Loading...
1/*
2 * Routines to compress and uncompress tcp packets (for transmission
3 * over low speed serial lines).
4 *
5 * Copyright (c) 1989 Regents of the University of California.
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms are permitted
9 * provided that the above copyright notice and this paragraph are
10 * duplicated in all such forms and that any documentation,
11 * advertising materials, and other materials related to such
12 * distribution and use acknowledge that the software was developed
13 * by the University of California, Berkeley. The name of the
14 * University may not be used to endorse or promote products derived
15 * from this software without specific prior written permission.
16 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
18 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
19 *
20 * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
21 * - Initial distribution.
22 *
23 *
24 * modified for KA9Q Internet Software Package by
25 * Katie Stevens (dkstevens@ucdavis.edu)
26 * University of California, Davis
27 * Computing Services
28 * - 01-31-90 initial adaptation (from 1.19)
29 * PPP.05 02-15-90 [ks]
30 * PPP.08 05-02-90 [ks] use PPP protocol field to signal compression
31 * PPP.15 09-90 [ks] improve mbuf handling
32 * PPP.16 11-02 [karn] substantially rewritten to use NOS facilities
33 *
34 * - Feb 1991 Bill_Simpson@um.cc.umich.edu
35 * variable number of conversation slots
36 * allow zero or one slots
37 * separate routines
38 * status display
39 * - Jul 1994 Dmitry Gorodchanin
40 * Fixes for memory leaks.
41 * - Oct 1994 Dmitry Gorodchanin
42 * Modularization.
43 * - Jan 1995 Bjorn Ekwall
44 * Use ip_fast_csum from ip.h
45 * - July 1995 Christos A. Polyzols
46 * Spotted bug in tcp option checking
47 *
48 *
49 * This module is a difficult issue. It's clearly inet code but it's also clearly
50 * driver code belonging close to PPP and SLIP
51 */
52
53#include <linux/module.h>
54#include <linux/slab.h>
55#include <linux/types.h>
56#include <linux/string.h>
57#include <linux/errno.h>
58#include <linux/kernel.h>
59#include <net/slhc_vj.h>
60
61#ifdef CONFIG_INET
62/* Entire module is for IP only */
63#include <linux/mm.h>
64#include <linux/socket.h>
65#include <linux/sockios.h>
66#include <linux/termios.h>
67#include <linux/in.h>
68#include <linux/fcntl.h>
69#include <linux/inet.h>
70#include <linux/netdevice.h>
71#include <net/ip.h>
72#include <net/protocol.h>
73#include <net/icmp.h>
74#include <net/tcp.h>
75#include <linux/skbuff.h>
76#include <net/sock.h>
77#include <linux/timer.h>
78#include <linux/uaccess.h>
79#include <net/checksum.h>
80#include <asm/unaligned.h>
81
82static unsigned char *encode(unsigned char *cp, unsigned short n);
83static long decode(unsigned char **cpp);
84static unsigned char * put16(unsigned char *cp, unsigned short x);
85static unsigned short pull16(unsigned char **cpp);
86
87/* Allocate compression data structure
88 * slots must be in range 0 to 255 (zero meaning no compression)
89 * Returns pointer to structure or ERR_PTR() on error.
90 */
91struct slcompress *
92slhc_init(int rslots, int tslots)
93{
94 register short i;
95 register struct cstate *ts;
96 struct slcompress *comp;
97
98 if (rslots < 0 || rslots > 255 || tslots < 0 || tslots > 255)
99 return ERR_PTR(-EINVAL);
100
101 comp = kzalloc(sizeof(struct slcompress), GFP_KERNEL);
102 if (! comp)
103 goto out_fail;
104
105 if (rslots > 0) {
106 size_t rsize = rslots * sizeof(struct cstate);
107 comp->rstate = kzalloc(rsize, GFP_KERNEL);
108 if (! comp->rstate)
109 goto out_free;
110 comp->rslot_limit = rslots - 1;
111 }
112
113 if (tslots > 0) {
114 size_t tsize = tslots * sizeof(struct cstate);
115 comp->tstate = kzalloc(tsize, GFP_KERNEL);
116 if (! comp->tstate)
117 goto out_free2;
118 comp->tslot_limit = tslots - 1;
119 }
120
121 comp->xmit_oldest = 0;
122 comp->xmit_current = 255;
123 comp->recv_current = 255;
124 /*
125 * don't accept any packets with implicit index until we get
126 * one with an explicit index. Otherwise the uncompress code
127 * will try to use connection 255, which is almost certainly
128 * out of range
129 */
130 comp->flags |= SLF_TOSS;
131
132 if ( tslots > 0 ) {
133 ts = comp->tstate;
134 for(i = comp->tslot_limit; i > 0; --i){
135 ts[i].cs_this = i;
136 ts[i].next = &(ts[i - 1]);
137 }
138 ts[0].next = &(ts[comp->tslot_limit]);
139 ts[0].cs_this = 0;
140 }
141 return comp;
142
143out_free2:
144 kfree(comp->rstate);
145out_free:
146 kfree(comp);
147out_fail:
148 return ERR_PTR(-ENOMEM);
149}
150
151
152/* Free a compression data structure */
153void
154slhc_free(struct slcompress *comp)
155{
156 if ( comp == NULLSLCOMPR )
157 return;
158
159 if ( comp->tstate != NULLSLSTATE )
160 kfree( comp->tstate );
161
162 if ( comp->rstate != NULLSLSTATE )
163 kfree( comp->rstate );
164
165 kfree( comp );
166}
167
168
169/* Put a short in host order into a char array in network order */
170static inline unsigned char *
171put16(unsigned char *cp, unsigned short x)
172{
173 *cp++ = x >> 8;
174 *cp++ = x;
175
176 return cp;
177}
178
179
180/* Encode a number */
181static unsigned char *
182encode(unsigned char *cp, unsigned short n)
183{
184 if(n >= 256 || n == 0){
185 *cp++ = 0;
186 cp = put16(cp,n);
187 } else {
188 *cp++ = n;
189 }
190 return cp;
191}
192
193/* Pull a 16-bit integer in host order from buffer in network byte order */
194static unsigned short
195pull16(unsigned char **cpp)
196{
197 short rval;
198
199 rval = *(*cpp)++;
200 rval <<= 8;
201 rval |= *(*cpp)++;
202 return rval;
203}
204
205/* Decode a number */
206static long
207decode(unsigned char **cpp)
208{
209 register int x;
210
211 x = *(*cpp)++;
212 if(x == 0){
213 return pull16(cpp) & 0xffff; /* pull16 returns -1 on error */
214 } else {
215 return x & 0xff; /* -1 if PULLCHAR returned error */
216 }
217}
218
219/*
220 * icp and isize are the original packet.
