include/net/slhc_vj.h

   1 #ifndef _SLHC_H
   2 #define _SLHC_H
   3 /*
   4  * Definitions for tcp compression routines.
   5  *
   6  * $Header: slcompress.h,v 1.10 89/12/31 08:53:02 van Exp $
   7  *
   8  * Copyright (c) 1989 Regents of the University of California.
   9  * All rights reserved.
  10  *
  11  * Redistribution and use in source and binary forms are permitted
  12  * provided that the above copyright notice and this paragraph are
  13  * duplicated in all such forms and that any documentation,
  14  * advertising materials, and other materials related to such
  15  * distribution and use acknowledge that the software was developed
  16  * by the University of California, Berkeley.  The name of the
  17  * University may not be used to endorse or promote products derived
  18  * from this software without specific prior written permission.
  19  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
  20  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
  21  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  22  *
  23  *      Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
  24  *      - Initial distribution.
  25  *
  26  *
  27  * modified for KA9Q Internet Software Package by
  28  * Katie Stevens (dkstevens@ucdavis.edu)
  29  * University of California, Davis
  30  * Computing Services
  31  *      - 01-31-90      initial adaptation
  32  *
  33  *      - Feb 1991      Bill_Simpson@um.cc.umich.edu
  34  *                      variable number of conversation slots
  35  *                      allow zero or one slots
  36  *                      separate routines
  37  *                      status display
  38  */
  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  * acknowledgment, 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
  84 #include <linux/ip.h>
  85 #include <linux/tcp.h>
  86
  87 /* SLIP compression masks for len/vers byte */
  88 #define SL_TYPE_IP 0x40
  89 #define SL_TYPE_UNCOMPRESSED_TCP 0x70
  90 #define SL_TYPE_COMPRESSED_TCP 0x80
  91 #define SL_TYPE_ERROR 0x00
  92
  93 /* Bits in first octet of compressed packet */
  94 #define NEW_C   0x40    /* flag bits for what changed in a packet */
  95 #define NEW_I   0x20
  96 #define NEW_S   0x08
  97 #define NEW_A   0x04
  98 #define NEW_W   0x02
  99 #define NEW_U   0x01
 100
 101 /* reserved, special-case values of above */
 102 #define SPECIAL_I (NEW_S|NEW_W|NEW_U)           /* echoed interactive traffic */
 103 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U)     /* unidirectional data */
 104 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U)
 105
 106 #define TCP_PUSH_BIT 0x10
 107
 108 /*
 109  * data type and sizes conversion assumptions:
 110  *
 111  *      VJ code         KA9Q style      generic
 112  *      u_char          byte_t          unsigned char    8 bits
 113  *      u_short         int16           unsigned short  16 bits
 114  *      u_int           int16           unsigned short  16 bits
 115  *      u_long          unsigned long   unsigned long   32 bits
 116  *      int             int32           long            32 bits
 117  */
 118
 119 typedef __u8 byte_t;
 120 typedef __u32 int32;
 121
 122 /*
 123  * "state" data for each active tcp conversation on the wire.  This is
 124  * basically a copy of the entire IP/TCP header from the last packet
 125  * we saw from the conversation together with a small identifier
 126  * the transmit & receive ends of the line use to locate saved header.
 127  */
 128 struct cstate {
 129         byte_t  cs_this;        /* connection id number (xmit) */
 130         struct cstate *next;    /* next in ring (xmit) */
 131         struct iphdr cs_ip;     /* ip/tcp hdr from most recent packet */
 132         struct tcphdr cs_tcp;
 133         unsigned char cs_ipopt[64];
 134         unsigned char cs_tcpopt[64];
 135         int cs_hsize;
 136 };
 137 #define NULLSLSTATE     (struct cstate *)0
 138
 139 /*
 140  * all the state data for one serial line (we need one of these per line).
 141  */
 142 struct slcompress {
 143         struct cstate *tstate;  /* transmit connection states (array)*/
 144         struct cstate *rstate;  /* receive connection states (array)*/
 145
 146         byte_t tslot_limit;     /* highest transmit slot id (0-l)*/
 147         byte_t rslot_limit;     /* highest receive slot id (0-l)*/
 148
 149         byte_t xmit_oldest;     /* oldest xmit in ring */
 150         byte_t xmit_current;    /* most recent xmit id */
 151         byte_t recv_current;    /* most recent rcvd id */
 152
 153         byte_t flags;
 154 #define SLF_TOSS        0x01    /* tossing rcvd frames until id received */
 155
 156         int32 sls_o_nontcp;     /* outbound non-TCP packets */
 157         int32 sls_o_tcp;        /* outbound TCP packets */
 158         int32 sls_o_uncompressed;       /* outbound uncompressed packets */
 159         int32 sls_o_compressed; /* outbound compressed packets */
 160         int32 sls_o_searches;   /* searches for connection state */
 161         int32 sls_o_misses;     /* times couldn't find conn. state */
 162
 163         int32 sls_i_uncompressed;       /* inbound uncompressed packets */
 164         int32 sls_i_compressed; /* inbound compressed packets */
 165         int32 sls_i_error;      /* inbound error packets */
 166         int32 sls_i_tossed;     /* inbound packets tossed because of error */
 167
 168         int32 sls_i_runt;
 169         int32 sls_i_badcheck;
 170 };
 171 #define NULLSLCOMPR     (struct slcompress *)0
 172
 173 /* In slhc.c: */
 174 struct slcompress *slhc_init(int rslots, int tslots);
 175 void slhc_free(struct slcompress *comp);
 176
 177 int slhc_compress(struct slcompress *comp, unsigned char *icp, int isize,
 178                   unsigned char *ocp, unsigned char **cpp, int compress_cid);
 179 int slhc_uncompress(struct slcompress *comp, unsigned char *icp, int isize);
 180 int slhc_remember(struct slcompress *comp, unsigned char *icp, int isize);
 181 int slhc_toss(struct slcompress *comp);
 182
 183 #endif  /* _SLHC_H */