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core/ipv4/ip_frag.c
- Committer:
- mbed_official
- Date:
- 2012-06-22
- Revision:
- 0:51ac1d130fd4
File content as of revision 0:51ac1d130fd4:
/** * @file * This is the IPv4 packet segmentation and reassembly implementation. * */ /* * Copyright (c) 2001-2004 Swedish Institute of Computer Science. * All rights reserved. * * Redistribution and use in source and binary forms, with or without modification, * are permitted provided that the following conditions are met: * * 1. Redistributions of source code must retain the above copyright notice, * this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright notice, * this list of conditions and the following disclaimer in the documentation * and/or other materials provided with the distribution. * 3. The name of the author may not be used to endorse or promote products * derived from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY * OF SUCH DAMAGE. * * This file is part of the lwIP TCP/IP stack. * * Author: Jani Monoses <jani@iv.ro> * Simon Goldschmidt * original reassembly code by Adam Dunkels <adam@sics.se> * */ #include "lwip/opt.h" #include "lwip/ip_frag.h" #include "lwip/def.h" #include "lwip/inet_chksum.h" #include "lwip/netif.h" #include "lwip/snmp.h" #include "lwip/stats.h" #include "lwip/icmp.h" #include <string.h> #if IP_REASSEMBLY /** * The IP reassembly code currently has the following limitations: * - IP header options are not supported * - fragments must not overlap (e.g. due to different routes), * currently, overlapping or duplicate fragments are thrown away * if IP_REASS_CHECK_OVERLAP=1 (the default)! * * @todo: work with IP header options */ /** Setting this to 0, you can turn off checking the fragments for overlapping * regions. The code gets a little smaller. Only use this if you know that * overlapping won't occur on your network! */ #ifndef IP_REASS_CHECK_OVERLAP #define IP_REASS_CHECK_OVERLAP 1 #endif /* IP_REASS_CHECK_OVERLAP */ /** Set to 0 to prevent freeing the oldest datagram when the reassembly buffer is * full (IP_REASS_MAX_PBUFS pbufs are enqueued). The code gets a little smaller. * Datagrams will be freed by timeout only. Especially useful when MEMP_NUM_REASSDATA * is set to 1, so one datagram can be reassembled at a time, only. */ #ifndef IP_REASS_FREE_OLDEST #define IP_REASS_FREE_OLDEST 1 #endif /* IP_REASS_FREE_OLDEST */ #define IP_REASS_FLAG_LASTFRAG 0x01 /** This is a helper struct which holds the starting * offset and the ending offset of this fragment to * easily chain the fragments. * It has the same packing requirements as the IP header, since it replaces * the IP header in memory in incoming fragments (after copying it) to keep * track of the various fragments. (-> If the IP header doesn't need packing, * this struct doesn't need packing, too.) */ #ifdef PACK_STRUCT_USE_INCLUDES # include "arch/bpstruct.h" #endif PACK_STRUCT_BEGIN struct ip_reass_helper { PACK_STRUCT_FIELD(struct pbuf *next_pbuf); PACK_STRUCT_FIELD(u16_t start); PACK_STRUCT_FIELD(u16_t end); } PACK_STRUCT_STRUCT; PACK_STRUCT_END #ifdef PACK_STRUCT_USE_INCLUDES # include "arch/epstruct.h" #endif #define IP_ADDRESSES_AND_ID_MATCH(iphdrA, iphdrB) \ (ip_addr_cmp(&(iphdrA)->src, &(iphdrB)->src) && \ ip_addr_cmp(&(iphdrA)->dest, &(iphdrB)->dest) && \ IPH_ID(iphdrA) == IPH_ID(iphdrB)) ? 