Revert "Increase the default TCP maximum segment size from 512 to 1460."
[dragonfly.git] / sys / netinet / tcp.h
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1/*
2 * Copyright (c) 1982, 1986, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed by the University of
16 * California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 *
33 * @(#)tcp.h 8.1 (Berkeley) 6/10/93
34 * $FreeBSD: src/sys/netinet/tcp.h,v 1.13.2.3 2001/03/01 22:08:42 jlemon Exp $
1bd40720 35 * $DragonFly: src/sys/netinet/tcp.h,v 1.7 2006/05/20 02:42:12 dillon Exp $
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36 */
37
38#ifndef _NETINET_TCP_H_
39#define _NETINET_TCP_H_
40
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41#ifndef _SYS_TYPES_H_
42#include <sys/types.h>
43#endif
44#ifndef _MACHINE_ENDIAN_H_
45#include <machine/endian.h>
46#endif
47
984263bc 48typedef u_int32_t tcp_seq;
91489f6b 49typedef int32_t tcp_seq_diff_t;
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50typedef u_int32_t tcp_cc; /* connection count per rfc1644 */
51
52#define tcp6_seq tcp_seq /* for KAME src sync over BSD*'s */
53#define tcp6hdr tcphdr /* for KAME src sync over BSD*'s */
54
55/*
56 * TCP header.
57 * Per RFC 793, September, 1981.
58 */
59struct tcphdr {
60 u_short th_sport; /* source port */
61 u_short th_dport; /* destination port */
62 tcp_seq th_seq; /* sequence number */
63 tcp_seq th_ack; /* acknowledgement number */
aae668f9 64#if _BYTE_ORDER == _LITTLE_ENDIAN
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65 u_int th_x2:4, /* (unused) */
66 th_off:4; /* data offset */
aae668f9 67#elif _BYTE_ORDER == _BIG_ENDIAN
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68 u_int th_off:4, /* data offset */
69 th_x2:4; /* (unused) */
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70#else
71#error "Byte order not implemented"
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72#endif
73 u_char th_flags;
74#define TH_FIN 0x01
75#define TH_SYN 0x02
76#define TH_RST 0x04
77#define TH_PUSH 0x08
78#define TH_ACK 0x10
79#define TH_URG 0x20
80#define TH_ECE 0x40
81#define TH_CWR 0x80
82#define TH_FLAGS (TH_FIN|TH_SYN|TH_RST|TH_ACK|TH_URG|TH_ECE|TH_CWR)
83
84 u_short th_win; /* window */
85 u_short th_sum; /* checksum */
86 u_short th_urp; /* urgent pointer */
87};
88
89#define TCPOPT_EOL 0
90#define TCPOPT_NOP 1
91489f6b 91#define TCPOPT_2NOPs (TCPOPT_NOP << 24 | TCPOPT_NOP << 16)
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92#define TCPOPT_MAXSEG 2
93#define TCPOLEN_MAXSEG 4
94#define TCPOPT_WINDOW 3
95#define TCPOLEN_WINDOW 3
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96#define TCPOPT_SACK_PERMITTED 4
97#define TCPOLEN_SACK_PERMITTED 2
98#define TCPOPT_SACK_PERMITTED_ALIGNED \
99 (TCPOPT_2NOPs | TCPOPT_SACK_PERMITTED << 8 | TCPOLEN_SACK_PERMITTED)
100#define TCPOLEN_SACK_PERMITTED_ALIGNED 4
101#define TCPOPT_SACK 5
102#define TCPOLEN_SACK 2
103#define TCPOLEN_SACK_BLOCK 8
104#define TCPOPT_SACK_ALIGNED (TCPOPT_2NOPs | TCPOPT_SACK << 8)
105#define TCPOLEN_SACK_ALIGNED 4
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106#define TCPOPT_TIMESTAMP 8
107#define TCPOLEN_TIMESTAMP 10
108#define TCPOLEN_TSTAMP_APPA (TCPOLEN_TIMESTAMP+2) /* appendix A */
109#define TCPOPT_TSTAMP_HDR \
91489f6b 110 (TCPOPT_2NOPs | TCPOPT_TIMESTAMP << 8 | TCPOLEN_TIMESTAMP)
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111#define TCPOPT_CC 11 /* CC options: RFC-1644 */
112#define TCPOPT_CCNEW 12
113#define TCPOPT_CCECHO 13
114#define TCPOLEN_CC 6
115#define TCPOLEN_CC_APPA (TCPOLEN_CC+2)
116#define TCPOPT_CC_HDR(ccopt) \
91489f6b 117 (TCPOPT_2NOPs | (ccopt) << 8 | TCPOLEN_CC)
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118
119/*
120 * Default maximum segment size for TCP.
121 * With an IP MSS of 576, this is 536,
122 * but 512 is probably more convenient.
123 * This should be defined as MIN(512, IP_MSS - sizeof (struct tcpiphdr)).
124 */
bf18b4fe 125#define TCP_MSS 512
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126
127/*
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128 * TCP_MINMSS is defined to be 256 which is fine for the smallest
129 * link MTU (296 bytes, SLIP interface) in the Internet.
130 * However it is very unlikely to come across such low MTU interfaces
131 * these days (anno dato 2003).
132 * Probably it can be set to 512 without ill effects. But we play safe.
133 * See tcp_subr.c tcp_minmss SYSCTL declaration for more comments.
134 * Setting this to "0" disables the minmss check.
135 */
136#define TCP_MINMSS 256
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137
138/*
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139 * Default maximum segment size for TCP6.
140 * With an IP6 MSS of 1280, this is 1220,
141 * but 1024 is probably more convenient. (xxx kazu in doubt)
142 * This should be defined as MIN(1024, IP6_MSS - sizeof (struct tcpip6hdr))
46e92930 143 *
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144 * NOTE: TCP_MIN_WINSHIFT is used when negotiating window scaling. Larger
145 * values are possible but apparently some firewires blows up if
146 * values larger then 5 are used, so use 5.
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147 */
148#define TCP6_MSS 1024
149
46e92930 150#define TCP_MAXWIN 65535 /* max value for (unscaled) window */
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151#define TTCP_CLIENT_SND_WND 4096 /* dflt send window for T/TCP client */
152
ce8b100c 153#define TCP_MIN_WINSHIFT 5 /* requested minimum (x32) */
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154#define TCP_MAX_WINSHIFT 14 /* maximum window shift */
155
f23061d4 156#define TCP_MAXBURST 4 /* maximum segments in a burst */
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157
158#define TCP_MAXHLEN (0xf<<2) /* max length of header in bytes */
159#define TCP_MAXOLEN (TCP_MAXHLEN - sizeof(struct tcphdr))
160 /* max space left for options */
161
162/*
163 * User-settable options (used with setsockopt).
164 */
165#define TCP_NODELAY 0x01 /* don't delay send to coalesce packets */
166#define TCP_MAXSEG 0x02 /* set maximum segment size */
167#define TCP_NOPUSH 0x04 /* don't push last block of write */
168#define TCP_NOOPT 0x08 /* don't use TCP options */
169
170#endif