/**
* Reassembles incoming IPv6 fragments into an IPv6 datagram.
*
* @param p points to the IPv6 Fragment Header
* @param len the length of the payload (after Fragment Header)
* @return NULL if reassembly is incomplete, pbuf pointing to
* IPv6 Header if reassembly is complete
*/
struct pbuf *
ip6_reass(struct pbuf *p)
{
struct ip6_reassdata *ipr, **pipr;
struct ip6_reass_helper *iprh, *iprh_tmp;
struct ip6_reass_helper **pnext;
struct ip6_frag_hdr * frag_hdr;
size_t unfrag_len;
u16_t offset, len, start, end, validlen;
u8_t clen;
IP6_FRAG_STATS_INC(ip6_frag.recv);
frag_hdr = (struct ip6_frag_hdr *) p->payload;
clen = pbuf_clen(p);
offset = ntohs(frag_hdr->_fragment_offset);
/* Calculate fragment length from IPv6 payload length.
* Adjust for headers before Fragment Header.
* And finally adjust by Fragment Header length. */
len = ntohs(ip6_current_header()->_plen);
len -= ((u8_t*)p->payload - (u8_t*)ip6_current_header()) - IP6_HLEN;
len -= IP6_FRAG_HLEN;
start = (offset & IP6_FRAG_OFFSET_MASK);
end = start + len;
/* 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 ((frag_hdr->_identification == ipr->identification) &&
ip6_addr_cmp(ip6_current_src_addr(), &(ipr->iphdr.src)) &&
ip6_addr_cmp(ip6_current_dest_addr(), &(ipr->iphdr.dest))) {
IP6_FRAG_STATS_INC(ip6_frag.cachehit);
break;
}
}
if (ipr == NULL) {
/* Enqueue a new datagram into the datagram queue */
ipr = (struct ip6_reassdata *)memp_malloc(MEMP_IP6_REASSDATA);
if (ipr == NULL) {
#if IP_REASS_FREE_OLDEST
/* Make room and try again. */
ip6_reass_remove_oldest_datagram(ipr, clen);
ipr = (struct ip6_reassdata *)memp_malloc(MEMP_IP6_REASSDATA);
if (ipr == NULL)
#endif /* IP_REASS_FREE_OLDEST */
{
IP6_FRAG_STATS_INC(ip6_frag.memerr);
IP6_FRAG_STATS_INC(ip6_frag.drop);
goto nullreturn;
}
}
memset(ipr, 0, sizeof(struct ip6_reassdata));
ipr->timer = IP_REASS_MAXAGE;
/* enqueue the new structure to the front of the list */
ipr->next = reassdatagrams;
reassdatagrams = ipr;
/* Use the current IPv6 header for src/dest address reference.
* Eventually, we will replace it when we get the first fragment
* (it might be this one, in any case, it is done later). */
SMEMCPY(&ipr->iphdr, ip6_current_header(), IP6_HLEN);
if (start == 0) {
ipr->iphdr0 = (struct ip6_hdr *)ip6_current_header();
}
/* copy the fragmented packet id. */
ipr->identification = frag_hdr->_identification;
}
/* If this is the last fragment, save total packet length. */
if ((offset & IP6_FRAG_MORE_FLAG) == 0) {
#if IP_REASS_CHECK_OVERLAP
if (ipr->datagram_len != 0) {
IP6_FRAG_STATS_INC(ip6_frag.proterr);
IP6_FRAG_STATS_INC(ip6_frag.drop);
goto nullreturn;
}
#endif /* IP_REASS_CHECK_OVERLAP */
ipr->datagram_len = end;
}
/* find the place to insert this pbuf */
validlen = 0;
for (pnext = &ipr->iprh; *pnext != NULL; pnext = &(*pnext)->next) {
iprh_tmp = *pnext;
if (start < iprh_tmp->start) {
/* the new pbuf should be inserted before this */
#if IP_REASS_CHECK_OVERLAP
if (end > iprh_tmp->start) {
/* fragment overlaps with following, throw away */
IP6_FRAG_STATS_INC(ip6_frag.proterr);
IP6_FRAG_STATS_INC(ip6_frag.drop);
goto nullreturn;
}
#endif /* IP_REASS_CHECK_OVERLAP */
break;
}
else if (start == iprh_tmp->start) {
/* received the same datagram twice: no need to keep the datagram */
IP6_FRAG_STATS_INC(ip6_frag.drop);
goto nullreturn;
}
#if IP_REASS_CHECK_OVERLAP
else if (start < iprh_tmp->end) {
/* overlap: no need to keep the new datagram */
IP6_FRAG_STATS_INC(ip6_frag.proterr);
IP6_FRAG_STATS_INC(ip6_frag.drop);
goto nullreturn;
}
#endif /* IP_REASS_CHECK_OVERLAP */
else {
/* Check if the fragments received so far have no gaps. */
if (validlen == iprh_tmp->start) {
validlen = iprh_tmp->end;
}
else {
validlen = 0;
}
}
}
/* Check if we are allowed to enqueue more datagrams. */
if ((ip6_reass_pbufcount + clen) > IP_REASS_MAX_PBUFS) {
#if IP_REASS_FREE_OLDEST
ip6_reass_remove_oldest_datagram(ipr, clen);
if ((ip6_reass_pbufcount + clen) > IP_REASS_MAX_PBUFS)
#endif /* IP_REASS_FREE_OLDEST */
{
/* @todo: send ICMPv6 time exceeded here? */
/* drop this pbuf */
IP6_FRAG_STATS_INC(ip6_frag.memerr);
IP6_FRAG_STATS_INC(ip6_frag.drop);
goto nullreturn;
}
}
if (start == 0 && ipr->iphdr0 == NULL) {
/*
* We've got the fragment with offset 0 out of order, remember its
* IPv6 header location (in the hidden part of the current pbuf)
* and update the copy in ip6_reassdata::iphdr. We don't need to
* copy complete header since src and dest are the same as in the
* first fragment we received.
