Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]
FreeBSD/Linux Kernel Cross Reference
sys/net/slcompress.c
Version:
- FREEBSD - FREEBSD-13-STABLE - FREEBSD-13-0 - FREEBSD-12-STABLE - FREEBSD-12-0 - FREEBSD-11-STABLE - FREEBSD-11-0 - FREEBSD-10-STABLE - FREEBSD-10-0 - FREEBSD-9-STABLE - FREEBSD-9-0 - FREEBSD-8-STABLE - FREEBSD-8-0 - FREEBSD-7-STABLE - FREEBSD-7-0 - FREEBSD-6-STABLE - FREEBSD-6-0 - FREEBSD-5-STABLE - FREEBSD-5-0 - FREEBSD-4-STABLE - FREEBSD-3-STABLE - FREEBSD22 - l41 - OPENBSD - linux-2.6 - MK84 - PLAN9 - xnu-8792
SearchContext: - none - 3 - 10
SearchContext: - none - 3 - 10
1 /*- 2 * Copyright (c) 1989, 1993, 1994 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)slcompress.c 8.2 (Berkeley) 4/16/94 30 * $FreeBSD$ 31 */ 32 33 /* 34 * Routines to compress and uncompess tcp packets (for transmission 35 * over low speed serial lines. 36 * 37 * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989: 38 * - Initial distribution. 39 * 40 */ 41 42 #include <sys/param.h> 43 #include <sys/mbuf.h> 44 #include <sys/systm.h> 45 46 #include <netinet/in.h> 47 #include <netinet/in_systm.h> 48 #include <netinet/ip.h> 49 #include <netinet/tcp.h> 50 51 #include <net/slcompress.h> 52 53 #ifndef SL_NO_STATS 54 #define INCR(counter) ++comp->counter; 55 #else 56 #define INCR(counter) 57 #endif 58 59 #define BCMP(p1, p2, n) bcmp((void *)(p1), (void *)(p2), (int)(n)) 60 #define BCOPY(p1, p2, n) bcopy((void *)(p1), (void *)(p2), (int)(n)) 61 62 void 63 sl_compress_init(struct slcompress *comp, int max_state) 64 { 65 u_int i; 66 struct cstate *tstate = comp->tstate; 67 68 if (max_state == -1) { 69 max_state = MAX_STATES - 1; 70 bzero((char *)comp, sizeof(*comp)); 71 } else { 72 /* Don't reset statistics */ 73 bzero((char *)comp->tstate, sizeof(comp->tstate)); 74 bzero((char *)comp->rstate, sizeof(comp->rstate)); 75 } 76 for (i = max_state; i > 0; --i) { 77 tstate[i].cs_id = i; 78 tstate[i].cs_next = &tstate[i - 1]; 79 } 80 tstate[0].cs_next = &tstate[max_state]; 81 tstate[0].cs_id = 0; 82 comp->last_cs = &tstate[0]; 83 comp->last_recv = 255; 84 comp->last_xmit = 255; 85 comp->flags = SLF_TOSS; 86 } 87 88 89 /* ENCODE encodes a number that is known to be non-zero. ENCODEZ 90 * checks for zero (since zero has to be encoded in the long, 3 byte 91 * form). 92 */ 93 #define ENCODE(n) { \ 94 if ((u_int16_t)(n) >= 256) { \ 95 *cp++ = 0; \ 96 cp[1] = (n); \ 97 cp[0] = (n) >> 8; \ 98 cp += 2; \ 99 } else { \ 100 *cp++ = (n); \ 101 } \ 102 } 103 #define ENCODEZ(n) { \ 104 if ((u_int16_t)(n) >= 256 || (u_int16_t)(n) == 0) { \ 105 *cp++ = 0; \ 106 cp[1] = (n); \ 107 cp[0] = (n) >> 8; \ 108 cp += 2; \ 109 } else { \ 110 *cp++ = (n); \ 111 } \ 112 } 113 114 #define DECODEL(f) { \ 115 if (*cp == 0) {\ 116 (f) = htonl(ntohl(f) + ((cp[1] << 8) | cp[2])); \ 117 cp += 3; \ 118 } else { \ 119 (f) = htonl(ntohl(f) + (u_int32_t)*cp++); \ 120 } \ 121 } 122 123 #define DECODES(f) { \ 124 if (*cp == 0) {\ 125 (f) = htons(ntohs(f) + ((cp[1] << 8) | cp[2])); \ 126 cp += 3; \ 127 } else { \ 128 (f) = htons(ntohs(f) + (u_int32_t)*cp++); \ 129 } \ 130 } 131 132 #define DECODEU(f) { \ 133 if (*cp == 0) {\ 134 (f) = htons((cp[1] << 8) | cp[2]); \ 135 cp += 3; \ 136 } else { \ 137 (f) = htons((u_int32_t)*cp++); \ 138 } \ 139 } 140 141 /* 142 * Attempt to compress an outgoing TCP packet and return the type of 143 * the result. The caller must have already verified that the protocol 144 * is TCP. The first mbuf must contain the complete IP and TCP headers, 145 * and "ip" must be == mtod(m, struct ip *). "comp" supplies the 146 * compression state, and "compress_cid" tells us whether it is OK 147 * to leave out the CID field when feasible. 148 * 149 * The caller is responsible for adjusting m->m_pkthdr.len upon return, 150 * if m is an M_PKTHDR mbuf. 151 */ 152 u_int 153 sl_compress_tcp(struct mbuf *m, struct ip *ip, struct slcompress *comp, 154 int compress_cid) 155 { 156 struct cstate *cs = comp->last_cs->cs_next; 157 u_int hlen = ip->ip_hl; 158 struct tcphdr *oth; 159 struct tcphdr *th; 160 u_int deltaS, deltaA; 161 u_int changes = 0; 162 u_char new_seq[16]; 163 u_char *cp = new_seq; 164 165 /* 166 * Bail if this is an IP fragment or if the TCP packet isn't 167 * `compressible' (i.e., ACK isn't set or some other control bit is 168 * set). (We assume that the caller has already made sure the 169 * packet is IP proto TCP). 170 */ 171 if ((ip->ip_off & htons(0x3fff)) || m->m_len < 40) 172 return (TYPE_IP); 173 174 th = (struct tcphdr *)&((int32_t *)ip)[hlen]; 175 if ((th->th_flags & (TH_SYN|TH_FIN|TH_RST|TH_ACK)) != TH_ACK) 176 return (TYPE_IP); 177 /* 178 * Packet is compressible -- we're going to send either a 179 * COMPRESSED_TCP or UNCOMPRESSED_TCP packet. Either way we need 180 * to locate (or create) the connection state. Special case the 181 * most recently used connection since it's most likely to be used 182 * again & we don't have to do any reordering if it's used. 183 */ 184 INCR(sls_packets) 185 if (ip->ip_src.s_addr != cs->cs_ip.ip_src.s_addr || 186 ip->ip_dst.s_addr != cs->cs_ip.ip_dst.s_addr || 187 *(int32_t *)th != ((int32_t *)&cs->cs_ip)[cs->cs_ip.ip_hl]) { 188 /* 189 * Wasn't the first -- search for it. 190 * 191 * States are kept in a circularly linked list with 192 * last_cs pointing to the end of the list. The 193 * list is kept in lru order by moving a state to the 194 * head of the list whenever it is referenced. Since 195 * the list is short and, empirically, the connection 196 * we want is almost always near the front, we locate 197 * states via linear search. If we don't find a state 198 * for the datagram, the oldest state is (re-)used. 199 */ 200 struct cstate *lcs; 201 struct cstate *lastcs = comp->last_cs; 202 203 do { 204 lcs = cs; cs = cs->cs_next; 205 INCR(sls_searches) 206 if (ip->ip_src.s_addr == cs->cs_ip.ip_src.s_addr 207 && ip->ip_dst.s_addr == cs->cs_ip.ip_dst.s_addr 208 && *(int32_t *)th == 209 ((int32_t *)&cs->cs_ip)[cs->cs_ip.ip_hl]) 210 goto found; 211 } while (cs != lastcs); 212 213 /* 214 * Didn't find it -- re-use oldest cstate. Send an 215 * uncompressed packet that tells the other side what 216 * connection number we're using for this conversation. 