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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/ip.h" 00044 #include "lwip/inet.h" 00045 #include "lwip/inet_chksum.h" 00046 #include "lwip/netif.h" 00047 #include "lwip/snmp.h" 00048 #include "lwip/stats.h" 00049 #include "lwip/icmp.h" 00050 00051 #include <string.h> 00052 00053 #if IP_REASSEMBLY 00054 /** 00055 * The IP reassembly code currently has the following limitations: 00056 * - IP header options are not supported 00057 * - fragments must not overlap (e.g. due to different routes), 00058 * currently, overlapping or duplicate fragments are thrown away 00059 * if IP_REASS_CHECK_OVERLAP=1 (the default)! 00060 * 00061 * @todo: work with IP header options 00062 */ 00063 00064 /** Setting this to 0, you can turn off checking the fragments for overlapping 00065 * regions. The code gets a little smaller. Only use this if you know that 00066 * overlapping won't occur on your network! */ 00067 #ifndef IP_REASS_CHECK_OVERLAP 00068 #define IP_REASS_CHECK_OVERLAP 1 00069 #endif /* IP_REASS_CHECK_OVERLAP */ 00070 00071 /** Set to 0 to prevent freeing the oldest datagram when the reassembly buffer is 00072 * full (IP_REASS_MAX_PBUFS pbufs are enqueued). The code gets a little smaller. 00073 * Datagrams will be freed by timeout only. Especially useful when MEMP_NUM_REASSDATA 00074 * is set to 1, so one datagram can be reassembled at a time, only. */ 00075 #ifndef IP_REASS_FREE_OLDEST 00076 #define IP_REASS_FREE_OLDEST 1 00077 #endif /* IP_REASS_FREE_OLDEST */ 00078 00079 #define IP_REASS_FLAG_LASTFRAG 0x01 00080 00081 /** This is a helper struct which holds the starting 00082 * offset and the ending offset of this fragment to 00083 * easily chain the fragments. 00084 * It has to be packed since it has to fit inside the IP header. 00085 */ 00086 00087 // XXX: For armcc 00088 struct ip_reass_helper { 00089 struct pbuf *next_pbuf; 00090 u16_t start; 00091 u16_t end; 00092 }; 00093 00094 /* // Will not work with armcc 00095 #ifdef PACK_STRUCT_USE_INCLUDES 00096 # include "arch/bpstruct.h" 00097 #endif 00098 PACK_STRUCT_BEGIN 00099 struct ip_reass_helper { 00100 PACK_STRUCT_FIELD(struct pbuf *next_pbuf); 00101 PACK_STRUCT_FIELD(u16_t start); 00102 PACK_STRUCT_FIELD(u16_t end); 00103 } PACK_STRUCT_STRUCT; 00104 PACK_STRUCT_END 00105 #ifdef PACK_STRUCT_USE_INCLUDES 00106 # include "arch/epstruct.h" 00107 #endif 00108 */ 00109 00110 #define IP_ADDRESSES_AND_ID_MATCH(iphdrA, iphdrB) \ 00111 (ip_addr_cmp(&(iphdrA)->src, &(iphdrB)->src) && \ 00112 ip_addr_cmp(&(iphdrA)->dest, &(iphdrB)->dest) && \ 00113 IPH_ID(iphdrA) == IPH_ID(iphdrB)) ? 1 : 0 00114 00115 /* global variables */ 00116 static struct ip_reassdata *reassdatagrams; 00117 static u16_t ip_reass_pbufcount; 00118 00119 /* function prototypes */ 00120 static void ip_reass_dequeue_datagram(struct ip_reassdata *ipr, struct ip_reassdata *prev); 00121 static int ip_reass_free_complete_datagram(struct ip_reassdata *ipr, struct ip_reassdata *prev); 00122 00123 /** 00124 * Reassembly timer base function 00125 * for both NO_SYS == 0 and 1 (!). 00126 * 00127 * Should be called every 1000 msec (defined by IP_TMR_INTERVAL). 