221 * ocp is a place to put a copy if necessary.
222 * cpp is initially a pointer to icp. If the copy is used,
223 * change it to ocp.
224 */
225
226int
227slhc_compress(struct slcompress *comp, unsigned char *icp, int isize,
228 unsigned char *ocp, unsigned char **cpp, int compress_cid)
229{
230 register struct cstate *ocs = &(comp->tstate[comp->xmit_oldest]);
231 register struct cstate *lcs = ocs;
232 register struct cstate *cs = lcs->next;
233 register unsigned long deltaS, deltaA;
234 register short changes = 0;
235 int hlen;
236 unsigned char new_seq[16];
237 register unsigned char *cp = new_seq;
238 struct iphdr *ip;
239 struct tcphdr *th, *oth;
240 __sum16 csum;
241
242
243 /*
244 * Don't play with runt packets.
245 */
246
247 if(isize<sizeof(struct iphdr))
248 return isize;
249
250 ip = (struct iphdr *) icp;
251
252 /* Bail if this packet isn't TCP, or is an IP fragment */
253 if (ip->protocol != IPPROTO_TCP || (ntohs(ip->frag_off) & 0x3fff)) {
254 /* Send as regular IP */
255 if(ip->protocol != IPPROTO_TCP)
256 comp->sls_o_nontcp++;
257 else
258 comp->sls_o_tcp++;
259 return isize;
260 }
261 /* Extract TCP header */
262
263 th = (struct tcphdr *)(((unsigned char *)ip) + ip->ihl*4);
264 hlen = ip->ihl*4 + th->doff*4;
265
266 /* Bail if the TCP packet isn't `compressible' (i.e., ACK isn't set or
267 * some other control bit is set). Also uncompressible if
268 * it's a runt.
269 */
270 if(hlen > isize || th->syn || th->fin || th->rst ||
271 ! (th->ack)){
272 /* TCP connection stuff; send as regular IP */
273 comp->sls_o_tcp++;
274 return isize;
275 }
276 /*
277 * Packet is compressible -- we're going to send either a
278 * COMPRESSED_TCP or UNCOMPRESSED_TCP packet. Either way,
279 * we need to locate (or create) the connection state.
280 *
281 * States are kept in a circularly linked list with
282 * xmit_oldest pointing to the end of the list. The
283 * list is kept in lru order by moving a state to the
284 * head of the list whenever it is referenced. Since
285 * the list is short and, empirically, the connection
286 * we want is almost always near the front, we locate
287 * states via linear search. If we don't find a state
288 * for the datagram, the oldest state is (re-)used.
289 */
290 for ( ; ; ) {
291 if( ip->saddr == cs->cs_ip.saddr
292 && ip->daddr == cs->cs_ip.daddr
293 && th->source == cs->cs_tcp.source
294 && th->dest == cs->cs_tcp.dest)
295 goto found;
296
297 /* if current equal oldest, at end of list */
298 if ( cs == ocs )
299 break;
300 lcs = cs;
301 cs = cs->next;
302 comp->sls_o_searches++;
303 }
304 /*
305 * Didn't find it -- re-use oldest cstate. Send an
306 * uncompressed packet that tells the other side what
307 * connection number we're using for this conversation.
308 *
309 * Note that since the state list is circular, the oldest
310 * state points to the newest and we only need to set
311 * xmit_oldest to update the lru linkage.
312 */
313 comp->sls_o_misses++;
314 comp->xmit_oldest = lcs->cs_this;
315 goto uncompressed;
316
317found:
318 /*
319 * Found it -- move to the front on the connection list.
320 */
321 if(lcs == ocs) {
322 /* found at most recently used */
323 } else if (cs == ocs) {
324 /* found at least recently used */
325 comp->xmit_oldest = lcs->cs_this;
326 } else {
327 /* more than 2 elements */
328 lcs->next = cs->next;
329 cs->next = ocs->next;
330 ocs->next = cs;
331 }
332
333 /*
334 * Make sure that only what we expect to change changed.
335 * Check the following:
336 * IP protocol version, header length & type of service.
337 * The "Don't fragment" bit.
338 * The time-to-live field.
339 * The TCP header length.
340 * IP options, if any.
341 * TCP options, if any.
342 * If any of these things are different between the previous &
343 * current datagram, we send the current datagram `uncompressed'.
344 */
345 oth = &cs->cs_tcp;
346
347 if(ip->version != cs->cs_ip.version || ip->ihl != cs->cs_ip.ihl
348 || ip->tos != cs->cs_ip.tos
349 || (ip->frag_off & htons(0x4000)) != (cs->cs_ip.frag_off & htons(0x4000))
350 || ip->ttl != cs->cs_ip.ttl
351 || th->doff != cs->cs_tcp.doff
352 || (ip->ihl > 5 && memcmp(ip+1,cs->cs_ipopt,((ip->ihl)-5)*4) != 0)
353 || (th->doff > 5 && memcmp(th+1,cs->cs_tcpopt,((th->doff)-5)*4) != 0)){
354 goto uncompressed;
355 }
356
357 /*
358 * Figure out which of the changing fields changed. The
359 * receiver expects changes in the order: urgent, window,
360 * ack, seq (the order minimizes the number of temporaries
361 * needed in this section of code).
362 */
363 if(th->urg){
364 deltaS = ntohs(th->urg_ptr);
365 cp = encode(cp,deltaS);
366 changes |= NEW_U;
367 } else if(th->urg_ptr != oth->urg_ptr){
368 /* argh! URG not set but urp changed -- a sensible
369 * implementation should never do this but RFC793
370 * doesn't prohibit the change so we have to deal
371 * with it. */
372 goto uncompressed;
373 }
374 if((deltaS = ntohs(th->window) - ntohs(oth->window)) != 0){
375 cp = encode(cp,deltaS);
376 changes |= NEW_W;
377 }
378 if((deltaA = ntohl(th->ack_seq) - ntohl(oth->ack_seq)) != 0L){
379 if(deltaA > 0x0000ffff)
380 goto uncompressed;
381 cp = encode(cp,deltaA);
382 changes |= NEW_A;
383 }
384 if((deltaS = ntohl(th->seq) - ntohl(oth->seq)) != 0L){
385 if(deltaS > 0x0000ffff)
386 goto uncompressed;
387 cp = encode(cp,deltaS);
388 changes |= NEW_S;
389 }
390
391 switch(changes){
392 case 0: /* Nothing changed. If this packet contains data and the
393 * last one didn't, this is probably a data packet following
394 * an ack (normal on an interactive connection) and we send
395 * it compressed. Otherwise it's probably a retransmit,
396 * retransmitted ack or window probe. Send it uncompressed
397 * in case the other side missed the compressed version.
