSPaul Saab 	 *    our earlier PAWS tests, so this check should be solely
2291cf09195bSPaul Saab 	 *    predicated on the sequence space of this segment.
2292cf09195bSPaul Saab 	 * 3) That we modify the segment boundary check to be
2293cf09195bSPaul Saab 	 *        Last.ACK.Sent <= SEG.SEQ + SEG.Len
2294cf09195bSPaul Saab 	 *    instead of RFC1323's
2295cf09195bSPaul Saab 	 *        Last.ACK.Sent < SEG.SEQ + SEG.Len,
2296cf09195bSPaul Saab 	 *    This modified check allows us to overcome RFC1323's
2297cf09195bSPaul Saab 	 *    limitations as described in Stevens TCP/IP Illustrated
2298cf09195bSPaul Saab 	 *    Vol. 2 p.869. In such cases, we can still calculate the
2299cf09195bSPaul Saab 	 *    RTT correctly when RCV.NXT == Last.ACK.Sent.
2300df8bae1dSRodney W. Grimes 	 */
2301be2ac88cSJonathan Lemon 	if ((to.to_flags & TOF_TS) != 0 &&
2302cf09195bSPaul Saab 	    SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
2303cf09195bSPaul Saab 	    SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen +
2304cf09195bSPaul Saab 		((thflags & (TH_SYN|TH_FIN)) != 0))) {
2305d8951c8aSBjoern A. Zeeb 		tp->ts_recent_age = tcp_ts_getticks();
2306a0292f23SGarrett Wollman 		tp->ts_recent = to.to_tsval;
2307df8bae1dSRodney W. Grimes 	}
2308df8bae1dSRodney W. Grimes 
2309df8bae1dSRodney W. Grimes 	/*
2310df8bae1dSRodney W. Grimes 	 * If a SYN is in the window, then this is an
2311df8bae1dSRodney W. Grimes 	 * error and we send an RST and drop the connection.
2312df8bae1dSRodney W. Grimes 	 */
2313fb59c426SYoshinobu Inoue 	if (thflags & TH_SYN) {
2314252ca428SRobert Watson 		KASSERT(ti_locked == TI_WLOCKED,
2315252ca428SRobert Watson 		    ("tcp_do_segment: TH_SYN ti_locked %d", ti_locked));
2316252ca428SRobert Watson 		INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2317252ca428SRobert Watson 
2318df8bae1dSRodney W. Grimes 		tp = tcp_drop(tp, ECONNRESET);
2319a57815efSBosko Milekic 		rstreason = BANDLIM_UNLIMITED;
2320122aad88SAndre Oppermann 		goto drop;
2321df8bae1dSRodney W. Grimes 	}
2322df8bae1dSRodney W. Grimes 
2323a0292f23SGarrett Wollman 	/*
2324a0292f23SGarrett Wollman 	 * If the ACK bit is off:  if in SYN-RECEIVED state or SENDSYN
2325a0292f23SGarrett Wollman 	 * flag is on (half-synchronized state), then queue data for
2326a0292f23SGarrett Wollman 	 * later processing; else drop segment and return.
2327a0292f23SGarrett Wollman 	 */
2328fb59c426SYoshinobu Inoue 	if ((thflags & TH_ACK) == 0) {
2329a0292f23SGarrett Wollman 		if (tp->t_state == TCPS_SYN_RECEIVED ||
2330a0292f23SGarrett Wollman 		    (tp->t_flags & TF_NEEDSYN))
2331a0292f23SGarrett Wollman 			goto step6;
23325e1aa279SDavid Malone 		else if (tp->t_flags & TF_ACKNOW)
23335e1aa279SDavid Malone 			goto dropafterack;
2334a0292f23SGarrett Wollman 		else
2335a0292f23SGarrett Wollman 			goto drop;
2336a0292f23SGarrett Wollman 	}
2337df8bae1dSRodney W. Grimes 
2338df8bae1dSRodney W. Grimes 	/*
2339df8bae1dSRodney W. Grimes 	 * Ack processing.
2340df8bae1dSRodney W. Grimes 	 */
2341df8bae1dSRodney W. Grimes 	switch (tp->t_state) {
2342df8bae1dSRodney W. Grimes 
2343df8bae1dSRodney W. Grimes 	/*
2344764d8cefSBill Fenner 	 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter
2345764d8cefSBill Fenner 	 * ESTABLISHED state and continue processing.
2346764d8cefSBill Fenner 	 * The ACK was checked above.
2347df8bae1dSRodney W. Grimes 	 */
2348df8bae1dSRodney W. Grimes 	case TCPS_SYN_RECEIVED:
2349a0292f23SGarrett Wollman 
235078b50714SRobert Watson 		TCPSTAT_INC(tcps_connects);
2351df8bae1dSRodney W. Grimes 		soisconnected(so);
2352df8bae1dSRodney W. Grimes 		/* Do window scaling? */
2353df8bae1dSRodney W. Grimes 		if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
2354df8bae1dSRodney W. Grimes 			(TF_RCVD_SCALE|TF_REQ_SCALE)) {
2355df8bae1dSRodney W. Grimes 			tp->rcv_scale = tp->request_r_scale;
2356464fcfbcSAndre Oppermann 			tp->snd_wnd = tiwin;
2357df8bae1dSRodney W. Grimes 		}
2358a0292f23SGarrett Wollman 		/*
2359a0292f23SGarrett Wollman 		 * Make transitions:
2360a0292f23SGarrett Wollman 		 *      SYN-RECEIVED  -> ESTABLISHED
2361a0292f23SGarrett Wollman 		 *      SYN-RECEIVED* -> FIN-WAIT-1
2362a0292f23SGarrett Wollman 		 */
23639b8b58e0SJonathan Lemon 		tp->t_starttime = ticks;
2364a0292f23SGarrett Wollman 		if (tp->t_flags & TF_NEEDFIN) {
236557f60867SMark Johnston 			tcp_state_change(tp, TCPS_FIN_WAIT_1);
2366a0292f23SGarrett Wollman 			tp->t_flags &= ~TF_NEEDFIN;
23677ff19458SPaul Traina 		} else {
236857f60867SMark Johnston 			tcp_state_change(tp, TCPS_ESTABLISHED);
2369d9fae5abSAndriy Gapon 			TCP_PROBE5(accept__established, NULL, tp,
2370fa22ce15SAdrian Chadd 			    mtod(m, const char *), tp, th);
2371dbc42409SLawrence Stewart 			cc_conn_init(tp);
23729077f387SGleb Smirnoff 			tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
23737ff19458SPaul Traina 		}
2374a0292f23SGarrett Wollman 		/*
2375a0292f23SGarrett Wollman 		 * If segment contains data or ACK, will call tcp_reass()
2376a0292f23SGarrett Wollman 		 * later; if not, do so now to pass queued data to user.
2377a0292f23SGarrett Wollman 		 */
2378fb59c426SYoshinobu Inoue 		if (tlen == 0 && (thflags & TH_FIN) == 0)
2379fb59c426SYoshinobu Inoue 			(void) tcp_reass(tp, (struct tcphdr *)0, 0,
2380a0292f23SGarrett Wollman 			    (struct mbuf *)0);
238160ee3bb2SAndre Oppermann 		tp->snd_wl1 = th->th_seq - 1;
238293b0017fSPhilippe Charnier 		/* FALLTHROUGH */
2383df8bae1dSRodney W. Grimes 
2384df8bae1dSRodney W. Grimes 	/*
2385df8bae1dSRodney W. Grimes 	 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
2386df8bae1dSRodney W. Grimes 	 * ACKs.  If the ack is in the range
2387fb59c426SYoshinobu Inoue 	 *	tp->snd_una < th->th_ack <= tp->snd_max
2388fb59c426SYoshinobu Inoue 	 * then advance tp->snd_una to th->th_ack and drop
2389df8bae1dSRodney W. Grimes 	 * data from the retransmission queue.  If this ACK reflects
2390df8bae1dSRodney W. Grimes 	 * more up to date window information we update our window information.
2391df8bae1dSRodney W. Grimes 	 */
2392df8bae1dSRodney W. Grimes 	case TCPS_ESTABLISHED:
2393df8bae1dSRodney W. Grimes 	case TCPS_FIN_WAIT_1:
2394df8bae1dSRodney W. Grimes 	case TCPS_FIN_WAIT_2:
2395df8bae1dSRodney W. Grimes 	case TCPS_CLOSE_WAIT:
2396df8bae1dSRodney W. Grimes 	case TCPS_CLOSING:
2397df8bae1dSRodney W. Grimes 	case TCPS_LAST_ACK:
23985a53ca16SPaul Saab 		if (SEQ_GT(th->th_ack, tp->snd_max)) {
239978b50714SRobert Watson 			TCPSTAT_INC(tcps_rcvacktoomuch);
24005a53ca16SPaul Saab 			goto dropafterack;
24015a53ca16SPaul Saab 		}
24023529149eSAndre Oppermann 		if ((tp->t_flags & TF_SACK_PERMIT) &&
2403fc30a251SAndre Oppermann 		    ((to.to_flags & TOF_SACK) ||
2404fc30a251SAndre Oppermann 		     !TAILQ_EMPTY(&tp->snd_holes)))
24055a53ca16SPaul Saab 			tcp_sack_doack(tp, &to, th->th_ack);
240639bc9de5SLawrence Stewart 
240739bc9de5SLawrence Stewart 		/* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */
240839bc9de5SLawrence Stewart 		hhook_run_tcp_est_in(tp, th, &to);
240939bc9de5SLawrence Stewart 
2410fb59c426SYoshinobu Inoue 		if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
241162b90589SPeter Wemm 			if (tlen == 0 && tiwin == tp->snd_wnd) {
241262b90589SPeter Wemm 				/*
241362b90589SPeter Wemm 				 * If this is the first time we've seen a
241462b90589SPeter Wemm 				 * FIN from the remote, this is not a
241562b90589SPeter Wemm 				 * duplicate and it needs to be processed
241662b90589SPeter Wemm 				 * normally.  This happens during a
241762b90589SPeter Wemm 				 * simultaneous close.
241862b90589SPeter Wemm 				 */
241962b90589SPeter Wemm 				if ((thflags & TH_FIN) &&
242062b90589SPeter Wemm 				    (TCPS_HAVERCVDFIN(tp->t_state) == 0)) {
242162b90589SPeter Wemm 					tp->t_dupacks = 0;
242262b90589SPeter Wemm 					break;
242362b90589SPeter Wemm 				}
242478b50714SRobert Watson 				TCPSTAT_INC(tcps_rcvdupack);
2425df8bae1dSRodney W. Grimes 				/*
2426df8bae1dSRodney W. Grimes 				 * If we have outstanding data (other than
2427df8bae1dSRodney W. Grimes 				 * a window probe), this is a completely
2428df8bae1dSRodney W. Grimes 				 * duplicate ack (ie, window info didn't
24295f30ec9bSEitan Adler 				 * change and FIN isn't set),
24305f30ec9bSEitan Adler 				 * the ack is the biggest we've
2431df8bae1dSRodney W. Grimes 				 * seen and we've seen exactly our rexmt
2432df8bae1dSRodney W. Grimes 				 * threshhold of them, assume a packet
2433df8bae1dSRodney W. Grimes 				 * has been dropped and retransmit it.
2434df8bae1dSRodney W. Grimes 				 * Kludge snd_nxt & the congestion
2435df8bae1dSRodney W. Grimes 				 * window so we send only this one
2436df8bae1dSRodney W. Grimes 				 * packet.
2437df8bae1dSRodney W. Grimes 				 *
2438df8bae1dSRodney W. Grimes 				 * We know we're losing at the current
2439df8bae1dSRodney W. Grimes 				 * window size so do congestion avoidance
2440df8bae1dSRodney W. Grimes 				 * (set ssthresh to half the current window
2441df8bae1dSRodney W. Grimes 				 * and pull our congestion window back to
2442df8bae1dSRodney W. Grimes 				 * the new ssthresh).
2443df8bae1dSRodney W. Grimes 				 *
2444df8bae1dSRodney W. Grimes 				 * Dup acks mean that packets have left the
2445df8bae1dSRodney W. Grimes 				 * network (they're now cached at the receiver)
2446df8bae1dSRodney W. Grimes 				 * so bump cwnd by the amount in the receiver
2447df8bae1dSRodney W. Grimes 				 * to keep a constant cwnd packets in the
2448df8bae1dSRodney W. Grimes 				 * network.
2449f2512ba1SRui Paulo 				 *
2450f2512ba1SRui Paulo 				 * When using TCP ECN, notify the peer that
2451f2512ba1SRui Paulo 				 * we reduced the cwnd.
2452df8bae1dSRodney W. Grimes 				 */
2453b8152ba7SAndre Oppermann 				if (!tcp_timer_active(tp, TT_REXMT) ||
2454fb59c426SYoshinobu Inoue 				    th->th_ack != tp->snd_una)
2455df8bae1dSRodney W. Grimes 					tp->t_dupacks = 0;
2456cb942153SJeffrey Hsu 				else if (++tp->t_dupacks > tcprexmtthresh ||
2457dbc42409SLawrence Stewart 				     IN_FASTRECOVERY(tp->t_flags)) {
2458dbc42409SLawrence Stewart 					cc_ack_received(tp, th, CC_DUPACK);
24593529149eSAndre Oppermann 					if ((tp->t_flags & TF_SACK_PERMIT) &&
2460dbc42409SLawrence Stewart 					    IN_FASTRECOVERY(tp->t_flags)) {
2461808f11b7SPaul Saab 						int awnd;
246225e6f9edSPaul Saab 
246325e6f9edSPaul Saab 						/*
246425e6f9edSPaul Saab 						 * Compute the amount of data in flight first.