00128 */ 00129 void 00130 ip_reass_tmr(void) 00131 { 00132 struct ip_reassdata *r, *prev = NULL; 00133 00134 r = reassdatagrams; 00135 while (r != NULL) { 00136 /* Decrement the timer. Once it reaches 0, 00137 * clean up the incomplete fragment assembly */ 00138 if (r->timer > 0) { 00139 r->timer--; 00140 LWIP_DEBUGF(IP_REASS_DEBUG, ("ip_reass_tmr: timer dec %"U16_F"\n",(u16_t)r->timer)); 00141 prev = r; 00142 r = r->next; 00143 } else { 00144 /* reassembly timed out */ 00145 struct ip_reassdata *tmp; 00146 LWIP_DEBUGF(IP_REASS_DEBUG, ("ip_reass_tmr: timer timed out\n")); 00147 tmp = r; 00148 /* get the next pointer before freeing */ 00149 r = r->next; 00150 /* free the helper struct and all enqueued pbufs */ 00151 ip_reass_free_complete_datagram(tmp, prev); 00152 } 00153 } 00154 } 00155 00156 /** 00157 * Free a datagram (struct ip_reassdata) and all its pbufs. 00158 * Updates the total count of enqueued pbufs (ip_reass_pbufcount), 00159 * SNMP counters and sends an ICMP time exceeded packet. 00160 * 00161 * @param ipr datagram to free 00162 * @param prev the previous datagram in the linked list 00163 * @return the number of pbufs freed 00164 */ 00165 static int 00166 ip_reass_free_complete_datagram(struct ip_reassdata *ipr, struct ip_reassdata *prev) 00167 { 00168 int pbufs_freed = 0; 00169 struct pbuf *p; 00170 struct ip_reass_helper *iprh; 00171 00172 LWIP_ASSERT("prev != ipr", prev != ipr); 00173 if (prev != NULL) { 00174 LWIP_ASSERT("prev->next == ipr", prev->next == ipr); 00175 } 00176 00177 snmp_inc_ipreasmfails(); 00178 #if LWIP_ICMP 00179 iprh = (struct ip_reass_helper *)ipr->p->payload; 00180 if (iprh->start == 0) { 00181 /* The first fragment was received, send ICMP time exceeded. */ 00182 /* First, de-queue the first pbuf from r->p. */ 00183 p = ipr->p; 00184 ipr->p = iprh->next_pbuf; 00185 /* Then, copy the original header into it. */ 00186 SMEMCPY(p->payload, &ipr->iphdr, IP_HLEN); 00187 icmp_time_exceeded(p, ICMP_TE_FRAG); 00188 pbufs_freed += pbuf_clen(p); 00189 pbuf_free(p); 00190 } 00191 #endif /* LWIP_ICMP */ 00192 00193 /* First, free all received pbufs. The individual pbufs need to be released 00194 separately as they have not yet been chained */ 00195 p = ipr->p; 00196 while (p != NULL) { 00197 struct pbuf *pcur; 00198 iprh = (struct ip_reass_helper *)p->payload; 00199 pcur = p; 00200 /* get the next pointer before freeing */ 00201 p = iprh->next_pbuf; 00202 pbufs_freed += pbuf_clen(pcur); 00203 pbuf_free(pcur); 00204 } 00205 /* Then, unchain the struct ip_reassdata from the list and free it. */ 00206 ip_reass_dequeue_datagram(ipr, prev); 00207 LWIP_ASSERT("ip_reass_pbufcount >= clen", ip_reass_pbufcount >= pbufs_freed); 00208 ip_reass_pbufcount -= pbufs_freed; 00209 00210 return pbufs_freed; 00211 } 00212 00213 #if IP_REASS_FREE_OLDEST 00214 /** 00215 * Free the oldest datagram to make room for enqueueing new fragments. 00216 * The datagram 'fraghdr' belongs to is not freed! 00217 * 00218 * @param fraghdr IP header of the current fragment 00219 * @param pbufs_needed number of pbufs needed to enqueue 00220 * (used for freeing other datagrams if not enough space) 00221 * @return the number of pbufs freed 00222 */ 00223 static int 00224 ip_reass_remove_oldest_datagram(struct ip_hdr *fraghdr, int pbufs_needed) 00225 { 00226 /* @todo Can't we simply remove the last datagram in the 00227 * linked list behind reassdatagrams? 