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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 short i;
95 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 ( IS_ERR_OR_NULL(comp) )
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 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 struct cstate *ocs = &(comp->tstate[comp->xmit_oldest]);
231 struct cstate *lcs = ocs;
232 struct cstate *cs = lcs->next;
233 unsigned long deltaS, deltaA;
234 short changes = 0;
235 int nlen, hlen;
236 unsigned char new_seq[16];
237 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 if (ip->version != 4 || ip->ihl < 5)
252 return isize;
253
254 /* Bail if this packet isn't TCP, or is an IP fragment */
255 if (ip->protocol != IPPROTO_TCP || (ntohs(ip->frag_off) & 0x3fff)) {
256 /* Send as regular IP */
257 if(ip->protocol != IPPROTO_TCP)
258 comp->sls_o_nontcp++;
259 else
260 comp->sls_o_tcp++;
261 return isize;
262 }
263 nlen = ip->ihl * 4;
264 if (isize < nlen + sizeof(*th))
265 return isize;
266
267 th = (struct tcphdr *)(icp + nlen);
268 if (th->doff < sizeof(struct tcphdr) / 4)
269 return isize;
270 hlen = nlen + th->doff * 4;
271
272 /* Bail if the TCP packet isn't `compressible' (i.e., ACK isn't set or
273 * some other control bit is set). Also uncompressible if
274 * it's a runt.
275 */
276 if(hlen > isize || th->syn || th->fin || th->rst ||
277 ! (th->ack)){
278 /* TCP connection stuff; send as regular IP */
279 comp->sls_o_tcp++;
280 return isize;
281 }
282 /*
283 * Packet is compressible -- we're going to send either a
284 * COMPRESSED_TCP or UNCOMPRESSED_TCP packet. Either way,
285 * we need to locate (or create) the connection state.
286 *
287 * States are kept in a circularly linked list with
288 * xmit_oldest pointing to the end of the list. The
289 * list is kept in lru order by moving a state to the
290 * head of the list whenever it is referenced. Since
291 * the list is short and, empirically, the connection
292 * we want is almost always near the front, we locate
293 * states via linear search. If we don't find a state
294 * for the datagram, the oldest state is (re-)used.
295 */
296 for ( ; ; ) {
297 if( ip->saddr == cs->cs_ip.saddr
298 && ip->daddr == cs->cs_ip.daddr
299 && th->source == cs->cs_tcp.source
300 && th->dest == cs->cs_tcp.dest)
301 goto found;
302
303 /* if current equal oldest, at end of list */
304 if ( cs == ocs )
305 break;
306 lcs = cs;
307 cs = cs->next;
308 comp->sls_o_searches++;
309 }
310 /*
311 * Didn't find it -- re-use oldest cstate. Send an
312 * uncompressed packet that tells the other side what
313 * connection number we're using for this conversation.
314 *
315 * Note that since the state list is circular, the oldest
316 * state points to the newest and we only need to set
317 * xmit_oldest to update the lru linkage.
318 */
319 comp->sls_o_misses++;
320 comp->xmit_oldest = lcs->cs_this;
321 goto uncompressed;
322
323found:
324 /*
325 * Found it -- move to the front on the connection list.
326 */
327 if(lcs == ocs) {
328 /* found at most recently used */
329 } else if (cs == ocs) {
330 /* found at least recently used */
331 comp->xmit_oldest = lcs->cs_this;
332 } else {
333 /* more than 2 elements */
334 lcs->next = cs->next;
335 cs->next = ocs->next;
336 ocs->next = cs;
337 }
338
339 /*
340 * Make sure that only what we expect to change changed.
341 * Check the following:
342 * IP protocol version, header length & type of service.
343 * The "Don't fragment" bit.
344 * The time-to-live field.
345 * The TCP header length.
346 * IP options, if any.
347 * TCP options, if any.
348 * If any of these things are different between the previous &
349 * current datagram, we send the current datagram `uncompressed'.
350 */
351 oth = &cs->cs_tcp;
352
353 if(ip->version != cs->cs_ip.version || ip->ihl != cs->cs_ip.ihl
354 || ip->tos != cs->cs_ip.tos
355 || (ip->frag_off & htons(0x4000)) != (cs->cs_ip.frag_off & htons(0x4000))
356 || ip->ttl != cs->cs_ip.ttl
357 || th->doff != cs->cs_tcp.doff
358 || (ip->ihl > 5 && memcmp(ip+1,cs->cs_ipopt,((ip->ihl)-5)*4) != 0)
359 || (th->doff > 5 && memcmp(th+1,cs->cs_tcpopt,((th->doff)-5)*4) != 0)){
360 goto uncompressed;
361 }
362
363 /*
364 * Figure out which of the changing fields changed. The
365 * receiver expects changes in the order: urgent, window,
366 * ack, seq (the order minimizes the number of temporaries
367 * needed in this section of code).
