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ip_frag.c
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00001 /** 00002 * @file 00003 * This is the IPv4 packet segmentation and reassembly implementation. 00004 * 00005 */ 00006 00007 /* 00008 * Copyright (c) 2001-2004 Swedish Institute of Computer Science. 00009 * All rights reserved. 00010 * 00011 * Redistribution and use in source and binary forms, with or without modification, 00012 * are permitted provided that the following conditions are met: 00013 * 00014 * 1. Redistributions of source code must retain the above copyright notice, 00015 * this list of conditions and the following disclaimer. 00016 * 2. Redistributions in binary form must reproduce the above copyright notice, 00017 * this list of conditions and the following disclaimer in the documentation 00018 * and/or other materials provided with the distribution. 00019 * 3. The name of the author may not be used to endorse or promote products 00020 * derived from this software without specific prior written permission. 00021 * 00022 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED 00023 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 00024 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT 00025 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 00026 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT 00027 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 00028 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 00029 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING 00030 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY 00031 * OF SUCH DAMAGE. 00032 * 00033 * This file is part of the lwIP TCP/IP stack. 00034 * 00035 * Author: Jani Monoses <jani@iv.ro> 00036 * Simon Goldschmidt 00037 * original reassembly code by Adam Dunkels <adam@sics.se> 00038 * 00039 */ 00040 00041 #include "lwip/opt.h" 00042 #include "lwip/ip_frag.h" 00043 #include "lwip/def.h" 00044 #include "lwip/inet_chksum.h" 00045 #include "lwip/netif.h" 00046 #include "lwip/snmp.h" 00047 #include "lwip/stats.h" 00048 #include "lwip/icmp.h" 00049 00050 #include <string.h> 00051 00052 #if IP_REASSEMBLY 00053 /** 00054 * The IP reassembly code currently has the following limitations: 00055 * - IP header options are not supported 00056 * - fragments must not overlap (e.g. due to different routes), 00057 * currently, overlapping or duplicate fragments are thrown away 00058 * if IP_REASS_CHECK_OVERLAP=1 (the default)! 00059 * 00060 * @todo: work with IP header options 00061 */ 00062 00063 /** Setting this to 0, you can turn off checking the fragments for overlapping 00064 * regions. The code gets a little smaller. Only use this if you know that 00065 * overlapping won't occur on your network! */ 00066 #ifndef IP_REASS_CHECK_OVERLAP 00067 #define IP_REASS_CHECK_OVERLAP 1 00068 #endif /* IP_REASS_CHECK_OVERLAP */ 00069 00070 /** Set to 0 to prevent freeing the oldest datagram when the reassembly buffer is 00071 * full (IP_REASS_MAX_PBUFS pbufs are enqueued). The code gets a little smaller. 00072 * Datagrams will be freed by timeout only. Especially useful when MEMP_NUM_REASSDATA 00073 * is set to 1, so one datagram can be reassembled at a time, only. */ 00074 #ifndef IP_REASS_FREE_OLDEST 00075 #define IP_REASS_FREE_OLDEST 1 00076 #endif /* IP_REASS_FREE_OLDEST */ 00077 00078 #define IP_REASS_FLAG_LASTFRAG 0x01 00079 00080 /** This is a helper struct which holds the starting 00081 * offset and the ending offset of this fragment to 00082 * easily chain the fragments. 00083 * It has to be packed since it has to fit inside the IP header. 