FreeBSD/Linux Kernel Cross Reference
sys/net/slcompress.h
1 /* $NetBSD: slcompress.h,v 1.20 2020/03/05 07:46:36 riastradh Exp $ */
2 /* Id: slcompress.h,v 1.4 1994/09/21 06:50:08 paulus Exp */
3
4 /*
5 * Copyright (c) 1989, 1993
6 * The Regents of the University of California. All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the University nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 *
32 * @(#)slcompress.h 8.1 (Berkeley) 6/10/93
33 */
34
35 /*
36 * Definitions for tcp compression routines.
37 *
38 * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
39 * - Initial distribution.
40 */
41
42 #ifndef _NET_SLCOMPRESS_H_
43 #define _NET_SLCOMPRESS_H_
44
45 #ifdef _KERNEL_OPT
46 #include "opt_inet.h"
47 #endif
48
49 #define MAX_STATES 16 /* must be > 2 and < 256 */
50 #define MAX_HDR MLEN /* XXX 4bsd-ism: should really be 128 */
51
52 /*
53 * Compressed packet format:
54 *
55 * The first octet contains the packet type (top 3 bits), TCP
56 * 'push' bit, and flags that indicate which of the 4 TCP sequence
57 * numbers have changed (bottom 5 bits). The next octet is a
58 * conversation number that associates a saved IP/TCP header with
59 * the compressed packet. The next two octets are the TCP checksum
60 * from the original datagram. The next 0 to 15 octets are
61 * sequence number changes, one change per bit set in the header
62 * (there may be no changes and there are two special cases where
63 * the receiver implicitly knows what changed -- see below).
64 *
65 * There are 5 numbers which can change (they are always inserted
66 * in the following order): TCP urgent pointer, window,
67 * acknowledgement, sequence number and IP ID. (The urgent pointer
68 * is different from the others in that its value is sent, not the
69 * change in value.) Since typical use of SLIP links is biased
70 * toward small packets (see comments on MTU/MSS below), changes
71 * use a variable length coding with one octet for numbers in the
72 * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the
73 * range 256 - 65535 or 0. (If the change in sequence number or
74 * ack is more than 65535, an uncompressed packet is sent.)
75 */
76
77 /*
78 * Packet types (must not conflict with IP protocol version)
79 *
80 * The top nibble of the first octet is the packet type. There are
81 * three possible types: IP (not proto TCP or tcp with one of the
82 * control flags set); uncompressed TCP (a normal IP/TCP packet but
83 * with the 8-bit protocol field replaced by an 8-bit connection id --
84 * this type of packet syncs the sender & receiver); and compressed
85 * TCP (described above).
86 *
87 * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and
88 * is logically part of the 4-bit "changes" field that follows. Top
89 * three bits are actual packet type. For backward compatibility
90 * and in the interest of conserving bits, numbers are chosen so the
91 * IP protocol version number (4) which normally appears in this nibble
92 * means "IP packet".
93 */
94
95 /* packet types */
96 #define TYPE_IP 0x40
97 #define TYPE_UNCOMPRESSED_TCP 0x70
98 #define TYPE_COMPRESSED_TCP 0x80
99 #define TYPE_ERROR 0x00
100
101 /* Bits in first octet of compressed packet */
102 #define NEW_C 0x40 /* flag bits for what changed in a packet */
103 #define NEW_I 0x20
104 #define NEW_S 0x08
105 #define NEW_A 0x04
106 #define NEW_W 0x02
107 #define NEW_U 0x01
108
109 /* reserved, special-case values of above */
110 #define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */
111 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */
112 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U)
113
114 #define TCP_PUSH_BIT 0x10
115
116
117 /*
118 * "state" data for each active tcp conversation on the wire. This is
119 * basically a copy of the entire IP/TCP header from the last packet
120 * we saw from the conversation together with a small identifier
121 * the transmit & receive ends of the line use to locate saved header.
122 */
123 struct cstate {
124 struct cstate *cs_next; /* next most recently used cstate (xmit only) */
125 uint16_t cs_hlen; /* size of hdr (receive only) */
126 u_char cs_id; /* connection # associated with this state */
127 u_char cs_filler;
128 union {
129 char csu_hdr[MAX_HDR];
130 #ifdef INET
131 struct ip csu_ip; /* ip/tcp hdr from most recent packet */
132 #endif
133 } slcs_u;
134 };
135 #define cs_ip slcs_u.csu_ip
136 #define cs_hdr slcs_u.csu_hdr
137
138 /*
139 * all the state data for one serial line (we need one of these
140 * per line).
141 */
142 struct slcompress {
143 struct cstate *last_cs; /* most recently used tstate */
144 u_char last_recv; /* last rcvd conn. id */
145 u_char last_xmit; /* last sent conn. id */
146 uint16_t flags;
147 #ifndef SL_NO_STATS
148 int sls_packets; /* outbound packets */
149 int sls_compressed; /* outbound compressed packets */
150 int sls_searches; /* searches for connection state */
151 int sls_misses; /* times couldn't find conn. state */
152 int sls_uncompressedin; /* inbound uncompressed packets */
153 int sls_compressedin; /* inbound compressed packets */
154 int sls_errorin; /* inbound unknown type packets */
155 int sls_tossed; /* inbound packets tossed because of error */
156 #endif
157 struct cstate tstate[MAX_STATES]; /* xmit connection states */
158 struct cstate rstate[MAX_STATES]; /* receive connection states */
159 };
160 /* flag values */
161 #define SLF_TOSS 1 /* tossing rcvd frames because of input err */
162
163 void sl_compress_init(struct slcompress *);
164 void sl_compress_setup(struct slcompress *, int);
165 #ifdef INET
166 u_int sl_compress_tcp(struct mbuf *,
167 struct ip *, struct slcompress *, int);
168 #endif
169 int sl_uncompress_tcp(u_char **, int, u_int, struct slcompress *);
170 int sl_uncompress_tcp_core(u_char *, int, int, u_int,
171 struct slcompress *, u_char **, u_int *);
172
173 #endif /* !_NET_SLCOMPRESS_H_ */
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