Commit | Line | Data |
---|---|---|
dbf0c423 | 1 | /* slcompress.c 7.6 90/06/28 */ |
11b5360c | 2 | /* |
11b5360c SL |
3 | * Routines to compress and uncompess tcp packets (for transmission |
4 | * over low speed serial lines. | |
5 | * | |
b06f22bd | 6 | * Copyright (c) 1989 Regents of the University of California. |
11b5360c | 7 | * All rights reserved. |
b06f22bd | 8 | * |
dbf0c423 | 9 | * %sccs.include.redist.c% |
b06f22bd SL |
10 | * |
11 | * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989: | |
12 | * - Initial distribution. | |
11b5360c | 13 | */ |
11b5360c | 14 | #ifndef lint |
b06f22bd | 15 | static char rcsid[] = "$Header: slcompress.c,v 1.19 89/12/31 08:52:59 van Exp $"; |
11b5360c SL |
16 | #endif |
17 | ||
18 | #include <sys/types.h> | |
19 | #include <sys/param.h> | |
20 | #include <sys/mbuf.h> | |
21 | #include <netinet/in.h> | |
22 | #include <netinet/in_systm.h> | |
23 | #include <netinet/ip.h> | |
24 | #include <netinet/tcp.h> | |
25 | ||
26 | #include "slcompress.h" | |
27 | ||
b06f22bd | 28 | #ifndef SL_NO_STATS |
1dbf8d66 MK |
29 | #define INCR(counter) ++comp->counter; |
30 | #else | |
31 | #define INCR(counter) | |
32 | #endif | |
11b5360c SL |
33 | |
34 | #define BCMP(p1, p2, n) bcmp((char *)(p1), (char *)(p2), (int)(n)) | |
35 | #define BCOPY(p1, p2, n) bcopy((char *)(p1), (char *)(p2), (int)(n)) | |
b06f22bd SL |
36 | #ifndef KERNEL |
37 | #define ovbcopy bcopy | |
38 | #endif | |
11b5360c | 39 | |
11b5360c SL |
40 | |
41 | void | |
42 | sl_compress_init(comp) | |
43 | struct slcompress *comp; | |
44 | { | |
45 | register u_int i; | |
46 | register struct cstate *tstate = comp->tstate; | |
47 | ||
48 | bzero((char *)comp, sizeof(*comp)); | |
49 | for (i = MAX_STATES - 1; i > 0; --i) { | |
50 | tstate[i].cs_id = i; | |
51 | tstate[i].cs_next = &tstate[i - 1]; | |
52 | } | |
53 | tstate[0].cs_next = &tstate[MAX_STATES - 1]; | |
54 | tstate[0].cs_id = 0; | |
55 | comp->last_cs = &tstate[0]; | |
56 | comp->last_recv = 255; | |
57 | comp->last_xmit = 255; | |
58 | } | |
59 | ||
60 | ||
61 | /* ENCODE encodes a number that is known to be non-zero. ENCODEZ | |
62 | * checks for zero (since zero has to be encoded in the long, 3 byte | |
63 | * form). | |
64 | */ | |
65 | #define ENCODE(n) { \ | |
66 | if ((u_short)(n) >= 256) { \ | |
67 | *cp++ = 0; \ | |
68 | cp[1] = (n); \ | |
69 | cp[0] = (n) >> 8; \ | |
70 | cp += 2; \ | |
71 | } else { \ | |
72 | *cp++ = (n); \ | |
73 | } \ | |
74 | } | |
75 | #define ENCODEZ(n) { \ | |
76 | if ((u_short)(n) >= 256 || (u_short)(n) == 0) { \ | |
77 | *cp++ = 0; \ | |
78 | cp[1] = (n); \ | |
79 | cp[0] = (n) >> 8; \ | |
80 | cp += 2; \ | |
81 | } else { \ | |
82 | *cp++ = (n); \ | |
83 | } \ | |
84 | } | |
85 | ||
86 | #define DECODEL(f) { \ | |
87 | if (*cp == 0) {\ | |
88 | (f) = htonl(ntohl(f) + ((cp[1] << 8) | cp[2])); \ | |
89 | cp += 3; \ | |
90 | } else { \ | |
91 | (f) = htonl(ntohl(f) + (u_long)*cp++); \ | |
92 | } \ | |
93 | } | |
94 | ||
95 | #define DECODES(f) { \ | |
96 | if (*cp == 0) {\ | |
97 | (f) = htons(ntohs(f) + ((cp[1] << 8) | cp[2])); \ | |
98 | cp += 3; \ | |
