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 | |