struct ip_reassdata* ip_reass_lookup_dg( struct ip_hdr *fraghdr )
{
struct ip_reassdata *ipr;
sys_lock_acquire( &ip_frag_lock );
for (ipr = reassdatagrams; ipr != NULL; ipr = ipr->next) {
if (IP_ADDRESSES_AND_ID_MATCH(&ipr->iphdr, fraghdr)) {
break;
}
}
sys_lock_release( &ip_frag_lock );
return ipr;
}
/**
* 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;
}
/**
* 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;
}
