Commit | Line | Data |
---|---|---|
11b5360c | 1 | /* |
26fea0bf | 2 | * @(#)slcompress.c 7.4 (Berkeley) %G% |
1dbf8d66 | 3 | * |
11b5360c SL |
4 | * THIS CODE IS NOT FOR DISTRIBUTION! |
5 | * KEEP YOUR GRUBBY HANDS OFF UNLESS AUTHORIZED BY VAN JACOBSON TO COPY! | |
6 | * ASK SAM, MIKE, OR BILL ABOUT IT. | |
1dbf8d66 | 7 | * |
11b5360c SL |
8 | * Routines to compress and uncompess tcp packets (for transmission |
9 | * over low speed serial lines. | |
10 | * | |
11 | * Copyright (c) 1988, 1989 by Van Jacobson, Lawrence Berkeley Laboratory | |
12 | * All rights reserved. | |
13 | */ | |
14 | ||
1dbf8d66 MK |
15 | #include "sl.h" |
16 | #if NSL > 0 | |
11b5360c | 17 | #ifndef lint |
1dbf8d66 | 18 | static char rcsid[] = "$Header: slcompress.c,v 1.10 89/06/05 08:28:52 van Exp $"; |
11b5360c SL |
19 | #endif |
20 | ||
21 | #include <sys/types.h> | |
22 | #include <sys/param.h> | |
23 | #include <sys/mbuf.h> | |
24 | #include <netinet/in.h> | |
25 | #include <netinet/in_systm.h> | |
26 | #include <netinet/ip.h> | |
27 | #include <netinet/tcp.h> | |
28 | ||
29 | #include "slcompress.h" | |
30 | ||
1dbf8d66 MK |
31 | #ifndef NO_SL_STATS |
32 | #define INCR(counter) ++comp->counter; | |
33 | #else | |
34 | #define INCR(counter) | |
35 | #endif | |
11b5360c SL |
36 | |
37 | #define BCMP(p1, p2, n) bcmp((char *)(p1), (char *)(p2), (int)(n)) | |
38 | #define BCOPY(p1, p2, n) bcopy((char *)(p1), (char *)(p2), (int)(n)) | |
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 | ||
104 | ||
105 | u_char | |
106 | sl_compress_tcp(m, ip, comp) | |
107 | struct mbuf *m; | |
108 | register struct ip *ip; | |
109 | struct slcompress *comp; | |
110 | { | |
111 | register struct cstate *cs = comp->last_cs->cs_next; | |
112 | register u_int hlen = ip->ip_hl; | |
113 | register struct tcphdr *oth; | |
114 | register struct tcphdr *th; | |
115 | register u_int deltaS, deltaA; | |
116 | register u_int changes = 0; | |
117 | u_char new_seq[16]; | |
118 | register u_char *cp = new_seq; | |
119 | ||
120 | /* | |
121 | * Bail if this is an ip fragment or if we don't have | |
122 | * a complete ip & tcp header in the first mbuf. Otherwise, | |
123 | * check flags to see if this is a packet we might compress | |
124 | * and, if so, try to locate the connection state. | |
11b5360c SL |
125 | * special case the most recently used connection since |
126 | * it's most likely to be used again & we don't have to | |
127 | * do any reordering if it's used. | |
128 | */ | |
129 | if ((ip->ip_off & 0x3fff) || m->m_len < 40) | |
130 | return (TYPE_IP); | |
131 | ||
132 | th = (struct tcphdr *)&((int *)ip)[hlen]; | |
133 | if ((th->th_flags & (TH_SYN|TH_FIN|TH_RST|TH_ACK)) != TH_ACK) | |
134 | return (TYPE_IP); | |
135 | ||
1dbf8d66 MK |
136 | INCR(sls_packets) |
137 | if (ip->ip_src.s_addr != cs->cs_ip.ip_src.s_addr || | |
138 | ip->ip_dst.s_addr != cs->cs_ip.ip_dst.s_addr || | |
139 | *(int *)th != ((int *)&cs->cs_ip)[cs->cs_ip.ip_hl]) { | |
11b5360c SL |
140 | /* |
141 | * Wasn't the first -- search for it. | |
142 | * | |
