BadVPN – Rev 1
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/**
* @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"
#if LWIP_IPV4
#include "lwip/ip4_frag.h"
#include "lwip/def.h"
#include "lwip/inet_chksum.h"
#include "lwip/netif.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
#define IP_REASS_VALIDATE_TELEGRAM_FINISHED 1
#define IP_REASS_VALIDATE_PBUF_QUEUED 0
#define IP_REASS_VALIDATE_PBUF_DROPPED -1
/** 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) \
(ip4_addr_cmp(&(iphdrA)->src, &(iphdrB)->src) && \
ip4_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;
u16_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);
}
MIB2_STATS_INC(mib2.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 = (u16_t)(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 = (u16_t)(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 >= pbufs_freed", ip_reass_pbufcount >= pbufs_freed);
ip_reass_pbufcount = (u16_t)(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, *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;
oldest_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;
oldest_prev = prev;
} else if (r->timer <= oldest->timer) {
/* older than the previous oldest */
oldest = r;
oldest_prev = prev;
}
}
if (r->next != NULL) {
prev = r;
}
r = r->next;
}
if (oldest != NULL) {
pbufs_freed_current = ip_reass_free_complete_datagram(oldest, 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;
#if ! IP_REASS_FREE_OLDEST
LWIP_UNUSED_ARG(clen);
#endif
/* 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_reassdata 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 ipr points to the reassembly state
* @param new_p points to the pbuf for the current fragment
* @param is_last is 1 if this pbuf has MF==0 (ipr->flags not updated yet)
* @return see IP_REASS_VALIDATE_* defines
*/
static int
ip_reass_chain_frag_into_datagram_and_validate(struct ip_reassdata *ipr, struct pbuf *new_p, int is_last)
{
struct ip_reass_helper *iprh, *iprh_tmp, *iprh_prev = NULL;
struct pbuf *q;
u16_t offset, len, clen;
u8_t hlen;
struct ip_hdr *fraghdr;
int valid = 1;
/* Extract length and fragment offset from current fragment */
fraghdr = (struct ip_hdr *)new_p->payload;
len = lwip_ntohs(IPH_LEN(fraghdr));
hlen = IPH_HL_BYTES(fraghdr);
if (hlen > len) {
/* invalid datagram */
goto freepbuf;
}
len = (u16_t)(len - hlen);
offset = IPH_OFFSET_BYTES(fraghdr);
/* 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 = (u16_t)(offset + len);
if (iprh->end < offset) {
/* u16_t overflow, cannot handle this */
goto freepbuf;
}
/* Iterate through until we either get to the end of the list (append),
* or we find one 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;
if (iprh_prev->end != iprh->start) {
/* There is a fragment missing between the current
* and the previous fragment */
valid = 0;
}
} else {
#if IP_REASS_CHECK_OVERLAP
if (iprh->end > iprh_tmp->start) {
/* fragment overlaps with following, throw away */
goto freepbuf;
}
#endif /* IP_REASS_CHECK_OVERLAP */
/* 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 holes. */
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 (is_last || ((ipr->flags & IP_REASS_FLAG_LASTFRAG) != 0)) {
/* and had no holes so far */
if (valid) {
/* then check if the rest of the fragments is here */
/* Check if the queue starts with the first datagram */
if ((ipr->p == NULL) || (((struct ip_reass_helper *)ipr->p->payload)->start != 0)) {
valid = 0;
} else {
/* and check that there are no holes 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);
}
}
}
/* 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 ? IP_REASS_VALIDATE_TELEGRAM_FINISHED : IP_REASS_VALIDATE_PBUF_QUEUED;
}
/* If we come here, not all fragments were received, yet! */
return IP_REASS_VALIDATE_PBUF_QUEUED; /* not yet valid! */
#if IP_REASS_CHECK_OVERLAP
freepbuf:
clen = pbuf_clen(new_p);
LWIP_ASSERT("ip_reass_pbufcount >= clen", ip_reass_pbufcount >= clen);
