xref: /freebsd/sys/netinet/tcp_input.c (revision eaf80179e2036deb396c6988bfacc9975d49ded0)
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.
4df8bae1dSRodney W. Grimes  *
5df8bae1dSRodney W. Grimes  * Redistribution and use in source and binary forms, with or without
6df8bae1dSRodney W. Grimes  * modification, are permitted provided that the following conditions
7df8bae1dSRodney W. Grimes  * are met:
8df8bae1dSRodney W. Grimes  * 1. Redistributions of source code must retain the above copyright
9df8bae1dSRodney W. Grimes  *    notice, this list of conditions and the following disclaimer.
10df8bae1dSRodney W. Grimes  * 2. Redistributions in binary form must reproduce the above copyright
11df8bae1dSRodney W. Grimes  *    notice, this list of conditions and the following disclaimer in the
12df8bae1dSRodney W. Grimes  *    documentation and/or other materials provided with the distribution.
13df8bae1dSRodney W. Grimes  * 4. Neither the name of the University nor the names of its contributors
14df8bae1dSRodney W. Grimes  *    may be used to endorse or promote products derived from this software
15df8bae1dSRodney W. Grimes  *    without specific prior written permission.
16df8bae1dSRodney W. Grimes  *
17df8bae1dSRodney W. Grimes  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18df8bae1dSRodney W. Grimes  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19df8bae1dSRodney W. Grimes  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20df8bae1dSRodney W. Grimes  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21df8bae1dSRodney W. Grimes  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22df8bae1dSRodney W. Grimes  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23df8bae1dSRodney W. Grimes  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24df8bae1dSRodney W. Grimes  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25df8bae1dSRodney W. Grimes  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26df8bae1dSRodney W. Grimes  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27df8bae1dSRodney W. Grimes  * SUCH DAMAGE.
28df8bae1dSRodney W. Grimes  *
29e79adb8eSGarrett Wollman  *	@(#)tcp_input.c	8.12 (Berkeley) 5/24/95
30c3aac50fSPeter Wemm  * $FreeBSD$
31df8bae1dSRodney W. Grimes  */
32df8bae1dSRodney W. Grimes 
33f9e354dfSJulian Elischer #include "opt_ipfw.h"		/* for ipfw_fwd		*/
341cfd4b53SBruce M Simpson #include "opt_inet.h"
35fb59c426SYoshinobu Inoue #include "opt_inet6.h"
363a2a9f79SYoshinobu Inoue #include "opt_ipsec.h"
37c488362eSRobert Watson #include "opt_mac.h"
380cc12cc5SJoerg Wunsch #include "opt_tcpdebug.h"
39e46cd3d4SDag-Erling Smørgrav #include "opt_tcp_input.h"
406d90faf3SPaul Saab #include "opt_tcp_sack.h"
410cc12cc5SJoerg Wunsch 
42df8bae1dSRodney W. Grimes #include <sys/param.h>
4398163b98SPoul-Henning Kamp #include <sys/kernel.h>
44c488362eSRobert Watson #include <sys/mac.h>
45df8bae1dSRodney W. Grimes #include <sys/malloc.h>
46df8bae1dSRodney W. Grimes #include <sys/mbuf.h>
47a29f300eSGarrett Wollman #include <sys/proc.h>		/* for proc0 declaration */
48df8bae1dSRodney W. Grimes #include <sys/protosw.h>
49960ed29cSSeigo Tanimura #include <sys/signalvar.h>
50df8bae1dSRodney W. Grimes #include <sys/socket.h>
51df8bae1dSRodney W. Grimes #include <sys/socketvar.h>
52960ed29cSSeigo Tanimura #include <sys/sysctl.h>
53816a3d83SPoul-Henning Kamp #include <sys/syslog.h>
54960ed29cSSeigo Tanimura #include <sys/systm.h>
55df8bae1dSRodney W. Grimes 
56e79adb8eSGarrett Wollman #include <machine/cpu.h>	/* before tcp_seq.h, for tcp_random18() */
57e79adb8eSGarrett Wollman 
5812e2e970SAndre Oppermann #include <vm/uma.h>
5912e2e970SAndre Oppermann 
60df8bae1dSRodney W. Grimes #include <net/if.h>
61df8bae1dSRodney W. Grimes #include <net/route.h>
62df8bae1dSRodney W. Grimes 
63df8bae1dSRodney W. Grimes #include <netinet/in.h>
64960ed29cSSeigo Tanimura #include <netinet/in_pcb.h>
65df8bae1dSRodney W. Grimes #include <netinet/in_systm.h>
66960ed29cSSeigo Tanimura #include <netinet/in_var.h>
67df8bae1dSRodney W. Grimes #include <netinet/ip.h>
68686cdd19SJun-ichiro itojun Hagino #include <netinet/ip_icmp.h>	/* for ICMP_BANDLIM		*/
69686cdd19SJun-ichiro itojun Hagino #include <netinet/icmp_var.h>	/* for ICMP_BANDLIM		*/
70df8bae1dSRodney W. Grimes #include <netinet/ip_var.h>
71ef39adf0SAndre Oppermann #include <netinet/ip_options.h>
72686cdd19SJun-ichiro itojun Hagino #include <netinet/ip6.h>
73686cdd19SJun-ichiro itojun Hagino #include <netinet/icmp6.h>
74686cdd19SJun-ichiro itojun Hagino #include <netinet6/in6_pcb.h>
75960ed29cSSeigo Tanimura #include <netinet6/ip6_var.h>
76960ed29cSSeigo Tanimura #include <netinet6/nd6.h>
77df8bae1dSRodney W. Grimes #include <netinet/tcp.h>
78df8bae1dSRodney W. Grimes #include <netinet/tcp_fsm.h>
79df8bae1dSRodney W. Grimes #include <netinet/tcp_seq.h>
80df8bae1dSRodney W. Grimes #include <netinet/tcp_timer.h>
81df8bae1dSRodney W. Grimes #include <netinet/tcp_var.h>
82fb59c426SYoshinobu Inoue #include <netinet6/tcp6_var.h>
83df8bae1dSRodney W. Grimes #include <netinet/tcpip.h>
84610ee2f9SDavid Greenman #ifdef TCPDEBUG
85df8bae1dSRodney W. Grimes #include <netinet/tcp_debug.h>
86fb59c426SYoshinobu Inoue #endif /* TCPDEBUG */
87fb59c426SYoshinobu Inoue 
88b9234fafSSam Leffler #ifdef FAST_IPSEC
89b9234fafSSam Leffler #include <netipsec/ipsec.h>
90b9234fafSSam Leffler #include <netipsec/ipsec6.h>
91b9234fafSSam Leffler #endif /*FAST_IPSEC*/
92b9234fafSSam Leffler 
93fb59c426SYoshinobu Inoue #ifdef IPSEC
94fb59c426SYoshinobu Inoue #include <netinet6/ipsec.h>
953a2a9f79SYoshinobu Inoue #include <netinet6/ipsec6.h>
96fb59c426SYoshinobu Inoue #include <netkey/key.h>
97fb59c426SYoshinobu Inoue #endif /*IPSEC*/
98fb59c426SYoshinobu Inoue 
99db4f9cc7SJonathan Lemon #include <machine/in_cksum.h>
100db4f9cc7SJonathan Lemon 
101c068736aSJeffrey Hsu static const int tcprexmtthresh = 3;
1020312fbe9SPoul-Henning Kamp 
1032f96f1f4SGarrett Wollman struct	tcpstat tcpstat;
104c73d99b5SRuslan Ermilov SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW,
1053d177f46SBill Fumerola     &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)");
1060312fbe9SPoul-Henning Kamp 
107d78a37adSPaul Traina static int log_in_vain = 0;
108816a3d83SPoul-Henning Kamp SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
1093d177f46SBill Fumerola     &log_in_vain, 0, "Log all incoming TCP connections");
110816a3d83SPoul-Henning Kamp 
11116f7f31fSGeoff Rehmet static int blackhole = 0;
11216f7f31fSGeoff Rehmet SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
11316f7f31fSGeoff Rehmet 	&blackhole, 0, "Do not send RST when dropping refused connections");
11416f7f31fSGeoff Rehmet 
115f498eeeeSDavid Greenman int tcp_delack_enabled = 1;
11684e33c9eSDavid Greenman SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
1173d177f46SBill Fumerola     &tcp_delack_enabled, 0,
1183d177f46SBill Fumerola     "Delay ACK to try and piggyback it onto a data packet");
119f498eeeeSDavid Greenman 
120f8613305SDag-Erling Smørgrav #ifdef TCP_DROP_SYNFIN
121f8613305SDag-Erling Smørgrav static int drop_synfin = 0;
122f8613305SDag-Erling Smørgrav SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
123f8613305SDag-Erling Smørgrav     &drop_synfin, 0, "Drop TCP packets with SYN+FIN set");
124f8613305SDag-Erling Smørgrav #endif
125f8613305SDag-Erling Smørgrav 
126dba7bc6aSAndre Oppermann static int tcp_do_rfc3042 = 1;
127582a954bSJeffrey Hsu SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW,
128582a954bSJeffrey Hsu     &tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)");
129582a954bSJeffrey Hsu 
130dba7bc6aSAndre Oppermann static int tcp_do_rfc3390 = 1;
131da3a8a1aSJeffrey Hsu SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW,
132da3a8a1aSJeffrey Hsu     &tcp_do_rfc3390, 0,
133da3a8a1aSJeffrey Hsu     "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
134da3a8a1aSJeffrey Hsu 
135a69968eeSMike Silbersack static int tcp_insecure_rst = 0;
136a69968eeSMike Silbersack SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW,
137a69968eeSMike Silbersack     &tcp_insecure_rst, 0,
138a69968eeSMike Silbersack     "Follow the old (insecure) criteria for accepting RST packets.");
139a69968eeSMike Silbersack 
14012e2e970SAndre Oppermann SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
14112e2e970SAndre Oppermann 	    "TCP Segment Reassembly Queue");
14212e2e970SAndre Oppermann 
14312e2e970SAndre Oppermann static int tcp_reass_maxseg = 0;
14412e2e970SAndre Oppermann SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN,
14512e2e970SAndre Oppermann 	   &tcp_reass_maxseg, 0,
14612e2e970SAndre Oppermann 	   "Global maximum number of TCP Segments in Reassembly Queue");
14712e2e970SAndre Oppermann 
14812e2e970SAndre Oppermann int tcp_reass_qsize = 0;
14912e2e970SAndre Oppermann SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD,
15012e2e970SAndre Oppermann 	   &tcp_reass_qsize, 0,
15112e2e970SAndre Oppermann 	   "Global number of TCP Segments currently in Reassembly Queue");
15212e2e970SAndre Oppermann 
15312e2e970SAndre Oppermann static int tcp_reass_maxqlen = 48;
15412e2e970SAndre Oppermann SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxqlen, CTLFLAG_RW,
15512e2e970SAndre Oppermann 	   &tcp_reass_maxqlen, 0,
15612e2e970SAndre Oppermann 	   "Maximum number of TCP Segments per individual Reassembly Queue");
15712e2e970SAndre Oppermann 
15812e2e970SAndre Oppermann static int tcp_reass_overflows = 0;
15912e2e970SAndre Oppermann SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
16012e2e970SAndre Oppermann 	   &tcp_reass_overflows, 0,
16112e2e970SAndre Oppermann 	   "Global number of TCP Segment Reassembly Queue Overflows");
16212e2e970SAndre Oppermann 
16315bd2b43SDavid Greenman struct inpcbhead tcb;
164fb59c426SYoshinobu Inoue #define	tcb6	tcb  /* for KAME src sync over BSD*'s */
16515bd2b43SDavid Greenman struct inpcbinfo tcbinfo;
166f76fcf6dSJeffrey Hsu struct mtx	*tcbinfo_mtx;
167df8bae1dSRodney W. Grimes 
1685a53ca16SPaul Saab static void	 tcp_dooptions(struct tcpopt *, u_char *, int, int);
1696d90faf3SPaul Saab 
1704d77a549SAlfred Perlstein static void	 tcp_pulloutofband(struct socket *,
1714d77a549SAlfred Perlstein 		     struct tcphdr *, struct mbuf *, int);
1724d77a549SAlfred Perlstein static int	 tcp_reass(struct tcpcb *, struct tcphdr *, int *,
1734d77a549SAlfred Perlstein 		     struct mbuf *);
1744d77a549SAlfred Perlstein static void	 tcp_xmit_timer(struct tcpcb *, int);
175c068736aSJeffrey Hsu static void	 tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *);
176340c35deSJonathan Lemon static int	 tcp_timewait(struct tcptw *, struct tcpopt *,
177340c35deSJonathan Lemon 		     struct tcphdr *, struct mbuf *, int);
1780312fbe9SPoul-Henning Kamp 
179fb59c426SYoshinobu Inoue /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
180fb59c426SYoshinobu Inoue #ifdef INET6
181fb59c426SYoshinobu Inoue #define ND6_HINT(tp) \
182fb59c426SYoshinobu Inoue do { \
183fb59c426SYoshinobu Inoue 	if ((tp) && (tp)->t_inpcb && \
18497d8d152SAndre Oppermann 	    ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \
18597d8d152SAndre Oppermann 		nd6_nud_hint(NULL, NULL, 0); \
186fb59c426SYoshinobu Inoue } while (0)
187fb59c426SYoshinobu Inoue #else
188fb59c426SYoshinobu Inoue #define ND6_HINT(tp)
189fb59c426SYoshinobu Inoue #endif
190df8bae1dSRodney W. Grimes 
191df8bae1dSRodney W. Grimes /*
192262c1c1aSMatthew Dillon  * Indicate whether this ack should be delayed.  We can delay the ack if
193262c1c1aSMatthew Dillon  *	- there is no delayed ack timer in progress and
194262c1c1aSMatthew Dillon  *	- our last ack wasn't a 0-sized window.  We never want to delay
1953bfd6421SJonathan Lemon  *	  the ack that opens up a 0-sized window and
1963bfd6421SJonathan Lemon  *		- delayed acks are enabled or
1973bfd6421SJonathan Lemon  *		- this is a half-synchronized T/TCP connection.
198d8c85a26SJonathan Lemon  */
199d8c85a26SJonathan Lemon #define DELAY_ACK(tp)							\
200a14c749fSJonathan Lemon 	((!callout_active(tp->tt_delack) &&				\
201a14c749fSJonathan Lemon 	    (tp->t_flags & TF_RXWIN0SENT) == 0) &&			\
2023bfd6421SJonathan Lemon 	    (tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN)))
203d8c85a26SJonathan Lemon 
20412e2e970SAndre Oppermann /* Initialize TCP reassembly queue */
20512e2e970SAndre Oppermann uma_zone_t	tcp_reass_zone;
20612e2e970SAndre Oppermann void
20712e2e970SAndre Oppermann tcp_reass_init()
20812e2e970SAndre Oppermann {
20912e2e970SAndre Oppermann 	tcp_reass_maxseg = nmbclusters / 16;
21012e2e970SAndre Oppermann 	TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments",
21112e2e970SAndre Oppermann 	    &tcp_reass_maxseg);
21212e2e970SAndre Oppermann 	tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent),
21312e2e970SAndre Oppermann 	    NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
21412e2e970SAndre Oppermann 	uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg);
21512e2e970SAndre Oppermann }
21612e2e970SAndre Oppermann 
2170312fbe9SPoul-Henning Kamp static int
218fb59c426SYoshinobu Inoue tcp_reass(tp, th, tlenp, m)
219df8bae1dSRodney W. Grimes 	register struct tcpcb *tp;
220fb59c426SYoshinobu Inoue 	register struct tcphdr *th;
221fb59c426SYoshinobu Inoue 	int *tlenp;
222df8bae1dSRodney W. Grimes 	struct mbuf *m;
223df8bae1dSRodney W. Grimes {
224fb59c426SYoshinobu Inoue 	struct tseg_qent *q;
225fb59c426SYoshinobu Inoue 	struct tseg_qent *p = NULL;
226fb59c426SYoshinobu Inoue 	struct tseg_qent *nq;
22712e2e970SAndre Oppermann 	struct tseg_qent *te = NULL;
228df8bae1dSRodney W. Grimes 	struct socket *so = tp->t_inpcb->inp_socket;
229df8bae1dSRodney W. Grimes 	int flags;
230df8bae1dSRodney W. Grimes 
231de30ea13SRobert Watson 	INP_LOCK_ASSERT(tp->t_inpcb);
232de30ea13SRobert Watson 
233df8bae1dSRodney W. Grimes 	/*
23412e2e970SAndre Oppermann 	 * XXX: tcp_reass() is rather inefficient with its data structures
23512e2e970SAndre Oppermann 	 * and should be rewritten (see NetBSD for optimizations).  While
23612e2e970SAndre Oppermann 	 * doing that it should move to its own file tcp_reass.c.
23712e2e970SAndre Oppermann 	 */
23812e2e970SAndre Oppermann 
23912e2e970SAndre Oppermann 	/*
240de30ea13SRobert Watson 	 * Call with th==NULL after become established to
241df8bae1dSRodney W. Grimes 	 * force pre-ESTABLISHED data up to user socket.
242df8bae1dSRodney W. Grimes 	 */
243de30ea13SRobert Watson 	if (th == NULL)
244df8bae1dSRodney W. Grimes 		goto present;
245df8bae1dSRodney W. Grimes 
24612e2e970SAndre Oppermann 	/*
24712e2e970SAndre Oppermann 	 * Limit the number of segments in the reassembly queue to prevent
24812e2e970SAndre Oppermann 	 * holding on to too many segments (and thus running out of mbufs).
24912e2e970SAndre Oppermann 	 * Make sure to let the missing segment through which caused this
25012e2e970SAndre Oppermann 	 * queue.  Always keep one global queue entry spare to be able to
25112e2e970SAndre Oppermann 	 * process the missing segment.
25212e2e970SAndre Oppermann 	 */
25312e2e970SAndre Oppermann 	if (th->th_seq != tp->rcv_nxt &&
25412e2e970SAndre Oppermann 	    (tcp_reass_qsize + 1 >= tcp_reass_maxseg ||
25512e2e970SAndre Oppermann 	     tp->t_segqlen >= tcp_reass_maxqlen)) {
25612e2e970SAndre Oppermann 		tcp_reass_overflows++;
25712e2e970SAndre Oppermann 		tcpstat.tcps_rcvmemdrop++;
25812e2e970SAndre Oppermann 		m_freem(m);
259e346eeffSPaul Saab 		*tlenp = 0;
26012e2e970SAndre Oppermann 		return (0);
26112e2e970SAndre Oppermann 	}
26212e2e970SAndre Oppermann 
26312e2e970SAndre Oppermann 	/*
26412e2e970SAndre Oppermann 	 * Allocate a new queue entry. If we can't, or hit the zone limit
26512e2e970SAndre Oppermann 	 * just drop the pkt.
26612e2e970SAndre Oppermann 	 */
26712e2e970SAndre Oppermann 	te = uma_zalloc(tcp_reass_zone, M_NOWAIT);
268fb59c426SYoshinobu Inoue 	if (te == NULL) {
269fb59c426SYoshinobu Inoue 		tcpstat.tcps_rcvmemdrop++;
270fb59c426SYoshinobu Inoue 		m_freem(m);
271e346eeffSPaul Saab 		*tlenp = 0;
272fb59c426SYoshinobu Inoue 		return (0);
273fb59c426SYoshinobu Inoue 	}
27412e2e970SAndre Oppermann 	tp->t_segqlen++;
27512e2e970SAndre Oppermann 	tcp_reass_qsize++;
2766effc713SDoug Rabson 
277df8bae1dSRodney W. Grimes 	/*
278df8bae1dSRodney W. Grimes 	 * Find a segment which begins after this one does.
279df8bae1dSRodney W. Grimes 	 */
280fb59c426SYoshinobu Inoue 	LIST_FOREACH(q, &tp->t_segq, tqe_q) {
281fb59c426SYoshinobu Inoue 		if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
282df8bae1dSRodney W. Grimes 			break;
283fb59c426SYoshinobu Inoue 		p = q;
284fb59c426SYoshinobu Inoue 	}
285df8bae1dSRodney W. Grimes 
286df8bae1dSRodney W. Grimes 	/*
287df8bae1dSRodney W. Grimes 	 * If there is a preceding segment, it may provide some of
288df8bae1dSRodney W. Grimes 	 * our data already.  If so, drop the data from the incoming
289df8bae1dSRodney W. Grimes 	 * segment.  If it provides all of our data, drop us.
290df8bae1dSRodney W. Grimes 	 */
2916effc713SDoug Rabson 	if (p != NULL) {
292df8bae1dSRodney W. Grimes 		register int i;
293df8bae1dSRodney W. Grimes 		/* conversion to int (in i) handles seq wraparound */
294fb59c426SYoshinobu Inoue 		i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
295df8bae1dSRodney W. Grimes 		if (i > 0) {
296fb59c426SYoshinobu Inoue 			if (i >= *tlenp) {
297df8bae1dSRodney W. Grimes 				tcpstat.tcps_rcvduppack++;
298fb59c426SYoshinobu Inoue 				tcpstat.tcps_rcvdupbyte += *tlenp;
299df8bae1dSRodney W. Grimes 				m_freem(m);
30012e2e970SAndre Oppermann 				uma_zfree(tcp_reass_zone, te);
30112e2e970SAndre Oppermann 				tp->t_segqlen--;
30212e2e970SAndre Oppermann 				tcp_reass_qsize--;
303a0292f23SGarrett Wollman 				/*
304a0292f23SGarrett Wollman 				 * Try to present any queued data
305a0292f23SGarrett Wollman 				 * at the left window edge to the user.
306a0292f23SGarrett Wollman 				 * This is needed after the 3-WHS
307a0292f23SGarrett Wollman 				 * completes.
308a0292f23SGarrett Wollman 				 */
309a0292f23SGarrett Wollman 				goto present;	/* ??? */
310df8bae1dSRodney W. Grimes 			}
311df8bae1dSRodney W. Grimes 			m_adj(m, i);
312fb59c426SYoshinobu Inoue 			*tlenp -= i;
313fb59c426SYoshinobu Inoue 			th->th_seq += i;
314df8bae1dSRodney W. Grimes 		}
315df8bae1dSRodney W. Grimes 	}
316df8bae1dSRodney W. Grimes 	tcpstat.tcps_rcvoopack++;
317fb59c426SYoshinobu Inoue 	tcpstat.tcps_rcvoobyte += *tlenp;
318df8bae1dSRodney W. Grimes 
319df8bae1dSRodney W. Grimes 	/*
320df8bae1dSRodney W. Grimes 	 * While we overlap succeeding segments trim them or,
321df8bae1dSRodney W. Grimes 	 * if they are completely covered, dequeue them.
322df8bae1dSRodney W. Grimes 	 */
3236effc713SDoug Rabson 	while (q) {
324fb59c426SYoshinobu Inoue 		register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
325df8bae1dSRodney W. Grimes 		if (i <= 0)
326df8bae1dSRodney W. Grimes 			break;
327fb59c426SYoshinobu Inoue 		if (i < q->tqe_len) {
328fb59c426SYoshinobu Inoue 			q->tqe_th->th_seq += i;
329fb59c426SYoshinobu Inoue 			q->tqe_len -= i;
330fb59c426SYoshinobu Inoue 			m_adj(q->tqe_m, i);
331df8bae1dSRodney W. Grimes 			break;
332df8bae1dSRodney W. Grimes 		}
3336effc713SDoug Rabson 
334fb59c426SYoshinobu Inoue 		nq = LIST_NEXT(q, tqe_q);
335fb59c426SYoshinobu Inoue 		LIST_REMOVE(q, tqe_q);
336fb59c426SYoshinobu Inoue 		m_freem(q->tqe_m);
33712e2e970SAndre Oppermann 		uma_zfree(tcp_reass_zone, q);
33812e2e970SAndre Oppermann 		tp->t_segqlen--;
33912e2e970SAndre Oppermann 		tcp_reass_qsize--;
3406effc713SDoug Rabson 		q = nq;
341df8bae1dSRodney W. Grimes 	}
342df8bae1dSRodney W. Grimes 
343fb59c426SYoshinobu Inoue 	/* Insert the new segment queue entry into place. */
344fb59c426SYoshinobu Inoue 	te->tqe_m = m;
345fb59c426SYoshinobu Inoue 	te->tqe_th = th;
346fb59c426SYoshinobu Inoue 	te->tqe_len = *tlenp;
347fb59c426SYoshinobu Inoue 
3486effc713SDoug Rabson 	if (p == NULL) {
349fb59c426SYoshinobu Inoue 		LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
3506effc713SDoug Rabson 	} else {
351fb59c426SYoshinobu Inoue 		LIST_INSERT_AFTER(p, te, tqe_q);
3526effc713SDoug Rabson 	}
353df8bae1dSRodney W. Grimes 
354df8bae1dSRodney W. Grimes present:
355df8bae1dSRodney W. Grimes 	/*
356df8bae1dSRodney W. Grimes 	 * Present data to user, advancing rcv_nxt through
357df8bae1dSRodney W. Grimes 	 * completed sequence space.
358df8bae1dSRodney W. Grimes 	 */
359a0292f23SGarrett Wollman 	if (!TCPS_HAVEESTABLISHED(tp->t_state))
360df8bae1dSRodney W. Grimes 		return (0);
361fb59c426SYoshinobu Inoue 	q = LIST_FIRST(&tp->t_segq);
362fb59c426SYoshinobu Inoue 	if (!q || q->tqe_th->th_seq != tp->rcv_nxt)
363df8bae1dSRodney W. Grimes 		return (0);
3641e4d7da7SRobert Watson 	SOCKBUF_LOCK(&so->so_rcv);
365df8bae1dSRodney W. Grimes 	do {
366fb59c426SYoshinobu Inoue 		tp->rcv_nxt += q->tqe_len;
367fb59c426SYoshinobu Inoue 		flags = q->tqe_th->th_flags & TH_FIN;
368fb59c426SYoshinobu Inoue 		nq = LIST_NEXT(q, tqe_q);
369fb59c426SYoshinobu Inoue 		LIST_REMOVE(q, tqe_q);
370c0b99ffaSRobert Watson 		if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
371fb59c426SYoshinobu Inoue 			m_freem(q->tqe_m);
3724cc20ab1SSeigo Tanimura 		else
3731e4d7da7SRobert Watson 			sbappendstream_locked(&so->so_rcv, q->tqe_m);
37412e2e970SAndre Oppermann 		uma_zfree(tcp_reass_zone, q);
37512e2e970SAndre Oppermann 		tp->t_segqlen--;
37612e2e970SAndre Oppermann 		tcp_reass_qsize--;
3776effc713SDoug Rabson 		q = nq;
378fb59c426SYoshinobu Inoue 	} while (q && q->tqe_th->th_seq == tp->rcv_nxt);
379fb59c426SYoshinobu Inoue 	ND6_HINT(tp);
3801e4d7da7SRobert Watson 	sorwakeup_locked(so);
381df8bae1dSRodney W. Grimes 	return (flags);
382df8bae1dSRodney W. Grimes }
383df8bae1dSRodney W. Grimes 
384df8bae1dSRodney W. Grimes /*
385df8bae1dSRodney W. Grimes  * TCP input routine, follows pages 65-76 of the
386df8bae1dSRodney W. Grimes  * protocol specification dated September, 1981 very closely.
387df8bae1dSRodney W. Grimes  */
388fb59c426SYoshinobu Inoue #ifdef INET6
389fb59c426SYoshinobu Inoue int
390fb59c426SYoshinobu Inoue tcp6_input(mp, offp, proto)
391fb59c426SYoshinobu Inoue 	struct mbuf **mp;
392fb59c426SYoshinobu Inoue 	int *offp, proto;
393fb59c426SYoshinobu Inoue {
394fb59c426SYoshinobu Inoue 	register struct mbuf *m = *mp;
39533841545SHajimu UMEMOTO 	struct in6_ifaddr *ia6;
396fb59c426SYoshinobu Inoue 
397fb59c426SYoshinobu Inoue 	IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
398fb59c426SYoshinobu Inoue 
399fb59c426SYoshinobu Inoue 	/*
400fb59c426SYoshinobu Inoue 	 * draft-itojun-ipv6-tcp-to-anycast
401fb59c426SYoshinobu Inoue 	 * better place to put this in?
402fb59c426SYoshinobu Inoue 	 */
40333841545SHajimu UMEMOTO 	ia6 = ip6_getdstifaddr(m);
40433841545SHajimu UMEMOTO 	if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
405fb59c426SYoshinobu Inoue 		struct ip6_hdr *ip6;
406fb59c426SYoshinobu Inoue 
407fb59c426SYoshinobu Inoue 		ip6 = mtod(m, struct ip6_hdr *);
408fb59c426SYoshinobu Inoue 		icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
409fb59c426SYoshinobu Inoue 			    (caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
410fb59c426SYoshinobu Inoue 		return IPPROTO_DONE;
411fb59c426SYoshinobu Inoue 	}
412fb59c426SYoshinobu Inoue 
413f0ffb944SJulian Elischer 	tcp_input(m, *offp);
414fb59c426SYoshinobu Inoue 	return IPPROTO_DONE;
415fb59c426SYoshinobu Inoue }
416fb59c426SYoshinobu Inoue #endif
417fb59c426SYoshinobu Inoue 
418df8bae1dSRodney W. Grimes void
419f0ffb944SJulian Elischer tcp_input(m, off0)
420df8bae1dSRodney W. Grimes 	register struct mbuf *m;
421f0ffb944SJulian Elischer 	int off0;
422df8bae1dSRodney W. Grimes {
423fb59c426SYoshinobu Inoue 	register struct tcphdr *th;
424fb59c426SYoshinobu Inoue 	register struct ip *ip = NULL;
425fb59c426SYoshinobu Inoue 	register struct ipovly *ipov;
426f76fcf6dSJeffrey Hsu 	register struct inpcb *inp = NULL;
427e79adb8eSGarrett Wollman 	u_char *optp = NULL;
42826f9a767SRodney W. Grimes 	int optlen = 0;
429a0194ef1SBruce M Simpson 	int len, tlen, off;
430fb59c426SYoshinobu Inoue 	int drop_hdrlen;
431df8bae1dSRodney W. Grimes 	register struct tcpcb *tp = 0;
432fb59c426SYoshinobu Inoue 	register int thflags;
43326f9a767SRodney W. Grimes 	struct socket *so = 0;
434df8bae1dSRodney W. Grimes 	int todrop, acked, ourfinisacked, needoutput = 0;
435a0292f23SGarrett Wollman 	u_long tiwin;
436a0292f23SGarrett Wollman 	struct tcpopt to;		/* options in this segment */
437f76fcf6dSJeffrey Hsu 	int headlocked = 0;
4389b932e9eSAndre Oppermann #ifdef IPFIREWALL_FORWARD
4399b932e9eSAndre Oppermann 	struct m_tag *fwd_tag;
4409b932e9eSAndre Oppermann #endif
441c068736aSJeffrey Hsu 	int rstreason; /* For badport_bandlim accounting purposes */
442c068736aSJeffrey Hsu 
443c068736aSJeffrey Hsu 	struct ip6_hdr *ip6 = NULL;
444c068736aSJeffrey Hsu #ifdef INET6
445c068736aSJeffrey Hsu 	int isipv6;
446c068736aSJeffrey Hsu #else
447c068736aSJeffrey Hsu 	const int isipv6 = 0;
448c068736aSJeffrey Hsu #endif
449f76fcf6dSJeffrey Hsu 
450610ee2f9SDavid Greenman #ifdef TCPDEBUG
451c068736aSJeffrey Hsu 	/*
452c068736aSJeffrey Hsu 	 * The size of tcp_saveipgen must be the size of the max ip header,
453c068736aSJeffrey Hsu 	 * now IPv6.
