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1 office 1 /**
2 * @file
3 * This is the IPv4 packet segmentation and reassembly implementation.
4 *
5 */
6  
7 /*
8 * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
9 * All rights reserved.
10 *
11 * Redistribution and use in source and binary forms, with or without modification,
12 * are permitted provided that the following conditions are met:
13 *
14 * 1. Redistributions of source code must retain the above copyright notice,
15 * this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright notice,
17 * this list of conditions and the following disclaimer in the documentation
18 * and/or other materials provided with the distribution.
19 * 3. The name of the author may not be used to endorse or promote products
20 * derived from this software without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
23 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
24 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
25 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
26 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
27 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
28 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
29 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
30 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
31 * OF SUCH DAMAGE.
32 *
33 * This file is part of the lwIP TCP/IP stack.
34 *
35 * Author: Jani Monoses <jani@iv.ro>
36 * Simon Goldschmidt
37 * original reassembly code by Adam Dunkels <adam@sics.se>
38 *
39 */
40  
41 #include "lwip/opt.h"
42  
43 #if LWIP_IPV4
44  
45 #include "lwip/ip4_frag.h"
46 #include "lwip/def.h"
47 #include "lwip/inet_chksum.h"
48 #include "lwip/netif.h"
49 #include "lwip/stats.h"
50 #include "lwip/icmp.h"
51  
52 #include <string.h>
53  
54 #if IP_REASSEMBLY
55 /**
56 * The IP reassembly code currently has the following limitations:
57 * - IP header options are not supported
58 * - fragments must not overlap (e.g. due to different routes),
59 * currently, overlapping or duplicate fragments are thrown away
60 * if IP_REASS_CHECK_OVERLAP=1 (the default)!
61 *
62 * @todo: work with IP header options
63 */
64  
65 /** Setting this to 0, you can turn off checking the fragments for overlapping
66 * regions. The code gets a little smaller. Only use this if you know that
67 * overlapping won't occur on your network! */
68 #ifndef IP_REASS_CHECK_OVERLAP
69 #define IP_REASS_CHECK_OVERLAP 1
70 #endif /* IP_REASS_CHECK_OVERLAP */
71  
72 /** Set to 0 to prevent freeing the oldest datagram when the reassembly buffer is
73 * full (IP_REASS_MAX_PBUFS pbufs are enqueued). The code gets a little smaller.
74 * Datagrams will be freed by timeout only. Especially useful when MEMP_NUM_REASSDATA
75 * is set to 1, so one datagram can be reassembled at a time, only. */
76 #ifndef IP_REASS_FREE_OLDEST
77 #define IP_REASS_FREE_OLDEST 1
78 #endif /* IP_REASS_FREE_OLDEST */
79  
80 #define IP_REASS_FLAG_LASTFRAG 0x01
81  
82 #define IP_REASS_VALIDATE_TELEGRAM_FINISHED 1
83 #define IP_REASS_VALIDATE_PBUF_QUEUED 0
84 #define IP_REASS_VALIDATE_PBUF_DROPPED -1
85  
86 /** This is a helper struct which holds the starting
87 * offset and the ending offset of this fragment to
88 * easily chain the fragments.
89 * It has the same packing requirements as the IP header, since it replaces
90 * the IP header in memory in incoming fragments (after copying it) to keep
91 * track of the various fragments. (-> If the IP header doesn't need packing,
92 * this struct doesn't need packing, too.)
93 */
94 #ifdef PACK_STRUCT_USE_INCLUDES
95 # include "arch/bpstruct.h"
96 #endif
97 PACK_STRUCT_BEGIN
98 struct ip_reass_helper {
99 PACK_STRUCT_FIELD(struct pbuf *next_pbuf);
100 PACK_STRUCT_FIELD(u16_t start);
101 PACK_STRUCT_FIELD(u16_t end);
102 } PACK_STRUCT_STRUCT;
103 PACK_STRUCT_END
104 #ifdef PACK_STRUCT_USE_INCLUDES
105 # include "arch/epstruct.h"
106 #endif
107  
108 #define IP_ADDRESSES_AND_ID_MATCH(iphdrA, iphdrB) \
109 (ip4_addr_cmp(&(iphdrA)->src, &(iphdrB)->src) && \
110 ip4_addr_cmp(&(iphdrA)->dest, &(iphdrB)->dest) && \
111 IPH_ID(iphdrA) == IPH_ID(iphdrB)) ? 1 : 0
112  
113 /* global variables */
114 static struct ip_reassdata *reassdatagrams;
115 static u16_t ip_reass_pbufcount;
116  
117 /* function prototypes */
118 static void ip_reass_dequeue_datagram(struct ip_reassdata *ipr, struct ip_reassdata *prev);
119 static int ip_reass_free_complete_datagram(struct ip_reassdata *ipr, struct ip_reassdata *prev);
120  
121 /**
122 * Reassembly timer base function
123 * for both NO_SYS == 0 and 1 (!).