00084 */ 00085 #ifdef PACK_STRUCT_USE_INCLUDES 00086 # include "arch/bpstruct.h" 00087 #endif 00088 PACK_STRUCT_BEGIN 00089 struct ip_reass_helper { 00090 PACK_STRUCT_FIELD(struct pbuf *next_pbuf); 00091 PACK_STRUCT_FIELD(u16_t start); 00092 PACK_STRUCT_FIELD(u16_t end); 00093 } PACK_STRUCT_STRUCT; 00094 PACK_STRUCT_END 00095 #ifdef PACK_STRUCT_USE_INCLUDES 00096 # include "arch/epstruct.h" 00097 #endif 00098 00099 #define IP_ADDRESSES_AND_ID_MATCH(iphdrA, iphdrB) \ 00100 (ip_addr_cmp(&(iphdrA)->src, &(iphdrB)->src) && \ 00101 ip_addr_cmp(&(iphdrA)->dest, &(iphdrB)->dest) && \ 00102 IPH_ID(iphdrA) == IPH_ID(iphdrB)) ? 1 : 0 00103 00104 /* global variables */ 00105 static struct ip_reassdata *reassdatagrams; 00106 static u16_t ip_reass_pbufcount; 00107 00108 /* function prototypes */ 00109 static void ip_reass_dequeue_datagram(struct ip_reassdata *ipr, struct ip_reassdata *prev); 00110 static int ip_reass_free_complete_datagram(struct ip_reassdata *ipr, struct ip_reassdata *prev); 00111 00112 /** 00113 * Reassembly timer base function 00114 * for both NO_SYS == 0 and 1 (!). 00115 * 00116 * Should be called every 1000 msec (defined by IP_TMR_INTERVAL). 00117 */ 00118 void 00119 ip_reass_tmr(void) 00120 { 00121 struct ip_reassdata *r, *prev = NULL; 00122 00123 r = reassdatagrams; 00124 while (r != NULL) { 00125 /* Decrement the timer. Once it reaches 0, 00126 * clean up the incomplete fragment assembly */ 00127 if (r->timer > 0) { 00128 r->timer--; 00129 LWIP_DEBUGF(IP_REASS_DEBUG, ("ip_reass_tmr: timer dec %"U16_F"\n",(u16_t)r->timer)); 00130 prev = r; 00131 r = r->next; 00132 } else { 00133 /* reassembly timed out */ 00134 struct ip_reassdata *tmp; 00135 LWIP_DEBUGF(IP_REASS_DEBUG, ("ip_reass_tmr: timer timed out\n")); 00136 tmp = r; 00137 /* get the next pointer before freeing */ 00138 r = r->next; 00139 /* free the helper struct and all enqueued pbufs */ 00140 ip_reass_free_complete_datagram(tmp, prev); 00141 } 00142 } 00143 } 00144 00145 /** 00146 * Free a datagram (struct ip_reassdata) and all its pbufs. 00147 * Updates the total count of enqueued pbufs (ip_reass_pbufcount), 00148 * SNMP counters and sends an ICMP time exceeded packet. 00149 * 00150 * @param ipr datagram to free 00151 * @param prev the previous datagram in the linked list 00152 * @return the number of pbufs freed 00153 */ 00154 static int 00155 ip_reass_free_complete_datagram(struct ip_reassdata *ipr, struct ip_reassdata *prev) 00156 { 00157 u16_t pbufs_freed = 0; 00158 u8_t clen; 00159 struct pbuf *p; 00160 struct ip_reass_helper *iprh; 00161 00162 LWIP_ASSERT("prev != ipr", prev != ipr); 00163 if (prev != NULL) { 00164 LWIP_ASSERT("prev->next == ipr", prev->next == ipr); 00165 } 00166 00167 snmp_inc_ipreasmfails(); 00168 #if LWIP_ICMP 00169 iprh = (struct ip_reass_helper *)ipr->p->payload; 00170 if (iprh->start == 0) { 00171 /* The first fragment was received, send ICMP time exceeded. */ 00172 /* First, de-queue the first pbuf from r->p. */ 00173 p = ipr->p; 00174 ipr->p = iprh->next_pbuf; 00175 /* Then, copy the original header into it. */ 00176 SMEMCPY(p->payload, &ipr->iphdr, IP_HLEN); 00177 icmp_time_exceeded(p, ICMP_TE_FRAG); 00178 clen = pbuf_clen(p); 00179 LWIP_ASSERT("pbufs_freed + clen <= 0xffff", pbufs_freed + clen <= 0xffff); 00180 pbufs_freed += clen; 00181 pbuf_free(p); 00182 } 00183 #endif /* LWIP_ICMP */ 00184 00185 /* First, free all received pbufs. The individual pbufs need to be released 00186 separately as they have not yet been chained */ 00187 p = ipr->p; 00188 while (p != NULL) { 00189 struct pbuf *pcur; 00190 iprh = (struct ip_reass_helper *)p->payload; 00191 pcur = p; 00192 /* get the next pointer