246525e6f9edSPaul Saab 						 * We can inject new data into the pipe iff
246625e6f9edSPaul Saab 						 * we have less than 1/2 the original window's
246725e6f9edSPaul Saab 						 * worth of data in flight.
246825e6f9edSPaul Saab 						 */
2469808f11b7SPaul Saab 						awnd = (tp->snd_nxt - tp->snd_fack) +
24700077b016SPaul Saab 							tp->sackhint.sack_bytes_rexmit;
2471808f11b7SPaul Saab 						if (awnd < tp->snd_ssthresh) {
247225e6f9edSPaul Saab 							tp->snd_cwnd += tp->t_maxseg;
247325e6f9edSPaul Saab 							if (tp->snd_cwnd > tp->snd_ssthresh)
247425e6f9edSPaul Saab 								tp->snd_cwnd = tp->snd_ssthresh;
247525e6f9edSPaul Saab 						}
247625e6f9edSPaul Saab 					} else
247746f58482SJonathan Lemon 						tp->snd_cwnd += tp->t_maxseg;
247846f58482SJonathan Lemon 					(void) tcp_output(tp);
247946f58482SJonathan Lemon 					goto drop;
2480cb942153SJeffrey Hsu 				} else if (tp->t_dupacks == tcprexmtthresh) {
2481cb942153SJeffrey Hsu 					tcp_seq onxt = tp->snd_nxt;
2482a0445c2eSJayanth Vijayaraghavan 
2483a0445c2eSJayanth Vijayaraghavan 					/*
2484a0445c2eSJayanth Vijayaraghavan 					 * If we're doing sack, check to
2485a0445c2eSJayanth Vijayaraghavan 					 * see if we're already in sack
2486a0445c2eSJayanth Vijayaraghavan 					 * recovery. If we're not doing sack,
2487a0445c2eSJayanth Vijayaraghavan 					 * check to see if we're in newreno
2488a0445c2eSJayanth Vijayaraghavan 					 * recovery.
2489a0445c2eSJayanth Vijayaraghavan 					 */
24903529149eSAndre Oppermann 					if (tp->t_flags & TF_SACK_PERMIT) {
2491dbc42409SLawrence Stewart 						if (IN_FASTRECOVERY(tp->t_flags)) {
2492a0445c2eSJayanth Vijayaraghavan 							tp->t_dupacks = 0;
2493a0445c2eSJayanth Vijayaraghavan 							break;
2494a0445c2eSJayanth Vijayaraghavan 						}
2495dbc42409SLawrence Stewart 					} else {
2496a0445c2eSJayanth Vijayaraghavan 						if (SEQ_LEQ(th->th_ack,
24979d11646dSJeffrey Hsu 						    tp->snd_recover)) {
2498cb942153SJeffrey Hsu 							tp->t_dupacks = 0;
2499cb942153SJeffrey Hsu 							break;
250046f58482SJonathan Lemon 						}
2501a0445c2eSJayanth Vijayaraghavan 					}
2502dbc42409SLawrence Stewart 					/* Congestion signal before ack. */
2503dbc42409SLawrence Stewart 					cc_cong_signal(tp, th, CC_NDUPACK);
2504dbc42409SLawrence Stewart 					cc_ack_received(tp, th, CC_DUPACK);
2505b8152ba7SAndre Oppermann 					tcp_timer_activate(tp, TT_REXMT, 0);
25069b8b58e0SJonathan Lemon 					tp->t_rtttime = 0;
25073529149eSAndre Oppermann 					if (tp->t_flags & TF_SACK_PERMIT) {
250878b50714SRobert Watson 						TCPSTAT_INC(
250978b50714SRobert Watson 						    tcps_sack_recovery_episode);
2510a55db2b6SPaul Saab 						tp->sack_newdata = tp->snd_nxt;
25118db456bfSPaul Saab 						tp->snd_cwnd = tp->t_maxseg;
25126d90faf3SPaul Saab 						(void) tcp_output(tp);
25136d90faf3SPaul Saab 						goto drop;
25146d90faf3SPaul Saab 					}
2515fb59c426SYoshinobu Inoue 					tp->snd_nxt = th->th_ack;
2516df8bae1dSRodney W. Grimes 					tp->snd_cwnd = tp->t_maxseg;
2517df8bae1dSRodney W. Grimes 					(void) tcp_output(tp);
251848d2549cSJeffrey Hsu 					KASSERT(tp->snd_limited <= 2,
2519302ce8d6SAndre Oppermann 					    ("%s: tp->snd_limited too big",
2520302ce8d6SAndre Oppermann 					    __func__));
2521df8bae1dSRodney W. Grimes 					tp->snd_cwnd = tp->snd_ssthresh +
252248d2549cSJeffrey Hsu 					     tp->t_maxseg *
252348d2549cSJeffrey Hsu 					     (tp->t_dupacks - tp->snd_limited);
2524df8bae1dSRodney W. Grimes 					if (SEQ_GT(onxt, tp->snd_nxt))
2525df8bae1dSRodney W. Grimes 						tp->snd_nxt = onxt;
2526df8bae1dSRodney W. Grimes 					goto drop;
2527603724d3SBjoern A. Zeeb 				} else if (V_tcp_do_rfc3042) {
2528dbc42409SLawrence Stewart 					cc_ack_received(tp, th, CC_DUPACK);
2529582a954bSJeffrey Hsu 					u_long oldcwnd = tp->snd_cwnd;
253048d2549cSJeffrey Hsu 					tcp_seq oldsndmax = tp->snd_max;
253148d2549cSJeffrey Hsu 					u_int sent;
25325628dd08SAndre Oppermann 					int avail;
253389c02376SJeffrey Hsu 
2534582a954bSJeffrey Hsu 					KASSERT(tp->t_dupacks == 1 ||
2535582a954bSJeffrey Hsu 					    tp->t_dupacks == 2,
2536302ce8d6SAndre Oppermann 					    ("%s: dupacks not 1 or 2",
2537302ce8d6SAndre Oppermann 					    __func__));
253861a36e3dSJeffrey Hsu 					if (tp->t_dupacks == 1)
253948d2549cSJeffrey Hsu 						tp->snd_limited = 0;
254061a36e3dSJeffrey Hsu 					tp->snd_cwnd =
254161a36e3dSJeffrey Hsu 					    (tp->snd_nxt - tp->snd_una) +
254261a36e3dSJeffrey Hsu 					    (tp->t_dupacks - tp->snd_limited) *
254361a36e3dSJeffrey Hsu 					    tp->t_maxseg;
25445628dd08SAndre Oppermann 					/*
25455628dd08SAndre Oppermann 					 * Only call tcp_output when there
25465628dd08SAndre Oppermann 					 * is new data available to be sent.
25475628dd08SAndre Oppermann 					 * Otherwise we would send pure ACKs.
25485628dd08SAndre Oppermann 					 */
25495628dd08SAndre Oppermann 					SOCKBUF_LOCK(&so->so_snd);
25505628dd08SAndre Oppermann 					avail = so->so_snd.sb_cc -
25515628dd08SAndre Oppermann 					    (tp->snd_nxt - tp->snd_una);
25525628dd08SAndre Oppermann 					SOCKBUF_UNLOCK(&so->so_snd);
25535628dd08SAndre Oppermann 					if (avail > 0)
2554582a954bSJeffrey Hsu 						(void) tcp_output(tp);
255548d2549cSJeffrey Hsu 					sent = tp->snd_max - oldsndmax;
255648d2549cSJeffrey Hsu 					if (sent > tp->t_maxseg) {
255789c02376SJeffrey Hsu 						KASSERT((tp->t_dupacks == 2 &&
255889c02376SJeffrey Hsu 						    tp->snd_limited == 0) ||
255989c02376SJeffrey Hsu 						   (sent == tp->t_maxseg + 1 &&
256089c02376SJeffrey Hsu 						    tp->t_flags & TF_SENTFIN),
2561302ce8d6SAndre Oppermann 						    ("%s: sent too much",
2562302ce8d6SAndre Oppermann 						    __func__));
256348d2549cSJeffrey Hsu 						tp->snd_limited = 2;
256448d2549cSJeffrey Hsu 					} else if (sent > 0)
256548d2549cSJeffrey Hsu 						++tp->snd_limited;
2566582a954bSJeffrey Hsu 					tp->snd_cwnd = oldcwnd;
2567582a954bSJeffrey Hsu 					goto drop;
2568df8bae1dSRodney W. Grimes 				}
2569df8bae1dSRodney W. Grimes 			} else
2570df8bae1dSRodney W. Grimes 				tp->t_dupacks = 0;
2571df8bae1dSRodney W. Grimes 			break;
2572df8bae1dSRodney W. Grimes 		}
2573cb942153SJeffrey Hsu 
2574302ce8d6SAndre Oppermann 		KASSERT(SEQ_GT(th->th_ack, tp->snd_una),
2575302ce8d6SAndre Oppermann 		    ("%s: th_ack <= snd_una", __func__));
2576cb942153SJeffrey Hsu 
2577df8bae1dSRodney W. Grimes 		/*
2578df8bae1dSRodney W. Grimes 		 * If the congestion window was inflated to account
2579df8bae1dSRodney W. Grimes 		 * for the other side's cached packets, retract it.
2580df8bae1dSRodney W. Grimes 		 */
2581dbc42409SLawrence Stewart 		if (IN_FASTRECOVERY(tp->t_flags)) {
2582cb942153SJeffrey Hsu 			if (SEQ_LT(th->th_ack, tp->snd_recover)) {
25833529149eSAndre Oppermann 				if (tp->t_flags & TF_SACK_PERMIT)
25846d90faf3SPaul Saab 					tcp_sack_partialack(tp, th);
25856d90faf3SPaul Saab 				else
2586c068736aSJeffrey Hsu 					tcp_newreno_partial_ack(tp, th);
2587dbc42409SLawrence Stewart 			} else
2588dbc42409SLawrence Stewart 				cc_post_recovery(tp, th);
258946f58482SJonathan Lemon 		}
2590cb942153SJeffrey Hsu 		tp->t_dupacks = 0;
2591a0292f23SGarrett Wollman 		/*
2592a0292f23SGarrett Wollman 		 * If we reach this point, ACK is not a duplicate,
2593a0292f23SGarrett Wollman 		 *     i.e., it ACKs something we sent.
2594a0292f23SGarrett Wollman 		 */
2595a0292f23SGarrett Wollman 		if (tp->t_flags & TF_NEEDSYN) {
2596a0292f23SGarrett Wollman 			/*
2597a0292f23SGarrett Wollman 			 * T/TCP: Connection was half-synchronized, and our
2598a0292f23SGarrett Wollman 			 * SYN has been ACK'd (so connection is now fully
259907e43e10SAndras Olah 			 * synchronized).  Go to non-starred state,
260007e43e10SAndras Olah 			 * increment snd_una for ACK of SYN, and check if
260107e43e10SAndras Olah 			 * we can do window scaling.
2602a0292f23SGarrett Wollman 			 */
2603a0292f23SGarrett Wollman 			tp->t_flags &= ~TF_NEEDSYN;
2604a0292f23SGarrett Wollman 			tp->snd_una++;
260507e43e10SAndras Olah 			/* Do window scaling? */
260607e43e10SAndras Olah 			if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
260707e43e10SAndras Olah 				(TF_RCVD_SCALE|TF_REQ_SCALE)) {
260807e43e10SAndras Olah 				tp->rcv_scale = tp->request_r_scale;
2609464fcfbcSAndre Oppermann 				/* Send window already scaled. */
261007e43e10SAndras Olah 			}
2611a0292f23SGarrett Wollman 		}
2612a0292f23SGarrett Wollman 
2613a0292f23SGarrett Wollman process_ACK:
26148501a69cSRobert Watson 		INP_WLOCK_ASSERT(tp->t_inpcb);
26157cfc6904SRobert Watson 
2616dbc42409SLawrence Stewart 		acked = BYTES_THIS_ACK(tp, th);
261778b50714SRobert Watson 		TCPSTAT_INC(tcps_rcvackpack);
261878b50714SRobert Watson 		TCPSTAT_ADD(tcps_rcvackbyte, acked);
2619df8bae1dSRodney W. Grimes 
2620df8bae1dSRodney W. Grimes 		/*
26219b8b58e0SJonathan Lemon 		 * If we just performed our first retransmit, and the ACK
26229b8b58e0SJonathan Lemon 		 * arrives within our recovery window, then it was a mistake
26239b8b58e0SJonathan Lemon 		 * to do the retransmit in the first place.  Recover our
26249b8b58e0SJonathan Lemon 		 * original cwnd and ssthresh, and proceed to transmit where
26259b8b58e0SJonathan Lemon 		 * we left off.