*/
ipr->iphdr0 = (struct ip6_hdr *)ip6_current_header();
SMEMCPY(&ipr->iphdr, ip6_current_header(),
IP6_HLEN - 2 * sizeof(ip_addr_p_t));
}
/* Overwrite IPv6 Header with our own helper struct (aligned). */
iprh = (struct ip6_reass_helper *)
(((uintptr_t)(u8_t *)ip6_current_header() + sizeof(void *) - 1)
& ~(sizeof(void *) - 1));
iprh->p = p;
iprh->start = start;
iprh->end = end;
/* insert it into the list */
iprh->next = *pnext;
*pnext = iprh;
/* 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 */
ip6_reass_pbufcount += clen;
if (ipr->datagram_len == 0) {
/* We still don't have the last fragment. */
return NULL;
}
if (validlen == start) {
validlen = end;
}
else {
/* There are gaps before this fragment. */
return NULL;
}
if (validlen != 0) {
/*
* We know we have all the data up to the end of this fragment and
* we know the total length. Check if the reassembly is complete.
*/
for (iprh_tmp = iprh->next; iprh_tmp != NULL; iprh_tmp = iprh_tmp->next) {
if (validlen == iprh_tmp->start) {
validlen = iprh_tmp->end;
}
else {
validlen = 0;
break;
}
}
if (validlen != ipr->datagram_len) {
/* the datagram is not yet reassembled completely */
return NULL;
}
}
/*
* All fragments have been received. Reassemble original datagram
* and return it to ip6_input() to be processed instead of the final
* fragment that completed the reassembly.
*/
/* chain together the pbufs contained within the ip6_reassdata list. */
p = NULL;
for (iprh = ipr->iprh; iprh != NULL; iprh = iprh->next) {
if (p == NULL) {
p = iprh->p;
}
else {
/* hide the fragment header for every succeeding fragment */
pbuf_header(iprh->p, -IP6_FRAG_HLEN);
pbuf_cat(p, iprh->p);
}
}
/* Adjust datagram length by adding preceding header lengths. */
unfrag_len = (u8_t *)p->payload - (u8_t *)ipr->iphdr0;
# ifndef VBOX
ipr->datagram_len += unfrag_len - IP6_HLEN + IP6_FRAG_HLEN;
# else
LWIP_ASSERT("overflow", (s16_t)unfrag_len == (ssize_t)unfrag_len); /* s16_t because of pbuf_header call */
ipr->datagram_len += (u16_t)(unfrag_len - IP6_HLEN + IP6_FRAG_HLEN);
# endif
/* Set payload length in ip header. */
ipr->iphdr._plen = htons(ipr->datagram_len);
/* restore IPv6 header (overwritten with ip6_reass_helper) */
SMEMCPY(ipr->iphdr0, &ipr->iphdr, IP6_HLEN);
/* Mark as "single fragment" packet (see caller). */
frag_hdr = (struct ip6_frag_hdr *) p->payload;
frag_hdr->_fragment_offset = 0;
/* Unlink from the reassdatagrams list */
for (pipr = &reassdatagrams; *pipr != NULL; pipr = &(*pipr)->next) {
if (*pipr == ipr) {
(*pipr) = ipr->next;
break;
}
}
memp_free(MEMP_IP6_REASSDATA, ipr);
/* adjust the number of pbufs currently queued for reassembly. */
ip6_reass_pbufcount -= pbuf_clen(p);
/* Move pbuf back to IPv6 header. */
# ifndef VBOX
if (pbuf_header(p, unfrag_len) != 0) {
# else
if (pbuf_header(p, (s16_t)unfrag_len) != 0) {
# endif
LWIP_ASSERT("ip6_reass: moving p->payload to ip6 header failed\n", 0);
goto nullreturn;
}
/* Return the pbuf chain */
return p;
nullreturn:
pbuf_free(p);
return NULL;
}
#endif /* LWIP_IPV6 && LWIP_IPV6_REASS */
#if LWIP_IPV6 && LWIP_IPV6_FRAG
/** Allocate a new struct pbuf_custom_ref */
static struct pbuf_custom_ref*
ip6_frag_alloc_pbuf_custom_ref(void)
{
return (struct pbuf_custom_ref*)memp_malloc(MEMP_FRAG_PBUF);
}
/** Free a struct pbuf_custom_ref */
static void
ip6_frag_free_pbuf_custom_ref(struct pbuf_custom_ref* p)
{
LWIP_ASSERT("p != NULL", p != NULL);
memp_free(MEMP_FRAG_PBUF, p);
}
/**
* Reassembles incoming IPv6 fragments into an IPv6 datagram.