before freeing */ 00193 p = iprh->next_pbuf; 00194 clen = pbuf_clen(pcur); 00195 LWIP_ASSERT("pbufs_freed + clen <= 0xffff", pbufs_freed + clen <= 0xffff); 00196 pbufs_freed += clen; 00197 pbuf_free(pcur); 00198 } 00199 /* Then, unchain the struct ip_reassdata from the list and free it. */ 00200 ip_reass_dequeue_datagram(ipr, prev); 00201 LWIP_ASSERT("ip_reass_pbufcount >= clen", ip_reass_pbufcount >= pbufs_freed); 00202 ip_reass_pbufcount -= pbufs_freed; 00203 00204 return pbufs_freed; 00205 } 00206 00207 #if IP_REASS_FREE_OLDEST 00208 /** 00209 * Free the oldest datagram to make room for enqueueing new fragments. 00210 * The datagram 'fraghdr' belongs to is not freed! 00211 * 00212 * @param fraghdr IP header of the current fragment 00213 * @param pbufs_needed number of pbufs needed to enqueue 00214 * (used for freeing other datagrams if not enough space) 00215 * @return the number of pbufs freed 00216 */ 00217 static int 00218 ip_reass_remove_oldest_datagram(struct ip_hdr *fraghdr, int pbufs_needed) 00219 { 00220 /* @todo Can't we simply remove the last datagram in the 00221 * linked list behind reassdatagrams? 00222 */ 00223 struct ip_reassdata *r, *oldest, *prev; 00224 int pbufs_freed = 0, pbufs_freed_current; 00225 int other_datagrams; 00226 00227 /* Free datagrams until being allowed to enqueue 'pbufs_needed' pbufs, 00228 * but don't free the datagram that 'fraghdr' belongs to! */ 00229 do { 00230 oldest = NULL; 00231 prev = NULL; 00232 other_datagrams = 0; 00233 r = reassdatagrams; 00234 while (r != NULL) { 00235 if (!IP_ADDRESSES_AND_ID_MATCH(&r->iphdr, fraghdr)) { 00236 /* Not the same datagram as fraghdr */ 00237 other_datagrams++; 00238 if (oldest == NULL) { 00239 oldest = r; 00240 } else if (r->timer <= oldest->timer) { 00241 /* older than the previous oldest */ 00242 oldest = r; 00243 } 00244 } 00245 if (r->next != NULL) { 00246 prev = r; 00247 } 00248 r = r->next; 00249 } 00250 if (oldest != NULL) { 00251 pbufs_freed_current = ip_reass_free_complete_datagram(oldest, prev); 00252 pbufs_freed += pbufs_freed_current; 00253 } 00254 } while ((pbufs_freed < pbufs_needed) && (other_datagrams > 1)); 00255 return pbufs_freed; 00256 } 00257 #endif /* IP_REASS_FREE_OLDEST */ 00258 00259 /** 00260 * Enqueues a new fragment into the fragment queue 00261 * @param fraghdr points to the new fragments IP hdr 00262 * @param clen number of pbufs needed to enqueue (used for freeing other datagrams if not enough space) 00263 * @return A pointer to the queue location into which the fragment was enqueued 00264 */ 00265 static struct ip_reassdata* 00266 ip_reass_enqueue_new_datagram(struct ip_hdr *fraghdr, int clen) 00267 { 00268 struct ip_reassdata* ipr; 00269 /* No matching previous fragment found, allocate a new reassdata struct */ 00270 ipr = (struct ip_reassdata*) memp_malloc(MEMP_REASSDATA); 00271 if (ipr == NULL) { 00272 #if IP_REASS_FREE_OLDEST 00273 if (ip_reass_remove_oldest_datagram(fraghdr, clen) >= clen) { 00274 ipr = (struct ip_reassdata*) memp_malloc(MEMP_REASSDATA); 00275 } 00276 if (ipr == NULL) 00277 #endif /* IP_REASS_FREE_OLDEST */ 00278 { 00279 IPFRAG_STATS_INC(ip_frag.memerr); 00280 LWIP_DEBUGF(IP_REASS_DEBUG,("Failed to alloc reassdata struct\n")); 00281 return NULL; 00282 } 00283 } 00284 memset(ipr, 0, sizeof(struct ip_reassdata)); 00285 ipr->timer = IP_REASS_MAXAGE; 00286 00287 /* enqueue the new structure to the front of the list */ 00288 ipr->next = reassdatagrams; 00289 reassdatagrams = ipr; 00290 /* copy the ip header for later tests and input */ 00291 /* @todo: no ip options supported? */ 00292 SMEMCPY(&(ipr->iphdr), fraghdr, IP_HLEN); 00293 return ipr; 00294 } 00295 00296 /** 00297 * Dequeues a datagram from the datagram queue. Doesn't deallocate the pbufs. 