143 | * States are kept in a circularly linked list with | |
144 | * first_cs pointing to the head of the list. The | |
145 | * list is kept in lru order by moving a state to the | |
146 | * head of the list whenever it is referenced. Since | |
147 | * the list is short and, empirically, the connection | |
148 | * we want is almost always near the front, we locate | |
149 | * states via linear search. If we don't find a state | |
150 | * for the datagram, the oldest state is used. | |
151 | */ | |
152 | register struct cstate *lcs; | |
153 | ||
154 | do { | |
155 | lcs = cs; cs = cs->cs_next; | |
1dbf8d66 | 156 | INCR(sls_searches) |
11b5360c SL |
157 | if (*(int *)th == ((int *)&cs->cs_ip)[cs->cs_ip.ip_hl] |
158 | && ip->ip_src.s_addr == cs->cs_ip.ip_src.s_addr | |
159 | && ip->ip_dst.s_addr == cs->cs_ip.ip_dst.s_addr) | |
160 | goto found; | |
161 | } while (cs != comp->last_cs); | |
1dbf8d66 | 162 | INCR(sls_misses) |
11b5360c SL |
163 | |
164 | /* | |
165 | * Didn't find it -- re-use oldest cstate. | |
166 | * Send an uncompressed packet that tells | |
167 | * the other side what connection number | |
168 | * we're using for this conversation. Note | |
169 | * that since the state list is circular, the | |
170 | * oldest state points to the newest and we only | |
171 | * need to set last_cs to update the lru linkage. | |
172 | */ | |
173 | comp->last_cs = lcs; | |
174 | hlen += th->th_off; | |
175 | hlen <<= 2; | |
176 | goto uncompressed; | |
177 | ||
178 | found: | |
179 | /* | |
180 | * Found it -- move to the front on the connection list. | |
181 | */ | |
182 | if (comp->last_cs == cs) | |
183 | comp->last_cs = lcs; | |
184 | else { | |
185 | lcs->cs_next = cs->cs_next; | |
186 | cs->cs_next = comp->last_cs->cs_next; | |
187 | comp->last_cs->cs_next = cs; | |
188 | } | |
189 | } | |
190 | ||
191 | /* | |
192 | * Make sure that only what we expect to change changed. | |
193 | */ | |
194 | oth = (struct tcphdr *)&((int *)&cs->cs_ip)[hlen]; | |
195 | deltaS = hlen; | |
196 | hlen += th->th_off; | |
197 | hlen <<= 2; | |
198 | ||
199 | if (((u_short *)ip)[0] != ((u_short *)&cs->cs_ip)[0] || | |
200 | ((u_short *)ip)[4] != ((u_short *)&cs->cs_ip)[4] || | |
201 | th->th_off != oth->th_off || | |
202 | (deltaS > 5 && | |
203 | BCMP(ip + 1, &cs->cs_ip + 1, (deltaS - 5) << 2)) || | |
204 | (th->th_off > 5 && | |
205 | BCMP(th + 1, oth + 1, (th->th_off - 5) << 2))) | |
206 | goto uncompressed; | |
207 | ||
208 | /* | |
209 | * Figure out which of the changing fields changed. The | |
210 | * receiver expects changes in the order: urgent, window, | |
211 | * ack, seq (the order minimizes the number of temporaries | |
212 | * needed in this section of code). | |
213 | */ | |
214 | if (th->th_flags & TH_URG) { | |
215 | deltaS = ntohs(th->th_urp); | |
216 | ENCODEZ(deltaS); | |
217 | changes |= NEW_U; | |
218 | } else if (th->th_urp != oth->th_urp) | |
219 | /* argh! URG not set but urp changed -- a sensible | |
220 | * implementation should never do this but RFC793 | |
221 | * doesn't prohibit the change so we have to deal | |
