1 | /* $NetBSD: slcompress.c,v 1.40 2016/08/05 08:56:36 pgoyette Exp $ */ |
2 | /* Id: slcompress.c,v 1.3 1996/05/24 07:04:47 paulus Exp */ |
3 | |
4 | /* |
5 | * Copyright (c) 1989, 1993, 1994 |
6 | * The Regents of the University of California. All rights reserved. |
7 | * |
8 | * Redistribution and use in source and binary forms, with or without |
9 | * modification, are permitted provided that the following conditions |
10 | * are met: |
11 | * 1. Redistributions of source code must retain the above copyright |
12 | * notice, this list of conditions and the following disclaimer. |
13 | * 2. Redistributions in binary form must reproduce the above copyright |
14 | * notice, this list of conditions and the following disclaimer in the |
15 | * documentation and/or other materials provided with the distribution. |
16 | * 3. Neither the name of the University nor the names of its contributors |
17 | * may be used to endorse or promote products derived from this software |
18 | * without specific prior written permission. |
19 | * |
20 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
21 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
22 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
23 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
24 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
25 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
26 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
27 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
28 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
29 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
30 | * SUCH DAMAGE. |
31 | * |
32 | * @(#)slcompress.c 8.2 (Berkeley) 4/16/94 |
33 | */ |
34 | |
35 | /* |
36 | * Routines to compress and uncompess tcp packets (for transmission |
37 | * over low speed serial lines. |
38 | * |
39 | * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989: |
40 | * - Initial distribution. |
41 | */ |
42 | |
43 | #include <sys/cdefs.h> |
44 | __KERNEL_RCSID(0, "$NetBSD: slcompress.c,v 1.40 2016/08/05 08:56:36 pgoyette Exp $" ); |
45 | |
46 | #ifdef _KERNEL_OPT |
47 | #include "opt_inet.h" |
48 | #endif |
49 | |
50 | #ifdef INET |
51 | #include <sys/param.h> |
52 | #include <sys/mbuf.h> |
53 | #include <sys/systm.h> |
54 | #include <sys/module.h> |
55 | |
56 | #include <netinet/in.h> |
57 | #include <netinet/in_systm.h> |
58 | #include <netinet/ip.h> |
59 | #include <netinet/tcp.h> |
60 | |
61 | #include <net/slcompress.h> |
62 | |
63 | #ifndef SL_NO_STATS |
64 | #define INCR(counter) ++comp->counter; |
65 | #else |
66 | #define INCR(counter) |
67 | #endif |
68 | |
69 | |
70 | void |
71 | sl_compress_init(struct slcompress *comp) |
72 | { |
73 | u_int i; |
74 | struct cstate *tstate = comp->tstate; |
75 | |
76 | memset(comp, 0, sizeof(*comp)); |
77 | for (i = MAX_STATES - 1; i > 0; --i) { |
78 | tstate[i].cs_id = i; |
79 | tstate[i].cs_next = &tstate[i - 1]; |
80 | } |
81 | tstate[0].cs_next = &tstate[MAX_STATES - 1]; |
82 | tstate[0].cs_id = 0; |
83 | comp->last_cs = &tstate[0]; |
84 | comp->last_recv = 255; |
85 | comp->last_xmit = 255; |
86 | comp->flags = SLF_TOSS; |
87 | } |
88 | |
89 | |
90 | /* |
91 | * Like sl_compress_init, but we get to specify the maximum connection |
