1/* 2 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved. 3 * 4 * @APPLE_LICENSE_HEADER_START@ 5 * 6 * This file contains Original Code and/or Modifications of Original Code 7 * as defined in and that are subject to the Apple Public Source License 8 * Version 2.0 (the 'License'). You may not use this file except in 9 * compliance with the License. Please obtain a copy of the License at 10 * http://www.opensource.apple.com/apsl/ and read it before using this 11 * file. 12 * 13 * The Original Code and all software distributed under the License are 14 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER 15 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, 16 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, 17 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. 18 * Please see the License for the specific language governing rights and 19 * limitations under the License. 20 * 21 * @APPLE_LICENSE_HEADER_END@ 22 */ 23 24/*- 25 * Copyright (c) 1989, 1993, 1994 26 * The Regents of the University of California. All rights reserved. 27 * 28 * Redistribution and use in source and binary forms, with or without 29 * modification, are permitted provided that the following conditions 30 * are met: 31 * 1. Redistributions of source code must retain the above copyright 32 * notice, this list of conditions and the following disclaimer. 33 * 2. Redistributions in binary form must reproduce the above copyright 34 * notice, this list of conditions and the following disclaimer in the 35 * documentation and/or other materials provided with the distribution. 36 * 3. All advertising materials mentioning features or use of this software 37 * must display the following acknowledgement: 38 * This product includes software developed by the University of 39 * California, Berkeley and its contributors. 40 * 4. Neither the name of the University nor the names of its contributors 41 * may be used to endorse or promote products derived from this software 42 * without specific prior written permission. 43 * 44 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 45 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 46 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 47 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 48 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 49 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 50 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 51 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 52 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 53 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 54 * SUCH DAMAGE. 55 * 56 * @(#)slcompress.c 8.2 (Berkeley) 4/16/94 57 */ 58 59/* 60 * Routines to compress and uncompess tcp packets (for transmission 61 * over low speed serial lines. 62 * 63 * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989: 64 * - Initial distribution. 