124 *
125 * Should be called every 1000 msec (defined by IP_TMR_INTERVAL).
126 */
127 void
128 ip_reass_tmr(void)
129 {
130 struct ip_reassdata *r, *prev = NULL;
131  
132 r = reassdatagrams;
133 while (r != NULL) {
134 /* Decrement the timer. Once it reaches 0,
135 * clean up the incomplete fragment assembly */
136 if (r->timer > 0) {
137 r->timer--;
138 LWIP_DEBUGF(IP_REASS_DEBUG, ("ip_reass_tmr: timer dec %"U16_F"\n", (u16_t)r->timer));
139 prev = r;
140 r = r->next;
141 } else {
142 /* reassembly timed out */
143 struct ip_reassdata *tmp;
144 LWIP_DEBUGF(IP_REASS_DEBUG, ("ip_reass_tmr: timer timed out\n"));
145 tmp = r;
146 /* get the next pointer before freeing */
147 r = r->next;
148 /* free the helper struct and all enqueued pbufs */
149 ip_reass_free_complete_datagram(tmp, prev);
150 }
151 }
152 }
153  
154 /**
155 * Free a datagram (struct ip_reassdata) and all its pbufs.
156 * Updates the total count of enqueued pbufs (ip_reass_pbufcount),
157 * SNMP counters and sends an ICMP time exceeded packet.
158 *
159 * @param ipr datagram to free
160 * @param prev the previous datagram in the linked list
161 * @return the number of pbufs freed
162 */
163 static int
164 ip_reass_free_complete_datagram(struct ip_reassdata *ipr, struct ip_reassdata *prev)
165 {
166 u16_t pbufs_freed = 0;
167 u16_t clen;
168 struct pbuf *p;
169 struct ip_reass_helper *iprh;
170  
171 LWIP_ASSERT("prev != ipr", prev != ipr);
172 if (prev != NULL) {
173 LWIP_ASSERT("prev->next == ipr", prev->next == ipr);
174 }
175  
176 MIB2_STATS_INC(mib2.ipreasmfails);
177 #if LWIP_ICMP
178 iprh = (struct ip_reass_helper *)ipr->p->payload;
179 if (iprh->start == 0) {
180 /* The first fragment was received, send ICMP time exceeded. */
181 /* First, de-queue the first pbuf from r->p. */
182 p = ipr->p;
183 ipr->p = iprh->next_pbuf;
184 /* Then, copy the original header into it. */
185 SMEMCPY(p->payload, &ipr->iphdr, IP_HLEN);
186 icmp_time_exceeded(p, ICMP_TE_FRAG);
187 clen = pbuf_clen(p);
188 LWIP_ASSERT("pbufs_freed + clen <= 0xffff", pbufs_freed + clen <= 0xffff);
189 pbufs_freed = (u16_t)(pbufs_freed + clen);
190 pbuf_free(p);
191 }
192 #endif /* LWIP_ICMP */
193  
194 /* First, free all received pbufs. The individual pbufs need to be released
195 separately as they have not yet been chained */
196 p = ipr->p;
197 while (p != NULL) {
198 struct pbuf *pcur;
199 iprh = (struct ip_reass_helper *)p->payload;
200 pcur = p;
201 /* get the next pointer before freeing */
202 p = iprh->next_pbuf;
203 clen = pbuf_clen(pcur);
204 LWIP_ASSERT("pbufs_freed + clen <= 0xffff", pbufs_freed + clen <= 0xffff);
205 pbufs_freed = (u16_t)(pbufs_freed + clen);
206 pbuf_free(pcur);
207 }
208 /* Then, unchain the struct ip_reassdata from the list and free it. */
209 ip_reass_dequeue_datagram(ipr, prev);
210 LWIP_ASSERT("ip_reass_pbufcount >= pbufs_freed", ip_reass_pbufcount >= pbufs_freed);
211 ip_reass_pbufcount = (u16_t)(ip_reass_pbufcount - pbufs_freed);
212  
213 return pbufs_freed;
214 }
215  
216 #if IP_REASS_FREE_OLDEST
217 /**
218 * Free the oldest datagram to make room for enqueueing new fragments.
219 * The datagram 'fraghdr' belongs to is not freed!
220 *
221 * @param fraghdr IP header of the current fragment
222 * @param pbufs_needed number of pbufs needed to enqueue
223 * (used for freeing other datagrams if not enough space)
224 * @return the number of pbufs freed
225 */
226 static int
227 ip_reass_remove_oldest_datagram(struct ip_hdr *fraghdr, int pbufs_needed)
228 {
229 /* @todo Can't we simply remove the last datagram in the
230 * linked list behind reassdatagrams?
