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1.1 root 1: /*
2: * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
3: *
4: * @APPLE_LICENSE_HEADER_START@
5: *
6: * The contents of this file constitute Original Code as defined in and
7: * are subject to the Apple Public Source License Version 1.1 (the
8: * "License"). You may not use this file except in compliance with the
9: * License. Please obtain a copy of the License at
10: * http://www.apple.com/publicsource and read it before using this file.
11: *
12: * This Original Code and all software distributed under the License are
13: * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
14: * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
15: * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
16: * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT. Please see the
17: * License for the specific language governing rights and limitations
18: * under the License.
19: *
20: * @APPLE_LICENSE_HEADER_END@
21: */
22: /*-
23: * Copyright (c) 1989, 1993, 1994
24: * The Regents of the University of California. All rights reserved.
25: *
26: * Redistribution and use in source and binary forms, with or without
27: * modification, are permitted provided that the following conditions
28: * are met:
29: * 1. Redistributions of source code must retain the above copyright
30: * notice, this list of conditions and the following disclaimer.
31: * 2. Redistributions in binary form must reproduce the above copyright
32: * notice, this list of conditions and the following disclaimer in the
33: * documentation and/or other materials provided with the distribution.
34: * 3. All advertising materials mentioning features or use of this software
35: * must display the following acknowledgement:
36: * This product includes software developed by the University of
37: * California, Berkeley and its contributors.
38: * 4. Neither the name of the University nor the names of its contributors
39: * may be used to endorse or promote products derived from this software
40: * without specific prior written permission.
41: *
42: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
43: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
44: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
45: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
46: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
47: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
48: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
49: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
50: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
51: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
52: * SUCH DAMAGE.
53: *
54: * @(#)slcompress.c 8.2 (Berkeley) 4/16/94
55: */
56:
57: /*
58: * Routines to compress and uncompess tcp packets (for transmission
59: * over low speed serial lines.
60: *
61: * Van Jacobson ([email protected]), Dec 31, 1989:
62: * - Initial distribution.
63: *
64: */
65:
66: #include <sys/param.h>
67: #include <sys/mbuf.h>
68: #include <sys/systm.h>
69:
70: #include <netinet/in.h>
71: #include <netinet/in_systm.h>
72: #include <netinet/ip.h>
73: #include <netinet/tcp.h>
74:
75: #include <net/slcompress.h>
76:
77: #ifndef SL_NO_STATS
78: #define INCR(counter) ++comp->counter;
79: #else
80: #define INCR(counter)
81: #endif
82:
83: #define BCMP(p1, p2, n) bcmp((char *)(p1), (char *)(p2), (int)(n))
84: #define BCOPY(p1, p2, n) bcopy((char *)(p1), (char *)(p2), (int)(n))
85: #ifndef KERNEL
86: #define ovbcopy bcopy
87: #endif
88:
89: void
90: sl_compress_init(comp, max_state)
91: struct slcompress *comp;
92: int max_state;
93: {
94: register u_int i;
95: register struct cstate *tstate = comp->tstate;
96:
97: if (max_state == -1) {
98: max_state = MAX_STATES - 1;
99: bzero((char *)comp, sizeof(*comp));
100: } else {
101: /* Don't reset statistics */
102: bzero((char *)comp->tstate, sizeof(comp->tstate));
103: bzero((char *)comp->rstate, sizeof(comp->rstate));
104: }
105: for (i = max_state; i > 0; --i) {
106: tstate[i].cs_id = i;
107: tstate[i].cs_next = &tstate[i - 1];
108: }
109: tstate[0].cs_next = &tstate[max_state];
110: tstate[0].cs_id = 0;
111: comp->last_cs = &tstate[0];
112: comp->last_recv = 255;
113: comp->last_xmit = 255;
114: comp->flags = SLF_TOSS;
115: }
116:
117:
118: /* ENCODE encodes a number that is known to be non-zero. ENCODEZ
119: * checks for zero (since zero has to be encoded in the long, 3 byte
120: * form).
