The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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

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    1 /*-
    2  * Copyright (c) 1982, 1986, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  * 4. Neither the name of the University nor the names of its contributors
   14  *    may be used to endorse or promote products derived from this software
   15  *    without specific prior written permission.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * SUCH DAMAGE.
   28  *
   29  *      @(#)tcp.h       8.1 (Berkeley) 6/10/93
   30  * $FreeBSD$
   31  */
   32 
   33 #ifndef _NETINET_TCP_H_
   34 #define _NETINET_TCP_H_
   35 
   36 #include <sys/cdefs.h>
   37 #include <sys/types.h>
   38 
   39 #if __BSD_VISIBLE
   40 
   41 typedef u_int32_t tcp_seq;
   42 
   43 #define tcp6_seq        tcp_seq /* for KAME src sync over BSD*'s */
   44 #define tcp6hdr         tcphdr  /* for KAME src sync over BSD*'s */
   45 
   46 /*
   47  * TCP header.
   48  * Per RFC 793, September, 1981.
   49  */
   50 struct tcphdr {
   51         u_short th_sport;               /* source port */
   52         u_short th_dport;               /* destination port */
   53         tcp_seq th_seq;                 /* sequence number */
   54         tcp_seq th_ack;                 /* acknowledgement number */
   55 #if BYTE_ORDER == LITTLE_ENDIAN
   56         u_char  th_x2:4,                /* (unused) */
   57                 th_off:4;               /* data offset */
   58 #endif
   59 #if BYTE_ORDER == BIG_ENDIAN
   60         u_char  th_off:4,               /* data offset */
   61                 th_x2:4;                /* (unused) */
   62 #endif
   63         u_char  th_flags;
   64 #define TH_FIN  0x01
   65 #define TH_SYN  0x02
   66 #define TH_RST  0x04
   67 #define TH_PUSH 0x08
   68 #define TH_ACK  0x10
   69 #define TH_URG  0x20
   70 #define TH_ECE  0x40
   71 #define TH_CWR  0x80
   72 #define TH_FLAGS        (TH_FIN|TH_SYN|TH_RST|TH_PUSH|TH_ACK|TH_URG|TH_ECE|TH_CWR)
   73 #define PRINT_TH_FLAGS  "\2\1FIN\2SYN\3RST\4PUSH\5ACK\6URG\7ECE\10CWR"
   74 
   75         u_short th_win;                 /* window */
   76         u_short th_sum;                 /* checksum */
   77         u_short th_urp;                 /* urgent pointer */
   78 };
   79 
   80 #define TCPOPT_EOL              0
   81 #define    TCPOLEN_EOL                  1
   82 #define TCPOPT_PAD              0               /* padding after EOL */
   83 #define    TCPOLEN_PAD                  1
   84 #define TCPOPT_NOP              1
   85 #define    TCPOLEN_NOP                  1
   86 #define TCPOPT_MAXSEG           2
   87 #define    TCPOLEN_MAXSEG               4
   88 #define TCPOPT_WINDOW           3
   89 #define    TCPOLEN_WINDOW               3
   90 #define TCPOPT_SACK_PERMITTED   4
   91 #define    TCPOLEN_SACK_PERMITTED       2
   92 #define TCPOPT_SACK             5
   93 #define    TCPOLEN_SACKHDR              2
   94 #define    TCPOLEN_SACK                 8       /* 2*sizeof(tcp_seq) */
   95 #define TCPOPT_TIMESTAMP        8
   96 #define    TCPOLEN_TIMESTAMP            10
   97 #define    TCPOLEN_TSTAMP_APPA          (TCPOLEN_TIMESTAMP+2) /* appendix A */
   98 #define TCPOPT_SIGNATURE        19              /* Keyed MD5: RFC 2385 */
   99 #define    TCPOLEN_SIGNATURE            18
  100 #define TCPOPT_FAST_OPEN        34
  101 #define    TCPOLEN_FAST_OPEN_EMPTY      2
  102 #define    TCPOLEN_FAST_OPEN_MIN        6
  103 #define    TCPOLEN_FAST_OPEN_MAX        18
  104 
  105 /* Miscellaneous constants */
  106 #define MAX_SACK_BLKS   6       /* Max # SACK blocks stored at receiver side */
  107 #define TCP_MAX_SACK    4       /* MAX # SACKs sent in any segment */
  108 
  109 
  110 /*
  111  * The default maximum segment size (MSS) to be used for new TCP connections
  112  * when path MTU discovery is not enabled.