454c068736aSJeffrey Hsu 	 */
455410bb1bfSLuigi Rizzo 	u_char tcp_saveipgen[40];
456410bb1bfSLuigi Rizzo 	struct tcphdr tcp_savetcp;
457610ee2f9SDavid Greenman 	short ostate = 0;
458610ee2f9SDavid Greenman #endif
459c068736aSJeffrey Hsu 
460fb59c426SYoshinobu Inoue #ifdef INET6
461fb59c426SYoshinobu Inoue 	isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
462fb59c426SYoshinobu Inoue #endif
463a0292f23SGarrett Wollman 	bzero((char *)&to, sizeof(to));
464a0292f23SGarrett Wollman 
465df8bae1dSRodney W. Grimes 	tcpstat.tcps_rcvtotal++;
466fb59c426SYoshinobu Inoue 
467fb59c426SYoshinobu Inoue 	if (isipv6) {
46804d3a452SHajimu UMEMOTO #ifdef INET6
469fb59c426SYoshinobu Inoue 		/* IP6_EXTHDR_CHECK() is already done at tcp6_input() */
470fb59c426SYoshinobu Inoue 		ip6 = mtod(m, struct ip6_hdr *);
471fb59c426SYoshinobu Inoue 		tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
472fb59c426SYoshinobu Inoue 		if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
473fb59c426SYoshinobu Inoue 			tcpstat.tcps_rcvbadsum++;
474fb59c426SYoshinobu Inoue 			goto drop;
475fb59c426SYoshinobu Inoue 		}
476fb59c426SYoshinobu Inoue 		th = (struct tcphdr *)((caddr_t)ip6 + off0);
47733841545SHajimu UMEMOTO 
47833841545SHajimu UMEMOTO 		/*
47933841545SHajimu UMEMOTO 		 * Be proactive about unspecified IPv6 address in source.
48033841545SHajimu UMEMOTO 		 * As we use all-zero to indicate unbounded/unconnected pcb,
48133841545SHajimu UMEMOTO 		 * unspecified IPv6 address can be used to confuse us.
48233841545SHajimu UMEMOTO 		 *
48333841545SHajimu UMEMOTO 		 * Note that packets with unspecified IPv6 destination is
48433841545SHajimu UMEMOTO 		 * already dropped in ip6_input.
48533841545SHajimu UMEMOTO 		 */
48633841545SHajimu UMEMOTO 		if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
48733841545SHajimu UMEMOTO 			/* XXX stat */
48833841545SHajimu UMEMOTO 			goto drop;
48933841545SHajimu UMEMOTO 		}
49004d3a452SHajimu UMEMOTO #else
49104d3a452SHajimu UMEMOTO 		th = NULL;		/* XXX: avoid compiler warning */
49204d3a452SHajimu UMEMOTO #endif
493c068736aSJeffrey Hsu 	} else {
494df8bae1dSRodney W. Grimes 		/*
495df8bae1dSRodney W. Grimes 		 * Get IP and TCP header together in first mbuf.
496df8bae1dSRodney W. Grimes 		 * Note: IP leaves IP header in first mbuf.
497df8bae1dSRodney W. Grimes 		 */
498fb59c426SYoshinobu Inoue 		if (off0 > sizeof (struct ip)) {
499df8bae1dSRodney W. Grimes 			ip_stripoptions(m, (struct mbuf *)0);
500fb59c426SYoshinobu Inoue 			off0 = sizeof(struct ip);
501fb59c426SYoshinobu Inoue 		}
502df8bae1dSRodney W. Grimes 		if (m->m_len < sizeof (struct tcpiphdr)) {
503df8bae1dSRodney W. Grimes 			if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) {
504df8bae1dSRodney W. Grimes 				tcpstat.tcps_rcvshort++;
505df8bae1dSRodney W. Grimes 				return;
506df8bae1dSRodney W. Grimes 			}
507df8bae1dSRodney W. Grimes 		}
508fb59c426SYoshinobu Inoue 		ip = mtod(m, struct ip *);
509fb59c426SYoshinobu Inoue 		ipov = (struct ipovly *)ip;
510db4f9cc7SJonathan Lemon 		th = (struct tcphdr *)((caddr_t)ip + off0);
511db4f9cc7SJonathan Lemon 		tlen = ip->ip_len;
512df8bae1dSRodney W. Grimes 
513db4f9cc7SJonathan Lemon 		if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
514db4f9cc7SJonathan Lemon 			if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
515db4f9cc7SJonathan Lemon 				th->th_sum = m->m_pkthdr.csum_data;
516db4f9cc7SJonathan Lemon 			else
517db4f9cc7SJonathan Lemon 				th->th_sum = in_pseudo(ip->ip_src.s_addr,
518c068736aSJeffrey Hsu 						ip->ip_dst.s_addr,
519c068736aSJeffrey Hsu 						htonl(m->m_pkthdr.csum_data +
520c068736aSJeffrey Hsu 							ip->ip_len +
521c068736aSJeffrey Hsu 							IPPROTO_TCP));
522db4f9cc7SJonathan Lemon 			th->th_sum ^= 0xffff;
5233c653157SHartmut Brandt #ifdef TCPDEBUG
5243c653157SHartmut Brandt 			ipov->ih_len = (u_short)tlen;
5253c653157SHartmut Brandt 			ipov->ih_len = htons(ipov->ih_len);
5263c653157SHartmut Brandt #endif
527db4f9cc7SJonathan Lemon 		} else {
528df8bae1dSRodney W. Grimes 			/*
529df8bae1dSRodney W. Grimes 			 * Checksum extended TCP header and data.
530df8bae1dSRodney W. Grimes 			 */
531df8bae1dSRodney W. Grimes 			len = sizeof (struct ip) + tlen;
532fb59c426SYoshinobu Inoue 			bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
533fb59c426SYoshinobu Inoue 			ipov->ih_len = (u_short)tlen;
534fd8e4ebcSMike Barcroft 			ipov->ih_len = htons(ipov->ih_len);
535fb59c426SYoshinobu Inoue 			th->th_sum = in_cksum(m, len);
536db4f9cc7SJonathan Lemon 		}
537fb59c426SYoshinobu Inoue 		if (th->th_sum) {
538df8bae1dSRodney W. Grimes 			tcpstat.tcps_rcvbadsum++;
539df8bae1dSRodney W. Grimes 			goto drop;
540df8bae1dSRodney W. Grimes 		}
541fb59c426SYoshinobu Inoue #ifdef INET6
542fb59c426SYoshinobu Inoue 		/* Re-initialization for later version check */
543fb59c426SYoshinobu Inoue 		ip->ip_v = IPVERSION;
544fb59c426SYoshinobu Inoue #endif
545fb59c426SYoshinobu Inoue 	}
546df8bae1dSRodney W. Grimes 
547df8bae1dSRodney W. Grimes 	/*
548df8bae1dSRodney W. Grimes 	 * Check that TCP offset makes sense,
549df8bae1dSRodney W. Grimes 	 * pull out TCP options and adjust length.		XXX
550df8bae1dSRodney W. Grimes 	 */
551fb59c426SYoshinobu Inoue 	off = th->th_off << 2;
552df8bae1dSRodney W. Grimes 	if (off < sizeof (struct tcphdr) || off > tlen) {
553df8bae1dSRodney W. Grimes 		tcpstat.tcps_rcvbadoff++;
554df8bae1dSRodney W. Grimes 		goto drop;
555df8bae1dSRodney W. Grimes 	}
556fb59c426SYoshinobu Inoue 	tlen -= off;	/* tlen is used instead of ti->ti_len */
557df8bae1dSRodney W. Grimes 	if (off > sizeof (struct tcphdr)) {
558fb59c426SYoshinobu Inoue 		if (isipv6) {
55904d3a452SHajimu UMEMOTO #ifdef INET6
560fb59c426SYoshinobu Inoue 			IP6_EXTHDR_CHECK(m, off0, off, );
561fb59c426SYoshinobu Inoue 			ip6 = mtod(m, struct ip6_hdr *);
562fb59c426SYoshinobu Inoue 			th = (struct tcphdr *)((caddr_t)ip6 + off0);
56304d3a452SHajimu UMEMOTO #endif
564c068736aSJeffrey Hsu 		} else {
565df8bae1dSRodney W. Grimes 			if (m->m_len < sizeof(struct ip) + off) {
566c068736aSJeffrey Hsu 				if ((m = m_pullup(m, sizeof (struct ip) + off))
567c068736aSJeffrey Hsu 						== 0) {
568df8bae1dSRodney W. Grimes 					tcpstat.tcps_rcvshort++;
569df8bae1dSRodney W. Grimes 					return;
570df8bae1dSRodney W. Grimes 				}
571fb59c426SYoshinobu Inoue 				ip = mtod(m, struct ip *);
572fb59c426SYoshinobu Inoue 				ipov = (struct ipovly *)ip;
573fb59c426SYoshinobu Inoue 				th = (struct tcphdr *)((caddr_t)ip + off0);
574fb59c426SYoshinobu Inoue 			}
575df8bae1dSRodney W. Grimes 		}
576df8bae1dSRodney W. Grimes 		optlen = off - sizeof (struct tcphdr);
577fb59c426SYoshinobu Inoue 		optp = (u_char *)(th + 1);
578df8bae1dSRodney W. Grimes 	}
579fb59c426SYoshinobu Inoue 	thflags = th->th_flags;
580df8bae1dSRodney W. Grimes 
581e46cd3d4SDag-Erling Smørgrav #ifdef TCP_DROP_SYNFIN
582e46cd3d4SDag-Erling Smørgrav 	/*
583e46cd3d4SDag-Erling Smørgrav 	 * If the drop_synfin option is enabled, drop all packets with
584e46cd3d4SDag-Erling Smørgrav 	 * both the SYN and FIN bits set. This prevents e.g. nmap from
585e46cd3d4SDag-Erling Smørgrav 	 * identifying the TCP/IP stack.
586e46cd3d4SDag-Erling Smørgrav 	 *
587a589a70eSGarrett Wollman 	 * This is a violation of the TCP specification.
588e46cd3d4SDag-Erling Smørgrav 	 */
589fb59c426SYoshinobu Inoue 	if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN))
590e46cd3d4SDag-Erling Smørgrav 		goto drop;
591e46cd3d4SDag-Erling Smørgrav #endif
592e46cd3d4SDag-Erling Smørgrav 
593df8bae1dSRodney W. Grimes 	/*
594df8bae1dSRodney W. Grimes 	 * Convert TCP protocol specific fields to host format.
595df8bae1dSRodney W. Grimes 	 */
596fd8e4ebcSMike Barcroft 	th->th_seq = ntohl(th->th_seq);
597fd8e4ebcSMike Barcroft 	th->th_ack = ntohl(th->th_ack);
598fd8e4ebcSMike Barcroft 	th->th_win = ntohs(th->th_win);
599fd8e4ebcSMike Barcroft 	th->th_urp = ntohs(th->th_urp);
600df8bae1dSRodney W. Grimes 
601df8bae1dSRodney W. Grimes 	/*
6023bfd6421SJonathan Lemon 	 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options,
603fb59c426SYoshinobu Inoue 	 * until after ip6_savecontrol() is called and before other functions
604fb59c426SYoshinobu Inoue 	 * which don't want those proto headers.
605fb59c426SYoshinobu Inoue 	 * Because ip6_savecontrol() is going to parse the mbuf to
606fb59c426SYoshinobu Inoue 	 * search for data to be passed up to user-land, it wants mbuf
607fb59c426SYoshinobu Inoue 	 * parameters to be unchanged.
60888ff5695SSUZUKI Shinsuke 	 * XXX: the call of ip6_savecontrol() has been obsoleted based on
60988ff5695SSUZUKI Shinsuke 	 * latest version of the advanced API (20020110).
610755c1f07SAndras Olah 	 */
611fb59c426SYoshinobu Inoue 	drop_hdrlen = off0 + off;
612755c1f07SAndras Olah 
613755c1f07SAndras Olah 	/*
614df8bae1dSRodney W. Grimes 	 * Locate pcb for segment.
615df8bae1dSRodney W. Grimes 	 */
616f76fcf6dSJeffrey Hsu 	INP_INFO_WLOCK(&tcbinfo);
617f76fcf6dSJeffrey Hsu 	headlocked = 1;
618df8bae1dSRodney W. Grimes findpcb:
619de30ea13SRobert Watson 	KASSERT(headlocked, ("tcp_input: findpcb: head not locked"));
6209b932e9eSAndre Oppermann #ifdef IPFIREWALL_FORWARD
6219b932e9eSAndre Oppermann 	/* Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. */
6229b932e9eSAndre Oppermann 	fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
6239b932e9eSAndre Oppermann 
6249b932e9eSAndre Oppermann 	if (fwd_tag != NULL && isipv6 == 0) {	/* IPv6 support is not yet */
6259b932e9eSAndre Oppermann 		struct sockaddr_in *next_hop;
6269b932e9eSAndre Oppermann 
6279b932e9eSAndre Oppermann 		next_hop = (struct sockaddr_in *)(fwd_tag+1);
628f9e354dfSJulian Elischer 		/*
6292b25acc1SLuigi Rizzo 		 * Transparently forwarded. Pretend to be the destination.
630f9e354dfSJulian Elischer 		 * already got one like this?
631f9e354dfSJulian Elischer 		 */
6329b932e9eSAndre Oppermann 		inp = in_pcblookup_hash(&tcbinfo,
6339b932e9eSAndre Oppermann 					ip->ip_src, th->th_sport,
634c068736aSJeffrey Hsu 					ip->ip_dst, th->th_dport,
635c068736aSJeffrey Hsu 					0, m->m_pkthdr.rcvif);
636f9e354dfSJulian Elischer 		if (!inp) {
6379b932e9eSAndre Oppermann 			/* It's new.  Try to find the ambushing socket. */
638f9e354dfSJulian Elischer 			inp = in_pcblookup_hash(&tcbinfo,
639fb59c426SYoshinobu Inoue 						ip->ip_src, th->th_sport,
6402b25acc1SLuigi Rizzo 						next_hop->sin_addr,
641c068736aSJeffrey Hsu 						next_hop->sin_port ?
642c068736aSJeffrey Hsu 						    ntohs(next_hop->sin_port) :
643c068736aSJeffrey Hsu 						    th->th_dport,
644c068736aSJeffrey Hsu 						1, m->m_pkthdr.rcvif);
645f9e354dfSJulian Elischer 		}
6469b932e9eSAndre Oppermann 		/* Remove the tag from the packet.  We don't need it anymore. */
6479b932e9eSAndre Oppermann 		m_tag_delete(m, fwd_tag);
648c068736aSJeffrey Hsu 	} else {
6499b932e9eSAndre Oppermann #endif /* IPFIREWALL_FORWARD */
65004d3a452SHajimu UMEMOTO 		if (isipv6) {
65104d3a452SHajimu UMEMOTO #ifdef INET6
652c068736aSJeffrey Hsu 			inp = in6_pcblookup_hash(&tcbinfo,
653c068736aSJeffrey Hsu 						 &ip6->ip6_src, th->th_sport,
654c068736aSJeffrey Hsu 						 &ip6->ip6_dst, th->th_dport,
655c068736aSJeffrey Hsu 						 1, m->m_pkthdr.rcvif);
65604d3a452SHajimu UMEMOTO #endif
65704d3a452SHajimu UMEMOTO 		} else
658c068736aSJeffrey Hsu 			inp = in_pcblookup_hash(&tcbinfo,
659c068736aSJeffrey Hsu 						ip->ip_src, th->th_sport,
660c068736aSJeffrey Hsu 						ip->ip_dst, th->th_dport,
661c068736aSJeffrey Hsu 						1, m->m_pkthdr.rcvif);
6629b932e9eSAndre Oppermann #ifdef IPFIREWALL_FORWARD
663fb59c426SYoshinobu Inoue 	}
6649b932e9eSAndre Oppermann #endif /* IPFIREWALL_FORWARD */
665f9e354dfSJulian Elischer 
666da0f4099SHajimu UMEMOTO #if defined(IPSEC) || defined(FAST_IPSEC)
667d420fcdaSBruce M Simpson #ifdef INET6
668da0f4099SHajimu UMEMOTO 	if (isipv6) {
669da0f4099SHajimu UMEMOTO 		if (inp != NULL && ipsec6_in_reject(m, inp)) {
670fb59c426SYoshinobu Inoue #ifdef IPSEC
671fb59c426SYoshinobu Inoue 			ipsec6stat.in_polvio++;
672d420fcdaSBruce M Simpson #endif
673fb59c426SYoshinobu Inoue 			goto drop;
674fb59c426SYoshinobu Inoue 		}
675d420fcdaSBruce M Simpson 	} else
676d420fcdaSBruce M Simpson #endif /* INET6 */
677d420fcdaSBruce M Simpson 	if (inp != NULL && ipsec4_in_reject(m, inp)) {
678da0f4099SHajimu UMEMOTO #ifdef IPSEC
679fb59c426SYoshinobu Inoue 		ipsecstat.in_polvio++;
680d420fcdaSBruce M Simpson #endif
681fb59c426SYoshinobu Inoue 		goto drop;
682fb59c426SYoshinobu Inoue 	}
683da0f4099SHajimu UMEMOTO #endif /*IPSEC || FAST_IPSEC*/
684df8bae1dSRodney W. Grimes 
685df8bae1dSRodney W. Grimes 	/*
686df8bae1dSRodney W. Grimes 	 * If the state is CLOSED (i.e., TCB does not exist) then
687df8bae1dSRodney W. Grimes 	 * all data in the incoming segment is discarded.
688df8bae1dSRodney W. Grimes 	 * If the TCB exists but is in CLOSED state, it is embryonic,
689df8bae1dSRodney W. Grimes 	 * but should either do a listen or a connect soon.
690df8bae1dSRodney W. Grimes 	 */
691816a3d83SPoul-Henning Kamp 	if (inp == NULL) {
6922e4e1b4cSGeoff Rehmet 		if (log_in_vain) {
693fb59c426SYoshinobu Inoue #ifdef INET6
694ded7008aSJuli Mallett 			char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2];
695c068736aSJeffrey Hsu #else
696fb59c426SYoshinobu Inoue 			char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"];
697c068736aSJeffrey Hsu #endif
69875cfc95fSAndrey A. Chernov 
699fb59c426SYoshinobu Inoue 			if (isipv6) {
70004d3a452SHajimu UMEMOTO #ifdef INET6
701ded7008aSJuli Mallett 				strcpy(dbuf, "[");
702ded7008aSJuli Mallett 				strcpy(sbuf, "[");
703ded7008aSJuli Mallett 				strcat(dbuf, ip6_sprintf(&ip6->ip6_dst));
704ded7008aSJuli Mallett 				strcat(sbuf, ip6_sprintf(&ip6->ip6_src));
705ded7008aSJuli Mallett 				strcat(dbuf, "]");
706ded7008aSJuli Mallett 				strcat(sbuf, "]");
70704d3a452SHajimu UMEMOTO #endif
708c068736aSJeffrey Hsu 			} else {
709fb59c426SYoshinobu Inoue 				strcpy(dbuf, inet_ntoa(ip->ip_dst));
710fb59c426SYoshinobu Inoue 				strcpy(sbuf, inet_ntoa(ip->ip_src));
711fb59c426SYoshinobu Inoue 			}
7122e4e1b4cSGeoff Rehmet 			switch (log_in_vain) {
7132e4e1b4cSGeoff Rehmet 			case 1:
71439eb27a4SCrist J. Clark 				if ((thflags & TH_SYN) == 0)
7152e4e1b4cSGeoff Rehmet 					break;
716e4d2978dSPoul-Henning Kamp 				/* FALLTHROUGH */
7172e4e1b4cSGeoff Rehmet 			case 2:
7182e4e1b4cSGeoff Rehmet 				log(LOG_INFO,
719c068736aSJeffrey Hsu 				    "Connection attempt to TCP %s:%d "
72039eb27a4SCrist J. Clark 				    "from %s:%d flags:0x%02x\n",
721fb59c426SYoshinobu Inoue 				    dbuf, ntohs(th->th_dport), sbuf,
722fb59c426SYoshinobu Inoue 				    ntohs(th->th_sport), thflags);
7232e4e1b4cSGeoff Rehmet 				break;
7242e4e1b4cSGeoff Rehmet 			default:
7252e4e1b4cSGeoff Rehmet 				break;
7262e4e1b4cSGeoff Rehmet 			}
72775cfc95fSAndrey A. Chernov 		}
7282e4e1b4cSGeoff Rehmet 		if (blackhole) {
7292e4e1b4cSGeoff Rehmet 			switch (blackhole) {
730828b7f40SGeoff Rehmet 			case 1:
731fb59c426SYoshinobu Inoue 				if (thflags & TH_SYN)
732828b7f40SGeoff Rehmet 					goto drop;
733828b7f40SGeoff Rehmet 				break;
734828b7f40SGeoff Rehmet 			case 2:
735828b7f40SGeoff Rehmet 				goto drop;
736828b7f40SGeoff Rehmet 			default:
737828b7f40SGeoff Rehmet 				goto drop;
7382e4e1b4cSGeoff Rehmet 			}
739828b7f40SGeoff Rehmet 		}
740a57815efSBosko Milekic 		rstreason = BANDLIM_RST_CLOSEDPORT;
741a57815efSBosko Milekic 		goto dropwithreset;
742816a3d83SPoul-Henning Kamp 	}
743f76fcf6dSJeffrey Hsu 	INP_LOCK(inp);
744936cd18dSAndre Oppermann 
745936cd18dSAndre Oppermann 	/* Check the minimum TTL for socket. */
74634f83c52SGeorge V. Neville-Neil 	if (inp->inp_ip_minttl != 0) {
74734f83c52SGeorge V. Neville-Neil #ifdef INET6
74834f83c52SGeorge V. Neville-Neil 		if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim)
749936cd18dSAndre Oppermann 			goto drop;
75002707462SAndre Oppermann 		else
75134f83c52SGeorge V. Neville-Neil #endif
75234f83c52SGeorge V. Neville-Neil 		if (inp->inp_ip_minttl > ip->ip_ttl)
75334f83c52SGeorge V. Neville-Neil 			goto drop;
75434f83c52SGeorge V. Neville-Neil 	}
755936cd18dSAndre Oppermann 
756340c35deSJonathan Lemon 	if (inp->inp_vflag & INP_TIMEWAIT) {
757340c35deSJonathan Lemon 		/*
758340c35deSJonathan Lemon 		 * The only option of relevance is TOF_CC, and only if
759340c35deSJonathan Lemon 		 * present in a SYN segment.  See tcp_timewait().
760340c35deSJonathan Lemon 		 */
761340c35deSJonathan Lemon 		if (thflags & TH_SYN)
7625a53ca16SPaul Saab 			tcp_dooptions(&to, optp, optlen, 1);
763340c35deSJonathan Lemon 		if (tcp_timewait((struct tcptw *)inp->inp_ppcb,
764340c35deSJonathan Lemon 		    &to, th, m, tlen))
765340c35deSJonathan Lemon 			goto findpcb;
766340c35deSJonathan Lemon 		/*
767340c35deSJonathan Lemon 		 * tcp_timewait unlocks inp.
768340c35deSJonathan Lemon 		 */
769340c35deSJonathan Lemon 		INP_INFO_WUNLOCK(&tcbinfo);
770340c35deSJonathan Lemon 		return;
771340c35deSJonathan Lemon 	}
772df8bae1dSRodney W. Grimes 	tp = intotcpcb(inp);
77309f81a46SBosko Milekic 	if (tp == 0) {
774f76fcf6dSJeffrey Hsu 		INP_UNLOCK(inp);
775a57815efSBosko Milekic 		rstreason = BANDLIM_RST_CLOSEDPORT;
776a57815efSBosko Milekic 		goto dropwithreset;
77709f81a46SBosko Milekic 	}
778df8bae1dSRodney W. Grimes 	if (tp->t_state == TCPS_CLOSED)
779df8bae1dSRodney W. Grimes 		goto drop;
780df8bae1dSRodney W. Grimes 
781df8bae1dSRodney W. Grimes 	/* Unscale the window into a 32-bit value. */
782fb59c426SYoshinobu Inoue 	if ((thflags & TH_SYN) == 0)
783fb59c426SYoshinobu Inoue 		tiwin = th->th_win << tp->snd_scale;
784df8bae1dSRodney W. Grimes 	else
785fb59c426SYoshinobu Inoue 		tiwin = th->th_win;
786fb59c426SYoshinobu Inoue 
787c488362eSRobert Watson #ifdef MAC
7881f82efb3SRobert Watson 	INP_LOCK_ASSERT(inp);
789a557af22SRobert Watson 	if (mac_check_inpcb_deliver(inp, m))
790c488362eSRobert Watson 		goto drop;
791c488362eSRobert Watson #endif
792a557af22SRobert Watson 	so = inp->inp_socket;
793610ee2f9SDavid Greenman #ifdef TCPDEBUG
794df8bae1dSRodney W. Grimes 	if (so->so_options & SO_DEBUG) {
795df8bae1dSRodney W. Grimes 		ostate = tp->t_state;
796fb59c426SYoshinobu Inoue 		if (isipv6)
797540e8b7eSJeffrey Hsu 			bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6));
798fb59c426SYoshinobu Inoue 		else
799540e8b7eSJeffrey Hsu 			bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip));
800fb59c426SYoshinobu Inoue 		tcp_savetcp = *th;
801df8bae1dSRodney W. Grimes 	}
802610ee2f9SDavid Greenman #endif
803540e8b7eSJeffrey Hsu 	if (so->so_options & SO_ACCEPTCONN) {
804540e8b7eSJeffrey Hsu 		struct in_conninfo inc;
805540e8b7eSJeffrey Hsu 
806fb59c426SYoshinobu Inoue #ifdef INET6
807be2ac88cSJonathan Lemon 		inc.inc_isipv6 = isipv6;
808c068736aSJeffrey Hsu #endif
809be2ac88cSJonathan Lemon 		if (isipv6) {
810be2ac88cSJonathan Lemon 			inc.inc6_faddr = ip6->ip6_src;
811be2ac88cSJonathan Lemon 			inc.inc6_laddr = ip6->ip6_dst;
812c068736aSJeffrey Hsu 		} else {
813be2ac88cSJonathan Lemon 			inc.inc_faddr = ip->ip_src;
814be2ac88cSJonathan Lemon 			inc.inc_laddr = ip->ip_dst;
815be2ac88cSJonathan Lemon 		}
816be2ac88cSJonathan Lemon 		inc.inc_fport = th->th_sport;
817be2ac88cSJonathan Lemon 		inc.inc_lport = th->th_dport;
818be2ac88cSJonathan Lemon 
819fb59c426SYoshinobu Inoue 	        /*
820be2ac88cSJonathan Lemon 	         * If the state is LISTEN then ignore segment if it contains
821be2ac88cSJonathan Lemon 		 * a RST.  If the segment contains an ACK then it is bad and
822be2ac88cSJonathan Lemon 		 * send a RST.  If it does not contain a SYN then it is not
823be2ac88cSJonathan Lemon 		 * interesting; drop it.
824be2ac88cSJonathan Lemon 		 *
825be2ac88cSJonathan Lemon 		 * If the state is SYN_RECEIVED (syncache) and seg contains
826be2ac88cSJonathan Lemon 		 * an ACK, but not for our SYN/ACK, send a RST.  If the seg
827be2ac88cSJonathan Lemon 		 * contains a RST, check the sequence number to see if it
828be2ac88cSJonathan Lemon 		 * is a valid reset segment.
829fb59c426SYoshinobu Inoue 		 */
830fb59c426SYoshinobu Inoue 		if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) {
831be2ac88cSJonathan Lemon 			if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) {
832be2ac88cSJonathan Lemon 				if (!syncache_expand(&inc, th, &so, m)) {
8334195b4afSPaul Traina 					/*
834be2ac88cSJonathan Lemon 					 * No syncache entry, or ACK was not
835be2ac88cSJonathan Lemon 					 * for our SYN/ACK.  Send a RST.
8364195b4afSPaul Traina 					 */
837be2ac88cSJonathan Lemon 					tcpstat.tcps_badsyn++;
838be2ac88cSJonathan Lemon 					rstreason = BANDLIM_RST_OPENPORT;
839be2ac88cSJonathan Lemon 					goto dropwithreset;
840be2ac88cSJonathan Lemon 				}
841f76fcf6dSJeffrey Hsu 				if (so == NULL) {
842be2ac88cSJonathan Lemon 					/*
843be2ac88cSJonathan Lemon 					 * Could not complete 3-way handshake,
844be2ac88cSJonathan Lemon 					 * connection is being closed down, and
845be2ac88cSJonathan Lemon 					 * syncache will free mbuf.
846be2ac88cSJonathan Lemon 					 */
847f76fcf6dSJeffrey Hsu 					INP_UNLOCK(inp);
848f76fcf6dSJeffrey Hsu 					INP_INFO_WUNLOCK(&tcbinfo);
849be2ac88cSJonathan Lemon 					return;
850f76fcf6dSJeffrey Hsu 				}
851be2ac88cSJonathan Lemon 				/*
852be2ac88cSJonathan Lemon 				 * Socket is created in state SYN_RECEIVED.