26269b8b58e0SJonathan Lemon 		 */
2627672dc4aeSJohn Baldwin 		if (tp->t_rxtshift == 1 && tp->t_flags & TF_PREVVALID &&
2628672dc4aeSJohn Baldwin 		    (int)(ticks - tp->t_badrxtwin) < 0)
2629dbc42409SLawrence Stewart 			cc_cong_signal(tp, th, CC_RTO_ERR);
26309b8b58e0SJonathan Lemon 
26319b8b58e0SJonathan Lemon 		/*
2632df8bae1dSRodney W. Grimes 		 * If we have a timestamp reply, update smoothed
2633df8bae1dSRodney W. Grimes 		 * round trip time.  If no timestamp is present but
2634df8bae1dSRodney W. Grimes 		 * transmit timer is running and timed sequence
2635df8bae1dSRodney W. Grimes 		 * number was acked, update smoothed round trip time.
2636df8bae1dSRodney W. Grimes 		 * Since we now have an rtt measurement, cancel the
2637df8bae1dSRodney W. Grimes 		 * timer backoff (cf., Phil Karn's retransmit alg.).
2638df8bae1dSRodney W. Grimes 		 * Recompute the initial retransmit timer.
2639fa55172bSMatthew Dillon 		 *
2640fa55172bSMatthew Dillon 		 * Some boxes send broken timestamp replies
2641fa55172bSMatthew Dillon 		 * during the SYN+ACK phase, ignore
2642fa55172bSMatthew Dillon 		 * timestamps of 0 or we could calculate a
2643fa55172bSMatthew Dillon 		 * huge RTT and blow up the retransmit timer.
2644df8bae1dSRodney W. Grimes 		 */
2645d8951c8aSBjoern A. Zeeb 		if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) {
2646d8951c8aSBjoern A. Zeeb 			u_int t;
2647d8951c8aSBjoern A. Zeeb 
2648d8951c8aSBjoern A. Zeeb 			t = tcp_ts_getticks() - to.to_tsecr;
2649d8951c8aSBjoern A. Zeeb 			if (!tp->t_rttlow || tp->t_rttlow > t)
2650d8951c8aSBjoern A. Zeeb 				tp->t_rttlow = t;
2651d8951c8aSBjoern A. Zeeb 			tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1);
2652fa55172bSMatthew Dillon 		} else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) {
2653eaf80179SAndre Oppermann 			if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime)
2654eaf80179SAndre Oppermann 				tp->t_rttlow = ticks - tp->t_rtttime;
26559b8b58e0SJonathan Lemon 			tcp_xmit_timer(tp, ticks - tp->t_rtttime);
2656fa55172bSMatthew Dillon 		}
2657df8bae1dSRodney W. Grimes 
2658df8bae1dSRodney W. Grimes 		/*
2659df8bae1dSRodney W. Grimes 		 * If all outstanding data is acked, stop retransmit
2660df8bae1dSRodney W. Grimes 		 * timer and remember to restart (more output or persist).
2661df8bae1dSRodney W. Grimes 		 * If there is more data to be acked, restart retransmit
2662df8bae1dSRodney W. Grimes 		 * timer, using current (possibly backed-off) value.
2663df8bae1dSRodney W. Grimes 		 */
2664fb59c426SYoshinobu Inoue 		if (th->th_ack == tp->snd_max) {
2665b8152ba7SAndre Oppermann 			tcp_timer_activate(tp, TT_REXMT, 0);
2666df8bae1dSRodney W. Grimes 			needoutput = 1;
2667b8152ba7SAndre Oppermann 		} else if (!tcp_timer_active(tp, TT_PERSIST))
2668b8152ba7SAndre Oppermann 			tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
2669a0292f23SGarrett Wollman 
2670a0292f23SGarrett Wollman 		/*
2671a0292f23SGarrett Wollman 		 * If no data (only SYN) was ACK'd,
2672a0292f23SGarrett Wollman 		 *    skip rest of ACK processing.
2673a0292f23SGarrett Wollman 		 */
2674a0292f23SGarrett Wollman 		if (acked == 0)
2675a0292f23SGarrett Wollman 			goto step6;
2676a0292f23SGarrett Wollman 
2677df8bae1dSRodney W. Grimes 		/*
2678dbc42409SLawrence Stewart 		 * Let the congestion control algorithm update congestion
2679dbc42409SLawrence Stewart 		 * control related information. This typically means increasing
2680dbc42409SLawrence Stewart 		 * the congestion window.
2681df8bae1dSRodney W. Grimes 		 */
2682dbc42409SLawrence Stewart 		cc_ack_received(tp, th, CC_ACK);
2683dbc42409SLawrence Stewart 
26845905999bSRobert Watson 		SOCKBUF_LOCK(&so->so_snd);
2685df8bae1dSRodney W. Grimes 		if (acked > so->so_snd.sb_cc) {
268660ee3bb2SAndre Oppermann 			tp->snd_wnd -= so->so_snd.sb_cc;
2687c11a15bfSGleb Smirnoff 			mfree = sbcut_locked(&so->so_snd,
2688c11a15bfSGleb Smirnoff 			    (int)so->so_snd.sb_cc);
2689df8bae1dSRodney W. Grimes 			ourfinisacked = 1;
2690df8bae1dSRodney W. Grimes 		} else {
2691c11a15bfSGleb Smirnoff 			mfree = sbcut_locked(&so->so_snd, acked);
269260ee3bb2SAndre Oppermann 			tp->snd_wnd -= acked;
2693df8bae1dSRodney W. Grimes 			ourfinisacked = 0;
2694df8bae1dSRodney W. Grimes 		}
2695564aab1fSAndre Oppermann 		/* NB: sowwakeup_locked() does an implicit unlock. */
26961e4d7da7SRobert Watson 		sowwakeup_locked(so);
2697c11a15bfSGleb Smirnoff 		m_freem(mfree);
2698e8949f74SAndre Oppermann 		/* Detect una wraparound. */
2699dbc42409SLawrence Stewart 		if (!IN_RECOVERY(tp->t_flags) &&
27009d11646dSJeffrey Hsu 		    SEQ_GT(tp->snd_una, tp->snd_recover) &&
27019d11646dSJeffrey Hsu 		    SEQ_LEQ(th->th_ack, tp->snd_recover))
27029d11646dSJeffrey Hsu 			tp->snd_recover = th->th_ack - 1;
2703dbc42409SLawrence Stewart 		/* XXXLAS: Can this be moved up into cc_post_recovery? */
2704dbc42409SLawrence Stewart 		if (IN_RECOVERY(tp->t_flags) &&
270524cb0f22SLawrence Stewart 		    SEQ_GEQ(th->th_ack, tp->snd_recover)) {
2706dbc42409SLawrence Stewart 			EXIT_RECOVERY(tp->t_flags);
270724cb0f22SLawrence Stewart 		}
2708fb59c426SYoshinobu Inoue 		tp->snd_una = th->th_ack;
27093529149eSAndre Oppermann 		if (tp->t_flags & TF_SACK_PERMIT) {
27106d90faf3SPaul Saab 			if (SEQ_GT(tp->snd_una, tp->snd_recover))
27116d90faf3SPaul Saab 				tp->snd_recover = tp->snd_una;
27126d90faf3SPaul Saab 		}
2713df8bae1dSRodney W. Grimes 		if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2714df8bae1dSRodney W. Grimes 			tp->snd_nxt = tp->snd_una;
2715df8bae1dSRodney W. Grimes 
2716df8bae1dSRodney W. Grimes 		switch (tp->t_state) {
2717df8bae1dSRodney W. Grimes 
2718df8bae1dSRodney W. Grimes 		/*
2719df8bae1dSRodney W. Grimes 		 * In FIN_WAIT_1 STATE in addition to the processing
2720df8bae1dSRodney W. Grimes 		 * for the ESTABLISHED state if our FIN is now acknowledged
2721df8bae1dSRodney W. Grimes 		 * then enter FIN_WAIT_2.
2722df8bae1dSRodney W. Grimes 		 */
2723df8bae1dSRodney W. Grimes 		case TCPS_FIN_WAIT_1:
2724df8bae1dSRodney W. Grimes 			if (ourfinisacked) {
2725df8bae1dSRodney W. Grimes 				/*
2726df8bae1dSRodney W. Grimes 				 * If we can't receive any more
2727df8bae1dSRodney W. Grimes 				 * data, then closing user can proceed.
2728df8bae1dSRodney W. Grimes 				 * Starting the timer is contrary to the
2729df8bae1dSRodney W. Grimes 				 * specification, but if we don't get a FIN
2730df8bae1dSRodney W. Grimes 				 * we'll hang forever.
2731e8949f74SAndre Oppermann 				 *
2732e8949f74SAndre Oppermann 				 * XXXjl:
2733340c35deSJonathan Lemon 				 * we should release the tp also, and use a
2734340c35deSJonathan Lemon 				 * compressed state.
2735340c35deSJonathan Lemon 				 */
2736c0b99ffaSRobert Watson 				if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
273703e49181SSeigo Tanimura 					soisdisconnected(so);
27389077f387SGleb Smirnoff 					tcp_timer_activate(tp, TT_2MSL,
27399077f387SGleb Smirnoff 					    (tcp_fast_finwait2_recycle ?
27409077f387SGleb Smirnoff 					    tcp_finwait2_timeout :
27419077f387SGleb Smirnoff 					    TP_MAXIDLE(tp)));
27424cc20ab1SSeigo Tanimura 				}
274357f60867SMark Johnston 				tcp_state_change(tp, TCPS_FIN_WAIT_2);
2744df8bae1dSRodney W. Grimes 			}
2745df8bae1dSRodney W. Grimes 			break;
2746df8bae1dSRodney W. Grimes 
2747df8bae1dSRodney W. Grimes 		/*
2748df8bae1dSRodney W. Grimes 		 * In CLOSING STATE in addition to the processing for
2749df8bae1dSRodney W. Grimes 		 * the ESTABLISHED state if the ACK acknowledges our FIN
2750df8bae1dSRodney W. Grimes 		 * then enter the TIME-WAIT state, otherwise ignore
2751df8bae1dSRodney W. Grimes 		 * the segment.
2752df8bae1dSRodney W. Grimes 		 */
2753df8bae1dSRodney W. Grimes 		case TCPS_CLOSING:
2754df8bae1dSRodney W. Grimes 			if (ourfinisacked) {
2755252ca428SRobert Watson 				INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
275611a20fb8SJeffrey Hsu 				tcp_twstart(tp);
2757603724d3SBjoern A. Zeeb 				INP_INFO_WUNLOCK(&V_tcbinfo);
2758340c35deSJonathan Lemon 				m_freem(m);
2759679d9708SAndre Oppermann 				return;
2760df8bae1dSRodney W. Grimes 			}
2761df8bae1dSRodney W. Grimes 			break;
2762df8bae1dSRodney W. Grimes 
2763df8bae1dSRodney W. Grimes 		/*
2764df8bae1dSRodney W. Grimes 		 * In LAST_ACK, we may still be waiting for data to drain
2765df8bae1dSRodney W. Grimes 		 * and/or to be acked, as well as for the ack of our FIN.
2766df8bae1dSRodney W. Grimes 		 * If our FIN is now acknowledged, delete the TCB,
2767df8bae1dSRodney W. Grimes 		 * enter the closed state and return.
2768df8bae1dSRodney W. Grimes 		 */
2769df8bae1dSRodney W. Grimes 		case TCPS_LAST_ACK:
2770df8bae1dSRodney W. Grimes 			if (ourfinisacked) {
2771252ca428SRobert Watson 				INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2772df8bae1dSRodney W. Grimes 				tp = tcp_close(tp);
2773df8bae1dSRodney W. Grimes 				goto drop;
2774df8bae1dSRodney W. Grimes 			}
2775df8bae1dSRodney W. Grimes 			break;
2776df8bae1dSRodney W. Grimes 		}
2777df8bae1dSRodney W. Grimes 	}
2778df8bae1dSRodney W. Grimes 
2779df8bae1dSRodney W. Grimes step6:
27808501a69cSRobert Watson 	INP_WLOCK_ASSERT(tp->t_inpcb);
27817cfc6904SRobert Watson 
2782df8bae1dSRodney W. Grimes 	/*
278360ee3bb2SAndre Oppermann 	 * Update window information.
278460ee3bb2SAndre Oppermann 	 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2785df8bae1dSRodney W. Grimes 	 */
278660ee3bb2SAndre Oppermann 	if ((thflags & TH_ACK) &&
278760ee3bb2SAndre Oppermann 	    (SEQ_LT(tp->snd_wl1, th->th_seq) ||
278860ee3bb2SAndre Oppermann 	    (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) ||
278960ee3bb2SAndre Oppermann 	     (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
279060ee3bb2SAndre Oppermann 		/* keep track of pure window updates */
279160ee3bb2SAndre Oppermann 		if (tlen == 0 &&
279260ee3bb2SAndre Oppermann 		    tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)
279378b50714SRobert Watson 			TCPSTAT_INC(tcps_rcvwinupd);
2794df8bae1dSRodney W. Grimes 		tp->snd_wnd = tiwin;
279560ee3bb2SAndre Oppermann 		tp->snd_wl1 = th->th_seq;
279660ee3bb2SAndre Oppermann 		tp->snd_wl2 = th->th_ack;
2797df8bae1dSRodney W. Grimes 		if (tp->snd_wnd > tp->max_sndwnd)
2798df8bae1dSRodney W. Grimes 			tp->max_sndwnd = tp->snd_wnd;
279960ee3bb2SAndre Oppermann 		needoutput = 1;
2800df8bae1dSRodney W. Grimes 	}
2801df8bae1dSRodney W. Grimes 
2802df8bae1dSRodney W. Grimes 	/*
2803df8bae1dSRodney W. Grimes 	 * Process segments with URG.