65 * 66 */ 67 68#include <sys/param.h> 69#include <sys/mbuf.h> 70#include <sys/systm.h> 71 72#include <netinet/in.h> 73#include <netinet/in_systm.h> 74#include <netinet/ip.h> 75#include <netinet/tcp.h> 76 77#include "slcompress.h" 78 79#ifndef SL_NO_STATS 80#define INCR(counter) ++comp->counter; 81#else 82#define INCR(counter) 83#endif 84 85#define BCMP(p1, p2, n) bcmp((char *)(p1), (char *)(p2), (int)(n)) 86#define BCOPY(p1, p2, n) bcopy((char *)(p1), (char *)(p2), (int)(n)) 87#ifndef KERNEL 88#define ovbcopy bcopy 89#endif 90 91/* Wcast-align fix - cast away alignment warning when buffer is aligned */ 92#define ALIGNED_CAST(type) (type)(void *) 93 94 95void 96sl_compress_init(comp, max_state) 97 struct slcompress *comp; 98 int max_state; 99{ 100 register u_int i; 101 register struct cstate *tstate = comp->tstate; 102 103 if (max_state == -1) { 104 max_state = MAX_STATES - 1; 105 bzero((char *)comp, sizeof(*comp)); 106 } else { 107 /* Don't reset statistics */ 108 bzero((char *)comp->tstate, sizeof(comp->tstate)); 109 bzero((char *)comp->rstate, sizeof(comp->rstate)); 110 } 111 for (i = max_state; i > 0; --i) { 112 tstate[i].cs_id = i; 113 tstate[i].cs_next = &tstate[i - 1]; 114 } 115 tstate[0].cs_next = &tstate[max_state]; 116 tstate[0].cs_id = 0; 117 comp->last_cs = &tstate[0]; 118 comp->last_recv = 255; 119 comp->last_xmit = 255; 120 comp->flags = SLF_TOSS; 121} 122 123 124/* ENCODE encodes a number that is known to be non-zero. ENCODEZ 125 * checks for zero (since zero has to be encoded in the long, 3 byte 126 * form). 127 */ 128#define ENCODE(n) { \ 129 if ((u_int16_t)(n) >= 256) { \ 130 *cp++ = 0; \ 131 cp[1] = (n); \ 132 cp[0] = (n) >> 8; \ 133 cp += 2; \ 134 } else { \ 135 *cp++ = (n); \ 136 } \ 137} 138#define ENCODEZ(n) { \ 139 if ((u_int16_t)(n) >= 256 || (u_int16_t)(n) == 0) { \ 140 *cp++ = 0; \ 141 cp[1] = (n); \ 142 cp[0] = (n) >> 8; \ 143 cp += 2; \ 144 } else { \ 145 *cp++ = (n); \ 146 } \ 147} 148 149#define DECODEL(f) { \ 150 if (*cp == 0) {\ 151 (f) = htonl(ntohl(f) + ((cp[1] << 8) | cp[2])); \ 152 cp += 3; \ 153 } else { \ 154 (f) = htonl(ntohl(f) + (u_int32_t)*cp++); \ 155 } \ 156} 157 158#define DECODES(f) { \ 159 if (*cp == 0) {\ 160 (f) = htons(ntohs(f) + ((cp[1] << 8) | cp[2])); \ 161 cp += 3; \ 162 } else { \ 163 (f) = htons(ntohs(f) + (u_int32_t)*cp++); \ 164 } \ 165} 166 167#define DECODEU(f) { \ 168 if (*cp == 0) {\ 169 (f) = htons((cp[1] << 8) | cp[2]); \ 170 cp += 3; \ 171 } else { \ 172 (f) = htons((u_int32_t)*cp++); \ 173 } \ 174} 175 176u_int 177sl_compress_tcp(m, ip, comp, compress_cid) 178 mbuf_t m; 179 register struct ip *ip; 180 struct slcompress *comp; 181 int compress_cid; 182{ 183 register struct cstate *cs = comp->last_cs->cs_next; 184 register u_int hlen = ip->ip_hl; 185 register struct tcphdr *oth; 186 register struct tcphdr *th; 187 register u_int deltaS, deltaA; 188 register u_int changes = 0; 189 u_char new_seq[16]; 190 register u_char *cp = new_seq; 191 192 /* 193 * Bail if this is an IP fragment or if the TCP packet isn't 194 * `compressible' (i.e., ACK isn't set or some other control bit is 195 * set). (We assume that the caller has already made sure the 196 * packet is IP proto TCP). 