92 | * ID to use on transmission. |
93 | */ |
94 | void |
95 | sl_compress_setup(struct slcompress *comp, int max_state) |
96 | { |
97 | u_int i; |
98 | struct cstate *tstate = comp->tstate; |
99 | |
100 | if (max_state == -1) { |
101 | max_state = MAX_STATES - 1; |
102 | memset(comp, 0, sizeof(*comp)); |
103 | } else { |
104 | /* Don't reset statistics */ |
105 | memset(comp->tstate, 0, sizeof(comp->tstate)); |
106 | memset(comp->rstate, 0, sizeof(comp->rstate)); |
107 | } |
108 | for (i = max_state; i > 0; --i) { |
109 | tstate[i].cs_id = i; |
110 | tstate[i].cs_next = &tstate[i - 1]; |
111 | } |
112 | tstate[0].cs_next = &tstate[max_state]; |
113 | tstate[0].cs_id = 0; |
114 | comp->last_cs = &tstate[0]; |
115 | comp->last_recv = 255; |
116 | comp->last_xmit = 255; |
117 | comp->flags = SLF_TOSS; |
118 | } |
119 | |
120 | |
121 | /* ENCODE encodes a number that is known to be non-zero. ENCODEZ |
122 | * checks for zero (since zero has to be encoded in the long, 3 byte |
123 | * form). |
124 | */ |
125 | #define ENCODE(n) { \ |
126 | if ((uint16_t)(n) >= 256) { \ |
127 | *cp++ = 0; \ |
128 | cp[1] = (n); \ |
129 | cp[0] = (n) >> 8; \ |
130 | cp += 2; \ |
131 | } else { \ |
132 | *cp++ = (n); \ |
133 | } \ |
134 | } |
135 | #define ENCODEZ(n) { \ |
136 | if ((uint16_t)(n) >= 256 || (uint16_t)(n) == 0) { \ |
137 | *cp++ = 0; \ |
138 | cp[1] = (n); \ |
139 | cp[0] = (n) >> 8; \ |
140 | cp += 2; \ |
141 | } else { \ |
142 | *cp++ = (n); \ |
143 | } \ |
144 | } |
145 | |
146 | #define DECODEL(f) { \ |
147 | if (*cp == 0) {\ |
148 | (f) = htonl(ntohl(f) + ((cp[1] << 8) | cp[2])); \ |
149 | cp += 3; \ |
150 | } else { \ |
151 | (f) = htonl(ntohl(f) + (uint32_t)*cp++); \ |
152 | } \ |
153 | } |
154 | |
155 | #define DECODES(f) { \ |
156 | if (*cp == 0) {\ |
157 | (f) = htons(ntohs(f) + ((cp[1] << 8) | cp[2])); \ |
158 | cp += 3; \ |
159 | } else { \ |
160 | (f) = htons(ntohs(f) + (uint32_t)*cp++); \ |
161 | } \ |
162 | } |
163 | |
164 | #define DECODEU(f) { \ |
165 | if (*cp == 0) {\ |
166 | (f) = htons((cp[1] << 8) | cp[2]); \ |
167 | cp += 3; \ |
168 | } else { \ |
169 | (f) = htons((uint32_t)*cp++); \ |
170 | } \ |
171 | } |
172 | |
173 | u_int |
174 | sl_compress_tcp(struct mbuf *m, struct ip *ip, struct slcompress *comp, |
175 | int compress_cid) |
176 | { |
177 | struct cstate *cs = comp->last_cs->cs_next; |
178 | u_int hlen = ip->ip_hl; |
179 | struct tcphdr *oth; |
180 | struct tcphdr *th; |
181 | u_int deltaS, deltaA; |
182 | u_int changes = 0; |
183 | u_char new_seq[16]; |
184 | 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 | struct cstate *lcs; |
222 | 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 (((uint16_t *)ip)[0] != ((uint16_t *)&cs->cs_ip)[0] || |
282 | ((uint16_t *)ip)[3] != ((uint16_t *)&cs->cs_ip)[3] || |
283 | ((uint16_t *)ip)[4] != ((uint16_t *)&cs->cs_ip)[4] || |
284 | th->th_off != oth->th_off || |
285 | (deltaS > 5 && |
286 | memcmp(ip + 1, &cs->cs_ip + 1, (deltaS - 5) << 2)) || |
287 | (th->th_off > 5 && |
288 | memcmp(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 = (uint16_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 | memcpy(&cs->cs_ip, 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 | memcpy(cp, new_seq, 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 | memcpy(&cs->cs_ip, 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(u_char **bufp, int len, u_int type, struct slcompress *comp) |