00298 * @param ipr points to the queue entry to dequeue 00299 */ 00300 static void 00301 ip_reass_dequeue_datagram(struct ip_reassdata *ipr, struct ip_reassdata *prev) 00302 { 00303 00304 /* dequeue the reass struct */ 00305 if (reassdatagrams == ipr) { 00306 /* it was the first in the list */ 00307 reassdatagrams = ipr->next; 00308 } else { 00309 /* it wasn't the first, so it must have a valid 'prev' */ 00310 LWIP_ASSERT("sanity check linked list", prev != NULL); 00311 prev->next = ipr->next; 00312 } 00313 00314 /* now we can free the ip_reass struct */ 00315 memp_free(MEMP_REASSDATA, ipr); 00316 } 00317 00318 /** 00319 * Chain a new pbuf into the pbuf list that composes the datagram. The pbuf list 00320 * will grow over time as new pbufs are rx. 00321 * Also checks that the datagram passes basic continuity checks (if the last 00322 * fragment was received at least once). 00323 * @param root_p points to the 'root' pbuf for the current datagram being assembled. 00324 * @param new_p points to the pbuf for the current fragment 00325 * @return 0 if invalid, >0 otherwise 00326 */ 00327 static int 00328 ip_reass_chain_frag_into_datagram_and_validate(struct ip_reassdata *ipr, struct pbuf *new_p) 00329 { 00330 struct ip_reass_helper *iprh, *iprh_tmp, *iprh_prev=NULL; 00331 struct pbuf *q; 00332 u16_t offset,len; 00333 struct ip_hdr *fraghdr; 00334 int valid = 1; 00335 00336 /* Extract length and fragment offset from current fragment */ 00337 fraghdr = (struct ip_hdr*)new_p->payload; 00338 len = ntohs(IPH_LEN(fraghdr)) - IPH_HL(fraghdr) * 4; 00339 offset = (ntohs(IPH_OFFSET(fraghdr)) & IP_OFFMASK) * 8; 00340 00341 /* overwrite the fragment's ip header from the pbuf with our helper struct, 00342 * and setup the embedded helper structure. */ 00343 /* make sure the struct ip_reass_helper fits into the IP header */ 00344 LWIP_ASSERT("sizeof(struct ip_reass_helper) <= IP_HLEN", 00345 sizeof(struct ip_reass_helper) <= IP_HLEN); 00346 iprh = (struct ip_reass_helper*)new_p->payload; 00347 iprh->next_pbuf = NULL; 00348 iprh->start = offset; 00349 iprh->end = offset + len; 00350 00351 /* Iterate through until we either get to the end of the list (append), 00352 * or we find on with a larger offset (insert). */ 00353 for (q = ipr->p; q != NULL;) { 00354 iprh_tmp = (struct ip_reass_helper*)q->payload; 00355 if (iprh->start < iprh_tmp->start) { 00356 /* the new pbuf should be inserted before this */ 00357 iprh->next_pbuf = q; 00358 if (iprh_prev != NULL) { 00359 /* not the fragment with the lowest offset */ 00360 #if IP_REASS_CHECK_OVERLAP 00361 if ((iprh->start < iprh_prev->end) || (iprh->end > iprh_tmp->start)) { 00362 /* fragment overlaps with previous or following, throw away */ 00363 goto freepbuf; 00364 } 00365 #endif /* IP_REASS_CHECK_OVERLAP */ 00366 iprh_prev->next_pbuf = new_p; 00367 } else { 00368 /* fragment with the lowest offset */ 00369 ipr->p = new_p; 00370 } 00371 break; 00372 } else if(iprh->start == iprh_tmp->start) { 00373 /* received the same datagram twice: no need to keep the datagram */ 00374 goto freepbuf; 00375 #if IP_REASS_CHECK_OVERLAP 00376 } else if(iprh->start < iprh_tmp->end) { 00377 /* overlap: no need to keep the new datagram */ 00378 goto freepbuf; 00379 #endif /* IP_REASS_CHECK_OVERLAP */ 00380 } else { 00381 /* Check if the fragments received so far have no wholes. */ 00382 if (iprh_prev != NULL) { 00383 if (iprh_prev->end != iprh_tmp->start) { 00384 /* There is a fragment missing between the current 00385 * and the previous fragment */ 00386 valid = 