1 /* 2 * Copyright (c) 1982 Regents of the University of California. 3 * All rights reserved. The Berkeley software License Agreement 4 * specifies the terms and conditions for redistribution. 5 * 6 * @(#)tcp.h 6.4 (Berkeley) 01/13/86 7 */ 8 9 typedef u_long tcp_seq; 10 /* 11 * TCP header. 12 * Per RFC 793, September, 1981. 13 */ 14 struct tcphdr { 15 u_short th_sport; /* source port */ 16 u_short th_dport; /* destination port */ 17 tcp_seq th_seq; /* sequence number */ 18 tcp_seq th_ack; /* acknowledgement number */ 19 #ifdef vax 20 u_char th_x2:4, /* (unused) */ 21 th_off:4; /* data offset */ 22 #endif 23 u_char th_flags; 24 #define TH_FIN 0x01 25 #define TH_SYN 0x02 26 #define TH_RST 0x04 27 #define TH_PUSH 0x08 28 #define TH_ACK 0x10 29 #define TH_URG 0x20 30 u_short th_win; /* window */ 31 u_short th_sum; /* checksum */ 32 u_short th_urp; /* urgent pointer */ 33 }; 34 35 #define TCPOPT_EOL 0 36 #define TCPOPT_NOP 1 37 #define TCPOPT_MAXSEG 2 38 39 /* 40 * Default maximum segment size for TCP. 41 * With an IP MSS of 576, this is 536, 42 * but 512 is probably more convenient. 43 */ 44 #define TCP_MSS MIN(512, IP_MSS - sizeof (struct tcpiphdr)) 45 46 /* 47 * User-settable options (used with setsockopt). 48 */ 49 #define TCP_NODELAY 0x01 /* don't delay send to coalesce packets */ 50 #define TCP_MAXSEG 0x02 /* set maximum segment size */ 51