99 | } else { \ | |
100 | (f) = htons(ntohs(f) + (u_long)*cp++); \ | |
101 | } \ | |
102 | } | |
103 | ||
b06f22bd SL |
104 | #define DECODEU(f) { \ |
105 | if (*cp == 0) {\ | |
106 | (f) = htons((cp[1] << 8) | cp[2]); \ | |
107 | cp += 3; \ | |
108 | } else { \ | |
109 | (f) = htons((u_long)*cp++); \ | |
110 | } \ | |
111 | } | |
112 | ||
11b5360c SL |
113 | |
114 | u_char | |
b06f22bd | 115 | sl_compress_tcp(m, ip, comp, compress_cid) |
11b5360c SL |
116 | struct mbuf *m; |
117 | register struct ip *ip; | |
118 | struct slcompress *comp; | |
b06f22bd | 119 | int compress_cid; |
11b5360c SL |
120 | { |
121 | register struct cstate *cs = comp->last_cs->cs_next; | |
122 | register u_int hlen = ip->ip_hl; | |
123 | register struct tcphdr *oth; | |
124 | register struct tcphdr *th; | |
125 | register u_int deltaS, deltaA; | |
126 | register u_int changes = 0; | |
127 | u_char new_seq[16]; | |
128 | register u_char *cp = new_seq; | |
129 | ||
130 | /* | |
b06f22bd SL |
131 | * Bail if this is an IP fragment or if the TCP packet isn't |
132 | * `compressible' (i.e., ACK isn't set or some other control bit is | |
133 | * set). (We assume that the caller has already made sure the | |
134 | * packet is IP proto TCP). | |
11b5360c | 135 | */ |
b06f22bd | 136 | if ((ip->ip_off & htons(0x3fff)) || m->m_len < 40) |
11b5360c SL |
137 | return (TYPE_IP); |
138 | ||
139 | th = (struct tcphdr *)&((int *)ip)[hlen]; | |
140 | if ((th->th_flags & (TH_SYN|TH_FIN|TH_RST|TH_ACK)) != TH_ACK) | |
141 | return (TYPE_IP); | |
b06f22bd SL |
142 | /* |
143 | * Packet is compressible -- we're going to send either a | |
144 | * COMPRESSED_TCP or UNCOMPRESSED_TCP packet. Either way we need | |
145 | * to locate (or create) the connection state. Special case the | |
146 | * most recently used connection since it's most likely to be used | |
147 | * again & we don't have to do any reordering if it's used. | |
148 | */ | |
1dbf8d66 MK |
149 | INCR(sls_packets) |
150 | if (ip->ip_src.s_addr != cs->cs_ip.ip_src.s_addr || | |
151 | ip->ip_dst.s_addr != cs->cs_ip.ip_dst.s_addr || | |
152 | *(int *)th != ((int *)&cs->cs_ip)[cs->cs_ip.ip_hl]) { | |
11b5360c SL |
153 | /* |
154 | * Wasn't the first -- search for it. | |
155 | * | |
156 | * States are kept in a circularly linked list with | |
b06f22bd | 157 | * last_cs pointing to the end of the list. The |
11b5360c SL |
158 | * list is kept in lru order by moving a state to the |
159 | * head of the list whenever it is referenced. Since | |
160 | * the list is short and, empirically, the connection | |
161 | * we want is almost always near the front, we locate | |
162 | * states via linear search. If we don't find a state | |
b06f22bd | 163 | * for the datagram, the oldest state is (re-)used. |
11b5360c SL |
164 | */ |
165 | register struct cstate *lcs; | |
b06f22bd | 166 | register struct cstate *lastcs = comp->last_cs; |
11b5360c SL |
167 | |
168 | do { | |
169 | lcs = cs; cs = cs->cs_next; | |
1dbf8d66 | 170 | INCR(sls_searches) |
b06f22bd SL |
171 | if (ip->ip_src.s_addr == cs->cs_ip.ip_src.s_addr |
172 | && ip->ip_dst.s_addr == cs->cs_ip.ip_dst.s_addr | |
