[85a0f07] | 1 | /*- |
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| 2 | * Copyright (c) 1989 The Regents of the University of California. |
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| 3 | * All rights reserved. |
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| 4 | * |
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| 5 | * Redistribution and use in source and binary forms, with or without |
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| 6 | * modification, are permitted provided that the following conditions |
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| 7 | * are met: |
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| 8 | * 1. Redistributions of source code must retain the above copyright |
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| 9 | * notice, this list of conditions and the following disclaimer. |
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| 10 | * 2. Redistributions in binary form must reproduce the above copyright |
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| 11 | * notice, this list of conditions and the following disclaimer in the |
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| 12 | * documentation and/or other materials provided with the distribution. |
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| 13 | * 3. All advertising materials mentioning features or use of this software |
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| 14 | * must display the following acknowledgement: |
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| 15 | * This product includes software developed by the University of |
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| 16 | * California, Berkeley and its contributors. |
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| 17 | * 4. Neither the name of the University nor the names of its contributors |
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| 18 | * may be used to endorse or promote products derived from this software |
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| 19 | * without specific prior written permission. |
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| 20 | * |
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| 21 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
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| 22 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
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| 23 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
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| 24 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
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| 25 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
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| 26 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
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| 27 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
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| 28 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
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| 29 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
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| 30 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
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| 31 | * SUCH DAMAGE. |
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| 32 | * |
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| 33 | * @(#)slcompress.c 7.7 (Berkeley) 5/7/91 |
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| 34 | */ |
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| 35 | |
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| 36 | /* |
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| 37 | * Routines to compress and uncompess tcp packets (for transmission |
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| 38 | * over low speed serial lines. |
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| 39 | * |
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| 40 | * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989: |
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| 41 | * - Initial distribution. |
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| 42 | * |
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| 43 | * $Id$ |
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| 44 | */ |
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| 45 | |
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| 46 | #include <sys/types.h> |
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| 47 | #include <sys/param.h> |
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| 48 | #include <sys/systm.h> |
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| 49 | #include <sys/mbuf.h> |
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| 50 | #include <sys/socket.h> |
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| 51 | #include <sys/socketvar.h> |
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| 52 | |
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| 53 | #include <netinet/in.h> |
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| 54 | #include <netinet/in_systm.h> |
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| 55 | #include <netinet/ip.h> |
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| 56 | #include <netinet/tcp.h> |
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| 57 | |
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| 58 | #include <net/pppcompress.h> |
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| 59 | |
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| 60 | #ifndef SL_NO_STATS |
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| 61 | #define INCR(counter) ++comp->counter; |
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| 62 | #else |
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| 63 | #define INCR(counter) |
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| 64 | #endif |
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| 65 | |
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| 66 | #define BCMP(p1, p2, n) bcmp((char *)(p1), (char *)(p2), (int)(n)) |
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| 67 | #define BCOPY(p1, p2, n) bcopy((char *)(p1), (char *)(p2), (int)(n)) |
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[dc28f16] | 68 | #ifndef _KERNEL |
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[85a0f07] | 69 | #define ovbcopy bcopy |
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| 70 | #endif |
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| 71 | |
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| 72 | void |
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| 73 | vj_compress_init(comp, max_state) |
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| 74 | struct vjcompress *comp; |