217 * Note that since the state list is circular, the oldest 218 * state points to the newest and we only need to set 219 * last_cs to update the lru linkage. 220 */ 221 INCR(sls_misses) 222 comp->last_cs = lcs; 223 hlen += th->th_off; 224 hlen <<= 2; 225 if (hlen > m->m_len) 226 return TYPE_IP; 227 goto uncompressed; 228 229 found: 230 /* 231 * Found it -- move to the front on the connection list. 232 */ 233 if (cs == lastcs) 234 comp->last_cs = lcs; 235 else { 236 lcs->cs_next = cs->cs_next; 237 cs->cs_next = lastcs->cs_next; 238 lastcs->cs_next = cs; 239 } 240 } 241 242 /* 243 * Make sure that only what we expect to change changed. The first 244 * line of the `if' checks the IP protocol version, header length & 245 * type of service. The 2nd line checks the "Don't fragment" bit. 246 * The 3rd line checks the time-to-live and protocol (the protocol 247 * check is unnecessary but costless). The 4th line checks the TCP 248 * header length. The 5th line checks IP options, if any. The 6th 249 * line checks TCP options, if any. If any of these things are 250 * different between the previous & current datagram, we send the 251 * current datagram `uncompressed'. 252 */ 253 oth = (struct tcphdr *)&((int32_t *)&cs->cs_ip)[hlen]; 254 deltaS = hlen; 255 hlen += th->th_off; 256 hlen <<= 2; 257 if (hlen > m->m_len) 258 return TYPE_IP; 259 260 if (((u_int16_t *)ip)[0] != ((u_int16_t *)&cs->cs_ip)[0] || 261 ((u_int16_t *)ip)[3] != ((u_int16_t *)&cs->cs_ip)[3] || 262 ((u_int16_t *)ip)[4] != ((u_int16_t *)&cs->cs_ip)[4] || 263 th->th_off != oth->th_off || 264 (deltaS > 5 && 265 BCMP(ip + 1, &cs->cs_ip + 1, (deltaS - 5) << 2)) || 266 (th->th_off > 5 && 267 BCMP(th + 1, oth + 1, (th->th_off - 5) << 2))) 268 goto uncompressed; 269 270 /* 271 * Figure out which of the changing fields changed. The 272 * receiver expects changes in the order: urgent, window, 273 * ack, seq (the order minimizes the number of temporaries 274 * needed in this section of code). 275 */ 276 if (th->th_flags & TH_URG) { 277 deltaS = ntohs(th->th_urp); 278 ENCODEZ(deltaS); 279 changes |= NEW_U; 280 } else if (th->th_urp != oth->th_urp) 281 /* argh! URG not set but urp changed -- a sensible 282 * implementation should never do this but RFC793 283 * doesn't prohibit the change so we have to deal 284 * with it. */ 285 goto uncompressed; 286 287 deltaS = (u_int16_t)(ntohs(th->th_win) - ntohs(oth->th_win)); 288 if (deltaS) { 289 ENCODE(deltaS); 290 changes |= NEW_W; 291 } 292 293 deltaA = ntohl(th->th_ack) - ntohl(oth->th_ack); 294 if (deltaA) { 295 if (deltaA > 0xffff) 296 goto uncompressed; 297 ENCODE(deltaA); 298 changes |= NEW_A; 299 } 300 301 deltaS = ntohl(th->th_seq) - ntohl(oth->th_seq); 302 if (deltaS) { 303 if (deltaS > 0xffff) 304 goto uncompressed; 305 ENCODE(deltaS); 306 changes |= NEW_S; 307 } 308 309 switch(changes) { 310 311 case 0: 312 /* 313 * Nothing changed. If this packet contains data and the 314 * last one didn't, this is probably a data packet following 315 * an ack (normal on an interactive connection) and we send 316 * it compressed. Otherwise it's probably a retransmit, 317 * retransmitted ack or window probe. Send it uncompressed 318 * in case the other side missed the compressed version. 