00228 */ 00229 struct ip_reassdata *r, *oldest, *prev; 00230 int pbufs_freed = 0, pbufs_freed_current; 00231 int other_datagrams; 00232 00233 /* Free datagrams until being allowed to enqueue 'pbufs_needed' pbufs, 00234 * but don't free the datagram that 'fraghdr' belongs to! */ 00235 do { 00236 oldest = NULL; 00237 prev = NULL; 00238 other_datagrams = 0; 00239 r = reassdatagrams; 00240 while (r != NULL) { 00241 if (!IP_ADDRESSES_AND_ID_MATCH(&r->iphdr, fraghdr)) { 00242 /* Not the same datagram as fraghdr */ 00243 other_datagrams++; 00244 if (oldest == NULL) { 00245 oldest = r; 00246 } else if (r->timer <= oldest->timer) { 00247 /* older than the previous oldest */ 00248 oldest = r; 00249 } 00250 } 00251 if (r->next != NULL) { 00252 prev = r; 00253 } 00254 r = r->next; 00255 } 00256 if (oldest != NULL) { 00257 pbufs_freed_current = ip_reass_free_complete_datagram(oldest, prev); 00258 pbufs_freed += pbufs_freed_current; 00259 } 00260 } while ((pbufs_freed < pbufs_needed) && (other_datagrams > 1)); 00261 return pbufs_freed; 00262 } 00263 #endif /* IP_REASS_FREE_OLDEST */ 00264 00265 /** 00266 * Enqueues a new fragment into the fragment queue 00267 * @param fraghdr points to the new fragments IP hdr 00268 * @param clen number of pbufs needed to enqueue (used for freeing other datagrams if not enough space) 00269 * @return A pointer to the queue location into which the fragment was enqueued 00270 */ 00271 static struct ip_reassdata* 00272 ip_reass_enqueue_new_datagram(struct ip_hdr *fraghdr, int clen) 00273 { 00274 struct ip_reassdata* ipr; 00275 /* No matching previous fragment found, allocate a new reassdata struct */ 00276 ipr = (struct ip_reassdata *)(memp_malloc(MEMP_REASSDATA)); // static_cast<struct ip_reassdata *>(x) 00277 if (ipr == NULL) { 00278 #if IP_REASS_FREE_OLDEST 00279 if (ip_reass_remove_oldest_datagram(fraghdr, clen) >= clen) { 00280 ipr = (struct ip_reassdata *)(memp_malloc(MEMP_REASSDATA)); // static_cast<struct ip_reassdata *>(x) 00281 } 00282 if (ipr == NULL) 00283 #endif /* IP_REASS_FREE_OLDEST */ 00284 { 00285 IPFRAG_STATS_INC(ip_frag.memerr); 00286 LWIP_DEBUGF(IP_REASS_DEBUG,("Failed to alloc reassdata struct\n")); 00287 return NULL; 00288 } 00289 } 00290 memset(ipr, 0, sizeof(struct ip_reassdata)); 00291 ipr->timer = IP_REASS_MAXAGE; 00292 00293 /* enqueue the new structure to the front of the list */ 00294 ipr->next = reassdatagrams; 00295 reassdatagrams = ipr; 00296 /* copy the ip header for later tests and input */ 00297 /* @todo: no ip options supported? */ 00298 SMEMCPY(&(ipr->iphdr), fraghdr, IP_HLEN); 00299 return ipr; 00300 } 00301 00302 /** 00303 * Dequeues a datagram from the datagram queue. Doesn't deallocate the pbufs. 00304 * @param ipr points to the queue entry to dequeue 00305 */ 00306 static void 00307 ip_reass_dequeue_datagram(struct ip_reassdata *ipr, struct ip_reassdata *prev) 00308 { 00309 00310 /* dequeue the reass struct */ 00311 if (reassdatagrams == ipr) { 00312 /* it was the first in the list */ 00313 reassdatagrams = ipr->next; 00314 } else { 00315 /* it wasn't the first, so it must have a valid 'prev' */ 00316 LWIP_ASSERT("sanity check linked list", prev != NULL); 00317 prev->next = ipr->next; 00318 } 00319 00320 /* now we can free the ip_reass struct */ 00321 memp_free(MEMP_REASSDATA, ipr); 00322 } 00323 00324 /** 00325 * Chain a new pbuf into the pbuf list that composes the datagram. The pbuf list 00326 * will grow over time as new pbufs are rx. 00327 * Also checks that the datagram passes basic continuity checks (if the last 00328 * fragment was received at least once). 00329 * @param root_p points to the 'root' pbuf for the current datagram being assembled. 