398 */
399 if(ip->tot_len != cs->cs_ip.tot_len &&
400 ntohs(cs->cs_ip.tot_len) == hlen)
401 break;
402 goto uncompressed;
403 case SPECIAL_I:
404 case SPECIAL_D:
405 /* actual changes match one of our special case encodings --
406 * send packet uncompressed.
407 */
408 goto uncompressed;
409 case NEW_S|NEW_A:
410 if(deltaS == deltaA &&
411 deltaS == ntohs(cs->cs_ip.tot_len) - hlen){
412 /* special case for echoed terminal traffic */
413 changes = SPECIAL_I;
414 cp = new_seq;
415 }
416 break;
417 case NEW_S:
418 if(deltaS == ntohs(cs->cs_ip.tot_len) - hlen){
419 /* special case for data xfer */
420 changes = SPECIAL_D;
421 cp = new_seq;
422 }
423 break;
424 }
425 deltaS = ntohs(ip->id) - ntohs(cs->cs_ip.id);
426 if(deltaS != 1){
427 cp = encode(cp,deltaS);
428 changes |= NEW_I;
429 }
430 if(th->psh)
431 changes |= TCP_PUSH_BIT;
432 /* Grab the cksum before we overwrite it below. Then update our
433 * state with this packet's header.
434 */
435 csum = th->check;
436 memcpy(&cs->cs_ip,ip,20);
437 memcpy(&cs->cs_tcp,th,20);
438 /* We want to use the original packet as our compressed packet.
439 * (cp - new_seq) is the number of bytes we need for compressed
440 * sequence numbers. In addition we need one byte for the change
441 * mask, one for the connection id and two for the tcp checksum.
442 * So, (cp - new_seq) + 4 bytes of header are needed.
443 */
444 deltaS = cp - new_seq;
445 if(compress_cid == 0 || comp->xmit_current != cs->cs_this){
446 cp = ocp;
447 *cpp = ocp;
448 *cp++ = changes | NEW_C;
449 *cp++ = cs->cs_this;
450 comp->xmit_current = cs->cs_this;
451 } else {
452 cp = ocp;
453 *cpp = ocp;
454 *cp++ = changes;
455 }
456 *(__sum16 *)cp = csum;
457 cp += 2;
458/* deltaS is now the size of the change section of the compressed header */
459 memcpy(cp,new_seq,deltaS); /* Write list of deltas */
460 memcpy(cp+deltaS,icp+hlen,isize-hlen);
461 comp->sls_o_compressed++;
462 ocp[0] |= SL_TYPE_COMPRESSED_TCP;
463 return isize - hlen + deltaS + (cp - ocp);
464
465 /* Update connection state cs & send uncompressed packet (i.e.,
466 * a regular ip/tcp packet but with the 'conversation id' we hope
467 * to use on future compressed packets in the protocol field).
468 */
469uncompressed:
470 memcpy(&cs->cs_ip,ip,20);
471 memcpy(&cs->cs_tcp,th,20);
472 if (ip->ihl > 5)
473 memcpy(cs->cs_ipopt, ip+1, ((ip->ihl) - 5) * 4);
474 if (th->doff > 5)
475 memcpy(cs->cs_tcpopt, th+1, ((th->doff) - 5) * 4);
476 comp->xmit_current = cs->cs_this;
477 comp->sls_o_uncompressed++;
478 memcpy(ocp, icp, isize);
479 *cpp = ocp;
480 ocp[9] = cs->cs_this;
481 ocp[0] |= SL_TYPE_UNCOMPRESSED_TCP;
482 return isize;
483}
484
485
486int
487slhc_uncompress(struct slcompress *comp, unsigned char *icp, int isize)
488{
489 register int changes;
490 long x;
491 register struct tcphdr *thp;
492 register struct iphdr *ip;
493 register struct cstate *cs;
494 int len, hdrlen;
495 unsigned char *cp = icp;
496
497 /* We've got a compressed packet; read the change byte */
498 comp->sls_i_compressed++;
499 if(isize < 3){
500 comp->sls_i_error++;
501 return 0;
502 }
503 changes = *cp++;
504 if(changes & NEW_C){
505 /* Make sure the state index is in range, then grab the state.
506 * If we have a good state index, clear the 'discard' flag.