0; 00387 } 00388 } 00389 } 00390 q = iprh_tmp->next_pbuf; 00391 iprh_prev = iprh_tmp; 00392 } 00393 00394 /* If q is NULL, then we made it to the end of the list. Determine what to do now */ 00395 if (q == NULL) { 00396 if (iprh_prev != NULL) { 00397 /* this is (for now), the fragment with the highest offset: 00398 * chain it to the last fragment */ 00399 #if IP_REASS_CHECK_OVERLAP 00400 LWIP_ASSERT("check fragments don't overlap", iprh_prev->end <= iprh->start); 00401 #endif /* IP_REASS_CHECK_OVERLAP */ 00402 iprh_prev->next_pbuf = new_p; 00403 if (iprh_prev->end != iprh->start) { 00404 valid = 0; 00405 } 00406 } else { 00407 #if IP_REASS_CHECK_OVERLAP 00408 LWIP_ASSERT("no previous fragment, this must be the first fragment!", 00409 ipr->p == NULL); 00410 #endif /* IP_REASS_CHECK_OVERLAP */ 00411 /* this is the first fragment we ever received for this ip datagram */ 00412 ipr->p = new_p; 00413 } 00414 } 00415 00416 /* At this point, the validation part begins: */ 00417 /* If we already received the last fragment */ 00418 if ((ipr->flags & IP_REASS_FLAG_LASTFRAG) != 0) { 00419 /* and had no wholes so far */ 00420 if (valid) { 00421 /* then check if the rest of the fragments is here */ 00422 /* Check if the queue starts with the first datagram */ 00423 if (((struct ip_reass_helper*)ipr->p->payload)->start != 0) { 00424 valid = 0; 00425 } else { 00426 /* and check that there are no wholes after this datagram */ 00427 iprh_prev = iprh; 00428 q = iprh->next_pbuf; 00429 while (q != NULL) { 00430 iprh = (struct ip_reass_helper*)q->payload; 00431 if (iprh_prev->end != iprh->start) { 00432 valid = 0; 00433 break; 00434 } 00435 iprh_prev = iprh; 00436 q = iprh->next_pbuf; 00437 } 00438 /* if still valid, all fragments are received 00439 * (because to the MF==0 already arrived */ 00440 if (valid) { 00441 LWIP_ASSERT("sanity check", ipr->p != NULL); 00442 LWIP_ASSERT("sanity check", 00443 ((struct ip_reass_helper*)ipr->p->payload) != iprh); 00444 LWIP_ASSERT("validate_datagram:next_pbuf!=NULL", 00445 iprh->next_pbuf == NULL); 00446 LWIP_ASSERT("validate_datagram:datagram end!=datagram len", 00447 iprh->end == ipr->datagram_len); 00448 } 00449 } 00450 } 00451 /* If valid is 0 here, there are some fragments missing in the middle 00452 * (since MF == 0 has already arrived). Such datagrams simply time out if 00453 * no more fragments are received... */ 00454 return valid; 00455 } 00456 /* If we come here, not all fragments were received, yet! */ 00457 return 0; /* not yet valid! */ 00458 #if IP_REASS_CHECK_OVERLAP 00459 freepbuf: 00460 ip_reass_pbufcount -= pbuf_clen(new_p); 00461 pbuf_free(new_p); 00462 return 0; 00463 #endif /* IP_REASS_CHECK_OVERLAP */ 00464 } 00465 00466 /** 00467 * Reassembles incoming IP fragments into an IP datagram. 00468 * 00469 * @param p points to a pbuf chain of the fragment 00470 * @return NULL if reassembly is incomplete, ? otherwise 00471 */ 00472 struct pbuf * 00473 ip_reass(struct pbuf *p) 00474 { 00475 struct pbuf *r; 00476 struct ip_hdr *fraghdr; 00477 struct ip_reassdata *ipr; 00478 struct ip_reass_helper *iprh; 00479 u16_t offset, len; 00480 u8_t clen; 00481 struct ip_reassdata *ipr_prev = NULL; 00482 00483 IPFRAG_STATS_INC(ip_frag.recv); 00484 snmp_inc_ipreasmreqds(); 00485 00486 fraghdr = (struct ip_hdr*)p->payload; 00487 00488 if ((IPH_HL(fraghdr) * 4) != IP_HLEN) { 00489 LWIP_DEBUGF(IP_REASS_DEBUG,("ip_reass: IP options currently not supported!