Annotation of qemu/slirp/tcp_var.h, revision 1.1.1.5

1.1       root        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.
1.1.1.3   root       13:  * 3. Neither the name of the University nor the names of its contributors
1.1       root       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 {
1.1.1.3   root       43:        struct tcpiphdr *seg_next;      /* sequencing queue */
                     44:        struct tcpiphdr *seg_prev;
1.1       root       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: 
1.1.1.4   root       64:        struct  tcpiphdr t_template;    /* static skeletal packet for xmit */
1.1       root       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 */
1.1.1.5 ! root       78:        uint32_t snd_wnd;               /* send window */
1.1       root       79: /* receive sequence variables */
1.1.1.5 ! root       80:        uint32_t rcv_wnd;               /* receive window */
1.1       root       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) */
1.1.1.5 ! root       94:        uint32_t snd_cwnd;              /* congestion-controlled window */
        !            95:        uint32_t snd_ssthresh;          /* snd_cwnd size threshold for
1.1       root       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 */
1.1.1.5 ! root      109:        uint32_t max_sndwnd;            /* largest window peer has offered */
1.1       root      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;
1.1.1.5 ! root      123:        uint32_t        ts_recent;              /* timestamp echo data */
        !           124:        uint32_t        ts_recent_age;          /* when last updated */
1.1       root      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

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