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/*

 * Copyright (c) 1982, 1986, 1993, 1994

 *        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.

 * 3. 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_var.h        8.3 (Berkeley) 4/10/94

 * tcp_var.h,v 1.3 1994/08/21 05:27:39 paul Exp

 */

#ifndef _TCP_VAR_H_

#define _TCP_VAR_H_

#include "tcpip.h"

#include "tcp_timer.h"

/*

 * Tcp control block, one per tcp; fields:

 */

struct tcpcb {

        struct tcpiphdr *seg_next;        /* sequencing queue */

        struct tcpiphdr *seg_prev;

        short        t_state;                /* state of this connection */

        short        t_timer[TCPT_NTIMERS];        /* tcp timers */

        short        t_rxtshift;                /* log(2) of rexmt exp. backoff */

        short        t_rxtcur;                /* current retransmit value */

        short        t_dupacks;                /* consecutive dup acks recd */

        u_short        t_maxseg;                /* maximum segment size */

        char        t_force;                /* 1 if forcing out a byte */

        u_short        t_flags;

#define        TF_ACKNOW        0x0001                /* ack peer immediately */

#define        TF_DELACK        0x0002                /* ack, but try to delay it */

#define        TF_NODELAY        0x0004                /* don't delay packets to coalesce */

#define        TF_NOOPT        0x0008                /* don't use tcp options */

#define        TF_SENTFIN        0x0010                /* have sent FIN */

#define        TF_REQ_SCALE        0x0020                /* have/will request window scaling */

#define        TF_RCVD_SCALE        0x0040                /* other side has requested scaling */

#define        TF_REQ_TSTMP        0x0080                /* have/will request timestamps */

#define        TF_RCVD_TSTMP        0x0100                /* a timestamp was received in SYN */

#define        TF_SACK_PERMIT        0x0200                /* other side said I could SACK */

        struct        tcpiphdr t_template;    /* static skeletal packet for xmit */

        struct        socket *t_socket;                /* back pointer to socket */

/*

 * The following fields are used as in the protocol specification.

 * See RFC783, Dec. 1981, page 21.

 */

/* send sequence variables */

        tcp_seq        snd_una;                /* send unacknowledged */

        tcp_seq        snd_nxt;                /* send next */

        tcp_seq        snd_up;                        /* send urgent pointer */

        tcp_seq        snd_wl1;                /* window update seg seq number */

        tcp_seq        snd_wl2;                /* window update seg ack number */

        tcp_seq        iss;                        /* initial send sequence number */

        uint32_t snd_wnd;                /* send window */

/* receive sequence variables */

        uint32_t rcv_wnd;                /* receive window */

        tcp_seq        rcv_nxt;                /* receive next */

        tcp_seq        rcv_up;                        /* receive urgent pointer */

        tcp_seq        irs;                        /* initial receive sequence number */

/*

 * Additional variables for this implementation.

 */

/* receive variables */

        tcp_seq        rcv_adv;                /* advertised window */

/* retransmit variables */

        tcp_seq        snd_max;                /* highest sequence number sent;

                                         * used to recognize retransmits

                                         */

/* congestion control (for slow start, source quench, retransmit after loss) */

        uint32_t snd_cwnd;                /* congestion-controlled window */

        uint32_t snd_ssthresh;                /* snd_cwnd size threshold for

                                         * for slow start exponential to

                                         * linear switch

                                         */

/*

 * transmit timing stuff.  See below for scale of srtt and rttvar.

 * "Variance" is actually smoothed difference.

 */

        short        t_idle;                        /* inactivity time */

        short        t_rtt;                        /* round trip time */

        tcp_seq        t_rtseq;                /* sequence number being timed */

        short        t_srtt;                        /* smoothed round-trip time */

        short        t_rttvar;                /* variance in round-trip time */

        u_short        t_rttmin;                /* minimum rtt allowed */

        uint32_t max_sndwnd;                /* largest window peer has offered */

/* out-of-band data */

        char        t_oobflags;                /* have some */

        char        t_iobc;                        /* input character */

#define        TCPOOB_HAVEDATA        0x01

#define        TCPOOB_HADDATA        0x02

        short        t_softerror;                /* possible error not yet reported */

/* RFC 1323 variables */

        u_char        snd_scale;                /* window scaling for send window */

        u_char        rcv_scale;                /* window scaling for recv window */

        u_char        request_r_scale;        /* pending window scaling */

        u_char        requested_s_scale;

        uint32_t        ts_recent;                /* timestamp echo data */

        uint32_t        ts_recent_age;                /* when last updated */

        tcp_seq        last_ack_sent;

};

#define        sototcpcb(so)        ((so)->so_tcpcb)

/*

 * The smoothed round-trip time and estimated variance

 * are stored as fixed point numbers scaled by the values below.

 * For convenience, these scales are also used in smoothing the average

 * (smoothed = (1/scale)sample + ((scale-1)/scale)smoothed).

 * With these scales, srtt has 3 bits to the right of the binary point,

 * and thus an "ALPHA" of 0.875.  rttvar has 2 bits to the right of the

 * binary point, and is smoothed with an ALPHA of 0.75.

 */

#define        TCP_RTT_SCALE                8        /* multiplier for srtt; 3 bits frac. */

#define        TCP_RTT_SHIFT                3        /* shift for srtt; 3 bits frac. */

#define        TCP_RTTVAR_SCALE        4        /* multiplier for rttvar; 2 bits */

#define        TCP_RTTVAR_SHIFT        2        /* multiplier for rttvar; 2 bits */

/*

 * The initial retransmission should happen at rtt + 4 * rttvar.

 * Because of the way we do the smoothing, srtt and rttvar

 * will each average +1/2 tick of bias.  When we compute

 * the retransmit timer, we want 1/2 tick of rounding and

 * 1 extra tick because of +-1/2 tick uncertainty in the

 * firing of the timer.  The bias will give us exactly the

 * 1.5 tick we need.  But, because the bias is

 * statistical, we have to test that we don't drop below

 * the minimum feasible timer (which is 2 ticks).

 * This macro assumes that the value of TCP_RTTVAR_SCALE

 * is the same as the multiplier for rttvar.

 */

#define        TCP_REXMTVAL(tp) \

        (((tp)->t_srtt >> TCP_RTT_SHIFT) + (tp)->t_rttvar)

#endif