1 : 0 /* global variables */ static struct ip_reassdata *reassdatagrams; static u16_t ip_reass_pbufcount; /* function prototypes */ static void ip_reass_dequeue_datagram(struct ip_reassdata *ipr, struct ip_reassdata *prev); static int ip_reass_free_complete_datagram(struct ip_reassdata *ipr, struct ip_reassdata *prev); /** * Reassembly timer base function * for both NO_SYS == 0 and 1 (!). * * Should be called every 1000 msec (defined by IP_TMR_INTERVAL). */ void ip_reass_tmr(void) { struct ip_reassdata *r, *prev = NULL; r = reassdatagrams; while (r != NULL) { /* Decrement the timer. Once it reaches 0, * clean up the incomplete fragment assembly */ if (r->timer > 0) { r->timer--; LWIP_DEBUGF(IP_REASS_DEBUG, ("ip_reass_tmr: timer dec %"U16_F"\n",(u16_t)r->timer)); prev = r; r = r->next; } else { /* reassembly timed out */ struct ip_reassdata *tmp; LWIP_DEBUGF(IP_REASS_DEBUG, ("ip_reass_tmr: timer timed out\n")); tmp = r; /* get the next pointer before freeing */ r = r->next; /* free the helper struct and all enqueued pbufs */ ip_reass_free_complete_datagram(tmp, prev); } } } /** * Free a datagram (struct ip_reassdata) and all its pbufs. * Updates the total count of enqueued pbufs (ip_reass_pbufcount), * SNMP counters and sends an ICMP time exceeded packet. * * @param ipr datagram to free * @param prev the previous datagram in the linked list * @return the number of pbufs freed */ static int ip_reass_free_complete_datagram(struct ip_reassdata *ipr, struct ip_reassdata *prev) { u16_t pbufs_freed = 0; u8_t clen; struct pbuf *p; struct ip_reass_helper *iprh; LWIP_ASSERT("prev != ipr", prev != ipr); if (prev != NULL) { LWIP_ASSERT("prev->next == ipr", prev->next == ipr); } snmp_inc_ipreasmfails(); #if LWIP_ICMP iprh = (struct ip_reass_helper *)ipr->p->payload; if (iprh->start == 0) { /* The first fragment was received, send ICMP time exceeded. */ /* First, de-queue the first pbuf from r->p. */ p = ipr->p; ipr->p = iprh->next_pbuf; /* Then, copy the original header into it. */ SMEMCPY(p->payload, &ipr->iphdr, IP_HLEN); icmp_time_exceeded(p, ICMP_TE_FRAG); clen = pbuf_clen(p); LWIP_ASSERT("pbufs_freed + clen <= 0xffff", pbufs_freed + clen <= 0xffff); pbufs_freed += clen; pbuf_free(p); } #endif /* LWIP_ICMP */ /* First, free all received pbufs. The individual pbufs need to be released separately as they have not yet been chained */ p = ipr->p; while (p != NULL) { struct pbuf *pcur; iprh = (struct ip_reass_helper *)p->payload; pcur = p; /* get the next pointer before freeing */ p = iprh->next_pbuf; clen = pbuf_clen(pcur); LWIP_ASSERT("pbufs_freed + clen <= 0xffff", pbufs_freed + clen <= 0xffff); pbufs_freed += clen; pbuf_free(pcur); } /* Then, unchain the struct ip_reassdata from the list and free it. */ ip_reass_dequeue_datagram(ipr, prev); LWIP_ASSERT("ip_reass_pbufcount >= clen", ip_reass_pbufcount >= pbufs_freed); ip_reass_pbufcount -= pbufs_freed; return pbufs_freed; } #if IP_REASS_FREE_OLDEST /** * Free the oldest datagram to make room for enqueueing new fragments. * The datagram 'fraghdr' belongs to is not freed! * * @param