lib/drivers/lwip/src/netif/ppp/vj.h

   1 /*
   2  * Definitions for tcp compression routines.
   3  *
   4  * $Id: vj.h,v 1.5 2007/12/19 20:47:23 fbernon 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 "vjbsdhdr.h"
  29
  30 #define MAX_SLOTS 16 /* must be > 2 and < 256 */
  31 #define MAX_HDR   128
  32
  33 /*
  34  * Compressed packet format:
  35  *
  36  * The first octet contains the packet type (top 3 bits), TCP
  37  * 'push' bit, and flags that indicate which of the 4 TCP sequence
  38  * numbers have changed (bottom 5 bits).  The next octet is a
  39  * conversation number that associates a saved IP/TCP header with
  40  * the compressed packet.  The next two octets are the TCP checksum
  41  * from the original datagram.  The next 0 to 15 octets are
  42  * sequence number changes, one change per bit set in the header
  43  * (there may be no changes and there are two special cases where
  44  * the receiver implicitly knows what changed -- see below).
  45  *
  46  * There are 5 numbers which can change (they are always inserted
  47  * in the following order): TCP urgent pointer, window,
  48  * acknowlegement, sequence number and IP ID.  (The urgent pointer
  49  * is different from the others in that its value is sent, not the
  50  * change in value.)  Since typical use of SLIP links is biased
  51  * toward small packets (see comments on MTU/MSS below), changes
  52  * use a variable length coding with one octet for numbers in the
  53  * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the
  54  * range 256 - 65535 or 0.  (If the change in sequence number or
  55  * ack is more than 65535, an uncompressed packet is sent.)
  56  */
  57
  58 /*
  59  * Packet types (must not conflict with IP protocol version)
  60  *
  61  * The top nibble of the first octet is the packet type.  There are
  62  * three possible types: IP (not proto TCP or tcp with one of the
  63  * control flags set); uncompressed TCP (a normal IP/TCP packet but
  64  * with the 8-bit protocol field replaced by an 8-bit connection id --
  65  * this type of packet syncs the sender & receiver); and compressed
  66  * TCP (described above).
  67  *
  68  * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and
  69  * is logically part of the 4-bit "changes" field that follows.  Top
  70  * three bits are actual packet type.  For backward compatibility
  71  * and in the interest of conserving bits, numbers are chosen so the
  72  * IP protocol version number (4) which normally appears in this nibble
  73  * means "IP packet".
  74  */
  75
  76 /* packet types */
  77 #define TYPE_IP               0x40
  78 #define TYPE_UNCOMPRESSED_TCP 0x70
  79 #define TYPE_COMPRESSED_TCP   0x80
  80 #define TYPE_ERROR            0x00
  81
  82 /* Bits in first octet of compressed packet */
  83 #define NEW_C 0x40 /* flag bits for what changed in a packet */
  84 #define NEW_I 0x20
  85 #define NEW_S 0x08
  86 #define NEW_A 0x04
  87 #define NEW_W 0x02
  88 #define NEW_U 0x01
  89
  90 /* reserved, special-case values of above */
  91 #define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */
  92 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */
  93 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U)
  94
  95 #define TCP_PUSH_BIT 0x10
  96
  97
  98 /*
  99  * "state" data for each active tcp conversation on the wire.  This is
 100  * basically a copy of the entire IP/TCP header from the last packet
 101  * we saw from the conversation together with a small identifier
 102  * the transmit & receive ends of the line use to locate saved header.
 103  */
 104 struct cstate {
 105   struct cstate *cs_next; /* next most recently used state (xmit only) */
 106   u_short cs_hlen;        /* size of hdr (receive only) */
 107   u_char cs_id;           /* connection # associated with this state */
 108   u_char cs_filler;
 109   union {
 110     char csu_hdr[MAX_HDR];
 111     struct ip csu_ip;     /* ip/tcp hdr from most recent packet */
 112   } vjcs_u;
 113 };
 114 #define cs_ip vjcs_u.csu_ip
 115 #define cs_hdr vjcs_u.csu_hdr
 116
 117
 118 struct vjstat {
 119   unsigned long vjs_packets;        /* outbound packets */
 120   unsigned long vjs_compressed;     /* outbound compressed packets */
 121   unsigned long vjs_searches;       /* searches for connection state */
 122   unsigned long vjs_misses;         /* times couldn't find conn. state */
 123   unsigned long vjs_uncompressedin; /* inbound uncompressed packets */
 124   unsigned long vjs_compressedin;   /* inbound compressed packets */
 125   unsigned long vjs_errorin;        /* inbound unknown type packets */
 126   unsigned long vjs_tossed;         /* inbound packets tossed because of error */
 127 };
 128
 129 /*
 130  * all the state data for one serial line (we need one of these per line).
 131  */
 132 struct vjcompress {
 133   struct cstate *last_cs;          /* most recently used tstate */
 134   u_char last_recv;                /* last rcvd conn. id */
 135   u_char last_xmit;                /* last sent conn. id */
 136   u_short flags;
 137   u_char maxSlotIndex;
 138   u_char compressSlot;             /* Flag indicating OK to compress slot ID. */
 139 #if LINK_STATS
 140   struct vjstat stats;
 141 #endif
 142   struct cstate tstate[MAX_SLOTS]; /* xmit connection states */
 143   struct cstate rstate[MAX_SLOTS]; /* receive connection states */
 144 };
 145
 146 /* flag values */
 147 #define VJF_TOSS 1U /* tossing rcvd frames because of input err */
 148
 149 extern void  vj_compress_init    (struct vjcompress *comp);
 150 extern u_int vj_compress_tcp     (struct vjcompress *comp, struct pbuf *pb);
 151 extern void  vj_uncompress_err   (struct vjcompress *comp);
 152 extern int   vj_uncompress_uncomp(struct pbuf *nb, struct vjcompress *comp);
 153 extern int   vj_uncompress_tcp   (struct pbuf **nb, struct vjcompress *comp);
 154
 155 #endif /* VJ_H */