FreeBSD/Linux Kernel Cross Reference
sys/netinet/tcp.h

     /*-
      * Copyright (c) 1982, 1986, 1993
      *      The Regents of the University of California.  All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      * 1. Redistributions of source code must retain the above copyright
      *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 4. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)tcp.h       8.1 (Berkeley) 6/10/93
     * $FreeBSD: releng/5.4/sys/netinet/tcp.h 145335 2005-04-20 19:11:07Z cvs2svn $
     */
    
    #ifndef _NETINET_TCP_H_
    #define _NETINET_TCP_H_
    
    #include <sys/cdefs.h>
    
    #if __BSD_VISIBLE
    
    typedef u_int32_t tcp_seq;
    typedef u_int32_t tcp_cc;               /* connection count per rfc1644 */
    
    #define tcp6_seq        tcp_seq /* for KAME src sync over BSD*'s */
    #define tcp6hdr         tcphdr  /* for KAME src sync over BSD*'s */
    
    /*
     * 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_int   th_x2:4,                /* (unused) */
                    th_off:4;               /* data offset */
    #endif
    #if BYTE_ORDER == BIG_ENDIAN
            u_int   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
    #define TH_ECE  0x40
    #define TH_CWR  0x80
    #define TH_FLAGS        (TH_FIN|TH_SYN|TH_RST|TH_ACK|TH_URG|TH_ECE|TH_CWR)
    
            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
    #define    TCPOLEN_MAXSEG               4
    #define TCPOPT_WINDOW           3
    #define    TCPOLEN_WINDOW               3
    #define TCPOPT_SACK_PERMITTED   4               /* Experimental */
    #define    TCPOLEN_SACK_PERMITTED       2
    #define TCPOPT_SACK             5               /* Experimental */
    #define    TCPOLEN_SACK                 8       /* 2*sizeof(tcp_seq) */
    #define TCPOPT_TIMESTAMP        8
    #define    TCPOLEN_TIMESTAMP            10
    #define    TCPOLEN_TSTAMP_APPA          (TCPOLEN_TIMESTAMP+2) /* appendix A */
    #define    TCPOPT_TSTAMP_HDR            \
        (TCPOPT_NOP<<24|TCPOPT_NOP<<16|TCPOPT_TIMESTAMP<<8|TCPOLEN_TIMESTAMP)
    
    #define MAX_TCPOPTLEN           40      /* Absolute maximum TCP options len */
    
    #define TCPOPT_CC               11              /* CC options: RFC-1644 */
    #define TCPOPT_CCNEW            12
    #define TCPOPT_CCECHO           13
   #define    TCPOLEN_CC                   6
   #define    TCPOLEN_CC_APPA              (TCPOLEN_CC+2)
   #define    TCPOPT_CC_HDR(ccopt)         \
       (TCPOPT_NOP<<24|TCPOPT_NOP<<16|(ccopt)<<8|TCPOLEN_CC)
   #define TCPOPT_SIGNATURE                19      /* Keyed MD5: RFC 2385 */
   #define    TCPOLEN_SIGNATURE            18
   
   /* Option definitions */
   #define TCPOPT_SACK_PERMIT_HDR  \
   (TCPOPT_NOP<<24|TCPOPT_NOP<<16|TCPOPT_SACK_PERMITTED<<8|TCPOLEN_SACK_PERMITTED)
   #define TCPOPT_SACK_HDR         (TCPOPT_NOP<<24|TCPOPT_NOP<<16|TCPOPT_SACK<<8)
   /* Miscellaneous constants */
   #define MAX_SACK_BLKS   6       /* Max # SACK blocks stored at sender side */
   #define TCP_MAX_SACK    3       /* MAX # SACKs sent in any segment */
   
   
   /*
    * Default maximum segment size for TCP.
    * With an IP MTU of 576, this is 536,
    * but 512 is probably more convenient.
    * This should be defined as MIN(512, IP_MSS - sizeof (struct tcpiphdr)).
    */
   #define TCP_MSS 512
   /*
    * TCP_MINMSS is defined to be 216 which is fine for the smallest
    * link MTU (256 bytes, AX.25 packet radio) in the Internet.
    * However it is very unlikely to come across such low MTU interfaces
    * these days (anno dato 2003).
    * See tcp_subr.c tcp_minmss SYSCTL declaration for more comments.
    * Setting this to "" disables the minmss check.
    */
   #define TCP_MINMSS 216
   /*
    * TCP_MINMSSOVERLOAD is defined to be 1000 which should cover any type
    * of interactive TCP session.
    * See tcp_subr.c tcp_minmssoverload SYSCTL declaration and tcp_input.c
    * for more comments.
    * Setting this to "" disables the minmssoverload check.
    */
   #define TCP_MINMSSOVERLOAD 0    /* XXX: Disabled until refined */
   
   /*
    * Default maximum segment size for TCP6.
    * With an IP6 MSS of 1280, this is 1220,
    * but 1024 is probably more convenient. (xxx kazu in doubt)
    * This should be defined as MIN(1024, IP6_MSS - sizeof (struct tcpip6hdr))
    */
   #define TCP6_MSS        1024
   
   #define TCP_MAXWIN      65535   /* largest value for (unscaled) window */
   #define TTCP_CLIENT_SND_WND     4096    /* dflt send window for T/TCP client */
   
   #define TCP_MAX_WINSHIFT        14      /* maximum window shift */
   
   #define TCP_MAXBURST            4       /* maximum segments in a burst */
   
   #define TCP_MAXHLEN     (0xf<<2)        /* max length of header in bytes */
   #define TCP_MAXOLEN     (TCP_MAXHLEN - sizeof(struct tcphdr))
                                           /* max space left for options */
   #endif /* __BSD_VISIBLE */
   
   /*
    * User-settable options (used with setsockopt).
    */
   #define TCP_NODELAY     0x01    /* don't delay send to coalesce packets */
   #if __BSD_VISIBLE
   #define TCP_MAXSEG      0x02    /* set maximum segment size */
   #define TCP_NOPUSH      0x04    /* don't push last block of write */
   #define TCP_NOOPT       0x08    /* don't use TCP options */
   #define TCP_MD5SIG      0x10    /* use MD5 digests (RFC2385) */
   #endif
   
   #endif /* !_NETINET_TCP_H_ */

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