121: */
122: #define ENCODE(n) { \
123: if ((u_int16_t)(n) >= 256) { \
124: *cp++ = 0; \
125: cp[1] = (n); \
126: cp[0] = (n) >> 8; \
127: cp += 2; \
128: } else { \
129: *cp++ = (n); \
130: } \
131: }
132: #define ENCODEZ(n) { \
133: if ((u_int16_t)(n) >= 256 || (u_int16_t)(n) == 0) { \
134: *cp++ = 0; \
135: cp[1] = (n); \
136: cp[0] = (n) >> 8; \
137: cp += 2; \
138: } else { \
139: *cp++ = (n); \
140: } \
141: }
142:
143: #define DECODEL(f) { \
144: if (*cp == 0) {\
145: (f) = htonl(ntohl(f) + ((cp[1] << 8) | cp[2])); \
146: cp += 3; \
147: } else { \
148: (f) = htonl(ntohl(f) + (u_int32_t)*cp++); \
149: } \
150: }
151:
152: #define DECODES(f) { \
153: if (*cp == 0) {\
154: (f) = htons(ntohs(f) + ((cp[1] << 8) | cp[2])); \
155: cp += 3; \
156: } else { \
157: (f) = htons(ntohs(f) + (u_int32_t)*cp++); \
158: } \
159: }
160:
161: #define DECODEU(f) { \
162: if (*cp == 0) {\
163: (f) = htons((cp[1] << 8) | cp[2]); \
164: cp += 3; \
165: } else { \
166: (f) = htons((u_int32_t)*cp++); \
167: } \
168: }
169:
170: u_int
171: sl_compress_tcp(m, ip, comp, compress_cid)
172: struct mbuf *m;
173: register struct ip *ip;
174: struct slcompress *comp;
175: int compress_cid;
176: {
177: register struct cstate *cs = comp->last_cs->cs_next;
178: register u_int hlen = ip->ip_hl;
179: register struct tcphdr *oth;
180: register struct tcphdr *th;
181: register u_int deltaS, deltaA;
182: register u_int changes = 0;
183: u_char new_seq[16];
184: register u_char *cp = new_seq;
185:
186: /*
187: * Bail if this is an IP fragment or if the TCP packet isn't
188: * `compressible' (i.e., ACK isn't set or some other control bit is
189: * set). (We assume that the caller has already made sure the
190: * packet is IP proto TCP).
191: */
192: if ((ip->ip_off & htons(0x3fff)) || m->m_len < 40)
193: return (TYPE_IP);
194:
195: th = (struct tcphdr *)&((int32_t *)ip)[hlen];
196: if ((th->th_flags & (TH_SYN|TH_FIN|TH_RST|TH_ACK)) != TH_ACK)
197: return (TYPE_IP);
198: /*
199: * Packet is compressible -- we're going to send either a
200: * COMPRESSED_TCP or UNCOMPRESSED_TCP packet. Either way we need
201: * to locate (or create) the connection state. Special case the
202: * most recently used connection since it's most likely to be used
203: * again & we don't have to do any reordering if it's used.
204: */
205: INCR(sls_packets)
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 != ((int32_t *)&cs->cs_ip)[cs->cs_ip.ip_hl]) {
209: /*
210: * Wasn't the first -- search for it.
211: *
212: * States are kept in a circularly linked list with
213: * last_cs pointing to the end of the list. The
214: * list is kept in lru order by moving a state to the
215: * head of the list whenever it is referenced. Since
216: * the list is short and, empirically, the connection
217: * we want is almost always near the front, we locate
218: * states via linear search. If we don't find a state
219: * for the datagram, the oldest state is (re-)used.
220: */
221: register struct cstate *lcs;
222: register struct cstate *lastcs = comp->last_cs;
223:
224: do {
225: lcs = cs; cs = cs->cs_next;
226: INCR(sls_searches)
227: if (ip->ip_src.s_addr == cs->cs_ip.ip_src.s_addr
228: && ip->ip_dst.s_addr == cs->cs_ip.ip_dst.s_addr
229: && *(int32_t *)th ==
230: ((int32_t *)&cs->cs_ip)[cs->cs_ip.ip_hl])
231: goto found;
232: } while (cs != lastcs);
233:
234: /*
235: * Didn't find it -- re-use oldest cstate. Send an
236: * uncompressed packet that tells the other side what
237: * connection number we're using for this conversation.
238: * Note that since the state list is circular, the oldest
239: * state points to the newest and we only need to set
240: * last_cs to update the lru linkage.
241: */
242: INCR(sls_misses)
243: comp->last_cs = lcs;
244: hlen += th->th_off;
245: hlen <<= 2;
246: if (hlen > m->m_len)
247: return TYPE_IP;
248: goto uncompressed;
249:
250: found:
251: /*
252: * Found it -- move to the front on the connection list.
253: */
254: if (cs == lastcs)
255: comp->last_cs = lcs;
256: else {
257: lcs->cs_next = cs->cs_next;
258: cs->cs_next = lastcs->cs_next;
259: lastcs->cs_next = cs;
260: }
261: }
262:
263: /*
264: * Make sure that only what we expect to change changed. The first
265: * line of the `if' checks the IP protocol version, header length &
266: * type of service. The 2nd line checks the "Don't fragment" bit.