368 */
369 if(th->urg){
370 deltaS = ntohs(th->urg_ptr);
371 cp = encode(cp,deltaS);
372 changes |= NEW_U;
373 } else if(th->urg_ptr != oth->urg_ptr){
374 /* argh! URG not set but urp changed -- a sensible
375 * implementation should never do this but RFC793
376 * doesn't prohibit the change so we have to deal
377 * with it. */
378 goto uncompressed;
379 }
380 if((deltaS = ntohs(th->window) - ntohs(oth->window)) != 0){
381 cp = encode(cp,deltaS);
382 changes |= NEW_W;
383 }
384 if((deltaA = ntohl(th->ack_seq) - ntohl(oth->ack_seq)) != 0L){
385 if(deltaA > 0x0000ffff)
386 goto uncompressed;
387 cp = encode(cp,deltaA);
388 changes |= NEW_A;
389 }
390 if((deltaS = ntohl(th->seq) - ntohl(oth->seq)) != 0L){
391 if(deltaS > 0x0000ffff)
392 goto uncompressed;
393 cp = encode(cp,deltaS);
394 changes |= NEW_S;
395 }
396
397 switch(changes){
398 case 0: /* Nothing changed. If this packet contains data and the
399 * last one didn't, this is probably a data packet following
400 * an ack (normal on an interactive connection) and we send
401 * it compressed. Otherwise it's probably a retransmit,
402 * retransmitted ack or window probe. Send it uncompressed
403 * in case the other side missed the compressed version.
404 */
405 if(ip->tot_len != cs->cs_ip.tot_len &&
406 ntohs(cs->cs_ip.tot_len) == hlen)
407 break;
408 goto uncompressed;
409 case SPECIAL_I:
410 case SPECIAL_D:
411 /* actual changes match one of our special case encodings --
412 * send packet uncompressed.
413 */
414 goto uncompressed;
415 case NEW_S|NEW_A:
416 if(deltaS == deltaA &&
417 deltaS == ntohs(cs->cs_ip.tot_len) - hlen){
418 /* special case for echoed terminal traffic */
419 changes = SPECIAL_I;
420 cp = new_seq;
421 }
422 break;
423 case NEW_S:
424 if(deltaS == ntohs(cs->cs_ip.tot_len) - hlen){
425 /* special case for data xfer */
426 changes = SPECIAL_D;
427 cp = new_seq;
428 }
429 break;
430 }
431 deltaS = ntohs(ip->id) - ntohs(cs->cs_ip.id);
432 if(deltaS != 1){
433 cp = encode(cp,deltaS);
434 changes |= NEW_I;
435 }
436 if(th->psh)
437 changes |= TCP_PUSH_BIT;
438 /* Grab the cksum before we overwrite it below. Then update our
439 * state with this packet's header.
440 */
441 csum = th->check;
442 memcpy(&cs->cs_ip,ip,20);
443 memcpy(&cs->cs_tcp,th,20);
444 /* We want to use the original packet as our compressed packet.
445 * (cp - new_seq) is the number of bytes we need for compressed
446 * sequence numbers. In addition we need one byte for the change
447 * mask, one for the connection id and two for the tcp checksum.
448 * So, (cp - new_seq) + 4 bytes of header are needed.
449 */
450 deltaS = cp - new_seq;
451 if(compress_cid == 0 || comp->xmit_current != cs->cs_this){
452 cp = ocp;
453 *cpp = ocp;
454 *cp++ = changes | NEW_C;
455 *cp++ = cs->cs_this;
456 comp->xmit_current = cs->cs_this;
457 } else {
458 cp = ocp;
459 *cpp = ocp;
460 *cp++ = changes;
461 }
462 *(__sum16 *)cp = csum;
463 cp += 2;
464/* deltaS is now the size of the change section of the compressed header */
465 memcpy(cp,new_seq,deltaS); /* Write list of deltas */
466 memcpy(cp+deltaS,icp+hlen,isize-hlen);
467 comp->sls_o_compressed++;
468 ocp[0] |= SL_TYPE_COMPRESSED_TCP;
469 return isize - hlen + deltaS + (cp - ocp);
470
471 /* Update connection state cs & send uncompressed packet (i.e.,
472 * a regular ip/tcp packet but with the 'conversation id' we hope
473 * to use on future compressed packets in the protocol field).
