lib/liblwip/netif/ppp/vj.h

   1 /*
   2  * Definitions for tcp compression routines.
   3  *
   4  * $Id: vj.h,v 1.7 2010/02/22 17:52:09 goldsimon Exp $
   5  *
   6  * Copyright (c) 1989 Regents of the University of California.
   7  * All rights reserved.
   8  *
   9  * Redistribution and use in source and binary forms are permitted
  10  * provided that the above copyright notice and this paragraph are
  11  * duplicated in all such forms and that any documentation,
  12  * advertising materials, and other materials related to such
  13  * distribution and use acknowledge that the software was developed
  14  * by the University of California, Berkeley.  The name of the
  15  * University may not be used to endorse or promote products derived
  16  * from this software without specific prior written permission.
  17  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
  18  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
  19  * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  20  *
  21  * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
  22  * - Initial distribution.
  23  */
  24
  25 #ifndef VJ_H
  26 #define VJ_H
  27
  28 #include "lwip/ip.h"
  29 #include "lwip/tcp_impl.h"
  30
  31 #define MAX_SLOTS 16 /* must be > 2 and < 256 */
  32 #define MAX_HDR   128
  33
  34 /*
  35  * Compressed packet format:
  36  *
  37  * The first octet contains the packet type (top 3 bits), TCP
  38  * 'push' bit, and flags that indicate which of the 4 TCP sequence
  39  * numbers have changed (bottom 5 bits).  The next octet is a
  40  * conversation number that associates a saved IP/TCP header with
  41  * the compressed packet.  The next two octets are the TCP checksum
  42  * from the original datagram.  The next 0 to 15 octets are
  43  * sequence number changes, one change per bit set in the header
  44  * (there may be no changes and there are two special cases where
  45  * the receiver implicitly knows what changed -- see below).
  46  *
  47  * There are 5 numbers which can change (they are always inserted
  48  * in the following order): TCP urgent pointer, window,
  49  * acknowlegement, sequence number and IP ID.  (The urgent pointer
  50  * is different from the others in that its value is sent, not the
  51  * change in value.)  Since typical use of SLIP links is biased
  52  * toward small packets (see comments on MTU/MSS below), changes
  53  * use a variable length coding with one octet for numbers in the
  54  * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the
  55  * range 256 - 65535 or 0.  (If the change in sequence number or
  56  * ack is more than 65535, an uncompressed packet is sent.)
  57  */
  58
  59 /*
  60  * Packet types (must not conflict with IP protocol version)
  61  *
  62  * The top nibble of the first octet is the packet type.  There are
  63  * three possible types: IP (not proto TCP or tcp with one of the
  64  * control flags set); uncompressed TCP (a normal IP/TCP packet but
  65  * with the 8-bit protocol field replaced by an 8-bit connection id --
  66  * this type of packet syncs the sender & receiver); and compressed
  67  * TCP (described above).
  68  *
  69  * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and
  70  * is logically part of the 4-bit "changes" field that follows.  Top
  71  * three bits are actual packet type.  For backward compatibility
  72  * and in the interest of conserving bits, numbers are chosen so the
  73  * IP protocol version number (4) which normally appears in this nibble
  74  * means "IP packet".
  75  */
  76
  77 /* packet types */
  78 #define TYPE_IP               0x40
  79 #define TYPE_UNCOMPRESSED_TCP 0x70
  80 #define TYPE_COMPRESSED_TCP   0x80
  81 #define TYPE_ERROR            0x00
  82
  83 /* Bits in first octet of compressed packet */
  84 #define NEW_C 0x40 /* flag bits for what changed in a packet */
  85 #define NEW_I 0x20
  86 #define NEW_S 0x08
  87 #define NEW_A 0x04
  88 #define NEW_W 0x02
  89 #define NEW_U 0x01
  90
  91 /* reserved, special-case values of above */
  92 #define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */
  93 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */
  94 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U)
  95
  96 #define TCP_PUSH_BIT 0x10
  97
  98
  99 /*
 100  * "state" data for each active tcp conversation on the wire.  This is
 101  * basically a copy of the entire IP/TCP header from the last packet
 102  * we saw from the conversation together with a small identifier
 103  * the transmit & receive ends of the line use to locate saved header.
 104  */
 105 struct cstate {
 106   struct cstate *cs_next; /* next most recently used state (xmit only) */
 107   u_short cs_hlen;        /* size of hdr (receive only) */
 108   u_char cs_id;           /* connection # associated with this state */
 109   u_char cs_filler;
 110   union {
 111     char csu_hdr[MAX_HDR];
 112     struct ip_hdr csu_ip;     /* ip/tcp hdr from most recent packet */
 113   } vjcs_u;
 114 };
 115 #define cs_ip vjcs_u.csu_ip
 116 #define cs_hdr vjcs_u.csu_hdr
 117
 118
 119 struct vjstat {
 120   unsigned long vjs_packets;        /* outbound packets */
 121   unsigned long vjs_compressed;     /* outbound compressed packets */
 122   unsigned long vjs_searches;       /* searches for connection state */
 123   unsigned long vjs_misses;         /* times couldn't find conn. state */
 124   unsigned long vjs_uncompressedin; /* inbound uncompressed packets */
 125   unsigned long vjs_compressedin;   /* inbound compressed packets */
 126   unsigned long vjs_errorin;        /* inbound unknown type packets */
 127   unsigned long vjs_tossed;         /* inbound packets tossed because of error */
 128 };
 129
 130 /*
 131  * all the state data for one serial line (we need one of these per line).
 132  */
 133 struct vjcompress {
 134   struct cstate *last_cs;          /* most recently used tstate */
 135   u_char last_recv;                /* last rcvd conn. id */
 136   u_char last_xmit;                /* last sent conn. id */
 137   u_short flags;
 138   u_char maxSlotIndex;
 139   u_char compressSlot;             /* Flag indicating OK to compress slot ID. */
 140 #if LINK_STATS
 141   struct vjstat stats;
 142 #endif
 143   struct cstate tstate[MAX_SLOTS]; /* xmit connection states */
 144   struct cstate rstate[MAX_SLOTS]; /* receive connection states */
 145 };
 146
 147 /* flag values */
 148 #define VJF_TOSS 1U /* tossing rcvd frames because of input err */
 149
 150 extern void  vj_compress_init    (struct vjcompress *comp);
 151 extern u_int vj_compress_tcp     (struct vjcompress *comp, struct pbuf *pb);
 152 extern void  vj_uncompress_err   (struct vjcompress *comp);
 153 extern int   vj_uncompress_uncomp(struct pbuf *nb, struct vjcompress *comp);
 154 extern int   vj_uncompress_tcp   (struct pbuf **nb, struct vjcompress *comp);
 155
 156 #endif /* VJ_H */