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/*
* Definitions for tcp compression routines.
*
* $Header: /home/ncvs/src/usr.sbin/ppp/slcompress.h,v 1.3 1995/05/30 03:50:58 rgrimes 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.
*
* $FreeBSD$
*
* Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
* - Initial distribution.
*/
#include "cdefs.h"
#define MAX_STATES 16 /* must be > 2 and < 256 */
#define MAX_HDR 128 /* 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;
struct cstate tstate[MAX_STATES]; /* xmit connection states */
struct cstate rstate[MAX_STATES]; /* receive connection states */
};
struct slstat {
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 */
};
/* flag values */
#define SLF_TOSS 1 /* tossing rcvd frames because of input err */
extern void sl_compress_init __P((struct slcompress *));
extern u_char sl_compress_tcp __P((struct mbuf *, struct ip *,
struct slcompress *, int compress_cid_flag));
extern int sl_uncompress_tcp __P((u_char **, int, u_int, struct slcompress *));
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