173 | && *(int *)th == ((int *)&cs->cs_ip)[cs->cs_ip.ip_hl]) | |
11b5360c | 174 | goto found; |
b06f22bd | 175 | } while (cs != lastcs); |
11b5360c SL |
176 | |
177 | /* | |
b06f22bd SL |
178 | * Didn't find it -- re-use oldest cstate. Send an |
179 | * uncompressed packet that tells the other side what | |
180 | * connection number we're using for this conversation. | |
181 | * Note that since the state list is circular, the oldest | |
182 | * state points to the newest and we only need to set | |
183 | * last_cs to update the lru linkage. | |
11b5360c | 184 | */ |
b06f22bd | 185 | INCR(sls_misses) |
11b5360c SL |
186 | comp->last_cs = lcs; |
187 | hlen += th->th_off; | |
188 | hlen <<= 2; | |
189 | goto uncompressed; | |
190 | ||
191 | found: | |
192 | /* | |
193 | * Found it -- move to the front on the connection list. | |
194 | */ | |
b06f22bd | 195 | if (cs == lastcs) |
11b5360c SL |
196 | comp->last_cs = lcs; |
197 | else { | |
198 | lcs->cs_next = cs->cs_next; | |
b06f22bd SL |
199 | cs->cs_next = lastcs->cs_next; |
200 | lastcs->cs_next = cs; | |
11b5360c SL |
201 | } |
202 | } | |
203 | ||
204 | /* | |
b06f22bd SL |
205 | * Make sure that only what we expect to change changed. The first |
206 | * line of the `if' checks the IP protocol version, header length & | |
207 | * type of service. The 2nd line checks the "Don't fragment" bit. | |
208 | * The 3rd line checks the time-to-live and protocol (the protocol | |
209 | * check is unnecessary but costless). The 4th line checks the TCP | |
210 | * header length. The 5th line checks IP options, if any. The 6th | |
211 | * line checks TCP options, if any. If any of these things are | |
212 | * different between the previous & current datagram, we send the | |
213 | * current datagram `uncompressed'. | |
11b5360c SL |
214 | */ |
215 | oth = (struct tcphdr *)&((int *)&cs->cs_ip)[hlen]; | |
216 | deltaS = hlen; | |
217 | hlen += th->th_off; | |
218 | hlen <<= 2; | |
219 | ||
220 | if (((u_short *)ip)[0] != ((u_short *)&cs->cs_ip)[0] || | |
b06f22bd | 221 | ((u_short *)ip)[3] != ((u_short *)&cs->cs_ip)[3] || |
11b5360c SL |
222 | ((u_short *)ip)[4] != ((u_short *)&cs->cs_ip)[4] || |
223 | th->th_off != oth->th_off || | |
224 | (deltaS > 5 && | |
225 | BCMP(ip + 1, &cs->cs_ip + 1, (deltaS - 5) << 2)) || | |
226 | (th->th_off > 5 && | |
227 | BCMP(th + 1, oth + 1, (th->th_off - 5) << 2))) | |
228 | goto uncompressed; | |
229 | ||
230 | /* | |
231 | * Figure out which of the changing fields changed. The | |
232 | * receiver expects changes in the order: urgent, window, | |
233 | * ack, seq (the order minimizes the number of temporaries | |
234 | * needed in this section of code). | |
235 | */ | |
236 | if (th->th_flags & TH_URG) { | |
237 | deltaS = ntohs(th->th_urp); | |
238 | ENCODEZ(deltaS); | |
239 | changes |= NEW_U; | |
240 | } else if (th->th_urp != oth->th_urp) | |
241 | /* argh! URG not set but urp changed -- a sensible | |
242 | * implementation should never do this but RFC793 | |
243 | * doesn't prohibit the change so we have to deal | |
b06f22bd | 244 | * with it. */ |