197 */ 198 if ((ip->ip_off & htons(0x3fff)) || mbuf_len(m) < 40) 199 return (TYPE_IP); 200 201 th = (struct tcphdr *)&((int32_t *)ip)[hlen]; 202 if ((th->th_flags & (TH_SYN|TH_FIN|TH_RST|TH_ACK)) != TH_ACK) 203 return (TYPE_IP); 204 /* 205 * Packet is compressible -- we're going to send either a 206 * COMPRESSED_TCP or UNCOMPRESSED_TCP packet. Either way we need 207 * to locate (or create) the connection state. Special case the 208 * most recently used connection since it's most likely to be used 209 * again & we don't have to do any reordering if it's used. 210 */ 211 INCR(sls_packets) 212 if (ip->ip_src.s_addr != cs->cs_ip.ip_src.s_addr || 213 ip->ip_dst.s_addr != cs->cs_ip.ip_dst.s_addr || 214 *(int32_t *)th != ((int32_t *)&cs->cs_ip)[cs->cs_ip.ip_hl]) { 215 /* 216 * Wasn't the first -- search for it. 217 * 218 * States are kept in a circularly linked list with 219 * last_cs pointing to the end of the list. The 220 * list is kept in lru order by moving a state to the 221 * head of the list whenever it is referenced. Since 222 * the list is short and, empirically, the connection 223 * we want is almost always near the front, we locate 224 * states via linear search. If we don't find a state 225 * for the datagram, the oldest state is (re-)used. 226 */ 227 register struct cstate *lcs; 228 register struct cstate *lastcs = comp->last_cs; 229 230 do { 231 lcs = cs; cs = cs->cs_next; 232 INCR(sls_searches) 233 if (ip->ip_src.s_addr == cs->cs_ip.ip_src.s_addr 234 && ip->ip_dst.s_addr == cs->cs_ip.ip_dst.s_addr 235 && *(int32_t *)th == 236 ((int32_t *)&cs->cs_ip)[cs->cs_ip.ip_hl]) 237 goto found; 238 } while (cs != lastcs); 239 240 /* 241 * Didn't find it -- re-use oldest cstate. Send an 242 * uncompressed packet that tells the other side what 243 * connection number we're using for this conversation. 244 * Note that since the state list is circular, the oldest 245 * state points to the newest and we only need to set 246 * last_cs to update the lru linkage. 247 */ 248 INCR(sls_misses) 249 comp->last_cs = lcs; 250 hlen += th->th_off; 251 hlen <<= 2; 252 if (hlen > mbuf_len(m)) 253 return TYPE_IP; 254 goto uncompressed; 255 256 found: 257 /* 258 * Found it -- move to the front on the connection list. 259 */ 260 if (cs == lastcs) 261 comp->last_cs = lcs; 262 else { 263 lcs->cs_next = cs->cs_next; 264 cs->cs_next = lastcs->cs_next; 265 lastcs->cs_next = cs; 266 } 267 } 268 269 /* 270 * Make sure that only what we expect to change changed. The first 271 * line of the `if' checks the IP protocol version, header length & 272 * type of service. The 2nd line checks the "Don't fragment" bit. 273 * The 3rd line checks the time-to-live and protocol (the protocol 274 * check is unnecessary but costless). The 4th line checks the TCP 275 * header length. The 5th line checks IP options, if any. The 6th 276 * line checks TCP options, if any. If any of these things are 277 * different between the previous & current datagram, we send the 278 * current datagram `uncompressed'. 279 */ 280 oth = (struct tcphdr *)&((int32_t *)&cs->cs_ip)[hlen]; 281 deltaS = hlen; 282 hlen += th->th_off; 283 hlen <<= 2; 284 if (hlen > mbuf_len(m)) 285 return TYPE_IP; 286 287 if (((u_int16_t *)ip)[0] != ((u_int16_t *)&cs->cs_ip)[0] || 288 ((u_int16_t *)ip)[3] != ((u_int16_t *)&cs->cs_ip)[3] || 289 ((u_int16_t *)ip)[4] != ((u_int16_t *)&cs->cs_ip)[4] || 290 th->th_off != oth->th_off || 291 (deltaS > 5 && 292 BCMP(ip + 1, &cs->cs_ip + 1, (deltaS - 5) << 2)) || 293 (th->th_off > 5 && 294 BCMP(th + 1, oth + 1, (th->th_off - 5) << 2))) 295 goto uncompressed; 296 297 /* 298 * Figure out which of the changing fields changed. The 299 * receiver expects changes in the order: urgent, window, 300 * ack, seq (the order minimizes the number of temporaries 301 * needed in this section of code). 