00330 * @param new_p points to the pbuf for the current fragment 00331 * @return 0 if invalid, >0 otherwise 00332 */ 00333 static int 00334 ip_reass_chain_frag_into_datagram_and_validate(struct ip_reassdata *ipr, struct pbuf *new_p) 00335 { 00336 struct ip_reass_helper *iprh, *iprh_tmp, *iprh_prev=NULL; 00337 struct pbuf *q; 00338 u16_t offset,len; 00339 struct ip_hdr *fraghdr; 00340 int valid = 1; 00341 00342 /* Extract length and fragment offset from current fragment */ 00343 fraghdr = (struct ip_hdr*)new_p->payload; 00344 len = ntohs(IPH_LEN(fraghdr)) - IPH_HL(fraghdr) * 4; 00345 offset = (ntohs(IPH_OFFSET(fraghdr)) & IP_OFFMASK) * 8; 00346 00347 /* overwrite the fragment's ip header from the pbuf with our helper struct, 00348 * and setup the embedded helper structure. */ 00349 /* make sure the struct ip_reass_helper fits into the IP header */ 00350 LWIP_ASSERT("sizeof(struct ip_reass_helper) <= IP_HLEN", 00351 sizeof(struct ip_reass_helper) <= IP_HLEN); 00352 iprh = (struct ip_reass_helper*)new_p->payload; 00353 iprh->next_pbuf = NULL; 00354 iprh->start = offset; 00355 iprh->end = offset + len; 00356 00357 /* Iterate through until we either get to the end of the list (append), 00358 * or we find on with a larger offset (insert). */ 00359 for (q = ipr->p; q != NULL;) { 00360 iprh_tmp = (struct ip_reass_helper*)q->payload; 00361 if (iprh->start < iprh_tmp->start) { 00362 /* the new pbuf should be inserted before this */ 00363 iprh->next_pbuf = q; 00364 if (iprh_prev != NULL) { 00365 /* not the fragment with the lowest offset */ 00366 #if IP_REASS_CHECK_OVERLAP 00367 if ((iprh->start < iprh_prev->end) || (iprh->end > iprh_tmp->start)) { 00368 /* fragment overlaps with previous or following, throw away */ 00369 goto freepbuf; 00370 } 00371 #endif /* IP_REASS_CHECK_OVERLAP */ 00372 iprh_prev->next_pbuf = new_p; 00373 } else { 00374 /* fragment with the lowest offset */ 00375 ipr->p = new_p; 00376 } 00377 break; 00378 } else if(iprh->start == iprh_tmp->start) { 00379 /* received the same datagram twice: no need to keep the datagram */ 00380 goto freepbuf; 00381 #if IP_REASS_CHECK_OVERLAP 00382 } else if(iprh->start < iprh_tmp->end) { 00383 /* overlap: no need to keep the new datagram */ 00384 goto freepbuf; 00385 #endif /* IP_REASS_CHECK_OVERLAP */ 00386 } else { 00387 /* Check if the fragments received so far have no wholes. */ 00388 if (iprh_prev != NULL) { 00389 if (iprh_prev->end != iprh_tmp->start) { 00390 /* There is a fragment missing between the current 00391 * and the previous fragment */ 00392 valid = 0; 00393 } 00394 } 00395 } 00396 q = iprh_tmp->next_pbuf; 00397 iprh_prev = iprh_tmp; 00398 } 00399 00400 /* If q is NULL, then we made it to the end of the list. Determine what to do now */ 00401 if (q == NULL) { 00402 if (iprh_prev != NULL) { 00403 /* this is (for now), the fragment with the highest offset: 00404 * chain it to the last fragment */ 00405 #if IP_REASS_CHECK_OVERLAP 00406 LWIP_ASSERT("check fragments don't overlap", iprh_prev->end <= iprh->start); 00407 #endif /* IP_REASS_CHECK_OVERLAP */ 00408 iprh_prev->next_pbuf = new_p; 00409 if (iprh_prev->end != iprh->start) { 00410 valid = 0; 00411 } 00412 } else { 00413 #if IP_REASS_CHECK_OVERLAP 00414 LWIP_ASSERT("no previous fragment, this must be the first fragment!", 00415 ipr->p == NULL); 00416 #endif /* IP_REASS_CHECK_OVERLAP */ 00417 /* this is the first fragment we ever received for this ip datagram */ 