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 */ 42struct 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 uint8_t 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 uint32_t snd_wnd; /* send window */ 79/* receive sequence variables */ 80 uint32_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 uint32_t snd_cwnd; /* congestion-controlled window */ 95 uint32_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 uint32_t max_sndwnd; /* largest window peer has offered */ 110 111/* out-of-band data */ 112 uint8_t t_oobflags; /* have some */ 113 uint8_t 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 uint32_t ts_recent; /* timestamp echo data */ 124 uint32_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 162