2804df8bae1dSRodney W. Grimes 	 */
2805fb59c426SYoshinobu Inoue 	if ((thflags & TH_URG) && th->th_urp &&
2806df8bae1dSRodney W. Grimes 	    TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2807df8bae1dSRodney W. Grimes 		/*
2808df8bae1dSRodney W. Grimes 		 * This is a kludge, but if we receive and accept
2809df8bae1dSRodney W. Grimes 		 * random urgent pointers, we'll crash in
2810df8bae1dSRodney W. Grimes 		 * soreceive.  It's hard to imagine someone
2811df8bae1dSRodney W. Grimes 		 * actually wanting to send this much urgent data.
2812df8bae1dSRodney W. Grimes 		 */
281318ad5842SRobert Watson 		SOCKBUF_LOCK(&so->so_rcv);
2814fb59c426SYoshinobu Inoue 		if (th->th_urp + so->so_rcv.sb_cc > sb_max) {
2815fb59c426SYoshinobu Inoue 			th->th_urp = 0;			/* XXX */
2816fb59c426SYoshinobu Inoue 			thflags &= ~TH_URG;		/* XXX */
281718ad5842SRobert Watson 			SOCKBUF_UNLOCK(&so->so_rcv);	/* XXX */
2818df8bae1dSRodney W. Grimes 			goto dodata;			/* XXX */
2819df8bae1dSRodney W. Grimes 		}
2820df8bae1dSRodney W. Grimes 		/*
2821df8bae1dSRodney W. Grimes 		 * If this segment advances the known urgent pointer,
2822df8bae1dSRodney W. Grimes 		 * then mark the data stream.  This should not happen
2823df8bae1dSRodney W. Grimes 		 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2824df8bae1dSRodney W. Grimes 		 * a FIN has been received from the remote side.
2825df8bae1dSRodney W. Grimes 		 * In these states we ignore the URG.
2826df8bae1dSRodney W. Grimes 		 *
2827df8bae1dSRodney W. Grimes 		 * According to RFC961 (Assigned Protocols),
2828df8bae1dSRodney W. Grimes 		 * the urgent pointer points to the last octet
2829df8bae1dSRodney W. Grimes 		 * of urgent data.  We continue, however,
2830df8bae1dSRodney W. Grimes 		 * to consider it to indicate the first octet
2831df8bae1dSRodney W. Grimes 		 * of data past the urgent section as the original
2832df8bae1dSRodney W. Grimes 		 * spec states (in one of two places).
2833df8bae1dSRodney W. Grimes 		 */
2834fb59c426SYoshinobu Inoue 		if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) {
2835fb59c426SYoshinobu Inoue 			tp->rcv_up = th->th_seq + th->th_urp;
2836df8bae1dSRodney W. Grimes 			so->so_oobmark = so->so_rcv.sb_cc +
2837df8bae1dSRodney W. Grimes 			    (tp->rcv_up - tp->rcv_nxt) - 1;
2838927c5ceaSRobert Watson 			if (so->so_oobmark == 0)
2839c0b99ffaSRobert Watson 				so->so_rcv.sb_state |= SBS_RCVATMARK;
2840df8bae1dSRodney W. Grimes 			sohasoutofband(so);
2841df8bae1dSRodney W. Grimes 			tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2842df8bae1dSRodney W. Grimes 		}
284318ad5842SRobert Watson 		SOCKBUF_UNLOCK(&so->so_rcv);
2844df8bae1dSRodney W. Grimes 		/*
2845df8bae1dSRodney W. Grimes 		 * Remove out of band data so doesn't get presented to user.
2846df8bae1dSRodney W. Grimes 		 * This can happen independent of advancing the URG pointer,
2847df8bae1dSRodney W. Grimes 		 * but if two URG's are pending at once, some out-of-band
2848df8bae1dSRodney W. Grimes 		 * data may creep in... ick.
2849df8bae1dSRodney W. Grimes 		 */
285030613f56SJeffrey Hsu 		if (th->th_urp <= (u_long)tlen &&
285130613f56SJeffrey Hsu 		    !(so->so_options & SO_OOBINLINE)) {
285230613f56SJeffrey Hsu 			/* hdr drop is delayed */
285330613f56SJeffrey Hsu 			tcp_pulloutofband(so, th, m, drop_hdrlen);
285430613f56SJeffrey Hsu 		}
2855c068736aSJeffrey Hsu 	} else {
2856df8bae1dSRodney W. Grimes 		/*
2857df8bae1dSRodney W. Grimes 		 * If no out of band data is expected,
2858df8bae1dSRodney W. Grimes 		 * pull receive urgent pointer along
2859df8bae1dSRodney W. Grimes 		 * with the receive window.
2860df8bae1dSRodney W. Grimes 		 */
2861df8bae1dSRodney W. Grimes 		if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2862df8bae1dSRodney W. Grimes 			tp->rcv_up = tp->rcv_nxt;
2863c068736aSJeffrey Hsu 	}
2864df8bae1dSRodney W. Grimes dodata:							/* XXX */
28658501a69cSRobert Watson 	INP_WLOCK_ASSERT(tp->t_inpcb);
28667cfc6904SRobert Watson 
2867df8bae1dSRodney W. Grimes 	/*
2868df8bae1dSRodney W. Grimes 	 * Process the segment text, merging it into the TCP sequencing queue,
2869df8bae1dSRodney W. Grimes 	 * and arranging for acknowledgment of receipt if necessary.
2870df8bae1dSRodney W. Grimes 	 * This process logically involves adjusting tp->rcv_wnd as data
2871df8bae1dSRodney W. Grimes 	 * is presented to the user (this happens in tcp_usrreq.c,
2872df8bae1dSRodney W. Grimes 	 * case PRU_RCVD).  If a FIN has already been received on this
2873df8bae1dSRodney W. Grimes 	 * connection then we just ignore the text.
2874df8bae1dSRodney W. Grimes 	 */
2875fb59c426SYoshinobu Inoue 	if ((tlen || (thflags & TH_FIN)) &&
2876df8bae1dSRodney W. Grimes 	    TCPS_HAVERCVDFIN(tp->t_state) == 0) {
287769e03620SPaul Saab 		tcp_seq save_start = th->th_seq;
2878fb59c426SYoshinobu Inoue 		m_adj(m, drop_hdrlen);	/* delayed header drop */
2879e4b64281SJesper Skriver 		/*
2880c068736aSJeffrey Hsu 		 * Insert segment which includes th into TCP reassembly queue
2881c068736aSJeffrey Hsu 		 * with control block tp.  Set thflags to whether reassembly now
2882c068736aSJeffrey Hsu 		 * includes a segment with FIN.  This handles the common case
2883c068736aSJeffrey Hsu 		 * inline (segment is the next to be received on an established
2884c068736aSJeffrey Hsu 		 * connection, and the queue is empty), avoiding linkage into
2885c068736aSJeffrey Hsu 		 * and removal from the queue and repetition of various
2886c068736aSJeffrey Hsu 		 * conversions.
2887c068736aSJeffrey Hsu 		 * Set DELACK for segments received in order, but ack
2888c068736aSJeffrey Hsu 		 * immediately when segments are out of order (so
2889c068736aSJeffrey Hsu 		 * fast retransmit can work).
2890e4b64281SJesper Skriver 		 */
2891e407b67bSGleb Smirnoff 		if (th->th_seq == tp->rcv_nxt && tp->t_segq == NULL &&
2892e4b64281SJesper Skriver 		    TCPS_HAVEESTABLISHED(tp->t_state)) {
2893c1e5a6e5SAndre Oppermann 			if (DELAY_ACK(tp, tlen))
28943bfd6421SJonathan Lemon 				tp->t_flags |= TF_DELACK;
2895e4b64281SJesper Skriver 			else
2896e4b64281SJesper Skriver 				tp->t_flags |= TF_ACKNOW;
2897e4b64281SJesper Skriver 			tp->rcv_nxt += tlen;
2898e4b64281SJesper Skriver 			thflags = th->th_flags & TH_FIN;
289978b50714SRobert Watson 			TCPSTAT_INC(tcps_rcvpack);
290078b50714SRobert Watson 			TCPSTAT_ADD(tcps_rcvbyte, tlen);
2901e4b64281SJesper Skriver 			ND6_HINT(tp);
29021e4d7da7SRobert Watson 			SOCKBUF_LOCK(&so->so_rcv);
2903c0b99ffaSRobert Watson 			if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
2904c1c36a2cSMike Silbersack 				m_freem(m);
2905c1c36a2cSMike Silbersack 			else
29061e4d7da7SRobert Watson 				sbappendstream_locked(&so->so_rcv, m);
2907e8949f74SAndre Oppermann 			/* NB: sorwakeup_locked() does an implicit unlock. */
29081e4d7da7SRobert Watson 			sorwakeup_locked(so);
2909e4b64281SJesper Skriver 		} else {
2910e8949f74SAndre Oppermann 			/*
2911e8949f74SAndre Oppermann 			 * XXX: Due to the header drop above "th" is
2912e8949f74SAndre Oppermann 			 * theoretically invalid by now.  Fortunately
2913e8949f74SAndre Oppermann 			 * m_adj() doesn't actually frees any mbufs
2914e8949f74SAndre Oppermann 			 * when trimming from the head.
2915e8949f74SAndre Oppermann 			 */
2916e4b64281SJesper Skriver 			thflags = tcp_reass(tp, th, &tlen, m);
2917e4b64281SJesper Skriver 			tp->t_flags |= TF_ACKNOW;
2918e4b64281SJesper Skriver 		}
29193529149eSAndre Oppermann 		if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT))
2920f194524fSAndre Oppermann 			tcp_update_sack_list(tp, save_start, save_start + tlen);
2921302ce8d6SAndre Oppermann #if 0
2922df8bae1dSRodney W. Grimes 		/*
2923df8bae1dSRodney W. Grimes 		 * Note the amount of data that peer has sent into
2924df8bae1dSRodney W. Grimes 		 * our window, in order to estimate the sender's
2925df8bae1dSRodney W. Grimes 		 * buffer size.
2926302ce8d6SAndre Oppermann 		 * XXX: Unused.
2927df8bae1dSRodney W. Grimes 		 */
2928f701e30dSJohn Baldwin 		if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt))
2929df8bae1dSRodney W. Grimes 			len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
2930f701e30dSJohn Baldwin 		else
2931f701e30dSJohn Baldwin 			len = so->so_rcv.sb_hiwat;
2932302ce8d6SAndre Oppermann #endif
2933df8bae1dSRodney W. Grimes 	} else {
2934df8bae1dSRodney W. Grimes 		m_freem(m);
2935fb59c426SYoshinobu Inoue 		thflags &= ~TH_FIN;
2936df8bae1dSRodney W. Grimes 	}
2937df8bae1dSRodney W. Grimes 
2938df8bae1dSRodney W. Grimes 	/*
2939df8bae1dSRodney W. Grimes 	 * If FIN is received ACK the FIN and let the user know
2940df8bae1dSRodney W. Grimes 	 * that the connection is closing.
2941df8bae1dSRodney W. Grimes 	 */
2942fb59c426SYoshinobu Inoue 	if (thflags & TH_FIN) {
2943df8bae1dSRodney W. Grimes 		if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2944df8bae1dSRodney W. Grimes 			socantrcvmore(so);
2945a0292f23SGarrett Wollman 			/*
2946a0292f23SGarrett Wollman 			 * If connection is half-synchronized
2947d3eede9dSAndras Olah 			 * (ie NEEDSYN flag on) then delay ACK,
2948a0292f23SGarrett Wollman 			 * so it may be piggybacked when SYN is sent.
2949a0292f23SGarrett Wollman 			 * Otherwise, since we received a FIN then no
2950a0292f23SGarrett Wollman 			 * more input can be expected, send ACK now.
2951a0292f23SGarrett Wollman 			 */
29523bfd6421SJonathan Lemon 			if (tp->t_flags & TF_NEEDSYN)
29533bfd6421SJonathan Lemon 				tp->t_flags |= TF_DELACK;
2954a0292f23SGarrett Wollman 			else
2955df8bae1dSRodney W. Grimes 				tp->t_flags |= TF_ACKNOW;
2956df8bae1dSRodney W. Grimes 			tp->rcv_nxt++;
2957df8bae1dSRodney W. Grimes 		}
2958df8bae1dSRodney W. Grimes 		switch (tp->t_state) {
2959df8bae1dSRodney W. Grimes 
2960df8bae1dSRodney W. Grimes 		/*
2961df8bae1dSRodney W. Grimes 		 * In SYN_RECEIVED and ESTABLISHED STATES
2962df8bae1dSRodney W. Grimes 		 * enter the CLOSE_WAIT state.
2963df8bae1dSRodney W. Grimes 		 */
2964df8bae1dSRodney W. Grimes 		case TCPS_SYN_RECEIVED:
29659b8b58e0SJonathan Lemon 			tp->t_starttime = ticks;
29669b8b58e0SJonathan Lemon 			/* FALLTHROUGH */
2967df8bae1dSRodney W. Grimes 		case TCPS_ESTABLISHED:
296857f60867SMark Johnston 			tcp_state_change(tp, TCPS_CLOSE_WAIT);
2969df8bae1dSRodney W. Grimes 			break;
2970df8bae1dSRodney W. Grimes 
2971df8bae1dSRodney W. Grimes 		/*
2972df8bae1dSRodney W. Grimes 		 * If still in FIN_WAIT_1 STATE FIN has not been acked so
2973df8bae1dSRodney W. Grimes 		 * enter the CLOSING state.