231 */
232 struct ip_reassdata *r, *oldest, *prev, *oldest_prev;
233 int pbufs_freed = 0, pbufs_freed_current;
234 int other_datagrams;
235  
236 /* Free datagrams until being allowed to enqueue 'pbufs_needed' pbufs,
237 * but don't free the datagram that 'fraghdr' belongs to! */
238 do {
239 oldest = NULL;
240 prev = NULL;
241 oldest_prev = NULL;
242 other_datagrams = 0;
243 r = reassdatagrams;
244 while (r != NULL) {
245 if (!IP_ADDRESSES_AND_ID_MATCH(&r->iphdr, fraghdr)) {
246 /* Not the same datagram as fraghdr */
247 other_datagrams++;
248 if (oldest == NULL) {
249 oldest = r;
250 oldest_prev = prev;
251 } else if (r->timer <= oldest->timer) {
252 /* older than the previous oldest */
253 oldest = r;
254 oldest_prev = prev;
255 }
256 }
257 if (r->next != NULL) {
258 prev = r;
259 }
260 r = r->next;
261 }
262 if (oldest != NULL) {
263 pbufs_freed_current = ip_reass_free_complete_datagram(oldest, oldest_prev);
264 pbufs_freed += pbufs_freed_current;
265 }
266 } while ((pbufs_freed < pbufs_needed) && (other_datagrams > 1));
267 return pbufs_freed;
268 }
269 #endif /* IP_REASS_FREE_OLDEST */
270  
271 /**
272 * Enqueues a new fragment into the fragment queue
273 * @param fraghdr points to the new fragments IP hdr
274 * @param clen number of pbufs needed to enqueue (used for freeing other datagrams if not enough space)
275 * @return A pointer to the queue location into which the fragment was enqueued
276 */
277 static struct ip_reassdata *
278 ip_reass_enqueue_new_datagram(struct ip_hdr *fraghdr, int clen)
279 {
280 struct ip_reassdata *ipr;
281 #if ! IP_REASS_FREE_OLDEST
282 LWIP_UNUSED_ARG(clen);
283 #endif
284  
285 /* No matching previous fragment found, allocate a new reassdata struct */
286 ipr = (struct ip_reassdata *)memp_malloc(MEMP_REASSDATA);
287 if (ipr == NULL) {
288 #if IP_REASS_FREE_OLDEST
289 if (ip_reass_remove_oldest_datagram(fraghdr, clen) >= clen) {
290 ipr = (struct ip_reassdata *)memp_malloc(MEMP_REASSDATA);
291 }
292 if (ipr == NULL)
293 #endif /* IP_REASS_FREE_OLDEST */
294 {
295 IPFRAG_STATS_INC(ip_frag.memerr);
296 LWIP_DEBUGF(IP_REASS_DEBUG, ("Failed to alloc reassdata struct\n"));
297 return NULL;
298 }
299 }
300 memset(ipr, 0, sizeof(struct ip_reassdata));
301 ipr->timer = IP_REASS_MAXAGE;
302  
303 /* enqueue the new structure to the front of the list */
304 ipr->next = reassdatagrams;
305 reassdatagrams = ipr;
306 /* copy the ip header for later tests and input */
307 /* @todo: no ip options supported? */
308 SMEMCPY(&(ipr->iphdr), fraghdr, IP_HLEN);
309 return ipr;
310 }
311  
312 /**
313 * Dequeues a datagram from the datagram queue. Doesn't deallocate the pbufs.
314 * @param ipr points to the queue entry to dequeue
315 */
316 static void
317 ip_reass_dequeue_datagram(struct ip_reassdata *ipr, struct ip_reassdata *prev)
318 {
319 /* dequeue the reass struct */
320 if (reassdatagrams == ipr) {
321 /* it was the first in the list */
322 reassdatagrams = ipr->next;
323 } else {
324 /* it wasn't the first, so it must have a valid 'prev' */
325 LWIP_ASSERT("sanity check linked list", prev != NULL);
326 prev->next = ipr->next;
327 }
328  
329 /* now we can free the ip_reassdata struct */
330 memp_free(MEMP_REASSDATA, ipr);
331 }
332  
333 /**
334 * Chain a new pbuf into the pbuf list that composes the datagram. The pbuf list
335 * will grow over time as new pbufs are rx.
336 * Also checks that the datagram passes basic continuity checks (if the last
337 * fragment was received at least once).
