/*	@(#)tcp.h 1.11 88/08/19 SMI; from UCB 7.2 10/28/86	*/

/*
 * Copyright (c) 1982, 1986 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 */

#ifndef _netinet_tcp_h
#define _netinet_tcp_h

typedef	u_long	tcp_seq;
/*
 * TCP header.
 * Per RFC 793, September, 1981.
 */
struct tcphdr {
	u_short	th_sport;		/* source port */
	u_short	th_dport;		/* destination port */
	tcp_seq	th_seq;			/* sequence number */
	tcp_seq	th_ack;			/* acknowledgement number */
#if __BYTE_ORDER == __LITTLE_ENDIAN
	u_char	th_x2:4,		/* (unused) */
		th_off:4;		/* data offset */
#endif
#if __BYTE_ORDER == __BIG_ENDIAN
	u_char	th_off:4,		/* data offset */
		th_x2:4;		/* (unused) */
#endif
	u_char	th_flags;
#define	TH_FIN	0x01
#define	TH_SYN	0x02
#define	TH_RST	0x04
#define	TH_PUSH	0x08
#define	TH_ACK	0x10
#define	TH_URG	0x20
	u_short	th_win;			/* window */
	u_short	th_sum;			/* checksum */
	u_short	th_urp;			/* urgent pointer */
};

#define	TCPOPT_EOL	0
#define	TCPOPT_NOP	1
#define	TCPOPT_MAXSEG	2

/*
 * Default maximum segment size for TCP.
 * With an IP MSS of 576, this is 536,
 * but 512 is probably more convenient.
 */
#ifdef	lint
#define	TCP_MSS	536
#else
#define	TCP_MSS	MIN(512, IP_MSS - sizeof (struct tcpiphdr))
#endif
#endif /*!_netinet_tcp_h*/