xref: /freebsd/sys/netinet/tcp.h (revision 74fe6c29fb7eef3418d7919dcd41dc1a04a982a1)
1 /*-
2  * SPDX-License-Identifier: BSD-3-Clause
3  *
4  * Copyright (c) 1982, 1986, 1993
5  *	The Regents of the University of California.  All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  * 3. Neither the name of the University nor the names of its contributors
16  *    may be used to endorse or promote products derived from this software
17  *    without specific prior written permission.
18  *
19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29  * SUCH DAMAGE.
30  *
31  *	@(#)tcp.h	8.1 (Berkeley) 6/10/93
32  * $FreeBSD$
33  */
34 
35 #ifndef _NETINET_TCP_H_
36 #define _NETINET_TCP_H_
37 
38 #include <sys/cdefs.h>
39 #include <sys/types.h>
40 
41 #if __BSD_VISIBLE
42 
43 typedef	u_int32_t tcp_seq;
44 
45 #define tcp6_seq	tcp_seq	/* for KAME src sync over BSD*'s */
46 #define tcp6hdr		tcphdr	/* for KAME src sync over BSD*'s */
47 
48 /*
49  * TCP header.
50  * Per RFC 793, September, 1981.
51  */
52 struct tcphdr {
53 	u_short	th_sport;		/* source port */
54 	u_short	th_dport;		/* destination port */
55 	tcp_seq	th_seq;			/* sequence number */
56 	tcp_seq	th_ack;			/* acknowledgement number */
57 #if BYTE_ORDER == LITTLE_ENDIAN
58 	u_char	th_x2:4,		/* (unused) */
59 		th_off:4;		/* data offset */
60 #endif
61 #if BYTE_ORDER == BIG_ENDIAN
62 	u_char	th_off:4,		/* data offset */
63 		th_x2:4;		/* (unused) */
64 #endif
65 	u_char	th_flags;
66 #define	TH_FIN	0x01
67 #define	TH_SYN	0x02
68 #define	TH_RST	0x04
69 #define	TH_PUSH	0x08
70 #define	TH_ACK	0x10
71 #define	TH_URG	0x20
72 #define	TH_ECE	0x40
73 #define	TH_CWR	0x80
74 #define	TH_FLAGS	(TH_FIN|TH_SYN|TH_RST|TH_PUSH|TH_ACK|TH_URG|TH_ECE|TH_CWR)
75 #define	PRINT_TH_FLAGS	"\20\1FIN\2SYN\3RST\4PUSH\5ACK\6URG\7ECE\10CWR"
76 
77 	u_short	th_win;			/* window */
78 	u_short	th_sum;			/* checksum */
79 	u_short	th_urp;			/* urgent pointer */
80 };
81 
82 #define	TCPOPT_EOL		0
83 #define	   TCPOLEN_EOL			1
84 #define	TCPOPT_PAD		0		/* padding after EOL */
85 #define	   TCPOLEN_PAD			1
86 #define	TCPOPT_NOP		1
87 #define	   TCPOLEN_NOP			1
88 #define	TCPOPT_MAXSEG		2
89 #define    TCPOLEN_MAXSEG		4
90 #define TCPOPT_WINDOW		3
91 #define    TCPOLEN_WINDOW		3
92 #define TCPOPT_SACK_PERMITTED	4
93 #define    TCPOLEN_SACK_PERMITTED	2
94 #define TCPOPT_SACK		5
95 #define	   TCPOLEN_SACKHDR		2
96 #define    TCPOLEN_SACK			8	/* 2*sizeof(tcp_seq) */
97 #define TCPOPT_TIMESTAMP	8
98 #define    TCPOLEN_TIMESTAMP		10
99 #define    TCPOLEN_TSTAMP_APPA		(TCPOLEN_TIMESTAMP+2) /* appendix A */
100 #define	TCPOPT_SIGNATURE	19		/* Keyed MD5: RFC 2385 */
101 #define	   TCPOLEN_SIGNATURE		18
102 #define	TCPOPT_FAST_OPEN	34
103 #define	   TCPOLEN_FAST_OPEN_EMPTY	2
104 
105 /* Miscellaneous constants */
106 #define	MAX_SACK_BLKS	6	/* Max # SACK blocks stored at receiver side */
107 #define	TCP_MAX_SACK	4	/* MAX # SACKs sent in any segment */
108 
109 
110 /*
111  * The default maximum segment size (MSS) to be used for new TCP connections
112  * when path MTU discovery is not enabled.