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| 75 | int max_state; |
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| 76 | { |
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| 77 | register u_int i; |
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| 78 | register struct cstate *tstate = comp->tstate; |
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| 79 | |
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| 80 | if ((unsigned) max_state > MAX_STATES - 1) |
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| 81 | max_state = MAX_STATES - 1; |
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| 82 | bzero((char *)comp, sizeof(*comp)); |
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| 83 | for (i = max_state; i > 0; --i) { |
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| 84 | tstate[i].cs_id = i; |
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| 85 | tstate[i].cs_next = &tstate[i - 1]; |
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| 86 | } |
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| 87 | tstate[0].cs_next = &tstate[max_state]; |
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| 88 | tstate[0].cs_id = 0; |
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| 89 | comp->last_cs = &tstate[0]; |
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| 90 | comp->last_recv = 255; |
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| 91 | comp->last_xmit = 255; |
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| 92 | comp->flags = SLF_TOSS; |
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| 93 | } |
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| 94 | |
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| 95 | |
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| 96 | /* ENCODE encodes a number that is known to be non-zero. ENCODEZ |
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| 97 | * checks for zero (since zero has to be encoded in the long, 3 byte |
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| 98 | * form). |
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| 99 | */ |
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| 100 | #define ENCODE(n) { \ |
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| 101 | if ((u_short)(n) >= 256) { \ |
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| 102 | *cp++ = 0; \ |
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| 103 | cp[1] = (n); \ |
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| 104 | cp[0] = (n) >> 8; \ |
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| 105 | cp += 2; \ |
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| 106 | } else { \ |
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| 107 | *cp++ = (n); \ |
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| 108 | } \ |
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| 109 | } |
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| 110 | #define ENCODEZ(n) { \ |
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| 111 | if ((u_short)(n) >= 256 || (u_short)(n) == 0) { \ |
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| 112 | *cp++ = 0; \ |
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| 113 | cp[1] = (n); \ |
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| 114 | cp[0] = (n) >> 8; \ |
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| 115 | cp += 2; \ |
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| 116 | } else { \ |
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| 117 | *cp++ = (n); \ |
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| 118 | } \ |
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| 119 | } |
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| 120 | |
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| 121 | #define DECODEL(f) { \ |
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| 122 | if (*cp == 0) {\ |
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| 123 | (f) = htonl(ntohl(f) + ((cp[1] << 8) | cp[2])); \ |
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| 124 | cp += 3; \ |
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| 125 | } else { \ |
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| 126 | (f) = htonl(ntohl(f) + (u_long)*cp++); \ |
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| 127 | } \ |
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| 128 | } |
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| 129 | |
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| 130 | #define DECODES(f) { \ |
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| 131 | if (*cp == 0) {\ |
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| 132 | (f) = htons(ntohs(f) + ((cp[1] << 8) | cp[2])); \ |
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| 133 | cp += 3; \ |
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| 134 | } else { \ |
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| 135 | (f) = htons(ntohs(f) + (u_long)*cp++); \ |
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| 136 | } \ |
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| 137 | } |
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| 138 | |
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| 139 | #define DECODEU(f) { \ |
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| 140 | if (*cp == 0) {\ |
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| 141 | (f) = htons((cp[1] << 8) | cp[2]); \ |
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| 142 | cp += 3; \ |
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| 143 | } else { \ |
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| 144 | (f) = htons((u_long)*cp++); \ |
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| 145 | } \ |
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| 146 | } |
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| 147 | |
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| 148 | u_int |
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| 149 | vj_compress_tcp(m, ip, comp, compress_cid) |
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| 150 | struct mbuf *m; |
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| 151 | register struct ip *ip; |
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| 152 | struct vjcompress *comp; |
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| 153 | int compress_cid; |
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| 154 | { |
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| 155 | register struct cstate *cs = comp->last_cs->cs_next; |
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| 156 | register u_int hlen = ip->ip_hl; |
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| 157 | register struct tcphdr *oth; |
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| 158 | register struct tcphdr *th; |
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| 159 | register u_int deltaS, deltaA; |
