slirp/tcp_var.h

   1 /*
   2  * Copyright (c) 1982, 1986, 1993, 1994
   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  * 3. 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_var.h   8.3 (Berkeley) 4/10/94
  30  * tcp_var.h,v 1.3 1994/08/21 05:27:39 paul Exp
  31  */
  32
  33 #ifndef _TCP_VAR_H_
  34 #define _TCP_VAR_H_
  35
  36 #include "tcpip.h"
  37 #include "tcp_timer.h"
  38
  39 /*
  40  * Tcp control block, one per tcp; fields:
  41  */
  42 struct tcpcb {
  43         struct tcpiphdr *seg_next;      /* sequencing queue */
  44         struct tcpiphdr *seg_prev;
  45         short   t_state;                /* state of this connection */
  46         short   t_timer[TCPT_NTIMERS];  /* tcp timers */
  47         short   t_rxtshift;             /* log(2) of rexmt exp. backoff */
  48         short   t_rxtcur;               /* current retransmit value */
  49         short   t_dupacks;              /* consecutive dup acks recd */
  50         u_short t_maxseg;               /* maximum segment size */
  51         char    t_force;                /* 1 if forcing out a byte */
  52         u_short t_flags;
  53 #define TF_ACKNOW       0x0001          /* ack peer immediately */
  54 #define TF_DELACK       0x0002          /* ack, but try to delay it */
  55 #define TF_NODELAY      0x0004          /* don't delay packets to coalesce */
  56 #define TF_NOOPT        0x0008          /* don't use tcp options */
  57 #define TF_SENTFIN      0x0010          /* have sent FIN */
  58 #define TF_REQ_SCALE    0x0020          /* have/will request window scaling */
  59 #define TF_RCVD_SCALE   0x0040          /* other side has requested scaling */
  60 #define TF_REQ_TSTMP    0x0080          /* have/will request timestamps */
  61 #define TF_RCVD_TSTMP   0x0100          /* a timestamp was received in SYN */
  62 #define TF_SACK_PERMIT  0x0200          /* other side said I could SACK */
  63
  64         struct  tcpiphdr t_template;    /* static skeletal packet for xmit */
  65
  66         struct  socket *t_socket;               /* back pointer to socket */
  67 /*
  68  * The following fields are used as in the protocol specification.
  69  * See RFC783, Dec. 1981, page 21.
  70  */
  71 /* send sequence variables */
  72         tcp_seq snd_una;                /* send unacknowledged */
  73         tcp_seq snd_nxt;                /* send next */
  74         tcp_seq snd_up;                 /* send urgent pointer */
  75         tcp_seq snd_wl1;                /* window update seg seq number */
  76         tcp_seq snd_wl2;                /* window update seg ack number */
  77         tcp_seq iss;                    /* initial send sequence number */
  78         uint32_t snd_wnd;               /* send window */
  79 /* receive sequence variables */
  80         uint32_t rcv_wnd;               /* receive window */
  81         tcp_seq rcv_nxt;                /* receive next */
  82         tcp_seq rcv_up;                 /* receive urgent pointer */
  83         tcp_seq irs;                    /* initial receive sequence number */
  84 /*
  85  * Additional variables for this implementation.
  86  */
  87 /* receive variables */
  88         tcp_seq rcv_adv;                /* advertised window */
  89 /* retransmit variables */
  90         tcp_seq snd_max;                /* highest sequence number sent;
  91                                          * used to recognize retransmits
  92                                          */
  93 /* congestion control (for slow start, source quench, retransmit after loss) */
  94         uint32_t snd_cwnd;              /* congestion-controlled window */
  95         uint32_t snd_ssthresh;          /* snd_cwnd size threshold for
  96                                          * for slow start exponential to
  97                                          * linear switch
  98                                          */
  99 /*
 100  * transmit timing stuff.  See below for scale of srtt and rttvar.
 101  * "Variance" is actually smoothed difference.
 102  */
 103         short   t_idle;                 /* inactivity time */
 104         short   t_rtt;                  /* round trip time */
 105         tcp_seq t_rtseq;                /* sequence number being timed */
 106         short   t_srtt;                 /* smoothed round-trip time */
 107         short   t_rttvar;               /* variance in round-trip time */
 108         u_short t_rttmin;               /* minimum rtt allowed */
 109         uint32_t max_sndwnd;            /* largest window peer has offered */
 110
 111 /* out-of-band data */
 112         char    t_oobflags;             /* have some */
 113         char    t_iobc;                 /* input character */
 114 #define TCPOOB_HAVEDATA 0x01
 115 #define TCPOOB_HADDATA  0x02
 116         short   t_softerror;            /* possible error not yet reported */
 117
 118 /* RFC 1323 variables */
 119         u_char  snd_scale;              /* window scaling for send window */
 120         u_char  rcv_scale;              /* window scaling for recv window */
 121         u_char  request_r_scale;        /* pending window scaling */
 122         u_char  requested_s_scale;
 123         uint32_t        ts_recent;              /* timestamp echo data */
 124         uint32_t        ts_recent_age;          /* when last updated */
 125         tcp_seq last_ack_sent;
 126
 127 };
 128
 129 #define sototcpcb(so)   ((so)->so_tcpcb)
 130
 131 /*
 132  * The smoothed round-trip time and estimated variance
 133  * are stored as fixed point numbers scaled by the values below.
 134  * For convenience, these scales are also used in smoothing the average
 135  * (smoothed = (1/scale)sample + ((scale-1)/scale)smoothed).
 136  * With these scales, srtt has 3 bits to the right of the binary point,
 137  * and thus an "ALPHA" of 0.875.  rttvar has 2 bits to the right of the
 138  * binary point, and is smoothed with an ALPHA of 0.75.
 139  */
 140 #define TCP_RTT_SCALE           8       /* multiplier for srtt; 3 bits frac. */
 141 #define TCP_RTT_SHIFT           3       /* shift for srtt; 3 bits frac. */
 142 #define TCP_RTTVAR_SCALE        4       /* multiplier for rttvar; 2 bits */
 143 #define TCP_RTTVAR_SHIFT        2       /* multiplier for rttvar; 2 bits */
 144
 145 /*
 146  * The initial retransmission should happen at rtt + 4 * rttvar.
 147  * Because of the way we do the smoothing, srtt and rttvar
 148  * will each average +1/2 tick of bias.  When we compute
 149  * the retransmit timer, we want 1/2 tick of rounding and
 150  * 1 extra tick because of +-1/2 tick uncertainty in the
 151  * firing of the timer.  The bias will give us exactly the
 152  * 1.5 tick we need.  But, because the bias is
 153  * statistical, we have to test that we don't drop below
 154  * the minimum feasible timer (which is 2 ticks).
 155  * This macro assumes that the value of TCP_RTTVAR_SCALE
 156  * is the same as the multiplier for rttvar.
 157  */
 158 #define TCP_REXMTVAL(tp) \
 159         (((tp)->t_srtt >> TCP_RTT_SHIFT) + (tp)->t_rttvar)
 160
 161 #endif