1 /* tcp.h 1.16 81/11/15 */ 2 3 /* 4 * TCP header. 5 */ 6 struct tcphdr { 7 u_short th_sport; /* source port */ 8 u_short th_dport; /* destination port */ 9 seq_t th_seq; /* sequence number */ 10 seq_t th_ackno; /* acknowledgement number */ 11 u_char 12 th_x2:4, /* (unused) */ 13 th_off:4; /* data offset */ 14 u_char th_flags; 15 #define TH_FIN 001 16 #define TH_SYN 002 17 #define TH_RST 004 18 #define TH_EOL 010 19 #define TH_ACK 020 20 #define TH_URG 040 21 u_short th_win; /* window */ 22 u_short th_sum; /* checksum */ 23 u_short th_urp; /* urgent pointer */ 24 }; 25