507 */
508 x = *cp++; /* Read conn index */
509 if(x < 0 || x > comp->rslot_limit)
510 goto bad;
511
512 /* Check if the cstate is initialized */
513 if (!comp->rstate[x].initialized)
514 goto bad;
515
516 comp->flags &=~ SLF_TOSS;
517 comp->recv_current = x;
518 } else {
519 /* this packet has an implicit state index. If we've
520 * had a line error since the last time we got an
521 * explicit state index, we have to toss the packet. */
522 if(comp->flags & SLF_TOSS){
523 comp->sls_i_tossed++;
524 return 0;
525 }
526 }
527 cs = &comp->rstate[comp->recv_current];
528 thp = &cs->cs_tcp;
529 ip = &cs->cs_ip;
530
531 thp->check = *(__sum16 *)cp;
532 cp += 2;
533
534 thp->psh = (changes & TCP_PUSH_BIT) ? 1 : 0;
535/*
536 * we can use the same number for the length of the saved header and
537 * the current one, because the packet wouldn't have been sent
538 * as compressed unless the options were the same as the previous one
539 */
540
541 hdrlen = ip->ihl * 4 + thp->doff * 4;
542
543 switch(changes & SPECIALS_MASK){
544 case SPECIAL_I: /* Echoed terminal traffic */
545 {
546 register short i;
547 i = ntohs(ip->tot_len) - hdrlen;
548 thp->ack_seq = htonl( ntohl(thp->ack_seq) + i);
549 thp->seq = htonl( ntohl(thp->seq) + i);
550 }
551 break;
552
553 case SPECIAL_D: /* Unidirectional data */
554 thp->seq = htonl( ntohl(thp->seq) +
555 ntohs(ip->tot_len) - hdrlen);
556 break;
557
558 default:
559 if(changes & NEW_U){
560 thp->urg = 1;
561 if((x = decode(&cp)) == -1) {
562 goto bad;
563 }
564 thp->urg_ptr = htons(x);
565 } else
566 thp->urg = 0;
567 if(changes & NEW_W){
568 if((x = decode(&cp)) == -1) {
569 goto bad;
570 }
571 thp->window = htons( ntohs(thp->window) + x);
572 }
573 if(changes & NEW_A){
574 if((x = decode(&cp)) == -1) {
575 goto bad;
576 }
577 thp->ack_seq = htonl( ntohl(thp->ack_seq) + x);
578 }
579 if(changes & NEW_S){
580 if((x = decode(&cp)) == -1) {
581 goto bad;
582 }
583 thp->seq = htonl( ntohl(thp->seq) + x);
584 }
585 break;
586 }
587 if(changes & NEW_I){
588 if((x = decode(&cp)) == -1) {
589 goto bad;
590 }
591 ip->id = htons (ntohs (ip->id) + x);
592 } else
593 ip->id = htons (ntohs (ip->id) + 1);
594
595 /*
596 * At this point, cp points to the first byte of data in the
597 * packet. Put the reconstructed TCP and IP headers back on the
598 * packet. Recalculate IP checksum (but not TCP checksum).
599 */
600
601 len = isize - (cp - icp);
602 if (len < 0)
603 goto bad;
604 len += hdrlen;
605 ip->tot_len = htons(len);
606 ip->check = 0;
607
608 memmove(icp + hdrlen, cp, len - hdrlen);
609
610 cp = icp;
611 memcpy(cp, ip, 20);
612 cp += 20;
613
614 if (ip->ihl > 5) {
615 memcpy(cp, cs->cs_ipopt, (ip->ihl - 5) * 4);
616 cp += (ip->ihl - 5) * 4;
617 }
618
619 put_unaligned(ip_fast_csum(icp, ip->ihl),
620 &((struct iphdr *)icp)->check);
621
622 memcpy(cp, thp, 20);
623 cp += 20;
624
625 if (thp->doff > 5) {
626 memcpy(cp, cs->cs_tcpopt, ((thp->doff) - 5) * 4);
627 cp += ((thp->doff) - 5) * 4;
628 }
629
630 return len;
631bad:
632 comp->sls_i_error++;
633 return slhc_toss( comp );
634}
635
636
637int
638slhc_remember(struct slcompress *comp, unsigned char *icp, int isize)
639{
640 register struct cstate *cs;
641 unsigned ihl;
642
643 unsigned char index;
644
645 if(isize < 20) {
646 /* The packet is shorter than a legal IP header */
647 comp->sls_i_runt++;
648 return slhc_toss( comp );
649 }
650 /* Peek at the IP header's IHL field to find its length */
651 ihl = icp[0] & 0xf;
652 if(ihl < 20 / 4){
653 /* The IP header length field is too small */
654 comp->sls_i_runt++;
655 return slhc_toss( comp );
656 }
657 index = icp[9];
658 icp[9] = IPPROTO_TCP;
659
660 if (ip_fast_csum(icp, ihl)) {
661 /* Bad IP header checksum; discard */
662 comp->sls_i_badcheck++;
663 return slhc_toss( comp );
664 }
665 if(index > comp->rslot_limit) {
666 comp->sls_i_error++;
667 return slhc_toss(comp);
668 }
669
670 /* Update local state */
671 cs = &comp->rstate[comp->recv_current = index];
672 comp->flags &=~ SLF_TOSS;
673 memcpy(&cs->cs_ip,icp,20);
674 memcpy(&cs->cs_tcp,icp + ihl*4,20);
675 if (ihl > 5)
676 memcpy(cs->cs_ipopt, icp + sizeof(struct iphdr), (ihl - 5) * 4);
677 if (cs->cs_tcp.doff > 5)
678 memcpy(cs->cs_tcpopt, icp + ihl*4 + sizeof(struct tcphdr), (cs->cs_tcp.doff - 5) * 4);
679 cs->cs_hsize = ihl*2 + cs->cs_tcp.doff*2;
680 cs->initialized = true;
681 /* Put headers back on packet
682 * Neither header checksum is recalculated
683 */
684 comp->sls_i_uncompressed++;
685 return isize;
686}
687
688int
689slhc_toss(struct slcompress *comp)
690{
691 if ( comp == NULLSLCOMPR )
692 return 0;
693
694 comp->flags |= SLF_TOSS;
695 return 0;
696}
697
698#else /* CONFIG_INET */
699
700int
701slhc_toss(struct slcompress *comp)
702{
703 printk(KERN_DEBUG "Called IP function on non IP-system: slhc_toss");
704 return -EINVAL;
705}
706int
707slhc_uncompress(struct slcompress *comp, unsigned char *icp, int isize)
708{
709 printk(KERN_DEBUG "Called IP function on non IP-system: slhc_uncompress");
710 return -EINVAL;
711}
712int
713slhc_compress(struct slcompress *comp, unsigned char *icp, int isize,
714 unsigned char *ocp, unsigned char **cpp, int compress_cid)
715{
716 printk(KERN_DEBUG "Called IP function on non IP-system: slhc_compress");
717 return -EINVAL;
718}
719
720int
721slhc_remember(struct slcompress *comp, unsigned char *icp, int isize)
722{
723 printk(KERN_DEBUG "Called IP function on non IP-system: slhc_remember");
724 return -EINVAL;
725}
726
727void
728slhc_free(struct slcompress *comp)
729{
730 printk(KERN_DEBUG "Called IP function on non IP-system: slhc_free");
731}
732struct slcompress *
733slhc_init(int rslots, int tslots)
734{
735 printk(KERN_DEBUG "Called IP function on non IP-system: slhc_init");
736 return NULL;
737}
738
739#endif /* CONFIG_INET */
740
741/* VJ header compression */
742EXPORT_SYMBOL(slhc_init);
743EXPORT_SYMBOL(slhc_free);
744EXPORT_SYMBOL(slhc_remember);
745EXPORT_SYMBOL(slhc_compress);
746EXPORT_SYMBOL(slhc_uncompress);
747EXPORT_SYMBOL(slhc_toss);
748
749MODULE_LICENSE("Dual BSD/GPL");
1/*
2 * Routines to compress and uncompress tcp packets (for transmission
3 * over low speed serial lines).