2974df8bae1dSRodney W. Grimes 		 */
2975df8bae1dSRodney W. Grimes 		case TCPS_FIN_WAIT_1:
297657f60867SMark Johnston 			tcp_state_change(tp, TCPS_CLOSING);
2977df8bae1dSRodney W. Grimes 			break;
2978df8bae1dSRodney W. Grimes 
2979df8bae1dSRodney W. Grimes 		/*
2980df8bae1dSRodney W. Grimes 		 * In FIN_WAIT_2 state enter the TIME_WAIT state,
2981df8bae1dSRodney W. Grimes 		 * starting the time-wait timer, turning off the other
2982df8bae1dSRodney W. Grimes 		 * standard timers.
2983df8bae1dSRodney W. Grimes 		 */
2984df8bae1dSRodney W. Grimes 		case TCPS_FIN_WAIT_2:
2985252ca428SRobert Watson 			INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2986252ca428SRobert Watson 			KASSERT(ti_locked == TI_WLOCKED, ("%s: dodata "
2987252ca428SRobert Watson 			    "TCP_FIN_WAIT_2 ti_locked: %d", __func__,
2988252ca428SRobert Watson 			    ti_locked));
2989252ca428SRobert Watson 
2990340c35deSJonathan Lemon 			tcp_twstart(tp);
2991603724d3SBjoern A. Zeeb 			INP_INFO_WUNLOCK(&V_tcbinfo);
2992679d9708SAndre Oppermann 			return;
2993df8bae1dSRodney W. Grimes 		}
2994df8bae1dSRodney W. Grimes 	}
2995fa046d87SRobert Watson 	if (ti_locked == TI_WLOCKED)
2996603724d3SBjoern A. Zeeb 		INP_INFO_WUNLOCK(&V_tcbinfo);
2997252ca428SRobert Watson 	ti_locked = TI_UNLOCKED;
2998252ca428SRobert Watson 
2999610ee2f9SDavid Greenman #ifdef TCPDEBUG
30004cc20ab1SSeigo Tanimura 	if (so->so_options & SO_DEBUG)
3001fb59c426SYoshinobu Inoue 		tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
3002fb59c426SYoshinobu Inoue 			  &tcp_savetcp, 0);
3003610ee2f9SDavid Greenman #endif
3004df8bae1dSRodney W. Grimes 
3005df8bae1dSRodney W. Grimes 	/*
3006df8bae1dSRodney W. Grimes 	 * Return any desired output.
3007df8bae1dSRodney W. Grimes 	 */
3008df8bae1dSRodney W. Grimes 	if (needoutput || (tp->t_flags & TF_ACKNOW))
3009df8bae1dSRodney W. Grimes 		(void) tcp_output(tp);
30107792ea27SJeffrey Hsu 
3011a14c749fSJonathan Lemon check_delack:
3012252ca428SRobert Watson 	KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d",
3013252ca428SRobert Watson 	    __func__, ti_locked));
3014603724d3SBjoern A. Zeeb 	INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
30158501a69cSRobert Watson 	INP_WLOCK_ASSERT(tp->t_inpcb);
3016252ca428SRobert Watson 
3017a14c749fSJonathan Lemon 	if (tp->t_flags & TF_DELACK) {
30183bfd6421SJonathan Lemon 		tp->t_flags &= ~TF_DELACK;
3019b8152ba7SAndre Oppermann 		tcp_timer_activate(tp, TT_DELACK, tcp_delacktime);
30203bfd6421SJonathan Lemon 	}
30218501a69cSRobert Watson 	INP_WUNLOCK(tp->t_inpcb);
3022679d9708SAndre Oppermann 	return;
3023df8bae1dSRodney W. Grimes 
3024df8bae1dSRodney W. Grimes dropafterack:
3025df8bae1dSRodney W. Grimes 	/*
3026df8bae1dSRodney W. Grimes 	 * Generate an ACK dropping incoming segment if it occupies
3027df8bae1dSRodney W. Grimes 	 * sequence space, where the ACK reflects our state.
302880ab7c0eSGarrett Wollman 	 *
302980ab7c0eSGarrett Wollman 	 * We can now skip the test for the RST flag since all
303080ab7c0eSGarrett Wollman 	 * paths to this code happen after packets containing
303180ab7c0eSGarrett Wollman 	 * RST have been dropped.
303280ab7c0eSGarrett Wollman 	 *
303380ab7c0eSGarrett Wollman 	 * In the SYN-RECEIVED state, don't send an ACK unless the
303480ab7c0eSGarrett Wollman 	 * segment we received passes the SYN-RECEIVED ACK test.
303580ab7c0eSGarrett Wollman 	 * If it fails send a RST.  This breaks the loop in the
303680ab7c0eSGarrett Wollman 	 * "LAND" DoS attack, and also prevents an ACK storm
303780ab7c0eSGarrett Wollman 	 * between two listening ports that have been sent forged
303880ab7c0eSGarrett Wollman 	 * SYN segments, each with the source address of the other.
3039df8bae1dSRodney W. Grimes 	 */
3040fb59c426SYoshinobu Inoue 	if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
3041fb59c426SYoshinobu Inoue 	    (SEQ_GT(tp->snd_una, th->th_ack) ||
3042a57815efSBosko Milekic 	     SEQ_GT(th->th_ack, tp->snd_max)) ) {
3043a57815efSBosko Milekic 		rstreason = BANDLIM_RST_OPENPORT;
3044a57815efSBosko Milekic 		goto dropwithreset;
3045a57815efSBosko Milekic 	}
3046a0292f23SGarrett Wollman #ifdef TCPDEBUG
30474cc20ab1SSeigo Tanimura 	if (so->so_options & SO_DEBUG)
3048fb59c426SYoshinobu Inoue 		tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
3049fb59c426SYoshinobu Inoue 			  &tcp_savetcp, 0);
3050a0292f23SGarrett Wollman #endif
3051fa046d87SRobert Watson 	if (ti_locked == TI_WLOCKED)
3052603724d3SBjoern A. Zeeb 		INP_INFO_WUNLOCK(&V_tcbinfo);
3053252ca428SRobert Watson 	ti_locked = TI_UNLOCKED;
3054252ca428SRobert Watson 
3055df8bae1dSRodney W. Grimes 	tp->t_flags |= TF_ACKNOW;
3056df8bae1dSRodney W. Grimes 	(void) tcp_output(tp);
30578501a69cSRobert Watson 	INP_WUNLOCK(tp->t_inpcb);
3058d6915262SRobert Watson 	m_freem(m);
3059679d9708SAndre Oppermann 	return;
3060df8bae1dSRodney W. Grimes 
3061df8bae1dSRodney W. Grimes dropwithreset:
3062fa046d87SRobert Watson 	if (ti_locked == TI_WLOCKED)
3063dd8ac7f9SRobert Watson 		INP_INFO_WUNLOCK(&V_tcbinfo);
3064252ca428SRobert Watson 	ti_locked = TI_UNLOCKED;
3065a57815efSBosko Milekic 
3066a0ca0871SRobert Watson 	if (tp != NULL) {
3067302ce8d6SAndre Oppermann 		tcp_dropwithreset(m, th, tp, tlen, rstreason);
30688501a69cSRobert Watson 		INP_WUNLOCK(tp->t_inpcb);
3069dd8ac7f9SRobert Watson 	} else
3070a0ca0871SRobert Watson 		tcp_dropwithreset(m, th, NULL, tlen, rstreason);
3071679d9708SAndre Oppermann 	return;
3072df8bae1dSRodney W. Grimes 
3073df8bae1dSRodney W. Grimes drop:
3074fa046d87SRobert Watson 	if (ti_locked == TI_WLOCKED) {
3075252ca428SRobert Watson 		INP_INFO_WUNLOCK(&V_tcbinfo);
3076fa046d87SRobert Watson 		ti_locked = TI_UNLOCKED;
3077fa046d87SRobert Watson 	}
3078252ca428SRobert Watson #ifdef INVARIANTS
3079252ca428SRobert Watson 	else
3080252ca428SRobert Watson 		INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
3081252ca428SRobert Watson #endif
3082252ca428SRobert Watson 
3083df8bae1dSRodney W. Grimes 	/*
3084df8bae1dSRodney W. Grimes 	 * Drop space held by incoming segment and return.
3085df8bae1dSRodney W. Grimes 	 */
3086610ee2f9SDavid Greenman #ifdef TCPDEBUG
30871c53f806SRobert Watson 	if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
3088fb59c426SYoshinobu Inoue 		tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
3089fb59c426SYoshinobu Inoue 			  &tcp_savetcp, 0);
3090a0292f23SGarrett Wollman #endif
30911c53f806SRobert Watson 	if (tp != NULL)
30928501a69cSRobert Watson 		INP_WUNLOCK(tp->t_inpcb);
3093d6915262SRobert Watson 	m_freem(m);
3094302ce8d6SAndre Oppermann }
3095302ce8d6SAndre Oppermann 
3096302ce8d6SAndre Oppermann /*
30970ca3f933SAndre Oppermann  * Issue RST and make ACK acceptable to originator of segment.
30980ca3f933SAndre Oppermann  * The mbuf must still include the original packet header.
30990ca3f933SAndre Oppermann  * tp may be NULL.
3100302ce8d6SAndre Oppermann  */
3101302ce8d6SAndre Oppermann static void
3102302ce8d6SAndre Oppermann tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp,
3103302ce8d6SAndre Oppermann     int tlen, int rstreason)
3104302ce8d6SAndre Oppermann {
3105b287c6c7SBjoern A. Zeeb #ifdef INET
3106302ce8d6SAndre Oppermann 	struct ip *ip;
3107b287c6c7SBjoern A. Zeeb #endif
3108302ce8d6SAndre Oppermann #ifdef INET6
3109302ce8d6SAndre Oppermann 	struct ip6_hdr *ip6;
3110302ce8d6SAndre Oppermann #endif
31117a3244ccSRobert Watson 
31127a3244ccSRobert Watson 	if (tp != NULL) {
31138501a69cSRobert Watson 		INP_WLOCK_ASSERT(tp->t_inpcb);
31147a3244ccSRobert Watson 	}
31157a3244ccSRobert Watson 
31160ca3f933SAndre Oppermann 	/* Don't bother if destination was broadcast/multicast. */
3117302ce8d6SAndre Oppermann 	if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST))
3118302ce8d6SAndre Oppermann 		goto drop;
3119302ce8d6SAndre Oppermann #ifdef INET6
3120302ce8d6SAndre Oppermann 	if (mtod(m, struct ip *)->ip_v == 6) {
3121302ce8d6SAndre Oppermann 		ip6 = mtod(m, struct ip6_hdr *);
3122302ce8d6SAndre Oppermann 		if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
3123302ce8d6SAndre Oppermann 		    IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
3124302ce8d6SAndre Oppermann 			goto drop;
3125302ce8d6SAndre Oppermann 		/* IPv6 anycast check is done at tcp6_input() */
3126b287c6c7SBjoern A. Zeeb 	}
3127302ce8d6SAndre Oppermann #endif
3128b287c6c7SBjoern A. Zeeb #if defined(INET) && defined(INET6)
3129b287c6c7SBjoern A. Zeeb 	else
3130b287c6c7SBjoern A. Zeeb #endif
3131b287c6c7SBjoern A. Zeeb #ifdef INET
3132302ce8d6SAndre Oppermann 	{
3133302ce8d6SAndre Oppermann 		ip = mtod(m, struct ip *);
3134302ce8d6SAndre Oppermann 		if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
3135302ce8d6SAndre Oppermann 		    IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
3136302ce8d6SAndre Oppermann 		    ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
3137302ce8d6SAndre Oppermann 		    in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
3138302ce8d6SAndre Oppermann 			goto drop;
3139302ce8d6SAndre Oppermann 	}
3140b287c6c7SBjoern A. Zeeb #endif
3141302ce8d6SAndre Oppermann 
3142302ce8d6SAndre Oppermann 	/* Perform bandwidth limiting. */
3143302ce8d6SAndre Oppermann 	if (badport_bandlim(rstreason) < 0)
3144302ce8d6SAndre Oppermann 		goto drop;
3145302ce8d6SAndre Oppermann 
3146302ce8d6SAndre Oppermann 	/* tcp_respond consumes the mbuf chain. */
3147302ce8d6SAndre Oppermann 	if (th->th_flags & TH_ACK) {
3148302ce8d6SAndre Oppermann 		tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0,
3149302ce8d6SAndre Oppermann 		    th->th_ack, TH_RST);
3150302ce8d6SAndre Oppermann 	} else {
3151302ce8d6SAndre Oppermann 		if (th->th_flags & TH_SYN)
3152302ce8d6SAndre Oppermann 			tlen++;
3153302ce8d6SAndre Oppermann 		tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen,
3154302ce8d6SAndre Oppermann 		    (tcp_seq)0, TH_RST|TH_ACK);
3155302ce8d6SAndre Oppermann 	}
3156302ce8d6SAndre Oppermann 	return;
3157302ce8d6SAndre Oppermann drop:
3158302ce8d6SAndre Oppermann 	m_freem(m);
3159df8bae1dSRodney W. Grimes }
3160df8bae1dSRodney W. Grimes 
3161be2ac88cSJonathan Lemon /*
3162be2ac88cSJonathan Lemon  * Parse TCP options and place in tcpopt.