*
* @param p points to the IPv6 Fragment Header
* @return NULL if reassembly is incomplete, pbuf pointing to
* IPv6 Header if reassembly is complete
*/
struct pbuf *
ip6_reass(struct pbuf *p)
{
struct ip6_reassdata *ipr, *ipr_prev;
struct ip6_reass_helper *iprh, *iprh_tmp, *iprh_prev=NULL;
struct ip6_frag_hdr *frag_hdr;
u16_t offset, len;
u16_t clen;
u8_t valid = 1;
struct pbuf *q;
IP6_FRAG_STATS_INC(ip6_frag.recv);
if ((const void*)ip6_current_header() != ((u8_t*)p->payload) - IP6_HLEN) {
/* ip6_frag_hdr must be in the first pbuf, not chained */
IP6_FRAG_STATS_INC(ip6_frag.proterr);
IP6_FRAG_STATS_INC(ip6_frag.drop);
goto nullreturn;
}
frag_hdr = (struct ip6_frag_hdr *) p->payload;
clen = pbuf_clen(p);
offset = lwip_ntohs(frag_hdr->_fragment_offset);
/* Calculate fragment length from IPv6 payload length.
* Adjust for headers before Fragment Header.
* And finally adjust by Fragment Header length. */
len = lwip_ntohs(ip6_current_header()->_plen);
len -= (u16_t)(((u8_t*)p->payload - (const u8_t*)ip6_current_header()) - IP6_HLEN);
len -= IP6_FRAG_HLEN;
/* 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_prev = NULL; 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 ((frag_hdr->_identification == ipr->identification) &&
ip6_addr_cmp(ip6_current_src_addr(), &(IPV6_FRAG_HDRREF(ipr->iphdr)->src)) &&
ip6_addr_cmp(ip6_current_dest_addr(), &(IPV6_FRAG_HDRREF(ipr->iphdr)->dest))) {
IP6_FRAG_STATS_INC(ip6_frag.cachehit);
break;
}
ipr_prev = ipr;
}
if (ipr == NULL) {
/* Enqueue a new datagram into the datagram queue */
ipr = (struct ip6_reassdata *)memp_malloc(MEMP_IP6_REASSDATA);
if (ipr == NULL) {
#if IP_REASS_FREE_OLDEST
/* Make room and try again. */
ip6_reass_remove_oldest_datagram(ipr, clen);
ipr = (struct ip6_reassdata *)memp_malloc(MEMP_IP6_REASSDATA);
if (ipr != NULL) {
/* re-search ipr_prev since it might have been removed */
for (ipr_prev = reassdatagrams; ipr_prev != NULL; ipr_prev = ipr_prev->next) {
if (ipr_prev->next == ipr) {
break;
}
}
} else
#endif /* IP_REASS_FREE_OLDEST */
{
IP6_FRAG_STATS_INC(ip6_frag.memerr);
IP6_FRAG_STATS_INC(ip6_frag.drop);
goto nullreturn;
}
}
memset(ipr, 0, sizeof(struct ip6_reassdata));
ipr->timer = IP_REASS_MAXAGE;
/* enqueue the new structure to the front of the list */
ipr->next = reassdatagrams;
reassdatagrams = ipr;
/* Use the current IPv6 header for src/dest address reference.