4 *
5 * Copyright (c) 1989 Regents of the University of California.
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms are permitted
9 * provided that the above copyright notice and this paragraph are
10 * duplicated in all such forms and that any documentation,
11 * advertising materials, and other materials related to such
12 * distribution and use acknowledge that the software was developed
13 * by the University of California, Berkeley. The name of the
14 * University may not be used to endorse or promote products derived
15 * from this software without specific prior written permission.
16 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
18 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
19 *
20 * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
21 * - Initial distribution.
22 *
23 *
24 * modified for KA9Q Internet Software Package by
25 * Katie Stevens (dkstevens@ucdavis.edu)
26 * University of California, Davis
27 * Computing Services
28 * - 01-31-90 initial adaptation (from 1.19)
29 * PPP.05 02-15-90 [ks]
30 * PPP.08 05-02-90 [ks] use PPP protocol field to signal compression
31 * PPP.15 09-90 [ks] improve mbuf handling
32 * PPP.16 11-02 [karn] substantially rewritten to use NOS facilities
33 *
34 * - Feb 1991 Bill_Simpson@um.cc.umich.edu
35 * variable number of conversation slots
36 * allow zero or one slots
37 * separate routines
38 * status display
39 * - Jul 1994 Dmitry Gorodchanin
40 * Fixes for memory leaks.
41 * - Oct 1994 Dmitry Gorodchanin
42 * Modularization.
43 * - Jan 1995 Bjorn Ekwall
44 * Use ip_fast_csum from ip.h
45 * - July 1995 Christos A. Polyzols
46 * Spotted bug in tcp option checking
47 *
48 *
49 * This module is a difficult issue. It's clearly inet code but it's also clearly
50 * driver code belonging close to PPP and SLIP
51 */
52
53#include <linux/module.h>
54#include <linux/slab.h>
55#include <linux/types.h>
56#include <linux/string.h>
57#include <linux/errno.h>
58#include <linux/kernel.h>
59#include <net/slhc_vj.h>
60
61#ifdef CONFIG_INET
62/* Entire module is for IP only */
63#include <linux/mm.h>
64#include <linux/socket.h>
65#include <linux/sockios.h>
66#include <linux/termios.h>
67#include <linux/in.h>
68#include <linux/fcntl.h>
69#include <linux/inet.h>
70#include <linux/netdevice.h>
71#include <net/ip.h>
72#include <net/protocol.h>
73#include <net/icmp.h>
74#include <net/tcp.h>
75#include <linux/skbuff.h>
76#include <net/sock.h>
77#include <linux/timer.h>
78#include <asm/uaccess.h>
79#include <net/checksum.h>
80#include <asm/unaligned.h>
81
82static unsigned char *encode(unsigned char *cp, unsigned short n);
83static long decode(unsigned char **cpp);
84static unsigned char * put16(unsigned char *cp, unsigned short x);
85static unsigned short pull16(unsigned char **cpp);
86
87/* Initialize compression data structure
88 * slots must be in range 0 to 255 (zero meaning no compression)
89 */
90struct slcompress *
91slhc_init(int rslots, int tslots)
92{
93 register short i;
94 register struct cstate *ts;
95 struct slcompress *comp;
96
97 comp = kzalloc(sizeof(struct slcompress), GFP_KERNEL);
98 if (! comp)
99 goto out_fail;
100
101 if ( rslots > 0 && rslots < 256 ) {
102 size_t rsize = rslots * sizeof(struct cstate);
103 comp->rstate = kzalloc(rsize, GFP_KERNEL);
104 if (! comp->rstate)
105 goto out_free;
106 comp->rslot_limit = rslots - 1;
107 }
108
109 if ( tslots > 0 && tslots < 256 ) {
110 size_t tsize = tslots * sizeof(struct cstate);
111 comp->tstate = kzalloc(tsize, GFP_KERNEL);
112 if (! comp->tstate)
113 goto out_free2;
114 comp->tslot_limit = tslots - 1;
115 }
116
117 comp->xmit_oldest = 0;
118 comp->xmit_current = 255;
119 comp->recv_current = 255;
120 /*
121 * don't accept any packets with implicit index until we get
122 * one with an explicit index. Otherwise the uncompress code
123 * will try to use connection 255, which is almost certainly
124 * out of range
125 */
126 comp->flags |= SLF_TOSS;
127
128 if ( tslots > 0 ) {
129 ts = comp->tstate;
130 for(i = comp->tslot_limit; i > 0; --i){
131 ts[i].cs_this = i;
132 ts[i].next = &(ts[i - 1]);
133 }
134 ts[0].next = &(ts[comp->tslot_limit]);
135 ts[0].cs_this = 0;
136 }
137 return comp;
138
139out_free2:
140 kfree(comp->rstate);
141out_free:
142 kfree(comp);
143out_fail:
144 return NULL;
145}
146
147
148/* Free a compression data structure */
149void
150slhc_free(struct slcompress *comp)
151{
152 if ( comp == NULLSLCOMPR )
153 return;
154
155 if ( comp->tstate != NULLSLSTATE )
156 kfree( comp->tstate );
157
158 if ( comp->rstate != NULLSLSTATE )
159 kfree( comp->rstate );
160
161 kfree( comp );
162}
163
164
165/* Put a short in host order into a char array in network order */
166static inline unsigned char *
167put16(unsigned char *cp, unsigned short x)
168{
169 *cp++ = x >> 8;
170 *cp++ = x;
171
172 return cp;
173}
174
175
176/* Encode a number */
177static unsigned char *
178encode(unsigned char *cp, unsigned short n)
179{
180 if(n >= 256 || n == 0){
181 *cp++ = 0;
182 cp = put16(cp,n);
183 } else {
184 *cp++ = n;
185 }
186 return cp;
187}
188
189/* Pull a 16-bit integer in host order from buffer in network byte order */
190static unsigned short
191pull16(unsigned char **cpp)
192{
193 short rval;
194
195 rval = *(*cpp)++;
196 rval <<= 8;
197 rval |= *(*cpp)++;
198 return rval;
199}
200
201/* Decode a number */
202static long
203decode(unsigned char **cpp)
204{
205 register int x;
206
207 x = *(*cpp)++;
208 if(x == 0){
209 return pull16(cpp) & 0xffff; /* pull16 returns -1 on error */
210 } else {
211 return x & 0xff; /* -1 if PULLCHAR returned error */
212 }
213}
214
215/*
216 * icp and isize are the original packet.