11b5360c SL |
245 | goto uncompressed; |
246 | ||
247 | if (deltaS = (u_short)(ntohs(th->th_win) - ntohs(oth->th_win))) { | |
248 | ENCODE(deltaS); | |
249 | changes |= NEW_W; | |
250 | } | |
251 | ||
252 | if (deltaA = ntohl(th->th_ack) - ntohl(oth->th_ack)) { | |
253 | if (deltaA > 0xffff) | |
254 | goto uncompressed; | |
255 | ENCODE(deltaA); | |
256 | changes |= NEW_A; | |
257 | } | |
258 | ||
259 | if (deltaS = ntohl(th->th_seq) - ntohl(oth->th_seq)) { | |
260 | if (deltaS > 0xffff) | |
261 | goto uncompressed; | |
262 | ENCODE(deltaS); | |
263 | changes |= NEW_S; | |
264 | } | |
265 | ||
266 | switch(changes) { | |
267 | ||
268 | case 0: | |
11b5360c | 269 | /* |
b06f22bd SL |
270 | * Nothing changed. If this packet contains data and the |
271 | * last one didn't, this is probably a data packet following | |
272 | * an ack (normal on an interactive connection) and we send | |
273 | * it compressed. Otherwise it's probably a retransmit, | |
274 | * retransmitted ack or window probe. Send it uncompressed | |
275 | * in case the other side missed the compressed version. | |
11b5360c | 276 | */ |
b06f22bd SL |
277 | if (ip->ip_len != cs->cs_ip.ip_len && |
278 | ntohs(cs->cs_ip.ip_len) == hlen) | |
279 | break; | |
280 | ||
281 | /* (fall through) */ | |
11b5360c SL |
282 | |
283 | case SPECIAL_I: | |
284 | case SPECIAL_D: | |
285 | /* | |
286 | * actual changes match one of our special case encodings -- | |
287 | * send packet uncompressed. | |
288 | */ | |
289 | goto uncompressed; | |
290 | ||
291 | case NEW_S|NEW_A: | |
292 | if (deltaS == deltaA && | |
293 | deltaS == ntohs(cs->cs_ip.ip_len) - hlen) { | |
294 | /* special case for echoed terminal traffic */ | |
295 | changes = SPECIAL_I; | |
296 | cp = new_seq; | |
297 | } | |
298 | break; | |
299 | ||
300 | case NEW_S: | |
301 | if (deltaS == ntohs(cs->cs_ip.ip_len) - hlen) { | |
302 | /* special case for data xfer */ | |
303 | changes = SPECIAL_D; | |
304 | cp = new_seq; | |
305 | } | |
306 | break; | |
307 | } | |
308 | ||
309 | deltaS = ntohs(ip->ip_id) - ntohs(cs->cs_ip.ip_id); | |
310 | if (deltaS != 1) { | |
311 | ENCODEZ(deltaS); | |
312 | changes |= NEW_I; | |
313 | } | |
314 | if (th->th_flags & TH_PUSH) | |
315 | changes |= TCP_PUSH_BIT; | |
316 | /* | |
317 | * Grab the cksum before we overwrite it below. Then update our | |
318 | * state with this packet's header. | |
319 | */ | |
320 | deltaA = ntohs(th->th_sum); | |
321 | BCOPY(ip, &cs->cs_ip, hlen); | |
322 | ||
323 | /* | |
324 | * We want to use the original packet as our compressed packet. | |
325 | * (cp - new_seq) is the number of bytes we need for compressed | |
326 | * sequence numbers. In addition we need one byte for the change | |
327 | * mask, one for the connection id and two for the tcp checksum. | |
328 | * So, (cp - new_seq) + 4 bytes of header are needed. hlen is how | |
329 | * many bytes of the original packet to toss so subtract the two to | |
330 | * get the new packet size. | |
331 | */ | |
332 | deltaS = cp - new_seq; | |
333 | cp = (u_char *)ip; | |
b06f22bd | 334 | if (compress_cid == 0 || comp->last_xmit != cs->cs_id) { |