432 | { |
433 | u_char *hdr, *cp; |
434 | int vjlen; |
435 | u_int hlen; |
436 | |
437 | cp = bufp ? *bufp : NULL; |
438 | vjlen = sl_uncompress_tcp_core(cp, len, len, type, comp, &hdr, &hlen); |
439 | if (vjlen < 0) |
440 | return (0); /* error */ |
441 | if (vjlen == 0) |
442 | return (len); /* was uncompressed already */ |
443 | |
444 | cp += vjlen; |
445 | len -= vjlen; |
446 | |
447 | /* |
448 | * At this point, cp points to the first byte of data in the |
449 | * packet. If we're not aligned on a 4-byte boundary, copy the |
450 | * data down so the ip & tcp headers will be aligned. Then back up |
451 | * cp by the tcp/ip header length to make room for the reconstructed |
452 | * header (we assume the packet we were handed has enough space to |
453 | * prepend 128 bytes of header). |
454 | */ |
455 | if ((long)cp & 3) { |
456 | if (len > 0) |
457 | memmove((void *)((long)cp &~ 3), cp, len); |
458 | cp = (u_char *)((long)cp &~ 3); |
459 | } |
460 | cp -= hlen; |
461 | len += hlen; |
462 | memcpy(cp, hdr, hlen); |
463 | |
464 | *bufp = cp; |
465 | return (len); |
466 | } |
467 | |
468 | /* |
469 | * Uncompress a packet of total length total_len. The first buflen |
470 | * bytes are at buf; this must include the entire (compressed or |
471 | * uncompressed) TCP/IP header. This procedure returns the length |
472 | * of the VJ header, with a pointer to the uncompressed IP header |
473 | * in *hdrp and its length in *hlenp. |
474 | */ |
475 | int |
476 | sl_uncompress_tcp_core(u_char *buf, int buflen, int total_len, u_int type, |
477 | struct slcompress *comp, u_char **hdrp, u_int *hlenp) |
478 | { |
479 | u_char *cp; |
480 | u_int hlen, changes; |
481 | struct tcphdr *th; |
482 | struct cstate *cs; |
483 | struct ip *ip; |
484 | uint16_t *bp; |
485 | u_int vjlen; |
486 | |
487 | switch (type) { |
488 | |
489 | case TYPE_UNCOMPRESSED_TCP: |
490 | if (buf == NULL) |
491 | goto bad; |
492 | ip = (struct ip *) buf; |
493 | if (ip->ip_p >= MAX_STATES) |
494 | goto bad; |
495 | cs = &comp->rstate[comp->last_recv = ip->ip_p]; |
496 | comp->flags &=~ SLF_TOSS; |
497 | ip->ip_p = IPPROTO_TCP; |
498 | /* |
499 | * Calculate the size of the TCP/IP header and make sure that |
500 | * we don't overflow the space we have available for it. |
501 | */ |
502 | hlen = ip->ip_hl << 2; |
503 | if (hlen + sizeof(struct tcphdr) > buflen) |
504 | goto bad; |
505 | hlen += ((struct tcphdr *)&((char *)ip)[hlen])->th_off << 2; |
506 | if (hlen > MAX_HDR || hlen > buflen) |
507 | goto bad; |
508 | memcpy(&cs->cs_ip, ip, hlen); |
509 | cs->cs_hlen = hlen; |
510 | INCR(sls_uncompressedin) |
511 | *hdrp = (u_char *) &cs->cs_ip; |
512 | *hlenp = hlen; |
513 | return (0); |
514 | |
515 | default: |
516 | goto bad; |
517 | |
518 | case TYPE_COMPRESSED_TCP: |
519 | break; |
520 | } |
521 | /* We've got a compressed packet. */ |
522 | INCR(sls_compressedin) |
523 | if (buf == NULL) |
524 | goto bad; |
525 | cp = buf; |
526 | changes = *cp++; |
527 | if (changes & NEW_C) { |
528 | /* Make sure the state index is in range, then grab the state. |
