/* slcompress.h 7.4 90/06/28 */ /* * Definitions for tcp compression routines. * * $Header: /cvsroot/src/sys/net/slcompress.h,v 1.1.1.1 1993/03/21 09:45:37 cgd Exp $ * * Copyright (c) 1989 Regents of the University of California. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989: * - Initial distribution. */ #define MAX_STATES 16 /* must be > 2 and < 256 */ #define MAX_HDR MLEN /* XXX 4bsd-ism: should really be 128 */ /* * Compressed packet format: * * The first octet contains the packet type (top 3 bits), TCP * 'push' bit, and flags that indicate which of the 4 TCP sequence * numbers have changed (bottom 5 bits). The next octet is a * conversation number that associates a saved IP/TCP header with * the compressed packet. The next two octets are the TCP checksum * from the original datagram. The next 0 to 15 octets are * sequence number changes, one change per bit set in the header * (there may be no changes and there are two special cases where * the receiver implicitly knows what changed -- see below). * * There are 5 numbers which can change (they are always inserted * in the following order): TCP urgent pointer, window, * acknowlegement, sequence number and IP ID. (The urgent pointer * is different from the others in that its value is sent, not the * change in value.) Since typical use of SLIP links is biased * toward small packets (see comments on MTU/MSS below), changes * use a variable length coding with one octet for numbers in the * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the * range 256 - 65535 or 0. (If the change in sequence number or * ack is more than 65535, an uncompressed packet is sent.) */ /* * Packet types (must not conflict with IP protocol version) * * The top nibble of the first octet is the packet type. There are * three possible types: IP (not proto TCP or tcp with one of the * control flags set); uncompressed TCP (a normal IP/TCP packet but * with the 8-bit protocol field replaced by an 8-bit connection id -- * this type of packet syncs the sender & receiver); and compressed * TCP (described above). * * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and * is logically part of the 4-bit "changes" field that follows. Top * three bits are actual packet type. For backward compatibility * and in the interest of conserving bits, numbers are chosen so the * IP protocol version number (4) which normally appears in this nibble * means "IP packet". */ /* packet types */ #define TYPE_IP 0x40 #define TYPE_UNCOMPRESSED_TCP 0x70 #define TYPE_COMPRESSED_TCP 0x80 #define TYPE_ERROR 0x00 /* Bits in first octet of compressed packet */ #define NEW_C 0x40 /* flag bits for what changed in a packet */ #define NEW_I 0x20 #define NEW_S 0x08 #define NEW_A 0x04 #define NEW_W 0x02 #define NEW_U 0x01 /* reserved, special-case values of above */ #define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */ #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */ #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U) #define TCP_PUSH_BIT 0x10 /* * "state" data for each active tcp conversation on the wire. This is * basically a copy of the entire IP/TCP header from the last packet * we saw from the conversation together with a small identifier * the transmit & receive ends of the line use to locate saved header. */ struct cstate { struct cstate *cs_next; /* next most recently used cstate (xmit only) */ u_short cs_hlen; /* size of hdr (receive only) */ u_char cs_id; /* connection # associated with this state */ u_char cs_filler; union { char csu_hdr[MAX_HDR]; struct ip csu_ip; /* ip/tcp hdr from most recent packet */ } slcs_u; }; #define cs_ip slcs_u.csu_ip #define cs_hdr slcs_u.csu_hdr /* * all the state data for one serial line (we need one of these * per line). */ struct slcompress { struct cstate *last_cs; /* most recently used tstate */ u_char last_recv; /* last rcvd conn. id */ u_char last_xmit; /* last sent conn. id */ u_short flags; #ifndef SL_NO_STATS int sls_packets; /* outbound packets */ int sls_compressed; /* outbound compressed packets */ int sls_searches; /* searches for connection state */ int sls_misses; /* times couldn't find conn. state */ int sls_uncompressedin; /* inbound uncompressed packets */ int sls_compressedin; /* inbound compressed packets */ int sls_errorin; /* inbound unknown type packets */ int sls_tossed; /* inbound packets tossed because of error */ #endif struct cstate tstate[MAX_STATES]; /* xmit connection states */ struct cstate rstate[MAX_STATES]; /* receive connection states */ }; /* flag values */ #define SLF_TOSS 1 /* tossing rcvd frames because of input err */ extern void sl_compress_init(/* struct slcompress * */); extern u_char sl_compress_tcp(/* struct mbuf *, struct ip *, struct slcompress *, int compress_cid_flag */); extern int sl_uncompress_tcp(/* u_char **, int, u_char, struct slcompress * */);