1 /* SPDX-License-Identifier: BSD-3-Clause */ 2 /* 3 * Copyright (c) 1982, 1986, 1993, 1994 4 * The Regents of the University of California. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. Neither the name of the University nor the names of its contributors 15 * may be used to endorse or promote products derived from this software 16 * without specific prior written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28 * SUCH DAMAGE. 29 * 30 * @(#)tcp_var.h 8.3 (Berkeley) 4/10/94 31 * tcp_var.h,v 1.3 1994/08/21 05:27:39 paul Exp 32 */ 33 34 #ifndef TCP_VAR_H 35 #define TCP_VAR_H 36 37 #include "tcpip.h" 38 #include "tcp_timer.h" 39 40 /* 41 * Tcp control block, one per tcp; fields: 42 */ 43 struct tcpcb { 44 struct tcpiphdr *seg_next; /* sequencing queue */ 45 struct tcpiphdr *seg_prev; 46 short t_state; /* state of this connection */ 47 short t_timer[TCPT_NTIMERS]; /* tcp timers */ 48 short t_rxtshift; /* log(2) of rexmt exp. backoff */ 49 short t_rxtcur; /* current retransmit value */ 50 short t_dupacks; /* consecutive dup acks recd */ 51 uint16_t t_maxseg; /* maximum segment size */ 52 uint8_t t_force; /* 1 if forcing out a byte */ 53 uint16_t t_flags; 54 #define TF_ACKNOW 0x0001 /* ack peer immediately */ 55 #define TF_DELACK 0x0002 /* ack, but try to delay it */ 56 #define TF_NODELAY 0x0004 /* don't delay packets to coalesce */ 57 #define TF_NOOPT 0x0008 /* don't use tcp options */ 58 #define TF_SENTFIN 0x0010 /* have sent FIN */ 59 #define TF_REQ_SCALE 0x0020 /* have/will request window scaling */ 60 #define TF_RCVD_SCALE 0x0040 /* other side has requested scaling */ 61 #define TF_REQ_TSTMP 0x0080 /* have/will request timestamps */ 62 #define TF_RCVD_TSTMP 0x0100 /* a timestamp was received in SYN */ 63 #define TF_SACK_PERMIT 0x0200 /* other side said I could SACK */ 64 65 struct tcpiphdr t_template; /* static skeletal packet for xmit */ 66 67 struct socket *t_socket; /* back pointer to socket */ 68 /* 69 * The following fields are used as in the protocol specification. 70 * See RFC783, Dec. 1981, page 21. 71 */ 72 /* send sequence variables */ 73 tcp_seq snd_una; /* send unacknowledged */ 74 tcp_seq snd_nxt; /* send next */ 75 tcp_seq snd_up; /* send urgent pointer */ 76 tcp_seq snd_wl1; /* window update seg seq number */ 77 tcp_seq snd_wl2; /* window update seg ack number */ 78 tcp_seq iss; /* initial send sequence number */ 79 uint32_t snd_wnd; /* send window */ 80 /* receive sequence variables */ 81 uint32_t rcv_wnd; /* receive window */ 82 tcp_seq rcv_nxt; /* receive next */ 83 tcp_seq rcv_up; /* receive urgent pointer */ 84 tcp_seq irs; /* initial receive sequence number */ 85 /* 86 * Additional variables for this implementation. 87 */ 88 /* receive variables */ 89 tcp_seq rcv_adv; /* advertised window */ 90 /* retransmit variables */ 91 tcp_seq snd_max; /* highest sequence number sent; 92 * used to recognize retransmits 93 */ 94 /* congestion control (for slow start, source quench, retransmit after loss) 95 */ 96 uint32_t snd_cwnd; /* congestion-controlled window */ 97 uint32_t snd_ssthresh; /* snd_cwnd size threshold for 98 * for slow start exponential to 99 * linear switch 100 */ 101 /* 102 * transmit timing stuff. See below for scale of srtt and rttvar. 103 * "Variance" is actually smoothed difference. 104 */ 105 short t_idle; /* inactivity time */ 106 short t_rtt; /* round trip time */ 107 tcp_seq t_rtseq; /* sequence number being timed */ 108 short t_srtt; /* smoothed round-trip time */ 109 short t_rttvar; /* variance in round-trip time */ 110 uint16_t t_rttmin; /* minimum rtt allowed */ 111 uint32_t max_sndwnd; /* largest window peer has offered */ 112 113 /* out-of-band data */ 114 uint8_t t_oobflags; /* have some */ 115 uint8_t t_iobc; /* input character */ 116 #define TCPOOB_HAVEDATA 0x01 117 #define TCPOOB_HADDATA 0x02 118 short t_softerror; /* possible error not yet reported */ 119 120 /* RFC 1323 variables */ 121 uint8_t snd_scale; /* window scaling for send window */ 122 uint8_t rcv_scale; /* window scaling for recv window */ 123 uint8_t request_r_scale; /* pending window scaling */ 124 uint8_t requested_s_scale; 125 uint32_t ts_recent; /* timestamp echo data */ 126 uint32_t ts_recent_age; /* when last updated */ 127 tcp_seq last_ack_sent; 128 }; 129 130 #define sototcpcb(so) ((so)->so_tcpcb) 131 132 /* 133 * The smoothed round-trip time and estimated variance 134 * are stored as fixed point numbers scaled by the values below. 135 * For convenience, these scales are also used in smoothing the average 136 * (smoothed = (1/scale)sample + ((scale-1)/scale)smoothed). 137 * With these scales, srtt has 3 bits to the right of the binary point, 138 * and thus an "ALPHA" of 0.875. rttvar has 2 bits to the right of the 139 * binary point, and is smoothed with an ALPHA of 0.75. 140 */ 141 #define TCP_RTT_SCALE 8 /* multiplier for srtt; 3 bits frac. */ 142 #define TCP_RTT_SHIFT 3 /* shift for srtt; 3 bits frac. */ 143 #define TCP_RTTVAR_SCALE 4 /* multiplier for rttvar; 2 bits */ 144 #define TCP_RTTVAR_SHIFT 2 /* multiplier for rttvar; 2 bits */ 145 146 /* 147 * The initial retransmission should happen at rtt + 4 * rttvar. 148 * Because of the way we do the smoothing, srtt and rttvar 149 * will each average +1/2 tick of bias. When we compute 150 * the retransmit timer, we want 1/2 tick of rounding and 151 * 1 extra tick because of +-1/2 tick uncertainty in the 152 * firing of the timer. The bias will give us exactly the 153 * 1.5 tick we need. But, because the bias is 154 * statistical, we have to test that we don't drop below 155 * the minimum feasible timer (which is 2 ticks). 156 * This macro assumes that the value of TCP_RTTVAR_SCALE 157 * is the same as the multiplier for rttvar. 158 */ 159 #define TCP_REXMTVAL(tp) (((tp)->t_srtt >> TCP_RTT_SHIFT) + (tp)->t_rttvar) 160 161 #endif 162