113  *
114  * RFC879 derives the default MSS from the largest datagram size hosts are
115  * minimally required to handle directly or through IP reassembly minus the
116  * size of the IP and TCP header.  With IPv6 the minimum MTU is specified
117  * in RFC2460.
118  *
119  * For IPv4 the MSS is 576 - sizeof(struct tcpiphdr)
120  * For IPv6 the MSS is IPV6_MMTU - sizeof(struct ip6_hdr) - sizeof(struct tcphdr)
121  *
122  * We use explicit numerical definition here to avoid header pollution.
123  */
124 #define	TCP_MSS		536
125 #define	TCP6_MSS	1220
126 
127 /*
128  * Limit the lowest MSS we accept for path MTU discovery and the TCP SYN MSS
129  * option.  Allowing low values of MSS can consume significant resources and
130  * be used to mount a resource exhaustion attack.
131  * Connections requesting lower MSS values will be rounded up to this value
132  * and the IP_DF flag will be cleared to allow fragmentation along the path.
133  *
134  * See tcp_subr.c tcp_minmss SYSCTL declaration for more comments.  Setting
135  * it to "0" disables the minmss check.
136  *
137  * The default value is fine for TCP across the Internet's smallest official
138  * link MTU (256 bytes for AX.25 packet radio).  However, a connection is very
139  * unlikely to come across such low MTU interfaces these days (anno domini 2003).
140  */
141 #define	TCP_MINMSS 216
142 
143 #define	TCP_MAXWIN	65535	/* largest value for (unscaled) window */
144 #define	TTCP_CLIENT_SND_WND	4096	/* dflt send window for T/TCP client */
145 
146 #define TCP_MAX_WINSHIFT	14	/* maximum window shift */
147 
148 #define TCP_MAXBURST		4	/* maximum segments in a burst */
149 
150 #define TCP_MAXHLEN	(0xf<<2)	/* max length of header in bytes */
151 #define TCP_MAXOLEN	(TCP_MAXHLEN - sizeof(struct tcphdr))
152 					/* max space left for options */
153 
154 #define TCP_FASTOPEN_MIN_COOKIE_LEN	4	/* Per RFC7413 */
155 #define TCP_FASTOPEN_MAX_COOKIE_LEN	16	/* Per RFC7413 */
156 #define TCP_FASTOPEN_PSK_LEN		16	/* Same as TCP_FASTOPEN_KEY_LEN */
157 #endif /* __BSD_VISIBLE */
158 
159 /*
160  * User-settable options (used with setsockopt).  These are discrete
161  * values and are not masked together.  Some values appear to be
162  * bitmasks for historical reasons.
163  */
164 #define	TCP_NODELAY	1	/* don't delay send to coalesce packets */
165 #if __BSD_VISIBLE
166 #define	TCP_MAXSEG	2	/* set maximum segment size */
167 #define TCP_NOPUSH	4	/* don't push last block of write */
168 #define TCP_NOOPT	8	/* don't use TCP options */
169 #define TCP_MD5SIG	16	/* use MD5 digests (RFC2385) */
170 #define	TCP_INFO	32	/* retrieve tcp_info structure */
171 #define	TCP_CONGESTION	64	/* get/set congestion control algorithm */
172 #define	TCP_CCALGOOPT	65	/* get/set cc algorithm specific options */
173 #define	TCP_KEEPINIT	128	/* N, time to establish connection */
174 #define	TCP_KEEPIDLE	256	/* L,N,X start keeplives after this period */
175 #define	TCP_KEEPINTVL	512	/* L,N interval between keepalives */
176 #define	TCP_KEEPCNT	1024	/* L,N number of keepalives before close */
177 #define	TCP_FASTOPEN	1025	/* enable TFO / was created via TFO */
178 #define	TCP_PCAP_OUT	2048	/* number of output packets to keep */
179 #define	TCP_PCAP_IN	4096	/* number of input packets to keep */
180 #define TCP_FUNCTION_BLK 8192	/* Set the tcp function pointers to the specified stack */
181 /* Start of reserved space for third-party user-settable options. */
182 #define	TCP_VENDOR	SO_VENDOR
183 
184 #define	TCP_CA_NAME_MAX	16	/* max congestion control name length */
185 
186 #define	TCPI_OPT_TIMESTAMPS	0x01
187 #define	TCPI_OPT_SACK		0x02
188 #define	TCPI_OPT_WSCALE		0x04
189 #define	TCPI_OPT_ECN		0x08
190 #define	TCPI_OPT_TOE		0x10
191 
192 /*
193  * The TCP_INFO socket option comes from the Linux 2.6 TCP API, and permits
194  * the caller to query certain information about the state of a TCP
195  * connection.  We provide an overlapping set of fields with the Linux
196  * implementation, but since this is a fixed size structure, room has been
197  * left for growth.  In order to maximize potential future compatibility with
198  * the Linux API, the same variable names and order have been adopted, and
199  * padding left to make room for omitted fields in case they are added later.