  113  *
  114  * RFC879 derives the default MSS from the largest datagram size hosts are
  115  * minimally required to handle directly or through IP reassembly minus the
  116  * size of the IP and TCP header.  With IPv6 the minimum MTU is specified
  117  * in RFC2460.
  118  *
  119  * For IPv4 the MSS is 576 - sizeof(struct tcpiphdr)
  120  * For IPv6 the MSS is IPV6_MMTU - sizeof(struct ip6_hdr) - sizeof(struct tcphdr)
  121  *
  122  * We use explicit numerical definition here to avoid header pollution.
  123  */
  124 #define TCP_MSS         536
  125 #define TCP6_MSS        1220
  126 
  127 /*
  128  * Limit the lowest MSS we accept for path MTU discovery and the TCP SYN MSS
  129  * option.  Allowing low values of MSS can consume significant resources and
  130  * be used to mount a resource exhaustion attack.
  131  * Connections requesting lower MSS values will be rounded up to this value
  132  * and the IP_DF flag will be cleared to allow fragmentation along the path.
  133  *
  134  * See tcp_subr.c tcp_minmss SYSCTL declaration for more comments.  Setting
  135  * it to "" disables the minmss check.
  136  *
  137  * The default value is fine for TCP across the Internet's smallest official
  138  * link MTU (256 bytes for AX.25 packet radio).  However, a connection is very
  139  * unlikely to come across such low MTU interfaces these days (anno domini 2003).
  140  */
  141 #define TCP_MINMSS 216
  142 
  143 #define TCP_MAXWIN      65535   /* largest value for (unscaled) window */
  144 #define TTCP_CLIENT_SND_WND     4096    /* dflt send window for T/TCP client */
  145 
  146 #define TCP_MAX_WINSHIFT        14      /* maximum window shift */
  147 
  148 #define TCP_MAXBURST            4       /* maximum segments in a burst */
  149 
  150 #define TCP_MAXHLEN     (0xf<<2)        /* max length of header in bytes */
  151 #define TCP_MAXOLEN     (TCP_MAXHLEN - sizeof(struct tcphdr))
  152                                         /* max space left for options */
  153 #endif /* __BSD_VISIBLE */
  154 
  155 /*
  156  * User-settable options (used with setsockopt).  These are discrete
  157  * values and are not masked together.  Some values appear to be
  158  * bitmasks for historical reasons.
  159  */
  160 #define TCP_NODELAY     1       /* don't delay send to coalesce packets */
  161 #if __BSD_VISIBLE
  162 #define TCP_MAXSEG      2       /* set maximum segment size */
  163 #define TCP_NOPUSH      4       /* don't push last block of write */
  164 #define TCP_NOOPT       8       /* don't use TCP options */
  165 #define TCP_MD5SIG      16      /* use MD5 digests (RFC2385) */
  166 #define TCP_INFO        32      /* retrieve tcp_info structure */
  167 #define TCP_CONGESTION  64      /* get/set congestion control algorithm */
  168 #define TCP_KEEPINIT    128     /* N, time to establish connection */
  169 #define TCP_KEEPIDLE    256     /* L,N,X start keeplives after this period */
  170 #define TCP_KEEPINTVL   512     /* L,N interval between keepalives */
  171 #define TCP_KEEPCNT     1024    /* L,N number of keepalives before close */
  172 #define TCP_FASTOPEN    1025    /* enable TFO / was created via TFO */
  173 
  174 /* Start of reserved space for third-party user-settable options. */
  175 #define TCP_VENDOR      SO_VENDOR
  176 
  177 #define TCP_CA_NAME_MAX 16      /* max congestion control name length */
  178 
  179 #define TCPI_OPT_TIMESTAMPS     0x01
  180 #define TCPI_OPT_SACK           0x02
  181 #define TCPI_OPT_WSCALE         0x04
  182 #define TCPI_OPT_ECN            0x08
  183 #define TCPI_OPT_TOE            0x10
  184 
  185 /*
  186  * The TCP_INFO socket option comes from the Linux 2.6 TCP API, and permits
  187  * the caller to query certain information about the state of a TCP
  188  * connection.  We provide an overlapping set of fields with the Linux
  189  * implementation, but since this is a fixed size structure, room has been
  190  * left for growth.  In order to maximize potential future compatibility with
  191  * the Linux API, the same variable names and order have been adopted, and
  192  * padding left to make room for omitted fields in case they are added later.
