usr.sbin/ppp/slcompress.h

   1 /*
   2  * Definitions for tcp compression routines.
   3  *
   4  * Copyright (c) 1989 Regents of the University of California.
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms are permitted
   8  * provided that the above copyright notice and this paragraph are
   9  * duplicated in all such forms and that any documentation,
  10  * advertising materials, and other materials related to such
  11  * distribution and use acknowledge that the software was developed
  12  * by the University of California, Berkeley.  The name of the
  13  * University may not be used to endorse or promote products derived
  14  * from this software without specific prior written permission.
  15  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
  16  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
  17  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  18  *
  19  * $FreeBSD: src/usr.sbin/ppp/slcompress.h,v 1.13 1999/08/28 01:18:44 peter Exp $
  20  *
  21  *      Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
  22  *      - Initial distribution.
  23  */
  24
  25 #define MIN_VJ_STATES 3
  26 #define MAX_VJ_STATES 255
  27 #define DEF_VJ_STATES 16                /* must be > 2 and < 256 */
  28 #define MAX_HDR 128
  29
  30 /*
  31  * Compressed packet format:
  32  *
  33  * The first octet contains the packet type (top 3 bits), TCP
  34  * 'push' bit, and flags that indicate which of the 4 TCP sequence
  35  * numbers have changed (bottom 5 bits).  The next octet is a
  36  * conversation number that associates a saved IP/TCP header with
  37  * the compressed packet.  The next two octets are the TCP checksum
  38  * from the original datagram.  The next 0 to 15 octets are
  39  * sequence number changes, one change per bit set in the header
  40  * (there may be no changes and there are two special cases where
  41  * the receiver implicitly knows what changed -- see below).
  42  *
  43  * There are 5 numbers which can change (they are always inserted
  44  * in the following order): TCP urgent pointer, window,
  45  * acknowlegement, sequence number and IP ID.  (The urgent pointer
  46  * is different from the others in that its value is sent, not the
  47  * change in value.)  Since typical use of SLIP links is biased
  48  * toward small packets (see comments on MTU/MSS below), changes
  49  * use a variable length coding with one octet for numbers in the
  50  * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the
  51  * range 256 - 65535 or 0.  (If the change in sequence number or
  52  * ack is more than 65535, an uncompressed packet is sent.)
  53  */
  54
  55 /*
  56  * Packet types (must not conflict with IP protocol version)
  57  *
  58  * The top nibble of the first octet is the packet type.  There are
  59  * three possible types: IP (not proto TCP or tcp with one of the
  60  * control flags set); uncompressed TCP (a normal IP/TCP packet but
  61  * with the 8-bit protocol field replaced by an 8-bit connection id --
  62  * this type of packet syncs the sender & receiver); and compressed
  63  * TCP (described above).
  64  *
  65  * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and
  66  * is logically part of the 4-bit "changes" field that follows.  Top
  67  * three bits are actual packet type.  For backward compatibility
  68  * and in the interest of conserving bits, numbers are chosen so the
  69  * IP protocol version number (4) which normally appears in this nibble
  70  * means "IP packet".
  71  */
  72
  73 /* packet types */
  74 #define TYPE_IP 0x40
  75 #define TYPE_UNCOMPRESSED_TCP 0x70
  76 #define TYPE_COMPRESSED_TCP 0x80
  77 #define TYPE_ERROR 0x00
  78
  79 /* Bits in first octet of compressed packet */
  80 #define NEW_C   0x40            /* flag bits for what changed in a packet */
  81 #define NEW_I   0x20
  82 #define NEW_S   0x08
  83 #define NEW_A   0x04
  84 #define NEW_W   0x02
  85 #define NEW_U   0x01
  86
  87 /* reserved, special-case values of above */
  88 #define SPECIAL_I (NEW_S|NEW_W|NEW_U)   /* echoed interactive traffic */
  89 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U)     /* unidirectional data */
  90 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U)
  91
  92 #define TCP_PUSH_BIT 0x10
  93
  94 /*
  95  * "state" data for each active tcp conversation on the wire.  This is
  96  * basically a copy of the entire IP/TCP header from the last packet
  97  * we saw from the conversation together with a small identifier
  98  * the transmit & receive ends of the line use to locate saved header.
  99  */
 100 struct cstate {
 101   struct cstate *cs_next;       /* next most recently used cstate (xmit only) */
 102   u_short cs_hlen;              /* size of hdr (receive only) */
 103   u_char cs_id;                 /* connection # associated with this state */
 104   u_char cs_filler;
 105   union {
 106     char csu_hdr[MAX_HDR];
 107     struct ip csu_ip;           /* ip/tcp hdr from most recent packet */
 108   } slcs_u;
 109 };
 110
 111 #define cs_ip slcs_u.csu_ip
 112 #define cs_hdr slcs_u.csu_hdr
 113
 114 /*
 115  * all the state data for one serial line (we need one of these
 116  * per line).
 117  */
 118 struct slcompress {
 119   struct cstate *last_cs;       /* most recently used tstate */
 120   u_char last_recv;             /* last rcvd conn. id */
 121   u_char last_xmit;             /* last sent conn. id */
 122   u_short flags;
 123   struct cstate tstate[MAX_VJ_STATES];  /* xmit connection states */
 124   struct cstate rstate[MAX_VJ_STATES];  /* receive connection states */
 125 };
 126
 127 struct slstat {
 128   int sls_packets;              /* outbound packets */
 129   int sls_compressed;           /* outbound compressed packets */
 130   int sls_searches;             /* searches for connection state */
 131   int sls_misses;               /* times couldn't find conn. state */
 132   int sls_uncompressedin;       /* inbound uncompressed packets */
 133   int sls_compressedin;         /* inbound compressed packets */
 134   int sls_errorin;              /* inbound unknown type packets */
 135   int sls_tossed;               /* inbound packets tossed because of error */
 136 };
 137
 138 /* flag values */
 139 #define SLF_TOSS 1              /* tossing rcvd frames because of input err */
 140
 141 struct mbuf;
 142 struct cmdargs;
 143
 144 extern void sl_compress_init(struct slcompress *, int);
 145 extern u_char sl_compress_tcp(struct mbuf *, struct ip *, struct slcompress *,
 146                               struct slstat *, int);
 147 extern int sl_uncompress_tcp(u_char **, int, u_int, struct slcompress *,
 148                              struct slstat *, int);
 149 extern int sl_Show(struct cmdargs const *);