* Eventually, we will replace it when we get the first fragment
* (it might be this one, in any case, it is done later). */
#if IPV6_FRAG_COPYHEADER
MEMCPY(&ipr->iphdr, ip6_current_header(), IP6_HLEN);
#else /* IPV6_FRAG_COPYHEADER */
/* need to use the none-const pointer here: */
ipr->iphdr = ip_data.current_ip6_header;
#endif /* IPV6_FRAG_COPYHEADER */
/* copy the fragmented packet id. */
ipr->identification = frag_hdr->_identification;
/* copy the nexth field */
ipr->nexth = frag_hdr->_nexth;
}
/* Check if we are allowed to enqueue more datagrams. */
if ((ip6_reass_pbufcount + clen) > IP_REASS_MAX_PBUFS) {
#if IP_REASS_FREE_OLDEST
ip6_reass_remove_oldest_datagram(ipr, clen);
if ((ip6_reass_pbufcount + clen) <= IP_REASS_MAX_PBUFS) {
/* re-search ipr_prev since it might have been removed */
for (ipr_prev = reassdatagrams; ipr_prev != NULL; ipr_prev = ipr_prev->next) {
if (ipr_prev->next == ipr) {
break;
}
}
} else
#endif /* IP_REASS_FREE_OLDEST */
{
/* @todo: send ICMPv6 time exceeded here? */
/* drop this pbuf */
IP6_FRAG_STATS_INC(ip6_frag.memerr);
IP6_FRAG_STATS_INC(ip6_frag.drop);
goto nullreturn;
}
}
/* Overwrite Fragment Header with our own helper struct. */
#if IPV6_FRAG_COPYHEADER
if (IPV6_FRAG_REQROOM > 0) {
/* Make room for struct ip6_reass_helper (only required if sizeof(void*) > 4).
This cannot fail since we already checked when receiving this fragment. */
u8_t hdrerr = pbuf_header_force(p, IPV6_FRAG_REQROOM);
LWIP_UNUSED_ARG(hdrerr); /* in case of LWIP_NOASSERT */
LWIP_ASSERT("no room for struct ip6_reass_helper", hdrerr == 0);
}
#else /* IPV6_FRAG_COPYHEADER */
LWIP_ASSERT("sizeof(struct ip6_reass_helper) <= IP6_FRAG_HLEN, set IPV6_FRAG_COPYHEADER to 1",
sizeof(struct ip6_reass_helper) <= IP6_FRAG_HLEN);
#endif /* IPV6_FRAG_COPYHEADER */
iprh = (struct ip6_reass_helper *)p->payload;
iprh->next_pbuf = NULL;
iprh->start = (offset & IP6_FRAG_OFFSET_MASK);
iprh->end = (offset & IP6_FRAG_OFFSET_MASK) + len;
/* find the right place to insert this pbuf */
/* 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 ip6_reass_helper*)q->payload;
if (iprh->start < iprh_tmp->start) {
#if IP_REASS_CHECK_OVERLAP
if (iprh->end > iprh_tmp->start) {
/* fragment overlaps with following, throw away */
IP6_FRAG_STATS_INC(ip6_frag.proterr);
IP6_FRAG_STATS_INC(ip6_frag.drop);
goto nullreturn;
}
if (iprh_prev != NULL) {
if (iprh->start < iprh_prev->end) {
/* fragment overlaps with previous, throw away */
IP6_FRAG_STATS_INC(ip6_frag.proterr);
IP6_FRAG_STATS_INC(ip6_frag.drop);
goto nullreturn;
}
}
#endif /* IP_REASS_CHECK_OVERLAP */
/* the new pbuf should be inserted before this */
iprh->next_pbuf = q;
if (iprh_prev != NULL) {
/* not the fragment with the lowest offset */
iprh_prev->next_pbuf = p;
} else {
/* fragment with the lowest offset */
ipr->p = p;
}
break;
} else if (iprh->start == iprh_tmp->start) {
/* received the same datagram twice: no need to keep the datagram */
IP6_FRAG_STATS_INC(ip6_frag.drop);
goto nullreturn;
#if IP_REASS_CHECK_OVERLAP
} else if (iprh->start < iprh_tmp->end) {
/* overlap: no need to keep the new datagram */
IP6_FRAG_STATS_INC(ip6_frag.proterr);
IP6_FRAG_STATS_INC(ip6_frag.drop);
goto nullreturn;
#endif /* IP_REASS_CHECK_OVERLAP */
} else {
/* Check if the fragments received so far have no gaps. */
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 = 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 = p;
}
}
/* 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 */
ip6_reass_pbufcount += clen;
/* Remember IPv6 header if this is the first fragment. */
if (iprh->start == 0) {
#if IPV6_FRAG_COPYHEADER