\n")); 00490 IPFRAG_STATS_INC(ip_frag.err); 00491 goto nullreturn; 00492 } 00493 00494 offset = (ntohs(IPH_OFFSET(fraghdr)) & IP_OFFMASK) * 8; 00495 len = ntohs(IPH_LEN(fraghdr)) - IPH_HL(fraghdr) * 4; 00496 00497 /* Check if we are allowed to enqueue more datagrams. */ 00498 clen = pbuf_clen(p); 00499 if ((ip_reass_pbufcount + clen) > IP_REASS_MAX_PBUFS) { 00500 #if IP_REASS_FREE_OLDEST 00501 if (!ip_reass_remove_oldest_datagram(fraghdr, clen) || 00502 ((ip_reass_pbufcount + clen) > IP_REASS_MAX_PBUFS)) 00503 #endif /* IP_REASS_FREE_OLDEST */ 00504 { 00505 /* No datagram could be freed and still too many pbufs enqueued */ 00506 LWIP_DEBUGF(IP_REASS_DEBUG,("ip_reass: Overflow condition: pbufct=%d, clen=%d, MAX=%d\n", 00507 ip_reass_pbufcount, clen, IP_REASS_MAX_PBUFS)); 00508 IPFRAG_STATS_INC(ip_frag.memerr); 00509 /* @todo: send ICMP time exceeded here? */ 00510 /* drop this pbuf */ 00511 goto nullreturn; 00512 } 00513 } 00514 00515 /* Look for the datagram the fragment belongs to in the current datagram queue, 00516 * remembering the previous in the queue for later dequeueing. */ 00517 for (ipr = reassdatagrams; ipr != NULL; ipr = ipr->next) { 00518 /* Check if the incoming fragment matches the one currently present 00519 in the reassembly buffer. If so, we proceed with copying the 00520 fragment into the buffer. */ 00521 if (IP_ADDRESSES_AND_ID_MATCH(&ipr->iphdr, fraghdr)) { 00522 LWIP_DEBUGF(IP_REASS_DEBUG, ("ip_reass: matching previous fragment ID=%"X16_F"\n", 00523 ntohs(IPH_ID(fraghdr)))); 00524 IPFRAG_STATS_INC(ip_frag.cachehit); 00525 break; 00526 } 00527 ipr_prev = ipr; 00528 } 00529 00530 if (ipr == NULL) { 00531 /* Enqueue a new datagram into the datagram queue */ 00532 ipr = ip_reass_enqueue_new_datagram(fraghdr, clen); 00533 /* Bail if unable to enqueue */ 00534 if(ipr == NULL) { 00535 goto nullreturn; 00536 } 00537 } else { 00538 if (((ntohs(IPH_OFFSET(fraghdr)) & IP_OFFMASK) == 0) && 00539 ((ntohs(IPH_OFFSET(&ipr->iphdr)) & IP_OFFMASK) != 0)) { 00540 /* ipr->iphdr is not the header from the first fragment, but fraghdr is 00541 * -> copy fraghdr into ipr->iphdr since we want to have the header 00542 * of the first fragment (for ICMP time exceeded and later, for copying 00543 * all options, if supported)*/ 00544 SMEMCPY(&ipr->iphdr, fraghdr, IP_HLEN); 00545 } 00546 } 00547 /* Track the current number of pbufs current 'in-flight', in order to limit 00548 the number of fragments that may be enqueued at any one time */ 00549 ip_reass_pbufcount += clen; 00550 00551 /* At this point, we have either created a new entry or pointing 00552 * to an existing one */ 00553 00554 /* check for 'no more fragments', and update queue entry*/ 00555 if ((ntohs(IPH_OFFSET(fraghdr)) & IP_MF) == 0) { 00556 ipr->flags |= IP_REASS_FLAG_LASTFRAG; 00557 ipr->datagram_len = offset + len; 00558 LWIP_DEBUGF(IP_REASS_DEBUG, 00559 ("ip_reass: last fragment seen, total len %"S16_F"\n", 00560 ipr->datagram_len)); 00561 } 00562 /* find the right place to insert this pbuf */ 00563 /* @todo: trim pbufs if fragments are overlapping */ 00564 if (ip_reass_chain_frag_into_datagram_and_validate(ipr, p)) { 00565 /* the totally last fragment (flag more fragments = 0) was received at least 00566 * once AND all fragments are received */ 00567 ipr->datagram_len += IP_HLEN; 00568 00569 /* save the second pbuf before copying the header over the pointer */ 00570 r = ((struct ip_reass_helper*)ipr->p->payload)->next_pbuf; 00571 00572 /* copy the original ip header back to the first pbuf */ 00573 fraghdr = (struct ip_hdr*)(ipr->p->payload); 00574 SMEMCPY(fraghdr, &ipr->iphdr, IP_HLEN); 00575 IPH_LEN_SET(fraghdr, htons(ipr->datagram_len)); 00576 IPH_OFFSET_SET(fraghdr, 0); 00577 IPH_CHKSUM_SET(fraghdr, 0); 00578 /* @todo: do we need to set calculate the correct checksum? */ 00579 IPH_CHKSUM_SET(fraghdr, inet_chksum(fraghdr, IP_HLEN)); 