1/*
  2 * Definitions for tcp compression routines.
  3 */
  4/*-
  5 * SPDX-License-Identifier: BSD-3-Clause
  6 *
  7 * Copyright (c) 1989, 1993
  8 *	The Regents of the University of California.  All rights reserved.
  9 *
 10 * Redistribution and use in source and binary forms, with or without
 11 * modification, are permitted provided that the following conditions
 12 * are met:
 13 * 1. Redistributions of source code must retain the above copyright
 14 *    notice, this list of conditions and the following disclaimer.
 15 * 2. Redistributions in binary form must reproduce the above copyright
 16 *    notice, this list of conditions and the following disclaimer in the
 17 *    documentation and/or other materials provided with the distribution.
 18 * 3. Neither the name of the University nor the names of its contributors
 19 *    may be used to endorse or promote products derived from this software
 20 *    without specific prior written permission.
 21 *
 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 25 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 32 * SUCH DAMAGE.
 33 *
 34 *	Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
 35 *	- Initial distribution.
 36 */
 37
 38#ifndef _NET_SLCOMPRESS_H_
 39#define _NET_SLCOMPRESS_H_
 40
 41#define MAX_STATES 16		/* must be > 2 and < 256 */
 42#define MAX_HDR 128
 43
 44/*
 45 * Compressed packet format:
 46 *
 47 * The first octet contains the packet type (top 3 bits), TCP
 48 * 'push' bit, and flags that indicate which of the 4 TCP sequence
 49 * numbers have changed (bottom 5 bits).  The next octet is a
 50 * conversation number that associates a saved IP/TCP header with
 51 * the compressed packet.  The next two octets are the TCP checksum
 52 * from the original datagram.  The next 0 to 15 octets are
 53 * sequence number changes, one change per bit set in the header
 54 * (there may be no changes and there are two special cases where
 55 * the receiver implicitly knows what changed -- see below).
 56 *
 57 * There are 5 numbers which can change (they are always inserted
 58 * in the following order): TCP urgent pointer, window,
 59 * acknowledgement, sequence number and IP ID.  (The urgent pointer
 60 * is different from the others in that its value is sent, not the
 61 * change in value.)  Since typical use of SLIP links is biased
 62 * toward small packets (see comments on MTU/MSS below), changes
 63 * use a variable length coding with one octet for numbers in the
 64 * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the
 65 * range 256 - 65535 or 0.  (If the change in sequence number or
 66 * ack is more than 65535, an uncompressed packet is sent.)
 67 */
 68
 69/*
 70 * Packet types (must not conflict with IP protocol version)
 71 *
 72 * The top nibble of the first octet is the packet type.  There are
 73 * three possible types: IP (not proto TCP or tcp with one of the
 74 * control flags set); uncompressed TCP (a normal IP/TCP packet but
 75 * with the 8-bit protocol field replaced by an 8-bit connection id --
 76 * this type of packet syncs the sender & receiver); and compressed
 77 * TCP (described above).
 78 *
 79 * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and
 80 * is logically part of the 4-bit "changes" field that follows.  Top
 81 * three bits are actual packet type.  For backward compatibility
 82 * and in the interest of conserving bits, numbers are chosen so the
 83 * IP protocol version number (4) which normally appears in this nibble
 84 * means "IP packet".
 85 */
 86
 87/* packet types */
 88#define TYPE_IP 0x40
 89#define TYPE_UNCOMPRESSED_TCP 0x70
 90#define TYPE_COMPRESSED_TCP 0x80
 91#define TYPE_ERROR 0x00
 92
 93/* Bits in first octet of compressed packet */
 94#define NEW_C	0x40	/* flag bits for what changed in a packet */
 95#define NEW_I	0x20
 96#define NEW_S	0x08
 97#define NEW_A	0x04
 98#define NEW_W	0x02
 99#define NEW_U	0x01
100
101/* reserved, special-case values of above */
102#define SPECIAL_I (NEW_S|NEW_W|NEW_U)		/* echoed interactive traffic */
103#define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U)	/* unidirectional data */
104#define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U)
105
106#define TCP_PUSH_BIT 0x10
107
108/*
109 * "state" data for each active tcp conversation on the wire.  This is
110 * basically a copy of the entire IP/TCP header from the last packet
111 * we saw from the conversation together with a small identifier
112 * the transmit & receive ends of the line use to locate saved header.
113 */
114struct cstate {
115	struct cstate *cs_next;	/* next most recently used cstate (xmit only) */
116	u_int16_t cs_hlen;	/* size of hdr (receive only) */
117	u_char cs_id;		/* connection # associated with this state */
118	u_char cs_filler;
119	union {
120		char csu_hdr[MAX_HDR];
121		struct ip csu_ip;	/* ip/tcp hdr from most recent packet */
122	} slcs_u;
123};
124#define cs_ip slcs_u.csu_ip
125#define cs_hdr slcs_u.csu_hdr
126
127/*
128 * all the state data for one serial line (we need one of these
129 * per line).
130 */
131struct slcompress {
132	struct cstate *last_cs;	/* most recently used tstate */
133	u_char last_recv;	/* last rcvd conn. id */
134	u_char last_xmit;	/* last sent conn. id */
135	u_int16_t flags;
136#ifndef SL_NO_STATS
137	int sls_packets;	/* outbound packets */
138	int sls_compressed;	/* outbound compressed packets */
139	int sls_searches;	/* searches for connection state */
140	int sls_misses;		/* times couldn't find conn. state */
141	int sls_uncompressedin;	/* inbound uncompressed packets */
142	int sls_compressedin;	/* inbound compressed packets */
143	int sls_errorin;	/* inbound unknown type packets */
144	int sls_tossed;		/* inbound packets tossed because of error */
145#endif
146	struct cstate tstate[MAX_STATES];	/* xmit connection states */
147	struct cstate rstate[MAX_STATES];	/* receive connection states */
148};
149/* flag values */
150#define SLF_TOSS 1		/* tossing rcvd frames because of input err */
151
152void	 sl_compress_init(struct slcompress *, int);
153u_int	 sl_compress_tcp(struct mbuf *, struct ip *, struct slcompress *, int);
154int	 sl_uncompress_tcp(u_char **, int, u_int, struct slcompress *);
155int	 sl_uncompress_tcp_core(u_char *, int, int, u_int,
156	    struct slcompress *, u_char **, u_int *);
157
158#endif /* !_NET_SLCOMPRESS_H_ */