00418 ipr->p = new_p; 00419 } 00420 } 00421 00422 /* At this point, the validation part begins: */ 00423 /* If we already received the last fragment */ 00424 if ((ipr->flags & IP_REASS_FLAG_LASTFRAG) != 0) { 00425 /* and had no wholes so far */ 00426 if (valid) { 00427 /* then check if the rest of the fragments is here */ 00428 /* Check if the queue starts with the first datagram */ 00429 if (((struct ip_reass_helper*)ipr->p->payload)->start != 0) { 00430 valid = 0; 00431 } else { 00432 /* and check that there are no wholes after this datagram */ 00433 iprh_prev = iprh; 00434 q = iprh->next_pbuf; 00435 while (q != NULL) { 00436 iprh = (struct ip_reass_helper*)q->payload; 00437 if (iprh_prev->end != iprh->start) { 00438 valid = 0; 00439 break; 00440 } 00441 iprh_prev = iprh; 00442 q = iprh->next_pbuf; 00443 } 00444 /* if still valid, all fragments are received 00445 * (because to the MF==0 already arrived */ 00446 if (valid) { 00447 LWIP_ASSERT("sanity check", ipr->p != NULL); 00448 LWIP_ASSERT("sanity check", 00449 ((struct ip_reass_helper*)ipr->p->payload) != iprh); 00450 LWIP_ASSERT("validate_datagram:next_pbuf!=NULL", 00451 iprh->next_pbuf == NULL); 00452 LWIP_ASSERT("validate_datagram:datagram end!=datagram len", 00453 iprh->end == ipr->datagram_len); 00454 } 00455 } 00456 } 00457 /* If valid is 0 here, there are some fragments missing in the middle 00458 * (since MF == 0 has already arrived). Such datagrams simply time out if 00459 * no more fragments are received... */ 00460 return valid; 00461 } 00462 /* If we come here, not all fragments were received, yet! */ 00463 return 0; /* not yet valid! */ 00464 #if IP_REASS_CHECK_OVERLAP 00465 freepbuf: 00466 ip_reass_pbufcount -= pbuf_clen(new_p); 00467 pbuf_free(new_p); 00468 return 0; 00469 #endif /* IP_REASS_CHECK_OVERLAP */ 00470 } 00471 00472 /** 00473 * Reassembles incoming IP fragments into an IP datagram. 00474 * 00475 * @param p points to a pbuf chain of the fragment 00476 * @return NULL if reassembly is incomplete, ? otherwise 00477 */ 00478 struct pbuf * 00479 ip_reass(struct pbuf *p) 00480 { 00481 struct pbuf *r; 00482 struct ip_hdr *fraghdr; 00483 struct ip_reassdata *ipr; 00484 struct ip_reass_helper *iprh; 00485 u16_t offset, len; 00486 u8_t clen; 00487 struct ip_reassdata *ipr_prev = NULL; 00488 00489 IPFRAG_STATS_INC(ip_frag.recv); 00490 snmp_inc_ipreasmreqds(); 00491 00492 fraghdr = (struct ip_hdr*)p->payload; 00493 00494 if ((IPH_HL(fraghdr) * 4) != IP_HLEN) { 00495 LWIP_DEBUGF(IP_REASS_DEBUG,("ip_reass: IP options currently not supported!\n")); 00496 IPFRAG_STATS_INC(ip_frag.err); 00497 goto nullreturn; 00498 } 00499 00500 offset = (ntohs(IPH_OFFSET(fraghdr)) & IP_OFFMASK) * 8; 00501 len = ntohs(IPH_LEN(fraghdr)) - IPH_HL(fraghdr) * 4; 00502 00503 /* Check if we are allowed to enqueue more datagrams. */ 00504 clen = pbuf_clen(p); 00505 if ((ip_reass_pbufcount + clen) > IP_REASS_MAX_PBUFS) { 00506 #if IP_REASS_FREE_OLDEST 00507 if (!ip_reass_remove_oldest_datagram(fraghdr, clen) || 00508 ((ip_reass_pbufcount + clen) > IP_REASS_MAX_PBUFS)) 00509 #endif /* IP_REASS_FREE_OLDEST */ 00510 { 00511 /* No datagram could be freed and still too many pbufs enqueued */ 00512 LWIP_DEBUGF(IP_REASS_DEBUG,("ip_reass: Overflow condition: pbufct=%d, clen=%d, MAX=%d\n", 00513 ip_reass_pbufcount, clen, IP_REASS_MAX_PBUFS)); 00514 IPFRAG_STATS_INC(ip_frag.memerr); 00515 /* @todo: send ICMP time exceeded here? */ 