00580 00581 p = ipr->p; 00582 00583 /* chain together the pbufs contained within the reass_data list. */ 00584 while(r != NULL) { 00585 iprh = (struct ip_reass_helper*)r->payload; 00586 00587 /* hide the ip header for every succeding fragment */ 00588 pbuf_header(r, -IP_HLEN); 00589 pbuf_cat(p, r); 00590 r = iprh->next_pbuf; 00591 } 00592 /* release the sources allocate for the fragment queue entry */ 00593 ip_reass_dequeue_datagram(ipr, ipr_prev); 00594 00595 /* and adjust the number of pbufs currently queued for reassembly. */ 00596 ip_reass_pbufcount -= pbuf_clen(p); 00597 00598 /* Return the pbuf chain */ 00599 return p; 00600 } 00601 /* the datagram is not (yet?) reassembled completely */ 00602 LWIP_DEBUGF(IP_REASS_DEBUG,("ip_reass_pbufcount: %d out\n", ip_reass_pbufcount)); 00603 return NULL; 00604 00605 nullreturn: 00606 LWIP_DEBUGF(IP_REASS_DEBUG,("ip_reass: nullreturn\n")); 00607 IPFRAG_STATS_INC(ip_frag.drop); 00608 pbuf_free(p); 00609 return NULL; 00610 } 00611 #endif /* IP_REASSEMBLY */ 00612 00613 #if IP_FRAG 00614 #if IP_FRAG_USES_STATIC_BUF 00615 static u8_t buf[LWIP_MEM_ALIGN_SIZE(IP_FRAG_MAX_MTU + MEM_ALIGNMENT - 1)]; 00616 #endif /* IP_FRAG_USES_STATIC_BUF */ 00617 00618 /** 00619 * Fragment an IP datagram if too large for the netif. 00620 * 00621 * Chop the datagram in MTU sized chunks and send them in order 00622 * by using a fixed size static memory buffer (PBUF_REF) or 00623 * point PBUF_REFs into p (depending on IP_FRAG_USES_STATIC_BUF). 00624 * 00625 * @param p ip packet to send 00626 * @param netif the netif on which to send 00627 * @param dest destination ip address to which to send 00628 * 00629 * @return ERR_OK if sent successfully, err_t otherwise 00630 */ 00631 err_t 00632 ip_frag(struct pbuf *p, struct netif *netif, ip_addr_t *dest) 00633 { 00634 struct pbuf *rambuf; 00635 #if IP_FRAG_USES_STATIC_BUF 00636 struct pbuf *header; 00637 #else 00638 struct pbuf *newpbuf; 00639 struct ip_hdr *original_iphdr; 00640 #endif 00641 struct ip_hdr *iphdr; 00642 u16_t nfb; 00643 u16_t left, cop; 00644 u16_t mtu = netif->mtu; 00645 u16_t ofo, omf; 00646 u16_t last; 00647 u16_t poff = IP_HLEN; 00648 u16_t tmp; 00649 #if !IP_FRAG_USES_STATIC_BUF 00650 u16_t newpbuflen = 0; 00651 u16_t left_to_copy; 00652 #endif 00653 00654 /* Get a RAM based MTU sized pbuf */ 00655 #if IP_FRAG_USES_STATIC_BUF 00656 /* When using a static buffer, we use a PBUF_REF, which we will 00657 * use to reference the packet (without link header). 00658 * Layer and length is irrelevant. 00659 */ 00660 rambuf = pbuf_alloc(PBUF_LINK, 0, PBUF_REF); 00661 if (rambuf == NULL) { 00662 LWIP_DEBUGF(IP_REASS_DEBUG, ("ip_frag: pbuf_alloc(PBUF_LINK, 0, PBUF_REF) failed\n")); 00663 return ERR_MEM; 00664 } 00665 rambuf->tot_len = rambuf->len = mtu; 00666 rambuf->payload = LWIP_MEM_ALIGN((void *)buf); 00667 00668 /* Copy the IP header in it */ 00669 iphdr = (struct ip_hdr*) rambuf->payload; 00670 SMEMCPY(iphdr, p->payload, IP_HLEN); 00671 #else /* IP_FRAG_USES_STATIC_BUF */ 00672 original_iphdr = (struct ip_hdr*) p->payload; 00673 iphdr = original_iphdr; 00674 #endif /* IP_FRAG_USES_STATIC_BUF */ 00675 00676 /* Save original offset */ 00677 tmp = ntohs(IPH_OFFSET(iphdr)); 00678 ofo = tmp & IP_OFFMASK; 00679 omf = tmp & IP_MF; 00680 00681 left = p->tot_len - IP_HLEN; 00682 00683 nfb = (mtu - IP_HLEN) / 8; 00684 00685 while (left) { 00686 last = (left <= mtu - IP_HLEN); 00687 00688 /* Set new offset and MF flag */ 00689 tmp = omf | (IP_OFFMASK & (ofo)); 00690 if (!last) { 00691 tmp = tmp | IP_MF; 00692 } 00693 00694 /* Fill this fragment */ 00695 cop = last ? left : nfb * 8; 00696 00697 #if IP_FRAG_USES_STATIC_BUF 00698 poff += pbuf_copy_partial(p, (u8_t*)iphdr + IP_HLEN, cop, poff); 00699 #else /* IP_FRAG_USES_STATIC_BUF */ 00700 /* When not using a static buffer, create a chain of pbufs. 