853be2ac88cSJonathan Lemon 				 * Continue processing segment.
854be2ac88cSJonathan Lemon 				 */
855f76fcf6dSJeffrey Hsu 				INP_UNLOCK(inp);
856be2ac88cSJonathan Lemon 				inp = sotoinpcb(so);
857f76fcf6dSJeffrey Hsu 				INP_LOCK(inp);
858be2ac88cSJonathan Lemon 				tp = intotcpcb(inp);
859be2ac88cSJonathan Lemon 				/*
860be2ac88cSJonathan Lemon 				 * This is what would have happened in
861e6658b12SRobert Watson 				 * tcp_output() when the SYN,ACK was sent.
862be2ac88cSJonathan Lemon 				 */
863be2ac88cSJonathan Lemon 				tp->snd_up = tp->snd_una;
864be2ac88cSJonathan Lemon 				tp->snd_max = tp->snd_nxt = tp->iss + 1;
865be2ac88cSJonathan Lemon 				tp->last_ack_sent = tp->rcv_nxt;
866be2ac88cSJonathan Lemon 				/*
86741446225SJonathan Lemon 				 * RFC1323: The window in SYN & SYN/ACK
86841446225SJonathan Lemon 				 * segments is never scaled.
869be2ac88cSJonathan Lemon 				 */
870be2ac88cSJonathan Lemon 				tp->snd_wnd = tiwin;	/* unscaled */
871be2ac88cSJonathan Lemon 				goto after_listen;
872be2ac88cSJonathan Lemon 			}
873be2ac88cSJonathan Lemon 			if (thflags & TH_RST) {
874be2ac88cSJonathan Lemon 				syncache_chkrst(&inc, th);
875be2ac88cSJonathan Lemon 				goto drop;
876be2ac88cSJonathan Lemon 			}
877fb59c426SYoshinobu Inoue 			if (thflags & TH_ACK) {
878be2ac88cSJonathan Lemon 				syncache_badack(&inc);
879ebb0cbeaSPaul Traina 				tcpstat.tcps_badsyn++;
880a57815efSBosko Milekic 				rstreason = BANDLIM_RST_OPENPORT;
881a57815efSBosko Milekic 				goto dropwithreset;
8824195b4afSPaul Traina 			}
883ebb0cbeaSPaul Traina 			goto drop;
884ebb0cbeaSPaul Traina 		}
88533841545SHajimu UMEMOTO 
886be2ac88cSJonathan Lemon 		/*
887be2ac88cSJonathan Lemon 		 * Segment's flags are (SYN) or (SYN|FIN).
888be2ac88cSJonathan Lemon 		 */
88933841545SHajimu UMEMOTO #ifdef INET6
89033841545SHajimu UMEMOTO 		/*
89133841545SHajimu UMEMOTO 		 * If deprecated address is forbidden,
89233841545SHajimu UMEMOTO 		 * we do not accept SYN to deprecated interface
89333841545SHajimu UMEMOTO 		 * address to prevent any new inbound connection from
89433841545SHajimu UMEMOTO 		 * getting established.
89533841545SHajimu UMEMOTO 		 * When we do not accept SYN, we send a TCP RST,
89633841545SHajimu UMEMOTO 		 * with deprecated source address (instead of dropping
89733841545SHajimu UMEMOTO 		 * it).  We compromise it as it is much better for peer
89833841545SHajimu UMEMOTO 		 * to send a RST, and RST will be the final packet
89933841545SHajimu UMEMOTO 		 * for the exchange.
90033841545SHajimu UMEMOTO 		 *
90133841545SHajimu UMEMOTO 		 * If we do not forbid deprecated addresses, we accept
90233841545SHajimu UMEMOTO 		 * the SYN packet.  RFC2462 does not suggest dropping
90333841545SHajimu UMEMOTO 		 * SYN in this case.
90433841545SHajimu UMEMOTO 		 * If we decipher RFC2462 5.5.4, it says like this:
90533841545SHajimu UMEMOTO 		 * 1. use of deprecated addr with existing
90633841545SHajimu UMEMOTO 		 *    communication is okay - "SHOULD continue to be
90733841545SHajimu UMEMOTO 		 *    used"
90833841545SHajimu UMEMOTO 		 * 2. use of it with new communication:
90933841545SHajimu UMEMOTO 		 *   (2a) "SHOULD NOT be used if alternate address
91033841545SHajimu UMEMOTO 		 *        with sufficient scope is available"
91133841545SHajimu UMEMOTO 		 *   (2b) nothing mentioned otherwise.
91233841545SHajimu UMEMOTO 		 * Here we fall into (2b) case as we have no choice in
91333841545SHajimu UMEMOTO 		 * our source address selection - we must obey the peer.
91433841545SHajimu UMEMOTO 		 *
91533841545SHajimu UMEMOTO 		 * The wording in RFC2462 is confusing, and there are
91633841545SHajimu UMEMOTO 		 * multiple description text for deprecated address
91733841545SHajimu UMEMOTO 		 * handling - worse, they are not exactly the same.
91833841545SHajimu UMEMOTO 		 * I believe 5.5.4 is the best one, so we follow 5.5.4.
91933841545SHajimu UMEMOTO 		 */
92033841545SHajimu UMEMOTO 		if (isipv6 && !ip6_use_deprecated) {
92133841545SHajimu UMEMOTO 			struct in6_ifaddr *ia6;
92233841545SHajimu UMEMOTO 
92333841545SHajimu UMEMOTO 			if ((ia6 = ip6_getdstifaddr(m)) &&
92433841545SHajimu UMEMOTO 			    (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
925f76fcf6dSJeffrey Hsu 				INP_UNLOCK(inp);
92633841545SHajimu UMEMOTO 				tp = NULL;
92733841545SHajimu UMEMOTO 				rstreason = BANDLIM_RST_OPENPORT;
92833841545SHajimu UMEMOTO 				goto dropwithreset;
92933841545SHajimu UMEMOTO 			}
93033841545SHajimu UMEMOTO 		}
93133841545SHajimu UMEMOTO #endif
93265f28919SJesper Skriver 		/*
933be2ac88cSJonathan Lemon 		 * If it is from this socket, drop it, it must be forged.
934be2ac88cSJonathan Lemon 		 * Don't bother responding if the destination was a broadcast.
93565f28919SJesper Skriver 		 */
936be2ac88cSJonathan Lemon 		if (th->th_dport == th->th_sport) {
937fb59c426SYoshinobu Inoue 			if (isipv6) {
938be2ac88cSJonathan Lemon 				if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
939be2ac88cSJonathan Lemon 						       &ip6->ip6_src))
940be2ac88cSJonathan Lemon 					goto drop;
941c068736aSJeffrey Hsu 			} else {
942be2ac88cSJonathan Lemon 				if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
943be2ac88cSJonathan Lemon 					goto drop;
944be2ac88cSJonathan Lemon 			}
945c068736aSJeffrey Hsu 		}
946be2ac88cSJonathan Lemon 		/*
947be2ac88cSJonathan Lemon 		 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
9482ca2159fSCrist J. Clark 		 *
94993ec91baSCrist J. Clark 		 * Note that it is quite possible to receive unicast
95093ec91baSCrist J. Clark 		 * link-layer packets with a broadcast IP address. Use
95193ec91baSCrist J. Clark 		 * in_broadcast() to find them.
952be2ac88cSJonathan Lemon 		 */
953be2ac88cSJonathan Lemon 		if (m->m_flags & (M_BCAST|M_MCAST))
954be2ac88cSJonathan Lemon 			goto drop;
955be2ac88cSJonathan Lemon 		if (isipv6) {
956be2ac88cSJonathan Lemon 			if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
957be2ac88cSJonathan Lemon 			    IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
958be2ac88cSJonathan Lemon 				goto drop;
959c068736aSJeffrey Hsu 		} else {
960be2ac88cSJonathan Lemon 			if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
961be2ac88cSJonathan Lemon 			    IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
9622ca2159fSCrist J. Clark 			    ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
9632ca2159fSCrist J. Clark 			    in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
964be2ac88cSJonathan Lemon 				goto drop;
965c068736aSJeffrey Hsu 		}
966be2ac88cSJonathan Lemon 		/*
967be2ac88cSJonathan Lemon 		 * SYN appears to be valid; create compressed TCP state
968be2ac88cSJonathan Lemon 		 * for syncache, or perform t/tcp connection.
969be2ac88cSJonathan Lemon 		 */
970be2ac88cSJonathan Lemon 		if (so->so_qlen <= so->so_qlimit) {
9713c653157SHartmut Brandt #ifdef TCPDEBUG
9723c653157SHartmut Brandt 			if (so->so_options & SO_DEBUG)
9733c653157SHartmut Brandt 				tcp_trace(TA_INPUT, ostate, tp,
9743c653157SHartmut Brandt 				    (void *)tcp_saveipgen, &tcp_savetcp, 0);
9753c653157SHartmut Brandt #endif
9765a53ca16SPaul Saab 			tcp_dooptions(&to, optp, optlen, 1);
977be2ac88cSJonathan Lemon 			if (!syncache_add(&inc, &to, th, &so, m))
978be2ac88cSJonathan Lemon 				goto drop;
979f76fcf6dSJeffrey Hsu 			if (so == NULL) {
980be2ac88cSJonathan Lemon 				/*
981be2ac88cSJonathan Lemon 				 * Entry added to syncache, mbuf used to
982be2ac88cSJonathan Lemon 				 * send SYN,ACK packet.
983be2ac88cSJonathan Lemon 				 */
984f76fcf6dSJeffrey Hsu 				KASSERT(headlocked, ("headlocked"));
985f76fcf6dSJeffrey Hsu 				INP_UNLOCK(inp);
986f76fcf6dSJeffrey Hsu 				INP_INFO_WUNLOCK(&tcbinfo);
987be2ac88cSJonathan Lemon 				return;
988f76fcf6dSJeffrey Hsu 			}
989be2ac88cSJonathan Lemon 			/*
990be2ac88cSJonathan Lemon 			 * Segment passed TAO tests.
991be2ac88cSJonathan Lemon 			 */
992f76fcf6dSJeffrey Hsu 			INP_UNLOCK(inp);
993be2ac88cSJonathan Lemon 			inp = sotoinpcb(so);
994f76fcf6dSJeffrey Hsu 			INP_LOCK(inp);
995df8bae1dSRodney W. Grimes 			tp = intotcpcb(inp);
996be2ac88cSJonathan Lemon 			tp->snd_wnd = tiwin;
997be2ac88cSJonathan Lemon 			tp->t_starttime = ticks;
998be2ac88cSJonathan Lemon 			tp->t_state = TCPS_ESTABLISHED;
999df8bae1dSRodney W. Grimes 
1000be2ac88cSJonathan Lemon 			/*
10013bfd6421SJonathan Lemon 			 * T/TCP logic:
10023bfd6421SJonathan Lemon 			 * If there is a FIN or if there is data, then
10033bfd6421SJonathan Lemon 			 * delay SYN,ACK(SYN) in the hope of piggy-backing
10043bfd6421SJonathan Lemon 			 * it on a response segment.  Otherwise must send
10053bfd6421SJonathan Lemon 			 * ACK now in case the other side is slow starting.
1006be2ac88cSJonathan Lemon 			 */
10073bfd6421SJonathan Lemon 			if (thflags & TH_FIN || tlen != 0)
10083bfd6421SJonathan Lemon 				tp->t_flags |= (TF_DELACK | TF_NEEDSYN);
10093bfd6421SJonathan Lemon 			else
1010f243998bSJonathan Lemon 				tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
1011be2ac88cSJonathan Lemon 			tcpstat.tcps_connects++;
1012be2ac88cSJonathan Lemon 			soisconnected(so);
1013be2ac88cSJonathan Lemon 			goto trimthenstep6;
1014df8bae1dSRodney W. Grimes 		}
1015be2ac88cSJonathan Lemon 		goto drop;
10164cc20ab1SSeigo Tanimura 	}
1017be2ac88cSJonathan Lemon after_listen:
1018de30ea13SRobert Watson 	KASSERT(headlocked, ("tcp_input: after_listen: head not locked"));
10197cfc6904SRobert Watson 	INP_LOCK_ASSERT(inp);
1020be2ac88cSJonathan Lemon 
1021a65e12b0SRobert Watson 	/* Syncache takes care of sockets in the listen state. */
1022a65e12b0SRobert Watson 	KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN"));
1023df8bae1dSRodney W. Grimes 
1024df8bae1dSRodney W. Grimes 	/*
102553369ac9SAndre Oppermann 	 * This is the second part of the MSS DoS prevention code (after
102653369ac9SAndre Oppermann 	 * minmss on the sending side) and it deals with too many too small
102753369ac9SAndre Oppermann 	 * tcp packets in a too short timeframe (1 second).
102853369ac9SAndre Oppermann 	 *
102953369ac9SAndre Oppermann 	 * For every full second we count the number of received packets
103053369ac9SAndre Oppermann 	 * and bytes. If we get a lot of packets per second for this connection
103153369ac9SAndre Oppermann 	 * (tcp_minmssoverload) we take a closer look at it and compute the
103253369ac9SAndre Oppermann 	 * average packet size for the past second. If that is less than
103353369ac9SAndre Oppermann 	 * tcp_minmss we get too many packets with very small payload which
103453369ac9SAndre Oppermann 	 * is not good and burdens our system (and every packet generates
103553369ac9SAndre Oppermann 	 * a wakeup to the process connected to our socket). We can reasonable
103653369ac9SAndre Oppermann 	 * expect this to be small packet DoS attack to exhaust our CPU
103753369ac9SAndre Oppermann 	 * cycles.
103853369ac9SAndre Oppermann 	 *
103953369ac9SAndre Oppermann 	 * Care has to be taken for the minimum packet overload value. This
104053369ac9SAndre Oppermann 	 * value defines the minimum number of packets per second before we
104153369ac9SAndre Oppermann 	 * start to worry. This must not be too low to avoid killing for
104253369ac9SAndre Oppermann 	 * example interactive connections with many small packets like
104353369ac9SAndre Oppermann 	 * telnet or SSH.
104453369ac9SAndre Oppermann 	 *
104553369ac9SAndre Oppermann 	 * Setting either tcp_minmssoverload or tcp_minmss to "0" disables
104653369ac9SAndre Oppermann 	 * this check.
104753369ac9SAndre Oppermann 	 *
104853369ac9SAndre Oppermann 	 * Account for packet if payload packet, skip over ACK, etc.
104953369ac9SAndre Oppermann 	 */
105053369ac9SAndre Oppermann 	if (tcp_minmss && tcp_minmssoverload &&
105153369ac9SAndre Oppermann 	    tp->t_state == TCPS_ESTABLISHED && tlen > 0) {
105268d37625SStephan Uphoff 		if ((unsigned int)(tp->rcv_second - ticks) < hz) {
105353369ac9SAndre Oppermann 			tp->rcv_pps++;
105453369ac9SAndre Oppermann 			tp->rcv_byps += tlen + off;
105553369ac9SAndre Oppermann 			if (tp->rcv_pps > tcp_minmssoverload) {
105653369ac9SAndre Oppermann 				if ((tp->rcv_byps / tp->rcv_pps) < tcp_minmss) {
105753369ac9SAndre Oppermann 					printf("too many small tcp packets from "
105853369ac9SAndre Oppermann 					       "%s:%u, av. %lubyte/packet, "
105953369ac9SAndre Oppermann 					       "dropping connection\n",
106053369ac9SAndre Oppermann #ifdef INET6
106153369ac9SAndre Oppermann 						isipv6 ?
106253369ac9SAndre Oppermann 						ip6_sprintf(&inp->inp_inc.inc6_faddr) :
106353369ac9SAndre Oppermann #endif
106453369ac9SAndre Oppermann 						inet_ntoa(inp->inp_inc.inc_faddr),
106553369ac9SAndre Oppermann 						inp->inp_inc.inc_fport,
106653369ac9SAndre Oppermann 						tp->rcv_byps / tp->rcv_pps);
10671e2d989dSRobert Watson 					KASSERT(headlocked, ("tcp_input: "
10681e2d989dSRobert Watson 					    "after_listen: tcp_drop: head "
10691e2d989dSRobert Watson 					    "not locked"));
107053369ac9SAndre Oppermann 					tp = tcp_drop(tp, ECONNRESET);
107153369ac9SAndre Oppermann 					tcpstat.tcps_minmssdrops++;
107253369ac9SAndre Oppermann 					goto drop;
107353369ac9SAndre Oppermann 				}
107453369ac9SAndre Oppermann 			}
107553369ac9SAndre Oppermann 		} else {
107653369ac9SAndre Oppermann 			tp->rcv_second = ticks + hz;
107753369ac9SAndre Oppermann 			tp->rcv_pps = 1;
107853369ac9SAndre Oppermann 			tp->rcv_byps = tlen + off;
107953369ac9SAndre Oppermann 		}
108053369ac9SAndre Oppermann 	}
108153369ac9SAndre Oppermann 
108253369ac9SAndre Oppermann 	/*
1083df8bae1dSRodney W. Grimes 	 * Segment received on connection.
1084df8bae1dSRodney W. Grimes 	 * Reset idle time and keep-alive timer.
1085df8bae1dSRodney W. Grimes 	 */
10869b8b58e0SJonathan Lemon 	tp->t_rcvtime = ticks;
10877ff19458SPaul Traina 	if (TCPS_HAVEESTABLISHED(tp->t_state))
10889b8b58e0SJonathan Lemon 		callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp);
1089df8bae1dSRodney W. Grimes 
1090df8bae1dSRodney W. Grimes 	/*
109197d8d152SAndre Oppermann 	 * Process options only when we get SYN/ACK back. The SYN case
109297d8d152SAndre Oppermann 	 * for incoming connections is handled in tcp_syncache.
109397d8d152SAndre Oppermann 	 * XXX this is traditional behavior, may need to be cleaned up.
1094df8bae1dSRodney W. Grimes 	 */
10955a53ca16SPaul Saab 	tcp_dooptions(&to, optp, optlen, thflags & TH_SYN);
10960a389eabSSimon L. B. Nielsen 	if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
1097be2ac88cSJonathan Lemon 		if (to.to_flags & TOF_SCALE) {
1098be2ac88cSJonathan Lemon 			tp->t_flags |= TF_RCVD_SCALE;
1099be2ac88cSJonathan Lemon 			tp->requested_s_scale = to.to_requested_s_scale;
1100be2ac88cSJonathan Lemon 		}
1101be2ac88cSJonathan Lemon 		if (to.to_flags & TOF_TS) {
1102be2ac88cSJonathan Lemon 			tp->t_flags |= TF_RCVD_TSTMP;
1103be2ac88cSJonathan Lemon 			tp->ts_recent = to.to_tsval;
1104be2ac88cSJonathan Lemon 			tp->ts_recent_age = ticks;
1105be2ac88cSJonathan Lemon 		}
1106be2ac88cSJonathan Lemon 		if (to.to_flags & TOF_MSS)
1107be2ac88cSJonathan Lemon 			tcp_mss(tp, to.to_mss);
11086d90faf3SPaul Saab 		if (tp->sack_enable) {
11096d90faf3SPaul Saab 			if (!(to.to_flags & TOF_SACK))
11106d90faf3SPaul Saab 				tp->sack_enable = 0;
11116d90faf3SPaul Saab 			else
11126d90faf3SPaul Saab 				tp->t_flags |= TF_SACK_PERMIT;
11136d90faf3SPaul Saab 		}
11146d90faf3SPaul Saab 
11156d90faf3SPaul Saab 	}
11166d90faf3SPaul Saab 
1117df8bae1dSRodney W. Grimes 	/*
1118df8bae1dSRodney W. Grimes 	 * Header prediction: check for the two common cases
1119df8bae1dSRodney W. Grimes 	 * of a uni-directional data xfer.  If the packet has
1120df8bae1dSRodney W. Grimes 	 * no control flags, is in-sequence, the window didn't
1121df8bae1dSRodney W. Grimes 	 * change and we're not retransmitting, it's a
1122df8bae1dSRodney W. Grimes 	 * candidate.  If the length is zero and the ack moved
1123df8bae1dSRodney W. Grimes 	 * forward, we're the sender side of the xfer.  Just
1124df8bae1dSRodney W. Grimes 	 * free the data acked & wake any higher level process
1125df8bae1dSRodney W. Grimes 	 * that was blocked waiting for space.  If the length
1126df8bae1dSRodney W. Grimes 	 * is non-zero and the ack didn't move, we're the
1127df8bae1dSRodney W. Grimes 	 * receiver side.  If we're getting packets in-order
1128df8bae1dSRodney W. Grimes 	 * (the reassembly queue is empty), add the data to
1129df8bae1dSRodney W. Grimes 	 * the socket buffer and note that we need a delayed ack.
1130a0292f23SGarrett Wollman 	 * Make sure that the hidden state-flags are also off.
1131a0292f23SGarrett Wollman 	 * Since we check for TCPS_ESTABLISHED above, it can only
1132a0292f23SGarrett Wollman 	 * be TH_NEEDSYN.
1133df8bae1dSRodney W. Grimes 	 */
1134df8bae1dSRodney W. Grimes 	if (tp->t_state == TCPS_ESTABLISHED &&
1135fb59c426SYoshinobu Inoue 	    (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
1136a0292f23SGarrett Wollman 	    ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
1137be2ac88cSJonathan Lemon 	    ((to.to_flags & TOF_TS) == 0 ||
1138a0292f23SGarrett Wollman 	     TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
1139c94c54e4SAndre Oppermann 	     th->th_seq == tp->rcv_nxt && tiwin && tiwin == tp->snd_wnd &&
1140df8bae1dSRodney W. Grimes 	     tp->snd_nxt == tp->snd_max) {
1141df8bae1dSRodney W. Grimes 
1142df8bae1dSRodney W. Grimes 		/*
1143df8bae1dSRodney W. Grimes 		 * If last ACK falls within this segment's sequence numbers,
1144df8bae1dSRodney W. Grimes 		 * record the timestamp.
1145a0292f23SGarrett Wollman 		 * NOTE that the test is modified according to the latest
1146a0292f23SGarrett Wollman 		 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1147df8bae1dSRodney W. Grimes 		 */
1148be2ac88cSJonathan Lemon 		if ((to.to_flags & TOF_TS) != 0 &&
1149fb59c426SYoshinobu Inoue 		    SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
11509b8b58e0SJonathan Lemon 			tp->ts_recent_age = ticks;
1151a0292f23SGarrett Wollman 			tp->ts_recent = to.to_tsval;
1152df8bae1dSRodney W. Grimes 		}
1153df8bae1dSRodney W. Grimes 
1154fb59c426SYoshinobu Inoue 		if (tlen == 0) {
1155fb59c426SYoshinobu Inoue 			if (SEQ_GT(th->th_ack, tp->snd_una) &&
1156fb59c426SYoshinobu Inoue 			    SEQ_LEQ(th->th_ack, tp->snd_max) &&
1157233e8c18SGarrett Wollman 			    tp->snd_cwnd >= tp->snd_wnd &&
11586d90faf3SPaul Saab 			    ((!tcp_do_newreno && !tp->sack_enable &&
1159cb942153SJeffrey Hsu 			      tp->t_dupacks < tcprexmtthresh) ||
11606d90faf3SPaul Saab 			     ((tcp_do_newreno || tp->sack_enable) &&
1161482ac968SPaul Saab 			      !IN_FASTRECOVERY(tp) && to.to_nsacks == 0 &&
1162482ac968SPaul Saab 			      TAILQ_EMPTY(&tp->snd_holes)))) {
1163f76fcf6dSJeffrey Hsu 				KASSERT(headlocked, ("headlocked"));
1164e0bef1cbSRobert Watson 				INP_INFO_WUNLOCK(&tcbinfo);
1165e0bef1cbSRobert Watson 				headlocked = 0;
1166df8bae1dSRodney W. Grimes 				/*
1167df8bae1dSRodney W. Grimes 				 * this is a pure ack for outstanding data.
1168df8bae1dSRodney W. Grimes 				 */
1169df8bae1dSRodney W. Grimes 				++tcpstat.tcps_predack;
11709b8b58e0SJonathan Lemon 				/*
11719b8b58e0SJonathan Lemon 				 * "bad retransmit" recovery
11729b8b58e0SJonathan Lemon 				 */
11739b8b58e0SJonathan Lemon 				if (tp->t_rxtshift == 1 &&
11749b8b58e0SJonathan Lemon 				    ticks < tp->t_badrxtwin) {
1175cb942153SJeffrey Hsu 					++tcpstat.tcps_sndrexmitbad;
11769b8b58e0SJonathan Lemon 					tp->snd_cwnd = tp->snd_cwnd_prev;
11779b8b58e0SJonathan Lemon 					tp->snd_ssthresh =
11789b8b58e0SJonathan Lemon 					    tp->snd_ssthresh_prev;
11799d11646dSJeffrey Hsu 					tp->snd_recover = tp->snd_recover_prev;
11809d11646dSJeffrey Hsu 					if (tp->t_flags & TF_WASFRECOVERY)
11819d11646dSJeffrey Hsu 					    ENTER_FASTRECOVERY(tp);
11829b8b58e0SJonathan Lemon 					tp->snd_nxt = tp->snd_max;
11839b8b58e0SJonathan Lemon 					tp->t_badrxtwin = 0;
11849b8b58e0SJonathan Lemon 				}
1185fa55172bSMatthew Dillon 
1186fa55172bSMatthew Dillon 				/*
1187fa55172bSMatthew Dillon 				 * Recalculate the transmit timer / rtt.
1188fa55172bSMatthew Dillon 				 *
1189fa55172bSMatthew Dillon 				 * Some boxes send broken timestamp replies
1190fa55172bSMatthew Dillon 				 * during the SYN+ACK phase, ignore
1191fa55172bSMatthew Dillon 				 * timestamps of 0 or we could calculate a
1192fa55172bSMatthew Dillon 				 * huge RTT and blow up the retransmit timer.
1193fa55172bSMatthew Dillon 				 */
1194fa55172bSMatthew Dillon 				if ((to.to_flags & TOF_TS) != 0 &&
1195fa55172bSMatthew Dillon 				    to.to_tsecr) {
1196eaf80179SAndre Oppermann 					if (!tp->t_rttlow ||
1197eaf80179SAndre Oppermann 					    tp->t_rttlow > ticks - to.to_tsecr)
1198eaf80179SAndre Oppermann 						tp->t_rttlow = ticks - to.to_tsecr;
1199a0292f23SGarrett Wollman 					tcp_xmit_timer(tp,
12009b8b58e0SJonathan Lemon 					    ticks - to.to_tsecr + 1);
1201fa55172bSMatthew Dillon 				} else if (tp->t_rtttime &&
1202fa55172bSMatthew Dillon 					    SEQ_GT(th->th_ack, tp->t_rtseq)) {
1203eaf80179SAndre Oppermann 					if (!tp->t_rttlow ||
1204eaf80179SAndre Oppermann 					    tp->t_rttlow > ticks - tp->t_rtttime)
1205eaf80179SAndre Oppermann 						tp->t_rttlow = ticks - tp->t_rtttime;
1206c068736aSJeffrey Hsu 					tcp_xmit_timer(tp,
1207c068736aSJeffrey Hsu 							ticks - tp->t_rtttime);
1208fa55172bSMatthew Dillon 				}
12091fcc99b5SMatthew Dillon 				tcp_xmit_bandwidth_limit(tp, th->th_ack);
1210fb59c426SYoshinobu Inoue 				acked = th->th_ack - tp->snd_una;
1211df8bae1dSRodney W. Grimes 				tcpstat.tcps_rcvackpack++;
1212df8bae1dSRodney W. Grimes 				tcpstat.tcps_rcvackbyte += acked;
1213df8bae1dSRodney W. Grimes 				sbdrop(&so->so_snd, acked);
12149d11646dSJeffrey Hsu 				if (SEQ_GT(tp->snd_una, tp->snd_recover) &&
12159d11646dSJeffrey Hsu 				    SEQ_LEQ(th->th_ack, tp->snd_recover))
12169d11646dSJeffrey Hsu 					tp->snd_recover = th->th_ack - 1;
12179d11646dSJeffrey Hsu 				tp->snd_una = th->th_ack;
12181645d090SJeff Roberson 				/*
12191645d090SJeff Roberson 				 * pull snd_wl2 up to prevent seq wrap relative
12201645d090SJeff Roberson 				 * to th_ack.
12211645d090SJeff Roberson 				 */
1222cb942153SJeffrey Hsu 				tp->snd_wl2 = th->th_ack;
1223b5addd85SJeffrey Hsu 				tp->t_dupacks = 0;
1224df8bae1dSRodney W. Grimes 				m_freem(m);
1225fb59c426SYoshinobu Inoue 				ND6_HINT(tp); /* some progress has been done */
1226df8bae1dSRodney W. Grimes 
1227df8bae1dSRodney W. Grimes 				/*
1228df8bae1dSRodney W. Grimes 				 * If all outstanding data are acked, stop
1229df8bae1dSRodney W. Grimes 				 * retransmit timer, otherwise restart timer
1230df8bae1dSRodney W. Grimes 				 * using current (possibly backed-off) value.
1231df8bae1dSRodney W. Grimes 				 * If process is waiting for space,
1232df8bae1dSRodney W. Grimes 				 * wakeup/selwakeup/signal.  If data
1233df8bae1dSRodney W. Grimes 				 * are ready to send, let tcp_output
1234df8bae1dSRodney W. Grimes 				 * decide between more output or persist.
