slirp/src/tcp_var.h - qemu - Git at Google

 /* SPDX-License-Identifier: BSD-3-Clause */
 /*
  * 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 */
 	uint16_t	t_maxseg;		/* maximum segment size */
 	uint8_t t_force;		/* 1 if forcing out a byte */
 	uint16_t	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 */
 	uint16_t	t_rttmin;		/* minimum rtt allowed */
 	uint32_t max_sndwnd;		/* largest window peer has offered */

 /* out-of-band data */
 	uint8_t	t_oobflags;		/* have some */
 	uint8_t	t_iobc;			/* input character */
 #define	TCPOOB_HAVEDATA	0x01
 #define	TCPOOB_HADDATA	0x02
 	short	t_softerror;		/* possible error not yet reported */

 /* RFC 1323 variables */
 	uint8_t	snd_scale;		/* window scaling for send window */
 	uint8_t	rcv_scale;		/* window scaling for recv window */
 	uint8_t	request_r_scale;	/* pending window scaling */
 	uint8_t	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
	/* SPDX-License-Identifier: BSD-3-Clause */
	/*
	* 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 */
	uint16_t t_maxseg; /* maximum segment size */
	uint8_t t_force; /* 1 if forcing out a byte */
	uint16_t 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 */
	uint16_t t_rttmin; /* minimum rtt allowed */
	uint32_t max_sndwnd; /* largest window peer has offered */

	/* out-of-band data */
	uint8_t t_oobflags; /* have some */
	uint8_t t_iobc; /* input character */
	#define TCPOOB_HAVEDATA 0x01
	#define TCPOOB_HADDATA 0x02
	short t_softerror; /* possible error not yet reported */

	/* RFC 1323 variables */
	uint8_t snd_scale; /* window scaling for send window */
	uint8_t rcv_scale; /* window scaling for recv window */
	uint8_t request_r_scale; /* pending window scaling */
	uint8_t 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