#ifndef _SLHC_H#define _SLHC_H/* * Definitions for tcp compression routines. * * $Header: slcompress.h,v 1.10 89/12/31 08:53:02 van 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. * * * modified for KA9Q Internet Software Package by * Katie Stevens (dkstevens@ucdavis.edu) * University of California, Davis * Computing Services *	- 01-31-90	initial adaptation * *	- Feb 1991	Bill_Simpson@um.cc.umich.edu *			variable number of conversation slots *			allow zero or one slots *			separate routines *			status display *//* * 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". *//* SLIP compression masks for len/vers byte */#define SL_TYPE_IP 0x40#define SL_TYPE_UNCOMPRESSED_TCP 0x70#define SL_TYPE_COMPRESSED_TCP 0x80#define SL_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/* * data type and sizes conversion assumptions: * *	VJ code		KA9Q style	generic *	u_char		byte_t		unsigned char	 8 bits *	u_short		int16		unsigned short	16 bits *	u_int		int16		unsigned short	16 bits *	u_long		unsigned long	unsigned long	32 bits *	int		int32		long		32 bits */typedef unsigned char byte_t;typedef unsigned long int32;/* * "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 {	byte_t	cs_this;	/* connection id number (xmit) */	struct cstate *next;	/* next in ring (xmit) */	struct iphdr cs_ip;	/* ip/tcp hdr from most recent packet */	struct tcphdr cs_tcp;	unsigned char cs_ipopt[64];	unsigned char cs_tcpopt[64];	int cs_hsize;};#define NULLSLSTATE	(struct cstate *)0/* * all the state data for one serial line (we need one of these per line). */struct slcompress {	struct cstate *tstate;	/* transmit connection states (array)*/	struct cstate *rstate;	/* receive connection states (array)*/	byte_t tslot_limit;	/* highest transmit slot id (0-l)*/	byte_t rslot_limit;	/* highest receive slot id (0-l)*/	byte_t xmit_oldest;	/* oldest xmit in ring */	byte_t xmit_current;	/* most recent xmit id */	byte_t recv_current;	/* most recent rcvd id */	byte_t flags;#define SLF_TOSS	0x01	/* tossing rcvd frames until id received */	int32 sls_o_nontcp;	/* outbound non-TCP packets */	int32 sls_o_tcp;	/* outbound TCP packets */	int32 sls_o_uncompressed;	/* outbound uncompressed packets */	int32 sls_o_compressed;	/* outbound compressed packets */	int32 sls_o_searches;	/* searches for connection state */	int32 sls_o_misses;	/* times couldn't find conn. state */	int32 sls_i_uncompressed;	/* inbound uncompressed packets */	int32 sls_i_compressed;	/* inbound compressed packets */	int32 sls_i_error;	/* inbound error packets */	int32 sls_i_tossed;	/* inbound packets tossed because of error */	int32 sls_i_runt;	int32 sls_i_badcheck;};#define NULLSLCOMPR	(struct slcompress *)0#define __ARGS(x) x/* In slhc.c: */struct slcompress *slhc_init __ARGS((int rslots, int tslots));void slhc_free __ARGS((struct slcompress *comp));int slhc_compress __ARGS((struct slcompress *comp, unsigned char *icp,			  int isize, unsigned char *ocp, unsigned char **cpp,			  int compress_cid));int slhc_uncompress __ARGS((struct slcompress *comp, unsigned char *icp,			    int isize));int slhc_remember __ARGS((struct slcompress *comp, unsigned char *icp,			  int isize));int slhc_toss __ARGS((struct slcompress *comp));void slhc_i_status __ARGS((struct slcompress *comp));void slhc_o_status __ARGS((struct slcompress *comp));#endif	/* _SLHC_H */