  193  *
  194  * XXX: This is currently an unstable ABI/API, in that it is expected to
  195  * change.
  196  */
  197 struct tcp_info {
  198         u_int8_t        tcpi_state;             /* TCP FSM state. */
  199         u_int8_t        __tcpi_ca_state;
  200         u_int8_t        __tcpi_retransmits;
  201         u_int8_t        __tcpi_probes;
  202         u_int8_t        __tcpi_backoff;
  203         u_int8_t        tcpi_options;           /* Options enabled on conn. */
  204         u_int8_t        tcpi_snd_wscale:4,      /* RFC1323 send shift value. */
  205                         tcpi_rcv_wscale:4;      /* RFC1323 recv shift value. */
  206 
  207         u_int32_t       tcpi_rto;               /* Retransmission timeout (usec). */
  208         u_int32_t       __tcpi_ato;
  209         u_int32_t       tcpi_snd_mss;           /* Max segment size for send. */
  210         u_int32_t       tcpi_rcv_mss;           /* Max segment size for receive. */
  211 
  212         u_int32_t       __tcpi_unacked;
  213         u_int32_t       __tcpi_sacked;
  214         u_int32_t       __tcpi_lost;
  215         u_int32_t       __tcpi_retrans;
  216         u_int32_t       __tcpi_fackets;
  217 
  218         /* Times; measurements in usecs. */
  219         u_int32_t       __tcpi_last_data_sent;
  220         u_int32_t       __tcpi_last_ack_sent;   /* Also unimpl. on Linux? */
  221         u_int32_t       tcpi_last_data_recv;    /* Time since last recv data. */
  222         u_int32_t       __tcpi_last_ack_recv;
  223 
  224         /* Metrics; variable units. */
  225         u_int32_t       __tcpi_pmtu;
  226         u_int32_t       __tcpi_rcv_ssthresh;
  227         u_int32_t       tcpi_rtt;               /* Smoothed RTT in usecs. */
  228         u_int32_t       tcpi_rttvar;            /* RTT variance in usecs. */
  229         u_int32_t       tcpi_snd_ssthresh;      /* Slow start threshold. */
  230         u_int32_t       tcpi_snd_cwnd;          /* Send congestion window. */
  231         u_int32_t       __tcpi_advmss;
  232         u_int32_t       __tcpi_reordering;
  233 
  234         u_int32_t       __tcpi_rcv_rtt;
  235         u_int32_t       tcpi_rcv_space;         /* Advertised recv window. */
  236 
  237         /* FreeBSD extensions to tcp_info. */
  238         u_int32_t       tcpi_snd_wnd;           /* Advertised send window. */
  239         u_int32_t       tcpi_snd_bwnd;          /* No longer used. */
  240         u_int32_t       tcpi_snd_nxt;           /* Next egress seqno */
  241         u_int32_t       tcpi_rcv_nxt;           /* Next ingress seqno */
  242         u_int32_t       tcpi_toe_tid;           /* HWTID for TOE endpoints */
  243         u_int32_t       tcpi_snd_rexmitpack;    /* Retransmitted packets */
  244         u_int32_t       tcpi_rcv_ooopack;       /* Out-of-order packets */
  245         u_int32_t       tcpi_snd_zerowin;       /* Zero-sized windows sent */
  246         
  247         /* Padding to grow without breaking ABI. */
  248         u_int32_t       __tcpi_pad[26];         /* Padding. */
  249 };
  250 #endif
  251 
  252 #endif /* !_NETINET_TCP_H_ */

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