217 * ocp is a place to put a copy if necessary.
218 * cpp is initially a pointer to icp. If the copy is used,
219 * change it to ocp.
220 */
221
222int
223slhc_compress(struct slcompress *comp, unsigned char *icp, int isize,
224 unsigned char *ocp, unsigned char **cpp, int compress_cid)
225{
226 register struct cstate *ocs = &(comp->tstate[comp->xmit_oldest]);
227 register struct cstate *lcs = ocs;
228 register struct cstate *cs = lcs->next;
229 register unsigned long deltaS, deltaA;
230 register short changes = 0;
231 int hlen;
232 unsigned char new_seq[16];
233 register unsigned char *cp = new_seq;
234 struct iphdr *ip;
235 struct tcphdr *th, *oth;
236 __sum16 csum;
237
238
239 /*
240 * Don't play with runt packets.
241 */
242
243 if(isize<sizeof(struct iphdr))
244 return isize;
245
246 ip = (struct iphdr *) icp;
247
248 /* Bail if this packet isn't TCP, or is an IP fragment */
249 if (ip->protocol != IPPROTO_TCP || (ntohs(ip->frag_off) & 0x3fff)) {
250 /* Send as regular IP */
251 if(ip->protocol != IPPROTO_TCP)
252 comp->sls_o_nontcp++;
253 else
254 comp->sls_o_tcp++;
255 return isize;
256 }
257 /* Extract TCP header */
258
259 th = (struct tcphdr *)(((unsigned char *)ip) + ip->ihl*4);
260 hlen = ip->ihl*4 + th->doff*4;
261
262 /* Bail if the TCP packet isn't `compressible' (i.e., ACK isn't set or
263 * some other control bit is set). Also uncompressible if
264 * it's a runt.
265 */
266 if(hlen > isize || th->syn || th->fin || th->rst ||
267 ! (th->ack)){
268 /* TCP connection stuff; send as regular IP */
269 comp->sls_o_tcp++;
270 return isize;
271 }
272 /*
273 * Packet is compressible -- we're going to send either a
274 * COMPRESSED_TCP or UNCOMPRESSED_TCP packet. Either way,
275 * we need to locate (or create) the connection state.
276 *
277 * States are kept in a circularly linked list with
278 * xmit_oldest pointing to the end of the list. The
279 * list is kept in lru order by moving a state to the
280 * head of the list whenever it is referenced. Since
281 * the list is short and, empirically, the connection
282 * we want is almost always near the front, we locate
283 * states via linear search. If we don't find a state
284 * for the datagram, the oldest state is (re-)used.
285 */
286 for ( ; ; ) {
287 if( ip->saddr == cs->cs_ip.saddr
288 && ip->daddr == cs->cs_ip.daddr
289 && th->source == cs->cs_tcp.source
290 && th->dest == cs->cs_tcp.dest)
291 goto found;
292
293 /* if current equal oldest, at end of list */
294 if ( cs == ocs )
295 break;
296 lcs = cs;
297 cs = cs->next;
298 comp->sls_o_searches++;
299 }
300 /*
301 * Didn't find it -- re-use oldest cstate. Send an
302 * uncompressed packet that tells the other side what
303 * connection number we're using for this conversation.
304 *
305 * Note that since the state list is circular, the oldest
306 * state points to the newest and we only need to set
307 * xmit_oldest to update the lru linkage.
308 */
309 comp->sls_o_misses++;
310 comp->xmit_oldest = lcs->cs_this;
311 goto uncompressed;
312
313found:
314 /*
315 * Found it -- move to the front on the connection list.
316 */
317 if(lcs == ocs) {
318 /* found at most recently used */
319 } else if (cs == ocs) {
320 /* found at least recently used */
321 comp->xmit_oldest = lcs->cs_this;
322 } else {
323 /* more than 2 elements */
324 lcs->next = cs->next;
325 cs->next = ocs->next;
326 ocs->next = cs;
327 }
328
329 /*
330 * Make sure that only what we expect to change changed.
331 * Check the following:
332 * IP protocol version, header length & type of service.
333 * The "Don't fragment" bit.
334 * The time-to-live field.
335 * The TCP header length.
336 * IP options, if any.
337 * TCP options, if any.
338 * If any of these things are different between the previous &
339 * current datagram, we send the current datagram `uncompressed'.
340 */
341 oth = &cs->cs_tcp;
342
343 if(ip->version != cs->cs_ip.version || ip->ihl != cs->cs_ip.ihl
344 || ip->tos != cs->cs_ip.tos
345 || (ip->frag_off & htons(0x4000)) != (cs->cs_ip.frag_off & htons(0x4000))
346 || ip->ttl != cs->cs_ip.ttl
347 || th->doff != cs->cs_tcp.doff
348 || (ip->ihl > 5 && memcmp(ip+1,cs->cs_ipopt,((ip->ihl)-5)*4) != 0)
349 || (th->doff > 5 && memcmp(th+1,cs->cs_tcpopt,((th->doff)-5)*4) != 0)){
350 goto uncompressed;
351 }
352
353 /*
354 * Figure out which of the changing fields changed. The
355 * receiver expects changes in the order: urgent, window,
356 * ack, seq (the order minimizes the number of temporaries
357 * needed in this section of code).
358 */
359 if(th->urg){
360 deltaS = ntohs(th->urg_ptr);
361 cp = encode(cp,deltaS);
362 changes |= NEW_U;
363 } else if(th->urg_ptr != oth->urg_ptr){
364 /* argh! URG not set but urp changed -- a sensible
365 * implementation should never do this but RFC793
366 * doesn't prohibit the change so we have to deal
367 * with it. */
368 goto uncompressed;
369 }
370 if((deltaS = ntohs(th->window) - ntohs(oth->window)) != 0){
371 cp = encode(cp,deltaS);
372 changes |= NEW_W;
373 }
374 if((deltaA = ntohl(th->ack_seq) - ntohl(oth->ack_seq)) != 0L){
375 if(deltaA > 0x0000ffff)
376 goto uncompressed;
377 cp = encode(cp,deltaA);
378 changes |= NEW_A;
379 }
380 if((deltaS = ntohl(th->seq) - ntohl(oth->seq)) != 0L){
381 if(deltaS > 0x0000ffff)
382 goto uncompressed;
383 cp = encode(cp,deltaS);
384 changes |= NEW_S;
385 }
386
387 switch(changes){
388 case 0: /* Nothing changed. If this packet contains data and the
389 * last one didn't, this is probably a data packet following
390 * an ack (normal on an interactive connection) and we send
391 * it compressed. Otherwise it's probably a retransmit,
392 * retransmitted ack or window probe. Send it uncompressed
393 * in case the other side missed the compressed version.