if (iprh->next_pbuf != NULL) {
MEMCPY(&ipr->iphdr, ip6_current_header(), IP6_HLEN);
}
#else /* IPV6_FRAG_COPYHEADER */
/* need to use the none-const pointer here: */
ipr->iphdr = ip_data.current_ip6_header;
#endif /* IPV6_FRAG_COPYHEADER */
}
/* If this is the last fragment, calculate total packet length. */
if ((offset & IP6_FRAG_MORE_FLAG) == 0) {
ipr->datagram_len = iprh->end;
}
/* Additional validity tests: we have received first and last fragment. */
iprh_tmp = (struct ip6_reass_helper*)ipr->p->payload;
if (iprh_tmp->start != 0) {
valid = 0;
}
if (ipr->datagram_len == 0) {
valid = 0;
}
/* Final validity test: no gaps between current and last fragment. */
iprh_prev = iprh;
q = iprh->next_pbuf;
while ((q != NULL) && valid) {
iprh = (struct ip6_reass_helper*)q->payload;
if (iprh_prev->end != iprh->start) {
valid = 0;
break;
}
iprh_prev = iprh;
q = iprh->next_pbuf;
}
if (valid) {
/* All fragments have been received */
struct ip6_hdr* iphdr_ptr;
/* chain together the pbufs contained within the ip6_reassdata list. */
iprh = (struct ip6_reass_helper*) ipr->p->payload;
while (iprh != NULL) {
struct pbuf* next_pbuf = iprh->next_pbuf;
if (next_pbuf != NULL) {
/* Save next helper struct (will be hidden in next step). */
iprh_tmp = (struct ip6_reass_helper*)next_pbuf->payload;
/* hide the fragment header for every succeeding fragment */
pbuf_header(next_pbuf, -IP6_FRAG_HLEN);
#if IPV6_FRAG_COPYHEADER
if (IPV6_FRAG_REQROOM > 0) {
/* hide the extra bytes borrowed from ip6_hdr for struct ip6_reass_helper */
u8_t hdrerr = pbuf_header(next_pbuf, -(s16_t)(IPV6_FRAG_REQROOM));
LWIP_UNUSED_ARG(hdrerr); /* in case of LWIP_NOASSERT */
LWIP_ASSERT("no room for struct ip6_reass_helper", hdrerr == 0);
}
#endif
pbuf_cat(ipr->p, next_pbuf);
}
else {
iprh_tmp = NULL;
}
iprh = iprh_tmp;
}
#if IPV6_FRAG_COPYHEADER
if (IPV6_FRAG_REQROOM > 0) {
/* get back room for struct ip6_reass_helper (only required if sizeof(void*) > 4) */
u8_t hdrerr = pbuf_header(ipr->p, -(s16_t)(IPV6_FRAG_REQROOM));
LWIP_UNUSED_ARG(hdrerr); /* in case of LWIP_NOASSERT */
LWIP_ASSERT("no room for struct ip6_reass_helper", hdrerr == 0);
}
iphdr_ptr = (struct ip6_hdr*)((u8_t*)ipr->p->payload - IP6_HLEN);
MEMCPY(iphdr_ptr, &ipr->iphdr, IP6_HLEN);
#else
iphdr_ptr = ipr->iphdr;
#endif
/* Adjust datagram length by adding header lengths. */
ipr->datagram_len += (u16_t)(((u8_t*)ipr->p->payload - (u8_t*)iphdr_ptr)
+ IP6_FRAG_HLEN
- IP6_HLEN);
/* Set payload length in ip header. */
iphdr_ptr->_plen = lwip_htons(ipr->datagram_len);
/* Get the first pbuf. */
p = ipr->p;
/* Restore Fragment Header in first pbuf. Mark as "single fragment"
* packet. Restore nexth. */
frag_hdr = (struct ip6_frag_hdr *) p->payload;
frag_hdr->_nexth = ipr->nexth;
frag_hdr->reserved = 0;
frag_hdr->_fragment_offset = 0;
frag_hdr->_identification = 0;
/* release the sources allocate for the fragment queue entry */
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", ipr_prev != NULL);
ipr_prev->next = ipr->next;
}
memp_free(MEMP_IP6_REASSDATA, ipr);
/* adjust the number of pbufs currently queued for reassembly. */
ip6_reass_pbufcount -= pbuf_clen(p);
/* Move pbuf back to IPv6 header.
This cannot fail since we already checked when receiving this fragment. */
if (pbuf_header_force(p, (s16_t)((u8_t*)p->payload - (u8_t*)iphdr_ptr))) {
LWIP_ASSERT("ip6_reass: moving p->payload to ip6 header failed\n", 0);
pbuf_free(p);
return NULL;
}
/* Return the pbuf chain */
return p;
}
/* the datagram is not (yet?) reassembled completely */
return NULL;
nullreturn:
pbuf_free(p);
return NULL;
}
/**
* Reassembles incoming IPv6 fragments into an IPv6 datagram.