ip_reass_pbufcount = (u16_t)(ip_reass_pbufcount - clen);
pbuf_free(new_p);
return IP_REASS_VALIDATE_PBUF_DROPPED;
#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 *
ip4_reass(struct pbuf *p)
{
struct pbuf *r;
struct ip_hdr *fraghdr;
struct ip_reassdata *ipr;
struct ip_reass_helper *iprh;
u16_t offset, len, clen;
u8_t hlen;
int valid;
int is_last;
IPFRAG_STATS_INC(ip_frag.recv);
MIB2_STATS_INC(mib2.ipreasmreqds);
fraghdr = (struct ip_hdr *)p->payload;
if ((IPH_HL(fraghdr) * 4) != IP_HLEN) {
LWIP_DEBUGF(IP_REASS_DEBUG, ("ip4_reass: IP options currently not supported!\n"));
IPFRAG_STATS_INC(ip_frag.err);
goto nullreturn;
}
offset = IPH_OFFSET_BYTES(fraghdr);
len = lwip_ntohs(IPH_LEN(fraghdr));
hlen = IPH_HL_BYTES(fraghdr);
if (hlen > len) {
/* invalid datagram */
goto nullreturn;
}
len = (u16_t)(len - hlen);
/* 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, ("ip4_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, ("ip4_reass: matching previous fragment ID=%"X16_F"\n",
lwip_ntohs(IPH_ID(fraghdr))));
IPFRAG_STATS_INC(ip_frag.cachehit);
break;
}
}
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 (((lwip_ntohs(IPH_OFFSET(fraghdr)) & IP_OFFMASK) == 0) &&
((lwip_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);
}
}
/* 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*/
is_last = (IPH_OFFSET(fraghdr) & PP_NTOHS(IP_MF)) == 0;
if (is_last) {
u16_t datagram_len = (u16_t)(offset + len);
if ((datagram_len < offset) || (datagram_len > (0xFFFF - IP_HLEN))) {
/* u16_t overflow, cannot handle this */
goto nullreturn;
}
}
/* find the right place to insert this pbuf */
/* @todo: trim pbufs if fragments are overlapping */
valid = ip_reass_chain_frag_into_datagram_and_validate(ipr, p, is_last);
if (valid == IP_REASS_VALIDATE_PBUF_DROPPED) {
goto nullreturn;
}
/* if we come here, the pbuf has been enqueued */
/* 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
(overflow checked by testing against IP_REASS_MAX_PBUFS) */
ip_reass_pbufcount = (u16_t)(ip_reass_pbufcount + clen);
if (is_last) {
u16_t datagram_len = (u16_t)(offset + len);
ipr->datagram_len = datagram_len;
ipr->flags |= IP_REASS_FLAG_LASTFRAG;
LWIP_DEBUGF(IP_REASS_DEBUG,
("ip4_reass: last fragment seen, total len %"S16_F"\n",
ipr->datagram_len));
}
if (valid == IP_REASS_VALIDATE_TELEGRAM_FINISHED) {
struct ip_reassdata *ipr_prev;
/* the totally last fragment (flag more fragments = 0) was received at least
* once AND all fragments are received */
u16_t datagram_len = (u16_t)(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, lwip_htons(datagram_len));
IPH_OFFSET_SET(fraghdr, 0);
IPH_CHKSUM_SET(fraghdr, 0);
/* @todo: do we need to set/calculate the correct checksum? */
#if CHECKSUM_GEN_IP
IF__NETIF_CHECKSUM_ENABLED(ip_current_input_netif(), NETIF_CHECKSUM_GEN_IP) {
IPH_CHKSUM_SET(fraghdr, inet_chksum(fraghdr, IP_HLEN));
}
#endif /* CHECKSUM_GEN_IP */
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 succeeding fragment */
pbuf_remove_header(r, IP_HLEN);
pbuf_cat(p, r);
r = iprh->next_pbuf;
}
/* find the previous entry in the linked list */
if (ipr == reassdatagrams) {
ipr_prev = NULL;
} else {
for (ipr_prev = reassdatagrams; ipr_prev != NULL; ipr_prev = ipr_prev->next) {
if (ipr_prev->next == ipr) {
break;
}
}
}
/* 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. */
clen = pbuf_clen(p);
LWIP_ASSERT("ip_reass_pbufcount >= clen", ip_reass_pbufcount >= clen);
ip_reass_pbufcount = (u16_t)(ip_reass_pbufcount - clen);
MIB2_STATS_INC(mib2.ipreasmoks);
/* 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, ("ip4_reass: nullreturn\n"));
IPFRAG_STATS_INC(ip_frag.drop);
pbuf_free(p);
return NULL;
}
#endif /* IP_REASSEMBLY */
#if IP_FRAG
#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 */
/**
* Fragment an IP datagram if too large for the netif.
*
* Chop the datagram in MTU sized chunks and send them in order
* by pointing PBUF_REFs into p.