302 */ 303 if (th->th_flags & TH_URG) { 304 deltaS = ntohs(th->th_urp); 305 ENCODEZ(deltaS); 306 changes |= NEW_U; 307 } else if (th->th_urp != oth->th_urp) 308 /* argh! URG not set but urp changed -- a sensible 309 * implementation should never do this but RFC793 310 * doesn't prohibit the change so we have to deal 311 * with it. */ 312 goto uncompressed; 313 314 deltaS = (u_int16_t)(ntohs(th->th_win) - ntohs(oth->th_win)); 315 if (deltaS) { 316 ENCODE(deltaS); 317 changes |= NEW_W; 318 } 319 320 deltaA = ntohl(th->th_ack) - ntohl(oth->th_ack); 321 if (deltaA) { 322 if (deltaA > 0xffff) 323 goto uncompressed; 324 ENCODE(deltaA); 325 changes |= NEW_A; 326 } 327 328 deltaS = ntohl(th->th_seq) - ntohl(oth->th_seq); 329 if (deltaS) { 330 if (deltaS > 0xffff) 331 goto uncompressed; 332 ENCODE(deltaS); 333 changes |= NEW_S; 334 } 335 336 switch(changes) { 337 338 case 0: 339 /* 340 * Nothing changed. If this packet contains data and the 341 * last one didn't, this is probably a data packet following 342 * an ack (normal on an interactive connection) and we send 343 * it compressed. Otherwise it's probably a retransmit, 344 * retransmitted ack or window probe. Send it uncompressed 345 * in case the other side missed the compressed version. 346 */ 347 if (ip->ip_len != cs->cs_ip.ip_len && 348 ntohs(cs->cs_ip.ip_len) == hlen) 349 break; 350 351 /* (fall through) */ 352 353 case SPECIAL_I: 354 case SPECIAL_D: 355 /* 356 * actual changes match one of our special case encodings -- 357 * send packet uncompressed. 358 */ 359 goto uncompressed; 360 361 case NEW_S|NEW_A: 362 if (deltaS == deltaA && 363 deltaS == ntohs(cs->cs_ip.ip_len) - hlen) { 364 /* special case for echoed terminal traffic */ 365 changes = SPECIAL_I; 366 cp = new_seq; 367 } 368 break; 369 370 case NEW_S: 371 if (deltaS == ntohs(cs->cs_ip.ip_len) - hlen) { 372 /* special case for data xfer */ 373 changes = SPECIAL_D; 374 cp = new_seq; 375 } 376 break; 377 } 378 379 deltaS = ntohs(ip->ip_id) - ntohs(cs->cs_ip.ip_id); 380 if (deltaS != 1) { 381 ENCODEZ(deltaS); 382 changes |= NEW_I; 383 } 384 if (th->th_flags & TH_PUSH) 385 changes |= TCP_PUSH_BIT; 386 /* 387 * Grab the cksum before we overwrite it below. Then update our 388 * state with this packet's header. 389 */ 390 deltaA = ntohs(th->th_sum); 391 BCOPY(ip, &cs->cs_ip, hlen); 392 393 /* 394 * We want to use the original packet as our compressed packet. 395 * (cp - new_seq) is the number of bytes we need for compressed 396 * sequence numbers. In addition we need one byte for the change 397 * mask, one for the connection id and two for the tcp checksum. 