fraghdr IP header of the current fragment * @param pbufs_needed number of pbufs needed to enqueue * (used for freeing other datagrams if not enough space) * @return the number of pbufs freed */ static int ip_reass_remove_oldest_datagram(struct ip_hdr *fraghdr, int pbufs_needed) { /* @todo Can't we simply remove the last datagram in the * linked list behind reassdatagrams? */ struct ip_reassdata *r, *oldest, *prev; int pbufs_freed = 0, pbufs_freed_current; int other_datagrams; /* Free datagrams until being allowed to enqueue 'pbufs_needed' pbufs, * but don't free the datagram that 'fraghdr' belongs to! */ do { oldest = NULL; prev = NULL; other_datagrams = 0; r = reassdatagrams; while (r != NULL) { if (!IP_ADDRESSES_AND_ID_MATCH(&r->iphdr, fraghdr)) { /* Not the same datagram as fraghdr */ other_datagrams++; if (oldest == NULL) { oldest = r; } else if (r->timer <= oldest->timer) { /* older than the previous oldest */ oldest = r; } } if (r->next != NULL) { prev = r; } r = r->next; } if (oldest != NULL) { pbufs_freed_current = ip_reass_free_complete_datagram(oldest, prev); pbufs_freed += pbufs_freed_current; } } while ((pbufs_freed < pbufs_needed) && (other_datagrams > 1)); return pbufs_freed; } #endif /* IP_REASS_FREE_OLDEST */ /** * Enqueues a new fragment into the fragment queue * @param fraghdr points to the new fragments IP hdr * @param clen number of pbufs needed to enqueue (used for freeing other datagrams if not enough space) * @return A pointer to the queue location into which the fragment was enqueued */ static struct ip_reassdata* ip_reass_enqueue_new_datagram(struct ip_hdr *fraghdr, int clen) { struct ip_reassdata* ipr; /* No matching previous fragment found, allocate a new reassdata struct */ ipr = (struct ip_reassdata *)memp_malloc(MEMP_REASSDATA); if (ipr == NULL) { #if IP_REASS_FREE_OLDEST if (ip_reass_remove_oldest_datagram(fraghdr, clen) >= clen) { ipr = (struct ip_reassdata *)memp_malloc(MEMP_REASSDATA); } if (ipr == NULL) #endif /* IP_REASS_FREE_OLDEST */ { IPFRAG_STATS_INC(ip_frag.memerr); LWIP_DEBUGF(IP_REASS_DEBUG,("Failed to alloc reassdata struct\n")); return NULL; } } memset(ipr, 0, sizeof(struct ip_reassdata)); ipr->timer = IP_REASS_MAXAGE; /* enqueue the new structure to the front of the list */ ipr->next = reassdatagrams; reassdatagrams = ipr; /* copy the ip header for later tests and input */ /* @todo: no ip options supported? */ SMEMCPY(&(ipr->iphdr), fraghdr, IP_HLEN); return ipr; } /** * Dequeues a datagram from the datagram queue. Doesn't deallocate the pbufs. * @param ipr points to the queue entry to dequeue */ static void ip_reass_dequeue_datagram(struct ip_reassdata *ipr, struct ip_reassdata *prev) { /* dequeue the reass struct */ if (reassdatagrams == ipr) { /* it was the first in the list */ reassdatagrams = ipr->next; } else { /* it wasn't the first, so it must have a valid 'prev' */ LWIP_ASSERT("sanity check linked list", prev != NULL); prev->next = ipr->next; } /* now we can free the ip_reass struct */ memp_free(MEMP_REASSDATA, ipr); } /** * Chain a new pbuf into the pbuf list that composes the datagram. The pbuf list * will grow over time as new pbufs are rx. * Also checks that the datagram passes basic