12353c653157SHartmut Brandt 
12363c653157SHartmut Brandt #ifdef TCPDEBUG
12373c653157SHartmut Brandt 				if (so->so_options & SO_DEBUG)
12383c653157SHartmut Brandt 					tcp_trace(TA_INPUT, ostate, tp,
12393c653157SHartmut Brandt 					    (void *)tcp_saveipgen,
12403c653157SHartmut Brandt 					    &tcp_savetcp, 0);
12413c653157SHartmut Brandt #endif
1242df8bae1dSRodney W. Grimes 				 */
1243df8bae1dSRodney W. Grimes 				if (tp->snd_una == tp->snd_max)
12449b8b58e0SJonathan Lemon 					callout_stop(tp->tt_rexmt);
12459b8b58e0SJonathan Lemon 				else if (!callout_active(tp->tt_persist))
12469b8b58e0SJonathan Lemon 					callout_reset(tp->tt_rexmt,
12479b8b58e0SJonathan Lemon 						      tp->t_rxtcur,
12489b8b58e0SJonathan Lemon 						      tcp_timer_rexmt, tp);
1249df8bae1dSRodney W. Grimes 
1250df8bae1dSRodney W. Grimes 				sowwakeup(so);
1251df8bae1dSRodney W. Grimes 				if (so->so_snd.sb_cc)
1252df8bae1dSRodney W. Grimes 					(void) tcp_output(tp);
1253a14c749fSJonathan Lemon 				goto check_delack;
1254df8bae1dSRodney W. Grimes 			}
1255fb59c426SYoshinobu Inoue 		} else if (th->th_ack == tp->snd_una &&
1256fb59c426SYoshinobu Inoue 		    LIST_EMPTY(&tp->t_segq) &&
1257fb59c426SYoshinobu Inoue 		    tlen <= sbspace(&so->so_rcv)) {
1258f76fcf6dSJeffrey Hsu 			KASSERT(headlocked, ("headlocked"));
1259e0bef1cbSRobert Watson 			INP_INFO_WUNLOCK(&tcbinfo);
1260e0bef1cbSRobert Watson 			headlocked = 0;
1261df8bae1dSRodney W. Grimes 			/*
1262df8bae1dSRodney W. Grimes 			 * this is a pure, in-sequence data packet
1263df8bae1dSRodney W. Grimes 			 * with nothing on the reassembly queue and
1264df8bae1dSRodney W. Grimes 			 * we have enough buffer space to take it.
1265df8bae1dSRodney W. Grimes 			 */
12666d90faf3SPaul Saab 			/* Clean receiver SACK report if present */
12676d90faf3SPaul Saab 			if (tp->sack_enable && tp->rcv_numsacks)
12686d90faf3SPaul Saab 				tcp_clean_sackreport(tp);
1269df8bae1dSRodney W. Grimes 			++tcpstat.tcps_preddat;
1270fb59c426SYoshinobu Inoue 			tp->rcv_nxt += tlen;
12711645d090SJeff Roberson 			/*
12721645d090SJeff Roberson 			 * Pull snd_wl1 up to prevent seq wrap relative to
12731645d090SJeff Roberson 			 * th_seq.
12741645d090SJeff Roberson 			 */
12751645d090SJeff Roberson 			tp->snd_wl1 = th->th_seq;
12761645d090SJeff Roberson 			/*
12771645d090SJeff Roberson 			 * Pull rcv_up up to prevent seq wrap relative to
12781645d090SJeff Roberson 			 * rcv_nxt.
12791645d090SJeff Roberson 			 */
12801645d090SJeff Roberson 			tp->rcv_up = tp->rcv_nxt;
1281df8bae1dSRodney W. Grimes 			tcpstat.tcps_rcvpack++;
1282fb59c426SYoshinobu Inoue 			tcpstat.tcps_rcvbyte += tlen;
1283fb59c426SYoshinobu Inoue 			ND6_HINT(tp);	/* some progress has been done */
1284df8bae1dSRodney W. Grimes 			/*
12853c653157SHartmut Brandt #ifdef TCPDEBUG
12863c653157SHartmut Brandt 			if (so->so_options & SO_DEBUG)
12873c653157SHartmut Brandt 				tcp_trace(TA_INPUT, ostate, tp,
12883c653157SHartmut Brandt 				    (void *)tcp_saveipgen, &tcp_savetcp, 0);
12893c653157SHartmut Brandt #endif
1290755c1f07SAndras Olah 			 * Add data to socket buffer.
1291df8bae1dSRodney W. Grimes 			 */
12921e4d7da7SRobert Watson 			SOCKBUF_LOCK(&so->so_rcv);
1293c0b99ffaSRobert Watson 			if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
1294c1c36a2cSMike Silbersack 				m_freem(m);
1295c1c36a2cSMike Silbersack 			} else {
1296fb59c426SYoshinobu Inoue 				m_adj(m, drop_hdrlen);	/* delayed header drop */
12971e4d7da7SRobert Watson 				sbappendstream_locked(&so->so_rcv, m);
1298c1c36a2cSMike Silbersack 			}
12991e4d7da7SRobert Watson 			sorwakeup_locked(so);
1300d8c85a26SJonathan Lemon 			if (DELAY_ACK(tp)) {
13013bfd6421SJonathan Lemon 				tp->t_flags |= TF_DELACK;
1302f498eeeeSDavid Greenman 			} else {
1303e612a582SDavid Greenman 				tp->t_flags |= TF_ACKNOW;
1304e612a582SDavid Greenman 				tcp_output(tp);
1305e612a582SDavid Greenman 			}
1306a14c749fSJonathan Lemon 			goto check_delack;
1307df8bae1dSRodney W. Grimes 		}
1308df8bae1dSRodney W. Grimes 	}
1309df8bae1dSRodney W. Grimes 
1310df8bae1dSRodney W. Grimes 	/*
1311df8bae1dSRodney W. Grimes 	 * Calculate amount of space in receive window,
1312df8bae1dSRodney W. Grimes 	 * and then do TCP input processing.
1313df8bae1dSRodney W. Grimes 	 * Receive window is amount of space in rcv queue,
1314df8bae1dSRodney W. Grimes 	 * but not less than advertised window.
1315df8bae1dSRodney W. Grimes 	 */
1316df8bae1dSRodney W. Grimes 	{ int win;
1317df8bae1dSRodney W. Grimes 
1318df8bae1dSRodney W. Grimes 	win = sbspace(&so->so_rcv);
1319df8bae1dSRodney W. Grimes 	if (win < 0)
1320df8bae1dSRodney W. Grimes 		win = 0;
132166e39adcSJohn Polstra 	tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
1322df8bae1dSRodney W. Grimes 	}
1323df8bae1dSRodney W. Grimes 
1324df8bae1dSRodney W. Grimes 	switch (tp->t_state) {
1325df8bae1dSRodney W. Grimes 
1326df8bae1dSRodney W. Grimes 	/*
1327764d8cefSBill Fenner 	 * If the state is SYN_RECEIVED:
1328764d8cefSBill Fenner 	 *	if seg contains an ACK, but not for our SYN/ACK, send a RST.
1329764d8cefSBill Fenner 	 */
1330764d8cefSBill Fenner 	case TCPS_SYN_RECEIVED:
1331fb59c426SYoshinobu Inoue 		if ((thflags & TH_ACK) &&
1332fb59c426SYoshinobu Inoue 		    (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1333a57815efSBosko Milekic 		     SEQ_GT(th->th_ack, tp->snd_max))) {
1334a57815efSBosko Milekic 				rstreason = BANDLIM_RST_OPENPORT;
1335a57815efSBosko Milekic 				goto dropwithreset;
1336a57815efSBosko Milekic 		}
1337764d8cefSBill Fenner 		break;
1338764d8cefSBill Fenner 
1339764d8cefSBill Fenner 	/*
1340df8bae1dSRodney W. Grimes 	 * If the state is SYN_SENT:
1341df8bae1dSRodney W. Grimes 	 *	if seg contains an ACK, but not for our SYN, drop the input.
1342df8bae1dSRodney W. Grimes 	 *	if seg contains a RST, then drop the connection.
1343df8bae1dSRodney W. Grimes 	 *	if seg does not contain SYN, then drop it.
1344df8bae1dSRodney W. Grimes 	 * Otherwise this is an acceptable SYN segment
1345df8bae1dSRodney W. Grimes 	 *	initialize tp->rcv_nxt and tp->irs
1346df8bae1dSRodney W. Grimes 	 *	if seg contains ack then advance tp->snd_una
1347df8bae1dSRodney W. Grimes 	 *	if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1348df8bae1dSRodney W. Grimes 	 *	arrange for segment to be acked (eventually)
1349df8bae1dSRodney W. Grimes 	 *	continue processing rest of data/controls, beginning with URG
1350df8bae1dSRodney W. Grimes 	 */
1351df8bae1dSRodney W. Grimes 	case TCPS_SYN_SENT:
1352fb59c426SYoshinobu Inoue 		if ((thflags & TH_ACK) &&
1353fb59c426SYoshinobu Inoue 		    (SEQ_LEQ(th->th_ack, tp->iss) ||
1354fb59c426SYoshinobu Inoue 		     SEQ_GT(th->th_ack, tp->snd_max))) {
1355a57815efSBosko Milekic 			rstreason = BANDLIM_UNLIMITED;
1356a0292f23SGarrett Wollman 			goto dropwithreset;
1357a0292f23SGarrett Wollman 		}
1358fb59c426SYoshinobu Inoue 		if (thflags & TH_RST) {
13591e2d989dSRobert Watson 			if (thflags & TH_ACK) {
13601e2d989dSRobert Watson 				KASSERT(headlocked, ("tcp_input: after_listen"
13611e2d989dSRobert Watson 				    ": tcp_drop.2: head not locked"));
1362df8bae1dSRodney W. Grimes 				tp = tcp_drop(tp, ECONNREFUSED);
13631e2d989dSRobert Watson 			}
1364df8bae1dSRodney W. Grimes 			goto drop;
1365df8bae1dSRodney W. Grimes 		}
1366fb59c426SYoshinobu Inoue 		if ((thflags & TH_SYN) == 0)
1367df8bae1dSRodney W. Grimes 			goto drop;
1368fb59c426SYoshinobu Inoue 		tp->snd_wnd = th->th_win;	/* initial send window */
1369a0292f23SGarrett Wollman 
1370fb59c426SYoshinobu Inoue 		tp->irs = th->th_seq;
1371df8bae1dSRodney W. Grimes 		tcp_rcvseqinit(tp);
1372fb59c426SYoshinobu Inoue 		if (thflags & TH_ACK) {
1373845799c1SAndras Olah 			tcpstat.tcps_connects++;
1374845799c1SAndras Olah 			soisconnected(so);
1375c488362eSRobert Watson #ifdef MAC
1376310e7cebSRobert Watson 			SOCK_LOCK(so);
1377c488362eSRobert Watson 			mac_set_socket_peer_from_mbuf(m, so);
1378310e7cebSRobert Watson 			SOCK_UNLOCK(so);
1379c488362eSRobert Watson #endif
1380845799c1SAndras Olah 			/* Do window scaling on this connection? */
1381845799c1SAndras Olah 			if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1382845799c1SAndras Olah 				(TF_RCVD_SCALE|TF_REQ_SCALE)) {
1383845799c1SAndras Olah 				tp->snd_scale = tp->requested_s_scale;
1384845799c1SAndras Olah 				tp->rcv_scale = tp->request_r_scale;
1385845799c1SAndras Olah 			}
1386a0292f23SGarrett Wollman 			tp->rcv_adv += tp->rcv_wnd;
1387a0292f23SGarrett Wollman 			tp->snd_una++;		/* SYN is acked */
1388a0292f23SGarrett Wollman 			/*
1389a0292f23SGarrett Wollman 			 * If there's data, delay ACK; if there's also a FIN
1390a0292f23SGarrett Wollman 			 * ACKNOW will be turned on later.
1391a0292f23SGarrett Wollman 			 */
1392d8c85a26SJonathan Lemon 			if (DELAY_ACK(tp) && tlen != 0)
13939b8b58e0SJonathan Lemon 				callout_reset(tp->tt_delack, tcp_delacktime,
13949b8b58e0SJonathan Lemon 				    tcp_timer_delack, tp);
1395a0292f23SGarrett Wollman 			else
1396a0292f23SGarrett Wollman 				tp->t_flags |= TF_ACKNOW;
1397a0292f23SGarrett Wollman 			/*
1398a0292f23SGarrett Wollman 			 * Received <SYN,ACK> in SYN_SENT[*] state.
1399a0292f23SGarrett Wollman 			 * Transitions:
1400a0292f23SGarrett Wollman 			 *	SYN_SENT  --> ESTABLISHED
1401a0292f23SGarrett Wollman 			 *	SYN_SENT* --> FIN_WAIT_1
1402a0292f23SGarrett Wollman 			 */
14039b8b58e0SJonathan Lemon 			tp->t_starttime = ticks;
1404a0292f23SGarrett Wollman 			if (tp->t_flags & TF_NEEDFIN) {
1405a0292f23SGarrett Wollman 				tp->t_state = TCPS_FIN_WAIT_1;
1406a0292f23SGarrett Wollman 				tp->t_flags &= ~TF_NEEDFIN;
1407fb59c426SYoshinobu Inoue 				thflags &= ~TH_SYN;
14087ff19458SPaul Traina 			} else {
1409a0292f23SGarrett Wollman 				tp->t_state = TCPS_ESTABLISHED;
14109b8b58e0SJonathan Lemon 				callout_reset(tp->tt_keep, tcp_keepidle,
14119b8b58e0SJonathan Lemon 					      tcp_timer_keep, tp);
14127ff19458SPaul Traina 			}
1413a0292f23SGarrett Wollman 		} else {
1414a0292f23SGarrett Wollman 			/*
1415c068736aSJeffrey Hsu 			 * Received initial SYN in SYN-SENT[*] state =>
1416c068736aSJeffrey Hsu 			 * simultaneous open.  If segment contains CC option
1417c068736aSJeffrey Hsu 			 * and there is a cached CC, apply TAO test.
1418c068736aSJeffrey Hsu 			 * If it succeeds, connection is * half-synchronized.
1419c068736aSJeffrey Hsu 			 * Otherwise, do 3-way handshake:
1420a0292f23SGarrett Wollman 			 *        SYN-SENT -> SYN-RECEIVED
1421a0292f23SGarrett Wollman 			 *        SYN-SENT* -> SYN-RECEIVED*
1422a0292f23SGarrett Wollman 			 * If there was no CC option, clear cached CC value.
1423a0292f23SGarrett Wollman 			 */
1424a0292f23SGarrett Wollman 			tp->t_flags |= TF_ACKNOW;
14259b8b58e0SJonathan Lemon 			callout_stop(tp->tt_rexmt);
1426df8bae1dSRodney W. Grimes 			tp->t_state = TCPS_SYN_RECEIVED;
1427a0292f23SGarrett Wollman 		}
1428df8bae1dSRodney W. Grimes 
1429df8bae1dSRodney W. Grimes trimthenstep6:
1430de30ea13SRobert Watson 		KASSERT(headlocked, ("tcp_input: trimthenstep6: head not "
1431de30ea13SRobert Watson 		    "locked"));
14327cfc6904SRobert Watson 		INP_LOCK_ASSERT(inp);
14337cfc6904SRobert Watson 
1434df8bae1dSRodney W. Grimes 		/*
1435fb59c426SYoshinobu Inoue 		 * Advance th->th_seq to correspond to first data byte.
1436df8bae1dSRodney W. Grimes 		 * If data, trim to stay within window,
1437df8bae1dSRodney W. Grimes 		 * dropping FIN if necessary.
1438df8bae1dSRodney W. Grimes 		 */
1439fb59c426SYoshinobu Inoue 		th->th_seq++;
1440fb59c426SYoshinobu Inoue 		if (tlen > tp->rcv_wnd) {
1441fb59c426SYoshinobu Inoue 			todrop = tlen - tp->rcv_wnd;
1442df8bae1dSRodney W. Grimes 			m_adj(m, -todrop);
1443fb59c426SYoshinobu Inoue 			tlen = tp->rcv_wnd;
1444fb59c426SYoshinobu Inoue 			thflags &= ~TH_FIN;
1445df8bae1dSRodney W. Grimes 			tcpstat.tcps_rcvpackafterwin++;
1446df8bae1dSRodney W. Grimes 			tcpstat.tcps_rcvbyteafterwin += todrop;
1447df8bae1dSRodney W. Grimes 		}
1448fb59c426SYoshinobu Inoue 		tp->snd_wl1 = th->th_seq - 1;
1449fb59c426SYoshinobu Inoue 		tp->rcv_up = th->th_seq;
1450a0292f23SGarrett Wollman 		/*
1451a0292f23SGarrett Wollman 		 * Client side of transaction: already sent SYN and data.
1452a0292f23SGarrett Wollman 		 * If the remote host used T/TCP to validate the SYN,
1453a0292f23SGarrett Wollman 		 * our data will be ACK'd; if so, enter normal data segment
1454a0292f23SGarrett Wollman 		 * processing in the middle of step 5, ack processing.
1455a0292f23SGarrett Wollman 		 * Otherwise, goto step 6.
1456a0292f23SGarrett Wollman 		 */
1457fb59c426SYoshinobu Inoue 		if (thflags & TH_ACK)
1458a0292f23SGarrett Wollman 			goto process_ACK;
1459c068736aSJeffrey Hsu 
1460df8bae1dSRodney W. Grimes 		goto step6;
1461c068736aSJeffrey Hsu 
1462a0292f23SGarrett Wollman 	/*
1463a0292f23SGarrett Wollman 	 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
1464c94c54e4SAndre Oppermann 	 *      do normal processing.
1465a0292f23SGarrett Wollman 	 *
1466c94c54e4SAndre Oppermann 	 * NB: Leftover from RFC1644 T/TCP.  Cases to be reused later.
1467a0292f23SGarrett Wollman 	 */
1468a0292f23SGarrett Wollman 	case TCPS_LAST_ACK:
1469a0292f23SGarrett Wollman 	case TCPS_CLOSING:
1470a0292f23SGarrett Wollman 	case TCPS_TIME_WAIT:
1471340c35deSJonathan Lemon 		KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
1472a0292f23SGarrett Wollman 		break;  /* continue normal processing */
1473df8bae1dSRodney W. Grimes 	}
1474df8bae1dSRodney W. Grimes 
1475df8bae1dSRodney W. Grimes 	/*
1476df8bae1dSRodney W. Grimes 	 * States other than LISTEN or SYN_SENT.
147780ab7c0eSGarrett Wollman 	 * First check the RST flag and sequence number since reset segments
147880ab7c0eSGarrett Wollman 	 * are exempt from the timestamp and connection count tests.  This
147980ab7c0eSGarrett Wollman 	 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
148080ab7c0eSGarrett Wollman 	 * below which allowed reset segments in half the sequence space
148180ab7c0eSGarrett Wollman 	 * to fall though and be processed (which gives forged reset
148280ab7c0eSGarrett Wollman 	 * segments with a random sequence number a 50 percent chance of
148380ab7c0eSGarrett Wollman 	 * killing a connection).
148480ab7c0eSGarrett Wollman 	 * Then check timestamp, if present.
1485a0292f23SGarrett Wollman 	 * Then check the connection count, if present.
1486df8bae1dSRodney W. Grimes 	 * Then check that at least some bytes of segment are within
1487df8bae1dSRodney W. Grimes 	 * receive window.  If segment begins before rcv_nxt,
1488df8bae1dSRodney W. Grimes 	 * drop leading data (and SYN); if nothing left, just ack.
1489df8bae1dSRodney W. Grimes 	 *
149080ab7c0eSGarrett Wollman 	 *
149180ab7c0eSGarrett Wollman 	 * If the RST bit is set, check the sequence number to see
149280ab7c0eSGarrett Wollman 	 * if this is a valid reset segment.
149380ab7c0eSGarrett Wollman 	 * RFC 793 page 37:
149480ab7c0eSGarrett Wollman 	 *   In all states except SYN-SENT, all reset (RST) segments
149580ab7c0eSGarrett Wollman 	 *   are validated by checking their SEQ-fields.  A reset is
149680ab7c0eSGarrett Wollman 	 *   valid if its sequence number is in the window.
149780ab7c0eSGarrett Wollman 	 * Note: this does not take into account delayed ACKs, so
149880ab7c0eSGarrett Wollman 	 *   we should test against last_ack_sent instead of rcv_nxt.
14991a244a61SJonathan Lemon 	 *   The sequence number in the reset segment is normally an
15001a244a61SJonathan Lemon 	 *   echo of our outgoing acknowlegement numbers, but some hosts
15011a244a61SJonathan Lemon 	 *   send a reset with the sequence number at the rightmost edge
15021a244a61SJonathan Lemon 	 *   of our receive window, and we have to handle this case.
150380dd2a81SMike Silbersack 	 * Note 2: Paul Watson's paper "Slipping in the Window" has shown
150480dd2a81SMike Silbersack 	 *   that brute force RST attacks are possible.  To combat this,
150580dd2a81SMike Silbersack 	 *   we use a much stricter check while in the ESTABLISHED state,
150680dd2a81SMike Silbersack 	 *   only accepting RSTs where the sequence number is equal to
150780dd2a81SMike Silbersack 	 *   last_ack_sent.  In all other states (the states in which a
150880dd2a81SMike Silbersack 	 *   RST is more likely), the more permissive check is used.
150980ab7c0eSGarrett Wollman 	 * If we have multiple segments in flight, the intial reset
151080ab7c0eSGarrett Wollman 	 * segment sequence numbers will be to the left of last_ack_sent,
151180ab7c0eSGarrett Wollman 	 * but they will eventually catch up.
151280ab7c0eSGarrett Wollman 	 * In any case, it never made sense to trim reset segments to
151380ab7c0eSGarrett Wollman 	 * fit the receive window since RFC 1122 says:
151480ab7c0eSGarrett Wollman 	 *   4.2.2.12  RST Segment: RFC-793 Section 3.4
151580ab7c0eSGarrett Wollman 	 *
151680ab7c0eSGarrett Wollman 	 *    A TCP SHOULD allow a received RST segment to include data.
151780ab7c0eSGarrett Wollman 	 *
151880ab7c0eSGarrett Wollman 	 *    DISCUSSION
151980ab7c0eSGarrett Wollman 	 *         It has been suggested that a RST segment could contain
152080ab7c0eSGarrett Wollman 	 *         ASCII text that encoded and explained the cause of the
152180ab7c0eSGarrett Wollman 	 *         RST.  No standard has yet been established for such
152280ab7c0eSGarrett Wollman 	 *         data.
152380ab7c0eSGarrett Wollman 	 *
152480ab7c0eSGarrett Wollman 	 * If the reset segment passes the sequence number test examine
152580ab7c0eSGarrett Wollman 	 * the state:
152680ab7c0eSGarrett Wollman 	 *    SYN_RECEIVED STATE:
152780ab7c0eSGarrett Wollman 	 *	If passive open, return to LISTEN state.
152880ab7c0eSGarrett Wollman 	 *	If active open, inform user that connection was refused.
1529745bab7fSDima Dorfman 	 *    ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES:
153080ab7c0eSGarrett Wollman 	 *	Inform user that connection was reset, and close tcb.
1531e9bd3a37SJonathan M. Bresler 	 *    CLOSING, LAST_ACK STATES:
153280ab7c0eSGarrett Wollman 	 *	Close the tcb.
1533e9bd3a37SJonathan M. Bresler 	 *    TIME_WAIT STATE:
153480ab7c0eSGarrett Wollman 	 *	Drop the segment - see Stevens, vol. 2, p. 964 and
153580ab7c0eSGarrett Wollman 	 *      RFC 1337.
153680ab7c0eSGarrett Wollman 	 */
1537fb59c426SYoshinobu Inoue 	if (thflags & TH_RST) {
15386a220ed8SMike Silbersack 		if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
15396a220ed8SMike Silbersack 		    SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) ||
15406a220ed8SMike Silbersack 		    (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) {
154180ab7c0eSGarrett Wollman 			switch (tp->t_state) {
154280ab7c0eSGarrett Wollman 
154380ab7c0eSGarrett Wollman 			case TCPS_SYN_RECEIVED:
154480ab7c0eSGarrett Wollman 				so->so_error = ECONNREFUSED;
154580ab7c0eSGarrett Wollman 				goto close;
154680ab7c0eSGarrett Wollman 
154780ab7c0eSGarrett Wollman 			case TCPS_ESTABLISHED:
1548a69968eeSMike Silbersack 				if (tp->last_ack_sent != th->th_seq &&
1549a69968eeSMike Silbersack 			 	    tcp_insecure_rst == 0) {
155080dd2a81SMike Silbersack 					tcpstat.tcps_badrst++;
155180dd2a81SMike Silbersack 					goto drop;
155280dd2a81SMike Silbersack 				}
155380ab7c0eSGarrett Wollman 			case TCPS_FIN_WAIT_1:
155480ab7c0eSGarrett Wollman 			case TCPS_FIN_WAIT_2:
155580ab7c0eSGarrett Wollman 			case TCPS_CLOSE_WAIT:
155680ab7c0eSGarrett Wollman 				so->so_error = ECONNRESET;
155780ab7c0eSGarrett Wollman 			close:
155880ab7c0eSGarrett Wollman 				tp->t_state = TCPS_CLOSED;
155980ab7c0eSGarrett Wollman 				tcpstat.tcps_drops++;
1560416738a7SRobert Watson 				KASSERT(headlocked, ("tcp_input: "
1561416738a7SRobert Watson 				    "trimthenstep6: tcp_close: head not "
1562416738a7SRobert Watson 				    "locked"));
156380ab7c0eSGarrett Wollman 				tp = tcp_close(tp);
156480ab7c0eSGarrett Wollman 				break;
156580ab7c0eSGarrett Wollman 
156680ab7c0eSGarrett Wollman 			case TCPS_CLOSING:
156780ab7c0eSGarrett Wollman 			case TCPS_LAST_ACK:
1568416738a7SRobert Watson 				KASSERT(headlocked, ("trimthenstep6: "
1569416738a7SRobert Watson 				    "tcp_close.2: head not locked"));
157080ab7c0eSGarrett Wollman 				tp = tcp_close(tp);
157180ab7c0eSGarrett Wollman 				break;
157280ab7c0eSGarrett Wollman 
157380ab7c0eSGarrett Wollman 			case TCPS_TIME_WAIT:
1574340c35deSJonathan Lemon 				KASSERT(tp->t_state != TCPS_TIME_WAIT,
1575340c35deSJonathan Lemon 				    ("timewait"));
157680ab7c0eSGarrett Wollman 				break;
157780ab7c0eSGarrett Wollman 			}
157880ab7c0eSGarrett Wollman 		}
157980ab7c0eSGarrett Wollman 		goto drop;
158080ab7c0eSGarrett Wollman 	}
158180ab7c0eSGarrett Wollman 
158280ab7c0eSGarrett Wollman 	/*
1583df8bae1dSRodney W. Grimes 	 * RFC 1323 PAWS: If we have a timestamp reply on this segment
1584df8bae1dSRodney W. Grimes 	 * and it's less than ts_recent, drop it.
1585df8bae1dSRodney W. Grimes 	 */
1586be2ac88cSJonathan Lemon 	if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
158780ab7c0eSGarrett Wollman 	    TSTMP_LT(to.to_tsval, tp->ts_recent)) {
1588df8bae1dSRodney W. Grimes 
1589df8bae1dSRodney W. Grimes 		/* Check to see if ts_recent is over 24 days old.  */
15909b8b58e0SJonathan Lemon 		if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) {
1591df8bae1dSRodney W. Grimes 			/*
1592df8bae1dSRodney W. Grimes 			 * Invalidate ts_recent.  If this segment updates
1593df8bae1dSRodney W. Grimes 			 * ts_recent, the age will be reset later and ts_recent
1594df8bae1dSRodney W. Grimes 			 * will get a valid value.  If it does not, setting
1595df8bae1dSRodney W. Grimes 			 * ts_recent to zero will at least satisfy the
1596df8bae1dSRodney W. Grimes 			 * requirement that zero be placed in the timestamp
1597df8bae1dSRodney W. Grimes 			 * echo reply when ts_recent isn't valid.  The
1598df8bae1dSRodney W. Grimes 			 * age isn't reset until we get a valid ts_recent
1599df8bae1dSRodney W. Grimes 			 * because we don't want out-of-order segments to be
1600df8bae1dSRodney W. Grimes 			 * dropped when ts_recent is old.
1601df8bae1dSRodney W. Grimes 			 */
1602df8bae1dSRodney W. Grimes 			tp->ts_recent = 0;
1603df8bae1dSRodney W. Grimes 		} else {
1604df8bae1dSRodney W. Grimes 			tcpstat.tcps_rcvduppack++;
1605fb59c426SYoshinobu Inoue 			tcpstat.tcps_rcvdupbyte += tlen;
1606df8bae1dSRodney W. Grimes 			tcpstat.tcps_pawsdrop++;
160707fd333dSMatthew Dillon 			if (tlen)
1608df8bae1dSRodney W. Grimes 				goto dropafterack;
16091ab4789dSMatthew Dillon 			goto drop;
16101ab4789dSMatthew Dillon 		}
1611df8bae1dSRodney W. Grimes 	}
1612df8bae1dSRodney W. Grimes 
1613a0292f23SGarrett Wollman 	/*
161480ab7c0eSGarrett Wollman 	 * In the SYN-RECEIVED state, validate that the packet belongs to
161580ab7c0eSGarrett Wollman 	 * this connection before trimming the data to fit the receive
161680ab7c0eSGarrett Wollman 	 * window.  Check the sequence number versus IRS since we know
161780ab7c0eSGarrett Wollman 	 * the sequence numbers haven't wrapped.  This is a partial fix
161880ab7c0eSGarrett Wollman 	 * for the "LAND" DoS attack.
161980ab7c0eSGarrett Wollman 	 */
1620a57815efSBosko Milekic 	if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
1621a57815efSBosko Milekic 		rstreason = BANDLIM_RST_OPENPORT;
1622a57815efSBosko Milekic 		goto dropwithreset;
1623a57815efSBosko Milekic 	}
162480ab7c0eSGarrett Wollman 
1625fb59c426SYoshinobu Inoue 	todrop = tp->rcv_nxt - th->th_seq;
1626df8bae1dSRodney W. Grimes 	if (todrop > 0) {
1627fb59c426SYoshinobu Inoue 		if (thflags & TH_SYN) {
1628fb59c426SYoshinobu Inoue 			thflags &= ~TH_SYN;
1629fb59c426SYoshinobu Inoue 			th->th_seq++;
1630fb59c426SYoshinobu Inoue 			if (th->th_urp > 1)
1631fb59c426SYoshinobu Inoue 				th->th_urp--;
1632df8bae1dSRodney W. Grimes 			else
1633fb59c426SYoshinobu Inoue 				thflags &= ~TH_URG;
1634df8bae1dSRodney W. Grimes 			todrop--;
1635df8bae1dSRodney W. Grimes 		}
1636df8bae1dSRodney W. Grimes 		/*
1637dac20301SGarrett Wollman 		 * Following if statement from Stevens, vol. 2, p. 960.
1638df8bae1dSRodney W. Grimes 		 */
1639fb59c426SYoshinobu Inoue 		if (todrop > tlen
1640fb59c426SYoshinobu Inoue 		    || (todrop == tlen && (thflags & TH_FIN) == 0)) {
1641dac20301SGarrett Wollman 			/*
1642dac20301SGarrett Wollman 			 * Any valid FIN must be to the left of the window.