267: * The 3rd line checks the time-to-live and protocol (the protocol
268: * check is unnecessary but costless). The 4th line checks the TCP
269: * header length. The 5th line checks IP options, if any. The 6th
270: * line checks TCP options, if any. If any of these things are
271: * different between the previous & current datagram, we send the
272: * current datagram `uncompressed'.
273: */
274: oth = (struct tcphdr *)&((int32_t *)&cs->cs_ip)[hlen];
275: deltaS = hlen;
276: hlen += th->th_off;
277: hlen <<= 2;
278: if (hlen > m->m_len)
279: return TYPE_IP;
280:
281: if (((u_int16_t *)ip)[0] != ((u_int16_t *)&cs->cs_ip)[0] ||
282: ((u_int16_t *)ip)[3] != ((u_int16_t *)&cs->cs_ip)[3] ||
283: ((u_int16_t *)ip)[4] != ((u_int16_t *)&cs->cs_ip)[4] ||
284: th->th_off != oth->th_off ||
285: (deltaS > 5 &&
286: BCMP(ip + 1, &cs->cs_ip + 1, (deltaS - 5) << 2)) ||
287: (th->th_off > 5 &&
288: BCMP(th + 1, oth + 1, (th->th_off - 5) << 2)))
289: goto uncompressed;
290:
291: /*
292: * Figure out which of the changing fields changed. The
293: * receiver expects changes in the order: urgent, window,
294: * ack, seq (the order minimizes the number of temporaries
295: * needed in this section of code).
296: */
297: if (th->th_flags & TH_URG) {
298: deltaS = ntohs(th->th_urp);
299: ENCODEZ(deltaS);
300: changes |= NEW_U;
301: } else if (th->th_urp != oth->th_urp)
302: /* argh! URG not set but urp changed -- a sensible
303: * implementation should never do this but RFC793
304: * doesn't prohibit the change so we have to deal
305: * with it. */
306: goto uncompressed;
307:
308: deltaS = (u_int16_t)(ntohs(th->th_win) - ntohs(oth->th_win));
309: if (deltaS) {
310: ENCODE(deltaS);
311: changes |= NEW_W;
312: }
313:
314: deltaA = ntohl(th->th_ack) - ntohl(oth->th_ack);
315: if (deltaA) {
316: if (deltaA > 0xffff)
317: goto uncompressed;
318: ENCODE(deltaA);
319: changes |= NEW_A;
320: }
321:
322: deltaS = ntohl(th->th_seq) - ntohl(oth->th_seq);
323: if (deltaS) {
324: if (deltaS > 0xffff)
325: goto uncompressed;
326: ENCODE(deltaS);
327: changes |= NEW_S;
328: }
329:
330: switch(changes) {
331:
332: case 0:
333: /*
334: * Nothing changed. If this packet contains data and the
335: * last one didn't, this is probably a data packet following
336: * an ack (normal on an interactive connection) and we send
337: * it compressed. Otherwise it's probably a retransmit,
338: * retransmitted ack or window probe. Send it uncompressed
339: * in case the other side missed the compressed version.
340: */
341: if (ip->ip_len != cs->cs_ip.ip_len &&
342: ntohs(cs->cs_ip.ip_len) == hlen)
343: break;
344:
345: /* (fall through) */
346:
347: case SPECIAL_I:
348: case SPECIAL_D:
349: /*
350: * actual changes match one of our special case encodings --
351: * send packet uncompressed.
352: */
353: goto uncompressed;
354:
355: case NEW_S|NEW_A:
356: if (deltaS == deltaA &&
357: deltaS == ntohs(cs->cs_ip.ip_len) - hlen) {
358: /* special case for echoed terminal traffic */
359: changes = SPECIAL_I;
360: cp = new_seq;
361: }
362: break;
363:
364: case NEW_S:
365: if (deltaS == ntohs(cs->cs_ip.ip_len) - hlen) {
366: /* special case for data xfer */
367: changes = SPECIAL_D;
368: cp = new_seq;
369: }
370: break;
371: }
372:
373: deltaS = ntohs(ip->ip_id) - ntohs(cs->cs_ip.ip_id);
374: if (deltaS != 1) {
375: ENCODEZ(deltaS);
376: changes |= NEW_I;
377: }
378: if (th->th_flags & TH_PUSH)
379: changes |= TCP_PUSH_BIT;
380: /*
381: * Grab the cksum before we overwrite it below. Then update our
382: * state with this packet's header.