continuity checks (if the last * fragment was received at least once). * @param root_p points to the 'root' pbuf for the current datagram being assembled. * @param new_p points to the pbuf for the current fragment * @return 0 if invalid, >0 otherwise */ static int ip_reass_chain_frag_into_datagram_and_validate(struct ip_reassdata *ipr, struct pbuf *new_p) { struct ip_reass_helper *iprh, *iprh_tmp, *iprh_prev=NULL; struct pbuf *q; u16_t offset,len; struct ip_hdr *fraghdr; int valid = 1; /* Extract length and fragment offset from current fragment */ fraghdr = (struct ip_hdr*)new_p->payload; len = ntohs(IPH_LEN(fraghdr)) - IPH_HL(fraghdr) * 4; offset = (ntohs(IPH_OFFSET(fraghdr)) & IP_OFFMASK) * 8; /* overwrite the fragment's ip header from the pbuf with our helper struct, * and setup the embedded helper structure. */ /* make sure the struct ip_reass_helper fits into the IP header */ LWIP_ASSERT("sizeof(struct ip_reass_helper) <= IP_HLEN", sizeof(struct ip_reass_helper) <= IP_HLEN); iprh = (struct ip_reass_helper*)new_p->payload; iprh->next_pbuf = NULL; iprh->start = offset; iprh->end = offset + len; /* Iterate through until we either get to the end of the list (append), * or we find on with a larger offset (insert). */ for (q = ipr->p; q != NULL;) { iprh_tmp = (struct ip_reass_helper*)q->payload; if (iprh->start < iprh_tmp->start) { /* the new pbuf should be inserted before this */ iprh->next_pbuf = q; if (iprh_prev != NULL) { /* not the fragment with the lowest offset */ #if IP_REASS_CHECK_OVERLAP if ((iprh->start < iprh_prev->end) || (iprh->end > iprh_tmp->start)) { /* fragment overlaps with previous or following, throw away */ goto freepbuf; } #endif /* IP_REASS_CHECK_OVERLAP */ iprh_prev->next_pbuf = new_p; } else { /* fragment with the lowest offset */ ipr->p = new_p; } break; } else if(iprh->start == iprh_tmp->start) { /* received the same datagram twice: no need to keep the datagram */ goto freepbuf; #if IP_REASS_CHECK_OVERLAP } else if(iprh->start < iprh_tmp->end) { /* overlap: no need to keep the new datagram */ goto freepbuf; #endif /* IP_REASS_CHECK_OVERLAP */ } else { /* Check if the fragments received so far have no wholes. */ if (iprh_prev != NULL) { if (iprh_prev->end != iprh_tmp->start) { /* There is a fragment missing between the current * and the previous fragment */ valid = 0; } } } q = iprh_tmp->next_pbuf; iprh_prev = iprh_tmp; } /* If q is NULL, then we made it to the end of the list. Determine what to do now */ if (q == NULL) { if (iprh_prev != NULL) { /* this is (for now), the fragment with the highest offset: * chain it to the last fragment */ #if IP_REASS_CHECK_OVERLAP LWIP_ASSERT("check fragments don't overlap", iprh_prev->end <= iprh->start); #endif /* IP_REASS_CHECK_OVERLAP */ iprh_prev->next_pbuf = new_p; if (iprh_prev->end != iprh->start) { valid = 0; } } else { #if IP_REASS_CHECK_OVERLAP LWIP_ASSERT("no previous fragment, this must be the first fragment!", ipr->p == NULL); #endif /* IP_REASS_CHECK_OVERLAP */ /* this is the first fragment we ever received for this ip datagram */ ipr->p = new_p; } } /* At this point, the validation part begins: */ /* If we already received the last fragment */ if ((ipr->flags & IP_REASS_FLAG_LASTFRAG) != 