319 */ 320 if (ip->ip_len != cs->cs_ip.ip_len && 321 ntohs(cs->cs_ip.ip_len) == hlen) 322 break; 323 324 /* FALLTHROUGH */ 325 326 case SPECIAL_I: 327 case SPECIAL_D: 328 /* 329 * actual changes match one of our special case encodings -- 330 * send packet uncompressed. 331 */ 332 goto uncompressed; 333 334 case NEW_S|NEW_A: 335 if (deltaS == deltaA && 336 deltaS == ntohs(cs->cs_ip.ip_len) - hlen) { 337 /* special case for echoed terminal traffic */ 338 changes = SPECIAL_I; 339 cp = new_seq; 340 } 341 break; 342 343 case NEW_S: 344 if (deltaS == ntohs(cs->cs_ip.ip_len) - hlen) { 345 /* special case for data xfer */ 346 changes = SPECIAL_D; 347 cp = new_seq; 348 } 349 break; 350 } 351 352 deltaS = ntohs(ip->ip_id) - ntohs(cs->cs_ip.ip_id); 353 if (deltaS != 1) { 354 ENCODEZ(deltaS); 355 changes |= NEW_I; 356 } 357 if (th->th_flags & TH_PUSH) 358 changes |= TCP_PUSH_BIT; 359 /* 360 * Grab the cksum before we overwrite it below. Then update our 361 * state with this packet's header. 362 */ 363 deltaA = ntohs(th->th_sum); 364 BCOPY(ip, &cs->cs_ip, hlen); 365 366 /* 367 * We want to use the original packet as our compressed packet. 368 * (cp - new_seq) is the number of bytes we need for compressed 369 * sequence numbers. In addition we need one byte for the change 370 * mask, one for the connection id and two for the tcp checksum. 371 * So, (cp - new_seq) + 4 bytes of header are needed. hlen is how 372 * many bytes of the original packet to toss so subtract the two to 373 * get the new packet size. 374 */ 375 deltaS = cp - new_seq; 376 cp = (u_char *)ip; 377 if (compress_cid == 0 || comp->last_xmit != cs->cs_id) { 378 comp->last_xmit = cs->cs_id; 379 hlen -= deltaS + 4; 380 cp += hlen; 381 *cp++ = changes | NEW_C; 382 *cp++ = cs->cs_id; 383 } else { 384 hlen -= deltaS + 3; 385 cp += hlen; 386 *cp++ = changes; 387 } 388 m->m_len -= hlen; 389 m->m_data += hlen; 390 *cp++ = deltaA >> 8; 391 *cp++ = deltaA; 392 BCOPY(new_seq, cp, deltaS); 393 INCR(sls_compressed) 394 return (TYPE_COMPRESSED_TCP); 395 396 /* 397 * Update connection state cs & send uncompressed packet ('uncompressed' 398 * means a regular ip/tcp packet but with the 'conversation id' we hope 399 * to use on future compressed packets in the protocol field). 400 */ 401 uncompressed: 402 BCOPY(ip, &cs->cs_ip, hlen); 403 ip->ip_p = cs->cs_id; 404 comp->last_xmit = cs->cs_id; 405 return (TYPE_UNCOMPRESSED_TCP); 406 } 407 408 409 int 410 sl_uncompress_tcp(u_char **bufp, int len, u_int type, struct slcompress *comp) 411 { 412 u_char *hdr, *cp; 413 int hlen, vjlen; 414 415 cp = bufp? *bufp: NULL; 416 vjlen = sl_uncompress_tcp_core(cp, len, len, type, comp, &hdr, &hlen); 417 if (vjlen < 0) 418 return (0); /* error */ 419 if (vjlen == 0) 420 return (len); /* was uncompressed already */ 421 422 cp += vjlen; 423 len -= vjlen; 424 425 /* 426 * At this point, cp points to the first byte of data in the 427 * packet. If we're not aligned on a 4-byte boundary, copy the 428 * data down so the ip & tcp headers will be aligned. Then back up 429 * cp by the tcp/ip header length to make room for the reconstructed 430 * header (we assume the packet we were handed has enough space to 431 * prepend 128 bytes of header). 432 */ 433 if ((intptr_t)cp & 3) { 434 if (len > 0) 435 BCOPY(cp, ((intptr_t)cp &~ 3), len); 436 cp = (u_char *)((intptr_t)cp &~ 3); 437 } 438 cp -= hlen; 439 len += hlen; 440 BCOPY(hdr, cp, hlen); 441 442 *bufp = cp; 443 return (len); 444 } 445 446 /* 447 * Uncompress a packet of total length total_len. The first buflen 448 * bytes are at buf; this must include the entire (compressed or 449 * uncompressed) TCP/IP header. This procedure returns the length 450 * of the VJ header, with a pointer to the uncompressed IP header 451 * in *hdrp and its length in *hlenp. 452 */ 453 int 454 sl_uncompress_tcp_core(u_char *buf, int buflen, int total_len, u_int type, 455 struct slcompress *comp, u_char **hdrp, u_int *hlenp) 456 { 457 u_char *cp; 458 u_int hlen, changes; 459 struct tcphdr *th; 460 struct cstate *cs; 461 struct ip *ip; 462 u_int16_t *bp; 463 u_int vjlen; 464 465 switch (type) { 466 467 case TYPE_UNCOMPRESSED_TCP: 468 ip = (struct ip *) buf; 469 if (ip->ip_p >= MAX_STATES) 470 goto bad; 471 cs = &comp->rstate[comp->last_recv = ip->ip_p]; 472 comp->flags &=~ SLF_TOSS; 473 ip->ip_p = IPPROTO_TCP; 474 /* 475 * Calculate the size of the TCP/IP header and make sure that 476 * we don't overflow the space we have available for it. 477 */ 478 hlen = ip->ip_hl << 2; 479 if (hlen + sizeof(struct tcphdr) > buflen) 480 goto bad; 481 hlen += ((struct tcphdr *)&((char *)ip)[hlen])->th_off << 2; 482 if (hlen > MAX_HDR || hlen > buflen) 483 goto bad; 484 BCOPY(ip, &cs->cs_ip, hlen); 485 cs->cs_hlen = hlen; 486 INCR(sls_uncompressedin) 487 *hdrp = (u_char *) &cs->cs_ip; 488 *hlenp = hlen; 489 return (0); 490 491 default: 492 goto bad; 493 494 case TYPE_COMPRESSED_TCP: 495 break; 496 } 497 /* We've got a compressed packet. */ 498 INCR(sls_compressedin) 499 cp = buf; 500 changes = *cp++; 501 if (changes & NEW_C) { 502 /* Make sure the state index is in range, then grab the state. 503 * If we have a good state index, clear the 'discard' flag. */ 504 if (*cp >= MAX_STATES) 505 goto bad; 506 507 comp->flags &=~ SLF_TOSS; 508 comp->last_recv = *cp++; 509 } else { 510 /* this packet has an implicit state index. If we've 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) 515 return (-1); 516 } 517 } 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; 527 528 switch (changes & SPECIALS_MASK) { 529 case SPECIAL_I: 530 { 531 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_int16_t *) &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 }
Cache object: 8cbbb35f2d0a8b7ee83747de34e3f780
[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]