162 lines
6.5 KiB
C
162 lines
6.5 KiB
C
/*
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* Copyright (c) 1982, 1986, 1993, 1994
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)tcp_var.h 8.3 (Berkeley) 4/10/94
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* tcp_var.h,v 1.3 1994/08/21 05:27:39 paul Exp
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*/
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#ifndef _TCP_VAR_H_
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#define _TCP_VAR_H_
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#include "tcpip.h"
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#include "tcp_timer.h"
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/*
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* Tcp control block, one per tcp; fields:
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*/
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struct tcpcb {
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struct tcpiphdr *seg_next; /* sequencing queue */
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struct tcpiphdr *seg_prev;
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short t_state; /* state of this connection */
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short t_timer[TCPT_NTIMERS]; /* tcp timers */
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short t_rxtshift; /* log(2) of rexmt exp. backoff */
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short t_rxtcur; /* current retransmit value */
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short t_dupacks; /* consecutive dup acks recd */
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u_short t_maxseg; /* maximum segment size */
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char t_force; /* 1 if forcing out a byte */
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u_short t_flags;
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#define TF_ACKNOW 0x0001 /* ack peer immediately */
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#define TF_DELACK 0x0002 /* ack, but try to delay it */
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#define TF_NODELAY 0x0004 /* don't delay packets to coalesce */
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#define TF_NOOPT 0x0008 /* don't use tcp options */
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#define TF_SENTFIN 0x0010 /* have sent FIN */
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#define TF_REQ_SCALE 0x0020 /* have/will request window scaling */
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#define TF_RCVD_SCALE 0x0040 /* other side has requested scaling */
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#define TF_REQ_TSTMP 0x0080 /* have/will request timestamps */
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#define TF_RCVD_TSTMP 0x0100 /* a timestamp was received in SYN */
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#define TF_SACK_PERMIT 0x0200 /* other side said I could SACK */
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struct tcpiphdr t_template; /* static skeletal packet for xmit */
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struct socket *t_socket; /* back pointer to socket */
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/*
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* The following fields are used as in the protocol specification.
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* See RFC783, Dec. 1981, page 21.
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*/
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/* send sequence variables */
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tcp_seq snd_una; /* send unacknowledged */
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tcp_seq snd_nxt; /* send next */
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tcp_seq snd_up; /* send urgent pointer */
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tcp_seq snd_wl1; /* window update seg seq number */
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tcp_seq snd_wl2; /* window update seg ack number */
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tcp_seq iss; /* initial send sequence number */
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uint32_t snd_wnd; /* send window */
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/* receive sequence variables */
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uint32_t rcv_wnd; /* receive window */
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tcp_seq rcv_nxt; /* receive next */
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tcp_seq rcv_up; /* receive urgent pointer */
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tcp_seq irs; /* initial receive sequence number */
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/*
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* Additional variables for this implementation.
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*/
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/* receive variables */
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tcp_seq rcv_adv; /* advertised window */
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/* retransmit variables */
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tcp_seq snd_max; /* highest sequence number sent;
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* used to recognize retransmits
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*/
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/* congestion control (for slow start, source quench, retransmit after loss) */
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uint32_t snd_cwnd; /* congestion-controlled window */
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uint32_t snd_ssthresh; /* snd_cwnd size threshold for
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* for slow start exponential to
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* linear switch
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*/
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/*
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* transmit timing stuff. See below for scale of srtt and rttvar.
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* "Variance" is actually smoothed difference.
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*/
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short t_idle; /* inactivity time */
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short t_rtt; /* round trip time */
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tcp_seq t_rtseq; /* sequence number being timed */
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short t_srtt; /* smoothed round-trip time */
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short t_rttvar; /* variance in round-trip time */
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u_short t_rttmin; /* minimum rtt allowed */
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uint32_t max_sndwnd; /* largest window peer has offered */
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/* out-of-band data */
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char t_oobflags; /* have some */
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char t_iobc; /* input character */
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#define TCPOOB_HAVEDATA 0x01
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#define TCPOOB_HADDATA 0x02
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short t_softerror; /* possible error not yet reported */
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/* RFC 1323 variables */
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u_char snd_scale; /* window scaling for send window */
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u_char rcv_scale; /* window scaling for recv window */
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u_char request_r_scale; /* pending window scaling */
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u_char requested_s_scale;
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uint32_t ts_recent; /* timestamp echo data */
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uint32_t ts_recent_age; /* when last updated */
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tcp_seq last_ack_sent;
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};
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#define sototcpcb(so) ((so)->so_tcpcb)
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/*
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* The smoothed round-trip time and estimated variance
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* are stored as fixed point numbers scaled by the values below.
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* For convenience, these scales are also used in smoothing the average
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* (smoothed = (1/scale)sample + ((scale-1)/scale)smoothed).
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* With these scales, srtt has 3 bits to the right of the binary point,
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* and thus an "ALPHA" of 0.875. rttvar has 2 bits to the right of the
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* binary point, and is smoothed with an ALPHA of 0.75.
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*/
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#define TCP_RTT_SCALE 8 /* multiplier for srtt; 3 bits frac. */
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#define TCP_RTT_SHIFT 3 /* shift for srtt; 3 bits frac. */
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#define TCP_RTTVAR_SCALE 4 /* multiplier for rttvar; 2 bits */
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#define TCP_RTTVAR_SHIFT 2 /* multiplier for rttvar; 2 bits */
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/*
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* The initial retransmission should happen at rtt + 4 * rttvar.
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* Because of the way we do the smoothing, srtt and rttvar
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* will each average +1/2 tick of bias. When we compute
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* the retransmit timer, we want 1/2 tick of rounding and
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* 1 extra tick because of +-1/2 tick uncertainty in the
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* firing of the timer. The bias will give us exactly the
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* 1.5 tick we need. But, because the bias is
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* statistical, we have to test that we don't drop below
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* the minimum feasible timer (which is 2 ticks).
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* This macro assumes that the value of TCP_RTTVAR_SCALE
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* is the same as the multiplier for rttvar.
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*/
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#define TCP_REXMTVAL(tp) \
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(((tp)->t_srtt >> TCP_RTT_SHIFT) + (tp)->t_rttvar)
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#endif
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