/* * Definitions for tcp compression routines. * * $Id: vjcompress.h,v 1.3 1996/05/28 00:55:33 paulus Exp $ * * Copyright (c) 1989 Regents of the University of California. * All rights reserved. * * Redistribution and use in source and binary forms are permitted * provided that the above copyright notice and this paragraph are * duplicated in all such forms and that any documentation, * advertising materials, and other materials related to such * distribution and use acknowledge that the software was developed * by the University of California, Berkeley.  The name of the * University may not be used to endorse or promote products derived * from this software without specific prior written permission. * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. * *	Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989: *	- Initial distribution. */#ifndef _VJCOMPRESS_H_#define _VJCOMPRESS_H_#define MAX_STATES 16		/* must be > 2 and < 256 */#define MAX_HDR	   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 state (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 */    } vjcs_u;};#define cs_ip vjcs_u.csu_ip#define cs_hdr vjcs_u.csu_hdr/* * all the state data for one serial line (we need one of these per line). */struct vjcompress {    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 VJ_NO_STATS    struct vjstat stats;#endif    struct cstate tstate[MAX_STATES];	/* xmit connection states */    struct cstate rstate[MAX_STATES];	/* receive connection states */};/* flag values */#define VJF_TOSS 1		/* tossing rcvd frames because of input err */extern void  vj_compress_init __P((struct vjcompress *comp, int max_state));extern u_int vj_compress_tcp __P((struct ip *ip, u_int mlen,				struct vjcompress *comp, int compress_cid_flag,				u_char **vjhdrp));extern void  vj_uncompress_err __P((struct vjcompress *comp));extern int   vj_uncompress_uncomp __P((u_char *buf, int buflen,				struct vjcompress *comp));extern int   vj_uncompress_tcp __P((u_char *buf, int buflen, int total_len,				struct vjcompress *comp, u_char **hdrp,				u_int *hlenp));#endif /* _VJCOMPRESS_H_ */