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| 160 | register u_int changes = 0; |
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| 161 | u_char new_seq[16]; |
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| 162 | register u_char *cp = new_seq; |
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| 163 | |
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| 164 | /* |
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| 165 | * Bail if this is an IP fragment or if the TCP packet isn't |
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| 166 | * `compressible' (i.e., ACK isn't set or some other control bit is |
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| 167 | * set). (We assume that the caller has already made sure the |
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| 168 | * packet is IP proto TCP). |
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| 169 | */ |
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| 170 | if ((ip->ip_off & htons(0x3fff)) || m->m_len < 40) |
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| 171 | return (TYPE_IP); |
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| 172 | |
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| 173 | th = (struct tcphdr *)&((int *)ip)[hlen]; |
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| 174 | if ((th->th_flags & (TH_SYN|TH_FIN|TH_RST|TH_ACK)) != TH_ACK) |
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| 175 | return (TYPE_IP); |
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| 176 | /* |
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| 177 | * Packet is compressible -- we're going to send either a |
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| 178 | * COMPRESSED_TCP or UNCOMPRESSED_TCP packet. Either way we need |
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| 179 | * to locate (or create) the connection state. Special case the |
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| 180 | * most recently used connection since it's most likely to be used |
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| 181 | * again & we don't have to do any reordering if it's used. |
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| 182 | */ |
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| 183 | INCR(sls_packets) |
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| 184 | if (ip->ip_src.s_addr != cs->cs_ip.ip_src.s_addr || |
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| 185 | ip->ip_dst.s_addr != cs->cs_ip.ip_dst.s_addr || |
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| 186 | *(int *)th != ((int *)&cs->cs_ip)[cs->cs_ip.ip_hl]) { |
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| 187 | /* |
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| 188 | * Wasn't the first -- search for it. |
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| 189 | * |
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| 190 | * States are kept in a circularly linked list with |
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| 191 | * last_cs pointing to the end of the list. The |
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| 192 | * list is kept in lru order by moving a state to the |
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| 193 | * head of the list whenever it is referenced. Since |
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| 194 | * the list is short and, empirically, the connection |
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| 195 | * we want is almost always near the front, we locate |
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| 196 | * states via linear search. If we don't find a state |
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| 197 | * for the datagram, the oldest state is (re-)used. |
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| 198 | */ |
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| 199 | register struct cstate *lcs; |
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| 200 | register struct cstate *lastcs = comp->last_cs; |
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| 201 | |
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| 202 | do { |
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| 203 | lcs = cs; cs = cs->cs_next; |
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| 204 | INCR(sls_searches) |
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| 205 | if (ip->ip_src.s_addr == cs->cs_ip.ip_src.s_addr |
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| 206 | && ip->ip_dst.s_addr == cs->cs_ip.ip_dst.s_addr |
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| 207 | && *(int *)th == ((int *)&cs->cs_ip)[cs->cs_ip.ip_hl]) |
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| 208 | goto found; |
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| 209 | } while (cs != lastcs); |
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| 210 | |
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| 211 | /* |
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| 212 | * Didn't find it -- re-use oldest cstate. Send an |
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| 213 | * uncompressed packet that tells the other side what |
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| 214 | * connection number we're using for this conversation. |
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| 215 | * Note that since the state list is circular, the oldest |
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| 216 | * state points to the newest and we only need to set |
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| 217 | * last_cs to update the lru linkage. |
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| 218 | */ |
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| 219 | INCR(sls_misses) |
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| 220 | comp->last_cs = lcs; |
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| 221 | hlen += th->th_off; |
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| 222 | hlen <<= 2; |
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| 223 | goto uncompressed; |
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| 224 | |
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| 225 | found: |
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| 226 | /* |
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| 227 | * Found it -- move to the front on the connection list. |
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| 228 | */ |
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| 229 | if (cs == lastcs) |
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| 230 | comp->last_cs = lcs; |
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| 231 | else { |
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| 232 | lcs->cs_next = cs->cs_next; |