00516 /* drop this pbuf */ 00517 goto nullreturn; 00518 } 00519 } 00520 00521 /* Look for the datagram the fragment belongs to in the current datagram queue, 00522 * remembering the previous in the queue for later dequeueing. */ 00523 for (ipr = reassdatagrams; ipr != NULL; ipr = ipr->next) { 00524 /* Check if the incoming fragment matches the one currently present 00525 in the reassembly buffer. If so, we proceed with copying the 00526 fragment into the buffer. */ 00527 if (IP_ADDRESSES_AND_ID_MATCH(&ipr->iphdr, fraghdr)) { 00528 LWIP_DEBUGF(IP_REASS_DEBUG, ("ip_reass: matching previous fragment ID=%"X16_F"\n", 00529 ntohs(IPH_ID(fraghdr)))); 00530 IPFRAG_STATS_INC(ip_frag.cachehit); 00531 break; 00532 } 00533 ipr_prev = ipr; 00534 } 00535 00536 if (ipr == NULL) { 00537 /* Enqueue a new datagram into the datagram queue */ 00538 ipr = ip_reass_enqueue_new_datagram(fraghdr, clen); 00539 /* Bail if unable to enqueue */ 00540 if(ipr == NULL) { 00541 goto nullreturn; 00542 } 00543 } else { 00544 if (((ntohs(IPH_OFFSET(fraghdr)) & IP_OFFMASK) == 0) && 00545 ((ntohs(IPH_OFFSET(&ipr->iphdr)) & IP_OFFMASK) != 0)) { 00546 /* ipr->iphdr is not the header from the first fragment, but fraghdr is 00547 * -> copy fraghdr into ipr->iphdr since we want to have the header 00548 * of the first fragment (for ICMP time exceeded and later, for copying 00549 * all options, if supported)*/ 00550 SMEMCPY(&ipr->iphdr, fraghdr, IP_HLEN); 00551 } 00552 } 00553 /* Track the current number of pbufs current 'in-flight', in order to limit 00554 the number of fragments that may be enqueued at any one time */ 00555 ip_reass_pbufcount += clen; 00556 00557 /* At this point, we have either created a new entry or pointing 00558 * to an existing one */ 00559 00560 /* check for 'no more fragments', and update queue entry*/ 00561 if ((ntohs(IPH_OFFSET(fraghdr)) & IP_MF) == 0) { 00562 ipr->flags |= IP_REASS_FLAG_LASTFRAG; 00563 ipr->datagram_len = offset + len; 00564 LWIP_DEBUGF(IP_REASS_DEBUG, 00565 ("ip_reass: last fragment seen, total len %"S16_F"\n", 00566 ipr->datagram_len)); 00567 } 00568 /* find the right place to insert this pbuf */ 00569 /* @todo: trim pbufs if fragments are overlapping */ 00570 if (ip_reass_chain_frag_into_datagram_and_validate(ipr, p)) { 00571 /* the totally last fragment (flag more fragments = 0) was received at least 00572 * once AND all fragments are received */ 00573 ipr->datagram_len += IP_HLEN; 00574 00575 /* save the second pbuf before copying the header over the pointer */ 00576 r = ((struct ip_reass_helper*)ipr->p->payload)->next_pbuf; 00577 00578 /* copy the original ip header back to the first pbuf */ 00579 fraghdr = (struct ip_hdr*)(ipr->p->payload); 00580 SMEMCPY(fraghdr, &ipr->iphdr, IP_HLEN); 00581 IPH_LEN_SET(fraghdr, htons(ipr->datagram_len)); 00582 IPH_OFFSET_SET(fraghdr, 0); 00583 IPH_CHKSUM_SET(fraghdr, 0); 00584 /* @todo: do we need to set calculate the correct checksum? */ 00585 IPH_CHKSUM_SET(fraghdr, inet_chksum(fraghdr, IP_HLEN)); 00586 00587 p = ipr->p; 00588 00589 /* chain together the pbufs contained within the reass_data list. */ 00590 while(r != NULL) { 00591 iprh = (struct ip_reass_helper*)r->payload; 00592 00593 /* hide the ip header for every succeding fragment */ 00594 pbuf_header(r, -IP_HLEN); 00595 pbuf_cat(p, r); 00596 r = iprh->next_pbuf; 00597 } 00598 /* release the sources allocate for the fragment queue entry */ 00599 