1643dac20301SGarrett Wollman 			 * At this point the FIN must be a duplicate or out
1644dac20301SGarrett Wollman 			 * of sequence; drop it.
1645dac20301SGarrett Wollman 			 */
1646fb59c426SYoshinobu Inoue 			thflags &= ~TH_FIN;
1647dac20301SGarrett Wollman 
1648df8bae1dSRodney W. Grimes 			/*
1649dac20301SGarrett Wollman 			 * Send an ACK to resynchronize and drop any data.
1650dac20301SGarrett Wollman 			 * But keep on processing for RST or ACK.
1651df8bae1dSRodney W. Grimes 			 */
1652dac20301SGarrett Wollman 			tp->t_flags |= TF_ACKNOW;
1653fb59c426SYoshinobu Inoue 			todrop = tlen;
1654dac20301SGarrett Wollman 			tcpstat.tcps_rcvduppack++;
1655dac20301SGarrett Wollman 			tcpstat.tcps_rcvdupbyte += todrop;
1656df8bae1dSRodney W. Grimes 		} else {
1657df8bae1dSRodney W. Grimes 			tcpstat.tcps_rcvpartduppack++;
1658df8bae1dSRodney W. Grimes 			tcpstat.tcps_rcvpartdupbyte += todrop;
1659df8bae1dSRodney W. Grimes 		}
1660fb59c426SYoshinobu Inoue 		drop_hdrlen += todrop;	/* drop from the top afterwards */
1661fb59c426SYoshinobu Inoue 		th->th_seq += todrop;
1662fb59c426SYoshinobu Inoue 		tlen -= todrop;
1663fb59c426SYoshinobu Inoue 		if (th->th_urp > todrop)
1664fb59c426SYoshinobu Inoue 			th->th_urp -= todrop;
1665df8bae1dSRodney W. Grimes 		else {
1666fb59c426SYoshinobu Inoue 			thflags &= ~TH_URG;
1667fb59c426SYoshinobu Inoue 			th->th_urp = 0;
1668df8bae1dSRodney W. Grimes 		}
1669df8bae1dSRodney W. Grimes 	}
1670df8bae1dSRodney W. Grimes 
1671df8bae1dSRodney W. Grimes 	/*
1672df8bae1dSRodney W. Grimes 	 * If new data are received on a connection after the
1673df8bae1dSRodney W. Grimes 	 * user processes are gone, then RST the other end.
1674df8bae1dSRodney W. Grimes 	 */
1675df8bae1dSRodney W. Grimes 	if ((so->so_state & SS_NOFDREF) &&
1676fb59c426SYoshinobu Inoue 	    tp->t_state > TCPS_CLOSE_WAIT && tlen) {
1677416738a7SRobert Watson 		KASSERT(headlocked, ("trimthenstep6: tcp_close.3: head not "
1678416738a7SRobert Watson 		    "locked"));
1679df8bae1dSRodney W. Grimes 		tp = tcp_close(tp);
1680df8bae1dSRodney W. Grimes 		tcpstat.tcps_rcvafterclose++;
1681a57815efSBosko Milekic 		rstreason = BANDLIM_UNLIMITED;
1682df8bae1dSRodney W. Grimes 		goto dropwithreset;
1683df8bae1dSRodney W. Grimes 	}
1684df8bae1dSRodney W. Grimes 
1685df8bae1dSRodney W. Grimes 	/*
1686df8bae1dSRodney W. Grimes 	 * If segment ends after window, drop trailing data
1687df8bae1dSRodney W. Grimes 	 * (and PUSH and FIN); if nothing left, just ACK.
1688df8bae1dSRodney W. Grimes 	 */
1689fb59c426SYoshinobu Inoue 	todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd);
1690df8bae1dSRodney W. Grimes 	if (todrop > 0) {
1691df8bae1dSRodney W. Grimes 		tcpstat.tcps_rcvpackafterwin++;
1692fb59c426SYoshinobu Inoue 		if (todrop >= tlen) {
1693fb59c426SYoshinobu Inoue 			tcpstat.tcps_rcvbyteafterwin += tlen;
1694df8bae1dSRodney W. Grimes 			/*
1695df8bae1dSRodney W. Grimes 			 * If a new connection request is received
1696df8bae1dSRodney W. Grimes 			 * while in TIME_WAIT, drop the old connection
1697df8bae1dSRodney W. Grimes 			 * and start over if the sequence numbers
1698df8bae1dSRodney W. Grimes 			 * are above the previous ones.
1699df8bae1dSRodney W. Grimes 			 */
1700340c35deSJonathan Lemon 			KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
1701fb59c426SYoshinobu Inoue 			if (thflags & TH_SYN &&
1702df8bae1dSRodney W. Grimes 			    tp->t_state == TCPS_TIME_WAIT &&
1703fb59c426SYoshinobu Inoue 			    SEQ_GT(th->th_seq, tp->rcv_nxt)) {
1704416738a7SRobert Watson 				KASSERT(headlocked, ("trimthenstep6: "
1705416738a7SRobert Watson 				    "tcp_close.4: head not locked"));
1706df8bae1dSRodney W. Grimes 				tp = tcp_close(tp);
1707df8bae1dSRodney W. Grimes 				goto findpcb;
1708df8bae1dSRodney W. Grimes 			}
1709df8bae1dSRodney W. Grimes 			/*
1710df8bae1dSRodney W. Grimes 			 * If window is closed can only take segments at
1711df8bae1dSRodney W. Grimes 			 * window edge, and have to drop data and PUSH from
1712df8bae1dSRodney W. Grimes 			 * incoming segments.  Continue processing, but
1713df8bae1dSRodney W. Grimes 			 * remember to ack.  Otherwise, drop segment
1714df8bae1dSRodney W. Grimes 			 * and ack.
1715df8bae1dSRodney W. Grimes 			 */
1716fb59c426SYoshinobu Inoue 			if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
1717df8bae1dSRodney W. Grimes 				tp->t_flags |= TF_ACKNOW;
1718df8bae1dSRodney W. Grimes 				tcpstat.tcps_rcvwinprobe++;
1719df8bae1dSRodney W. Grimes 			} else
1720df8bae1dSRodney W. Grimes 				goto dropafterack;
1721df8bae1dSRodney W. Grimes 		} else
1722df8bae1dSRodney W. Grimes 			tcpstat.tcps_rcvbyteafterwin += todrop;
1723df8bae1dSRodney W. Grimes 		m_adj(m, -todrop);
1724fb59c426SYoshinobu Inoue 		tlen -= todrop;
1725fb59c426SYoshinobu Inoue 		thflags &= ~(TH_PUSH|TH_FIN);
1726df8bae1dSRodney W. Grimes 	}
1727df8bae1dSRodney W. Grimes 
1728df8bae1dSRodney W. Grimes 	/*
1729df8bae1dSRodney W. Grimes 	 * If last ACK falls within this segment's sequence numbers,
1730df8bae1dSRodney W. Grimes 	 * record its timestamp.
1731cf09195bSPaul Saab 	 * NOTE:
1732cf09195bSPaul Saab 	 * 1) That the test incorporates suggestions from the latest
1733a0292f23SGarrett Wollman 	 *    proposal of the tcplw@cray.com list (Braden 1993/04/26).
1734cf09195bSPaul Saab 	 * 2) That updating only on newer timestamps interferes with
1735cf09195bSPaul Saab 	 *    our earlier PAWS tests, so this check should be solely
1736cf09195bSPaul Saab 	 *    predicated on the sequence space of this segment.
1737cf09195bSPaul Saab 	 * 3) That we modify the segment boundary check to be
1738cf09195bSPaul Saab 	 *        Last.ACK.Sent <= SEG.SEQ + SEG.Len
1739cf09195bSPaul Saab 	 *    instead of RFC1323's
1740cf09195bSPaul Saab 	 *        Last.ACK.Sent < SEG.SEQ + SEG.Len,
1741cf09195bSPaul Saab 	 *    This modified check allows us to overcome RFC1323's
1742cf09195bSPaul Saab 	 *    limitations as described in Stevens TCP/IP Illustrated
1743cf09195bSPaul Saab 	 *    Vol. 2 p.869. In such cases, we can still calculate the
1744cf09195bSPaul Saab 	 *    RTT correctly when RCV.NXT == Last.ACK.Sent.
1745df8bae1dSRodney W. Grimes 	 */
1746be2ac88cSJonathan Lemon 	if ((to.to_flags & TOF_TS) != 0 &&
1747cf09195bSPaul Saab 	    SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
1748cf09195bSPaul Saab 	    SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen +
1749cf09195bSPaul Saab 		((thflags & (TH_SYN|TH_FIN)) != 0))) {
17509b8b58e0SJonathan Lemon 		tp->ts_recent_age = ticks;
1751a0292f23SGarrett Wollman 		tp->ts_recent = to.to_tsval;
1752df8bae1dSRodney W. Grimes 	}
1753df8bae1dSRodney W. Grimes 
1754df8bae1dSRodney W. Grimes 	/*
1755df8bae1dSRodney W. Grimes 	 * If a SYN is in the window, then this is an
1756df8bae1dSRodney W. Grimes 	 * error and we send an RST and drop the connection.
1757df8bae1dSRodney W. Grimes 	 */
1758fb59c426SYoshinobu Inoue 	if (thflags & TH_SYN) {
17591e2d989dSRobert Watson 		KASSERT(headlocked, ("tcp_input: tcp_drop: trimthenstep6: "
17601e2d989dSRobert Watson 		    "head not locked"));
1761df8bae1dSRodney W. Grimes 		tp = tcp_drop(tp, ECONNRESET);
1762a57815efSBosko Milekic 		rstreason = BANDLIM_UNLIMITED;
1763122aad88SAndre Oppermann 		goto drop;
1764df8bae1dSRodney W. Grimes 	}
1765df8bae1dSRodney W. Grimes 
1766a0292f23SGarrett Wollman 	/*
1767a0292f23SGarrett Wollman 	 * If the ACK bit is off:  if in SYN-RECEIVED state or SENDSYN
1768a0292f23SGarrett Wollman 	 * flag is on (half-synchronized state), then queue data for
1769a0292f23SGarrett Wollman 	 * later processing; else drop segment and return.
1770a0292f23SGarrett Wollman 	 */
1771fb59c426SYoshinobu Inoue 	if ((thflags & TH_ACK) == 0) {
1772a0292f23SGarrett Wollman 		if (tp->t_state == TCPS_SYN_RECEIVED ||
1773a0292f23SGarrett Wollman 		    (tp->t_flags & TF_NEEDSYN))
1774a0292f23SGarrett Wollman 			goto step6;
1775a0292f23SGarrett Wollman 		else
1776a0292f23SGarrett Wollman 			goto drop;
1777a0292f23SGarrett Wollman 	}
1778df8bae1dSRodney W. Grimes 
1779df8bae1dSRodney W. Grimes 	/*
1780df8bae1dSRodney W. Grimes 	 * Ack processing.
1781df8bae1dSRodney W. Grimes 	 */
1782df8bae1dSRodney W. Grimes 	switch (tp->t_state) {
1783df8bae1dSRodney W. Grimes 
1784df8bae1dSRodney W. Grimes 	/*
1785764d8cefSBill Fenner 	 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter
1786764d8cefSBill Fenner 	 * ESTABLISHED state and continue processing.
1787764d8cefSBill Fenner 	 * The ACK was checked above.
1788df8bae1dSRodney W. Grimes 	 */
1789df8bae1dSRodney W. Grimes 	case TCPS_SYN_RECEIVED:
1790a0292f23SGarrett Wollman 
1791df8bae1dSRodney W. Grimes 		tcpstat.tcps_connects++;
1792df8bae1dSRodney W. Grimes 		soisconnected(so);
1793df8bae1dSRodney W. Grimes 		/* Do window scaling? */
1794df8bae1dSRodney W. Grimes 		if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1795df8bae1dSRodney W. Grimes 			(TF_RCVD_SCALE|TF_REQ_SCALE)) {
1796df8bae1dSRodney W. Grimes 			tp->snd_scale = tp->requested_s_scale;
1797df8bae1dSRodney W. Grimes 			tp->rcv_scale = tp->request_r_scale;
1798df8bae1dSRodney W. Grimes 		}
1799a0292f23SGarrett Wollman 		/*
1800a0292f23SGarrett Wollman 		 * Make transitions:
1801a0292f23SGarrett Wollman 		 *      SYN-RECEIVED  -> ESTABLISHED
1802a0292f23SGarrett Wollman 		 *      SYN-RECEIVED* -> FIN-WAIT-1
1803a0292f23SGarrett Wollman 		 */
18049b8b58e0SJonathan Lemon 		tp->t_starttime = ticks;
1805a0292f23SGarrett Wollman 		if (tp->t_flags & TF_NEEDFIN) {
1806a0292f23SGarrett Wollman 			tp->t_state = TCPS_FIN_WAIT_1;
1807a0292f23SGarrett Wollman 			tp->t_flags &= ~TF_NEEDFIN;
18087ff19458SPaul Traina 		} else {
1809a0292f23SGarrett Wollman 			tp->t_state = TCPS_ESTABLISHED;
18109b8b58e0SJonathan Lemon 			callout_reset(tp->tt_keep, tcp_keepidle,
18119b8b58e0SJonathan Lemon 				      tcp_timer_keep, tp);
18127ff19458SPaul Traina 		}
1813a0292f23SGarrett Wollman 		/*
1814a0292f23SGarrett Wollman 		 * If segment contains data or ACK, will call tcp_reass()
1815a0292f23SGarrett Wollman 		 * later; if not, do so now to pass queued data to user.
1816a0292f23SGarrett Wollman 		 */
1817fb59c426SYoshinobu Inoue 		if (tlen == 0 && (thflags & TH_FIN) == 0)
1818fb59c426SYoshinobu Inoue 			(void) tcp_reass(tp, (struct tcphdr *)0, 0,
1819a0292f23SGarrett Wollman 			    (struct mbuf *)0);
1820fb59c426SYoshinobu Inoue 		tp->snd_wl1 = th->th_seq - 1;
182193b0017fSPhilippe Charnier 		/* FALLTHROUGH */
1822df8bae1dSRodney W. Grimes 
1823df8bae1dSRodney W. Grimes 	/*
1824df8bae1dSRodney W. Grimes 	 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
1825df8bae1dSRodney W. Grimes 	 * ACKs.  If the ack is in the range
1826fb59c426SYoshinobu Inoue 	 *	tp->snd_una < th->th_ack <= tp->snd_max
1827fb59c426SYoshinobu Inoue 	 * then advance tp->snd_una to th->th_ack and drop
1828df8bae1dSRodney W. Grimes 	 * data from the retransmission queue.  If this ACK reflects
1829df8bae1dSRodney W. Grimes 	 * more up to date window information we update our window information.
1830df8bae1dSRodney W. Grimes 	 */
1831df8bae1dSRodney W. Grimes 	case TCPS_ESTABLISHED:
1832df8bae1dSRodney W. Grimes 	case TCPS_FIN_WAIT_1:
1833df8bae1dSRodney W. Grimes 	case TCPS_FIN_WAIT_2:
1834df8bae1dSRodney W. Grimes 	case TCPS_CLOSE_WAIT:
1835df8bae1dSRodney W. Grimes 	case TCPS_CLOSING:
1836df8bae1dSRodney W. Grimes 	case TCPS_LAST_ACK:
1837df8bae1dSRodney W. Grimes 	case TCPS_TIME_WAIT:
1838340c35deSJonathan Lemon 		KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
18395a53ca16SPaul Saab 		if (SEQ_GT(th->th_ack, tp->snd_max)) {
18405a53ca16SPaul Saab 			tcpstat.tcps_rcvacktoomuch++;
18415a53ca16SPaul Saab 			goto dropafterack;
18425a53ca16SPaul Saab 		}
1843482ac968SPaul Saab 		if (tp->sack_enable &&
1844482ac968SPaul Saab 		    (to.to_nsacks > 0 || !TAILQ_EMPTY(&tp->snd_holes)))
18455a53ca16SPaul Saab 			tcp_sack_doack(tp, &to, th->th_ack);
1846fb59c426SYoshinobu Inoue 		if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
1847fb59c426SYoshinobu Inoue 			if (tlen == 0 && tiwin == tp->snd_wnd) {
1848df8bae1dSRodney W. Grimes 				tcpstat.tcps_rcvdupack++;
1849df8bae1dSRodney W. Grimes 				/*
1850df8bae1dSRodney W. Grimes 				 * If we have outstanding data (other than
1851df8bae1dSRodney W. Grimes 				 * a window probe), this is a completely
1852df8bae1dSRodney W. Grimes 				 * duplicate ack (ie, window info didn't
1853df8bae1dSRodney W. Grimes 				 * change), the ack is the biggest we've
1854df8bae1dSRodney W. Grimes 				 * seen and we've seen exactly our rexmt
1855df8bae1dSRodney W. Grimes 				 * threshhold of them, assume a packet
1856df8bae1dSRodney W. Grimes 				 * has been dropped and retransmit it.
1857df8bae1dSRodney W. Grimes 				 * Kludge snd_nxt & the congestion
1858df8bae1dSRodney W. Grimes 				 * window so we send only this one
1859df8bae1dSRodney W. Grimes 				 * packet.
1860df8bae1dSRodney W. Grimes 				 *
1861df8bae1dSRodney W. Grimes 				 * We know we're losing at the current
1862df8bae1dSRodney W. Grimes 				 * window size so do congestion avoidance
1863df8bae1dSRodney W. Grimes 				 * (set ssthresh to half the current window
1864df8bae1dSRodney W. Grimes 				 * and pull our congestion window back to
1865df8bae1dSRodney W. Grimes 				 * the new ssthresh).
1866df8bae1dSRodney W. Grimes 				 *
1867df8bae1dSRodney W. Grimes 				 * Dup acks mean that packets have left the
1868df8bae1dSRodney W. Grimes 				 * network (they're now cached at the receiver)
1869df8bae1dSRodney W. Grimes 				 * so bump cwnd by the amount in the receiver
1870df8bae1dSRodney W. Grimes 				 * to keep a constant cwnd packets in the
1871df8bae1dSRodney W. Grimes 				 * network.
1872df8bae1dSRodney W. Grimes 				 */
18739b8b58e0SJonathan Lemon 				if (!callout_active(tp->tt_rexmt) ||
1874fb59c426SYoshinobu Inoue 				    th->th_ack != tp->snd_una)
1875df8bae1dSRodney W. Grimes 					tp->t_dupacks = 0;
1876cb942153SJeffrey Hsu 				else if (++tp->t_dupacks > tcprexmtthresh ||
18776d90faf3SPaul Saab 					 ((tcp_do_newreno || tp->sack_enable) &&
18789d11646dSJeffrey Hsu 					  IN_FASTRECOVERY(tp))) {
187925e6f9edSPaul Saab                                         if (tp->sack_enable && IN_FASTRECOVERY(tp)) {
1880808f11b7SPaul Saab 						int awnd;
188125e6f9edSPaul Saab 
188225e6f9edSPaul Saab 						/*
188325e6f9edSPaul Saab 						 * Compute the amount of data in flight first.
188425e6f9edSPaul Saab 						 * We can inject new data into the pipe iff
188525e6f9edSPaul Saab 						 * we have less than 1/2 the original window's
188625e6f9edSPaul Saab 						 * worth of data in flight.
188725e6f9edSPaul Saab 						 */
1888808f11b7SPaul Saab 						awnd = (tp->snd_nxt - tp->snd_fack) +
18890077b016SPaul Saab 							tp->sackhint.sack_bytes_rexmit;
1890808f11b7SPaul Saab 						if (awnd < tp->snd_ssthresh) {
189125e6f9edSPaul Saab 							tp->snd_cwnd += tp->t_maxseg;
189225e6f9edSPaul Saab 							if (tp->snd_cwnd > tp->snd_ssthresh)
189325e6f9edSPaul Saab 								tp->snd_cwnd = tp->snd_ssthresh;
189425e6f9edSPaul Saab 						}
189525e6f9edSPaul Saab 					} else
189646f58482SJonathan Lemon 						tp->snd_cwnd += tp->t_maxseg;
189746f58482SJonathan Lemon 					(void) tcp_output(tp);
189846f58482SJonathan Lemon 					goto drop;
1899cb942153SJeffrey Hsu 				} else if (tp->t_dupacks == tcprexmtthresh) {
1900cb942153SJeffrey Hsu 					tcp_seq onxt = tp->snd_nxt;
1901cb942153SJeffrey Hsu 					u_int win;
1902a0445c2eSJayanth Vijayaraghavan 
1903a0445c2eSJayanth Vijayaraghavan 					/*
1904a0445c2eSJayanth Vijayaraghavan 					 * If we're doing sack, check to
1905a0445c2eSJayanth Vijayaraghavan 					 * see if we're already in sack
1906a0445c2eSJayanth Vijayaraghavan 					 * recovery. If we're not doing sack,
1907a0445c2eSJayanth Vijayaraghavan 					 * check to see if we're in newreno
1908a0445c2eSJayanth Vijayaraghavan 					 * recovery.
1909a0445c2eSJayanth Vijayaraghavan 					 */
1910a0445c2eSJayanth Vijayaraghavan 					if (tp->sack_enable) {
1911a0445c2eSJayanth Vijayaraghavan 						if (IN_FASTRECOVERY(tp)) {
1912a0445c2eSJayanth Vijayaraghavan 							tp->t_dupacks = 0;
1913a0445c2eSJayanth Vijayaraghavan 							break;
1914a0445c2eSJayanth Vijayaraghavan 						}
1915a0445c2eSJayanth Vijayaraghavan 					} else if (tcp_do_newreno) {
1916a0445c2eSJayanth Vijayaraghavan 						if (SEQ_LEQ(th->th_ack,
19179d11646dSJeffrey Hsu 						    tp->snd_recover)) {
1918cb942153SJeffrey Hsu 							tp->t_dupacks = 0;
1919cb942153SJeffrey Hsu 							break;
192046f58482SJonathan Lemon 						}
1921a0445c2eSJayanth Vijayaraghavan 					}
1922cb942153SJeffrey Hsu 					win = min(tp->snd_wnd, tp->snd_cwnd) /
1923cb942153SJeffrey Hsu 					    2 / tp->t_maxseg;
1924df8bae1dSRodney W. Grimes 					if (win < 2)
1925df8bae1dSRodney W. Grimes 						win = 2;
1926df8bae1dSRodney W. Grimes 					tp->snd_ssthresh = win * tp->t_maxseg;
19279d11646dSJeffrey Hsu 					ENTER_FASTRECOVERY(tp);
192846f58482SJonathan Lemon 					tp->snd_recover = tp->snd_max;
19299b8b58e0SJonathan Lemon 					callout_stop(tp->tt_rexmt);
19309b8b58e0SJonathan Lemon 					tp->t_rtttime = 0;
19316d90faf3SPaul Saab 					if (tp->sack_enable) {
19326d90faf3SPaul Saab 						tcpstat.tcps_sack_recovery_episode++;
1933a55db2b6SPaul Saab 						tp->sack_newdata = tp->snd_nxt;
19348db456bfSPaul Saab 						tp->snd_cwnd = tp->t_maxseg;
19356d90faf3SPaul Saab 						(void) tcp_output(tp);
19366d90faf3SPaul Saab 						goto drop;
19376d90faf3SPaul Saab 					}
1938fb59c426SYoshinobu Inoue 					tp->snd_nxt = th->th_ack;
1939df8bae1dSRodney W. Grimes 					tp->snd_cwnd = tp->t_maxseg;
1940df8bae1dSRodney W. Grimes 					(void) tcp_output(tp);
194148d2549cSJeffrey Hsu 					KASSERT(tp->snd_limited <= 2,
194248d2549cSJeffrey Hsu 					    ("tp->snd_limited too big"));
1943df8bae1dSRodney W. Grimes 					tp->snd_cwnd = tp->snd_ssthresh +
194448d2549cSJeffrey Hsu 					     tp->t_maxseg *
194548d2549cSJeffrey Hsu 					     (tp->t_dupacks - tp->snd_limited);
1946df8bae1dSRodney W. Grimes 					if (SEQ_GT(onxt, tp->snd_nxt))
1947df8bae1dSRodney W. Grimes 						tp->snd_nxt = onxt;
1948df8bae1dSRodney W. Grimes 					goto drop;
1949582a954bSJeffrey Hsu 				} else if (tcp_do_rfc3042) {
1950582a954bSJeffrey Hsu 					u_long oldcwnd = tp->snd_cwnd;
195148d2549cSJeffrey Hsu 					tcp_seq oldsndmax = tp->snd_max;
195248d2549cSJeffrey Hsu 					u_int sent;
195389c02376SJeffrey Hsu 
1954582a954bSJeffrey Hsu 					KASSERT(tp->t_dupacks == 1 ||
1955582a954bSJeffrey Hsu 					    tp->t_dupacks == 2,
1956582a954bSJeffrey Hsu 					    ("dupacks not 1 or 2"));
195761a36e3dSJeffrey Hsu 					if (tp->t_dupacks == 1)
195848d2549cSJeffrey Hsu 						tp->snd_limited = 0;
195961a36e3dSJeffrey Hsu 					tp->snd_cwnd =
196061a36e3dSJeffrey Hsu 					    (tp->snd_nxt - tp->snd_una) +
196161a36e3dSJeffrey Hsu 					    (tp->t_dupacks - tp->snd_limited) *
196261a36e3dSJeffrey Hsu 					    tp->t_maxseg;
1963582a954bSJeffrey Hsu 					(void) tcp_output(tp);
196448d2549cSJeffrey Hsu 					sent = tp->snd_max - oldsndmax;
196548d2549cSJeffrey Hsu 					if (sent > tp->t_maxseg) {
196689c02376SJeffrey Hsu 						KASSERT((tp->t_dupacks == 2 &&
196789c02376SJeffrey Hsu 						    tp->snd_limited == 0) ||
196889c02376SJeffrey Hsu 						   (sent == tp->t_maxseg + 1 &&
196989c02376SJeffrey Hsu 						    tp->t_flags & TF_SENTFIN),
197048d2549cSJeffrey Hsu 						    ("sent too much"));
197148d2549cSJeffrey Hsu 						tp->snd_limited = 2;
197248d2549cSJeffrey Hsu 					} else if (sent > 0)
197348d2549cSJeffrey Hsu 						++tp->snd_limited;
1974582a954bSJeffrey Hsu 					tp->snd_cwnd = oldcwnd;
1975582a954bSJeffrey Hsu 					goto drop;
1976df8bae1dSRodney W. Grimes 				}
1977df8bae1dSRodney W. Grimes 			} else
1978df8bae1dSRodney W. Grimes 				tp->t_dupacks = 0;
1979df8bae1dSRodney W. Grimes 			break;
1980df8bae1dSRodney W. Grimes 		}
1981cb942153SJeffrey Hsu 
1982cb942153SJeffrey Hsu 		KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una"));
1983cb942153SJeffrey Hsu 
1984df8bae1dSRodney W. Grimes 		/*
1985df8bae1dSRodney W. Grimes 		 * If the congestion window was inflated to account
1986df8bae1dSRodney W. Grimes 		 * for the other side's cached packets, retract it.
1987df8bae1dSRodney W. Grimes 		 */
19886d90faf3SPaul Saab 		if (tcp_do_newreno || tp->sack_enable) {
19899d11646dSJeffrey Hsu 			if (IN_FASTRECOVERY(tp)) {
1990cb942153SJeffrey Hsu 				if (SEQ_LT(th->th_ack, tp->snd_recover)) {
19916d90faf3SPaul Saab 					if (tp->sack_enable)
19926d90faf3SPaul Saab 						tcp_sack_partialack(tp, th);
19936d90faf3SPaul Saab 					else
1994c068736aSJeffrey Hsu 						tcp_newreno_partial_ack(tp, th);
1995c068736aSJeffrey Hsu 				} else {
1996c068736aSJeffrey Hsu 					/*
19976d90faf3SPaul Saab 					 * Out of fast recovery.
1998c068736aSJeffrey Hsu 					 * Window inflation should have left us
1999c068736aSJeffrey Hsu 					 * with approximately snd_ssthresh
2000c068736aSJeffrey Hsu 					 * outstanding data.
2001c068736aSJeffrey Hsu 					 * But in case we would be inclined to
2002c068736aSJeffrey Hsu 					 * send a burst, better to do it via
2003c068736aSJeffrey Hsu 					 * the slow start mechanism.
2004c068736aSJeffrey Hsu 					 */
2005c068736aSJeffrey Hsu 					if (SEQ_GT(th->th_ack +
2006c068736aSJeffrey Hsu 							tp->snd_ssthresh,
2007c068736aSJeffrey Hsu 						   tp->snd_max))
2008c068736aSJeffrey Hsu 						tp->snd_cwnd = tp->snd_max -
2009c068736aSJeffrey Hsu 								th->th_ack +
2010c068736aSJeffrey Hsu 								tp->t_maxseg;
2011c068736aSJeffrey Hsu 					else
2012c068736aSJeffrey Hsu 						tp->snd_cwnd = tp->snd_ssthresh;
2013c068736aSJeffrey Hsu 				}
2014c068736aSJeffrey Hsu 			}
2015c068736aSJeffrey Hsu 		} else {
2016233e8c18SGarrett Wollman 			if (tp->t_dupacks >= tcprexmtthresh &&
2017df8bae1dSRodney W. Grimes 			    tp->snd_cwnd > tp->snd_ssthresh)
2018df8bae1dSRodney W. Grimes 				tp->snd_cwnd = tp->snd_ssthresh;
201946f58482SJonathan Lemon 		}
2020cb942153SJeffrey Hsu 		tp->t_dupacks = 0;
2021a0292f23SGarrett Wollman 		/*
2022a0292f23SGarrett Wollman 		 * If we reach this point, ACK is not a duplicate,
2023a0292f23SGarrett Wollman 		 *     i.e., it ACKs something we sent.
2024a0292f23SGarrett Wollman 		 */
2025a0292f23SGarrett Wollman 		if (tp->t_flags & TF_NEEDSYN) {
2026a0292f23SGarrett Wollman 			/*
2027a0292f23SGarrett Wollman 			 * T/TCP: Connection was half-synchronized, and our
2028a0292f23SGarrett Wollman 			 * SYN has been ACK'd (so connection is now fully
202907e43e10SAndras Olah 			 * synchronized).  Go to non-starred state,
203007e43e10SAndras Olah 			 * increment snd_una for ACK of SYN, and check if
203107e43e10SAndras Olah 			 * we can do window scaling.