338 * @param ipr points to the reassembly state
339 * @param new_p points to the pbuf for the current fragment
340 * @param is_last is 1 if this pbuf has MF==0 (ipr->flags not updated yet)
341 * @return see IP_REASS_VALIDATE_* defines
342 */
343 static int
344 ip_reass_chain_frag_into_datagram_and_validate(struct ip_reassdata *ipr, struct pbuf *new_p, int is_last)
345 {
346 struct ip_reass_helper *iprh, *iprh_tmp, *iprh_prev = NULL;
347 struct pbuf *q;
348 u16_t offset, len, clen;
349 u8_t hlen;
350 struct ip_hdr *fraghdr;
351 int valid = 1;
352  
353 /* Extract length and fragment offset from current fragment */
354 fraghdr = (struct ip_hdr *)new_p->payload;
355 len = lwip_ntohs(IPH_LEN(fraghdr));
356 hlen = IPH_HL_BYTES(fraghdr);
357 if (hlen > len) {
358 /* invalid datagram */
359 goto freepbuf;
360 }
361 len = (u16_t)(len - hlen);
362 offset = IPH_OFFSET_BYTES(fraghdr);
363  
364 /* overwrite the fragment's ip header from the pbuf with our helper struct,
365 * and setup the embedded helper structure. */
366 /* make sure the struct ip_reass_helper fits into the IP header */
367 LWIP_ASSERT("sizeof(struct ip_reass_helper) <= IP_HLEN",
368 sizeof(struct ip_reass_helper) <= IP_HLEN);
369 iprh = (struct ip_reass_helper *)new_p->payload;
370 iprh->next_pbuf = NULL;
371 iprh->start = offset;
372 iprh->end = (u16_t)(offset + len);
373 if (iprh->end < offset) {
374 /* u16_t overflow, cannot handle this */
375 goto freepbuf;
376 }
377  
378 /* Iterate through until we either get to the end of the list (append),
379 * or we find one with a larger offset (insert). */
380 for (q = ipr->p; q != NULL;) {
381 iprh_tmp = (struct ip_reass_helper *)q->payload;
382 if (iprh->start < iprh_tmp->start) {
383 /* the new pbuf should be inserted before this */
384 iprh->next_pbuf = q;
385 if (iprh_prev != NULL) {
386 /* not the fragment with the lowest offset */
387 #if IP_REASS_CHECK_OVERLAP
388 if ((iprh->start < iprh_prev->end) || (iprh->end > iprh_tmp->start)) {
389 /* fragment overlaps with previous or following, throw away */
390 goto freepbuf;
391 }
392 #endif /* IP_REASS_CHECK_OVERLAP */
393 iprh_prev->next_pbuf = new_p;
394 if (iprh_prev->end != iprh->start) {
395 /* There is a fragment missing between the current
396 * and the previous fragment */
397 valid = 0;
398 }
399 } else {
400 #if IP_REASS_CHECK_OVERLAP
401 if (iprh->end > iprh_tmp->start) {
402 /* fragment overlaps with following, throw away */
403 goto freepbuf;
404 }
405 #endif /* IP_REASS_CHECK_OVERLAP */
406 /* fragment with the lowest offset */
407 ipr->p = new_p;
408 }
409 break;
410 } else if (iprh->start == iprh_tmp->start) {
411 /* received the same datagram twice: no need to keep the datagram */
412 goto freepbuf;
413 #if IP_REASS_CHECK_OVERLAP
414 } else if (iprh->start < iprh_tmp->end) {
415 /* overlap: no need to keep the new datagram */
416 goto freepbuf;
417 #endif /* IP_REASS_CHECK_OVERLAP */
418 } else {
419 /* Check if the fragments received so far have no holes. */
420 if (iprh_prev != NULL) {
421 if (iprh_prev->end != iprh_tmp->start) {
422 /* There is a fragment missing between the current
423 * and the previous fragment */
424 valid = 0;
425 }
426 }
427 }
428 q = iprh_tmp->next_pbuf;
429 iprh_prev = iprh_tmp;
430 }
431  
432 /* If q is NULL, then we made it to the end of the list. Determine what to do now */
433 if (q == NULL) {
434 if (iprh_prev != NULL) {
435 /* this is (for now), the fragment with the highest offset:
436 * chain it to the last fragment */
437 #if IP_REASS_CHECK_OVERLAP
438 LWIP_ASSERT("check fragments don't overlap", iprh_prev->end <= iprh->start);
439 #endif /* IP_REASS_CHECK_OVERLAP */
440 iprh_prev->next_pbuf = new_p;
441 if (iprh_prev->end != iprh->start) {
442 valid = 0;
443 }
444 } else {
445 #if IP_REASS_CHECK_OVERLAP
446 LWIP_ASSERT("no previous fragment, this must be the first fragment!",
447 ipr->p == NULL);
448 #endif /* IP_REASS_CHECK_OVERLAP */