ip_reass_dequeue_datagram(ipr, ipr_prev); 00600 00601 /* and adjust the number of pbufs currently queued for reassembly. */ 00602 ip_reass_pbufcount -= pbuf_clen(p); 00603 00604 /* Return the pbuf chain */ 00605 return p; 00606 } 00607 /* the datagram is not (yet?) reassembled completely */ 00608 LWIP_DEBUGF(IP_REASS_DEBUG,("ip_reass_pbufcount: %d out\n", ip_reass_pbufcount)); 00609 return NULL; 00610 00611 nullreturn: 00612 LWIP_DEBUGF(IP_REASS_DEBUG,("ip_reass: nullreturn\n")); 00613 IPFRAG_STATS_INC(ip_frag.drop); 00614 pbuf_free(p); 00615 return NULL; 00616 } 00617 #endif /* IP_REASSEMBLY */ 00618 00619 #if IP_FRAG 00620 #if IP_FRAG_USES_STATIC_BUF 00621 static u8_t buf[LWIP_MEM_ALIGN_SIZE(IP_FRAG_MAX_MTU + MEM_ALIGNMENT - 1)]; 00622 #endif /* IP_FRAG_USES_STATIC_BUF */ 00623 00624 /** 00625 * Fragment an IP datagram if too large for the netif. 00626 * 00627 * Chop the datagram in MTU sized chunks and send them in order 00628 * by using a fixed size static memory buffer (PBUF_REF) or 00629 * point PBUF_REFs into p (depending on IP_FRAG_USES_STATIC_BUF). 00630 * 00631 * @param p ip packet to send 00632 * @param netif the netif on which to send 00633 * @param dest destination ip address to which to send 00634 * 00635 * @return ERR_OK if sent successfully, err_t otherwise 00636 */ 00637 err_t 00638 ip_frag(struct pbuf *p, struct netif *netif, struct ip_addr *dest) 00639 { 00640 struct pbuf *rambuf; 00641 #if IP_FRAG_USES_STATIC_BUF 00642 struct pbuf *header; 00643 #else 00644 struct pbuf *newpbuf; 00645 struct ip_hdr *original_iphdr; 00646 #endif 00647 struct ip_hdr *iphdr; 00648 u16_t nfb; 00649 u16_t left, cop; 00650 u16_t mtu = netif->mtu; 00651 u16_t ofo, omf; 00652 u16_t last; 00653 u16_t poff = IP_HLEN; 00654 u16_t tmp; 00655 #if !IP_FRAG_USES_STATIC_BUF 00656 u16_t newpbuflen = 0; 00657 u16_t left_to_copy; 00658 #endif 00659 00660 /* Get a RAM based MTU sized pbuf */ 00661 #if IP_FRAG_USES_STATIC_BUF 00662 /* When using a static buffer, we use a PBUF_REF, which we will 00663 * use to reference the packet (without link header). 00664 * Layer and length is irrelevant. 00665 */ 00666 rambuf = pbuf_alloc(PBUF_LINK, 0, PBUF_REF); 00667 if (rambuf == NULL) { 00668 LWIP_DEBUGF(IP_REASS_DEBUG, ("ip_frag: pbuf_alloc(PBUF_LINK, 0, PBUF_REF) failed\n")); 00669 return ERR_MEM; 00670 } 00671 rambuf->tot_len = rambuf->len = mtu; 00672 rambuf->payload = LWIP_MEM_ALIGN((void *)buf); 00673 00674 /* Copy the IP header in it */ 00675 iphdr = (struct ip_hdr *)(rambuf->payload); // static_cast<struct ip_hdr *>(x) 00676 SMEMCPY(iphdr, p->payload, IP_HLEN); 00677 #else /* IP_FRAG_USES_STATIC_BUF */ 00678 original_iphdr = (struct ip_hdr *)p->payload; 00679 iphdr = original_iphdr; 00680 #endif /* IP_FRAG_USES_STATIC_BUF */ 00681 00682 /* Save original offset */ 00683 tmp = ntohs(IPH_OFFSET(iphdr)); 00684 ofo = tmp & IP_OFFMASK; 00685 omf = tmp & IP_MF; 00686 00687 left = p->tot_len - IP_HLEN; 00688 00689 nfb = (mtu - IP_HLEN) / 8; 00690 00691 while (left) { 00692 last = (left <= mtu - IP_HLEN); 00693 00694 /* Set new offset and MF flag */ 00695 tmp = omf | (IP_OFFMASK & (ofo)); 00696 if (!last) 00697 tmp = tmp | IP_MF; 00698 00699 /* Fill this fragment */ 00700 cop = last ? left : nfb * 8; 00701 00702 #if IP_FRAG_USES_STATIC_BUF 00703 poff += pbuf_copy_partial(p, (u8_t*)iphdr + IP_HLEN, cop, poff); 00704 #else /* IP_FRAG_USES_STATIC_BUF */ 00705 /* When not using a static buffer, create a chain of pbufs. 