00001 /* 00002 * Definitions for tcp compression routines. 00003 * 00004 * $Id: vj.h,v 1.5 2007/12/19 20:47:23 fbernon 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 #ifndef VJ_H 00026 #define VJ_H 00027 00028 #include "vjbsdhdr.h" 00029 00030 #define MAX_SLOTS 16 /* must be > 2 and < 256 */ 00031 #define MAX_HDR 128 00032 00033 /* 00034 * Compressed packet format: 00035 * 00036 * The first octet contains the packet type (top 3 bits), TCP 00037 * 'push' bit, and flags that indicate which of the 4 TCP sequence 00038 * numbers have changed (bottom 5 bits). The next octet is a 00039 * conversation number that associates a saved IP/TCP header with 00040 * the compressed packet. The next two octets are the TCP checksum 00041 * from the original datagram. The next 0 to 15 octets are 00042 * sequence number changes, one change per bit set in the header 00043 * (there may be no changes and there are two special cases where 00044 * the receiver implicitly knows what changed -- see below). 00045 * 00046 * There are 5 numbers which can change (they are always inserted 00047 * in the following order): TCP urgent pointer, window, 00048 * acknowlegement, sequence number and IP ID. (The urgent pointer 00049 * is different from the others in that its value is sent, not the 00050 * change in value.) Since typical use of SLIP links is biased 00051 * toward small packets (see comments on MTU/MSS below), changes 00052 * use a variable length coding with one octet for numbers in the 00053 * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the 00054 * range 256 - 65535 or 0. (If the change in sequence number or 00055 * ack is more than 65535, an uncompressed packet is sent.) 00056 */ 00057 00058 /* 00059 * Packet types (must not conflict with IP protocol version) 00060 * 00061 * The top nibble of the first octet is the packet type. There are 00062 * three possible types: IP (not proto TCP or tcp with one of the 00063 * control flags set); uncompressed TCP (a normal IP/TCP packet but 00064 * with the 8-bit protocol field replaced by an 8-bit connection id -- 00065 * this type of packet syncs the sender & receiver); and compressed 00066 * TCP (described above). 00067 * 00068 * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and 00069 * is logically part of the 4-bit "changes" field that follows. Top 00070 * three bits are actual packet type. For backward compatibility 00071 * and in the interest of conserving bits, numbers are chosen so the 00072 * IP protocol version number (4) which normally appears in this nibble 00073 * means "IP packet". 00074 */ 00075 00076 /* packet types */ 00077 #define TYPE_IP 0x40 00078 #define TYPE_UNCOMPRESSED_TCP 0x70 00079 #define TYPE_COMPRESSED_TCP 0x80 00080 #define TYPE_ERROR 0x00 00081 00082 /* Bits in first octet of compressed packet */ 00083 #define NEW_C 0x40 /* flag bits for what changed in a packet */ 00084 #define NEW_I 0x20 00085 #define NEW_S 0x08 00086 #define NEW_A 0x04 00087 #define NEW_W 0x02 00088 #define NEW_U 0x01 00089 00090 /* reserved, special-case values of above */ 00091 #define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */ 00092 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */ 00093 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U) 00094 00095 #define TCP_PUSH_BIT 0x10 00096 00097 00098 /* 00099 * "state" data for each active tcp conversation on the wire. This is 00100 * basically a copy of the entire IP/TCP header from the last packet 00101 * we saw from the conversation together with a small identifier 00102 * the transmit & receive ends of the line use to locate saved header. 00103 */ 00104 struct cstate { 00105 struct cstate *cs_next; /* next most recently used state (xmit only) */ 00106 u_short cs_hlen; /* size of hdr (receive only) */ 00107 u_char cs_id; /* connection # associated with this state */ 00108 u_char cs_filler; 00109 union { 00110 char csu_hdr[MAX_HDR]; 00111 struct ip csu_ip; /* ip/tcp hdr from most recent packet */ 00112 } vjcs_u; 00113 }; 00114 #define cs_ip vjcs_u.csu_ip 00115 #define cs_hdr vjcs_u.csu_hdr 00116 00117 00118 struct vjstat { 00119 unsigned long vjs_packets; /* outbound packets */ 00120 unsigned long vjs_compressed; /* outbound compressed packets */ 00121 unsigned long vjs_searches; /* searches for connection state */ 00122 unsigned long vjs_misses; /* times couldn't find conn. state */ 00123 unsigned long vjs_uncompressedin; /* inbound uncompressed packets */ 00124 unsigned long vjs_compressedin; /* inbound compressed packets */ 00125 unsigned long vjs_errorin; /* inbound unknown type packets */ 00126 unsigned long vjs_tossed; /* inbound packets tossed because of error */ 00127 }; 00128 00129 /* 00130 * all the state data for one serial line (we need one of these per line). 00131 */ 00132 struct vjcompress { 00133 struct cstate *last_cs; /* most recently used tstate */ 00134 u_char last_recv; /* last rcvd conn. id */ 00135 u_char last_xmit; /* last sent conn. id */ 00136 u_short flags; 00137 u_char maxSlotIndex; 00138 u_char compressSlot; /* Flag indicating OK to compress slot ID. */ 00139 #if LINK_STATS 00140 struct vjstat stats; 00141 #endif 00142 struct cstate tstate[MAX_SLOTS]; /* xmit connection states */ 00143 struct cstate rstate[MAX_SLOTS]; /* receive connection states */ 00144 }; 00145 00146 /* flag values */ 00147 #define VJF_TOSS 1U /* tossing rcvd frames because of input err */ 00148 00149 extern void vj_compress_init (struct vjcompress *comp); 00150 extern u_int vj_compress_tcp (struct vjcompress *comp, struct pbuf *pb); 00151 extern void vj_uncompress_err (struct vjcompress *comp); 00152 extern int vj_uncompress_uncomp(struct pbuf *nb, struct vjcompress *comp); 00153 extern int vj_uncompress_tcp (struct pbuf **nb, struct vjcompress *comp); 00154 00155 #endif /* VJ_H */