0) { /* and had no wholes so far */ if (valid) { /* then check if the rest of the fragments is here */ /* Check if the queue starts with the first datagram */ if (((struct ip_reass_helper*)ipr->p->payload)->start != 0) { valid = 0; } else { /* and check that there are no wholes after this datagram */ iprh_prev = iprh; q = iprh->next_pbuf; while (q != NULL) { iprh = (struct ip_reass_helper*)q->payload; if (iprh_prev->end != iprh->start) { valid = 0; break; } iprh_prev = iprh; q = iprh->next_pbuf; } /* if still valid, all fragments are received * (because to the MF==0 already arrived */ if (valid) { LWIP_ASSERT("sanity check", ipr->p != NULL); LWIP_ASSERT("sanity check", ((struct ip_reass_helper*)ipr->p->payload) != iprh); LWIP_ASSERT("validate_datagram:next_pbuf!=NULL", iprh->next_pbuf == NULL); LWIP_ASSERT("validate_datagram:datagram end!=datagram len", iprh->end == ipr->datagram_len); } } } /* If valid is 0 here, there are some fragments missing in the middle * (since MF == 0 has already arrived). Such datagrams simply time out if * no more fragments are received... */ return valid; } /* If we come here, not all fragments were received, yet! */ return 0; /* not yet valid! */ #if IP_REASS_CHECK_OVERLAP freepbuf: ip_reass_pbufcount -= pbuf_clen(new_p); pbuf_free(new_p); return 0; #endif /* IP_REASS_CHECK_OVERLAP */ } /** * Reassembles incoming IP fragments into an IP datagram. * * @param p points to a pbuf chain of the fragment * @return NULL if reassembly is incomplete, ? otherwise */ struct pbuf * ip_reass(struct pbuf *p) { struct pbuf *r; struct ip_hdr *fraghdr; struct ip_reassdata *ipr; struct ip_reass_helper *iprh; u16_t offset, len; u8_t clen; struct ip_reassdata *ipr_prev = NULL; IPFRAG_STATS_INC(ip_frag.recv); snmp_inc_ipreasmreqds(); fraghdr = (struct ip_hdr*)p->payload; if ((IPH_HL(fraghdr) * 4) != IP_HLEN) { LWIP_DEBUGF(IP_REASS_DEBUG,("ip_reass: IP options currently not supported!\n")); IPFRAG_STATS_INC(ip_frag.err); goto nullreturn; } offset = (ntohs(IPH_OFFSET(fraghdr)) & IP_OFFMASK) * 8; len = ntohs(IPH_LEN(fraghdr)) - IPH_HL(fraghdr) * 4; /* Check if we are allowed to enqueue more datagrams. */ clen = pbuf_clen(p); if ((ip_reass_pbufcount + clen) > IP_REASS_MAX_PBUFS) { #if IP_REASS_FREE_OLDEST if (!ip_reass_remove_oldest_datagram(fraghdr, clen) || ((ip_reass_pbufcount + clen) > IP_REASS_MAX_PBUFS)) #endif /* IP_REASS_FREE_OLDEST */ { /* No datagram could be freed and still too many pbufs enqueued */ LWIP_DEBUGF(IP_REASS_DEBUG,("ip_reass: Overflow condition: pbufct=%d, clen=%d, MAX=%d\n", ip_reass_pbufcount, clen, IP_REASS_MAX_PBUFS)); IPFRAG_STATS_INC(ip_frag.memerr); /* @todo: send ICMP time exceeded here? */ /* drop this pbuf */ goto nullreturn; } } /* Look for the datagram the fragment belongs to in the current datagram queue, * remembering the previous in the queue for later dequeueing. */ for (ipr = reassdatagrams; ipr != NULL; ipr = ipr->next) { /* Check if the incoming fragment matches the one currently present in the reassembly buffer. If so, we proceed with copying the fragment into the buffer. */ if (IP_ADDRESSES_AND_ID_MATCH(&ipr->iphdr, fraghdr)) { LWIP_DEBUGF(IP_REASS_DEBUG, ("ip_reass: matching previous fragment