383: */
384: deltaA = ntohs(th->th_sum);
385: BCOPY(ip, &cs->cs_ip, hlen);
386:
387: /*
388: * We want to use the original packet as our compressed packet.
389: * (cp - new_seq) is the number of bytes we need for compressed
390: * sequence numbers. In addition we need one byte for the change
391: * mask, one for the connection id and two for the tcp checksum.
392: * So, (cp - new_seq) + 4 bytes of header are needed. hlen is how
393: * many bytes of the original packet to toss so subtract the two to
394: * get the new packet size.
395: */
396: deltaS = cp - new_seq;
397: cp = (u_char *)ip;
398: if (compress_cid == 0 || comp->last_xmit != cs->cs_id) {
399: comp->last_xmit = cs->cs_id;
400: hlen -= deltaS + 4;
401: cp += hlen;
402: *cp++ = changes | NEW_C;
403: *cp++ = cs->cs_id;
404: } else {
405: hlen -= deltaS + 3;
406: cp += hlen;
407: *cp++ = changes;
408: }
409: m->m_len -= hlen;
410: m->m_data += hlen;
411: *cp++ = deltaA >> 8;
412: *cp++ = deltaA;
413: BCOPY(new_seq, cp, deltaS);
414: INCR(sls_compressed)
415: return (TYPE_COMPRESSED_TCP);
416:
417: /*
418: * Update connection state cs & send uncompressed packet ('uncompressed'
419: * means a regular ip/tcp packet but with the 'conversation id' we hope
420: * to use on future compressed packets in the protocol field).
421: */
422: uncompressed:
423: BCOPY(ip, &cs->cs_ip, hlen);
424: ip->ip_p = cs->cs_id;
425: comp->last_xmit = cs->cs_id;
426: return (TYPE_UNCOMPRESSED_TCP);
427: }
428:
429:
430: int
431: sl_uncompress_tcp(bufp, len, type, comp)
432: u_char **bufp;
433: int len;
434: u_int type;
435: struct slcompress *comp;
436: {
437: u_char *hdr, *cp;
438: int hlen, vjlen;
439:
440: cp = bufp? *bufp: NULL;
441: vjlen = sl_uncompress_tcp_core(cp, len, len, type, comp, &hdr, &hlen);
442: if (vjlen < 0)
443: return (0); /* error */
444: if (vjlen == 0)
445: return (len); /* was uncompressed already */
446:
447: cp += vjlen;
448: len -= vjlen;
449:
450: /*
451: * At this point, cp points to the first byte of data in the
452: * packet. If we're not aligned on a 4-byte boundary, copy the
453: * data down so the ip & tcp headers will be aligned. Then back up
454: * cp by the tcp/ip header length to make room for the reconstructed
455: * header (we assume the packet we were handed has enough space to
456: * prepend 128 bytes of header).
457: */
458: if ((intptr_t)cp & 3) {
459: if (len > 0)
460: (void) ovbcopy(cp, (caddr_t)((intptr_t)cp &~ 3), len);
461: cp = (u_char *)((intptr_t)cp &~ 3);
462: }
463: cp -= hlen;
464: len += hlen;
465: BCOPY(hdr, cp, hlen);
466:
467: *bufp = cp;
468: return (len);
469: }
470:
471: /*
472: * Uncompress a packet of total length total_len. The first buflen
473: * bytes are at buf; this must include the entire (compressed or
474: * uncompressed) TCP/IP header. This procedure returns the length
475: * of the VJ header, with a pointer to the uncompressed IP header
476: * in *hdrp and its length in *hlenp.
477: */
478: int
479: sl_uncompress_tcp_core(buf, buflen, total_len, type, comp, hdrp, hlenp)
480: u_char *buf;
481: int buflen, total_len;
482: u_int type;
483: struct slcompress *comp;
484: u_char **hdrp;
485: u_int *hlenp;
486: {
487: register u_char *cp;
488: register u_int hlen, changes;
489: register struct tcphdr *th;
490: register struct cstate *cs;
491: register struct ip *ip;
492: register u_int16_t *bp;
493: register u_int vjlen;
494:
495: switch (type) {
496:
497: case TYPE_UNCOMPRESSED_TCP:
498: ip = (struct ip *) buf;
499: if (ip->ip_p >= MAX_STATES)
500: goto bad;
501: cs = &comp->rstate[comp->last_recv = ip->ip_p];
502: comp->flags &=~ SLF_TOSS;
503: ip->ip_p = IPPROTO_TCP;
504: /*
505: * Calculate the size of the TCP/IP header and make sure that
506: * we don't overflow the space we have available for it.