*
* @param p points to the IPv6 Fragment Header
* @return NULL if reassembly is incomplete, pbuf pointing to
* IPv6 Header if reassembly is complete
*/
struct pbuf *
ip6_reass(struct pbuf *p)
{
struct ip6_reassdata *ipr, *ipr_prev;
struct ip6_reass_helper *iprh, *iprh_tmp, *iprh_prev=NULL;
struct ip6_frag_hdr *frag_hdr;
u16_t offset, len, start, end;
ptrdiff_t hdrdiff;
u16_t clen;
u8_t valid = 1;
struct pbuf *q, *next_pbuf;
IP6_FRAG_STATS_INC(ip6_frag.recv);
/* ip6_frag_hdr must be in the first pbuf, not chained. Checked by caller. */
LWIP_ASSERT("IPv6 fragment header does not fit in first pbuf",
p->len >= sizeof(struct ip6_frag_hdr));
frag_hdr = (struct ip6_frag_hdr *) p->payload;
clen = pbuf_clen(p);
offset = lwip_ntohs(frag_hdr->_fragment_offset);
/* Calculate fragment length from IPv6 payload length.
* Adjust for headers before Fragment Header.
* And finally adjust by Fragment Header length. */
len = lwip_ntohs(ip6_current_header()->_plen);
hdrdiff = (u8_t*)p->payload - (const u8_t*)ip6_current_header();
LWIP_ASSERT("not a valid pbuf (ip6_input check missing?)", hdrdiff <= 0xFFFF);
LWIP_ASSERT("not a valid pbuf (ip6_input check missing?)", hdrdiff >= IP6_HLEN);
hdrdiff -= IP6_HLEN;
hdrdiff += IP6_FRAG_HLEN;
if (hdrdiff > len) {
IP6_FRAG_STATS_INC(ip6_frag.proterr);
goto nullreturn;
}
len = (u16_t)(len - hdrdiff);
start = (offset & IP6_FRAG_OFFSET_MASK);
if (start > (0xFFFF - len)) {
/* u16_t overflow, cannot handle this */
IP6_FRAG_STATS_INC(ip6_frag.proterr);
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_prev = NULL; 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 ((frag_hdr->_identification == ipr->identification) &&
ip6_addr_cmp_packed(ip6_current_src_addr(), &(IPV6_FRAG_SRC(ipr)), ipr->src_zone) &&
ip6_addr_cmp_packed(ip6_current_dest_addr(), &(IPV6_FRAG_DEST(ipr)), ipr->dest_zone)) {
IP6_FRAG_STATS_INC(ip6_frag.cachehit);
break;
}
ipr_prev = ipr;
}
if (ipr == NULL) {
/* Enqueue a new datagram into the datagram queue */
ipr = (struct ip6_reassdata *)memp_malloc(MEMP_IP6_REASSDATA);
if (ipr == NULL) {
#if IP_REASS_FREE_OLDEST
/* Make room and try again. */
ip6_reass_remove_oldest_datagram(ipr, clen);
ipr = (struct ip6_reassdata *)memp_malloc(MEMP_IP6_REASSDATA);
if (ipr != NULL) {
/* re-search ipr_prev since it might have been removed */
for (ipr_prev = reassdatagrams; ipr_prev != NULL; ipr_prev = ipr_prev->next) {
if (ipr_prev->next == ipr) {
break;
}
}
} else
#endif /* IP_REASS_FREE_OLDEST */
{
IP6_FRAG_STATS_INC(ip6_frag.memerr);
goto nullreturn;
}
}
memset(ipr, 0, sizeof(struct ip6_reassdata));
ipr->timer = IPV6_REASS_MAXAGE;
/* enqueue the new structure to the front of the list */
ipr->next = reassdatagrams;
reassdatagrams = ipr;
/* Use the current IPv6 header for src/dest address reference.
* Eventually, we will replace it when we get the first fragment
* (it might be this one, in any case, it is done later). */
/* need to use the none-const pointer here: */
ipr->iphdr = ip_data.current_ip6_header;
#if IPV6_FRAG_COPYHEADER
MEMCPY(&ipr->src, &ip6_current_header()->src, sizeof(ipr->src));
MEMCPY(&ipr->dest, &ip6_current_header()->dest, sizeof(ipr->dest));
#endif /* IPV6_FRAG_COPYHEADER */
#if LWIP_IPV6_SCOPES
/* Also store the address zone information.
* @todo It is possible that due to netif destruction and recreation, the
* stored zones end up resolving to a different interface. In that case, we
* risk sending a "time exceeded" ICMP response over the wrong link.