2032a0292f23SGarrett Wollman 			 */
2033a0292f23SGarrett Wollman 			tp->t_flags &= ~TF_NEEDSYN;
2034a0292f23SGarrett Wollman 			tp->snd_una++;
203507e43e10SAndras Olah 			/* Do window scaling? */
203607e43e10SAndras Olah 			if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
203707e43e10SAndras Olah 				(TF_RCVD_SCALE|TF_REQ_SCALE)) {
203807e43e10SAndras Olah 				tp->snd_scale = tp->requested_s_scale;
203907e43e10SAndras Olah 				tp->rcv_scale = tp->request_r_scale;
204007e43e10SAndras Olah 			}
2041a0292f23SGarrett Wollman 		}
2042a0292f23SGarrett Wollman 
2043a0292f23SGarrett Wollman process_ACK:
2044de30ea13SRobert Watson 		KASSERT(headlocked, ("tcp_input: process_ACK: head not "
2045de30ea13SRobert Watson 		    "locked"));
20467cfc6904SRobert Watson 		INP_LOCK_ASSERT(inp);
20477cfc6904SRobert Watson 
2048fb59c426SYoshinobu Inoue 		acked = th->th_ack - tp->snd_una;
2049df8bae1dSRodney W. Grimes 		tcpstat.tcps_rcvackpack++;
2050df8bae1dSRodney W. Grimes 		tcpstat.tcps_rcvackbyte += acked;
2051df8bae1dSRodney W. Grimes 
2052df8bae1dSRodney W. Grimes 		/*
20539b8b58e0SJonathan Lemon 		 * If we just performed our first retransmit, and the ACK
20549b8b58e0SJonathan Lemon 		 * arrives within our recovery window, then it was a mistake
20559b8b58e0SJonathan Lemon 		 * to do the retransmit in the first place.  Recover our
20569b8b58e0SJonathan Lemon 		 * original cwnd and ssthresh, and proceed to transmit where
20579b8b58e0SJonathan Lemon 		 * we left off.
20589b8b58e0SJonathan Lemon 		 */
20599b8b58e0SJonathan Lemon 		if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) {
2060d65bf08aSMatthew Dillon 			++tcpstat.tcps_sndrexmitbad;
20619b8b58e0SJonathan Lemon 			tp->snd_cwnd = tp->snd_cwnd_prev;
20629b8b58e0SJonathan Lemon 			tp->snd_ssthresh = tp->snd_ssthresh_prev;
20639d11646dSJeffrey Hsu 			tp->snd_recover = tp->snd_recover_prev;
20649d11646dSJeffrey Hsu 			if (tp->t_flags & TF_WASFRECOVERY)
20659d11646dSJeffrey Hsu 				ENTER_FASTRECOVERY(tp);
20669b8b58e0SJonathan Lemon 			tp->snd_nxt = tp->snd_max;
20679b8b58e0SJonathan Lemon 			tp->t_badrxtwin = 0;	/* XXX probably not required */
20689b8b58e0SJonathan Lemon 		}
20699b8b58e0SJonathan Lemon 
20709b8b58e0SJonathan Lemon 		/*
2071df8bae1dSRodney W. Grimes 		 * If we have a timestamp reply, update smoothed
2072df8bae1dSRodney W. Grimes 		 * round trip time.  If no timestamp is present but
2073df8bae1dSRodney W. Grimes 		 * transmit timer is running and timed sequence
2074df8bae1dSRodney W. Grimes 		 * number was acked, update smoothed round trip time.
2075df8bae1dSRodney W. Grimes 		 * Since we now have an rtt measurement, cancel the
2076df8bae1dSRodney W. Grimes 		 * timer backoff (cf., Phil Karn's retransmit alg.).
2077df8bae1dSRodney W. Grimes 		 * Recompute the initial retransmit timer.
2078fa55172bSMatthew Dillon 		 *
2079fa55172bSMatthew Dillon 		 * Some boxes send broken timestamp replies
2080fa55172bSMatthew Dillon 		 * during the SYN+ACK phase, ignore
2081fa55172bSMatthew Dillon 		 * timestamps of 0 or we could calculate a
2082fa55172bSMatthew Dillon 		 * huge RTT and blow up the retransmit timer.
2083df8bae1dSRodney W. Grimes 		 */
2084fa55172bSMatthew Dillon 		if ((to.to_flags & TOF_TS) != 0 &&
2085fa55172bSMatthew Dillon 		    to.to_tsecr) {
2086eaf80179SAndre Oppermann 			if (!tp->t_rttlow || tp->t_rttlow > ticks - to.to_tsecr)
2087eaf80179SAndre Oppermann 				tp->t_rttlow = ticks - to.to_tsecr;
20889b8b58e0SJonathan Lemon 			tcp_xmit_timer(tp, ticks - to.to_tsecr + 1);
2089fa55172bSMatthew Dillon 		} else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) {
2090eaf80179SAndre Oppermann 			if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime)
2091eaf80179SAndre Oppermann 				tp->t_rttlow = ticks - tp->t_rtttime;
20929b8b58e0SJonathan Lemon 			tcp_xmit_timer(tp, ticks - tp->t_rtttime);
2093fa55172bSMatthew Dillon 		}
20941fcc99b5SMatthew Dillon 		tcp_xmit_bandwidth_limit(tp, th->th_ack);
2095df8bae1dSRodney W. Grimes 
2096df8bae1dSRodney W. Grimes 		/*
2097df8bae1dSRodney W. Grimes 		 * If all outstanding data is acked, stop retransmit
2098df8bae1dSRodney W. Grimes 		 * timer and remember to restart (more output or persist).
2099df8bae1dSRodney W. Grimes 		 * If there is more data to be acked, restart retransmit
2100df8bae1dSRodney W. Grimes 		 * timer, using current (possibly backed-off) value.
2101df8bae1dSRodney W. Grimes 		 */
2102fb59c426SYoshinobu Inoue 		if (th->th_ack == tp->snd_max) {
21039b8b58e0SJonathan Lemon 			callout_stop(tp->tt_rexmt);
2104df8bae1dSRodney W. Grimes 			needoutput = 1;
21059b8b58e0SJonathan Lemon 		} else if (!callout_active(tp->tt_persist))
21069b8b58e0SJonathan Lemon 			callout_reset(tp->tt_rexmt, tp->t_rxtcur,
21079b8b58e0SJonathan Lemon 				      tcp_timer_rexmt, tp);
2108a0292f23SGarrett Wollman 
2109a0292f23SGarrett Wollman 		/*
2110a0292f23SGarrett Wollman 		 * If no data (only SYN) was ACK'd,
2111a0292f23SGarrett Wollman 		 *    skip rest of ACK processing.
2112a0292f23SGarrett Wollman 		 */
2113a0292f23SGarrett Wollman 		if (acked == 0)
2114a0292f23SGarrett Wollman 			goto step6;
2115a0292f23SGarrett Wollman 
2116df8bae1dSRodney W. Grimes 		/*
2117df8bae1dSRodney W. Grimes 		 * When new data is acked, open the congestion window.
2118df8bae1dSRodney W. Grimes 		 * If the window gives us less than ssthresh packets
2119df8bae1dSRodney W. Grimes 		 * in flight, open exponentially (maxseg per packet).
2120df8bae1dSRodney W. Grimes 		 * Otherwise open linearly: maxseg per window
212110be5648SGarrett Wollman 		 * (maxseg^2 / cwnd per packet).
2122df8bae1dSRodney W. Grimes 		 */
21236d90faf3SPaul Saab 		if ((!tcp_do_newreno && !tp->sack_enable) ||
21246d90faf3SPaul Saab 		    !IN_FASTRECOVERY(tp)) {
2125df8bae1dSRodney W. Grimes 			register u_int cw = tp->snd_cwnd;
2126df8bae1dSRodney W. Grimes 			register u_int incr = tp->t_maxseg;
2127df8bae1dSRodney W. Grimes 			if (cw > tp->snd_ssthresh)
212810be5648SGarrett Wollman 				incr = incr * incr / cw;
2129df8bae1dSRodney W. Grimes 			tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale);
2130df8bae1dSRodney W. Grimes 		}
21315905999bSRobert Watson 		SOCKBUF_LOCK(&so->so_snd);
2132df8bae1dSRodney W. Grimes 		if (acked > so->so_snd.sb_cc) {
2133df8bae1dSRodney W. Grimes 			tp->snd_wnd -= so->so_snd.sb_cc;
21345905999bSRobert Watson 			sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc);
2135df8bae1dSRodney W. Grimes 			ourfinisacked = 1;
2136df8bae1dSRodney W. Grimes 		} else {
21375905999bSRobert Watson 			sbdrop_locked(&so->so_snd, acked);
2138df8bae1dSRodney W. Grimes 			tp->snd_wnd -= acked;
2139df8bae1dSRodney W. Grimes 			ourfinisacked = 0;
2140df8bae1dSRodney W. Grimes 		}
21411e4d7da7SRobert Watson 		sowwakeup_locked(so);
2142cb942153SJeffrey Hsu 		/* detect una wraparound */
21436d90faf3SPaul Saab 		if ((tcp_do_newreno || tp->sack_enable) &&
21446d90faf3SPaul Saab 		    !IN_FASTRECOVERY(tp) &&
21459d11646dSJeffrey Hsu 		    SEQ_GT(tp->snd_una, tp->snd_recover) &&
21469d11646dSJeffrey Hsu 		    SEQ_LEQ(th->th_ack, tp->snd_recover))
21479d11646dSJeffrey Hsu 			tp->snd_recover = th->th_ack - 1;
21486d90faf3SPaul Saab 		if ((tcp_do_newreno || tp->sack_enable) &&
21496d90faf3SPaul Saab 		    IN_FASTRECOVERY(tp) &&
21509d11646dSJeffrey Hsu 		    SEQ_GEQ(th->th_ack, tp->snd_recover))
21519d11646dSJeffrey Hsu 			EXIT_FASTRECOVERY(tp);
2152fb59c426SYoshinobu Inoue 		tp->snd_una = th->th_ack;
21536d90faf3SPaul Saab 		if (tp->sack_enable) {
21546d90faf3SPaul Saab 			if (SEQ_GT(tp->snd_una, tp->snd_recover))
21556d90faf3SPaul Saab 				tp->snd_recover = tp->snd_una;
21566d90faf3SPaul Saab 		}
2157df8bae1dSRodney W. Grimes 		if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2158df8bae1dSRodney W. Grimes 			tp->snd_nxt = tp->snd_una;
2159df8bae1dSRodney W. Grimes 
2160df8bae1dSRodney W. Grimes 		switch (tp->t_state) {
2161df8bae1dSRodney W. Grimes 
2162df8bae1dSRodney W. Grimes 		/*
2163df8bae1dSRodney W. Grimes 		 * In FIN_WAIT_1 STATE in addition to the processing
2164df8bae1dSRodney W. Grimes 		 * for the ESTABLISHED state if our FIN is now acknowledged
2165df8bae1dSRodney W. Grimes 		 * then enter FIN_WAIT_2.
2166df8bae1dSRodney W. Grimes 		 */
2167df8bae1dSRodney W. Grimes 		case TCPS_FIN_WAIT_1:
2168df8bae1dSRodney W. Grimes 			if (ourfinisacked) {
2169df8bae1dSRodney W. Grimes 				/*
2170df8bae1dSRodney W. Grimes 				 * If we can't receive any more
2171df8bae1dSRodney W. Grimes 				 * data, then closing user can proceed.
2172df8bae1dSRodney W. Grimes 				 * Starting the timer is contrary to the
2173df8bae1dSRodney W. Grimes 				 * specification, but if we don't get a FIN
2174df8bae1dSRodney W. Grimes 				 * we'll hang forever.
2175df8bae1dSRodney W. Grimes 				 */
2176340c35deSJonathan Lemon 		/* XXXjl
2177340c35deSJonathan Lemon 		 * we should release the tp also, and use a
2178340c35deSJonathan Lemon 		 * compressed state.
2179340c35deSJonathan Lemon 		 */
2180c0b99ffaSRobert Watson 				if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
218103e49181SSeigo Tanimura 					soisdisconnected(so);
21829b8b58e0SJonathan Lemon 					callout_reset(tp->tt_2msl, tcp_maxidle,
21839b8b58e0SJonathan Lemon 						      tcp_timer_2msl, tp);
21844cc20ab1SSeigo Tanimura 				}
2185df8bae1dSRodney W. Grimes 				tp->t_state = TCPS_FIN_WAIT_2;
2186df8bae1dSRodney W. Grimes 			}
2187df8bae1dSRodney W. Grimes 			break;
2188df8bae1dSRodney W. Grimes 
2189df8bae1dSRodney W. Grimes 		/*
2190df8bae1dSRodney W. Grimes 		 * In CLOSING STATE in addition to the processing for
2191df8bae1dSRodney W. Grimes 		 * the ESTABLISHED state if the ACK acknowledges our FIN
2192df8bae1dSRodney W. Grimes 		 * then enter the TIME-WAIT state, otherwise ignore
2193df8bae1dSRodney W. Grimes 		 * the segment.
2194df8bae1dSRodney W. Grimes 		 */
2195df8bae1dSRodney W. Grimes 		case TCPS_CLOSING:
2196df8bae1dSRodney W. Grimes 			if (ourfinisacked) {
2197de30ea13SRobert Watson 				KASSERT(headlocked, ("tcp_input: process_ACK: "
2198de30ea13SRobert Watson 				    "head not locked"));
219911a20fb8SJeffrey Hsu 				tcp_twstart(tp);
2200340c35deSJonathan Lemon 				INP_INFO_WUNLOCK(&tcbinfo);
2201340c35deSJonathan Lemon 				m_freem(m);
2202340c35deSJonathan Lemon 				return;
2203df8bae1dSRodney W. Grimes 			}
2204df8bae1dSRodney W. Grimes 			break;
2205df8bae1dSRodney W. Grimes 
2206df8bae1dSRodney W. Grimes 		/*
2207df8bae1dSRodney W. Grimes 		 * In LAST_ACK, we may still be waiting for data to drain
2208df8bae1dSRodney W. Grimes 		 * and/or to be acked, as well as for the ack of our FIN.
2209df8bae1dSRodney W. Grimes 		 * If our FIN is now acknowledged, delete the TCB,
2210df8bae1dSRodney W. Grimes 		 * enter the closed state and return.
2211df8bae1dSRodney W. Grimes 		 */
2212df8bae1dSRodney W. Grimes 		case TCPS_LAST_ACK:
2213df8bae1dSRodney W. Grimes 			if (ourfinisacked) {
2214416738a7SRobert Watson 				KASSERT(headlocked, ("tcp_input: process_ACK:"
2215416738a7SRobert Watson 				    " tcp_close: head not locked"));
2216df8bae1dSRodney W. Grimes 				tp = tcp_close(tp);
2217df8bae1dSRodney W. Grimes 				goto drop;
2218df8bae1dSRodney W. Grimes 			}
2219df8bae1dSRodney W. Grimes 			break;
2220df8bae1dSRodney W. Grimes 
2221df8bae1dSRodney W. Grimes 		/*
2222df8bae1dSRodney W. Grimes 		 * In TIME_WAIT state the only thing that should arrive
2223df8bae1dSRodney W. Grimes 		 * is a retransmission of the remote FIN.  Acknowledge
2224df8bae1dSRodney W. Grimes 		 * it and restart the finack timer.
2225df8bae1dSRodney W. Grimes 		 */
2226df8bae1dSRodney W. Grimes 		case TCPS_TIME_WAIT:
2227340c35deSJonathan Lemon 			KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
22289b8b58e0SJonathan Lemon 			callout_reset(tp->tt_2msl, 2 * tcp_msl,
22299b8b58e0SJonathan Lemon 				      tcp_timer_2msl, tp);
2230df8bae1dSRodney W. Grimes 			goto dropafterack;
2231df8bae1dSRodney W. Grimes 		}
2232df8bae1dSRodney W. Grimes 	}
2233df8bae1dSRodney W. Grimes 
2234df8bae1dSRodney W. Grimes step6:
2235de30ea13SRobert Watson 	KASSERT(headlocked, ("tcp_input: step6: head not locked"));
22367cfc6904SRobert Watson 	INP_LOCK_ASSERT(inp);
22377cfc6904SRobert Watson 
2238df8bae1dSRodney W. Grimes 	/*
2239df8bae1dSRodney W. Grimes 	 * Update window information.
2240df8bae1dSRodney W. Grimes 	 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2241df8bae1dSRodney W. Grimes 	 */
2242fb59c426SYoshinobu Inoue 	if ((thflags & TH_ACK) &&
2243fb59c426SYoshinobu Inoue 	    (SEQ_LT(tp->snd_wl1, th->th_seq) ||
2244fb59c426SYoshinobu Inoue 	    (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) ||
2245fb59c426SYoshinobu Inoue 	     (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
2246df8bae1dSRodney W. Grimes 		/* keep track of pure window updates */
2247fb59c426SYoshinobu Inoue 		if (tlen == 0 &&
2248fb59c426SYoshinobu Inoue 		    tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)
2249df8bae1dSRodney W. Grimes 			tcpstat.tcps_rcvwinupd++;
2250df8bae1dSRodney W. Grimes 		tp->snd_wnd = tiwin;
2251fb59c426SYoshinobu Inoue 		tp->snd_wl1 = th->th_seq;
2252fb59c426SYoshinobu Inoue 		tp->snd_wl2 = th->th_ack;
2253df8bae1dSRodney W. Grimes 		if (tp->snd_wnd > tp->max_sndwnd)
2254df8bae1dSRodney W. Grimes 			tp->max_sndwnd = tp->snd_wnd;
2255df8bae1dSRodney W. Grimes 		needoutput = 1;
2256df8bae1dSRodney W. Grimes 	}
2257df8bae1dSRodney W. Grimes 
2258df8bae1dSRodney W. Grimes 	/*
2259df8bae1dSRodney W. Grimes 	 * Process segments with URG.
2260df8bae1dSRodney W. Grimes 	 */
2261fb59c426SYoshinobu Inoue 	if ((thflags & TH_URG) && th->th_urp &&
2262df8bae1dSRodney W. Grimes 	    TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2263df8bae1dSRodney W. Grimes 		/*
2264df8bae1dSRodney W. Grimes 		 * This is a kludge, but if we receive and accept
2265df8bae1dSRodney W. Grimes 		 * random urgent pointers, we'll crash in
2266df8bae1dSRodney W. Grimes 		 * soreceive.  It's hard to imagine someone
2267df8bae1dSRodney W. Grimes 		 * actually wanting to send this much urgent data.
2268df8bae1dSRodney W. Grimes 		 */
226918ad5842SRobert Watson 		SOCKBUF_LOCK(&so->so_rcv);
2270fb59c426SYoshinobu Inoue 		if (th->th_urp + so->so_rcv.sb_cc > sb_max) {
2271fb59c426SYoshinobu Inoue 			th->th_urp = 0;			/* XXX */
2272fb59c426SYoshinobu Inoue 			thflags &= ~TH_URG;		/* XXX */
227318ad5842SRobert Watson 			SOCKBUF_UNLOCK(&so->so_rcv);	/* XXX */
2274df8bae1dSRodney W. Grimes 			goto dodata;			/* XXX */
2275df8bae1dSRodney W. Grimes 		}
2276df8bae1dSRodney W. Grimes 		/*
2277df8bae1dSRodney W. Grimes 		 * If this segment advances the known urgent pointer,
2278df8bae1dSRodney W. Grimes 		 * then mark the data stream.  This should not happen
2279df8bae1dSRodney W. Grimes 		 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2280df8bae1dSRodney W. Grimes 		 * a FIN has been received from the remote side.
2281df8bae1dSRodney W. Grimes 		 * In these states we ignore the URG.
2282df8bae1dSRodney W. Grimes 		 *
2283df8bae1dSRodney W. Grimes 		 * According to RFC961 (Assigned Protocols),
2284df8bae1dSRodney W. Grimes 		 * the urgent pointer points to the last octet
2285df8bae1dSRodney W. Grimes 		 * of urgent data.  We continue, however,
2286df8bae1dSRodney W. Grimes 		 * to consider it to indicate the first octet
2287df8bae1dSRodney W. Grimes 		 * of data past the urgent section as the original
2288df8bae1dSRodney W. Grimes 		 * spec states (in one of two places).
2289df8bae1dSRodney W. Grimes 		 */
2290fb59c426SYoshinobu Inoue 		if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) {
2291fb59c426SYoshinobu Inoue 			tp->rcv_up = th->th_seq + th->th_urp;
2292df8bae1dSRodney W. Grimes 			so->so_oobmark = so->so_rcv.sb_cc +
2293df8bae1dSRodney W. Grimes 			    (tp->rcv_up - tp->rcv_nxt) - 1;
2294927c5ceaSRobert Watson 			if (so->so_oobmark == 0)
2295c0b99ffaSRobert Watson 				so->so_rcv.sb_state |= SBS_RCVATMARK;
2296df8bae1dSRodney W. Grimes 			sohasoutofband(so);
2297df8bae1dSRodney W. Grimes 			tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2298df8bae1dSRodney W. Grimes 		}
229918ad5842SRobert Watson 		SOCKBUF_UNLOCK(&so->so_rcv);
2300df8bae1dSRodney W. Grimes 		/*
2301df8bae1dSRodney W. Grimes 		 * Remove out of band data so doesn't get presented to user.
2302df8bae1dSRodney W. Grimes 		 * This can happen independent of advancing the URG pointer,
2303df8bae1dSRodney W. Grimes 		 * but if two URG's are pending at once, some out-of-band
2304df8bae1dSRodney W. Grimes 		 * data may creep in... ick.
2305df8bae1dSRodney W. Grimes 		 */
230630613f56SJeffrey Hsu 		if (th->th_urp <= (u_long)tlen &&
230730613f56SJeffrey Hsu 		    !(so->so_options & SO_OOBINLINE)) {
230830613f56SJeffrey Hsu 			/* hdr drop is delayed */
230930613f56SJeffrey Hsu 			tcp_pulloutofband(so, th, m, drop_hdrlen);
231030613f56SJeffrey Hsu 		}
2311c068736aSJeffrey Hsu 	} else {
2312df8bae1dSRodney W. Grimes 		/*
2313df8bae1dSRodney W. Grimes 		 * If no out of band data is expected,
2314df8bae1dSRodney W. Grimes 		 * pull receive urgent pointer along
2315df8bae1dSRodney W. Grimes 		 * with the receive window.
2316df8bae1dSRodney W. Grimes 		 */
2317df8bae1dSRodney W. Grimes 		if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2318df8bae1dSRodney W. Grimes 			tp->rcv_up = tp->rcv_nxt;
2319c068736aSJeffrey Hsu 	}
2320df8bae1dSRodney W. Grimes dodata:							/* XXX */
2321de30ea13SRobert Watson 	KASSERT(headlocked, ("tcp_input: dodata: head not locked"));
23227cfc6904SRobert Watson 	INP_LOCK_ASSERT(inp);
23237cfc6904SRobert Watson 
2324df8bae1dSRodney W. Grimes 	/*
2325df8bae1dSRodney W. Grimes 	 * Process the segment text, merging it into the TCP sequencing queue,
2326df8bae1dSRodney W. Grimes 	 * and arranging for acknowledgment of receipt if necessary.
2327df8bae1dSRodney W. Grimes 	 * This process logically involves adjusting tp->rcv_wnd as data
2328df8bae1dSRodney W. Grimes 	 * is presented to the user (this happens in tcp_usrreq.c,
2329df8bae1dSRodney W. Grimes 	 * case PRU_RCVD).  If a FIN has already been received on this
2330df8bae1dSRodney W. Grimes 	 * connection then we just ignore the text.
2331df8bae1dSRodney W. Grimes 	 */
2332fb59c426SYoshinobu Inoue 	if ((tlen || (thflags & TH_FIN)) &&
2333df8bae1dSRodney W. Grimes 	    TCPS_HAVERCVDFIN(tp->t_state) == 0) {
233469e03620SPaul Saab 		tcp_seq save_start = th->th_seq;
233569e03620SPaul Saab 		tcp_seq save_end = th->th_seq + tlen;
2336fb59c426SYoshinobu Inoue 		m_adj(m, drop_hdrlen);	/* delayed header drop */
2337e4b64281SJesper Skriver 		/*
2338c068736aSJeffrey Hsu 		 * Insert segment which includes th into TCP reassembly queue
2339c068736aSJeffrey Hsu 		 * with control block tp.  Set thflags to whether reassembly now
2340c068736aSJeffrey Hsu 		 * includes a segment with FIN.  This handles the common case
2341c068736aSJeffrey Hsu 		 * inline (segment is the next to be received on an established
2342c068736aSJeffrey Hsu 		 * connection, and the queue is empty), avoiding linkage into
2343c068736aSJeffrey Hsu 		 * and removal from the queue and repetition of various
2344c068736aSJeffrey Hsu 		 * conversions.
2345c068736aSJeffrey Hsu 		 * Set DELACK for segments received in order, but ack
2346c068736aSJeffrey Hsu 		 * immediately when segments are out of order (so
2347c068736aSJeffrey Hsu 		 * fast retransmit can work).
2348e4b64281SJesper Skriver 		 */
2349e4b64281SJesper Skriver 		if (th->th_seq == tp->rcv_nxt &&
2350e4b64281SJesper Skriver 		    LIST_EMPTY(&tp->t_segq) &&
2351e4b64281SJesper Skriver 		    TCPS_HAVEESTABLISHED(tp->t_state)) {
2352e4b64281SJesper Skriver 			if (DELAY_ACK(tp))
23533bfd6421SJonathan Lemon 				tp->t_flags |= TF_DELACK;
2354e4b64281SJesper Skriver 			else
2355e4b64281SJesper Skriver 				tp->t_flags |= TF_ACKNOW;
2356e4b64281SJesper Skriver 			tp->rcv_nxt += tlen;
2357e4b64281SJesper Skriver 			thflags = th->th_flags & TH_FIN;
2358e4b64281SJesper Skriver 			tcpstat.tcps_rcvpack++;
2359e4b64281SJesper Skriver 			tcpstat.tcps_rcvbyte += tlen;
2360e4b64281SJesper Skriver 			ND6_HINT(tp);
23611e4d7da7SRobert Watson 			SOCKBUF_LOCK(&so->so_rcv);
2362c0b99ffaSRobert Watson 			if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
2363c1c36a2cSMike Silbersack 				m_freem(m);
2364c1c36a2cSMike Silbersack 			else
23651e4d7da7SRobert Watson 				sbappendstream_locked(&so->so_rcv, m);
23661e4d7da7SRobert Watson 			sorwakeup_locked(so);
2367e4b64281SJesper Skriver 		} else {
2368e4b64281SJesper Skriver 			thflags = tcp_reass(tp, th, &tlen, m);
2369e4b64281SJesper Skriver 			tp->t_flags |= TF_ACKNOW;
2370e4b64281SJesper Skriver 		}
2371e346eeffSPaul Saab 		if (tlen > 0 && tp->sack_enable)
237269e03620SPaul Saab 			tcp_update_sack_list(tp, save_start, save_end);
2373df8bae1dSRodney W. Grimes 		/*
2374df8bae1dSRodney W. Grimes 		 * Note the amount of data that peer has sent into
2375df8bae1dSRodney W. Grimes 		 * our window, in order to estimate the sender's
2376df8bae1dSRodney W. Grimes 		 * buffer size.
2377df8bae1dSRodney W. Grimes 		 */
2378df8bae1dSRodney W. Grimes 		len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
2379df8bae1dSRodney W. Grimes 	} else {
2380df8bae1dSRodney W. Grimes 		m_freem(m);
2381fb59c426SYoshinobu Inoue 		thflags &= ~TH_FIN;
2382df8bae1dSRodney W. Grimes 	}
2383df8bae1dSRodney W. Grimes 
2384df8bae1dSRodney W. Grimes 	/*
2385df8bae1dSRodney W. Grimes 	 * If FIN is received ACK the FIN and let the user know
2386df8bae1dSRodney W. Grimes 	 * that the connection is closing.
2387df8bae1dSRodney W. Grimes 	 */
2388fb59c426SYoshinobu Inoue 	if (thflags & TH_FIN) {
2389df8bae1dSRodney W. Grimes 		if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2390df8bae1dSRodney W. Grimes 			socantrcvmore(so);
2391a0292f23SGarrett Wollman 			/*
2392a0292f23SGarrett Wollman 			 * If connection is half-synchronized
2393d3eede9dSAndras Olah 			 * (ie NEEDSYN flag on) then delay ACK,
2394a0292f23SGarrett Wollman 			 * so it may be piggybacked when SYN is sent.
2395a0292f23SGarrett Wollman 			 * Otherwise, since we received a FIN then no
2396a0292f23SGarrett Wollman 			 * more input can be expected, send ACK now.
2397a0292f23SGarrett Wollman 			 */
23983bfd6421SJonathan Lemon 			if (tp->t_flags & TF_NEEDSYN)
23993bfd6421SJonathan Lemon 				tp->t_flags |= TF_DELACK;
2400a0292f23SGarrett Wollman 			else
2401df8bae1dSRodney W. Grimes 				tp->t_flags |= TF_ACKNOW;
2402df8bae1dSRodney W. Grimes 			tp->rcv_nxt++;
2403df8bae1dSRodney W. Grimes 		}
2404df8bae1dSRodney W. Grimes 		switch (tp->t_state) {
2405df8bae1dSRodney W. Grimes 
2406df8bae1dSRodney W. Grimes 		/*
2407df8bae1dSRodney W. Grimes 		 * In SYN_RECEIVED and ESTABLISHED STATES
2408df8bae1dSRodney W. Grimes 		 * enter the CLOSE_WAIT state.
2409df8bae1dSRodney W. Grimes 		 */
2410df8bae1dSRodney W. Grimes 		case TCPS_SYN_RECEIVED:
24119b8b58e0SJonathan Lemon 			tp->t_starttime = ticks;
24129b8b58e0SJonathan Lemon 			/*FALLTHROUGH*/
2413df8bae1dSRodney W. Grimes 		case TCPS_ESTABLISHED:
2414df8bae1dSRodney W. Grimes 			tp->t_state = TCPS_CLOSE_WAIT;
2415df8bae1dSRodney W. Grimes 			break;
2416df8bae1dSRodney W. Grimes 
2417df8bae1dSRodney W. Grimes 		/*
2418df8bae1dSRodney W. Grimes 		 * If still in FIN_WAIT_1 STATE FIN has not been acked so
2419df8bae1dSRodney W. Grimes 		 * enter the CLOSING state.