222 | * with it. */ | |
223 | goto uncompressed; | |
224 | ||
225 | if (deltaS = (u_short)(ntohs(th->th_win) - ntohs(oth->th_win))) { | |
226 | ENCODE(deltaS); | |
227 | changes |= NEW_W; | |
228 | } | |
229 | ||
230 | if (deltaA = ntohl(th->th_ack) - ntohl(oth->th_ack)) { | |
231 | if (deltaA > 0xffff) | |
232 | goto uncompressed; | |
233 | ENCODE(deltaA); | |
234 | changes |= NEW_A; | |
235 | } | |
236 | ||
237 | if (deltaS = ntohl(th->th_seq) - ntohl(oth->th_seq)) { | |
238 | if (deltaS > 0xffff) | |
239 | goto uncompressed; | |
240 | ENCODE(deltaS); | |
241 | changes |= NEW_S; | |
242 | } | |
243 | ||
244 | switch(changes) { | |
245 | ||
246 | case 0: | |
247 | if (ip->ip_len != cs->cs_ip.ip_len && ntohs(ip->ip_len) != hlen) | |
248 | break; | |
249 | /* | |
250 | * Nothing changed and this packet looks like a duplicate | |
251 | * of the last or contains no data -- this is probably a | |
252 | * retransmitted ack or window probe. Send it | |
253 | * uncompressed in case the other side missed the | |
254 | * compressed version. | |
255 | * | |
256 | * (fall through) | |
257 | */ | |
258 | ||
259 | case SPECIAL_I: | |
260 | case SPECIAL_D: | |
261 | /* | |
262 | * actual changes match one of our special case encodings -- | |
263 | * send packet uncompressed. | |
264 | */ | |
265 | goto uncompressed; | |
266 | ||
267 | case NEW_S|NEW_A: | |
268 | if (deltaS == deltaA && | |
269 | deltaS == ntohs(cs->cs_ip.ip_len) - hlen) { | |
270 | /* special case for echoed terminal traffic */ | |
271 | changes = SPECIAL_I; | |
272 | cp = new_seq; | |
273 | } | |
274 | break; | |
275 | ||
276 | case NEW_S: | |
277 | if (deltaS == ntohs(cs->cs_ip.ip_len) - hlen) { | |
278 | /* special case for data xfer */ | |
279 | changes = SPECIAL_D; | |
280 | cp = new_seq; | |
281 | } | |
282 | break; | |
283 | } | |
284 | ||
285 | deltaS = ntohs(ip->ip_id) - ntohs(cs->cs_ip.ip_id); | |
286 | if (deltaS != 1) { | |
287 | ENCODEZ(deltaS); | |
288 | changes |= NEW_I; | |
289 | } | |
290 | if (th->th_flags & TH_PUSH) | |
291 | changes |= TCP_PUSH_BIT; | |
292 | /* | |
293 | * Grab the cksum before we overwrite it below. Then update our | |
294 | * state with this packet's header. | |
295 | */ | |
296 | deltaA = ntohs(th->th_sum); | |
297 | BCOPY(ip, &cs->cs_ip, hlen); | |
298 | ||
299 | /* | |
300 | * We want to use the original packet as our compressed packet. | |
301 | * (cp - new_seq) is the number of bytes we need for compressed | |
302 | * sequence numbers. In addition we need one byte for the change | |
303 | * mask, one for the connection id and two for the tcp checksum. | |
304 | * So, (cp - new_seq) + 4 bytes of header are needed. hlen is how | |
305 | * many bytes of the original packet to toss so subtract the two to | |
306 | * get the new packet size. | |
307 | */ | |
308 | deltaS = cp - new_seq; | |
309 | cp = (u_char *)ip; | |
310 | if (comp->last_xmit != cs->cs_id) { | |
311 | comp->last_xmit = cs->cs_id; | |
312 | hlen -= deltaS + 4; | |
1dbf8d66 MK |
313 | cp += hlen; |