394 */
395 if(ip->tot_len != cs->cs_ip.tot_len &&
396 ntohs(cs->cs_ip.tot_len) == hlen)
397 break;
398 goto uncompressed;
399 break;
400 case SPECIAL_I:
401 case SPECIAL_D:
402 /* actual changes match one of our special case encodings --
403 * send packet uncompressed.
404 */
405 goto uncompressed;
406 case NEW_S|NEW_A:
407 if(deltaS == deltaA &&
408 deltaS == ntohs(cs->cs_ip.tot_len) - hlen){
409 /* special case for echoed terminal traffic */
410 changes = SPECIAL_I;
411 cp = new_seq;
412 }
413 break;
414 case NEW_S:
415 if(deltaS == ntohs(cs->cs_ip.tot_len) - hlen){
416 /* special case for data xfer */
417 changes = SPECIAL_D;
418 cp = new_seq;
419 }
420 break;
421 }
422 deltaS = ntohs(ip->id) - ntohs(cs->cs_ip.id);
423 if(deltaS != 1){
424 cp = encode(cp,deltaS);
425 changes |= NEW_I;
426 }
427 if(th->psh)
428 changes |= TCP_PUSH_BIT;
429 /* Grab the cksum before we overwrite it below. Then update our
430 * state with this packet's header.
431 */
432 csum = th->check;
433 memcpy(&cs->cs_ip,ip,20);
434 memcpy(&cs->cs_tcp,th,20);
435 /* We want to use the original packet as our compressed packet.
436 * (cp - new_seq) is the number of bytes we need for compressed
437 * sequence numbers. In addition we need one byte for the change
438 * mask, one for the connection id and two for the tcp checksum.
439 * So, (cp - new_seq) + 4 bytes of header are needed.
440 */
441 deltaS = cp - new_seq;
442 if(compress_cid == 0 || comp->xmit_current != cs->cs_this){
443 cp = ocp;
444 *cpp = ocp;
445 *cp++ = changes | NEW_C;
446 *cp++ = cs->cs_this;
447 comp->xmit_current = cs->cs_this;
448 } else {
449 cp = ocp;
450 *cpp = ocp;
451 *cp++ = changes;
452 }
453 *(__sum16 *)cp = csum;
454 cp += 2;
455/* deltaS is now the size of the change section of the compressed header */
456 memcpy(cp,new_seq,deltaS); /* Write list of deltas */
457 memcpy(cp+deltaS,icp+hlen,isize-hlen);
458 comp->sls_o_compressed++;
459 ocp[0] |= SL_TYPE_COMPRESSED_TCP;
460 return isize - hlen + deltaS + (cp - ocp);
461
462 /* Update connection state cs & send uncompressed packet (i.e.,
463 * a regular ip/tcp packet but with the 'conversation id' we hope
464 * to use on future compressed packets in the protocol field).
465 */
466uncompressed:
467 memcpy(&cs->cs_ip,ip,20);
468 memcpy(&cs->cs_tcp,th,20);
469 if (ip->ihl > 5)
470 memcpy(cs->cs_ipopt, ip+1, ((ip->ihl) - 5) * 4);
471 if (th->doff > 5)
472 memcpy(cs->cs_tcpopt, th+1, ((th->doff) - 5) * 4);
473 comp->xmit_current = cs->cs_this;
474 comp->sls_o_uncompressed++;
475 memcpy(ocp, icp, isize);
476 *cpp = ocp;
477 ocp[9] = cs->cs_this;
478 ocp[0] |= SL_TYPE_UNCOMPRESSED_TCP;
479 return isize;
480}
481
482
483int
484slhc_uncompress(struct slcompress *comp, unsigned char *icp, int isize)
485{
486 register int changes;
487 long x;
488 register struct tcphdr *thp;
489 register struct iphdr *ip;
490 register struct cstate *cs;
491 int len, hdrlen;
492 unsigned char *cp = icp;
493
494 /* We've got a compressed packet; read the change byte */
495 comp->sls_i_compressed++;
496 if(isize < 3){
497 comp->sls_i_error++;
498 return 0;
499 }
500 changes = *cp++;
501 if(changes & NEW_C){
502 /* Make sure the state index is in range, then grab the state.
503 * If we have a good state index, clear the 'discard' flag.
504 */
505 x = *cp++; /* Read conn index */
506 if(x < 0 || x > comp->rslot_limit)
507 goto bad;
508
509 comp->flags &=~ SLF_TOSS;
510 comp->recv_current = x;
511 } else {
512 /* this packet has an implicit state index. If we've
513 * had a line error since the last time we got an
514 * explicit state index, we have to toss the packet. */
515 if(comp->flags & SLF_TOSS){
516 comp->sls_i_tossed++;
517 return 0;
518 }
519 }
520 cs = &comp->rstate[comp->recv_current];
521 thp = &cs->cs_tcp;
522 ip = &cs->cs_ip;
523
524 thp->check = *(__sum16 *)cp;
525 cp += 2;
526
527 thp->psh = (changes & TCP_PUSH_BIT) ? 1 : 0;
528/*
529 * we can use the same number for the length of the saved header and
530 * the current one, because the packet wouldn't have been sent
531 * as compressed unless the options were the same as the previous one
532 */
533
534 hdrlen = ip->ihl * 4 + thp->doff * 4;
535
536 switch(changes & SPECIALS_MASK){
537 case SPECIAL_I: /* Echoed terminal traffic */
538 {
539 register short i;
540 i = ntohs(ip->tot_len) - hdrlen;
541 thp->ack_seq = htonl( ntohl(thp->ack_seq) + i);
542 thp->seq = htonl( ntohl(thp->seq) + i);
543 }
544 break;
545
546 case SPECIAL_D: /* Unidirectional data */
547 thp->seq = htonl( ntohl(thp->seq) +
548 ntohs(ip->tot_len) - hdrlen);
549 break;
550
551 default:
552 if(changes & NEW_U){
553 thp->urg = 1;
554 if((x = decode(&cp)) == -1) {
555 goto bad;
556 }
557 thp->urg_ptr = htons(x);
558 } else
559 thp->urg = 0;
560 if(changes & NEW_W){
561 if((x = decode(&cp)) == -1) {
562 goto bad;
563 }
564 thp->window = htons( ntohs(thp->window) + x);
565 }
566 if(changes & NEW_A){
567 if((x = decode(&cp)) == -1) {
568 goto bad;
569 }
570 thp->ack_seq = htonl( ntohl(thp->ack_seq) + x);
571 }
572 if(changes & NEW_S){
573 if((x = decode(&cp)) == -1) {
574 goto bad;
575 }
576 thp->seq = htonl( ntohl(thp->seq) + x);
577 }
578 break;
579 }
580 if(changes & NEW_I){
581 if((x = decode(&cp)) == -1) {
582 goto bad;
583 }
584 ip->id = htons (ntohs (ip->id) + x);
585 } else
586 ip->id = htons (ntohs (ip->id) + 1);
587
588 /*
589 * At this point, cp points to the first byte of data in the
590 * packet. Put the reconstructed TCP and IP headers back on the
591 * packet. Recalculate IP checksum (but not TCP checksum).