449 /* this is the first fragment we ever received for this ip datagram */
450 ipr->p = new_p;
451 }
452 }
453  
454 /* At this point, the validation part begins: */
455 /* If we already received the last fragment */
456 if (is_last || ((ipr->flags & IP_REASS_FLAG_LASTFRAG) != 0)) {
457 /* and had no holes so far */
458 if (valid) {
459 /* then check if the rest of the fragments is here */
460 /* Check if the queue starts with the first datagram */
461 if ((ipr->p == NULL) || (((struct ip_reass_helper *)ipr->p->payload)->start != 0)) {
462 valid = 0;
463 } else {
464 /* and check that there are no holes after this datagram */
465 iprh_prev = iprh;
466 q = iprh->next_pbuf;
467 while (q != NULL) {
468 iprh = (struct ip_reass_helper *)q->payload;
469 if (iprh_prev->end != iprh->start) {
470 valid = 0;
471 break;
472 }
473 iprh_prev = iprh;
474 q = iprh->next_pbuf;
475 }
476 /* if still valid, all fragments are received
477 * (because to the MF==0 already arrived */
478 if (valid) {
479 LWIP_ASSERT("sanity check", ipr->p != NULL);
480 LWIP_ASSERT("sanity check",
481 ((struct ip_reass_helper *)ipr->p->payload) != iprh);
482 LWIP_ASSERT("validate_datagram:next_pbuf!=NULL",
483 iprh->next_pbuf == NULL);
484 }
485 }
486 }
487 /* If valid is 0 here, there are some fragments missing in the middle
488 * (since MF == 0 has already arrived). Such datagrams simply time out if
489 * no more fragments are received... */
490 return valid ? IP_REASS_VALIDATE_TELEGRAM_FINISHED : IP_REASS_VALIDATE_PBUF_QUEUED;
491 }
492 /* If we come here, not all fragments were received, yet! */
493 return IP_REASS_VALIDATE_PBUF_QUEUED; /* not yet valid! */
494 #if IP_REASS_CHECK_OVERLAP
495 freepbuf:
496 clen = pbuf_clen(new_p);
497 LWIP_ASSERT("ip_reass_pbufcount >= clen", ip_reass_pbufcount >= clen);
498 ip_reass_pbufcount = (u16_t)(ip_reass_pbufcount - clen);
499 pbuf_free(new_p);
500 return IP_REASS_VALIDATE_PBUF_DROPPED;
501 #endif /* IP_REASS_CHECK_OVERLAP */
502 }
503  
504 /**
505 * Reassembles incoming IP fragments into an IP datagram.
506 *
507 * @param p points to a pbuf chain of the fragment
508 * @return NULL if reassembly is incomplete, ? otherwise
509 */
510 struct pbuf *
511 ip4_reass(struct pbuf *p)
512 {
513 struct pbuf *r;
514 struct ip_hdr *fraghdr;
515 struct ip_reassdata *ipr;
516 struct ip_reass_helper *iprh;
517 u16_t offset, len, clen;
518 u8_t hlen;
519 int valid;
520 int is_last;
521  
522 IPFRAG_STATS_INC(ip_frag.recv);
523 MIB2_STATS_INC(mib2.ipreasmreqds);
524  
525 fraghdr = (struct ip_hdr *)p->payload;
526  
527 if ((IPH_HL(fraghdr) * 4) != IP_HLEN) {
528 LWIP_DEBUGF(IP_REASS_DEBUG, ("ip4_reass: IP options currently not supported!\n"));
529 IPFRAG_STATS_INC(ip_frag.err);
530 goto nullreturn;
531 }
532  
533 offset = IPH_OFFSET_BYTES(fraghdr);
534 len = lwip_ntohs(IPH_LEN(fraghdr));
535 hlen = IPH_HL_BYTES(fraghdr);
536 if (hlen > len) {
537 /* invalid datagram */
538 goto nullreturn;
539 }
540 len = (u16_t)(len - hlen);
541  
542 /* Check if we are allowed to enqueue more datagrams. */
543 clen = pbuf_clen(p);
544 if ((ip_reass_pbufcount + clen) > IP_REASS_MAX_PBUFS) {
545 #if IP_REASS_FREE_OLDEST
546 if (!ip_reass_remove_oldest_datagram(fraghdr, clen) ||
547 ((ip_reass_pbufcount + clen) > IP_REASS_MAX_PBUFS))
548 #endif /* IP_REASS_FREE_OLDEST */
549 {
550 /* No datagram could be freed and still too many pbufs enqueued */
551 LWIP_DEBUGF(IP_REASS_DEBUG, ("ip4_reass: Overflow condition: pbufct=%d, clen=%d, MAX=%d\n",
552 ip_reass_pbufcount, clen, IP_REASS_MAX_PBUFS));
553 IPFRAG_STATS_INC(ip_frag.memerr);
554 /* @todo: send ICMP time exceeded here? */
555 /* drop this pbuf */
556 goto nullreturn;
557 }
558 }
559  
560 /* Look for the datagram the fragment belongs to in the current datagram queue,
561 * remembering the previous in the queue for later dequeueing. */
562 for (ipr = reassdatagrams; ipr != NULL; ipr = ipr->next) {
563 /* Check if the incoming fragment matches the one currently present
