1/*
2 * Definitions for tcp compression routines.
3 *
4 * Copyright (c) 1989, 1993
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 *    may be used to endorse or promote products derived from this software
17 *    without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 *
31 *	Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
32 *	- Initial distribution.
33 *
34 * $FreeBSD: releng/11.0/usr.sbin/ppp/slcompress.h 139979 2005-01-10 11:47:17Z brian $
35 */
36
37#define MIN_VJ_STATES 3
38#define MAX_VJ_STATES 255
39#define DEF_VJ_STATES 16		/* must be > 2 and < 256 */
40#define MAX_HDR 128
41
42/*
43 * Compressed packet format:
44 *
45 * The first octet contains the packet type (top 3 bits), TCP
46 * 'push' bit, and flags that indicate which of the 4 TCP sequence
47 * numbers have changed (bottom 5 bits).  The next octet is a
48 * conversation number that associates a saved IP/TCP header with
49 * the compressed packet.  The next two octets are the TCP checksum
50 * from the original datagram.  The next 0 to 15 octets are
51 * sequence number changes, one change per bit set in the header
52 * (there may be no changes and there are two special cases where
53 * the receiver implicitly knows what changed -- see below).
54 *
55 * There are 5 numbers which can change (they are always inserted
56 * in the following order): TCP urgent pointer, window,
57 * acknowlegement, sequence number and IP ID.  (The urgent pointer
58 * is different from the others in that its value is sent, not the
59 * change in value.)  Since typical use of SLIP links is biased
60 * toward small packets (see comments on MTU/MSS below), changes
61 * use a variable length coding with one octet for numbers in the
62 * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the
63 * range 256 - 65535 or 0.  (If the change in sequence number or
64 * ack is more than 65535, an uncompressed packet is sent.)
65 */
66
67/*
68 * Packet types (must not conflict with IP protocol version)
69 *
70 * The top nibble of the first octet is the packet type.  There are
71 * three possible types: IP (not proto TCP or tcp with one of the
72 * control flags set); uncompressed TCP (a normal IP/TCP packet but
73 * with the 8-bit protocol field replaced by an 8-bit connection id --
74 * this type of packet syncs the sender & receiver); and compressed
75 * TCP (described above).
76 *
77 * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and
78 * is logically part of the 4-bit "changes" field that follows.  Top
79 * three bits are actual packet type.  For backward compatibility
80 * and in the interest of conserving bits, numbers are chosen so the
81 * IP protocol version number (4) which normally appears in this nibble
82 * means "IP packet".
83 */
84
85/* packet types */
86#define TYPE_IP 0x40
87#define TYPE_UNCOMPRESSED_TCP 0x70
88#define TYPE_COMPRESSED_TCP 0x80
89#define TYPE_ERROR 0x00
90
91/* Bits in first octet of compressed packet */
92#define NEW_C	0x40		/* flag bits for what changed in a packet */
93#define NEW_I	0x20
94#define NEW_S	0x08
95#define NEW_A	0x04
96#define NEW_W	0x02
97#define NEW_U	0x01
98
99/* reserved, special-case values of above */
100#define SPECIAL_I (NEW_S|NEW_W|NEW_U)	/* echoed interactive traffic */
101#define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U)	/* unidirectional data */
102#define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U)
103
104#define TCP_PUSH_BIT 0x10
105
106/*
107 * "state" data for each active tcp conversation on the wire.  This is
108 * basically a copy of the entire IP/TCP header from the last packet
109 * we saw from the conversation together with a small identifier
110 * the transmit & receive ends of the line use to locate saved header.
111 */
112struct cstate {
113  struct cstate *cs_next;	/* next most recently used cstate (xmit only) */
114  u_short cs_hlen;		/* size of hdr (receive only) */
115  u_char cs_id;			/* connection # associated with this state */
116  u_char cs_filler;
117  union {
118    char csu_hdr[MAX_HDR];
119    struct ip csu_ip;		/* ip/tcp hdr from most recent packet */
120  } slcs_u;
121};
122
123#define cs_ip slcs_u.csu_ip
124#define cs_hdr slcs_u.csu_hdr
125
126/*
127 * all the state data for one serial line (we need one of these
128 * per line).
129 */
130struct slcompress {
131  struct cstate *last_cs;	/* most recently used tstate */
132  u_char last_recv;		/* last rcvd conn. id */
133  u_char last_xmit;		/* last sent conn. id */
134  u_short flags;
135  struct cstate tstate[MAX_VJ_STATES];	/* xmit connection states */
136  struct cstate rstate[MAX_VJ_STATES];	/* receive connection states */
137};
138
139struct slstat {
140  int sls_packets;		/* outbound packets */
141  int sls_compressed;		/* outbound compressed packets */
142  int sls_searches;		/* searches for connection state */
143  int sls_misses;		/* times couldn't find conn. state */
144  int sls_uncompressedin;	/* inbound uncompressed packets */
145  int sls_compressedin;		/* inbound compressed packets */
146  int sls_errorin;		/* inbound unknown type packets */
147  int sls_tossed;		/* inbound packets tossed because of error */
148};
149
150/* flag values */
151#define SLF_TOSS 1		/* tossing rcvd frames because of input err */
152
153struct mbuf;
154struct cmdargs;
155
156extern void sl_compress_init(struct slcompress *, int);
157extern u_char sl_compress_tcp(struct mbuf *, struct ip *, struct slcompress *,
158                              struct slstat *, int);
159extern int sl_uncompress_tcp(u_char **, int, u_int, struct slcompress *,
160                             struct slstat *, int);
161extern int sl_Show(struct cmdargs const *);
162