592 */
593
594 len = isize - (cp - icp);
595 if (len < 0)
596 goto bad;
597 len += hdrlen;
598 ip->tot_len = htons(len);
599 ip->check = 0;
600
601 memmove(icp + hdrlen, cp, len - hdrlen);
602
603 cp = icp;
604 memcpy(cp, ip, 20);
605 cp += 20;
606
607 if (ip->ihl > 5) {
608 memcpy(cp, cs->cs_ipopt, (ip->ihl - 5) * 4);
609 cp += (ip->ihl - 5) * 4;
610 }
611
612 put_unaligned(ip_fast_csum(icp, ip->ihl),
613 &((struct iphdr *)icp)->check);
614
615 memcpy(cp, thp, 20);
616 cp += 20;
617
618 if (thp->doff > 5) {
619 memcpy(cp, cs->cs_tcpopt, ((thp->doff) - 5) * 4);
620 cp += ((thp->doff) - 5) * 4;
621 }
622
623 return len;
624bad:
625 comp->sls_i_error++;
626 return slhc_toss( comp );
627}
628
629
630int
631slhc_remember(struct slcompress *comp, unsigned char *icp, int isize)
632{
633 register struct cstate *cs;
634 unsigned ihl;
635
636 unsigned char index;
637
638 if(isize < 20) {
639 /* The packet is shorter than a legal IP header */
640 comp->sls_i_runt++;
641 return slhc_toss( comp );
642 }
643 /* Peek at the IP header's IHL field to find its length */
644 ihl = icp[0] & 0xf;
645 if(ihl < 20 / 4){
646 /* The IP header length field is too small */
647 comp->sls_i_runt++;
648 return slhc_toss( comp );
649 }
650 index = icp[9];
651 icp[9] = IPPROTO_TCP;
652
653 if (ip_fast_csum(icp, ihl)) {
654 /* Bad IP header checksum; discard */
655 comp->sls_i_badcheck++;
656 return slhc_toss( comp );
657 }
658 if(index > comp->rslot_limit) {
659 comp->sls_i_error++;
660 return slhc_toss(comp);
661 }
662
663 /* Update local state */
664 cs = &comp->rstate[comp->recv_current = index];
665 comp->flags &=~ SLF_TOSS;
666 memcpy(&cs->cs_ip,icp,20);
667 memcpy(&cs->cs_tcp,icp + ihl*4,20);
668 if (ihl > 5)
669 memcpy(cs->cs_ipopt, icp + sizeof(struct iphdr), (ihl - 5) * 4);
670 if (cs->cs_tcp.doff > 5)
671 memcpy(cs->cs_tcpopt, icp + ihl*4 + sizeof(struct tcphdr), (cs->cs_tcp.doff - 5) * 4);
672 cs->cs_hsize = ihl*2 + cs->cs_tcp.doff*2;
673 /* Put headers back on packet
674 * Neither header checksum is recalculated
675 */
676 comp->sls_i_uncompressed++;
677 return isize;
678}
679
680int
681slhc_toss(struct slcompress *comp)
682{
683 if ( comp == NULLSLCOMPR )
684 return 0;
685
686 comp->flags |= SLF_TOSS;
687 return 0;
688}
689
690#else /* CONFIG_INET */
691
692int
693slhc_toss(struct slcompress *comp)
694{
695 printk(KERN_DEBUG "Called IP function on non IP-system: slhc_toss");
696 return -EINVAL;
697}
698int
699slhc_uncompress(struct slcompress *comp, unsigned char *icp, int isize)
700{
701 printk(KERN_DEBUG "Called IP function on non IP-system: slhc_uncompress");
702 return -EINVAL;
703}
704int
705slhc_compress(struct slcompress *comp, unsigned char *icp, int isize,
706 unsigned char *ocp, unsigned char **cpp, int compress_cid)
707{
708 printk(KERN_DEBUG "Called IP function on non IP-system: slhc_compress");
709 return -EINVAL;
710}
711
712int
713slhc_remember(struct slcompress *comp, unsigned char *icp, int isize)
714{
715 printk(KERN_DEBUG "Called IP function on non IP-system: slhc_remember");
716 return -EINVAL;
717}
718
719void
720slhc_free(struct slcompress *comp)
721{
722 printk(KERN_DEBUG "Called IP function on non IP-system: slhc_free");
723}
724struct slcompress *
725slhc_init(int rslots, int tslots)
726{
727 printk(KERN_DEBUG "Called IP function on non IP-system: slhc_init");
728 return NULL;
729}
730
731#endif /* CONFIG_INET */
732
733/* VJ header compression */
734EXPORT_SYMBOL(slhc_init);
735EXPORT_SYMBOL(slhc_free);
736EXPORT_SYMBOL(slhc_remember);
737EXPORT_SYMBOL(slhc_compress);
738EXPORT_SYMBOL(slhc_uncompress);
739EXPORT_SYMBOL(slhc_toss);
740
741MODULE_LICENSE("Dual BSD/GPL");