398 * So, (cp - new_seq) + 4 bytes of header are needed. hlen is how 399 * many bytes of the original packet to toss so subtract the two to 400 * get the new packet size. 401 */ 402 deltaS = cp - new_seq; 403 cp = (u_char *)ip; 404 if (compress_cid == 0 || comp->last_xmit != cs->cs_id) { 405 comp->last_xmit = cs->cs_id; 406 hlen -= deltaS + 4; 407 cp += hlen; 408 *cp++ = changes | NEW_C; 409 *cp++ = cs->cs_id; 410 } else { 411 hlen -= deltaS + 3; 412 cp += hlen; 413 *cp++ = changes; 414 } 415 mbuf_setdata(m, mbuf_data(m) + hlen, mbuf_len(m) - hlen); 416 *cp++ = deltaA >> 8; 417 *cp++ = deltaA; 418 BCOPY(new_seq, cp, deltaS); 419 INCR(sls_compressed) 420 return (TYPE_COMPRESSED_TCP); 421 422 /* 423 * Update connection state cs & send uncompressed packet ('uncompressed' 424 * means a regular ip/tcp packet but with the 'conversation id' we hope 425 * to use on future compressed packets in the protocol field). 426 */ 427uncompressed: 428 BCOPY(ip, &cs->cs_ip, hlen); 429 ip->ip_p = cs->cs_id; 430 comp->last_xmit = cs->cs_id; 431 return (TYPE_UNCOMPRESSED_TCP); 432} 433 434 435int 436sl_uncompress_tcp(bufp, len, type, comp) 437 u_char **bufp; 438 int len; 439 u_int type; 440 struct slcompress *comp; 441{ 442 u_char *hdr, *cp; 443 int hlen, vjlen; 444 445 cp = bufp? *bufp: NULL; 446 vjlen = sl_uncompress_tcp_core(cp, len, len, type, comp, &hdr, (uint32_t *)&hlen); 447 if (vjlen < 0) 448 return (0); /* error */ 449 if (vjlen == 0) 450 return (len); /* was uncompressed already */ 451 452 cp += vjlen; 453 len -= vjlen; 454 455 /* 456 * At this point, cp points to the first byte of data in the 457 * packet. If we're not aligned on a 4-byte boundary, copy the 458 * data down so the ip & tcp headers will be aligned. Then back up 459 * cp by the tcp/ip header length to make room for the reconstructed 460 * header (we assume the packet we were handed has enough space to 461 * prepend 128 bytes of header). 462 */ 463 // Start APPLE 464// if ((intptr_t)cp & 3) { 465 // if (len > 0) 466// (void) ovbcopy(cp, (caddr_t)((intptr_t)cp &~ 3), len); 467// cp = (u_char *)((intptr_t)cp &~ 3); 468// } 469 if ((uintptr_t)cp & 3) { 470 if (len > 0) 471 (void) ovbcopy(cp, (caddr_t)((uintptr_t)cp &~ 3), len); 472 cp = (u_char *)((uintptr_t)cp &~ 3); 473 } 474 // End APPLE 475 cp -= hlen; 476 len += hlen; 477 BCOPY(hdr, cp, hlen); 478 479 if (bufp) 480 *bufp = cp; 481 return (len); 482} 483 484/* 485 * Uncompress a packet of total length total_len. The first buflen 486 * bytes are at buf; this must include the entire (compressed or 487 * uncompressed) TCP/IP header. This procedure returns the length 488 * of the VJ header, with a pointer to the uncompressed IP header 489 * in *hdrp and its length in *hlenp. 490 */ 491int 492sl_uncompress_tcp_core(buf, buflen, total_len, type, comp, hdrp, hlenp) 493 u_char *buf; 494 int buflen, total_len; 495 u_int type; 496 struct slcompress *comp; 497 u_char **hdrp; 498 u_int *hlenp; 499{ 500 register u_char *cp; 501 register u_int hlen, changes; 502 register struct tcphdr *th; 503 register struct cstate *cs; 504 register struct ip *ip; 505 register u_int16_t *bp; 506 register u_int vjlen; 507 508 switch (type) { 509 510 case TYPE_UNCOMPRESSED_TCP: 511 ip = (struct ip *)(void*) buf; // Wcast-align fix (void*) - used only to access 1 byte or less 512 if (ip->ip_p >= MAX_STATES) 513 goto bad; 514 cs = &comp->rstate[comp->last_recv = ip->ip_p]; 515 comp->flags &=~ SLF_TOSS; 516 ip->ip_p = IPPROTO_TCP; 517 /* 518 * Calculate the size of the TCP/IP header and make sure that 519 * we