564 in the reassembly buffer. If so, we proceed with copying the
565 fragment into the buffer. */
566 if (IP_ADDRESSES_AND_ID_MATCH(&ipr->iphdr, fraghdr)) {
567 LWIP_DEBUGF(IP_REASS_DEBUG, ("ip4_reass: matching previous fragment ID=%"X16_F"\n",
568 lwip_ntohs(IPH_ID(fraghdr))));
569 IPFRAG_STATS_INC(ip_frag.cachehit);
570 break;
571 }
572 }
573  
574 if (ipr == NULL) {
575 /* Enqueue a new datagram into the datagram queue */
576 ipr = ip_reass_enqueue_new_datagram(fraghdr, clen);
577 /* Bail if unable to enqueue */
578 if (ipr == NULL) {
579 goto nullreturn;
580 }
581 } else {
582 if (((lwip_ntohs(IPH_OFFSET(fraghdr)) & IP_OFFMASK) == 0) &&
583 ((lwip_ntohs(IPH_OFFSET(&ipr->iphdr)) & IP_OFFMASK) != 0)) {
584 /* ipr->iphdr is not the header from the first fragment, but fraghdr is
585 * -> copy fraghdr into ipr->iphdr since we want to have the header
586 * of the first fragment (for ICMP time exceeded and later, for copying
587 * all options, if supported)*/
588 SMEMCPY(&ipr->iphdr, fraghdr, IP_HLEN);
589 }
590 }
591  
592 /* At this point, we have either created a new entry or pointing
593 * to an existing one */
594  
595 /* check for 'no more fragments', and update queue entry*/
596 is_last = (IPH_OFFSET(fraghdr) & PP_NTOHS(IP_MF)) == 0;
597 if (is_last) {
598 u16_t datagram_len = (u16_t)(offset + len);
599 if ((datagram_len < offset) || (datagram_len > (0xFFFF - IP_HLEN))) {
600 /* u16_t overflow, cannot handle this */
601 goto nullreturn;
602 }
603 }
604 /* find the right place to insert this pbuf */
605 /* @todo: trim pbufs if fragments are overlapping */
606 valid = ip_reass_chain_frag_into_datagram_and_validate(ipr, p, is_last);
607 if (valid == IP_REASS_VALIDATE_PBUF_DROPPED) {
608 goto nullreturn;
609 }
610 /* if we come here, the pbuf has been enqueued */
611  
612 /* Track the current number of pbufs current 'in-flight', in order to limit
613 the number of fragments that may be enqueued at any one time
614 (overflow checked by testing against IP_REASS_MAX_PBUFS) */
615 ip_reass_pbufcount = (u16_t)(ip_reass_pbufcount + clen);
616 if (is_last) {
617 u16_t datagram_len = (u16_t)(offset + len);
618 ipr->datagram_len = datagram_len;
619 ipr->flags |= IP_REASS_FLAG_LASTFRAG;
620 LWIP_DEBUGF(IP_REASS_DEBUG,
621 ("ip4_reass: last fragment seen, total len %"S16_F"\n",
622 ipr->datagram_len));
623 }
624  
625 if (valid == IP_REASS_VALIDATE_TELEGRAM_FINISHED) {
626 struct ip_reassdata *ipr_prev;
627 /* the totally last fragment (flag more fragments = 0) was received at least
628 * once AND all fragments are received */
629 u16_t datagram_len = (u16_t)(ipr->datagram_len + IP_HLEN);
630  
631 /* save the second pbuf before copying the header over the pointer */
632 r = ((struct ip_reass_helper *)ipr->p->payload)->next_pbuf;
633  
634 /* copy the original ip header back to the first pbuf */
635 fraghdr = (struct ip_hdr *)(ipr->p->payload);
636 SMEMCPY(fraghdr, &ipr->iphdr, IP_HLEN);
637 IPH_LEN_SET(fraghdr, lwip_htons(datagram_len));
638 IPH_OFFSET_SET(fraghdr, 0);
639 IPH_CHKSUM_SET(fraghdr, 0);
640 /* @todo: do we need to set/calculate the correct checksum? */
641 #if CHECKSUM_GEN_IP
642 IF__NETIF_CHECKSUM_ENABLED(ip_current_input_netif(), NETIF_CHECKSUM_GEN_IP) {
643 IPH_CHKSUM_SET(fraghdr, inet_chksum(fraghdr, IP_HLEN));
644 }
645 #endif /* CHECKSUM_GEN_IP */
646  
647 p = ipr->p;
648  
649 /* chain together the pbufs contained within the reass_data list. */
650 while (r != NULL) {
651 iprh = (struct ip_reass_helper *)r->payload;
652  
653 /* hide the ip header for every succeeding fragment */
654 pbuf_remove_header(r, IP_HLEN);
655 pbuf_cat(p, r);
656 r = iprh->next_pbuf;
657 }
658  
659 /* find the previous entry in the linked list */
660 if (ipr == reassdatagrams) {
661 ipr_prev = NULL;
662 } else {
663 for (ipr_prev = reassdatagrams; ipr_prev != NULL; ipr_prev = ipr_prev->next) {
664 if (ipr_prev->next == ipr) {
665 break;
666 }
667 }