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| 233 | cs->cs_next = lastcs->cs_next; |
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| 234 | lastcs->cs_next = cs; |
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| 235 | } |
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| 236 | } |
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| 237 | |
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| 238 | /* |
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| 239 | * Make sure that only what we expect to change changed. The first |
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| 240 | * line of the `if' checks the IP protocol version, header length & |
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| 241 | * type of service. The 2nd line checks the "Don't fragment" bit. |
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| 242 | * The 3rd line checks the time-to-live and protocol (the protocol |
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| 243 | * check is unnecessary but costless). The 4th line checks the TCP |
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| 244 | * header length. The 5th line checks IP options, if any. The 6th |
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| 245 | * line checks TCP options, if any. If any of these things are |
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| 246 | * different between the previous & current datagram, we send the |
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| 247 | * current datagram `uncompressed'. |
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| 248 | */ |
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| 249 | oth = (struct tcphdr *)&((int *)&cs->cs_ip)[hlen]; |
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| 250 | deltaS = hlen; |
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| 251 | hlen += th->th_off; |
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| 252 | hlen <<= 2; |
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| 253 | |
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| 254 | if (((u_short *)ip)[0] != ((u_short *)&cs->cs_ip)[0] || |
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| 255 | ((u_short *)ip)[3] != ((u_short *)&cs->cs_ip)[3] || |
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| 256 | ((u_short *)ip)[4] != ((u_short *)&cs->cs_ip)[4] || |
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| 257 | th->th_off != oth->th_off || |
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| 258 | (deltaS > 5 && |
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| 259 | BCMP(ip + 1, &cs->cs_ip + 1, (deltaS - 5) << 2)) || |
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| 260 | (th->th_off > 5 && |
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| 261 | BCMP(th + 1, oth + 1, (th->th_off - 5) << 2))) |
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| 262 | goto uncompressed; |
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| 263 | |
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| 264 | /* |
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| 265 | * Figure out which of the changing fields changed. The |
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| 266 | * receiver expects changes in the order: urgent, window, |
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| 267 | * ack, seq (the order minimizes the number of temporaries |
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| 268 | * needed in this section of code). |
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| 269 | */ |
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| 270 | if (th->th_flags & TH_URG) { |
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| 271 | deltaS = ntohs(th->th_urp); |
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| 272 | ENCODEZ(deltaS); |
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| 273 | changes |= NEW_U; |
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| 274 | } else if (th->th_urp != oth->th_urp) |
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| 275 | /* argh! URG not set but urp changed -- a sensible |
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| 276 | * implementation should never do this but RFC793 |
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| 277 | * doesn't prohibit the change so we have to deal |
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| 278 | * with it. */ |
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| 279 | goto uncompressed; |
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| 280 | |
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[78d6a50] | 281 | if ((deltaS = (u_short)(ntohs(th->th_win) - ntohs(oth->th_win)))) { |
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[85a0f07] | 282 | ENCODE(deltaS); |
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| 283 | changes |= NEW_W; |
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| 284 | } |
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| 285 | |
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[78d6a50] | 286 | if ((deltaA = ntohl(th->th_ack) - ntohl(oth->th_ack))) { |
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[85a0f07] | 287 | if (deltaA > 0xffff) |
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| 288 | goto uncompressed; |
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| 289 | ENCODE(deltaA); |
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| 290 | changes |= NEW_A; |
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| 291 | } |
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| 292 | |
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[78d6a50] | 293 | if ((deltaS = ntohl(th->th_seq) - ntohl(oth->th_seq))) { |
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[85a0f07] | 294 | if (deltaS > 0xffff) |
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| 295 | goto uncompressed; |
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| 296 | ENCODE(deltaS); |
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| 297 | changes |= NEW_S; |
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| 298 | } |
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| 299 | |
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| 300 | switch(changes) { |
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| 301 | |
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| 302 | case 0: |
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| 303 | /* |
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| 304 | * Nothing changed. If this packet contains data and the |
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| 305 | * last one didn't, this is probably a data packet following |
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| 306 | * an ack (normal on an interactive connection) and we send |
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| 307 | * it compressed. Otherwise it's probably a retransmit, |
