Annotation of sys/net/slcompress.h, Revision 1.1.1.1
1.1 nbrk 1: /* $OpenBSD: slcompress.h,v 1.7 2003/06/02 23:28:12 millert Exp $ */
2: /* $NetBSD: slcompress.h,v 1.11 1997/05/17 21:12:11 christos 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: #define MAX_STATES 16 /* must be > 2 and < 256 */
46: #define MAX_HDR MLEN /* XXX 4bsd-ism: should really be 128 */
47:
48: /*
49: * Compressed packet format:
50: *
51: * The first octet contains the packet type (top 3 bits), TCP
52: * 'push' bit, and flags that indicate which of the 4 TCP sequence
53: * numbers have changed (bottom 5 bits). The next octet is a
54: * conversation number that associates a saved IP/TCP header with
55: * the compressed packet. The next two octets are the TCP checksum
56: * from the original datagram. The next 0 to 15 octets are
57: * sequence number changes, one change per bit set in the header
58: * (there may be no changes and there are two special cases where
59: * the receiver implicitly knows what changed -- see below).
60: *
61: * There are 5 numbers which can change (they are always inserted
62: * in the following order): TCP urgent pointer, window,
63: * acknowledgement, sequence number and IP ID. (The urgent pointer
64: * is different from the others in that its value is sent, not the
65: * change in value.) Since typical use of SLIP links is biased
66: * toward small packets (see comments on MTU/MSS below), changes
67: * use a variable length coding with one octet for numbers in the
68: * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the
69: * range 256 - 65535 or 0. (If the change in sequence number or
70: * ack is more than 65535, an uncompressed packet is sent.)
71: */
72:
73: /*
74: * Packet types (must not conflict with IP protocol version)
75: *
76: * The top nibble of the first octet is the packet type. There are
77: * three possible types: IP (not proto TCP or tcp with one of the
78: * control flags set); uncompressed TCP (a normal IP/TCP packet but
79: * with the 8-bit protocol field replaced by an 8-bit connection id --
80: * this type of packet syncs the sender & receiver); and compressed
81: * TCP (described above).
82: *
83: * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and
84: * is logically part of the 4-bit "changes" field that follows. Top
85: * three bits are actual packet type. For backward compatibility
86: * and in the interest of conserving bits, numbers are chosen so the
87: * IP protocol version number (4) which normally appears in this nibble
88: * means "IP packet".
89: */
90:
91: /* packet types */
92: #define TYPE_IP 0x40
93: #define TYPE_UNCOMPRESSED_TCP 0x70
94: #define TYPE_COMPRESSED_TCP 0x80
95: #define TYPE_ERROR 0x00
96:
97: /* Bits in first octet of compressed packet */
98: #define NEW_C 0x40 /* flag bits for what changed in a packet */
99: #define NEW_I 0x20
100: #define NEW_S 0x08
101: #define NEW_A 0x04
102: #define NEW_W 0x02
103: #define NEW_U 0x01
104:
105: /* reserved, special-case values of above */
106: #define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */
107: #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */
108: #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U)
109:
110: #define TCP_PUSH_BIT 0x10
111:
112:
113: /*
114: * "state" data for each active tcp conversation on the wire. This is
115: * basically a copy of the entire IP/TCP header from the last packet
116: * we saw from the conversation together with a small identifier
117: * the transmit & receive ends of the line use to locate saved header.
118: */
119: struct cstate {
120: struct cstate *cs_next; /* next most recently used cstate (xmit only) */
121: u_int16_t cs_hlen; /* size of hdr (receive only) */
122: u_char cs_id; /* connection # associated with this state */
123: u_char cs_filler;
124: union {
125: char csu_hdr[MAX_HDR];
126: struct ip csu_ip; /* ip/tcp hdr from most recent packet */
127: } slcs_u;
128: };
129: #define cs_ip slcs_u.csu_ip
130: #define cs_hdr slcs_u.csu_hdr
131:
132: /*
133: * all the state data for one serial line (we need one of these
134: * per line).
135: */
136: struct slcompress {
137: struct cstate *last_cs; /* most recently used tstate */
138: u_char last_recv; /* last rcvd conn. id */
139: u_char last_xmit; /* last sent conn. id */
140: u_int16_t flags;
141: #ifndef SL_NO_STATS
142: int sls_packets; /* outbound packets */
143: int sls_compressed; /* outbound compressed packets */
144: int sls_searches; /* searches for connection state */
145: int sls_misses; /* times couldn't find conn. state */
146: int sls_uncompressedin; /* inbound uncompressed packets */
147: int sls_compressedin; /* inbound compressed packets */
148: int sls_errorin; /* inbound unknown type packets */
149: int sls_tossed; /* inbound packets tossed because of error */
150: #endif
151: struct cstate tstate[MAX_STATES]; /* xmit connection states */
152: struct cstate rstate[MAX_STATES]; /* receive connection states */
153: };
154: /* flag values */
155: #define SLF_TOSS 1 /* tossing rcvd frames because of input err */
156:
157: void sl_compress_init(struct slcompress *);
158: void sl_compress_setup(struct slcompress *, int);
159: u_int sl_compress_tcp(struct mbuf *,
160: struct ip *, struct slcompress *, int);
161: int sl_uncompress_tcp(u_char **, int, u_int, struct slcompress *);
162: int sl_uncompress_tcp_core(u_char *, int, int, u_int,
163: struct slcompress *, u_char **, u_int *);
164:
165: #endif /* _NET_SLCOMPRESS_H_ */
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