00706 * The first will be a PBUF_RAM holding the link and IP header. 00707 * The rest will be PBUF_REFs mirroring the pbuf chain to be fragged, 00708 * but limited to the size of an mtu. 00709 */ 00710 rambuf = pbuf_alloc(PBUF_LINK, IP_HLEN, PBUF_RAM); 00711 if (rambuf == NULL) { 00712 return ERR_MEM; 00713 } 00714 LWIP_ASSERT("this needs a pbuf in one piece!", 00715 (p->len >= (IP_HLEN))); 00716 SMEMCPY(rambuf->payload, original_iphdr, IP_HLEN); 00717 iphdr = (struct ip_hdr *)rambuf->payload; 00718 00719 /* Can just adjust p directly for needed offset. */ 00720 p->payload = (u8_t *)p->payload + poff; 00721 p->len -= poff; 00722 00723 left_to_copy = cop; 00724 while (left_to_copy) { 00725 newpbuflen = (left_to_copy < p->len) ? left_to_copy : p->len; 00726 /* Is this pbuf already empty? */ 00727 if (!newpbuflen) { 00728 p = p->next; 00729 continue; 00730 } 00731 newpbuf = pbuf_alloc(PBUF_RAW, 0, PBUF_REF); 00732 if (newpbuf == NULL) { 00733 pbuf_free(rambuf); 00734 return ERR_MEM; 00735 } 00736 /* Mirror this pbuf, although we might not need all of it. */ 00737 newpbuf->payload = p->payload; 00738 newpbuf->len = newpbuf->tot_len = newpbuflen; 00739 /* Add it to end of rambuf's chain, but using pbuf_cat, not pbuf_chain 00740 * so that it is removed when pbuf_dechain is later called on rambuf. 00741 */ 00742 pbuf_cat(rambuf, newpbuf); 00743 left_to_copy -= newpbuflen; 00744 if (left_to_copy) 00745 p = p->next; 00746 } 00747 poff = newpbuflen; 00748 #endif /* IP_FRAG_USES_STATIC_BUF */ 00749 00750 /* Correct header */ 00751 IPH_OFFSET_SET(iphdr, htons(tmp)); 00752 IPH_LEN_SET(iphdr, htons(cop + IP_HLEN)); 00753 IPH_CHKSUM_SET(iphdr, 0); 00754 IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, IP_HLEN)); 00755 00756 #if IP_FRAG_USES_STATIC_BUF 00757 if (last) 00758 pbuf_realloc(rambuf, left + IP_HLEN); 00759 00760 /* This part is ugly: we alloc a RAM based pbuf for 00761 * the link level header for each chunk and then 00762 * free it.A PBUF_ROM style pbuf for which pbuf_header 00763 * worked would make things simpler. 00764 */ 00765 header = pbuf_alloc(PBUF_LINK, 0, PBUF_RAM); 00766 if (header != NULL) { 00767 pbuf_chain(header, rambuf); 00768 netif->output(netif, header, dest); 00769 IPFRAG_STATS_INC(ip_frag.xmit); 00770 snmp_inc_ipfragcreates(); 00771 pbuf_free(header); 00772 } else { 00773 LWIP_DEBUGF(IP_REASS_DEBUG, ("ip_frag: pbuf_alloc() for header failed\n")); 00774 pbuf_free(rambuf); 00775 return ERR_MEM; 00776 } 00777 #else /* IP_FRAG_USES_STATIC_BUF */ 00778 /* No need for separate header pbuf - we allowed room for it in rambuf 00779 * when allocated. 00780 */ 00781 netif->output(netif, rambuf, dest); 00782 IPFRAG_STATS_INC(ip_frag.xmit); 00783 00784 /* Unfortunately we can't reuse rambuf - the hardware may still be 00785 * using the buffer. Instead we free it (and the ensuing chain) and 00786 * recreate it next time round the loop. If we're lucky the hardware 00787 * will have already sent the packet, the free will really free, and 00788 * there will be zero memory penalty. 00789 */ 00790 00791 pbuf_free(rambuf); 00792 #endif /* IP_FRAG_USES_STATIC_BUF */ 00793 left -= cop; 00794 ofo += nfb; 00795 } 00796 #if IP_FRAG_USES_STATIC_BUF 00797 pbuf_free(rambuf); 00798 #endif /* IP_FRAG_USES_STATIC_BUF */ 00799 snmp_inc_ipfragoks(); 00800 return ERR_OK; 00801 } 00802 #endif /* IP_FRAG */
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