00701 * The first will be a PBUF_RAM holding the link and IP header. 00702 * The rest will be PBUF_REFs mirroring the pbuf chain to be fragged, 00703 * but limited to the size of an mtu. 00704 */ 00705 rambuf = pbuf_alloc(PBUF_LINK, IP_HLEN, PBUF_RAM); 00706 if (rambuf == NULL) { 00707 return ERR_MEM; 00708 } 00709 LWIP_ASSERT("this needs a pbuf in one piece!", 00710 (p->len >= (IP_HLEN))); 00711 SMEMCPY(rambuf->payload, original_iphdr, IP_HLEN); 00712 iphdr = (struct ip_hdr*) rambuf->payload; 00713 00714 /* Can just adjust p directly for needed offset. */ 00715 p->payload = (u8_t *)p->payload + poff; 00716 p->len -= poff; 00717 00718 left_to_copy = cop; 00719 while (left_to_copy) { 00720 newpbuflen = (left_to_copy < p->len) ? left_to_copy : p->len; 00721 /* Is this pbuf already empty? */ 00722 if (!newpbuflen) { 00723 p = p->next; 00724 continue; 00725 } 00726 newpbuf = pbuf_alloc(PBUF_RAW, 0, PBUF_REF); 00727 if (newpbuf == NULL) { 00728 pbuf_free(rambuf); 00729 return ERR_MEM; 00730 } 00731 /* Mirror this pbuf, although we might not need all of it. */ 00732 newpbuf->payload = p->payload; 00733 newpbuf->len = newpbuf->tot_len = newpbuflen; 00734 /* Add it to end of rambuf's chain, but using pbuf_cat, not pbuf_chain 00735 * so that it is removed when pbuf_dechain is later called on rambuf. 00736 */ 00737 pbuf_cat(rambuf, newpbuf); 00738 left_to_copy -= newpbuflen; 00739 if (left_to_copy) { 00740 p = p->next; 00741 } 00742 } 00743 poff = newpbuflen; 00744 #endif /* IP_FRAG_USES_STATIC_BUF */ 00745 00746 /* Correct header */ 00747 IPH_OFFSET_SET(iphdr, htons(tmp)); 00748 IPH_LEN_SET(iphdr, htons(cop + IP_HLEN)); 00749 IPH_CHKSUM_SET(iphdr, 0); 00750 IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, IP_HLEN)); 00751 00752 #if IP_FRAG_USES_STATIC_BUF 00753 if (last) { 00754 pbuf_realloc(rambuf, left + IP_HLEN); 00755 } 00756 00757 /* This part is ugly: we alloc a RAM based pbuf for 00758 * the link level header for each chunk and then 00759 * free it.A PBUF_ROM style pbuf for which pbuf_header 00760 * worked would make things simpler. 00761 */ 00762 header = pbuf_alloc(PBUF_LINK, 0, PBUF_RAM); 00763 if (header != NULL) { 00764 pbuf_chain(header, rambuf); 00765 netif->output(netif, header, dest); 00766 IPFRAG_STATS_INC(ip_frag.xmit); 00767 snmp_inc_ipfragcreates(); 00768 pbuf_free(header); 00769 } else { 00770 LWIP_DEBUGF(IP_REASS_DEBUG, ("ip_frag: pbuf_alloc() for header failed\n")); 00771 pbuf_free(rambuf); 00772 return ERR_MEM; 00773 } 00774 #else /* IP_FRAG_USES_STATIC_BUF */ 00775 /* No need for separate header pbuf - we allowed room for it in rambuf 00776 * when allocated. 00777 */ 00778 netif->output(netif, rambuf, dest); 00779 IPFRAG_STATS_INC(ip_frag.xmit); 00780 00781 /* Unfortunately we can't reuse rambuf - the hardware may still be 00782 * using the buffer. Instead we free it (and the ensuing chain) and 00783 * recreate it next time round the loop. If we're lucky the hardware 00784 * will have already sent the packet, the free will really free, and 00785 * there will be zero memory penalty. 00786 */ 00787 00788 pbuf_free(rambuf); 00789 #endif /* IP_FRAG_USES_STATIC_BUF */ 00790 left -= cop; 00791 ofo += nfb; 00792 } 00793 #if IP_FRAG_USES_STATIC_BUF 00794 pbuf_free(rambuf); 00795 #endif /* IP_FRAG_USES_STATIC_BUF */ 00796 snmp_inc_ipfragoks(); 00797 return ERR_OK; 00798 } 00799 #endif /* IP_FRAG */
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