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    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: 	u_int32_t snd_wnd;		/* send window */
   79: /* receive sequence variables */
   80: 	u_int32_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: 	u_int32_t snd_cwnd;		/* congestion-controlled window */
   95: 	u_int32_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: 	u_int32_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: 	u_int32_t	ts_recent;		/* timestamp echo data */
  124: 	u_int32_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