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| 308 | * retransmitted ack or window probe. Send it uncompressed |
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| 309 | * in case the other side missed the compressed version. |
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| 310 | */ |
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| 311 | if (ip->ip_len != cs->cs_ip.ip_len && |
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| 312 | ntohs(cs->cs_ip.ip_len) == hlen) |
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| 313 | break; |
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| 314 | |
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| 315 | /* (fall through) */ |
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| 316 | |
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| 317 | case SPECIAL_I: |
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| 318 | case SPECIAL_D: |
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| 319 | /* |
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| 320 | * actual changes match one of our special case encodings -- |
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| 321 | * send packet uncompressed. |
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| 322 | */ |
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| 323 | goto uncompressed; |
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| 324 | |
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| 325 | case NEW_S|NEW_A: |
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| 326 | if (deltaS == deltaA && |
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| 327 | deltaS == ntohs(cs->cs_ip.ip_len) - hlen) { |
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| 328 | /* special case for echoed terminal traffic */ |
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| 329 | changes = SPECIAL_I; |
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| 330 | cp = new_seq; |
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| 331 | } |
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| 332 | break; |
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| 333 | |
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| 334 | case NEW_S: |
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| 335 | if (deltaS == ntohs(cs->cs_ip.ip_len) - hlen) { |
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| 336 | /* special case for data xfer */ |
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| 337 | changes = SPECIAL_D; |
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| 338 | cp = new_seq; |
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| 339 | } |
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| 340 | break; |
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| 341 | } |
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| 342 | |
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| 343 | deltaS = ntohs(ip->ip_id) - ntohs(cs->cs_ip.ip_id); |
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| 344 | if (deltaS != 1) { |
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| 345 | ENCODEZ(deltaS); |
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| 346 | changes |= NEW_I; |
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| 347 | } |
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| 348 | if (th->th_flags & TH_PUSH) |
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| 349 | changes |= TCP_PUSH_BIT; |
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| 350 | /* |
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| 351 | * Grab the cksum before we overwrite it below. Then update our |
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| 352 | * state with this packet's header. |
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| 353 | */ |
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| 354 | deltaA = ntohs(th->th_sum); |
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| 355 | BCOPY(ip, &cs->cs_ip, hlen); |
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| 356 | |
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| 357 | /* |
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| 358 | * We want to use the original packet as our compressed packet. |
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| 359 | * (cp - new_seq) is the number of bytes we need for compressed |
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| 360 | * sequence numbers. In addition we need one byte for the change |
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| 361 | * mask, one for the connection id and two for the tcp checksum. |
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| 362 | * So, (cp - new_seq) + 4 bytes of header are needed. hlen is how |
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| 363 | * many bytes of the original packet to toss so subtract the two to |
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| 364 | * get the new packet size. |
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| 365 | */ |
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| 366 | deltaS = cp - new_seq; |
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| 367 | cp = (u_char *)ip; |
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| 368 | if (compress_cid == 0 || comp->last_xmit != cs->cs_id) { |
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| 369 | comp->last_xmit = cs->cs_id; |
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| 370 | hlen -= deltaS + 4; |
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| 371 | cp += hlen; |
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| 372 | *cp++ = changes | NEW_C; |
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| 373 | *cp++ = cs->cs_id; |
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| 374 | } else { |
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| 375 | hlen -= deltaS + 3; |
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| 376 | cp += hlen; |
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| 377 | *cp++ = changes; |
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| 378 | } |
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| 379 | m->m_len -= hlen; |
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| 380 | m->m_data += hlen; |
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| 381 | *cp++ = deltaA >> 8; |
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| 382 | *cp++ = deltaA; |
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| 383 | BCOPY(new_seq, cp, deltaS); |
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| 384 | INCR(sls_compressed) |
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| 385 | return (TYPE_COMPRESSED_TCP); |
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| 386 | |
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| 387 | /* |