507: */
508: hlen = ip->ip_hl << 2;
509: if (hlen + sizeof(struct tcphdr) > buflen)
510: goto bad;
511: hlen += ((struct tcphdr *)&((char *)ip)[hlen])->th_off << 2;
512: if (hlen > MAX_HDR || hlen > buflen)
513: goto bad;
514: BCOPY(ip, &cs->cs_ip, hlen);
515: cs->cs_hlen = hlen;
516: INCR(sls_uncompressedin)
517: *hdrp = (u_char *) &cs->cs_ip;
518: *hlenp = hlen;
519: return (0);
520:
521: default:
522: goto bad;
523:
524: case TYPE_COMPRESSED_TCP:
525: break;
526: }
527: /* We've got a compressed packet. */
528: INCR(sls_compressedin)
529: cp = buf;
530: changes = *cp++;
531: if (changes & NEW_C) {
532: /* Make sure the state index is in range, then grab the state.
533: * If we have a good state index, clear the 'discard' flag. */
534: if (*cp >= MAX_STATES)
535: goto bad;
536:
537: comp->flags &=~ SLF_TOSS;
538: comp->last_recv = *cp++;
539: } else {
540: /* this packet has an implicit state index. If we've
541: * had a line error since the last time we got an
542: * explicit state index, we have to toss the packet. */
543: if (comp->flags & SLF_TOSS) {
544: INCR(sls_tossed)
545: return (-1);
546: }
547: }
548: cs = &comp->rstate[comp->last_recv];
549: hlen = cs->cs_ip.ip_hl << 2;
550: th = (struct tcphdr *)&((u_char *)&cs->cs_ip)[hlen];
551: th->th_sum = htons((*cp << 8) | cp[1]);
552: cp += 2;
553: if (changes & TCP_PUSH_BIT)
554: th->th_flags |= TH_PUSH;
555: else
556: th->th_flags &=~ TH_PUSH;
557:
558: switch (changes & SPECIALS_MASK) {
559: case SPECIAL_I:
560: {
561: register u_int i = ntohs(cs->cs_ip.ip_len) - cs->cs_hlen;
562: th->th_ack = htonl(ntohl(th->th_ack) + i);
563: th->th_seq = htonl(ntohl(th->th_seq) + i);
564: }
565: break;
566:
567: case SPECIAL_D:
568: th->th_seq = htonl(ntohl(th->th_seq) + ntohs(cs->cs_ip.ip_len)
569: - cs->cs_hlen);
570: break;
571:
572: default:
573: if (changes & NEW_U) {
574: th->th_flags |= TH_URG;
575: DECODEU(th->th_urp)
576: } else
577: th->th_flags &=~ TH_URG;
578: if (changes & NEW_W)
579: DECODES(th->th_win)
580: if (changes & NEW_A)
581: DECODEL(th->th_ack)
582: if (changes & NEW_S)
583: DECODEL(th->th_seq)
584: break;
585: }
586: if (changes & NEW_I) {
587: DECODES(cs->cs_ip.ip_id)
588: } else
589: cs->cs_ip.ip_id = htons(ntohs(cs->cs_ip.ip_id) + 1);
590:
591: /*
592: * At this point, cp points to the first byte of data in the
593: * packet. Fill in the IP total length and update the IP
594: * header checksum.
595: */
596: vjlen = cp - buf;
597: buflen -= vjlen;
598: if (buflen < 0)
599: /* we must have dropped some characters (crc should detect
600: * this but the old slip framing won't) */
601: goto bad;
602:
603: total_len += cs->cs_hlen - vjlen;
604: cs->cs_ip.ip_len = htons(total_len);
605:
606: /* recompute the ip header checksum */
607: bp = (u_int16_t *) &cs->cs_ip;
608: cs->cs_ip.ip_sum = 0;
609: for (changes = 0; hlen > 0; hlen -= 2)
610: changes += *bp++;
611: changes = (changes & 0xffff) + (changes >> 16);
612: changes = (changes & 0xffff) + (changes >> 16);
613: cs->cs_ip.ip_sum = ~ changes;
614:
615: *hdrp = (u_char *) &cs->cs_ip;
616: *hlenp = cs->cs_hlen;
617: return vjlen;
618:
619: bad:
620: comp->flags |= SLF_TOSS;
621: INCR(sls_errorin)
622: return (-1);
623: }
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