* Ideally, netif destruction would clean up matching pending reassembly
* structures, but custom zone mappings would make that non-trivial. */
ipr->src_zone = ip6_addr_zone(ip6_current_src_addr());
ipr->dest_zone = ip6_addr_zone(ip6_current_dest_addr());
#endif /* LWIP_IPV6_SCOPES */
/* copy the fragmented packet id. */
ipr->identification = frag_hdr->_identification;
/* copy the nexth field */
ipr->nexth = frag_hdr->_nexth;
}
/* Check if we are allowed to enqueue more datagrams. */
if ((ip6_reass_pbufcount + clen) > IP_REASS_MAX_PBUFS) {
#if IP_REASS_FREE_OLDEST
ip6_reass_remove_oldest_datagram(ipr, clen);
if ((ip6_reass_pbufcount + clen) <= IP_REASS_MAX_PBUFS) {
/* re-search ipr_prev since it might have been removed */
for (ipr_prev = reassdatagrams; ipr_prev != NULL; ipr_prev = ipr_prev->next) {
if (ipr_prev->next == ipr) {
break;
}
}
} else
#endif /* IP_REASS_FREE_OLDEST */
{
/* @todo: send ICMPv6 time exceeded here? */
/* drop this pbuf */
IP6_FRAG_STATS_INC(ip6_frag.memerr);
goto nullreturn;
}
}
/* Overwrite Fragment Header with our own helper struct. */
#if IPV6_FRAG_COPYHEADER
if (IPV6_FRAG_REQROOM > 0) {
/* Make room for struct ip6_reass_helper (only required if sizeof(void*) > 4).
This cannot fail since we already checked when receiving this fragment. */
u8_t hdrerr = pbuf_header_force(p, IPV6_FRAG_REQROOM);
LWIP_UNUSED_ARG(hdrerr); /* in case of LWIP_NOASSERT */
LWIP_ASSERT("no room for struct ip6_reass_helper", hdrerr == 0);
}
#else /* IPV6_FRAG_COPYHEADER */
LWIP_ASSERT("sizeof(struct ip6_reass_helper) <= IP6_FRAG_HLEN, set IPV6_FRAG_COPYHEADER to 1",
sizeof(struct ip6_reass_helper) <= IP6_FRAG_HLEN);
#endif /* IPV6_FRAG_COPYHEADER */
/* Prepare the pointer to the helper structure, and its initial values.
* Do not yet write to the structure itself, as we still have to make a
* backup of the original data, and we should not do that until we know for
* sure that we are going to add this packet to the list. */
iprh = (struct ip6_reass_helper *)p->payload;
next_pbuf = NULL;
end = (u16_t)(start + len);
/* find the right place to insert this pbuf */
/* 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 ip6_reass_helper*)q->payload;
if (start < iprh_tmp->start) {
#if IP_REASS_CHECK_OVERLAP
if (end > iprh_tmp->start) {
/* fragment overlaps with following, throw away */
IP6_FRAG_STATS_INC(ip6_frag.proterr);
goto nullreturn;
}
if (iprh_prev != NULL) {
if (start < iprh_prev->end) {
/* fragment overlaps with previous, throw away */
IP6_FRAG_STATS_INC(ip6_frag.proterr);
goto nullreturn;
}
}
#endif /* IP_REASS_CHECK_OVERLAP */
/* the new pbuf should be inserted before this */
next_pbuf = q;
if (iprh_prev != NULL) {
/* not the fragment with the lowest offset */
iprh_prev->next_pbuf = p;
} else {
/* fragment with the lowest offset */
ipr->p = p;
}
break;
} else if (start == iprh_tmp->start) {
/* received the same datagram twice: no need to keep the datagram */
goto nullreturn;
#if IP_REASS_CHECK_OVERLAP
} else if (start < iprh_tmp->end) {
/* overlap: no need to keep the new datagram */
IP6_FRAG_STATS_INC(ip6_frag.proterr);
goto nullreturn;
#endif /* IP_REASS_CHECK_OVERLAP */
} else {
/* Check if the fragments received so far have no gaps. */
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 <= start);
#endif /* IP_REASS_CHECK_OVERLAP */
iprh_prev->next_pbuf = p;
if (iprh_prev->end != 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 = p;
}
}
/* 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 */
ip6_reass_pbufcount = (u16_t)(ip6_reass_pbufcount + clen);
/* Remember IPv6 header if this is the first fragment. */
if (start == 0) {
/* need to use the none-const pointer here: */
ipr->iphdr = ip_data.current_ip6_header;
/* Make a backup of the part of the packet data that we are about to
* overwrite, so that we can restore the original later. */
MEMCPY(ipr->orig_hdr, p->payload, sizeof(*iprh));
/* For IPV6_FRAG_COPYHEADER there is no need to copy src/dst again, as they
* will be the same as they were. With LWIP_IPV6_SCOPES, the same applies
* to the source/destination zones. */
}
/* Only after the backup do we get to fill in the actual helper structure. */
