include/net/vjcompress.h

   1 /*
   2  * Definitions for tcp compression routines.
   3  *
   4  * $Id: vjcompress.h,v 1.3 1996/05/28 00:55:33 paulus Exp $
   5  *
   6  * Copyright (c) 2000 by Sun Microsystems, Inc.
   7  * All rights reserved.
   8  *
   9  * Copyright (c) 1989 Regents of the University of California.
  10  * All rights reserved.
  11  *
  12  * Redistribution and use in source and binary forms are permitted
  13  * provided that the above copyright notice and this paragraph are
  14  * duplicated in all such forms and that any documentation,
  15  * advertising materials, and other materials related to such
  16  * distribution and use acknowledge that the software was developed
  17  * by the University of California, Berkeley.  The name of the
  18  * University may not be used to endorse or promote products derived
  19  * from this software without specific prior written permission.
  20  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
  21  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
  22  * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  23  *
  24  *      Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
  25  *      - Initial distribution.
  26  */
  27
  28 #ifndef _VJCOMPRESS_H_
  29 #define _VJCOMPRESS_H_
  30
  31 #pragma ident   "%Z%%M% %I%     %E% SMI"
  32
  33 #ifdef __cplusplus
  34 extern "C" {
  35 #endif
  36
  37 #define MAX_STATES 16           /* must be > 2 and < 256 */
  38 #define MAX_HDR    128
  39
  40 /*
  41  * Compressed packet format:
  42  *
  43  * The first octet contains the packet type (top 3 bits), TCP
  44  * 'push' bit, and flags that indicate which of the 4 TCP sequence
  45  * numbers have changed (bottom 5 bits).  The next octet is a
  46  * conversation number that associates a saved IP/TCP header with
  47  * the compressed packet.  The next two octets are the TCP checksum
  48  * from the original datagram.  The next 0 to 15 octets are
  49  * sequence number changes, one change per bit set in the header
  50  * (there may be no changes and there are two special cases where
  51  * the receiver implicitly knows what changed -- see below).
  52  *
  53  * There are 5 numbers which can change (they are always inserted
  54  * in the following order): TCP urgent pointer, window,
  55  * acknowlegement, sequence number and IP ID.  (The urgent pointer
  56  * is different from the others in that its value is sent, not the
  57  * change in value.)  Since typical use of SLIP links is biased
  58  * toward small packets (see comments on MTU/MSS below), changes
  59  * use a variable length coding with one octet for numbers in the
  60  * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the
  61  * range 256 - 65535 or 0.  (If the change in sequence number or
  62  * ack is more than 65535, an uncompressed packet is sent.)
  63  */
  64
  65 /*
  66  * Packet types (must not conflict with IP protocol version)
  67  *
  68  * The top nibble of the first octet is the packet type.  There are
  69  * three possible types: IP (not proto TCP or tcp with one of the
  70  * control flags set); uncompressed TCP (a normal IP/TCP packet but
  71  * with the 8-bit protocol field replaced by an 8-bit connection id --
  72  * this type of packet syncs the sender & receiver); and compressed
  73  * TCP (described above).
  74  *
  75  * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and
  76  * is logically part of the 4-bit "changes" field that follows.  Top
  77  * three bits are actual packet type.  For backward compatibility
  78  * and in the interest of conserving bits, numbers are chosen so the
  79  * IP protocol version number (4) which normally appears in this nibble
  80  * means "IP packet".
  81  */
  82
  83 /* packet types */
  84 #define TYPE_IP 0x40
  85 #define TYPE_UNCOMPRESSED_TCP 0x70
  86 #define TYPE_COMPRESSED_TCP 0x80
  87 #define TYPE_ERROR 0x00
  88
  89 /* Bits in first octet of compressed packet */
  90 #define NEW_C   0x40    /* flag bits for what changed in a packet */
  91 #define NEW_I   0x20
  92 #define NEW_S   0x08
  93 #define NEW_A   0x04
  94 #define NEW_W   0x02
  95 #define NEW_U   0x01
  96
  97 /* reserved, special-case values of above */
  98 #define SPECIAL_I (NEW_S|NEW_W|NEW_U)           /* echoed interactive traffic */
  99 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U)     /* unidirectional data */
 100 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U)
 101
 102 #define TCP_PUSH_BIT 0x10
 103
 104
 105 /*
 106  * "state" data for each active tcp conversation on the wire.  This is
 107  * basically a copy of the entire IP/TCP header from the last packet
 108  * we saw from the conversation together with a small identifier
 109  * the transmit & receive ends of the line use to locate saved header.
 110  */
 111 struct cstate {
 112         struct cstate *cs_next; /* next most recently used state (xmit only) */
 113         ushort_t cs_hlen;       /* size of hdr (receive only) */
 114         uchar_t cs_id;          /* connection # associated with this state */
 115         uchar_t cs_filler;
 116         union {
 117                 char csu_hdr[MAX_HDR];
 118                 struct ip csu_ip; /* ip/tcp hdr from most recent packet */
 119         } vjcs_u;
 120 };
 121 #define cs_ip vjcs_u.csu_ip
 122 #define cs_hdr vjcs_u.csu_hdr
 123
 124 /*
 125  * all the state data for one serial line (we need one of these per line).
 126  */
 127 struct vjcompress {
 128         struct cstate *last_cs; /* most recently used tstate */
 129         uchar_t last_recv;              /* last rcvd conn. id */
 130         uchar_t last_xmit;              /* last sent conn. id */
 131         ushort_t flags;
 132 #ifndef VJ_NO_STATS
 133         struct vjstat stats;
 134 #endif
 135         struct cstate tstate[MAX_STATES];       /* xmit connection states */
 136         struct cstate rstate[MAX_STATES];       /* receive connection states */
 137 };
 138
 139 /* flag values */
 140 #define VJF_TOSS 1              /* tossing rcvd frames because of input err */
 141
 142 extern void  vj_compress_init __P((struct vjcompress *comp, int max_state));
 143 extern uint_t vj_compress_tcp __P((struct ip *ip, uint_t mlen,
 144                                 struct vjcompress *comp, int compress_cid_flag,
 145                                 uchar_t **vjhdrp));
 146 extern void  vj_uncompress_err __P((struct vjcompress *comp));
 147 extern int   vj_uncompress_uncomp __P((uchar_t *buf, int buflen,
 148                                 struct vjcompress *comp));
 149 extern int   vj_uncompress_tcp __P((uchar_t *buf, int buflen, int total_len,
 150                                 struct vjcompress *comp, uchar_t **hdrp,
 151                                 uint_t *hlenp));
 152
 153 #ifdef __cplusplus
 154 }
 155 #endif
 156
 157 #endif /* _VJCOMPRESS_H_ */