/* | |
* Definitions for tcp compression routines. | |
* | |
* $Id: vj.h,v 1.5 2007/12/19 20:47:23 fbernon 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 VJ_H | |
#define VJ_H | |
#include "vjbsdhdr.h" | |
#define MAX_SLOTS 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 | |
struct vjstat { | |
unsigned long vjs_packets; /* outbound packets */ | |
unsigned long vjs_compressed; /* outbound compressed packets */ | |
unsigned long vjs_searches; /* searches for connection state */ | |
unsigned long vjs_misses; /* times couldn't find conn. state */ | |
unsigned long vjs_uncompressedin; /* inbound uncompressed packets */ | |
unsigned long vjs_compressedin; /* inbound compressed packets */ | |
unsigned long vjs_errorin; /* inbound unknown type packets */ | |
unsigned long vjs_tossed; /* inbound packets tossed because of error */ | |
}; | |
/* | |
* 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; | |
u_char maxSlotIndex; | |
u_char compressSlot; /* Flag indicating OK to compress slot ID. */ | |
#if LINK_STATS | |
struct vjstat stats; | |
#endif | |
struct cstate tstate[MAX_SLOTS]; /* xmit connection states */ | |
struct cstate rstate[MAX_SLOTS]; /* receive connection states */ | |
}; | |
/* flag values */ | |
#define VJF_TOSS 1U /* tossing rcvd frames because of input err */ | |
extern void vj_compress_init (struct vjcompress *comp); | |
extern u_int vj_compress_tcp (struct vjcompress *comp, struct pbuf *pb); | |
extern void vj_uncompress_err (struct vjcompress *comp); | |
extern int vj_uncompress_uncomp(struct pbuf *nb, struct vjcompress *comp); | |
extern int vj_uncompress_tcp (struct pbuf **nb, struct vjcompress *comp); | |
#endif /* VJ_H */ |