11b5360c SL |
335 | comp->last_xmit = cs->cs_id; |
336 | hlen -= deltaS + 4; | |
1dbf8d66 | 337 | cp += hlen; |
1dbf8d66 | 338 | *cp++ = changes | NEW_C; |
11b5360c SL |
339 | *cp++ = cs->cs_id; |
340 | } else { | |
341 | hlen -= deltaS + 3; | |
1dbf8d66 | 342 | cp += hlen; |
1dbf8d66 | 343 | *cp++ = changes; |
11b5360c | 344 | } |
b06f22bd SL |
345 | m->m_len -= hlen; |
346 | m->m_data += hlen; | |
11b5360c SL |
347 | *cp++ = deltaA >> 8; |
348 | *cp++ = deltaA; | |
349 | BCOPY(new_seq, cp, deltaS); | |
1dbf8d66 | 350 | INCR(sls_compressed) |
11b5360c SL |
351 | return (TYPE_COMPRESSED_TCP); |
352 | ||
353 | /* | |
354 | * Update connection state cs & send uncompressed packet ('uncompressed' | |
355 | * means a regular ip/tcp packet but with the 'conversation id' we hope | |
356 | * to use on future compressed packets in the protocol field). | |
357 | */ | |
358 | uncompressed: | |
359 | BCOPY(ip, &cs->cs_ip, hlen); | |
360 | ip->ip_p = cs->cs_id; | |
361 | comp->last_xmit = cs->cs_id; | |
11b5360c SL |
362 | return (TYPE_UNCOMPRESSED_TCP); |
363 | } | |
364 | ||
11b5360c | 365 | |
1dbf8d66 MK |
366 | int |
367 | sl_uncompress_tcp(bufp, len, type, comp) | |
368 | u_char **bufp; | |
369 | int len; | |
370 | u_int type; | |
11b5360c SL |
371 | struct slcompress *comp; |
372 | { | |
373 | register u_char *cp; | |
374 | register u_int hlen, changes; | |
375 | register struct tcphdr *th; | |
376 | register struct cstate *cs; | |
377 | register struct ip *ip; | |
11b5360c SL |
378 | |
379 | switch (type) { | |
380 | ||
381 | case TYPE_UNCOMPRESSED_TCP: | |
1dbf8d66 | 382 | ip = (struct ip *) *bufp; |
b06f22bd SL |
383 | if (ip->ip_p >= MAX_STATES) |
384 | goto bad; | |
11b5360c SL |
385 | cs = &comp->rstate[comp->last_recv = ip->ip_p]; |
386 | comp->flags &=~ SLF_TOSS; | |
387 | ip->ip_p = IPPROTO_TCP; | |
388 | hlen = ip->ip_hl; | |
389 | hlen += ((struct tcphdr *)&((int *)ip)[hlen])->th_off; | |
390 | hlen <<= 2; | |
391 | BCOPY(ip, &cs->cs_ip, hlen); | |
392 | cs->cs_ip.ip_sum = 0; | |
393 | cs->cs_hlen = hlen; | |
1dbf8d66 MK |
394 | INCR(sls_uncompressedin) |
395 | return (len); | |
11b5360c | 396 | |
1dbf8d66 | 397 | default: |
b06f22bd | 398 | goto bad; |
11b5360c SL |
399 | |
400 | case TYPE_COMPRESSED_TCP: | |
11b5360c SL |
401 | break; |
402 | } | |
403 | /* We've got a compressed packet. */ | |
1dbf8d66 MK |
404 | INCR(sls_compressedin) |
405 | cp = *bufp; | |
11b5360c SL |
406 | changes = *cp++; |
407 | if (changes & NEW_C) { | |
408 | /* Make sure the state index is in range, then grab the state. | |
409 | * If we have a good state index, clear the 'discard' flag. */ | |
b06f22bd SL |
410 | if (*cp >= MAX_STATES) |
411 | goto bad; | |
412 | ||
11b5360c SL |
413 | comp->flags &=~ SLF_TOSS; |
414 | comp->last_recv = *cp++; | |
415 | } else { | |
416 | /* this packet has an implicit state index. If we've | |
417 | * had a line error since the last time we got an | |
418 | * explicit state index, we have to toss the packet. */ | |
1dbf8d66 MK |
419 | if (comp->flags & SLF_TOSS) { |
420 | INCR(sls_tossed) | |
421 | return (0); | |
