1 /* tcp.h 6.1 83/07/29 */ 2 3 typedef u_long tcp_seq; 4 /* 5 * TCP header. 6 * Per RFC 793, September, 1981. 7 */ 8 struct tcphdr { 9 u_short th_sport; /* source port */ 10 u_short th_dport; /* destination port */ 11 tcp_seq th_seq; /* sequence number */ 12 tcp_seq th_ack; /* acknowledgement number */ 13 #ifdef vax 14 u_char th_x2:4, /* (unused) */ 15 th_off:4; /* data offset */ 16 #endif 17 u_char th_flags; 18 #define TH_FIN 0x01 19 #define TH_SYN 0x02 20 #define TH_RST 0x04 21 #define TH_PUSH 0x08 22 #define TH_ACK 0x10 23 #define TH_URG 0x20 24 u_short th_win; /* window */ 25 u_short th_sum; /* checksum */ 26 u_short th_urp; /* urgent pointer */ 27 }; 28 29 #define TCPOPT_EOL 0 30 #define TCPOPT_NOP 1 31 #define TCPOPT_MAXSEG 2 32