200  *
201  * XXX: This is currently an unstable ABI/API, in that it is expected to
202  * change.
203  */
204 struct tcp_info {
205 	u_int8_t	tcpi_state;		/* TCP FSM state. */
206 	u_int8_t	__tcpi_ca_state;
207 	u_int8_t	__tcpi_retransmits;
208 	u_int8_t	__tcpi_probes;
209 	u_int8_t	__tcpi_backoff;
210 	u_int8_t	tcpi_options;		/* Options enabled on conn. */
211 	u_int8_t	tcpi_snd_wscale:4,	/* RFC1323 send shift value. */
212 			tcpi_rcv_wscale:4;	/* RFC1323 recv shift value. */
213 
214 	u_int32_t	tcpi_rto;		/* Retransmission timeout (usec). */
215 	u_int32_t	__tcpi_ato;
216 	u_int32_t	tcpi_snd_mss;		/* Max segment size for send. */
217 	u_int32_t	tcpi_rcv_mss;		/* Max segment size for receive. */
218 
219 	u_int32_t	__tcpi_unacked;
220 	u_int32_t	__tcpi_sacked;
221 	u_int32_t	__tcpi_lost;
222 	u_int32_t	__tcpi_retrans;
223 	u_int32_t	__tcpi_fackets;
224 
225 	/* Times; measurements in usecs. */
226 	u_int32_t	__tcpi_last_data_sent;
227 	u_int32_t	__tcpi_last_ack_sent;	/* Also unimpl. on Linux? */
228 	u_int32_t	tcpi_last_data_recv;	/* Time since last recv data. */
229 	u_int32_t	__tcpi_last_ack_recv;
230 
231 	/* Metrics; variable units. */
232 	u_int32_t	__tcpi_pmtu;
233 	u_int32_t	__tcpi_rcv_ssthresh;
234 	u_int32_t	tcpi_rtt;		/* Smoothed RTT in usecs. */
235 	u_int32_t	tcpi_rttvar;		/* RTT variance in usecs. */
236 	u_int32_t	tcpi_snd_ssthresh;	/* Slow start threshold. */
237 	u_int32_t	tcpi_snd_cwnd;		/* Send congestion window. */
238 	u_int32_t	__tcpi_advmss;
239 	u_int32_t	__tcpi_reordering;
240 
241 	u_int32_t	__tcpi_rcv_rtt;
242 	u_int32_t	tcpi_rcv_space;		/* Advertised recv window. */
243 
244 	/* FreeBSD extensions to tcp_info. */
245 	u_int32_t	tcpi_snd_wnd;		/* Advertised send window. */
246 	u_int32_t	tcpi_snd_bwnd;		/* No longer used. */
247 	u_int32_t	tcpi_snd_nxt;		/* Next egress seqno */
248 	u_int32_t	tcpi_rcv_nxt;		/* Next ingress seqno */
249 	u_int32_t	tcpi_toe_tid;		/* HWTID for TOE endpoints */
250 	u_int32_t	tcpi_snd_rexmitpack;	/* Retransmitted packets */
251 	u_int32_t	tcpi_rcv_ooopack;	/* Out-of-order packets */
252 	u_int32_t	tcpi_snd_zerowin;	/* Zero-sized windows sent */
253 
254 	/* Padding to grow without breaking ABI. */
255 	u_int32_t	__tcpi_pad[26];		/* Padding. */
256 };
257 
258 /*
259  * If this structure is provided when setting the TCP_FASTOPEN socket
260  * option, and the enable member is non-zero, a subsequent connect will use
261  * pre-shared key (PSK) mode using the provided key.
262  */
263 struct tcp_fastopen {
264 	int enable;
265 	uint8_t psk[TCP_FASTOPEN_PSK_LEN];
266 };
267 #endif
268 #define TCP_FUNCTION_NAME_LEN_MAX 32
269 
270 struct tcp_function_set {
271 	char function_set_name[TCP_FUNCTION_NAME_LEN_MAX];
272 	uint32_t pcbcnt;
273 };
274 
275 #endif /* !_NETINET_TCP_H_ */
276