422 | } | |
11b5360c SL |
423 | } |
424 | cs = &comp->rstate[comp->last_recv]; | |
425 | hlen = cs->cs_ip.ip_hl << 2; | |
426 | th = (struct tcphdr *)&((u_char *)&cs->cs_ip)[hlen]; | |
427 | th->th_sum = htons((*cp << 8) | cp[1]); | |
428 | cp += 2; | |
429 | if (changes & TCP_PUSH_BIT) | |
430 | th->th_flags |= TH_PUSH; | |
431 | else | |
432 | th->th_flags &=~ TH_PUSH; | |
433 | ||
434 | switch (changes & SPECIALS_MASK) { | |
435 | case SPECIAL_I: | |
436 | { | |
437 | register u_int i = ntohs(cs->cs_ip.ip_len) - cs->cs_hlen; | |
438 | th->th_ack = htonl(ntohl(th->th_ack) + i); | |
439 | th->th_seq = htonl(ntohl(th->th_seq) + i); | |
440 | } | |
441 | break; | |
442 | ||
443 | case SPECIAL_D: | |
444 | th->th_seq = htonl(ntohl(th->th_seq) + ntohs(cs->cs_ip.ip_len) | |
445 | - cs->cs_hlen); | |
446 | break; | |
447 | ||
448 | default: | |
449 | if (changes & NEW_U) { | |
450 | th->th_flags |= TH_URG; | |
b06f22bd | 451 | DECODEU(th->th_urp) |
11b5360c SL |
452 | } else |
453 | th->th_flags &=~ TH_URG; | |
454 | if (changes & NEW_W) | |
455 | DECODES(th->th_win) | |
456 | if (changes & NEW_A) | |
457 | DECODEL(th->th_ack) | |
458 | if (changes & NEW_S) | |
459 | DECODEL(th->th_seq) | |
460 | break; | |
461 | } | |
462 | if (changes & NEW_I) { | |
463 | DECODES(cs->cs_ip.ip_id) | |
464 | } else | |
465 | cs->cs_ip.ip_id = htons(ntohs(cs->cs_ip.ip_id) + 1); | |
466 | ||
467 | /* | |
468 | * At this point, cp points to the first byte of data in the | |
1dbf8d66 MK |
469 | * packet. If we're not aligned on a 4-byte boundary, copy the |
470 | * data down so the ip & tcp headers will be aligned. Then back up | |
471 | * cp by the tcp/ip header length to make room for the reconstructed | |
472 | * header (we assume the packet we were handed has enough space to | |
b06f22bd | 473 | * prepend 128 bytes of header). Adjust the length to account for |
1dbf8d66 | 474 | * the new header & fill in the IP total length. |
11b5360c | 475 | */ |
1dbf8d66 | 476 | len -= (cp - *bufp); |
b06f22bd | 477 | if (len < 0) |
1dbf8d66 MK |
478 | /* we must have dropped some characters (crc should detect |
479 | * this but the old slip framing won't) */ | |
b06f22bd SL |
480 | goto bad; |
481 | ||
26fea0bf SL |
482 | if ((int)cp & 3) { |
483 | if (len > 0) | |
b06f22bd | 484 | (void) ovbcopy(cp, (caddr_t)((int)cp &~ 3), len); |
1dbf8d66 MK |
485 | cp = (u_char *)((int)cp &~ 3); |
486 | } | |
487 | cp -= cs->cs_hlen; | |
488 | len += cs->cs_hlen; | |
489 | cs->cs_ip.ip_len = htons(len); | |
490 | BCOPY(&cs->cs_ip, cp, cs->cs_hlen); | |
491 | *bufp = cp; | |
492 | ||
493 | /* recompute the ip header checksum */ | |
494 | { | |
495 | register u_short *bp = (u_short *)cp; | |
496 | for (changes = 0; hlen > 0; hlen -= 2) | |
497 | changes += *bp++; | |
498 | changes = (changes & 0xffff) + (changes >> 16); | |
499 | changes = (changes & 0xffff) + (changes >> 16); | |
500 | ((struct ip *)cp)->ip_sum = ~ changes; | |
501 | } | |
502 | return (len); | |
b06f22bd SL |
503 | bad: |
504 | comp->flags |= SLF_TOSS; | |
505 | INCR(sls_errorin) | |
506 | return (0); | |
11b5360c | 507 | } |