474 */
475uncompressed:
476 memcpy(&cs->cs_ip,ip,20);
477 memcpy(&cs->cs_tcp,th,20);
478 if (ip->ihl > 5)
479 memcpy(cs->cs_ipopt, ip+1, ((ip->ihl) - 5) * 4);
480 if (th->doff > 5)
481 memcpy(cs->cs_tcpopt, th+1, ((th->doff) - 5) * 4);
482 comp->xmit_current = cs->cs_this;
483 comp->sls_o_uncompressed++;
484 memcpy(ocp, icp, isize);
485 *cpp = ocp;
486 ocp[9] = cs->cs_this;
487 ocp[0] |= SL_TYPE_UNCOMPRESSED_TCP;
488 return isize;
489}
490
491
492int
493slhc_uncompress(struct slcompress *comp, unsigned char *icp, int isize)
494{
495 int changes;
496 long x;
497 struct tcphdr *thp;
498 struct iphdr *ip;
499 struct cstate *cs;
500 int len, hdrlen;
501 unsigned char *cp = icp;
502
503 /* We've got a compressed packet; read the change byte */
504 comp->sls_i_compressed++;
505 if(isize < 3){
506 comp->sls_i_error++;
507 return 0;
508 }
509 changes = *cp++;
510 if(changes & NEW_C){
511 /* Make sure the state index is in range, then grab the state.
512 * If we have a good state index, clear the 'discard' flag.
513 */
514 x = *cp++; /* Read conn index */
515 if(x < 0 || x > comp->rslot_limit)
516 goto bad;
517
518 /* Check if the cstate is initialized */
519 if (!comp->rstate[x].initialized)
520 goto bad;
521
522 comp->flags &=~ SLF_TOSS;
523 comp->recv_current = x;
524 } else {
525 /* this packet has an implicit state index. If we've
526 * had a line error since the last time we got an
527 * explicit state index, we have to toss the packet. */
528 if(comp->flags & SLF_TOSS){
529 comp->sls_i_tossed++;
530 return 0;
531 }
532 }
533 cs = &comp->rstate[comp->recv_current];
534 thp = &cs->cs_tcp;
535 ip = &cs->cs_ip;
536
537 thp->check = *(__sum16 *)cp;
538 cp += 2;
539
540 thp->psh = (changes & TCP_PUSH_BIT) ? 1 : 0;
541/*
542 * we can use the same number for the length of the saved header and
543 * the current one, because the packet wouldn't have been sent
544 * as compressed unless the options were the same as the previous one
545 */
546
547 hdrlen = ip->ihl * 4 + thp->doff * 4;
548
549 switch(changes & SPECIALS_MASK){
550 case SPECIAL_I: /* Echoed terminal traffic */
551 {
552 short i;
553 i = ntohs(ip->tot_len) - hdrlen;
554 thp->ack_seq = htonl( ntohl(thp->ack_seq) + i);
555 thp->seq = htonl( ntohl(thp->seq) + i);
556 }
557 break;
558
559 case SPECIAL_D: /* Unidirectional data */
560 thp->seq = htonl( ntohl(thp->seq) +
561 ntohs(ip->tot_len) - hdrlen);
562 break;
563
564 default:
565 if(changes & NEW_U){
566 thp->urg = 1;
567 if((x = decode(&cp)) == -1) {
568 goto bad;
569 }
570 thp->urg_ptr = htons(x);
571 } else
572 thp->urg = 0;
573 if(changes & NEW_W){
574 if((x = decode(&cp)) == -1) {
575 goto bad;
576 }
577 thp->window = htons( ntohs(thp->window) + x);
578 }
579 if(changes & NEW_A){
580 if((x = decode(&cp)) == -1) {
581 goto bad;
582 }
583 thp->ack_seq = htonl( ntohl(thp->ack_seq) + x);
584 }
585 if(changes & NEW_S){
586 if((x = decode(&cp)) == -1) {
587 goto bad;
588 }
589 thp->seq = htonl( ntohl(thp->seq) + x);
590 }
591 break;
592 }
593 if(changes & NEW_I){
594 if((x = decode(&cp)) == -1) {
595 goto bad;
596 }
597 ip->id = htons (ntohs (ip->id) + x);
598 } else
599 ip->id = htons (ntohs (ip->id) + 1);
600
601 /*
602 * At this point, cp points to the first byte of data in the
603 * packet. Put the reconstructed TCP and IP headers back on the
604 * packet. Recalculate IP checksum (but not TCP checksum).