3163be2ac88cSJonathan Lemon  */
31640312fbe9SPoul-Henning Kamp static void
3165ad3f9ab3SAndre Oppermann tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags)
3166df8bae1dSRodney W. Grimes {
3167df8bae1dSRodney W. Grimes 	int opt, optlen;
3168df8bae1dSRodney W. Grimes 
3169be2ac88cSJonathan Lemon 	to->to_flags = 0;
3170df8bae1dSRodney W. Grimes 	for (; cnt > 0; cnt -= optlen, cp += optlen) {
3171df8bae1dSRodney W. Grimes 		opt = cp[0];
3172df8bae1dSRodney W. Grimes 		if (opt == TCPOPT_EOL)
3173df8bae1dSRodney W. Grimes 			break;
3174df8bae1dSRodney W. Grimes 		if (opt == TCPOPT_NOP)
3175df8bae1dSRodney W. Grimes 			optlen = 1;
3176df8bae1dSRodney W. Grimes 		else {
3177b474779fSJun-ichiro itojun Hagino 			if (cnt < 2)
3178b474779fSJun-ichiro itojun Hagino 				break;
3179df8bae1dSRodney W. Grimes 			optlen = cp[1];
3180b474779fSJun-ichiro itojun Hagino 			if (optlen < 2 || optlen > cnt)
3181df8bae1dSRodney W. Grimes 				break;
3182df8bae1dSRodney W. Grimes 		}
3183df8bae1dSRodney W. Grimes 		switch (opt) {
3184df8bae1dSRodney W. Grimes 		case TCPOPT_MAXSEG:
3185df8bae1dSRodney W. Grimes 			if (optlen != TCPOLEN_MAXSEG)
3186df8bae1dSRodney W. Grimes 				continue;
3187f72167f4SAndre Oppermann 			if (!(flags & TO_SYN))
3188df8bae1dSRodney W. Grimes 				continue;
3189be2ac88cSJonathan Lemon 			to->to_flags |= TOF_MSS;
3190be2ac88cSJonathan Lemon 			bcopy((char *)cp + 2,
3191be2ac88cSJonathan Lemon 			    (char *)&to->to_mss, sizeof(to->to_mss));
3192fd8e4ebcSMike Barcroft 			to->to_mss = ntohs(to->to_mss);
3193df8bae1dSRodney W. Grimes 			break;
3194df8bae1dSRodney W. Grimes 		case TCPOPT_WINDOW:
3195df8bae1dSRodney W. Grimes 			if (optlen != TCPOLEN_WINDOW)
3196df8bae1dSRodney W. Grimes 				continue;
3197f72167f4SAndre Oppermann 			if (!(flags & TO_SYN))
3198df8bae1dSRodney W. Grimes 				continue;
3199be2ac88cSJonathan Lemon 			to->to_flags |= TOF_SCALE;
320002a1a643SAndre Oppermann 			to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT);
3201df8bae1dSRodney W. Grimes 			break;
3202df8bae1dSRodney W. Grimes 		case TCPOPT_TIMESTAMP:
3203df8bae1dSRodney W. Grimes 			if (optlen != TCPOLEN_TIMESTAMP)
3204df8bae1dSRodney W. Grimes 				continue;
3205be2ac88cSJonathan Lemon 			to->to_flags |= TOF_TS;
3206a0292f23SGarrett Wollman 			bcopy((char *)cp + 2,
3207a0292f23SGarrett Wollman 			    (char *)&to->to_tsval, sizeof(to->to_tsval));
3208fd8e4ebcSMike Barcroft 			to->to_tsval = ntohl(to->to_tsval);
3209a0292f23SGarrett Wollman 			bcopy((char *)cp + 6,
3210a0292f23SGarrett Wollman 			    (char *)&to->to_tsecr, sizeof(to->to_tsecr));
3211fd8e4ebcSMike Barcroft 			to->to_tsecr = ntohl(to->to_tsecr);
3212df8bae1dSRodney W. Grimes 			break;
32131cfd4b53SBruce M Simpson #ifdef TCP_SIGNATURE
32141cfd4b53SBruce M Simpson 		/*
32151cfd4b53SBruce M Simpson 		 * XXX In order to reply to a host which has set the
32161cfd4b53SBruce M Simpson 		 * TCP_SIGNATURE option in its initial SYN, we have to
32171cfd4b53SBruce M Simpson 		 * record the fact that the option was observed here
32181cfd4b53SBruce M Simpson 		 * for the syncache code to perform the correct response.
32191cfd4b53SBruce M Simpson 		 */
32201cfd4b53SBruce M Simpson 		case TCPOPT_SIGNATURE:
32211cfd4b53SBruce M Simpson 			if (optlen != TCPOLEN_SIGNATURE)
32221cfd4b53SBruce M Simpson 				continue;
3223df47e437SAndre Oppermann 			to->to_flags |= TOF_SIGNATURE;
3224df47e437SAndre Oppermann 			to->to_signature = cp + 2;
32251cfd4b53SBruce M Simpson 			break;
3226265ed012SBruce M Simpson #endif
32276d90faf3SPaul Saab 		case TCPOPT_SACK_PERMITTED:
3228f72167f4SAndre Oppermann 			if (optlen != TCPOLEN_SACK_PERMITTED)
32296d90faf3SPaul Saab 				continue;
3230f72167f4SAndre Oppermann 			if (!(flags & TO_SYN))
3231f72167f4SAndre Oppermann 				continue;
3232603724d3SBjoern A. Zeeb 			if (!V_tcp_do_sack)
3233f72167f4SAndre Oppermann 				continue;
3234fc30a251SAndre Oppermann 			to->to_flags |= TOF_SACKPERM;
32356d90faf3SPaul Saab 			break;
32366d90faf3SPaul Saab 		case TCPOPT_SACK:
32375a53ca16SPaul Saab 			if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0)
32386d90faf3SPaul Saab 				continue;
3239b728e902SAndre Oppermann 			if (flags & TO_SYN)
3240b728e902SAndre Oppermann 				continue;
3241fc30a251SAndre Oppermann 			to->to_flags |= TOF_SACK;
32425a53ca16SPaul Saab 			to->to_nsacks = (optlen - 2) / TCPOLEN_SACK;
32435a53ca16SPaul Saab 			to->to_sacks = cp + 2;
324478b50714SRobert Watson 			TCPSTAT_INC(tcps_sack_rcv_blocks);
32456d90faf3SPaul Saab 			break;
3246be2ac88cSJonathan Lemon 		default:
3247be2ac88cSJonathan Lemon 			continue;
3248df8bae1dSRodney W. Grimes 		}
3249df8bae1dSRodney W. Grimes 	}
3250df8bae1dSRodney W. Grimes }
3251df8bae1dSRodney W. Grimes 
3252df8bae1dSRodney W. Grimes /*
3253df8bae1dSRodney W. Grimes  * Pull out of band byte out of a segment so
3254df8bae1dSRodney W. Grimes  * it doesn't appear in the user's data queue.
3255df8bae1dSRodney W. Grimes  * It is still reflected in the segment length for
3256df8bae1dSRodney W. Grimes  * sequencing purposes.
3257df8bae1dSRodney W. Grimes  */
32580312fbe9SPoul-Henning Kamp static void
3259ad3f9ab3SAndre Oppermann tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m,
3260ad3f9ab3SAndre Oppermann     int off)
3261df8bae1dSRodney W. Grimes {
3262fb59c426SYoshinobu Inoue 	int cnt = off + th->th_urp - 1;
3263df8bae1dSRodney W. Grimes 
3264df8bae1dSRodney W. Grimes 	while (cnt >= 0) {
3265df8bae1dSRodney W. Grimes 		if (m->m_len > cnt) {
3266df8bae1dSRodney W. Grimes 			char *cp = mtod(m, caddr_t) + cnt;
3267df8bae1dSRodney W. Grimes 			struct tcpcb *tp = sototcpcb(so);
3268df8bae1dSRodney W. Grimes 
32698501a69cSRobert Watson 			INP_WLOCK_ASSERT(tp->t_inpcb);
32707a3244ccSRobert Watson 
3271df8bae1dSRodney W. Grimes 			tp->t_iobc = *cp;
3272df8bae1dSRodney W. Grimes 			tp->t_oobflags |= TCPOOB_HAVEDATA;
3273df8bae1dSRodney W. Grimes 			bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1));
3274df8bae1dSRodney W. Grimes 			m->m_len--;
327569a34685SYoshinobu Inoue 			if (m->m_flags & M_PKTHDR)
327669a34685SYoshinobu Inoue 				m->m_pkthdr.len--;
3277df8bae1dSRodney W. Grimes 			return;
3278df8bae1dSRodney W. Grimes 		}
3279df8bae1dSRodney W. Grimes 		cnt -= m->m_len;
3280df8bae1dSRodney W. Grimes 		m = m->m_next;
32814dfdffe9SAndre Oppermann 		if (m == NULL)
3282df8bae1dSRodney W. Grimes 			break;
3283df8bae1dSRodney W. Grimes 	}
3284df8bae1dSRodney W. Grimes 	panic("tcp_pulloutofband");
3285df8bae1dSRodney W. Grimes }
3286df8bae1dSRodney W. Grimes 
3287df8bae1dSRodney W. Grimes /*
3288df8bae1dSRodney W. Grimes  * Collect new round-trip time estimate
3289df8bae1dSRodney W. Grimes  * and update averages and current timeout.
3290df8bae1dSRodney W. Grimes  */
32910312fbe9SPoul-Henning Kamp static void
3292ad3f9ab3SAndre Oppermann tcp_xmit_timer(struct tcpcb *tp, int rtt)
3293df8bae1dSRodney W. Grimes {
3294ad3f9ab3SAndre Oppermann 	int delta;
3295233e8c18SGarrett Wollman 
32968501a69cSRobert Watson 	INP_WLOCK_ASSERT(tp->t_inpcb);
32972be3bf22SRobert Watson 
329878b50714SRobert Watson 	TCPSTAT_INC(tcps_rttupdated);
3299233e8c18SGarrett Wollman 	tp->t_rttupdated++;
3300233e8c18SGarrett Wollman 	if (tp->t_srtt != 0) {
3301233e8c18SGarrett Wollman 		/*
3302233e8c18SGarrett Wollman 		 * srtt is stored as fixed point with 5 bits after the
3303233e8c18SGarrett Wollman 		 * binary point (i.e., scaled by 8).  The following magic
3304233e8c18SGarrett Wollman 		 * is equivalent to the smoothing algorithm in rfc793 with
3305233e8c18SGarrett Wollman 		 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
3306233e8c18SGarrett Wollman 		 * point).  Adjust rtt to origin 0.
3307233e8c18SGarrett Wollman 		 */
3308233e8c18SGarrett Wollman 		delta = ((rtt - 1) << TCP_DELTA_SHIFT)
3309233e8c18SGarrett Wollman 			- (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
3310233e8c18SGarrett Wollman 
3311233e8c18SGarrett Wollman 		if ((tp->t_srtt += delta) <= 0)
3312233e8c18SGarrett Wollman 			tp->t_srtt = 1;
3313233e8c18SGarrett Wollman 
3314233e8c18SGarrett Wollman 		/*
3315233e8c18SGarrett Wollman 		 * We accumulate a smoothed rtt variance (actually, a
3316233e8c18SGarrett Wollman 		 * smoothed mean difference), then set the retransmit
3317233e8c18SGarrett Wollman 		 * timer to smoothed rtt + 4 times the smoothed variance.
3318233e8c18SGarrett Wollman 		 * rttvar is stored as fixed point with 4 bits after the
3319233e8c18SGarrett Wollman 		 * binary point (scaled by 16).  The following is
3320233e8c18SGarrett Wollman 		 * equivalent to rfc793 smoothing with an alpha of .75
3321233e8c18SGarrett Wollman 		 * (rttvar = rttvar*3/4 + |delta| / 4).  This replaces
3322233e8c18SGarrett Wollman 		 * rfc793's wired-in beta.
3323233e8c18SGarrett Wollman 		 */
3324233e8c18SGarrett Wollman 		if (delta < 0)
3325233e8c18SGarrett Wollman 			delta = -delta;
3326233e8c18SGarrett Wollman 		delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
3327233e8c18SGarrett Wollman 		if ((tp->t_rttvar += delta) <= 0)
3328233e8c18SGarrett Wollman 			tp->t_rttvar = 1;
33291fcc99b5SMatthew Dillon 		if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
33301fcc99b5SMatthew Dillon 		    tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
3331233e8c18SGarrett Wollman 	} else {
3332233e8c18SGarrett Wollman 		/*
3333233e8c18SGarrett Wollman 		 * No rtt measurement yet - use the unsmoothed rtt.
3334233e8c18SGarrett Wollman 		 * Set the variance to half the rtt (so our first
3335233e8c18SGarrett Wollman 		 * retransmit happens at 3*rtt).
3336233e8c18SGarrett Wollman 		 */
3337233e8c18SGarrett Wollman 		tp->t_srtt = rtt << TCP_RTT_SHIFT;
3338233e8c18SGarrett Wollman 		tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
33391fcc99b5SMatthew Dillon 		tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
3340233e8c18SGarrett Wollman 	}
33419b8b58e0SJonathan Lemon 	tp->t_rtttime = 0;
3342df8bae1dSRodney W. Grimes 	tp->t_rxtshift = 0;
3343df8bae1dSRodney W. Grimes 
3344df8bae1dSRodney W. Grimes 	/*
3345df8bae1dSRodney W. Grimes 	 * the retransmit should happen at rtt + 4 * rttvar.