668 }
669  
670 /* release the sources allocate for the fragment queue entry */
671 ip_reass_dequeue_datagram(ipr, ipr_prev);
672  
673 /* and adjust the number of pbufs currently queued for reassembly. */
674 clen = pbuf_clen(p);
675 LWIP_ASSERT("ip_reass_pbufcount >= clen", ip_reass_pbufcount >= clen);
676 ip_reass_pbufcount = (u16_t)(ip_reass_pbufcount - clen);
677  
678 MIB2_STATS_INC(mib2.ipreasmoks);
679  
680 /* Return the pbuf chain */
681 return p;
682 }
683 /* the datagram is not (yet?) reassembled completely */
684 LWIP_DEBUGF(IP_REASS_DEBUG, ("ip_reass_pbufcount: %d out\n", ip_reass_pbufcount));
685 return NULL;
686  
687 nullreturn:
688 LWIP_DEBUGF(IP_REASS_DEBUG, ("ip4_reass: nullreturn\n"));
689 IPFRAG_STATS_INC(ip_frag.drop);
690 pbuf_free(p);
691 return NULL;
692 }
693 #endif /* IP_REASSEMBLY */
694  
695 #if IP_FRAG
696 #if !LWIP_NETIF_TX_SINGLE_PBUF
697 /** Allocate a new struct pbuf_custom_ref */
698 static struct pbuf_custom_ref *
699 ip_frag_alloc_pbuf_custom_ref(void)
700 {
701 return (struct pbuf_custom_ref *)memp_malloc(MEMP_FRAG_PBUF);
702 }
703  
704 /** Free a struct pbuf_custom_ref */
705 static void
706 ip_frag_free_pbuf_custom_ref(struct pbuf_custom_ref *p)
707 {
708 LWIP_ASSERT("p != NULL", p != NULL);
709 memp_free(MEMP_FRAG_PBUF, p);
710 }
711  
712 /** Free-callback function to free a 'struct pbuf_custom_ref', called by
713 * pbuf_free. */
714 static void
715 ipfrag_free_pbuf_custom(struct pbuf *p)
716 {
717 struct pbuf_custom_ref *pcr = (struct pbuf_custom_ref *)p;
718 LWIP_ASSERT("pcr != NULL", pcr != NULL);
719 LWIP_ASSERT("pcr == p", (void *)pcr == (void *)p);
720 if (pcr->original != NULL) {
721 pbuf_free(pcr->original);
722 }
723 ip_frag_free_pbuf_custom_ref(pcr);
724 }
725 #endif /* !LWIP_NETIF_TX_SINGLE_PBUF */
726  
727 /**
728 * Fragment an IP datagram if too large for the netif.
729 *
730 * Chop the datagram in MTU sized chunks and send them in order
731 * by pointing PBUF_REFs into p.
732 *
733 * @param p ip packet to send
734 * @param netif the netif on which to send
735 * @param dest destination ip address to which to send
736 *
737 * @return ERR_OK if sent successfully, err_t otherwise
738 */
739 err_t
740 ip4_frag(struct pbuf *p, struct netif *netif, const ip4_addr_t *dest)
741 {
742 struct pbuf *rambuf;
743 #if !LWIP_NETIF_TX_SINGLE_PBUF
744 struct pbuf *newpbuf;
745 u16_t newpbuflen = 0;
746 u16_t left_to_copy;
747 #endif
748 struct ip_hdr *original_iphdr;
749 struct ip_hdr *iphdr;
750 const u16_t nfb = (u16_t)((netif->mtu - IP_HLEN) / 8);
751 u16_t left, fragsize;
752 u16_t ofo;
753 int last;
754 u16_t poff = IP_HLEN;
755 u16_t tmp;
756  
757 original_iphdr = (struct ip_hdr *)p->payload;
758 iphdr = original_iphdr;
759 LWIP_ERROR("ip4_frag() does not support IP options", IPH_HL_BYTES(iphdr) == IP_HLEN, return ERR_VAL);
760 LWIP_ERROR("ip4_frag(): pbuf too short", p->len >= IP_HLEN, return ERR_VAL);
761  
762 /* Save original offset */
763 tmp = lwip_ntohs(IPH_OFFSET(iphdr));
764 ofo = tmp & IP_OFFMASK;
765 LWIP_ERROR("ip_frag(): MF already set", (tmp & IP_MF) == 0, return ERR_VAL);
766  
767 left = (u16_t)(p->tot_len - IP_HLEN);
768  
769 while (left) {
770 /* Fill this fragment */
771 fragsize = LWIP_MIN(left, (u16_t)(nfb * 8));
772  
773 #if LWIP_NETIF_TX_SINGLE_PBUF
774 rambuf = pbuf_alloc(PBUF_IP, fragsize, PBUF_RAM);
775 if (rambuf == NULL) {
776 goto memerr;
777 }
778 LWIP_ASSERT("this needs a pbuf in one piece!",
779 (rambuf->len == rambuf->tot_len) && (rambuf->next == NULL));
780 poff += pbuf_copy_partial(p, rambuf->payload, fragsize, poff);
781 /* make room for the IP header */
782 if (pbuf_add_header(rambuf, IP_HLEN)) {
783 pbuf_free(rambuf);
784 goto memerr;
785 }
786 /* fill in the IP header */
787 SMEMCPY(rambuf->payload, original_iphdr, IP_HLEN);
788 iphdr = (struct ip_hdr *)rambuf->payload;
789 #else /* LWIP_NETIF_TX_SINGLE_PBUF */
790 /* When not using a static buffer, create a chain of pbufs.