don't overflow the space we have available for it. 520 */ 521 hlen = ip->ip_hl << 2; 522 if (hlen + sizeof(struct tcphdr) > buflen) 523 goto bad; 524 hlen += ((struct tcphdr *)(void*)&((char *)ip)[hlen])->th_off << 2; // Wcast-align fix (void*) - used for access to 4 bits 525 if (hlen > MAX_HDR || hlen > buflen) 526 goto bad; 527 BCOPY(ip, &cs->cs_ip, hlen); 528 cs->cs_hlen = hlen; 529 INCR(sls_uncompressedin) 530 *hdrp = (u_char *) &cs->cs_ip; 531 *hlenp = hlen; 532 return (0); 533 534 default: 535 goto bad; 536 537 case TYPE_COMPRESSED_TCP: 538 break; 539 } 540 /* We've got a compressed packet. */ 541 INCR(sls_compressedin) 542 cp = buf; 543 changes = *cp++; 544 if (changes & NEW_C) { 545 /* Make sure the state index is in range, then grab the state. 546 * If we have a good state index, clear the 'discard' flag. */ 547 if (*cp >= MAX_STATES) 548 goto bad; 549 550 comp->flags &=~ SLF_TOSS; 551 comp->last_recv = *cp++; 552 } else { 553 /* this packet has an implicit state index. If we've 554 * had a line error since the last time we got an 555 * explicit state index, we have to toss the packet. */ 556 if (comp->flags & SLF_TOSS) { 557 INCR(sls_tossed) 558 return (-1); 559 } 560 } 561 cs = &comp->rstate[comp->last_recv]; 562 hlen = cs->cs_ip.ip_hl << 2; 563 th = ALIGNED_CAST(struct tcphdr *)&((u_char *)&cs->cs_ip)[hlen]; 564 th->th_sum = htons((*cp << 8) | cp[1]); 565 cp += 2; 566 if (changes & TCP_PUSH_BIT) 567 th->th_flags |= TH_PUSH; 568 else 569 th->th_flags &=~ TH_PUSH; 570 571 switch (changes & SPECIALS_MASK) { 572 case SPECIAL_I: 573 { 574 register u_int i = ntohs(cs->cs_ip.ip_len) - cs->cs_hlen; 575 th->th_ack = htonl(ntohl(th->th_ack) + i); 576 th->th_seq = htonl(ntohl(th->th_seq) + i); 577 } 578 break; 579 580 case SPECIAL_D: 581 th->th_seq = htonl(ntohl(th->th_seq) + ntohs(cs->cs_ip.ip_len) 582 - cs->cs_hlen); 583 break; 584 585 default: 586 if (changes & NEW_U) { 587 th->th_flags |= TH_URG; 588 DECODEU(th->th_urp) 589 } else 590 th->th_flags &=~ TH_URG; 591 if (changes & NEW_W) 592 DECODES(th->th_win) 593 if (changes & NEW_A) 594 DECODEL(th->th_ack) 595 if (changes & NEW_S) 596 DECODEL(th->th_seq) 597 break; 598 } 599 if (changes & NEW_I) { 600 DECODES(cs->cs_ip.ip_id) 601 } else 602 cs->cs_ip.ip_id = htons(ntohs(cs->cs_ip.ip_id) + 1); 603 604 /* 605 * At this point, cp points to the first byte of data in the 606 * packet. Fill in the IP total length and update the IP 607 * header checksum. 608 */ 609 vjlen = cp - buf; 610 buflen -= vjlen; 611 if (buflen < 0) 612 /* we must have dropped some characters (crc should detect 613 * this but the old slip framing won't) */ 614 goto bad; 615 616 total_len += cs->cs_hlen - vjlen; 617 cs->cs_ip.ip_len = htons(total_len); 618 619 /* recompute the ip header checksum */ 620 bp = (u_int16_t *) &cs->cs_ip; 621 cs->cs_ip.ip_sum = 0; 622 for (changes = 0; hlen > 0; hlen -= 2) 623 changes += *bp++; 624 changes = (changes & 0xffff) + (changes >> 16); 625 changes = (changes & 0xffff) + (changes >> 16); 626 cs->cs_ip.ip_sum = ~ changes; 627 628 *hdrp = (u_char *) &cs->cs_ip; 629 *hlenp = cs->cs_hlen; 630 return vjlen; 631 632bad: 633 comp->flags |= SLF_TOSS; 634 INCR(sls_errorin) 635 return (-1); 636} 637