3346df8bae1dSRodney W. Grimes 	 * Because of the way we do the smoothing, srtt and rttvar
3347df8bae1dSRodney W. Grimes 	 * will each average +1/2 tick of bias.  When we compute
3348df8bae1dSRodney W. Grimes 	 * the retransmit timer, we want 1/2 tick of rounding and
3349df8bae1dSRodney W. Grimes 	 * 1 extra tick because of +-1/2 tick uncertainty in the
3350df8bae1dSRodney W. Grimes 	 * firing of the timer.  The bias will give us exactly the
3351df8bae1dSRodney W. Grimes 	 * 1.5 tick we need.  But, because the bias is
3352df8bae1dSRodney W. Grimes 	 * statistical, we have to test that we don't drop below
3353df8bae1dSRodney W. Grimes 	 * the minimum feasible timer (which is 2 ticks).
3354df8bae1dSRodney W. Grimes 	 */
3355233e8c18SGarrett Wollman 	TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
33569e2874b0SGarrett Wollman 		      max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
3357df8bae1dSRodney W. Grimes 
3358df8bae1dSRodney W. Grimes 	/*
3359df8bae1dSRodney W. Grimes 	 * We received an ack for a packet that wasn't retransmitted;
3360df8bae1dSRodney W. Grimes 	 * it is probably safe to discard any error indications we've
3361df8bae1dSRodney W. Grimes 	 * received recently.  This isn't quite right, but close enough
3362df8bae1dSRodney W. Grimes 	 * for now (a route might have failed after we sent a segment,
3363df8bae1dSRodney W. Grimes 	 * and the return path might not be symmetrical).
3364df8bae1dSRodney W. Grimes 	 */
3365df8bae1dSRodney W. Grimes 	tp->t_softerror = 0;
3366df8bae1dSRodney W. Grimes }
3367df8bae1dSRodney W. Grimes 
3368df8bae1dSRodney W. Grimes /*
3369df8bae1dSRodney W. Grimes  * Determine a reasonable value for maxseg size.
3370df8bae1dSRodney W. Grimes  * If the route is known, check route for mtu.
33714faaea55SAndre Oppermann  * If none, use an mss that can be handled on the outgoing interface
33724faaea55SAndre Oppermann  * without forcing IP to fragment.  If no route is found, route has no mtu,
3373df8bae1dSRodney W. Grimes  * or the destination isn't local, use a default, hopefully conservative
3374df8bae1dSRodney W. Grimes  * size (usually 512 or the default IP max size, but no more than the mtu
3375df8bae1dSRodney W. Grimes  * of the interface), as we can't discover anything about intervening
3376df8bae1dSRodney W. Grimes  * gateways or networks.  We also initialize the congestion/slow start
3377df8bae1dSRodney W. Grimes  * window to be a single segment if the destination isn't local.
3378df8bae1dSRodney W. Grimes  * While looking at the routing entry, we also initialize other path-dependent
3379df8bae1dSRodney W. Grimes  * parameters from pre-set or cached values in the routing entry.
3380a0292f23SGarrett Wollman  *
3381a0292f23SGarrett Wollman  * Also take into account the space needed for options that we
3382a0292f23SGarrett Wollman  * send regularly.  Make maxseg shorter by that amount to assure
3383a0292f23SGarrett Wollman  * that we can send maxseg amount of data even when the options
3384a0292f23SGarrett Wollman  * are present.  Store the upper limit of the length of options plus
3385a0292f23SGarrett Wollman  * data in maxopd.
3386a0292f23SGarrett Wollman  *
338797d8d152SAndre Oppermann  * NOTE that this routine is only called when we process an incoming
3388ef341ee1SGleb Smirnoff  * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS
3389ef341ee1SGleb Smirnoff  * settings are handled in tcp_mssopt().
3390df8bae1dSRodney W. Grimes  */
3391a0292f23SGarrett Wollman void
3392ef341ee1SGleb Smirnoff tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer,
33933c914c54SAndre Oppermann     struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap)
3394df8bae1dSRodney W. Grimes {
3395b287c6c7SBjoern A. Zeeb 	int mss = 0;
3396b287c6c7SBjoern A. Zeeb 	u_long maxmtu = 0;
3397c068736aSJeffrey Hsu 	struct inpcb *inp = tp->t_inpcb;
339897d8d152SAndre Oppermann 	struct hc_metrics_lite metrics;
3399ef341ee1SGleb Smirnoff 	int origoffer;
3400fb59c426SYoshinobu Inoue #ifdef INET6
3401c068736aSJeffrey Hsu 	int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
3402c068736aSJeffrey Hsu 	size_t min_protoh = isipv6 ?
3403c068736aSJeffrey Hsu 			    sizeof (struct ip6_hdr) + sizeof (struct tcphdr) :
3404c068736aSJeffrey Hsu 			    sizeof (struct tcpiphdr);
3405c068736aSJeffrey Hsu #else
3406c068736aSJeffrey Hsu 	const size_t min_protoh = sizeof(struct tcpiphdr);
3407fb59c426SYoshinobu Inoue #endif
3408df8bae1dSRodney W. Grimes 
34098501a69cSRobert Watson 	INP_WLOCK_ASSERT(tp->t_inpcb);
34107a3244ccSRobert Watson 
3411ef341ee1SGleb Smirnoff 	if (mtuoffer != -1) {
3412ef341ee1SGleb Smirnoff 		KASSERT(offer == -1, ("%s: conflict", __func__));
3413ef341ee1SGleb Smirnoff 		offer = mtuoffer - min_protoh;
3414ef341ee1SGleb Smirnoff 	}
3415ef341ee1SGleb Smirnoff 	origoffer = offer;
3416ef341ee1SGleb Smirnoff 
3417e8949f74SAndre Oppermann 	/* Initialize. */
341897d8d152SAndre Oppermann #ifdef INET6
341997d8d152SAndre Oppermann 	if (isipv6) {
34203c914c54SAndre Oppermann 		maxmtu = tcp_maxmtu6(&inp->inp_inc, cap);
3421603724d3SBjoern A. Zeeb 		tp->t_maxopd = tp->t_maxseg = V_tcp_v6mssdflt;
3422b287c6c7SBjoern A. Zeeb 	}
342397d8d152SAndre Oppermann #endif
3424b287c6c7SBjoern A. Zeeb #if defined(INET) && defined(INET6)
3425b287c6c7SBjoern A. Zeeb 	else
3426b287c6c7SBjoern A. Zeeb #endif
3427b287c6c7SBjoern A. Zeeb #ifdef INET
342897d8d152SAndre Oppermann 	{
34293c914c54SAndre Oppermann 		maxmtu = tcp_maxmtu(&inp->inp_inc, cap);
3430603724d3SBjoern A. Zeeb 		tp->t_maxopd = tp->t_maxseg = V_tcp_mssdflt;
3431df8bae1dSRodney W. Grimes 	}
3432b287c6c7SBjoern A. Zeeb #endif
3433df8bae1dSRodney W. Grimes 
343497d8d152SAndre Oppermann 	/*
3435e8949f74SAndre Oppermann 	 * No route to sender, stay with default mss and return.
343697d8d152SAndre Oppermann 	 */
34376f01cac6SBjoern A. Zeeb 	if (maxmtu == 0) {
34386f01cac6SBjoern A. Zeeb 		/*
34398e5c87f4SBjoern A. Zeeb 		 * In case we return early we need to initialize metrics
34406f01cac6SBjoern A. Zeeb 		 * to a defined state as tcp_hc_get() would do for us
34416f01cac6SBjoern A. Zeeb 		 * if there was no cache hit.
34426f01cac6SBjoern A. Zeeb 		 */
34436f01cac6SBjoern A. Zeeb 		if (metricptr != NULL)
34446f01cac6SBjoern A. Zeeb 			bzero(metricptr, sizeof(struct hc_metrics_lite));
344597d8d152SAndre Oppermann 		return;
34466f01cac6SBjoern A. Zeeb 	}
344797d8d152SAndre Oppermann 
3448e8949f74SAndre Oppermann 	/* What have we got? */
344997d8d152SAndre Oppermann 	switch (offer) {
345097d8d152SAndre Oppermann 		case 0:
345197d8d152SAndre Oppermann 			/*
345297d8d152SAndre Oppermann 			 * Offer == 0 means that there was no MSS on the SYN
3453c3b02504SBjoern A. Zeeb 			 * segment, in this case we use tcp_mssdflt as
3454c3b02504SBjoern A. Zeeb 			 * already assigned to t_maxopd above.
345597d8d152SAndre Oppermann 			 */
3456c3b02504SBjoern A. Zeeb 			offer = tp->t_maxopd;
345797d8d152SAndre Oppermann 			break;
345897d8d152SAndre Oppermann 
345997d8d152SAndre Oppermann 		case -1:
3460a0292f23SGarrett Wollman 			/*
3461c94c54e4SAndre Oppermann 			 * Offer == -1 means that we didn't receive SYN yet.
3462a0292f23SGarrett Wollman 			 */
346397d8d152SAndre Oppermann 			/* FALLTHROUGH */
346497d8d152SAndre Oppermann 
346597d8d152SAndre Oppermann 		default:
3466a0292f23SGarrett Wollman 			/*
346753369ac9SAndre Oppermann 			 * Prevent DoS attack with too small MSS. Round up
346853369ac9SAndre Oppermann 			 * to at least minmss.
346953369ac9SAndre Oppermann 			 */
3470603724d3SBjoern A. Zeeb 			offer = max(offer, V_tcp_minmss);
347197d8d152SAndre Oppermann 	}
3472a0292f23SGarrett Wollman 
3473df8bae1dSRodney W. Grimes 	/*
3474e8949f74SAndre Oppermann 	 * rmx information is now retrieved from tcp_hostcache.
3475df8bae1dSRodney W. Grimes 	 */
347697d8d152SAndre Oppermann 	tcp_hc_get(&inp->inp_inc, &metrics);
34773cee92e0SBjoern A. Zeeb 	if (metricptr != NULL)
34783cee92e0SBjoern A. Zeeb 		bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite));
347997d8d152SAndre Oppermann 
3480df8bae1dSRodney W. Grimes 	/*
3481cc412412SHiren Panchasara 	 * If there's a discovered mtu in tcp hostcache, use it.
3482cc412412SHiren Panchasara 	 * Else, use the link mtu.
3483df8bae1dSRodney W. Grimes 	 */
348497d8d152SAndre Oppermann 	if (metrics.rmx_mtu)
34852d166c02SAndre Oppermann 		mss = min(metrics.rmx_mtu, maxmtu) - min_protoh;
3486c068736aSJeffrey Hsu 	else {
348731b3783cSHajimu UMEMOTO #ifdef INET6
3488fb59c426SYoshinobu Inoue 		if (isipv6) {
348997d8d152SAndre Oppermann 			mss = maxmtu - min_protoh;
3490603724d3SBjoern A. Zeeb 			if (!V_path_mtu_discovery &&
349197d8d152SAndre Oppermann 			    !in6_localaddr(&inp->in6p_faddr))
3492603724d3SBjoern A. Zeeb 				mss = min(mss, V_tcp_v6mssdflt);
3493b287c6c7SBjoern A. Zeeb 		}
3494b3399803SHajimu UMEMOTO #endif
3495b287c6c7SBjoern A. Zeeb #if defined(INET) && defined(INET6)
3496b287c6c7SBjoern A. Zeeb 		else
3497b287c6c7SBjoern A. Zeeb #endif
3498b287c6c7SBjoern A. Zeeb #ifdef INET
349997d8d152SAndre Oppermann 		{
350097d8d152SAndre Oppermann 			mss = maxmtu - min_protoh;
3501603724d3SBjoern A. Zeeb 			if (!V_path_mtu_discovery &&
350297d8d152SAndre Oppermann 			    !in_localaddr(inp->inp_faddr))
3503603724d3SBjoern A. Zeeb 				mss = min(mss, V_tcp_mssdflt);
3504a0292f23SGarrett Wollman 		}
3505b287c6c7SBjoern A. Zeeb #endif
35063cee92e0SBjoern A. Zeeb 		/*
35073cee92e0SBjoern A. Zeeb 		 * XXX - The above conditional (mss = maxmtu - min_protoh)
35083cee92e0SBjoern A. Zeeb 		 * probably violates the TCP spec.
35093cee92e0SBjoern A. Zeeb 		 * The problem is that, since we don't know the
35103cee92e0SBjoern A. Zeeb 		 * other end's MSS, we are supposed to use a conservative
35113cee92e0SBjoern A. Zeeb 		 * default.  But, if we do that, then MTU discovery will
35123cee92e0SBjoern A. Zeeb 		 * never actually take place, because the conservative
35133cee92e0SBjoern A. Zeeb 		 * default is much less than the MTUs typically seen
35143cee92e0SBjoern A. Zeeb 		 * on the Internet today.  For the moment, we'll sweep
35153cee92e0SBjoern A. Zeeb 		 * this under the carpet.