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| 388 | * Update connection state cs & send uncompressed packet ('uncompressed' |
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| 389 | * means a regular ip/tcp packet but with the 'conversation id' we hope |
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| 390 | * to use on future compressed packets in the protocol field). |
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| 391 | */ |
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| 392 | uncompressed: |
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| 393 | BCOPY(ip, &cs->cs_ip, hlen); |
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| 394 | ip->ip_p = cs->cs_id; |
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| 395 | comp->last_xmit = cs->cs_id; |
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| 396 | return (TYPE_UNCOMPRESSED_TCP); |
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| 397 | } |
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| 398 | |
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| 399 | |
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| 400 | int |
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| 401 | vj_uncompress_tcp(bufp, len, type, comp) |
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| 402 | u_char **bufp; |
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| 403 | int len; |
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| 404 | u_int type; |
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| 405 | struct vjcompress *comp; |
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| 406 | { |
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| 407 | u_char *hdr, *cp; |
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| 408 | int hlen, vjlen; |
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| 409 | |
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| 410 | cp = bufp? *bufp: NULL; |
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| 411 | vjlen = vj_uncompress_tcp_core(cp, len, len, type, comp, &hdr, &hlen); |
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| 412 | if (vjlen < 0) |
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| 413 | return (0); /* error */ |
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| 414 | if (vjlen == 0) |
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| 415 | return (len); /* was uncompressed already */ |
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| 416 | |
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| 417 | cp += vjlen; |
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| 418 | len -= vjlen; |
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| 419 | |
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| 420 | /* |
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| 421 | * At this point, cp points to the first byte of data in the |
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| 422 | * packet. If we're not aligned on a 4-byte boundary, copy the |
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| 423 | * data down so the ip & tcp headers will be aligned. Then back up |
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| 424 | * cp by the tcp/ip header length to make room for the reconstructed |
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| 425 | * header (we assume the packet we were handed has enough space to |
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| 426 | * prepend 128 bytes of header). |
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| 427 | */ |
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| 428 | if ((int)cp & 3) { |
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| 429 | if (len > 0) |
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| 430 | (void) ovbcopy(cp, (caddr_t)((int)cp &~ 3), len); |
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| 431 | cp = (u_char *)((int)cp &~ 3); |
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| 432 | } |
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| 433 | cp -= hlen; |
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| 434 | len += hlen; |
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| 435 | BCOPY(hdr, cp, hlen); |
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| 436 | |
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| 437 | *bufp = cp; |
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| 438 | return (len); |
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| 439 | } |
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| 440 | |
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| 441 | /* |
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| 442 | * Uncompress a packet of total length total_len. The first buflen |
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| 443 | * bytes are at buf; this must include the entire (compressed or |
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| 444 | * uncompressed) TCP/IP header. This procedure returns the length |
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| 445 | * of the VJ header, with a pointer to the uncompressed IP header |
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| 446 | * in *hdrp and its length in *hlenp. |
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| 447 | */ |
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| 448 | int |
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| 449 | vj_uncompress_tcp_core(buf, buflen, total_len, type, comp, hdrp, hlenp) |
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| 450 | u_char *buf; |
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| 451 | int buflen, total_len; |
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| 452 | u_int type; |
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| 453 | struct vjcompress *comp; |
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| 454 | u_char **hdrp; |
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| 455 | u_int *hlenp; |
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| 456 | { |
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| 457 | register u_char *cp; |
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| 458 | register u_int hlen, changes; |
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| 459 | register struct tcphdr *th; |
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| 460 | register struct cstate *cs; |
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| 461 | register struct ip *ip; |
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| 462 | register u_short *bp; |
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| 463 | register u_int vjlen; |
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| 464 | |
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| 465 | switch (type) { |
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| 466 | |