791 * The first will be a PBUF_RAM holding the link and IP header.
792 * The rest will be PBUF_REFs mirroring the pbuf chain to be fragged,
793 * but limited to the size of an mtu.
794 */
795 rambuf = pbuf_alloc(PBUF_LINK, IP_HLEN, PBUF_RAM);
796 if (rambuf == NULL) {
797 goto memerr;
798 }
799 LWIP_ASSERT("this needs a pbuf in one piece!",
800 (p->len >= (IP_HLEN)));
801 SMEMCPY(rambuf->payload, original_iphdr, IP_HLEN);
802 iphdr = (struct ip_hdr *)rambuf->payload;
803  
804 left_to_copy = fragsize;
805 while (left_to_copy) {
806 struct pbuf_custom_ref *pcr;
807 u16_t plen = (u16_t)(p->len - poff);
808 LWIP_ASSERT("p->len >= poff", p->len >= poff);
809 newpbuflen = LWIP_MIN(left_to_copy, plen);
810 /* Is this pbuf already empty? */
811 if (!newpbuflen) {
812 poff = 0;
813 p = p->next;
814 continue;
815 }
816 pcr = ip_frag_alloc_pbuf_custom_ref();
817 if (pcr == NULL) {
818 pbuf_free(rambuf);
819 goto memerr;
820 }
821 /* Mirror this pbuf, although we might not need all of it. */
822 newpbuf = pbuf_alloced_custom(PBUF_RAW, newpbuflen, PBUF_REF, &pcr->pc,
823 (u8_t *)p->payload + poff, newpbuflen);
824 if (newpbuf == NULL) {
825 ip_frag_free_pbuf_custom_ref(pcr);
826 pbuf_free(rambuf);
827 goto memerr;
828 }
829 pbuf_ref(p);
830 pcr->original = p;
831 pcr->pc.custom_free_function = ipfrag_free_pbuf_custom;
832  
833 /* Add it to end of rambuf's chain, but using pbuf_cat, not pbuf_chain
834 * so that it is removed when pbuf_dechain is later called on rambuf.
835 */
836 pbuf_cat(rambuf, newpbuf);
837 left_to_copy = (u16_t)(left_to_copy - newpbuflen);
838 if (left_to_copy) {
839 poff = 0;
840 p = p->next;
841 }
842 }
843 poff = (u16_t)(poff + newpbuflen);
844 #endif /* LWIP_NETIF_TX_SINGLE_PBUF */
845  
846 /* Correct header */
847 last = (left <= netif->mtu - IP_HLEN);
848  
849 /* Set new offset and MF flag */
850 tmp = (IP_OFFMASK & (ofo));
851 if (!last) {
852 tmp = tmp | IP_MF;
853 }
854 IPH_OFFSET_SET(iphdr, lwip_htons(tmp));
855 IPH_LEN_SET(iphdr, lwip_htons((u16_t)(fragsize + IP_HLEN)));
856 IPH_CHKSUM_SET(iphdr, 0);
857 #if CHECKSUM_GEN_IP
858 IF__NETIF_CHECKSUM_ENABLED(netif, NETIF_CHECKSUM_GEN_IP) {
859 IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, IP_HLEN));
860 }
861 #endif /* CHECKSUM_GEN_IP */
862  
863 /* No need for separate header pbuf - we allowed room for it in rambuf
864 * when allocated.
865 */
866 netif->output(netif, rambuf, dest);
867 IPFRAG_STATS_INC(ip_frag.xmit);
868  
869 /* Unfortunately we can't reuse rambuf - the hardware may still be
870 * using the buffer. Instead we free it (and the ensuing chain) and
871 * recreate it next time round the loop. If we're lucky the hardware
872 * will have already sent the packet, the free will really free, and
873 * there will be zero memory penalty.
874 */
875  
876 pbuf_free(rambuf);
877 left = (u16_t)(left - fragsize);
878 ofo = (u16_t)(ofo + nfb);
879 }
880 MIB2_STATS_INC(mib2.ipfragoks);
881 return ERR_OK;
882 memerr:
883 MIB2_STATS_INC(mib2.ipfragfails);
884 return ERR_MEM;
885 }
886 #endif /* IP_FRAG */
887  
888 #endif /* LWIP_IPV4 */