35163cee92e0SBjoern A. Zeeb 		 *
35173cee92e0SBjoern A. Zeeb 		 * The conservative default might not actually be a problem
35183cee92e0SBjoern A. Zeeb 		 * if the only case this occurs is when sending an initial
35193cee92e0SBjoern A. Zeeb 		 * SYN with options and data to a host we've never talked
35203cee92e0SBjoern A. Zeeb 		 * to before.  Then, they will reply with an MSS value which
35213cee92e0SBjoern A. Zeeb 		 * will get recorded and the new parameters should get
35223cee92e0SBjoern A. Zeeb 		 * recomputed.  For Further Study.
35233cee92e0SBjoern A. Zeeb 		 */
352497d8d152SAndre Oppermann 	}
3525a0292f23SGarrett Wollman 	mss = min(mss, offer);
352697d8d152SAndre Oppermann 
3527a0292f23SGarrett Wollman 	/*
35283cee92e0SBjoern A. Zeeb 	 * Sanity check: make sure that maxopd will be large
35293cee92e0SBjoern A. Zeeb 	 * enough to allow some data on segments even if the
35303cee92e0SBjoern A. Zeeb 	 * all the option space is used (40bytes).  Otherwise
35313cee92e0SBjoern A. Zeeb 	 * funny things may happen in tcp_output.
35323cee92e0SBjoern A. Zeeb 	 */
35333cee92e0SBjoern A. Zeeb 	mss = max(mss, 64);
35343cee92e0SBjoern A. Zeeb 
35353cee92e0SBjoern A. Zeeb 	/*
3536a0292f23SGarrett Wollman 	 * maxopd stores the maximum length of data AND options
3537a0292f23SGarrett Wollman 	 * in a segment; maxseg is the amount of data in a normal
3538a0292f23SGarrett Wollman 	 * segment.  We need to store this value (maxopd) apart
3539a0292f23SGarrett Wollman 	 * from maxseg, because now every segment carries options
3540a0292f23SGarrett Wollman 	 * and thus we normally have somewhat less data in segments.
3541a0292f23SGarrett Wollman 	 */
3542a0292f23SGarrett Wollman 	tp->t_maxopd = mss;
3543a0292f23SGarrett Wollman 
3544a0292f23SGarrett Wollman 	/*
3545e8949f74SAndre Oppermann 	 * origoffer==-1 indicates that no segments were received yet.
3546c94c54e4SAndre Oppermann 	 * In this case we just guess.
3547a0292f23SGarrett Wollman 	 */
3548a0292f23SGarrett Wollman 	if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
3549a0292f23SGarrett Wollman 	    (origoffer == -1 ||
3550a0292f23SGarrett Wollman 	     (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
3551a0292f23SGarrett Wollman 		mss -= TCPOLEN_TSTAMP_APPA;
3552a0292f23SGarrett Wollman 
355397d8d152SAndre Oppermann 	tp->t_maxseg = mss;
35543cee92e0SBjoern A. Zeeb }
35553cee92e0SBjoern A. Zeeb 
35563cee92e0SBjoern A. Zeeb void
35573cee92e0SBjoern A. Zeeb tcp_mss(struct tcpcb *tp, int offer)
35583cee92e0SBjoern A. Zeeb {
3559dbc42409SLawrence Stewart 	int mss;
35603cee92e0SBjoern A. Zeeb 	u_long bufsize;
35613cee92e0SBjoern A. Zeeb 	struct inpcb *inp;
35623cee92e0SBjoern A. Zeeb 	struct socket *so;
35633cee92e0SBjoern A. Zeeb 	struct hc_metrics_lite metrics;
35643c914c54SAndre Oppermann 	struct tcp_ifcap cap;
3565dbc42409SLawrence Stewart 
35663cee92e0SBjoern A. Zeeb 	KASSERT(tp != NULL, ("%s: tp == NULL", __func__));
35673cee92e0SBjoern A. Zeeb 
35683c914c54SAndre Oppermann 	bzero(&cap, sizeof(cap));
35693c914c54SAndre Oppermann 	tcp_mss_update(tp, offer, -1, &metrics, &cap);
35703cee92e0SBjoern A. Zeeb 
35713cee92e0SBjoern A. Zeeb 	mss = tp->t_maxseg;
35723cee92e0SBjoern A. Zeeb 	inp = tp->t_inpcb;
357397d8d152SAndre Oppermann 
3574df8bae1dSRodney W. Grimes 	/*
357597d8d152SAndre Oppermann 	 * If there's a pipesize, change the socket buffer to that size,
357697d8d152SAndre Oppermann 	 * don't change if sb_hiwat is different than default (then it
357797d8d152SAndre Oppermann 	 * has been changed on purpose with setsockopt).
357897d8d152SAndre Oppermann 	 * Make the socket buffers an integral number of mss units;
357997d8d152SAndre Oppermann 	 * if the mss is larger than the socket buffer, decrease the mss.
3580df8bae1dSRodney W. Grimes 	 */
3581c3b02504SBjoern A. Zeeb 	so = inp->inp_socket;
35823f11a2f3SRobert Watson 	SOCKBUF_LOCK(&so->so_snd);
3583e233e2acSAndre Oppermann 	if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe)
358497d8d152SAndre Oppermann 		bufsize = metrics.rmx_sendpipe;
358597d8d152SAndre Oppermann 	else
3586df8bae1dSRodney W. Grimes 		bufsize = so->so_snd.sb_hiwat;
3587df8bae1dSRodney W. Grimes 	if (bufsize < mss)
3588df8bae1dSRodney W. Grimes 		mss = bufsize;
3589df8bae1dSRodney W. Grimes 	else {
3590df8bae1dSRodney W. Grimes 		bufsize = roundup(bufsize, mss);
3591df8bae1dSRodney W. Grimes 		if (bufsize > sb_max)
3592df8bae1dSRodney W. Grimes 			bufsize = sb_max;
359388c39af3SRuslan Ermilov 		if (bufsize > so->so_snd.sb_hiwat)
35943f11a2f3SRobert Watson 			(void)sbreserve_locked(&so->so_snd, bufsize, so, NULL);
3595df8bae1dSRodney W. Grimes 	}
35963f11a2f3SRobert Watson 	SOCKBUF_UNLOCK(&so->so_snd);
3597df8bae1dSRodney W. Grimes 	tp->t_maxseg = mss;
3598df8bae1dSRodney W. Grimes 
35993f11a2f3SRobert Watson 	SOCKBUF_LOCK(&so->so_rcv);
3600e233e2acSAndre Oppermann 	if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe)
360197d8d152SAndre Oppermann 		bufsize = metrics.rmx_recvpipe;
360297d8d152SAndre Oppermann 	else
3603df8bae1dSRodney W. Grimes 		bufsize = so->so_rcv.sb_hiwat;
3604df8bae1dSRodney W. Grimes 	if (bufsize > mss) {
3605df8bae1dSRodney W. Grimes 		bufsize = roundup(bufsize, mss);
3606df8bae1dSRodney W. Grimes 		if (bufsize > sb_max)
3607df8bae1dSRodney W. Grimes 			bufsize = sb_max;
360888c39af3SRuslan Ermilov 		if (bufsize > so->so_rcv.sb_hiwat)
36093f11a2f3SRobert Watson 			(void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL);
3610df8bae1dSRodney W. Grimes 	}
36113f11a2f3SRobert Watson 	SOCKBUF_UNLOCK(&so->so_rcv);
361291d6cfa6SBjoern A. Zeeb 
361391d6cfa6SBjoern A. Zeeb 	/* Check the interface for TSO capabilities. */
36143c914c54SAndre Oppermann 	if (cap.ifcap & CSUM_TSO) {
361591d6cfa6SBjoern A. Zeeb 		tp->t_flags |= TF_TSO;
36163c914c54SAndre Oppermann 		tp->t_tsomax = cap.tsomax;
36173c914c54SAndre Oppermann 	}
3618a0292f23SGarrett Wollman }
3619a0292f23SGarrett Wollman 
3620a0292f23SGarrett Wollman /*
3621a0292f23SGarrett Wollman  * Determine the MSS option to send on an outgoing SYN.
3622a0292f23SGarrett Wollman  */
3623a0292f23SGarrett Wollman int
3624ad3f9ab3SAndre Oppermann tcp_mssopt(struct in_conninfo *inc)
3625a0292f23SGarrett Wollman {
362697d8d152SAndre Oppermann 	int mss = 0;
362797d8d152SAndre Oppermann 	u_long maxmtu = 0;
362897d8d152SAndre Oppermann 	u_long thcmtu = 0;
362997d8d152SAndre Oppermann 	size_t min_protoh;
3630a0292f23SGarrett Wollman 
363197d8d152SAndre Oppermann 	KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer"));
3632a0292f23SGarrett Wollman 
363331b3783cSHajimu UMEMOTO #ifdef INET6
3634dcdb4371SBjoern A. Zeeb 	if (inc->inc_flags & INC_ISIPV6) {
3635603724d3SBjoern A. Zeeb 		mss = V_tcp_v6mssdflt;
3636233dcce1SAndre Oppermann 		maxmtu = tcp_maxmtu6(inc, NULL);
363797d8d152SAndre Oppermann 		min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
3638b287c6c7SBjoern A. Zeeb 	}
363931b3783cSHajimu UMEMOTO #endif
3640b287c6c7SBjoern A. Zeeb #if defined(INET) && defined(INET6)
3641b287c6c7SBjoern A. Zeeb 	else
3642b287c6c7SBjoern A. Zeeb #endif
3643b287c6c7SBjoern A. Zeeb #ifdef INET
364497d8d152SAndre Oppermann 	{
3645603724d3SBjoern A. Zeeb 		mss = V_tcp_mssdflt;
3646233dcce1SAndre Oppermann 		maxmtu = tcp_maxmtu(inc, NULL);
364797d8d152SAndre Oppermann 		min_protoh = sizeof(struct tcpiphdr);
364897d8d152SAndre Oppermann 	}
3649b287c6c7SBjoern A. Zeeb #endif
36503a9391deSBjoern A. Zeeb #if defined(INET6) || defined(INET)
36513a9391deSBjoern A. Zeeb 	thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */
36523a9391deSBjoern A. Zeeb #endif
36533a9391deSBjoern A. Zeeb 
365497d8d152SAndre Oppermann 	if (maxmtu && thcmtu)
365597d8d152SAndre Oppermann 		mss = min(maxmtu, thcmtu) - min_protoh;
365697d8d152SAndre Oppermann 	else if (maxmtu || thcmtu)
365797d8d152SAndre Oppermann 		mss = max(maxmtu, thcmtu) - min_protoh;
365897d8d152SAndre Oppermann 
365997d8d152SAndre Oppermann 	return (mss);
3660df8bae1dSRodney W. Grimes }
366146f58482SJonathan Lemon 
366246f58482SJonathan Lemon 
366346f58482SJonathan Lemon /*
3664c068736aSJeffrey Hsu  * On a partial ack arrives, force the retransmission of the
3665c068736aSJeffrey Hsu  * next unacknowledged segment.  Do not clear tp->t_dupacks.
3666c068736aSJeffrey Hsu  * By setting snd_nxt to ti_ack, this forces retransmission timer to
3667c068736aSJeffrey Hsu  * be started again.
366846f58482SJonathan Lemon  */
3669c068736aSJeffrey Hsu static void
3670ad3f9ab3SAndre Oppermann tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th)
367146f58482SJonathan Lemon {
367246f58482SJonathan Lemon 	tcp_seq onxt = tp->snd_nxt;
367346f58482SJonathan Lemon 	u_long  ocwnd = tp->snd_cwnd;
367446f58482SJonathan Lemon 
36758501a69cSRobert Watson 	INP_WLOCK_ASSERT(tp->t_inpcb);
36767a3244ccSRobert Watson 
3677b8152ba7SAndre Oppermann 	tcp_timer_activate(tp, TT_REXMT, 0);
367846f58482SJonathan Lemon 	tp->t_rtttime = 0;
367946f58482SJonathan Lemon 	tp->snd_nxt = th->th_ack;
36806b2a5f92SJayanth Vijayaraghavan 	/*
3681c068736aSJeffrey Hsu 	 * Set snd_cwnd to one segment beyond acknowledged offset.
3682c068736aSJeffrey Hsu 	 * (tp->snd_una has not yet been updated when this function is called.)
36836b2a5f92SJayanth Vijayaraghavan 	 */
3684dbc42409SLawrence Stewart 	tp->snd_cwnd = tp->t_maxseg + BYTES_THIS_ACK(tp, th);
3685a84db8f4SMatthew Dillon 	tp->t_flags |= TF_ACKNOW;
36866b2a5f92SJayanth Vijayaraghavan 	(void) tcp_output(tp);
368746f58482SJonathan Lemon 	tp->snd_cwnd = ocwnd;
368846f58482SJonathan Lemon 	if (SEQ_GT(onxt, tp->snd_nxt))
368946f58482SJonathan Lemon 		tp->snd_nxt = onxt;
369046f58482SJonathan Lemon 	/*
369146f58482SJonathan Lemon 	 * Partial window deflation.  Relies on fact that tp->snd_una
369246f58482SJonathan Lemon 	 * not updated yet.
369346f58482SJonathan Lemon 	 */
3694dbc42409SLawrence Stewart 	if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th))
3695dbc42409SLawrence Stewart 		tp->snd_cwnd -= BYTES_THIS_ACK(tp, th);
3696d7587117SPaul Saab 	else
3697d7587117SPaul Saab 		tp->snd_cwnd = 0;
3698d7587117SPaul Saab 	tp->snd_cwnd += tp->t_maxseg;
369946f58482SJonathan Lemon }
3700