605 */
606
607 len = isize - (cp - icp);
608 if (len < 0)
609 goto bad;
610 len += hdrlen;
611 ip->tot_len = htons(len);
612 ip->check = 0;
613
614 memmove(icp + hdrlen, cp, len - hdrlen);
615
616 cp = icp;
617 memcpy(cp, ip, 20);
618 cp += 20;
619
620 if (ip->ihl > 5) {
621 memcpy(cp, cs->cs_ipopt, (ip->ihl - 5) * 4);
622 cp += (ip->ihl - 5) * 4;
623 }
624
625 put_unaligned(ip_fast_csum(icp, ip->ihl),
626 &((struct iphdr *)icp)->check);
627
628 memcpy(cp, thp, 20);
629 cp += 20;
630
631 if (thp->doff > 5) {
632 memcpy(cp, cs->cs_tcpopt, ((thp->doff) - 5) * 4);
633 cp += ((thp->doff) - 5) * 4;
634 }
635
636 return len;
637bad:
638 comp->sls_i_error++;
639 return slhc_toss( comp );
640}
641
642
643int
644slhc_remember(struct slcompress *comp, unsigned char *icp, int isize)
645{
646 struct cstate *cs;
647 unsigned ihl;
648
649 unsigned char index;
650
651 if(isize < 20) {
652 /* The packet is shorter than a legal IP header */
653 comp->sls_i_runt++;
654 return slhc_toss( comp );
655 }
656 /* Peek at the IP header's IHL field to find its length */
657 ihl = icp[0] & 0xf;
658 if(ihl < 20 / 4){
659 /* The IP header length field is too small */
660 comp->sls_i_runt++;
661 return slhc_toss( comp );
662 }
663 index = icp[9];
664 icp[9] = IPPROTO_TCP;
665
666 if (ip_fast_csum(icp, ihl)) {
667 /* Bad IP header checksum; discard */
668 comp->sls_i_badcheck++;
669 return slhc_toss( comp );
670 }
671 if(index > comp->rslot_limit) {
672 comp->sls_i_error++;
673 return slhc_toss(comp);
674 }
675
676 /* Update local state */
677 cs = &comp->rstate[comp->recv_current = index];
678 comp->flags &=~ SLF_TOSS;
679 memcpy(&cs->cs_ip,icp,20);
680 memcpy(&cs->cs_tcp,icp + ihl*4,20);
681 if (ihl > 5)
682 memcpy(cs->cs_ipopt, icp + sizeof(struct iphdr), (ihl - 5) * 4);
683 if (cs->cs_tcp.doff > 5)
684 memcpy(cs->cs_tcpopt, icp + ihl*4 + sizeof(struct tcphdr), (cs->cs_tcp.doff - 5) * 4);
685 cs->cs_hsize = ihl*2 + cs->cs_tcp.doff*2;
686 cs->initialized = true;
687 /* Put headers back on packet
688 * Neither header checksum is recalculated
689 */
690 comp->sls_i_uncompressed++;
691 return isize;
692}
693
694int
695slhc_toss(struct slcompress *comp)
696{
697 if ( comp == NULLSLCOMPR )
698 return 0;
699
700 comp->flags |= SLF_TOSS;
701 return 0;
702}
703
704#else /* CONFIG_INET */
705
706int
707slhc_toss(struct slcompress *comp)
708{
709 printk(KERN_DEBUG "Called IP function on non IP-system: slhc_toss");
710 return -EINVAL;
711}
712int
713slhc_uncompress(struct slcompress *comp, unsigned char *icp, int isize)
714{
715 printk(KERN_DEBUG "Called IP function on non IP-system: slhc_uncompress");
716 return -EINVAL;
717}
718int
719slhc_compress(struct slcompress *comp, unsigned char *icp, int isize,
720 unsigned char *ocp, unsigned char **cpp, int compress_cid)
721{
722 printk(KERN_DEBUG "Called IP function on non IP-system: slhc_compress");
723 return -EINVAL;
724}
725
726int
727slhc_remember(struct slcompress *comp, unsigned char *icp, int isize)
728{
729 printk(KERN_DEBUG "Called IP function on non IP-system: slhc_remember");
730 return -EINVAL;
731}
732
733void
734slhc_free(struct slcompress *comp)
735{
736 printk(KERN_DEBUG "Called IP function on non IP-system: slhc_free");
737}
738struct slcompress *
739slhc_init(int rslots, int tslots)
740{
741 printk(KERN_DEBUG "Called IP function on non IP-system: slhc_init");
742 return NULL;
743}
744
745#endif /* CONFIG_INET */
746
747/* VJ header compression */
748EXPORT_SYMBOL(slhc_init);
749EXPORT_SYMBOL(slhc_free);
750EXPORT_SYMBOL(slhc_remember);
751EXPORT_SYMBOL(slhc_compress);
752EXPORT_SYMBOL(slhc_uncompress);
753EXPORT_SYMBOL(slhc_toss);
754
755MODULE_DESCRIPTION("Compression helpers for SLIP (serial line)");
756MODULE_LICENSE("Dual BSD/GPL");