2420df8bae1dSRodney W. Grimes 		 */
2421df8bae1dSRodney W. Grimes 		case TCPS_FIN_WAIT_1:
2422df8bae1dSRodney W. Grimes 			tp->t_state = TCPS_CLOSING;
2423df8bae1dSRodney W. Grimes 			break;
2424df8bae1dSRodney W. Grimes 
2425df8bae1dSRodney W. Grimes 		/*
2426df8bae1dSRodney W. Grimes 		 * In FIN_WAIT_2 state enter the TIME_WAIT state,
2427df8bae1dSRodney W. Grimes 		 * starting the time-wait timer, turning off the other
2428df8bae1dSRodney W. Grimes 		 * standard timers.
2429df8bae1dSRodney W. Grimes 		 */
2430df8bae1dSRodney W. Grimes 		case TCPS_FIN_WAIT_2:
2431de30ea13SRobert Watson 			KASSERT(headlocked == 1, ("tcp_input: dodata: "
2432de30ea13SRobert Watson 			    "TCP_FIN_WAIT_2: head not locked"));
2433340c35deSJonathan Lemon 			tcp_twstart(tp);
243411a20fb8SJeffrey Hsu 			INP_INFO_WUNLOCK(&tcbinfo);
2435340c35deSJonathan Lemon 			return;
2436df8bae1dSRodney W. Grimes 
2437df8bae1dSRodney W. Grimes 		/*
2438df8bae1dSRodney W. Grimes 		 * In TIME_WAIT state restart the 2 MSL time_wait timer.
2439df8bae1dSRodney W. Grimes 		 */
2440df8bae1dSRodney W. Grimes 		case TCPS_TIME_WAIT:
2441340c35deSJonathan Lemon 			KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
24429b8b58e0SJonathan Lemon 			callout_reset(tp->tt_2msl, 2 * tcp_msl,
24439b8b58e0SJonathan Lemon 				      tcp_timer_2msl, tp);
2444df8bae1dSRodney W. Grimes 			break;
2445df8bae1dSRodney W. Grimes 		}
2446df8bae1dSRodney W. Grimes 	}
2447e0bef1cbSRobert Watson 	INP_INFO_WUNLOCK(&tcbinfo);
2448e0bef1cbSRobert Watson 	headlocked = 0;
2449610ee2f9SDavid Greenman #ifdef TCPDEBUG
24504cc20ab1SSeigo Tanimura 	if (so->so_options & SO_DEBUG)
2451fb59c426SYoshinobu Inoue 		tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
2452fb59c426SYoshinobu Inoue 			  &tcp_savetcp, 0);
2453610ee2f9SDavid Greenman #endif
2454df8bae1dSRodney W. Grimes 
2455df8bae1dSRodney W. Grimes 	/*
2456df8bae1dSRodney W. Grimes 	 * Return any desired output.
2457df8bae1dSRodney W. Grimes 	 */
2458df8bae1dSRodney W. Grimes 	if (needoutput || (tp->t_flags & TF_ACKNOW))
2459df8bae1dSRodney W. Grimes 		(void) tcp_output(tp);
24607792ea27SJeffrey Hsu 
2461a14c749fSJonathan Lemon check_delack:
2462e0bef1cbSRobert Watson 	KASSERT(headlocked == 0, ("tcp_input: check_delack: head locked"));
24637cfc6904SRobert Watson 	INP_LOCK_ASSERT(inp);
2464a14c749fSJonathan Lemon 	if (tp->t_flags & TF_DELACK) {
24653bfd6421SJonathan Lemon 		tp->t_flags &= ~TF_DELACK;
24663bfd6421SJonathan Lemon 		callout_reset(tp->tt_delack, tcp_delacktime,
24673bfd6421SJonathan Lemon 		    tcp_timer_delack, tp);
24683bfd6421SJonathan Lemon 	}
2469f76fcf6dSJeffrey Hsu 	INP_UNLOCK(inp);
2470df8bae1dSRodney W. Grimes 	return;
2471df8bae1dSRodney W. Grimes 
2472df8bae1dSRodney W. Grimes dropafterack:
2473de30ea13SRobert Watson 	KASSERT(headlocked, ("tcp_input: dropafterack: head not locked"));
2474df8bae1dSRodney W. Grimes 	/*
2475df8bae1dSRodney W. Grimes 	 * Generate an ACK dropping incoming segment if it occupies
2476df8bae1dSRodney W. Grimes 	 * sequence space, where the ACK reflects our state.
247780ab7c0eSGarrett Wollman 	 *
247880ab7c0eSGarrett Wollman 	 * We can now skip the test for the RST flag since all
247980ab7c0eSGarrett Wollman 	 * paths to this code happen after packets containing
248080ab7c0eSGarrett Wollman 	 * RST have been dropped.
248180ab7c0eSGarrett Wollman 	 *
248280ab7c0eSGarrett Wollman 	 * In the SYN-RECEIVED state, don't send an ACK unless the
248380ab7c0eSGarrett Wollman 	 * segment we received passes the SYN-RECEIVED ACK test.
248480ab7c0eSGarrett Wollman 	 * If it fails send a RST.  This breaks the loop in the
248580ab7c0eSGarrett Wollman 	 * "LAND" DoS attack, and also prevents an ACK storm
248680ab7c0eSGarrett Wollman 	 * between two listening ports that have been sent forged
248780ab7c0eSGarrett Wollman 	 * SYN segments, each with the source address of the other.
2488df8bae1dSRodney W. Grimes 	 */
2489fb59c426SYoshinobu Inoue 	if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
2490fb59c426SYoshinobu Inoue 	    (SEQ_GT(tp->snd_una, th->th_ack) ||
2491a57815efSBosko Milekic 	     SEQ_GT(th->th_ack, tp->snd_max)) ) {
2492a57815efSBosko Milekic 		rstreason = BANDLIM_RST_OPENPORT;
2493a57815efSBosko Milekic 		goto dropwithreset;
2494a57815efSBosko Milekic 	}
2495a0292f23SGarrett Wollman #ifdef TCPDEBUG
24964cc20ab1SSeigo Tanimura 	if (so->so_options & SO_DEBUG)
2497fb59c426SYoshinobu Inoue 		tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2498fb59c426SYoshinobu Inoue 			  &tcp_savetcp, 0);
2499a0292f23SGarrett Wollman #endif
250085e8b243SJeffrey Hsu 	KASSERT(headlocked, ("headlocked should be 1"));
250142cf3289SRobert Watson 	INP_INFO_WUNLOCK(&tcbinfo);
2502df8bae1dSRodney W. Grimes 	tp->t_flags |= TF_ACKNOW;
2503df8bae1dSRodney W. Grimes 	(void) tcp_output(tp);
2504f76fcf6dSJeffrey Hsu 	INP_UNLOCK(inp);
2505d6915262SRobert Watson 	m_freem(m);
2506df8bae1dSRodney W. Grimes 	return;
2507df8bae1dSRodney W. Grimes 
2508df8bae1dSRodney W. Grimes dropwithreset:
2509de30ea13SRobert Watson 	KASSERT(headlocked, ("tcp_input: dropwithreset: head not locked"));
2510df8bae1dSRodney W. Grimes 	/*
2511df8bae1dSRodney W. Grimes 	 * Generate a RST, dropping incoming segment.
2512df8bae1dSRodney W. Grimes 	 * Make ACK acceptable to originator of segment.
2513df8bae1dSRodney W. Grimes 	 * Don't bother to respond if destination was broadcast/multicast.
2514df8bae1dSRodney W. Grimes 	 */
2515fb59c426SYoshinobu Inoue 	if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST))
2516df8bae1dSRodney W. Grimes 		goto drop;
2517fb59c426SYoshinobu Inoue 	if (isipv6) {
2518173c0f9fSWarner Losh 		if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
2519173c0f9fSWarner Losh 		    IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
2520fb59c426SYoshinobu Inoue 			goto drop;
2521c068736aSJeffrey Hsu 	} else {
2522173c0f9fSWarner Losh 		if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
2523173c0f9fSWarner Losh 		    IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
25242ca2159fSCrist J. Clark 		    ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
25252ca2159fSCrist J. Clark 		    in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
2526fb59c426SYoshinobu Inoue 			goto drop;
2527c068736aSJeffrey Hsu 	}
2528fb59c426SYoshinobu Inoue 	/* IPv6 anycast check is done at tcp6_input() */
2529a57815efSBosko Milekic 
2530a57815efSBosko Milekic 	/*
2531c59319bfSDag-Erling Smørgrav 	 * Perform bandwidth limiting.
2532a57815efSBosko Milekic 	 */
2533a57815efSBosko Milekic 	if (badport_bandlim(rstreason) < 0)
2534a57815efSBosko Milekic 		goto drop;
2535a57815efSBosko Milekic 
2536a0292f23SGarrett Wollman #ifdef TCPDEBUG
25374cc20ab1SSeigo Tanimura 	if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2538fb59c426SYoshinobu Inoue 		tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2539fb59c426SYoshinobu Inoue 			  &tcp_savetcp, 0);
2540a0292f23SGarrett Wollman #endif
25416fd22cafSJeffrey Hsu 
2542fb59c426SYoshinobu Inoue 	if (thflags & TH_ACK)
2543fb59c426SYoshinobu Inoue 		/* mtod() below is safe as long as hdr dropping is delayed */
2544fb59c426SYoshinobu Inoue 		tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
2545fb59c426SYoshinobu Inoue 			    TH_RST);
2546df8bae1dSRodney W. Grimes 	else {
2547fb59c426SYoshinobu Inoue 		if (thflags & TH_SYN)
2548fb59c426SYoshinobu Inoue 			tlen++;
2549fb59c426SYoshinobu Inoue 		/* mtod() below is safe as long as hdr dropping is delayed */
2550fb59c426SYoshinobu Inoue 		tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen,
2551fb59c426SYoshinobu Inoue 			    (tcp_seq)0, TH_RST|TH_ACK);
2552df8bae1dSRodney W. Grimes 	}
2553c29afad6SSam Leffler 
2554c29afad6SSam Leffler 	if (tp)
2555c29afad6SSam Leffler 		INP_UNLOCK(inp);
2556f76fcf6dSJeffrey Hsu 	if (headlocked)
2557f76fcf6dSJeffrey Hsu 		INP_INFO_WUNLOCK(&tcbinfo);
2558df8bae1dSRodney W. Grimes 	return;
2559df8bae1dSRodney W. Grimes 
2560df8bae1dSRodney W. Grimes drop:
2561df8bae1dSRodney W. Grimes 	/*
2562df8bae1dSRodney W. Grimes 	 * Drop space held by incoming segment and return.
2563df8bae1dSRodney W. Grimes 	 */
2564610ee2f9SDavid Greenman #ifdef TCPDEBUG
25654cc20ab1SSeigo Tanimura 	if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2566fb59c426SYoshinobu Inoue 		tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2567fb59c426SYoshinobu Inoue 			  &tcp_savetcp, 0);
2568a0292f23SGarrett Wollman #endif
2569f76fcf6dSJeffrey Hsu 	if (tp)
2570f76fcf6dSJeffrey Hsu 		INP_UNLOCK(inp);
2571f76fcf6dSJeffrey Hsu 	if (headlocked)
2572f76fcf6dSJeffrey Hsu 		INP_INFO_WUNLOCK(&tcbinfo);
2573d6915262SRobert Watson 	m_freem(m);
2574df8bae1dSRodney W. Grimes 	return;
2575df8bae1dSRodney W. Grimes }
2576df8bae1dSRodney W. Grimes 
2577be2ac88cSJonathan Lemon /*
2578be2ac88cSJonathan Lemon  * Parse TCP options and place in tcpopt.
2579be2ac88cSJonathan Lemon  */
25800312fbe9SPoul-Henning Kamp static void
25815a53ca16SPaul Saab tcp_dooptions(to, cp, cnt, is_syn)
2582be2ac88cSJonathan Lemon 	struct tcpopt *to;
2583df8bae1dSRodney W. Grimes 	u_char *cp;
2584df8bae1dSRodney W. Grimes 	int cnt;
2585152385d1SDavid E. O'Brien 	int is_syn;
2586df8bae1dSRodney W. Grimes {
2587df8bae1dSRodney W. Grimes 	int opt, optlen;
2588df8bae1dSRodney W. Grimes 
2589be2ac88cSJonathan Lemon 	to->to_flags = 0;
2590df8bae1dSRodney W. Grimes 	for (; cnt > 0; cnt -= optlen, cp += optlen) {
2591df8bae1dSRodney W. Grimes 		opt = cp[0];
2592df8bae1dSRodney W. Grimes 		if (opt == TCPOPT_EOL)
2593df8bae1dSRodney W. Grimes 			break;
2594df8bae1dSRodney W. Grimes 		if (opt == TCPOPT_NOP)
2595df8bae1dSRodney W. Grimes 			optlen = 1;
2596df8bae1dSRodney W. Grimes 		else {
2597b474779fSJun-ichiro itojun Hagino 			if (cnt < 2)
2598b474779fSJun-ichiro itojun Hagino 				break;
2599df8bae1dSRodney W. Grimes 			optlen = cp[1];
2600b474779fSJun-ichiro itojun Hagino 			if (optlen < 2 || optlen > cnt)
2601df8bae1dSRodney W. Grimes 				break;
2602df8bae1dSRodney W. Grimes 		}
2603df8bae1dSRodney W. Grimes 		switch (opt) {
2604df8bae1dSRodney W. Grimes 		case TCPOPT_MAXSEG:
2605df8bae1dSRodney W. Grimes 			if (optlen != TCPOLEN_MAXSEG)
2606df8bae1dSRodney W. Grimes 				continue;
2607be2ac88cSJonathan Lemon 			if (!is_syn)
2608df8bae1dSRodney W. Grimes 				continue;
2609be2ac88cSJonathan Lemon 			to->to_flags |= TOF_MSS;
2610be2ac88cSJonathan Lemon 			bcopy((char *)cp + 2,
2611be2ac88cSJonathan Lemon 			    (char *)&to->to_mss, sizeof(to->to_mss));
2612fd8e4ebcSMike Barcroft 			to->to_mss = ntohs(to->to_mss);
2613df8bae1dSRodney W. Grimes 			break;
2614df8bae1dSRodney W. Grimes 		case TCPOPT_WINDOW:
2615df8bae1dSRodney W. Grimes 			if (optlen != TCPOLEN_WINDOW)
2616df8bae1dSRodney W. Grimes 				continue;
2617be2ac88cSJonathan Lemon 			if (! is_syn)
2618df8bae1dSRodney W. Grimes 				continue;
2619be2ac88cSJonathan Lemon 			to->to_flags |= TOF_SCALE;
2620be2ac88cSJonathan Lemon 			to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
2621df8bae1dSRodney W. Grimes 			break;
2622df8bae1dSRodney W. Grimes 		case TCPOPT_TIMESTAMP:
2623df8bae1dSRodney W. Grimes 			if (optlen != TCPOLEN_TIMESTAMP)
2624df8bae1dSRodney W. Grimes 				continue;
2625be2ac88cSJonathan Lemon 			to->to_flags |= TOF_TS;
2626a0292f23SGarrett Wollman 			bcopy((char *)cp + 2,
2627a0292f23SGarrett Wollman 			    (char *)&to->to_tsval, sizeof(to->to_tsval));
2628fd8e4ebcSMike Barcroft 			to->to_tsval = ntohl(to->to_tsval);
2629a0292f23SGarrett Wollman 			bcopy((char *)cp + 6,
2630a0292f23SGarrett Wollman 			    (char *)&to->to_tsecr, sizeof(to->to_tsecr));
2631fd8e4ebcSMike Barcroft 			to->to_tsecr = ntohl(to->to_tsecr);
2632cf09195bSPaul Saab 			/*
2633cf09195bSPaul Saab 			 * If echoed timestamp is later than the current time,
2634cf09195bSPaul Saab 			 * fall back to non RFC1323 RTT calculation.
2635cf09195bSPaul Saab 			 */
2636cf09195bSPaul Saab 			if ((to->to_tsecr != 0) && TSTMP_GT(to->to_tsecr, ticks))
2637cf09195bSPaul Saab 				to->to_tsecr = 0;
2638df8bae1dSRodney W. Grimes 			break;
26391cfd4b53SBruce M Simpson #ifdef TCP_SIGNATURE
26401cfd4b53SBruce M Simpson 		/*
26411cfd4b53SBruce M Simpson 		 * XXX In order to reply to a host which has set the
26421cfd4b53SBruce M Simpson 		 * TCP_SIGNATURE option in its initial SYN, we have to
26431cfd4b53SBruce M Simpson 		 * record the fact that the option was observed here
26441cfd4b53SBruce M Simpson 		 * for the syncache code to perform the correct response.
26451cfd4b53SBruce M Simpson 		 */
26461cfd4b53SBruce M Simpson 		case TCPOPT_SIGNATURE:
26471cfd4b53SBruce M Simpson 			if (optlen != TCPOLEN_SIGNATURE)
26481cfd4b53SBruce M Simpson 				continue;
26491cfd4b53SBruce M Simpson 			to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN);
26501cfd4b53SBruce M Simpson 			break;
2651265ed012SBruce M Simpson #endif
26526d90faf3SPaul Saab 		case TCPOPT_SACK_PERMITTED:
26536d90faf3SPaul Saab 			if (!tcp_do_sack ||
26546d90faf3SPaul Saab 			    optlen != TCPOLEN_SACK_PERMITTED)
26556d90faf3SPaul Saab 				continue;
26566d90faf3SPaul Saab 			if (is_syn) {
26576d90faf3SPaul Saab 				/* MUST only be set on SYN */
26586d90faf3SPaul Saab 				to->to_flags |= TOF_SACK;
26596d90faf3SPaul Saab 			}
26606d90faf3SPaul Saab 			break;
26616d90faf3SPaul Saab 		case TCPOPT_SACK:
26625a53ca16SPaul Saab 			if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0)
26636d90faf3SPaul Saab 				continue;
26645a53ca16SPaul Saab 			to->to_nsacks = (optlen - 2) / TCPOLEN_SACK;
26655a53ca16SPaul Saab 			to->to_sacks = cp + 2;
26665a53ca16SPaul Saab 			tcpstat.tcps_sack_rcv_blocks++;
26676d90faf3SPaul Saab 			break;
2668be2ac88cSJonathan Lemon 		default:
2669be2ac88cSJonathan Lemon 			continue;
2670df8bae1dSRodney W. Grimes 		}
2671df8bae1dSRodney W. Grimes 	}
2672df8bae1dSRodney W. Grimes }
2673df8bae1dSRodney W. Grimes 
2674df8bae1dSRodney W. Grimes /*
2675df8bae1dSRodney W. Grimes  * Pull out of band byte out of a segment so
2676df8bae1dSRodney W. Grimes  * it doesn't appear in the user's data queue.
2677df8bae1dSRodney W. Grimes  * It is still reflected in the segment length for
2678df8bae1dSRodney W. Grimes  * sequencing purposes.
2679df8bae1dSRodney W. Grimes  */
26800312fbe9SPoul-Henning Kamp static void
2681fb59c426SYoshinobu Inoue tcp_pulloutofband(so, th, m, off)
2682df8bae1dSRodney W. Grimes 	struct socket *so;
2683fb59c426SYoshinobu Inoue 	struct tcphdr *th;
2684df8bae1dSRodney W. Grimes 	register struct mbuf *m;
2685fb59c426SYoshinobu Inoue 	int off;		/* delayed to be droped hdrlen */
2686df8bae1dSRodney W. Grimes {
2687fb59c426SYoshinobu Inoue 	int cnt = off + th->th_urp - 1;
2688df8bae1dSRodney W. Grimes 
2689df8bae1dSRodney W. Grimes 	while (cnt >= 0) {
2690df8bae1dSRodney W. Grimes 		if (m->m_len > cnt) {
2691df8bae1dSRodney W. Grimes 			char *cp = mtod(m, caddr_t) + cnt;
2692df8bae1dSRodney W. Grimes 			struct tcpcb *tp = sototcpcb(so);
2693df8bae1dSRodney W. Grimes 
2694df8bae1dSRodney W. Grimes 			tp->t_iobc = *cp;
2695df8bae1dSRodney W. Grimes 			tp->t_oobflags |= TCPOOB_HAVEDATA;
2696df8bae1dSRodney W. Grimes 			bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1));
2697df8bae1dSRodney W. Grimes 			m->m_len--;
269869a34685SYoshinobu Inoue 			if (m->m_flags & M_PKTHDR)
269969a34685SYoshinobu Inoue 				m->m_pkthdr.len--;
2700df8bae1dSRodney W. Grimes 			return;
2701df8bae1dSRodney W. Grimes 		}
2702df8bae1dSRodney W. Grimes 		cnt -= m->m_len;
2703df8bae1dSRodney W. Grimes 		m = m->m_next;
2704df8bae1dSRodney W. Grimes 		if (m == 0)
2705df8bae1dSRodney W. Grimes 			break;
2706df8bae1dSRodney W. Grimes 	}
2707df8bae1dSRodney W. Grimes 	panic("tcp_pulloutofband");
2708df8bae1dSRodney W. Grimes }
2709df8bae1dSRodney W. Grimes 
2710df8bae1dSRodney W. Grimes /*
2711df8bae1dSRodney W. Grimes  * Collect new round-trip time estimate
2712df8bae1dSRodney W. Grimes  * and update averages and current timeout.
2713df8bae1dSRodney W. Grimes  */
27140312fbe9SPoul-Henning Kamp static void
2715df8bae1dSRodney W. Grimes tcp_xmit_timer(tp, rtt)
2716df8bae1dSRodney W. Grimes 	register struct tcpcb *tp;
27179b8b58e0SJonathan Lemon 	int rtt;
2718df8bae1dSRodney W. Grimes {
2719233e8c18SGarrett Wollman 	register int delta;
2720233e8c18SGarrett Wollman 
27212be3bf22SRobert Watson 	INP_LOCK_ASSERT(tp->t_inpcb);
27222be3bf22SRobert Watson 
2723233e8c18SGarrett Wollman 	tcpstat.tcps_rttupdated++;
2724233e8c18SGarrett Wollman 	tp->t_rttupdated++;
2725233e8c18SGarrett Wollman 	if (tp->t_srtt != 0) {
2726233e8c18SGarrett Wollman 		/*
2727233e8c18SGarrett Wollman 		 * srtt is stored as fixed point with 5 bits after the
2728233e8c18SGarrett Wollman 		 * binary point (i.e., scaled by 8).  The following magic
2729233e8c18SGarrett Wollman 		 * is equivalent to the smoothing algorithm in rfc793 with
2730233e8c18SGarrett Wollman 		 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
2731233e8c18SGarrett Wollman 		 * point).  Adjust rtt to origin 0.
2732233e8c18SGarrett Wollman 		 */
2733233e8c18SGarrett Wollman 		delta = ((rtt - 1) << TCP_DELTA_SHIFT)
2734233e8c18SGarrett Wollman 			- (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
2735233e8c18SGarrett Wollman 
2736233e8c18SGarrett Wollman 		if ((tp->t_srtt += delta) <= 0)
2737233e8c18SGarrett Wollman 			tp->t_srtt = 1;
2738233e8c18SGarrett Wollman 
2739233e8c18SGarrett Wollman 		/*
2740233e8c18SGarrett Wollman 		 * We accumulate a smoothed rtt variance (actually, a
2741233e8c18SGarrett Wollman 		 * smoothed mean difference), then set the retransmit
2742233e8c18SGarrett Wollman 		 * timer to smoothed rtt + 4 times the smoothed variance.
2743233e8c18SGarrett Wollman 		 * rttvar is stored as fixed point with 4 bits after the
2744233e8c18SGarrett Wollman 		 * binary point (scaled by 16).  The following is
2745233e8c18SGarrett Wollman 		 * equivalent to rfc793 smoothing with an alpha of .75
2746233e8c18SGarrett Wollman 		 * (rttvar = rttvar*3/4 + |delta| / 4).  This replaces
2747233e8c18SGarrett Wollman 		 * rfc793's wired-in beta.
2748233e8c18SGarrett Wollman 		 */
2749233e8c18SGarrett Wollman 		if (delta < 0)
2750233e8c18SGarrett Wollman 			delta = -delta;
2751233e8c18SGarrett Wollman 		delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
2752233e8c18SGarrett Wollman 		if ((tp->t_rttvar += delta) <= 0)
2753233e8c18SGarrett Wollman 			tp->t_rttvar = 1;
27541fcc99b5SMatthew Dillon 		if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
27551fcc99b5SMatthew Dillon 		    tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2756233e8c18SGarrett Wollman 	} else {
2757233e8c18SGarrett Wollman 		/*
2758233e8c18SGarrett Wollman 		 * No rtt measurement yet - use the unsmoothed rtt.
2759233e8c18SGarrett Wollman 		 * Set the variance to half the rtt (so our first
2760233e8c18SGarrett Wollman 		 * retransmit happens at 3*rtt).
2761233e8c18SGarrett Wollman 		 */
2762233e8c18SGarrett Wollman 		tp->t_srtt = rtt << TCP_RTT_SHIFT;
2763233e8c18SGarrett Wollman 		tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
27641fcc99b5SMatthew Dillon 		tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2765233e8c18SGarrett Wollman 	}
27669b8b58e0SJonathan Lemon 	tp->t_rtttime = 0;
2767df8bae1dSRodney W. Grimes 	tp->t_rxtshift = 0;
2768df8bae1dSRodney W. Grimes 
2769df8bae1dSRodney W. Grimes 	/*
2770df8bae1dSRodney W. Grimes 	 * the retransmit should happen at rtt + 4 * rttvar.
2771df8bae1dSRodney W. Grimes 	 * Because of the way we do the smoothing, srtt and rttvar
2772df8bae1dSRodney W. Grimes 	 * will each average +1/2 tick of bias.  When we compute
2773df8bae1dSRodney W. Grimes 	 * the retransmit timer, we want 1/2 tick of rounding and
2774df8bae1dSRodney W. Grimes 	 * 1 extra tick because of +-1/2 tick uncertainty in the
2775df8bae1dSRodney W. Grimes 	 * firing of the timer.  The bias will give us exactly the
2776df8bae1dSRodney W. Grimes 	 * 1.5 tick we need.  But, because the bias is
2777df8bae1dSRodney W. Grimes 	 * statistical, we have to test that we don't drop below
2778df8bae1dSRodney W. Grimes 	 * the minimum feasible timer (which is 2 ticks).
2779df8bae1dSRodney W. Grimes 	 */
2780233e8c18SGarrett Wollman 	TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
27819e2874b0SGarrett Wollman 		      max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
2782df8bae1dSRodney W. Grimes 
2783df8bae1dSRodney W. Grimes 	/*
2784df8bae1dSRodney W. Grimes 	 * We received an ack for a packet that wasn't retransmitted;
2785df8bae1dSRodney W. Grimes 	 * it is probably safe to discard any error indications we've
2786df8bae1dSRodney W. Grimes 	 * received recently.  This isn't quite right, but close enough
2787df8bae1dSRodney W. Grimes 	 * for now (a route might have failed after we sent a segment,
2788df8bae1dSRodney W. Grimes 	 * and the return path might not be symmetrical).
2789df8bae1dSRodney W. Grimes 	 */
2790df8bae1dSRodney W. Grimes 	tp->t_softerror = 0;
2791df8bae1dSRodney W. Grimes }
2792df8bae1dSRodney W. Grimes 
2793df8bae1dSRodney W. Grimes /*
2794df8bae1dSRodney W. Grimes  * Determine a reasonable value for maxseg size.
2795df8bae1dSRodney W. Grimes  * If the route is known, check route for mtu.
2796df8bae1dSRodney W. Grimes  * If none, use an mss that can be handled on the outgoing
2797df8bae1dSRodney W. Grimes  * interface without forcing IP to fragment; if bigger than
2798df8bae1dSRodney W. Grimes  * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
2799df8bae1dSRodney W. Grimes  * to utilize large mbufs.  If no route is found, route has no mtu,
2800df8bae1dSRodney W. Grimes  * or the destination isn't local, use a default, hopefully conservative
2801df8bae1dSRodney W. Grimes  * size (usually 512 or the default IP max size, but no more than the mtu
2802df8bae1dSRodney W. Grimes  * of the interface), as we can't discover anything about intervening
2803df8bae1dSRodney W. Grimes  * gateways or networks.  We also initialize the congestion/slow start
2804df8bae1dSRodney W. Grimes  * window to be a single segment if the destination isn't local.
2805df8bae1dSRodney W. Grimes  * While looking at the routing entry, we also initialize other path-dependent
2806df8bae1dSRodney W. Grimes  * parameters from pre-set or cached values in the routing entry.
2807a0292f23SGarrett Wollman  *
2808a0292f23SGarrett Wollman  * Also take into account the space needed for options that we
2809a0292f23SGarrett Wollman  * send regularly.  Make maxseg shorter by that amount to assure
2810a0292f23SGarrett Wollman  * that we can send maxseg amount of data even when the options
2811a0292f23SGarrett Wollman  * are present.  Store the upper limit of the length of options plus
2812a0292f23SGarrett Wollman  * data in maxopd.
2813a0292f23SGarrett Wollman  *
2814a0292f23SGarrett Wollman  *
2815a0292f23SGarrett Wollman  * In case of T/TCP, we call this routine during implicit connection
2816a0292f23SGarrett Wollman  * setup as well (offer = -1), to initialize maxseg from the cached
2817a0292f23SGarrett Wollman  * MSS of our peer.
281897d8d152SAndre Oppermann  *
281997d8d152SAndre Oppermann  * NOTE that this routine is only called when we process an incoming
282097d8d152SAndre Oppermann  * segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt().
2821df8bae1dSRodney W. Grimes  */
2822a0292f23SGarrett Wollman void
2823df8bae1dSRodney W. Grimes tcp_mss(tp, offer)
2824a0292f23SGarrett Wollman 	struct tcpcb *tp;
2825a0292f23SGarrett Wollman 	int offer;
2826df8bae1dSRodney W. Grimes {
282797d8d152SAndre Oppermann 	int rtt, mss;
2828df8bae1dSRodney W. Grimes 	u_long bufsize;
282997d8d152SAndre Oppermann 	u_long maxmtu;
2830c068736aSJeffrey Hsu 	struct inpcb *inp = tp->t_inpcb;
2831df8bae1dSRodney W. Grimes 	struct socket *so;
283297d8d152SAndre Oppermann 	struct hc_metrics_lite metrics;
2833a0292f23SGarrett Wollman 	int origoffer = offer;
2834fb59c426SYoshinobu Inoue #ifdef INET6
2835c068736aSJeffrey Hsu 	int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
2836c068736aSJeffrey Hsu 	size_t min_protoh = isipv6 ?
