root/drivers/net/slhc.h

/* */

INCLUDED FROM

   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 MERCHANTIBILITY 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  * 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 /* SLIP compression masks for len/vers byte */
  84 #define SL_TYPE_IP 0x40
  85 #define SL_TYPE_UNCOMPRESSED_TCP 0x70
  86 #define SL_TYPE_COMPRESSED_TCP 0x80
  87 #define SL_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  * data type and sizes conversion assumptions:
 106  *
 107  *      VJ code         KA9Q style      generic
 108  *      u_char          byte_t          unsigned char    8 bits
 109  *      u_short         int16           unsigned short  16 bits
 110  *      u_int           int16           unsigned short  16 bits
 111  *      u_long          unsigned long   unsigned long   32 bits
 112  *      int             int32           long            32 bits
 113  */
 114 
 115 typedef unsigned char byte_t;
 116 typedef unsigned long int32;
 117 
 118 /*
 119  * "state" data for each active tcp conversation on the wire.  This is
 120  * basically a copy of the entire IP/TCP header from the last packet
 121  * we saw from the conversation together with a small identifier
 122  * the transmit & receive ends of the line use to locate saved header.
 123  */
 124 struct cstate {
 125         byte_t  cs_this;        /* connection id number (xmit) */
 126         struct cstate *next;    /* next in ring (xmit) */
 127         struct iphdr cs_ip;     /* ip/tcp hdr from most recent packet */
 128         struct tcphdr cs_tcp;
 129         unsigned char cs_ipopt[64];
 130         unsigned char cs_tcpopt[64];
 131         int cs_hsize;
 132 };
 133 #define NULLSLSTATE     (struct cstate *)0
 134 
 135 /*
 136  * all the state data for one serial line (we need one of these per line).
 137  */
 138 struct slcompress {
 139         struct cstate *tstate;  /* transmit connection states (array)*/
 140         struct cstate *rstate;  /* receive connection states (array)*/
 141 
 142         byte_t tslot_limit;     /* highest transmit slot id (0-l)*/
 143         byte_t rslot_limit;     /* highest receive slot id (0-l)*/
 144 
 145         byte_t xmit_oldest;     /* oldest xmit in ring */
 146         byte_t xmit_current;    /* most recent xmit id */
 147         byte_t recv_current;    /* most recent rcvd id */
 148 
 149         byte_t flags;
 150 #define SLF_TOSS        0x01    /* tossing rcvd frames until id received */
 151 
 152         int32 sls_o_nontcp;     /* outbound non-TCP packets */
 153         int32 sls_o_tcp;        /* outbound TCP packets */
 154         int32 sls_o_uncompressed;       /* outbound uncompressed packets */
 155         int32 sls_o_compressed; /* outbound compressed packets */
 156         int32 sls_o_searches;   /* searches for connection state */
 157         int32 sls_o_misses;     /* times couldn't find conn. state */
 158 
 159         int32 sls_i_uncompressed;       /* inbound uncompressed packets */
 160         int32 sls_i_compressed; /* inbound compressed packets */
 161         int32 sls_i_error;      /* inbound error packets */
 162         int32 sls_i_tossed;     /* inbound packets tossed because of error */
 163 
 164         int32 sls_i_runt;
 165         int32 sls_i_badcheck;
 166 };
 167 #define NULLSLCOMPR     (struct slcompress *)0
 168 
 169 #define __ARGS(x) x
 170 
 171 /* In slhc.c: */
 172 struct slcompress *slhc_init __ARGS((int rslots, int tslots));
 173 void slhc_free __ARGS((struct slcompress *comp));
 174 
 175 int slhc_compress __ARGS((struct slcompress *comp, unsigned char *icp,
 176                           int isize, unsigned char *ocp, unsigned char **cpp,
 177                           int compress_cid));
 178 int slhc_uncompress __ARGS((struct slcompress *comp, unsigned char *icp,
 179                             int isize));
 180 int slhc_remember __ARGS((struct slcompress *comp, unsigned char *icp,
 181                           int isize));
 182 int slhc_toss __ARGS((struct slcompress *comp));
 183 
 184 void slhc_i_status __ARGS((struct slcompress *comp));
 185 void slhc_o_status __ARGS((struct slcompress *comp));
 186 
 187 #endif  /* _SLHC_H */

/* */