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| 467 | case TYPE_UNCOMPRESSED_TCP: |
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| 468 | ip = (struct ip *) buf; |
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| 469 | if (ip->ip_p >= MAX_STATES) |
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| 470 | goto bad; |
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| 471 | cs = &comp->rstate[comp->last_recv = ip->ip_p]; |
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| 472 | comp->flags &=~ SLF_TOSS; |
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| 473 | ip->ip_p = IPPROTO_TCP; |
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| 474 | /* |
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| 475 | * Calculate the size of the TCP/IP header and make sure that |
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| 476 | * we don't overflow the space we have available for it. |
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| 477 | */ |
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| 478 | hlen = ip->ip_hl << 2; |
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| 479 | if (hlen + sizeof(struct tcphdr) > buflen) |
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| 480 | goto bad; |
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| 481 | hlen += ((struct tcphdr *)&((char *)ip)[hlen])->th_off << 2; |
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| 482 | if (hlen > MAX_HDR || hlen > buflen) |
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| 483 | goto bad; |
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| 484 | BCOPY(ip, &cs->cs_ip, hlen); |
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| 485 | cs->cs_hlen = hlen; |
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| 486 | INCR(sls_uncompressedin) |
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| 487 | *hdrp = (u_char *) &cs->cs_ip; |
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| 488 | *hlenp = hlen; |
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| 489 | return (0); |
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| 490 | |
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| 491 | default: |
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| 492 | goto bad; |
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| 493 | |
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| 494 | case TYPE_COMPRESSED_TCP: |
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| 495 | break; |
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| 496 | } |
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| 497 | /* We've got a compressed packet. */ |
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| 498 | INCR(sls_compressedin) |
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| 499 | cp = buf; |
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| 500 | changes = *cp++; |
---|
| 501 | if (changes & NEW_C) { |
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| 502 | /* Make sure the state index is in range, then grab the state. |
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| 503 | * If we have a good state index, clear the 'discard' flag. */ |
---|
| 504 | if (*cp >= MAX_STATES) |
---|
| 505 | goto bad; |
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| 506 | |
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| 507 | comp->flags &=~ SLF_TOSS; |
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| 508 | comp->last_recv = *cp++; |
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| 509 | } else { |
---|
| 510 | /* this packet has an implicit state index. If we've |
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| 511 | * had a line error since the last time we got an |
---|
| 512 | * explicit state index, we have to toss the packet. */ |
---|
| 513 | if (comp->flags & SLF_TOSS) { |
---|
| 514 | INCR(sls_tossed) |
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| 515 | return (-1); |
---|
| 516 | } |
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| 517 | } |
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| 518 | cs = &comp->rstate[comp->last_recv]; |
---|
| 519 | hlen = cs->cs_ip.ip_hl << 2; |
---|
| 520 | th = (struct tcphdr *)&((u_char *)&cs->cs_ip)[hlen]; |
---|
| 521 | th->th_sum = htons((*cp << 8) | cp[1]); |
---|
| 522 | cp += 2; |
---|
| 523 | if (changes & TCP_PUSH_BIT) |
---|
| 524 | th->th_flags |= TH_PUSH; |
---|
| 525 | else |
---|
| 526 | th->th_flags &=~ TH_PUSH; |
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| 527 | |
---|
| 528 | switch (changes & SPECIALS_MASK) { |
---|
| 529 | case SPECIAL_I: |
---|
| 530 | { |
---|
| 531 | register u_int i = ntohs(cs->cs_ip.ip_len) - cs->cs_hlen; |
---|
| 532 | th->th_ack = htonl(ntohl(th->th_ack) + i); |
---|
| 533 | th->th_seq = htonl(ntohl(th->th_seq) + i); |
---|
| 534 | } |
---|
| 535 | break; |
---|
| 536 | |
---|
| 537 | case SPECIAL_D: |
---|
| 538 | th->th_seq = htonl(ntohl(th->th_seq) + ntohs(cs->cs_ip.ip_len) |
---|
| 539 | - cs->cs_hlen); |
---|
| 540 | break; |
---|
| 541 | |
---|
| 542 | default: |
---|
| 543 | if (changes & NEW_U) { |
---|
| 544 | th->th_flags |= TH_URG; |
---|
| 545 | DECODEU(th->th_urp) |
---|
| 546 | } else |
---|
| 547 | th->th_flags &=~ TH_URG; |
---|
| 548 | if (changes & NEW_W) |
---|
| 549 | DECODES(th->th_win) |
---|
| 550 | if (changes & NEW_A) |
---|
| 551 | DECODEL(th->th_ack) |
---|
| 552 | if (changes & NEW_S) |
---|
| 553 | DECODEL(th->th_seq) |
---|
| 554 | break; |
---|
| 555 | } |
---|
| 556 | if (changes & NEW_I) { |
---|
| 557 | DECODES(cs->cs_ip.ip_id) |
---|
| 558 | } else |
---|
| 559 | cs->cs_ip.ip_id = htons(ntohs(cs->cs_ip.ip_id) + 1); |
---|
| 560 | |
---|
| 561 | /* |
---|
| 562 | * At this point, cp points to the first byte of data in the |
---|
| 563 | * packet. Fill in the IP total length and update the IP |
---|
| 564 | * header checksum. |
---|
| 565 | */ |
---|
| 566 | vjlen = cp - buf; |
---|
| 567 | buflen -= vjlen; |
---|
| 568 | if (buflen < 0) |
---|
| 569 | /* we must have dropped some characters (crc should detect |
---|
| 570 | * this but the old slip framing won't) */ |
---|
| 571 | goto bad; |
---|
| 572 | |
---|
| 573 | total_len += cs->cs_hlen - vjlen; |
---|
| 574 | cs->cs_ip.ip_len = htons(total_len); |
---|
| 575 | |
---|
| 576 | /* recompute the ip header checksum */ |
---|
| 577 | bp = (u_short *) &cs->cs_ip; |
---|
| 578 | cs->cs_ip.ip_sum = 0; |
---|
| 579 | for (changes = 0; hlen > 0; hlen -= 2) |
---|
| 580 | changes += *bp++; |
---|
| 581 | changes = (changes & 0xffff) + (changes >> 16); |
---|
| 582 | changes = (changes & 0xffff) + (changes >> 16); |
---|
| 583 | cs->cs_ip.ip_sum = ~ changes; |
---|
| 584 | |
---|
| 585 | *hdrp = (u_char *) &cs->cs_ip; |
---|
| 586 | *hlenp = cs->cs_hlen; |
---|
| 587 | return vjlen; |
---|
| 588 | |
---|
| 589 | bad: |
---|
| 590 | comp->flags |= SLF_TOSS; |
---|
| 591 | INCR(sls_errorin) |
---|
| 592 | return (-1); |
---|
| 593 | } |
---|