ID=%"X16_F"\n", ntohs(IPH_ID(fraghdr)))); IPFRAG_STATS_INC(ip_frag.cachehit); break; } ipr_prev = ipr; } if (ipr == NULL) { /* Enqueue a new datagram into the datagram queue */ ipr = ip_reass_enqueue_new_datagram(fraghdr, clen); /* Bail if unable to enqueue */ if(ipr == NULL) { goto nullreturn; } } else { if (((ntohs(IPH_OFFSET(fraghdr)) & IP_OFFMASK) == 0) && ((ntohs(IPH_OFFSET(&ipr->iphdr)) & IP_OFFMASK) != 0)) { /* ipr->iphdr is not the header from the first fragment, but fraghdr is * -> copy fraghdr into ipr->iphdr since we want to have the header * of the first fragment (for ICMP time exceeded and later, for copying * all options, if supported)*/ SMEMCPY(&ipr->iphdr, fraghdr, IP_HLEN); } } /* Track the current number of pbufs current 'in-flight', in order to limit the number of fragments that may be enqueued at any one time */ ip_reass_pbufcount += clen; /* At this point, we have either created a new entry or pointing * to an existing one */ /* check for 'no more fragments', and update queue entry*/ if ((IPH_OFFSET(fraghdr) & PP_NTOHS(IP_MF)) == 0) { ipr->flags |= IP_REASS_FLAG_LASTFRAG; ipr->datagram_len = offset + len; LWIP_DEBUGF(IP_REASS_DEBUG, ("ip_reass: last fragment seen, total len %"S16_F"\n", ipr->datagram_len)); } /* find the right place to insert this pbuf */ /* @todo: trim pbufs if fragments are overlapping */ if (ip_reass_chain_frag_into_datagram_and_validate(ipr, p)) { /* the totally last fragment (flag more fragments = 0) was received at least * once AND all fragments are received */ ipr->datagram_len += IP_HLEN; /* save the second pbuf before copying the header over the pointer */ r = ((struct ip_reass_helper*)ipr->p->payload)->next_pbuf; /* copy the original ip header back to the first pbuf */ fraghdr = (struct ip_hdr*)(ipr->p->payload); SMEMCPY(fraghdr, &ipr->iphdr, IP_HLEN); IPH_LEN_SET(fraghdr, htons(ipr->datagram_len)); IPH_OFFSET_SET(fraghdr, 0); IPH_CHKSUM_SET(fraghdr, 0); /* @todo: do we need to set calculate the correct checksum? */ IPH_CHKSUM_SET(fraghdr, inet_chksum(fraghdr, IP_HLEN)); p = ipr->p; /* chain together the pbufs contained within the reass_data list. */ while(r != NULL) { iprh = (struct ip_reass_helper*)r->payload; /* hide the ip header for every succeding fragment */ pbuf_header(r, -IP_HLEN); pbuf_cat(p, r); r = iprh->next_pbuf; } /* release the sources allocate for the fragment queue entry */ ip_reass_dequeue_datagram(ipr, ipr_prev); /* and adjust the number of pbufs currently queued for reassembly. */ ip_reass_pbufcount -= pbuf_clen(p); /* Return the pbuf chain */ return p; } /* the datagram is not (yet?) reassembled completely */ LWIP_DEBUGF(IP_REASS_DEBUG,("ip_reass_pbufcount: %d out\n", ip_reass_pbufcount)); return NULL; nullreturn: LWIP_DEBUGF(IP_REASS_DEBUG,("ip_reass: nullreturn\n")); IPFRAG_STATS_INC(ip_frag.drop); pbuf_free(p); return NULL; } #endif /* IP_REASSEMBLY */ #if IP_FRAG #if IP_FRAG_USES_STATIC_BUF static u8_t buf[LWIP_MEM_ALIGN_SIZE(IP_FRAG_MAX_MTU + MEM_ALIGNMENT - 1)]; #else /* IP_FRAG_USES_STATIC_BUF */ #if !LWIP_NETIF_TX_SINGLE_PBUF /** Allocate a new struct pbuf_custom_ref */ static struct pbuf_custom_ref* ip_frag_alloc_pbuf_custom_ref(void) { return (struct pbuf_custom_ref*)memp_malloc(MEMP_FRAG_PBUF); } /** Free