#define SL_NO_STATS

#ifndef _COMPRESS
#define _COMPRESS

#include "kernel.h"
#include "streams.h"
#include "f_ip.h"
#include "vanj.h"
#include "van_j.h"

/*
 * Definitions for tcp compression routines.
 * 
 * $Header: /usr/src/cvs/kernel/isdn/van_j/compress.h,v 1.2 1996/09/16 01:03:31 smurf 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.
 */

#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 cstate (xmit only) */
	ushort_t cs_hlen;			  /* size of hdr (receive only) */
	uchar_t cs_id;				  /* connection # associated with this state */
	uchar_t 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 compress {
	struct cstate *last_cs;		  /* most recently used tstate */
	uchar_t last_recv;			  /* last rcvd conn. id */
	uchar_t last_xmit;			  /* last sent conn. id */
	ushort_t 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 */

void compress_init (struct compress *);
ushort_t compress_tcp (struct compress *, mblk_t **);
void uncompress_tcp (struct compress *, mblk_t **, ushort_t);

#endif