314 | m->m_len -= hlen; | |
315 | m->m_data += hlen; | |
316 | *cp++ = changes | NEW_C; | |
11b5360c SL |
317 | *cp++ = cs->cs_id; |
318 | } else { | |
319 | hlen -= deltaS + 3; | |
1dbf8d66 MK |
320 | cp += hlen; |
321 | m->m_len -= hlen; | |
322 | m->m_data += hlen; | |
323 | *cp++ = changes; | |
11b5360c SL |
324 | } |
325 | *cp++ = deltaA >> 8; | |
326 | *cp++ = deltaA; | |
327 | BCOPY(new_seq, cp, deltaS); | |
1dbf8d66 | 328 | INCR(sls_compressed) |
11b5360c SL |
329 | return (TYPE_COMPRESSED_TCP); |
330 | ||
331 | /* | |
332 | * Update connection state cs & send uncompressed packet ('uncompressed' | |
333 | * means a regular ip/tcp packet but with the 'conversation id' we hope | |
334 | * to use on future compressed packets in the protocol field). | |
335 | */ | |
336 | uncompressed: | |
337 | BCOPY(ip, &cs->cs_ip, hlen); | |
338 | ip->ip_p = cs->cs_id; | |
339 | comp->last_xmit = cs->cs_id; | |
11b5360c SL |
340 | return (TYPE_UNCOMPRESSED_TCP); |
341 | } | |
342 | ||
11b5360c | 343 | |
1dbf8d66 MK |
344 | int |
345 | sl_uncompress_tcp(bufp, len, type, comp) | |
346 | u_char **bufp; | |
347 | int len; | |
348 | u_int type; | |
11b5360c SL |
349 | struct slcompress *comp; |
350 | { | |
351 | register u_char *cp; | |
352 | register u_int hlen, changes; | |
353 | register struct tcphdr *th; | |
354 | register struct cstate *cs; | |
355 | register struct ip *ip; | |
11b5360c SL |
356 | |
357 | switch (type) { | |
358 | ||
359 | case TYPE_UNCOMPRESSED_TCP: | |
1dbf8d66 MK |
360 | ip = (struct ip *) *bufp; |
361 | if (ip->ip_p >= MAX_STATES) { | |
362 | INCR(sls_errorin) | |
363 | return (0); | |
364 | } | |
11b5360c SL |
365 | cs = &comp->rstate[comp->last_recv = ip->ip_p]; |
366 | comp->flags &=~ SLF_TOSS; | |
367 | ip->ip_p = IPPROTO_TCP; | |
368 | hlen = ip->ip_hl; | |
369 | hlen += ((struct tcphdr *)&((int *)ip)[hlen])->th_off; | |
370 | hlen <<= 2; | |
371 | BCOPY(ip, &cs->cs_ip, hlen); | |
372 | cs->cs_ip.ip_sum = 0; | |
373 | cs->cs_hlen = hlen; | |
1dbf8d66 MK |
374 | INCR(sls_uncompressedin) |
375 | return (len); | |
11b5360c SL |
376 | |
377 | case TYPE_ERROR: | |
378 | comp->flags |= SLF_TOSS; | |
1dbf8d66 MK |
379 | default: |
380 | INCR(sls_errorin) | |
381 | return (0); | |
11b5360c SL |
382 | |
383 | case TYPE_COMPRESSED_TCP: | |
11b5360c SL |
384 | break; |
385 | } | |
386 | /* We've got a compressed packet. */ | |
1dbf8d66 MK |
387 | INCR(sls_compressedin) |
388 | cp = *bufp; | |
11b5360c SL |
389 | changes = *cp++; |
390 | if (changes & NEW_C) { | |
391 | /* Make sure the state index is in range, then grab the state. | |
392 | * If we have a good state index, clear the 'discard' flag. */ | |
1dbf8d66 MK |
393 | if (*cp >= MAX_STATES) { |
394 | INCR(sls_errorin) | |
395 | return (0); | |
396 | } | |
11b5360c SL |
397 | comp->flags &=~ SLF_TOSS; |
398 | comp->last_recv = *cp++; | |
399 | } else { | |
400 | /* this packet has an implicit state index. If we've | |
401 | * had a line error since the last time we got an | |
402 | * explicit state index, we have to toss the packet. */ | |