a struct pbuf_custom_ref */ static void ip_frag_free_pbuf_custom_ref(struct pbuf_custom_ref* p) { LWIP_ASSERT("p != NULL", p != NULL); memp_free(MEMP_FRAG_PBUF, p); } /** Free-callback function to free a 'struct pbuf_custom_ref', called by * pbuf_free. */ static void ipfrag_free_pbuf_custom(struct pbuf *p) { struct pbuf_custom_ref *pcr = (struct pbuf_custom_ref*)p; LWIP_ASSERT("pcr != NULL", pcr != NULL); LWIP_ASSERT("pcr == p", (void*)pcr == (void*)p); if (pcr->original != NULL) { pbuf_free(pcr->original); } ip_frag_free_pbuf_custom_ref(pcr); } #endif /* !LWIP_NETIF_TX_SINGLE_PBUF */ #endif /* IP_FRAG_USES_STATIC_BUF */ /** * Fragment an IP datagram if too large for the netif. * * Chop the datagram in MTU sized chunks and send them in order * by using a fixed size static memory buffer (PBUF_REF) or * point PBUF_REFs into p (depending on IP_FRAG_USES_STATIC_BUF). * * @param p ip packet to send * @param netif the netif on which to send * @param dest destination ip address to which to send * * @return ERR_OK if sent successfully, err_t otherwise */ err_t ip_frag(struct pbuf *p, struct netif *netif, ip_addr_t *dest) { struct pbuf *rambuf; #if IP_FRAG_USES_STATIC_BUF struct pbuf *header; #else #if !LWIP_NETIF_TX_SINGLE_PBUF struct pbuf *newpbuf; #endif struct ip_hdr *original_iphdr; #endif struct ip_hdr *iphdr; u16_t nfb; u16_t left, cop; u16_t mtu = netif->mtu; u16_t ofo, omf; u16_t last; u16_t poff = IP_HLEN; u16_t tmp; #if !IP_FRAG_USES_STATIC_BUF && !LWIP_NETIF_TX_SINGLE_PBUF u16_t newpbuflen = 0; u16_t left_to_copy; #endif /* Get a RAM based MTU sized pbuf */ #if IP_FRAG_USES_STATIC_BUF /* When using a static buffer, we use a PBUF_REF, which we will * use to reference the packet (without link header). * Layer and length is irrelevant. */ rambuf = pbuf_alloc(PBUF_LINK, 0, PBUF_REF); if (rambuf == NULL) { LWIP_DEBUGF(IP_REASS_DEBUG, ("ip_frag: pbuf_alloc(PBUF_LINK, 0, PBUF_REF) failed\n")); return ERR_MEM; } rambuf->tot_len = rambuf->len = mtu; rambuf->payload = LWIP_MEM_ALIGN((void *)buf); /* Copy the IP header in it */ iphdr = (struct ip_hdr *)rambuf->payload; SMEMCPY(iphdr, p->payload, IP_HLEN); #else /* IP_FRAG_USES_STATIC_BUF */ original_iphdr = (struct ip_hdr *)p->payload; iphdr = original_iphdr; #endif /* IP_FRAG_USES_STATIC_BUF */ /* Save original offset */ tmp = ntohs(IPH_OFFSET(iphdr)); ofo = tmp & IP_OFFMASK; omf = tmp & IP_MF; left = p->tot_len - IP_HLEN; nfb = (mtu - IP_HLEN) / 8; while (left) { last = (left <= mtu - IP_HLEN); /* Set new offset and MF flag */ tmp = omf | (IP_OFFMASK & (ofo)); if (!last) { tmp = tmp | IP_MF; } /* Fill this fragment */ cop = last ? left : nfb * 8; #if IP_FRAG_USES_STATIC_BUF poff += pbuf_copy_partial(p, (u8_t*)iphdr + IP_HLEN, cop, poff); #else /* IP_FRAG_USES_STATIC_BUF */ #if LWIP_NETIF_TX_SINGLE_PBUF rambuf = pbuf_alloc(PBUF_IP, cop, PBUF_RAM); if (rambuf == NULL) { return ERR_MEM; } LWIP_ASSERT("this needs a pbuf in one piece!", (rambuf->len == rambuf->tot_len) && (rambuf->next == NULL)); poff += pbuf_copy_partial(p, rambuf->payload, cop, poff); /* make room for the IP header */ if(pbuf_header(rambuf, IP_HLEN)) { pbuf_free(rambuf); return ERR_MEM; } /* fill in the IP header */ SMEMCPY(rambuf->payload, original_iphdr, IP_HLEN); iphdr = rambuf->payload; #else /* LWIP_NETIF_TX_SINGLE_PBUF */ /* When not using a static buffer, create a chain of pbufs. * The first will be a PBUF_RAM holding the link and IP header. * The rest will be PBUF_REFs mirroring the pbuf chain to be fragged, * but limited to the size of an mtu. */ rambuf = pbuf_alloc(PBUF_LINK, IP_HLEN, PBUF_RAM); if (rambuf == NULL) { return ERR_MEM; } LWIP_ASSERT("this needs a pbuf in one piece!", (p->len >= (IP_HLEN))); SMEMCPY(rambuf->payload, original_iphdr, IP_HLEN); iphdr = (struct ip_hdr *)rambuf->payload; /* Can just adjust p directly for needed offset. */ p->payload = (u8_t *)p->payload + poff; p->len -= poff; left_to_copy = cop; while (left_to_copy) { struct pbuf_custom_ref *pcr; newpbuflen = (left_to_copy < p->len) ? left_to_copy : p->len; /* Is this pbuf already empty? */ if (!newpbuflen) { p = p->next; continue; } pcr = ip_frag_alloc_pbuf_custom_ref(); if (pcr == NULL) { pbuf_free(rambuf); return ERR_MEM; } /* Mirror this pbuf, although we might not need all of it. */ newpbuf = pbuf_alloced_custom(PBUF_RAW, newpbuflen, PBUF_REF, &pcr->pc, p->payload, newpbuflen); if (newpbuf == NULL) { ip_frag_free_pbuf_custom_ref(pcr); pbuf_free(rambuf); return ERR_MEM; } pbuf_ref(p); pcr->original = p; pcr->pc.custom_free_function = ipfrag_free_pbuf_custom; /* Add it to end of rambuf's chain, but using pbuf_cat, not pbuf_chain * so that it is removed when pbuf_dechain is later called on rambuf. */ pbuf_cat(rambuf, newpbuf); left_to_copy -= newpbuflen; if (left_to_copy) { p = p->next; } } poff = newpbuflen; #endif /* LWIP_NETIF_TX_SINGLE_PBUF */ #endif /* IP_FRAG_USES_STATIC_BUF */ /* Correct header */ IPH_OFFSET_SET(iphdr, htons(tmp)); IPH_LEN_SET(iphdr, htons(cop + IP_HLEN)); IPH_CHKSUM_SET(iphdr, 0); IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, IP_HLEN)); #if IP_FRAG_USES_STATIC_BUF if (last) { pbuf_realloc(rambuf, left + IP_HLEN); } /* This part is ugly: we alloc a RAM based pbuf for * the link level header for each chunk and then * free it.A PBUF_ROM style pbuf for which pbuf_header * worked would make things simpler. */ header = pbuf_alloc(PBUF_LINK, 0, PBUF_RAM); if (header != NULL) { pbuf_chain(header, rambuf); netif->output(netif, header, dest); IPFRAG_STATS_INC(ip_frag.xmit); snmp_inc_ipfragcreates(); pbuf_free(header); } else { LWIP_DEBUGF(IP_REASS_DEBUG, ("ip_frag: pbuf_alloc() for header failed\n")); pbuf_free(rambuf); return ERR_MEM; } #else /* IP_FRAG_USES_STATIC_BUF */ /* No need for separate header pbuf - we allowed room for it in rambuf * when allocated. */ netif->output(netif, rambuf, dest); IPFRAG_STATS_INC(ip_frag.xmit); /* Unfortunately we can't reuse rambuf - the hardware may still be * using the buffer. Instead we free it (and the ensuing chain) and * recreate it next time round the loop. If we're lucky the hardware * will have already sent the packet, the free will really free, and * there will be zero memory penalty. */ pbuf_free(rambuf); #endif /* IP_FRAG_USES_STATIC_BUF */ left -= cop; ofo += nfb; } #if IP_FRAG_USES_STATIC_BUF pbuf_free(rambuf); #endif /* IP_FRAG_USES_STATIC_BUF */ snmp_inc_ipfragoks(); return ERR_OK; } #endif /* IP_FRAG */