--- /dev/null
+/**
+ * @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/ip.h"
+#include "lwip/inet.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.
+ */
+struct ip_reass_helper {
+ struct pbuf *next_pbuf;
+ u16_t start;
+ u16_t end;
+};
+
+#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)
+{
+ int pbufs_freed = 0;
+ 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);
+ pbufs_freed += pbuf_clen(p);
+ 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;
+ pbufs_freed += pbuf_clen(pcur);
+ 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 = memp_malloc(MEMP_REASSDATA);
+ if (ipr == NULL) {
+#if IP_REASS_FREE_OLDEST
+ if (ip_reass_remove_oldest_datagram(fraghdr, clen) >= clen) {
+ ipr = 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 ((ntohs(IPH_OFFSET(fraghdr)) & 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)];
+#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, struct ip_addr *dest)
+{
+ struct pbuf *rambuf;
+#if IP_FRAG_USES_STATIC_BUF
+ struct pbuf *header;
+#else
+ struct pbuf *newpbuf;
+ 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
+ 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 = rambuf->payload;
+ SMEMCPY(iphdr, p->payload, IP_HLEN);
+#else /* IP_FRAG_USES_STATIC_BUF */
+ original_iphdr = 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 */
+ /* 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 = 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) {
+ newpbuflen = (left_to_copy < p->len) ? left_to_copy : p->len;
+ /* Is this pbuf already empty? */
+ if (!newpbuflen) {
+ p = p->next;
+ continue;
+ }
+ newpbuf = pbuf_alloc(PBUF_RAW, 0, PBUF_REF);
+ if (newpbuf == NULL) {
+ pbuf_free(rambuf);
+ return ERR_MEM;
+ }
+ /* Mirror this pbuf, although we might not need all of it. */
+ newpbuf->payload = p->payload;
+ newpbuf->len = newpbuf->tot_len = newpbuflen;
+ /* 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 /* 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 */