*
* @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
ip4_frag(struct pbuf *p, struct netif *netif, const ip4_addr_t *dest)
{
struct pbuf *rambuf;
#if !LWIP_NETIF_TX_SINGLE_PBUF
struct pbuf *newpbuf;
u16_t newpbuflen = 0;
u16_t left_to_copy;
#endif
struct ip_hdr *original_iphdr;
struct ip_hdr *iphdr;
const u16_t nfb = (u16_t)((netif->mtu - IP_HLEN) / 8);
u16_t left, fragsize;
u16_t ofo;
int last;
u16_t poff = IP_HLEN;
u16_t tmp;
original_iphdr = (struct ip_hdr *)p->payload;
iphdr = original_iphdr;
LWIP_ERROR("ip4_frag() does not support IP options", IPH_HL_BYTES(iphdr) == IP_HLEN, return ERR_VAL);
LWIP_ERROR("ip4_frag(): pbuf too short", p->len >= IP_HLEN, return ERR_VAL);
/* Save original offset */
tmp = lwip_ntohs(IPH_OFFSET(iphdr));
ofo = tmp & IP_OFFMASK;
LWIP_ERROR("ip_frag(): MF already set", (tmp & IP_MF) == 0, return ERR_VAL);
left = (u16_t)(p->tot_len - IP_HLEN);
while (left) {
/* Fill this fragment */
fragsize = LWIP_MIN(left, (u16_t)(nfb * 8));
#if LWIP_NETIF_TX_SINGLE_PBUF
rambuf = pbuf_alloc(PBUF_IP, fragsize, PBUF_RAM);
if (rambuf == NULL) {
goto memerr;
}
LWIP_ASSERT("this needs a pbuf in one piece!",
(rambuf->len == rambuf->tot_len) && (rambuf->next == NULL));
poff += pbuf_copy_partial(p, rambuf->payload, fragsize, poff);
/* make room for the IP header */
if (pbuf_add_header(rambuf, IP_HLEN)) {
pbuf_free(rambuf);
goto memerr;
}
/* fill in the IP header */
SMEMCPY(rambuf->payload, original_iphdr, IP_HLEN);
iphdr = (struct ip_hdr *)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) {
goto memerr;
}
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;
left_to_copy = fragsize;
while (left_to_copy) {
struct pbuf_custom_ref *pcr;
u16_t plen = (u16_t)(p->len - poff);
LWIP_ASSERT("p->len >= poff", p->len >= poff);
newpbuflen = LWIP_MIN(left_to_copy, plen);
/* Is this pbuf already empty? */
if (!newpbuflen) {
poff = 0;
p = p->next;
continue;
}
pcr = ip_frag_alloc_pbuf_custom_ref();
if (pcr == NULL) {
pbuf_free(rambuf);
goto memerr;
}
/* Mirror this pbuf, although we might not need all of it. */
newpbuf = pbuf_alloced_custom(PBUF_RAW, newpbuflen, PBUF_REF, &pcr->pc,
(u8_t *)p->payload + poff, newpbuflen);
if (newpbuf == NULL) {
ip_frag_free_pbuf_custom_ref(pcr);
pbuf_free(rambuf);
goto memerr;
}
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 = (u16_t)(left_to_copy - newpbuflen);
if (left_to_copy) {
poff = 0;
p = p->next;
}
}
poff = (u16_t)(poff + newpbuflen);
#endif /* LWIP_NETIF_TX_SINGLE_PBUF */
/* Correct header */
last = (left <= netif->mtu - IP_HLEN);
/* Set new offset and MF flag */
tmp = (IP_OFFMASK & (ofo));
if (!last) {
tmp = tmp | IP_MF;
}
IPH_OFFSET_SET(iphdr, lwip_htons(tmp));
IPH_LEN_SET(iphdr, lwip_htons((u16_t)(fragsize + IP_HLEN)));
IPH_CHKSUM_SET(iphdr, 0);
#if CHECKSUM_GEN_IP
IF__NETIF_CHECKSUM_ENABLED(netif, NETIF_CHECKSUM_GEN_IP) {
IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, IP_HLEN));
}
#endif /* CHECKSUM_GEN_IP */
/* 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);
left = (u16_t)(left - fragsize);
ofo = (u16_t)(ofo + nfb);
}
MIB2_STATS_INC(mib2.ipfragoks);
return ERR_OK;
memerr:
MIB2_STATS_INC(mib2.ipfragfails);
return ERR_MEM;
}
#endif /* IP_FRAG */
#endif /* LWIP_IPV4 */