529 | * If we have a good state index, clear the 'discard' flag. */ |
530 | if (*cp >= MAX_STATES) |
531 | goto bad; |
532 | |
533 | comp->flags &=~ SLF_TOSS; |
534 | comp->last_recv = *cp++; |
535 | } else { |
536 | /* this packet has an implicit state index. If we've |
537 | * had a line error since the last time we got an |
538 | * explicit state index, we have to toss the packet. */ |
539 | if (comp->flags & SLF_TOSS) { |
540 | INCR(sls_tossed) |
541 | return (-1); |
542 | } |
543 | } |
544 | cs = &comp->rstate[comp->last_recv]; |
545 | hlen = cs->cs_ip.ip_hl << 2; |
546 | th = (struct tcphdr *)&((u_char *)&cs->cs_ip)[hlen]; |
547 | th->th_sum = htons((*cp << 8) | cp[1]); |
548 | cp += 2; |
549 | if (changes & TCP_PUSH_BIT) |
550 | th->th_flags |= TH_PUSH; |
551 | else |
552 | th->th_flags &=~ TH_PUSH; |
553 | |
554 | switch (changes & SPECIALS_MASK) { |
555 | case SPECIAL_I: |
556 | { |
557 | u_int i = ntohs(cs->cs_ip.ip_len) - cs->cs_hlen; |
558 | th->th_ack = htonl(ntohl(th->th_ack) + i); |
559 | th->th_seq = htonl(ntohl(th->th_seq) + i); |
560 | } |
561 | break; |
562 | |
563 | case SPECIAL_D: |
564 | th->th_seq = htonl(ntohl(th->th_seq) + ntohs(cs->cs_ip.ip_len) |
565 | - cs->cs_hlen); |
566 | break; |
567 | |
568 | default: |
569 | if (changes & NEW_U) { |
570 | th->th_flags |= TH_URG; |
571 | DECODEU(th->th_urp) |
572 | } else |
573 | th->th_flags &=~ TH_URG; |
574 | if (changes & NEW_W) |
575 | DECODES(th->th_win) |
576 | if (changes & NEW_A) |
577 | DECODEL(th->th_ack) |
578 | if (changes & NEW_S) |
579 | DECODEL(th->th_seq) |
580 | break; |
581 | } |
582 | if (changes & NEW_I) { |
583 | DECODES(cs->cs_ip.ip_id) |
584 | } else |
585 | cs->cs_ip.ip_id = htons(ntohs(cs->cs_ip.ip_id) + 1); |
586 | |
587 | /* |
588 | * At this point, cp points to the first byte of data in the |
589 | * packet. Fill in the IP total length and update the IP |
590 | * header checksum. |
591 | */ |
592 | vjlen = cp - buf; |
593 | buflen -= vjlen; |
594 | if (buflen < 0) |
595 | /* we must have dropped some characters (crc should detect |
596 | * this but the old slip framing won't) */ |
597 | goto bad; |
598 | |
599 | total_len += cs->cs_hlen - vjlen; |
600 | cs->cs_ip.ip_len = htons(total_len); |
601 | |
602 | /* recompute the ip header checksum */ |
603 | bp = (uint16_t *) &cs->cs_ip; |
604 | cs->cs_ip.ip_sum = 0; |
605 | for (changes = 0; hlen > 0; hlen -= 2) |
606 | changes += *bp++; |
607 | changes = (changes & 0xffff) + (changes >> 16); |
608 | changes = (changes & 0xffff) + (changes >> 16); |
609 | cs->cs_ip.ip_sum = ~ changes; |
610 | |
611 | *hdrp = (u_char *) &cs->cs_ip; |
612 | *hlenp = cs->cs_hlen; |
613 | return vjlen; |
614 | |
615 | bad: |
616 | comp->flags |= SLF_TOSS; |
617 | INCR(sls_errorin) |
618 | return (-1); |
619 | } |
620 | #endif |
621 | |
622 | MODULE(MODULE_CLASS_MISC, slcompress, NULL); |
623 | |
624 | static int |
625 | slcompress_modcmd(modcmd_t cmd, void *arg) |
626 | { |
627 | switch (cmd) { |
628 | case MODULE_CMD_INIT: |
629 | case MODULE_CMD_FINI: |
630 | #ifdef INET |
631 | return 0; |
632 | #endif |
633 | case MODULE_CMD_STAT: |
634 | case MODULE_CMD_AUTOUNLOAD: |
635 | default: |
636 | return ENOTTY; |
637 | } |
638 | } |
639 | |