vj.h

00001 /*
00002  * Definitions for tcp compression routines.
00003  *
00004  * $Id: vj.h,v 1.7 2010/02/22 17:52:09 goldsimon Exp $
00005  *
00006  * Copyright (c) 1989 Regents of the University of California.
00007  * All rights reserved.
00008  *
00009  * Redistribution and use in source and binary forms are permitted
00010  * provided that the above copyright notice and this paragraph are
00011  * duplicated in all such forms and that any documentation,
00012  * advertising materials, and other materials related to such
00013  * distribution and use acknowledge that the software was developed
00014  * by the University of California, Berkeley.  The name of the
00015  * University may not be used to endorse or promote products derived
00016  * from this software without specific prior written permission.
00017  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
00018  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
00019  * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
00020  *
00021  * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
00022  * - Initial distribution.
00023  */
00024 
00025 #include "ppp_opts.h"
00026 #if PPP_SUPPORT && VJ_SUPPORT /* don't build if not configured for use in ppp_opts.h */
00027 
00028 #ifndef VJ_H
00029 #define VJ_H
00030 
00031 #ifdef __cplusplus
00032 extern "C" {
00033 #endif
00034 
00035 #define MAX_SLOTS 16 /* must be > 2 and < 256 */
00036 #define MAX_HDR   128
00037 
00038 /*
00039  * Compressed packet format:
00040  *
00041  * The first octet contains the packet type (top 3 bits), TCP
00042  * 'push' bit, and flags that indicate which of the 4 TCP sequence
00043  * numbers have changed (bottom 5 bits).  The next octet is a
00044  * conversation number that associates a saved IP/TCP header with
00045  * the compressed packet.  The next two octets are the TCP checksum
00046  * from the original datagram.  The next 0 to 15 octets are
00047  * sequence number changes, one change per bit set in the header
00048  * (there may be no changes and there are two special cases where
00049  * the receiver implicitly knows what changed -- see below).
00050  *
00051  * There are 5 numbers which can change (they are always inserted
00052  * in the following order): TCP urgent pointer, window,
00053  * acknowlegement, sequence number and IP ID.  (The urgent pointer
00054  * is different from the others in that its value is sent, not the
00055  * change in value.)  Since typical use of SLIP links is biased
00056  * toward small packets (see comments on MTU/MSS below), changes
00057  * use a variable length coding with one octet for numbers in the
00058  * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the
00059  * range 256 - 65535 or 0.  (If the change in sequence number or
00060  * ack is more than 65535, an uncompressed packet is sent.)
00061  */
00062 
00063 /*
00064  * Packet types (must not conflict with IP protocol version)
00065  *
00066  * The top nibble of the first octet is the packet type.  There are
00067  * three possible types: IP (not proto TCP or tcp with one of the
00068  * control flags set); uncompressed TCP (a normal IP/TCP packet but
00069  * with the 8-bit protocol field replaced by an 8-bit connection id --
00070  * this type of packet syncs the sender & receiver); and compressed
00071  * TCP (described above).
00072  *
00073  * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and
00074  * is logically part of the 4-bit "changes" field that follows.  Top
00075  * three bits are actual packet type.  For backward compatibility
00076  * and in the interest of conserving bits, numbers are chosen so the
00077  * IP protocol version number (4) which normally appears in this nibble
00078  * means "IP packet".
00079  */
00080 
00081 /* packet types */
00082 #define TYPE_IP               0x40
00083 #define TYPE_UNCOMPRESSED_TCP 0x70
00084 #define TYPE_COMPRESSED_TCP   0x80
00085 #define TYPE_ERROR            0x00
00086 
00087 /* Bits in first octet of compressed packet */
00088 #define NEW_C 0x40 /* flag bits for what changed in a packet */
00089 #define NEW_I 0x20
00090 #define NEW_S 0x08
00091 #define NEW_A 0x04
00092 #define NEW_W 0x02
00093 #define NEW_U 0x01
00094 
00095 /* reserved, special-case values of above */
00096 #define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */
00097 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */
00098 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U)
00099 
00100 #define TCP_PUSH_BIT 0x10
00101 
00102 
00103 /*
00104  * "state" data for each active tcp conversation on the wire.  This is
00105  * basically a copy of the entire IP/TCP header from the last packet
00106  * we saw from the conversation together with a small identifier
00107  * the transmit & receive ends of the line use to locate saved header.
00108  */
00109 struct cstate {
00110   struct cstate *cs_next; /* next most recently used state (xmit only) */
00111   u16_t cs_hlen;        /* size of hdr (receive only) */
00112   u8_t cs_id;           /* connection # associated with this state */
00113   u8_t cs_filler;
00114   union {
00115     char csu_hdr[MAX_HDR];
00116     struct ip_hdr csu_ip;     /* ip/tcp hdr from most recent packet */
00117   } vjcs_u;
00118 };
00119 #define cs_ip vjcs_u.csu_ip
00120 #define cs_hdr vjcs_u.csu_hdr
00121 
00122 
00123 struct vjstat {
00124   u32_t vjs_packets;        /* outbound packets */
00125   u32_t vjs_compressed;     /* outbound compressed packets */
00126   u32_t vjs_searches;       /* searches for connection state */
00127   u32_t vjs_misses;         /* times couldn't find conn. state */
00128   u32_t vjs_uncompressedin; /* inbound uncompressed packets */
00129   u32_t vjs_compressedin;   /* inbound compressed packets */
00130   u32_t vjs_errorin;        /* inbound unknown type packets */
00131   u32_t vjs_tossed;         /* inbound packets tossed because of error */
00132 };
00133 
00134 /*
00135  * all the state data for one serial line (we need one of these per line).
00136  */
00137 struct vjcompress {
00138   struct cstate *last_cs;          /* most recently used tstate */
00139   u8_t last_recv;                /* last rcvd conn. id */
00140   u8_t last_xmit;                /* last sent conn. id */
00141   u16_t flags;
00142   u8_t maxSlotIndex;
00143   u8_t compressSlot;             /* Flag indicating OK to compress slot ID. */
00144 #if LINK_STATS
00145   struct vjstat stats;
00146 #endif
00147   struct cstate tstate[MAX_SLOTS]; /* xmit connection states */
00148   struct cstate rstate[MAX_SLOTS]; /* receive connection states */
00149 };
00150 
00151 /* flag values */
00152 #define VJF_TOSS 1U /* tossing rcvd frames because of input err */
00153 
00154 extern void  vj_compress_init    (struct vjcompress *comp);
00155 extern u8_t  vj_compress_tcp     (struct vjcompress *comp, struct pbuf **pb);
00156 extern void  vj_uncompress_err   (struct vjcompress *comp);
00157 extern int   vj_uncompress_uncomp(struct pbuf *nb, struct vjcompress *comp);
00158 extern int   vj_uncompress_tcp   (struct pbuf **nb, struct vjcompress *comp);
00159 
00160 #ifdef __cplusplus
00161 }
00162 #endif
00163 
00164 #endif /* VJ_H */
00165 
00166 #endif /* PPP_SUPPORT && VJ_SUPPORT */