2837c068736aSJeffrey Hsu 			    sizeof (struct ip6_hdr) + sizeof (struct tcphdr) :
2838c068736aSJeffrey Hsu 			    sizeof (struct tcpiphdr);
2839c068736aSJeffrey Hsu #else
2840c068736aSJeffrey Hsu 	const size_t min_protoh = sizeof(struct tcpiphdr);
2841fb59c426SYoshinobu Inoue #endif
2842df8bae1dSRodney W. Grimes 
284397d8d152SAndre Oppermann 	/* initialize */
284497d8d152SAndre Oppermann #ifdef INET6
284597d8d152SAndre Oppermann 	if (isipv6) {
284697d8d152SAndre Oppermann 		maxmtu = tcp_maxmtu6(&inp->inp_inc);
284797d8d152SAndre Oppermann 		tp->t_maxopd = tp->t_maxseg = tcp_v6mssdflt;
284897d8d152SAndre Oppermann 	} else
284997d8d152SAndre Oppermann #endif
285097d8d152SAndre Oppermann 	{
285197d8d152SAndre Oppermann 		maxmtu = tcp_maxmtu(&inp->inp_inc);
285297d8d152SAndre Oppermann 		tp->t_maxopd = tp->t_maxseg = tcp_mssdflt;
2853df8bae1dSRodney W. Grimes 	}
2854df8bae1dSRodney W. Grimes 	so = inp->inp_socket;
2855df8bae1dSRodney W. Grimes 
285697d8d152SAndre Oppermann 	/*
28572d166c02SAndre Oppermann 	 * no route to sender, stay with default mss and return
285897d8d152SAndre Oppermann 	 */
285997d8d152SAndre Oppermann 	if (maxmtu == 0)
286097d8d152SAndre Oppermann 		return;
286197d8d152SAndre Oppermann 
286297d8d152SAndre Oppermann 	/* what have we got? */
286397d8d152SAndre Oppermann 	switch (offer) {
286497d8d152SAndre Oppermann 		case 0:
286597d8d152SAndre Oppermann 			/*
286697d8d152SAndre Oppermann 			 * Offer == 0 means that there was no MSS on the SYN
286797d8d152SAndre Oppermann 			 * segment, in this case we use tcp_mssdflt.
286897d8d152SAndre Oppermann 			 */
286997d8d152SAndre Oppermann 			offer =
287097d8d152SAndre Oppermann #ifdef INET6
287197d8d152SAndre Oppermann 				isipv6 ? tcp_v6mssdflt :
287297d8d152SAndre Oppermann #endif
287397d8d152SAndre Oppermann 				tcp_mssdflt;
287497d8d152SAndre Oppermann 			break;
287597d8d152SAndre Oppermann 
287697d8d152SAndre Oppermann 		case -1:
2877a0292f23SGarrett Wollman 			/*
2878c94c54e4SAndre Oppermann 			 * Offer == -1 means that we didn't receive SYN yet.
2879a0292f23SGarrett Wollman 			 */
288097d8d152SAndre Oppermann 			/* FALLTHROUGH */
288197d8d152SAndre Oppermann 
288297d8d152SAndre Oppermann 		default:
2883a0292f23SGarrett Wollman 			/*
288453369ac9SAndre Oppermann 			 * Prevent DoS attack with too small MSS. Round up
288553369ac9SAndre Oppermann 			 * to at least minmss.
288653369ac9SAndre Oppermann 			 */
288753369ac9SAndre Oppermann 			offer = max(offer, tcp_minmss);
288853369ac9SAndre Oppermann 			/*
2889a0292f23SGarrett Wollman 			 * Sanity check: make sure that maxopd will be large
289097d8d152SAndre Oppermann 			 * enough to allow some data on segments even if the
2891a0292f23SGarrett Wollman 			 * all the option space is used (40bytes).  Otherwise
2892a0292f23SGarrett Wollman 			 * funny things may happen in tcp_output.
2893a0292f23SGarrett Wollman 			 */
2894a0292f23SGarrett Wollman 			offer = max(offer, 64);
289597d8d152SAndre Oppermann 	}
2896a0292f23SGarrett Wollman 
2897df8bae1dSRodney W. Grimes 	/*
289897d8d152SAndre Oppermann 	 * rmx information is now retrieved from tcp_hostcache
2899df8bae1dSRodney W. Grimes 	 */
290097d8d152SAndre Oppermann 	tcp_hc_get(&inp->inp_inc, &metrics);
290197d8d152SAndre Oppermann 
2902df8bae1dSRodney W. Grimes 	/*
290397d8d152SAndre Oppermann 	 * if there's a discovered mtu int tcp hostcache, use it
2904fb59c426SYoshinobu Inoue 	 * else, use the link mtu.
2905df8bae1dSRodney W. Grimes 	 */
290697d8d152SAndre Oppermann 	if (metrics.rmx_mtu)
29072d166c02SAndre Oppermann 		mss = min(metrics.rmx_mtu, maxmtu) - min_protoh;
2908c068736aSJeffrey Hsu 	else {
290931b3783cSHajimu UMEMOTO #ifdef INET6
2910fb59c426SYoshinobu Inoue 		if (isipv6) {
291197d8d152SAndre Oppermann 			mss = maxmtu - min_protoh;
291297d8d152SAndre Oppermann 			if (!path_mtu_discovery &&
291397d8d152SAndre Oppermann 			    !in6_localaddr(&inp->in6p_faddr))
2914fb59c426SYoshinobu Inoue 				mss = min(mss, tcp_v6mssdflt);
2915b3399803SHajimu UMEMOTO 		} else
2916b3399803SHajimu UMEMOTO #endif
291797d8d152SAndre Oppermann 		{
291897d8d152SAndre Oppermann 			mss = maxmtu - min_protoh;
291997d8d152SAndre Oppermann 			if (!path_mtu_discovery &&
292097d8d152SAndre Oppermann 			    !in_localaddr(inp->inp_faddr))
2921a0292f23SGarrett Wollman 				mss = min(mss, tcp_mssdflt);
2922a0292f23SGarrett Wollman 		}
292397d8d152SAndre Oppermann 	}
2924a0292f23SGarrett Wollman 	mss = min(mss, offer);
292597d8d152SAndre Oppermann 
2926a0292f23SGarrett Wollman 	/*
2927a0292f23SGarrett Wollman 	 * maxopd stores the maximum length of data AND options
2928a0292f23SGarrett Wollman 	 * in a segment; maxseg is the amount of data in a normal
2929a0292f23SGarrett Wollman 	 * segment.  We need to store this value (maxopd) apart
2930a0292f23SGarrett Wollman 	 * from maxseg, because now every segment carries options
2931a0292f23SGarrett Wollman 	 * and thus we normally have somewhat less data in segments.
2932a0292f23SGarrett Wollman 	 */
2933a0292f23SGarrett Wollman 	tp->t_maxopd = mss;
2934a0292f23SGarrett Wollman 
2935a0292f23SGarrett Wollman 	/*
2936c94c54e4SAndre Oppermann 	 * origoffer==-1 indicates, that no segments were received yet.
2937c94c54e4SAndre Oppermann 	 * In this case we just guess.
2938a0292f23SGarrett Wollman 	 */
2939a0292f23SGarrett Wollman 	if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
2940a0292f23SGarrett Wollman 	    (origoffer == -1 ||
2941a0292f23SGarrett Wollman 	     (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
2942a0292f23SGarrett Wollman 		mss -= TCPOLEN_TSTAMP_APPA;
294397d8d152SAndre Oppermann 	tp->t_maxseg = mss;
2944a0292f23SGarrett Wollman 
2945df8bae1dSRodney W. Grimes #if	(MCLBYTES & (MCLBYTES - 1)) == 0
2946df8bae1dSRodney W. Grimes 		if (mss > MCLBYTES)
2947df8bae1dSRodney W. Grimes 			mss &= ~(MCLBYTES-1);
2948df8bae1dSRodney W. Grimes #else
2949df8bae1dSRodney W. Grimes 		if (mss > MCLBYTES)
2950df8bae1dSRodney W. Grimes 			mss = mss / MCLBYTES * MCLBYTES;
2951df8bae1dSRodney W. Grimes #endif
295297d8d152SAndre Oppermann 	tp->t_maxseg = mss;
295397d8d152SAndre Oppermann 
2954df8bae1dSRodney W. Grimes 	/*
295597d8d152SAndre Oppermann 	 * If there's a pipesize, change the socket buffer to that size,
295697d8d152SAndre Oppermann 	 * don't change if sb_hiwat is different than default (then it
295797d8d152SAndre Oppermann 	 * has been changed on purpose with setsockopt).
295897d8d152SAndre Oppermann 	 * Make the socket buffers an integral number of mss units;
295997d8d152SAndre Oppermann 	 * if the mss is larger than the socket buffer, decrease the mss.
2960df8bae1dSRodney W. Grimes 	 */
29613f11a2f3SRobert Watson 	SOCKBUF_LOCK(&so->so_snd);
296297d8d152SAndre Oppermann 	if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe)
296397d8d152SAndre Oppermann 		bufsize = metrics.rmx_sendpipe;
296497d8d152SAndre Oppermann 	else
2965df8bae1dSRodney W. Grimes 		bufsize = so->so_snd.sb_hiwat;
2966df8bae1dSRodney W. Grimes 	if (bufsize < mss)
2967df8bae1dSRodney W. Grimes 		mss = bufsize;
2968df8bae1dSRodney W. Grimes 	else {
2969df8bae1dSRodney W. Grimes 		bufsize = roundup(bufsize, mss);
2970df8bae1dSRodney W. Grimes 		if (bufsize > sb_max)
2971df8bae1dSRodney W. Grimes 			bufsize = sb_max;
297288c39af3SRuslan Ermilov 		if (bufsize > so->so_snd.sb_hiwat)
29733f11a2f3SRobert Watson 			(void)sbreserve_locked(&so->so_snd, bufsize, so, NULL);
2974df8bae1dSRodney W. Grimes 	}
29753f11a2f3SRobert Watson 	SOCKBUF_UNLOCK(&so->so_snd);
2976df8bae1dSRodney W. Grimes 	tp->t_maxseg = mss;
2977df8bae1dSRodney W. Grimes 
29783f11a2f3SRobert Watson 	SOCKBUF_LOCK(&so->so_rcv);
297997d8d152SAndre Oppermann 	if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe)
298097d8d152SAndre Oppermann 		bufsize = metrics.rmx_recvpipe;
298197d8d152SAndre Oppermann 	else
2982df8bae1dSRodney W. Grimes 		bufsize = so->so_rcv.sb_hiwat;
2983df8bae1dSRodney W. Grimes 	if (bufsize > mss) {
2984df8bae1dSRodney W. Grimes 		bufsize = roundup(bufsize, mss);
2985df8bae1dSRodney W. Grimes 		if (bufsize > sb_max)
2986df8bae1dSRodney W. Grimes 			bufsize = sb_max;
298788c39af3SRuslan Ermilov 		if (bufsize > so->so_rcv.sb_hiwat)
29883f11a2f3SRobert Watson 			(void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL);
2989df8bae1dSRodney W. Grimes 	}
29903f11a2f3SRobert Watson 	SOCKBUF_UNLOCK(&so->so_rcv);
2991a0292f23SGarrett Wollman 	/*
299297d8d152SAndre Oppermann 	 * While we're here, check the others too
2993a0292f23SGarrett Wollman 	 */
299497d8d152SAndre Oppermann 	if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) {
299597d8d152SAndre Oppermann 		tp->t_srtt = rtt;
299697d8d152SAndre Oppermann 		tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
299797d8d152SAndre Oppermann 		tcpstat.tcps_usedrtt++;
299897d8d152SAndre Oppermann 		if (metrics.rmx_rttvar) {
299997d8d152SAndre Oppermann 			tp->t_rttvar = metrics.rmx_rttvar;
300097d8d152SAndre Oppermann 			tcpstat.tcps_usedrttvar++;
300197d8d152SAndre Oppermann 		} else {
300297d8d152SAndre Oppermann 			/* default variation is +- 1 rtt */
300397d8d152SAndre Oppermann 			tp->t_rttvar =
300497d8d152SAndre Oppermann 			    tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
300597d8d152SAndre Oppermann 		}
300697d8d152SAndre Oppermann 		TCPT_RANGESET(tp->t_rxtcur,
300797d8d152SAndre Oppermann 			      ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
300897d8d152SAndre Oppermann 			      tp->t_rttmin, TCPTV_REXMTMAX);
300997d8d152SAndre Oppermann 	}
301097d8d152SAndre Oppermann 	if (metrics.rmx_ssthresh) {
3011df8bae1dSRodney W. Grimes 		/*
3012df8bae1dSRodney W. Grimes 		 * There's some sort of gateway or interface
3013df8bae1dSRodney W. Grimes 		 * buffer limit on the path.  Use this to set
3014df8bae1dSRodney W. Grimes 		 * the slow start threshhold, but set the
3015df8bae1dSRodney W. Grimes 		 * threshold to no less than 2*mss.
3016df8bae1dSRodney W. Grimes 		 */
301797d8d152SAndre Oppermann 		tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh);
3018dd224982SGarrett Wollman 		tcpstat.tcps_usedssthresh++;
3019df8bae1dSRodney W. Grimes 	}
302097d8d152SAndre Oppermann 	if (metrics.rmx_bandwidth)
302197d8d152SAndre Oppermann 		tp->snd_bandwidth = metrics.rmx_bandwidth;
302297d8d152SAndre Oppermann 
302397d8d152SAndre Oppermann 	/*
302497d8d152SAndre Oppermann 	 * Set the slow-start flight size depending on whether this
302597d8d152SAndre Oppermann 	 * is a local network or not.
302697d8d152SAndre Oppermann 	 *
302797d8d152SAndre Oppermann 	 * Extend this so we cache the cwnd too and retrieve it here.
302897d8d152SAndre Oppermann 	 * Make cwnd even bigger than RFC3390 suggests but only if we
302997d8d152SAndre Oppermann 	 * have previous experience with the remote host. Be careful
303097d8d152SAndre Oppermann 	 * not make cwnd bigger than remote receive window or our own
303197d8d152SAndre Oppermann 	 * send socket buffer. Maybe put some additional upper bound
303297d8d152SAndre Oppermann 	 * on the retrieved cwnd. Should do incremental updates to
303397d8d152SAndre Oppermann 	 * hostcache when cwnd collapses so next connection doesn't
303497d8d152SAndre Oppermann 	 * overloads the path again.
303597d8d152SAndre Oppermann 	 *
303697d8d152SAndre Oppermann 	 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost.
303797d8d152SAndre Oppermann 	 * We currently check only in syncache_socket for that.
303897d8d152SAndre Oppermann 	 */
303997d8d152SAndre Oppermann #define TCP_METRICS_CWND
304097d8d152SAndre Oppermann #ifdef TCP_METRICS_CWND
304197d8d152SAndre Oppermann 	if (metrics.rmx_cwnd)
304297d8d152SAndre Oppermann 		tp->snd_cwnd = max(mss,
304397d8d152SAndre Oppermann 				min(metrics.rmx_cwnd / 2,
304497d8d152SAndre Oppermann 				 min(tp->snd_wnd, so->so_snd.sb_hiwat)));
304597d8d152SAndre Oppermann 	else
304697d8d152SAndre Oppermann #endif
304797d8d152SAndre Oppermann 	if (tcp_do_rfc3390)
304897d8d152SAndre Oppermann 		tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380));
304997d8d152SAndre Oppermann #ifdef INET6
305097d8d152SAndre Oppermann 	else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
305197d8d152SAndre Oppermann 		 (!isipv6 && in_localaddr(inp->inp_faddr)))
3052943ae302SAndre Oppermann #else
3053943ae302SAndre Oppermann 	else if (in_localaddr(inp->inp_faddr))
305497d8d152SAndre Oppermann #endif
3055943ae302SAndre Oppermann 		tp->snd_cwnd = mss * ss_fltsz_local;
305697d8d152SAndre Oppermann 	else
305797d8d152SAndre Oppermann 		tp->snd_cwnd = mss * ss_fltsz;
3058a0292f23SGarrett Wollman }
3059a0292f23SGarrett Wollman 
3060a0292f23SGarrett Wollman /*
3061a0292f23SGarrett Wollman  * Determine the MSS option to send on an outgoing SYN.
3062a0292f23SGarrett Wollman  */
3063a0292f23SGarrett Wollman int
306497d8d152SAndre Oppermann tcp_mssopt(inc)
306597d8d152SAndre Oppermann 	struct in_conninfo *inc;
3066a0292f23SGarrett Wollman {
306797d8d152SAndre Oppermann 	int mss = 0;
306897d8d152SAndre Oppermann 	u_long maxmtu = 0;
306997d8d152SAndre Oppermann 	u_long thcmtu = 0;
307097d8d152SAndre Oppermann 	size_t min_protoh;
3071fb59c426SYoshinobu Inoue #ifdef INET6
307297d8d152SAndre Oppermann 	int isipv6 = inc->inc_isipv6 ? 1 : 0;
3073fb59c426SYoshinobu Inoue #endif
3074a0292f23SGarrett Wollman 
307597d8d152SAndre Oppermann 	KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer"));
3076a0292f23SGarrett Wollman 
307731b3783cSHajimu UMEMOTO #ifdef INET6
307897d8d152SAndre Oppermann 	if (isipv6) {
307997d8d152SAndre Oppermann 		mss = tcp_v6mssdflt;
308097d8d152SAndre Oppermann 		maxmtu = tcp_maxmtu6(inc);
308197d8d152SAndre Oppermann 		thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */
308297d8d152SAndre Oppermann 		min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
308397d8d152SAndre Oppermann 	} else
308431b3783cSHajimu UMEMOTO #endif
308597d8d152SAndre Oppermann 	{
308697d8d152SAndre Oppermann 		mss = tcp_mssdflt;
308797d8d152SAndre Oppermann 		maxmtu = tcp_maxmtu(inc);
308897d8d152SAndre Oppermann 		thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */
308997d8d152SAndre Oppermann 		min_protoh = sizeof(struct tcpiphdr);
309097d8d152SAndre Oppermann 	}
309197d8d152SAndre Oppermann 	if (maxmtu && thcmtu)
309297d8d152SAndre Oppermann 		mss = min(maxmtu, thcmtu) - min_protoh;
309397d8d152SAndre Oppermann 	else if (maxmtu || thcmtu)
309497d8d152SAndre Oppermann 		mss = max(maxmtu, thcmtu) - min_protoh;
309597d8d152SAndre Oppermann 
309697d8d152SAndre Oppermann 	return (mss);
3097df8bae1dSRodney W. Grimes }
309846f58482SJonathan Lemon 
309946f58482SJonathan Lemon 
310046f58482SJonathan Lemon /*
3101c068736aSJeffrey Hsu  * On a partial ack arrives, force the retransmission of the
3102c068736aSJeffrey Hsu  * next unacknowledged segment.  Do not clear tp->t_dupacks.
3103c068736aSJeffrey Hsu  * By setting snd_nxt to ti_ack, this forces retransmission timer to
3104c068736aSJeffrey Hsu  * be started again.
310546f58482SJonathan Lemon  */
3106c068736aSJeffrey Hsu static void
3107c068736aSJeffrey Hsu tcp_newreno_partial_ack(tp, th)
310846f58482SJonathan Lemon 	struct tcpcb *tp;
310946f58482SJonathan Lemon 	struct tcphdr *th;
311046f58482SJonathan Lemon {
311146f58482SJonathan Lemon 	tcp_seq onxt = tp->snd_nxt;
311246f58482SJonathan Lemon 	u_long  ocwnd = tp->snd_cwnd;
311346f58482SJonathan Lemon 
311446f58482SJonathan Lemon 	callout_stop(tp->tt_rexmt);
311546f58482SJonathan Lemon 	tp->t_rtttime = 0;
311646f58482SJonathan Lemon 	tp->snd_nxt = th->th_ack;
31176b2a5f92SJayanth Vijayaraghavan 	/*
3118c068736aSJeffrey Hsu 	 * Set snd_cwnd to one segment beyond acknowledged offset.
3119c068736aSJeffrey Hsu 	 * (tp->snd_una has not yet been updated when this function is called.)
31206b2a5f92SJayanth Vijayaraghavan 	 */
31216b2a5f92SJayanth Vijayaraghavan 	tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una);
3122a84db8f4SMatthew Dillon 	tp->t_flags |= TF_ACKNOW;
31236b2a5f92SJayanth Vijayaraghavan 	(void) tcp_output(tp);
312446f58482SJonathan Lemon 	tp->snd_cwnd = ocwnd;
312546f58482SJonathan Lemon 	if (SEQ_GT(onxt, tp->snd_nxt))
312646f58482SJonathan Lemon 		tp->snd_nxt = onxt;
312746f58482SJonathan Lemon 	/*
312846f58482SJonathan Lemon 	 * Partial window deflation.  Relies on fact that tp->snd_una
312946f58482SJonathan Lemon 	 * not updated yet.
313046f58482SJonathan Lemon 	 */
3131d7587117SPaul Saab 	if (tp->snd_cwnd > th->th_ack - tp->snd_una)
3132d7587117SPaul Saab 		tp->snd_cwnd -= th->th_ack - tp->snd_una;
3133d7587117SPaul Saab 	else
3134d7587117SPaul Saab 		tp->snd_cwnd = 0;
3135d7587117SPaul Saab 	tp->snd_cwnd += tp->t_maxseg;
313646f58482SJonathan Lemon }
3137340c35deSJonathan Lemon 
3138340c35deSJonathan Lemon /*
3139340c35deSJonathan Lemon  * Returns 1 if the TIME_WAIT state was killed and we should start over,
3140340c35deSJonathan Lemon  * looking for a pcb in the listen state.  Returns 0 otherwise.
3141340c35deSJonathan Lemon  */
3142340c35deSJonathan Lemon static int
3143340c35deSJonathan Lemon tcp_timewait(tw, to, th, m, tlen)
3144340c35deSJonathan Lemon 	struct tcptw *tw;
3145340c35deSJonathan Lemon 	struct tcpopt *to;
3146340c35deSJonathan Lemon 	struct tcphdr *th;
3147340c35deSJonathan Lemon 	struct mbuf *m;
3148340c35deSJonathan Lemon 	int tlen;
3149340c35deSJonathan Lemon {
3150340c35deSJonathan Lemon 	int thflags;
3151340c35deSJonathan Lemon 	tcp_seq seq;
3152340c35deSJonathan Lemon #ifdef INET6
3153340c35deSJonathan Lemon 	int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
3154340c35deSJonathan Lemon #else
3155340c35deSJonathan Lemon 	const int isipv6 = 0;
3156340c35deSJonathan Lemon #endif
3157340c35deSJonathan Lemon 
3158cce83ffbSRobert Watson 	/* tcbinfo lock required for tcp_twclose(), tcp_2msl_reset. */
3159cce83ffbSRobert Watson 	INP_INFO_WLOCK_ASSERT(&tcbinfo);
3160cce83ffbSRobert Watson 	INP_LOCK_ASSERT(tw->tw_inpcb);
3161cce83ffbSRobert Watson 
3162340c35deSJonathan Lemon 	thflags = th->th_flags;
3163340c35deSJonathan Lemon 
3164340c35deSJonathan Lemon 	/*
3165340c35deSJonathan Lemon 	 * NOTE: for FIN_WAIT_2 (to be added later),
3166340c35deSJonathan Lemon 	 * must validate sequence number before accepting RST
3167340c35deSJonathan Lemon 	 */
3168340c35deSJonathan Lemon 
3169340c35deSJonathan Lemon 	/*
3170340c35deSJonathan Lemon 	 * If the segment contains RST:
3171340c35deSJonathan Lemon 	 *	Drop the segment - see Stevens, vol. 2, p. 964 and
3172340c35deSJonathan Lemon 	 *      RFC 1337.
3173340c35deSJonathan Lemon 	 */
3174340c35deSJonathan Lemon 	if (thflags & TH_RST)
3175340c35deSJonathan Lemon 		goto drop;
3176340c35deSJonathan Lemon 
3177340c35deSJonathan Lemon #if 0
3178340c35deSJonathan Lemon /* PAWS not needed at the moment */
3179340c35deSJonathan Lemon 	/*
3180340c35deSJonathan Lemon 	 * RFC 1323 PAWS: If we have a timestamp reply on this segment
3181340c35deSJonathan Lemon 	 * and it's less than ts_recent, drop it.
3182340c35deSJonathan Lemon 	 */
3183340c35deSJonathan Lemon 	if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
3184340c35deSJonathan Lemon 	    TSTMP_LT(to.to_tsval, tp->ts_recent)) {
3185340c35deSJonathan Lemon 		if ((thflags & TH_ACK) == 0)
3186340c35deSJonathan Lemon 			goto drop;
3187340c35deSJonathan Lemon 		goto ack;
3188340c35deSJonathan Lemon 	}
3189340c35deSJonathan Lemon 	/*
3190340c35deSJonathan Lemon 	 * ts_recent is never updated because we never accept new segments.
3191340c35deSJonathan Lemon 	 */
3192340c35deSJonathan Lemon #endif
3193340c35deSJonathan Lemon 
3194340c35deSJonathan Lemon 	/*
3195340c35deSJonathan Lemon 	 * If a new connection request is received
3196340c35deSJonathan Lemon 	 * while in TIME_WAIT, drop the old connection
3197340c35deSJonathan Lemon 	 * and start over if the sequence numbers
3198340c35deSJonathan Lemon 	 * are above the previous ones.
3199340c35deSJonathan Lemon 	 */
3200340c35deSJonathan Lemon 	if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) {
3201607b0b0cSJonathan Lemon 		(void) tcp_twclose(tw, 0);
3202340c35deSJonathan Lemon 		return (1);
3203340c35deSJonathan Lemon 	}
3204340c35deSJonathan Lemon 
3205340c35deSJonathan Lemon 	/*
3206340c35deSJonathan Lemon 	 * Drop the the segment if it does not contain an ACK.
3207340c35deSJonathan Lemon 	 */
3208340c35deSJonathan Lemon 	if ((thflags & TH_ACK) == 0)
3209340c35deSJonathan Lemon 		goto drop;
3210340c35deSJonathan Lemon 
3211340c35deSJonathan Lemon 	/*
3212340c35deSJonathan Lemon 	 * Reset the 2MSL timer if this is a duplicate FIN.
3213340c35deSJonathan Lemon 	 */
3214340c35deSJonathan Lemon 	if (thflags & TH_FIN) {
3215340c35deSJonathan Lemon 		seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0);
3216340c35deSJonathan Lemon 		if (seq + 1 == tw->rcv_nxt)
3217607b0b0cSJonathan Lemon 			tcp_timer_2msl_reset(tw, 2 * tcp_msl);
3218340c35deSJonathan Lemon 	}
3219340c35deSJonathan Lemon 
3220340c35deSJonathan Lemon 	/*
3221272c5dfeSJonathan Lemon 	 * Acknowledge the segment if it has data or is not a duplicate ACK.
3222340c35deSJonathan Lemon 	 */
3223272c5dfeSJonathan Lemon 	if (thflags != TH_ACK || tlen != 0 ||
3224272c5dfeSJonathan Lemon 	    th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt)
3225a7b6a14aSRobert Watson 		tcp_twrespond(tw, TH_ACK);
3226340c35deSJonathan Lemon 	goto drop;
3227340c35deSJonathan Lemon 
3228340c35deSJonathan Lemon 	/*
3229340c35deSJonathan Lemon 	 * Generate a RST, dropping incoming segment.
3230340c35deSJonathan Lemon 	 * Make ACK acceptable to originator of segment.
3231340c35deSJonathan Lemon 	 * Don't bother to respond if destination was broadcast/multicast.
3232340c35deSJonathan Lemon 	 */
3233340c35deSJonathan Lemon 	if (m->m_flags & (M_BCAST|M_MCAST))
3234340c35deSJonathan Lemon 		goto drop;
3235340c35deSJonathan Lemon 	if (isipv6) {
3236340c35deSJonathan Lemon 		struct ip6_hdr *ip6;
3237340c35deSJonathan Lemon 
3238340c35deSJonathan Lemon 		/* IPv6 anycast check is done at tcp6_input() */
3239340c35deSJonathan Lemon 		ip6 = mtod(m, struct ip6_hdr *);
3240340c35deSJonathan Lemon 		if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
3241340c35deSJonathan Lemon 		    IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
3242340c35deSJonathan Lemon 			goto drop;
3243340c35deSJonathan Lemon 	} else {
3244340c35deSJonathan Lemon 		struct ip *ip;
3245340c35deSJonathan Lemon 
3246340c35deSJonathan Lemon 		ip = mtod(m, struct ip *);
3247340c35deSJonathan Lemon 		if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
3248340c35deSJonathan Lemon 		    IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
3249340c35deSJonathan Lemon 		    ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
3250340c35deSJonathan Lemon 		    in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
3251340c35deSJonathan Lemon 			goto drop;
3252340c35deSJonathan Lemon 	}
3253340c35deSJonathan Lemon 	if (thflags & TH_ACK) {
3254340c35deSJonathan Lemon 		tcp_respond(NULL,
3255340c35deSJonathan Lemon 		    mtod(m, void *), th, m, 0, th->th_ack, TH_RST);
3256340c35deSJonathan Lemon 	} else {
3257340c35deSJonathan Lemon 		seq = th->th_seq + (thflags & TH_SYN ? 1 : 0);
3258340c35deSJonathan Lemon 		tcp_respond(NULL,
3259340c35deSJonathan Lemon 		    mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK);
3260340c35deSJonathan Lemon 	}
3261340c35deSJonathan Lemon 	INP_UNLOCK(tw->tw_inpcb);
3262340c35deSJonathan Lemon 	return (0);
3263340c35deSJonathan Lemon 
3264340c35deSJonathan Lemon drop:
3265340c35deSJonathan Lemon 	INP_UNLOCK(tw->tw_inpcb);
3266340c35deSJonathan Lemon 	m_freem(m);
3267340c35deSJonathan Lemon 	return (0);
3268340c35deSJonathan Lemon }
3269