1dbf8d66 MK |
403 | if (comp->flags & SLF_TOSS) { |
404 | INCR(sls_tossed) | |
405 | return (0); | |
406 | } | |
11b5360c SL |
407 | } |
408 | cs = &comp->rstate[comp->last_recv]; | |
409 | hlen = cs->cs_ip.ip_hl << 2; | |
410 | th = (struct tcphdr *)&((u_char *)&cs->cs_ip)[hlen]; | |
411 | th->th_sum = htons((*cp << 8) | cp[1]); | |
412 | cp += 2; | |
413 | if (changes & TCP_PUSH_BIT) | |
414 | th->th_flags |= TH_PUSH; | |
415 | else | |
416 | th->th_flags &=~ TH_PUSH; | |
417 | ||
418 | switch (changes & SPECIALS_MASK) { | |
419 | case SPECIAL_I: | |
420 | { | |
421 | register u_int i = ntohs(cs->cs_ip.ip_len) - cs->cs_hlen; | |
422 | th->th_ack = htonl(ntohl(th->th_ack) + i); | |
423 | th->th_seq = htonl(ntohl(th->th_seq) + i); | |
424 | } | |
425 | break; | |
426 | ||
427 | case SPECIAL_D: | |
428 | th->th_seq = htonl(ntohl(th->th_seq) + ntohs(cs->cs_ip.ip_len) | |
429 | - cs->cs_hlen); | |
430 | break; | |
431 | ||
432 | default: | |
433 | if (changes & NEW_U) { | |
434 | th->th_flags |= TH_URG; | |
435 | DECODES(th->th_urp) | |
436 | } else | |
437 | th->th_flags &=~ TH_URG; | |
438 | if (changes & NEW_W) | |
439 | DECODES(th->th_win) | |
440 | if (changes & NEW_A) | |
441 | DECODEL(th->th_ack) | |
442 | if (changes & NEW_S) | |
443 | DECODEL(th->th_seq) | |
444 | break; | |
445 | } | |
446 | if (changes & NEW_I) { | |
447 | DECODES(cs->cs_ip.ip_id) | |
448 | } else | |
449 | cs->cs_ip.ip_id = htons(ntohs(cs->cs_ip.ip_id) + 1); | |
450 | ||
451 | /* | |
452 | * At this point, cp points to the first byte of data in the | |
1dbf8d66 MK |
453 | * packet. If we're not aligned on a 4-byte boundary, copy the |
454 | * data down so the ip & tcp headers will be aligned. Then back up | |
455 | * cp by the tcp/ip header length to make room for the reconstructed | |
456 | * header (we assume the packet we were handed has enough space to | |
457 | * prepend 128 bytes of header). Adjust the lenth to account for | |
458 | * the new header & fill in the IP total length. | |
11b5360c | 459 | */ |
1dbf8d66 MK |
460 | len -= (cp - *bufp); |
461 | if (len < 0) { | |
462 | /* we must have dropped some characters (crc should detect | |
463 | * this but the old slip framing won't) */ | |
464 | INCR(sls_errorin) | |
465 | return (0); | |
466 | } | |
26fea0bf SL |
467 | if ((int)cp & 3) { |
468 | if (len > 0) | |
469 | BCOPY(cp, (int)cp &~ 3, len); | |
1dbf8d66 MK |
470 | cp = (u_char *)((int)cp &~ 3); |
471 | } | |
472 | cp -= cs->cs_hlen; | |
473 | len += cs->cs_hlen; | |
474 | cs->cs_ip.ip_len = htons(len); | |
475 | BCOPY(&cs->cs_ip, cp, cs->cs_hlen); | |
476 | *bufp = cp; | |
477 | ||
478 | /* recompute the ip header checksum */ | |
479 | { | |
480 | register u_short *bp = (u_short *)cp; | |
481 | for (changes = 0; hlen > 0; hlen -= 2) | |
482 | changes += *bp++; | |
483 | changes = (changes & 0xffff) + (changes >> 16); | |
484 | changes = (changes & 0xffff) + (changes >> 16); | |
485 | ((struct ip *)cp)->ip_sum = ~ changes; | |
486 | } | |
487 | return (len); | |
11b5360c | 488 | } |
1dbf8d66 | 489 | #endif |