iprh->next_pbuf = next_pbuf;
iprh->start = start;
iprh->end = end;
/* If this is the last fragment, calculate total packet length. */
if ((offset & IP6_FRAG_MORE_FLAG) == 0) {
ipr->datagram_len = iprh->end;
}
/* Additional validity tests: we have received first and last fragment. */
iprh_tmp = (struct ip6_reass_helper*)ipr->p->payload;
if (iprh_tmp->start != 0) {
valid = 0;
}
if (ipr->datagram_len == 0) {
valid = 0;
}
/* Final validity test: no gaps between current and last fragment. */
iprh_prev = iprh;
q = iprh->next_pbuf;
while ((q != NULL) && valid) {
iprh = (struct ip6_reass_helper*)q->payload;
if (iprh_prev->end != iprh->start) {
valid = 0;
break;
}
iprh_prev = iprh;
q = iprh->next_pbuf;
}
if (valid) {
/* All fragments have been received */
struct ip6_hdr* iphdr_ptr;
/* chain together the pbufs contained within the ip6_reassdata list. */
iprh = (struct ip6_reass_helper*) ipr->p->payload;
while (iprh != NULL) {
next_pbuf = iprh->next_pbuf;
if (next_pbuf != NULL) {
/* Save next helper struct (will be hidden in next step). */
iprh_tmp = (struct ip6_reass_helper*)next_pbuf->payload;
/* hide the fragment header for every succeeding fragment */
pbuf_remove_header(next_pbuf, IP6_FRAG_HLEN);
#if IPV6_FRAG_COPYHEADER
if (IPV6_FRAG_REQROOM > 0) {
/* hide the extra bytes borrowed from ip6_hdr for struct ip6_reass_helper */
u8_t hdrerr = pbuf_remove_header(next_pbuf, IPV6_FRAG_REQROOM);
LWIP_UNUSED_ARG(hdrerr); /* in case of LWIP_NOASSERT */
LWIP_ASSERT("no room for struct ip6_reass_helper", hdrerr == 0);
}
#endif
pbuf_cat(ipr->p, next_pbuf);
}
else {
iprh_tmp = NULL;
}
iprh = iprh_tmp;
}
/* Get the first pbuf. */
p = ipr->p;
#if IPV6_FRAG_COPYHEADER
if (IPV6_FRAG_REQROOM > 0) {
u8_t hdrerr;
/* Restore (only) the bytes that we overwrote beyond the fragment header.
* Those bytes may belong to either the IPv6 header or an extension
* header placed before the fragment header. */
MEMCPY(p->payload, ipr->orig_hdr, IPV6_FRAG_REQROOM);
/* get back room for struct ip6_reass_helper (only required if sizeof(void*) > 4) */
hdrerr = pbuf_remove_header(p, IPV6_FRAG_REQROOM);
LWIP_UNUSED_ARG(hdrerr); /* in case of LWIP_NOASSERT */
LWIP_ASSERT("no room for struct ip6_reass_helper", hdrerr == 0);
}
#endif
/* We need to get rid of the fragment header itself, which is somewhere in
* the middle of the packet (but still in the first pbuf of the chain).
* Getting rid of the header is required by RFC 2460 Sec. 4.5 and necessary
* in order to be able to reassemble packets that are close to full size
* (i.e., around 65535 bytes). We simply move up all the headers before the
* fragment header, including the IPv6 header, and adjust the payload start
* accordingly. This works because all these headers are in the first pbuf
* of the chain, and because the caller adjusts all its pointers on
* successful reassembly. */
MEMMOVE((u8_t*)ipr->iphdr + sizeof(struct ip6_frag_hdr), ipr->iphdr,
(size_t)((u8_t*)p->payload - (u8_t*)ipr->iphdr));
/* This is where the IPv6 header is now. */
iphdr_ptr = (struct ip6_hdr*)((u8_t*)ipr->iphdr +
sizeof(struct ip6_frag_hdr));
/* Adjust datagram length by adding header lengths. */
ipr->datagram_len = (u16_t)(ipr->datagram_len + ((u8_t*)p->payload - (u8_t*)iphdr_ptr)
- IP6_HLEN);
/* Set payload length in ip header. */
iphdr_ptr->_plen = lwip_htons(ipr->datagram_len);
/* With the fragment header gone, we now need to adjust the next-header
* field of whatever header was originally before it. Since the packet made
* it through the original header processing routines at least up to the
* fragment header, we do not need any further sanity checks here. */
if (IP6H_NEXTH(iphdr_ptr) == IP6_NEXTH_FRAGMENT) {
iphdr_ptr->_nexth = ipr->nexth;
} else {
u8_t *ptr = (u8_t *)iphdr_ptr + IP6_HLEN;
while (*ptr != IP6_NEXTH_FRAGMENT) {
ptr += 8 * (1 + ptr[1]);
}
*ptr = ipr->nexth;
}
/* release the resources allocated for the fragment queue entry */
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", ipr_prev != NULL);
ipr_prev->next = ipr->next;
}
memp_free(MEMP_IP6_REASSDATA, ipr);
/* adjust the number of pbufs currently queued for reassembly. */
clen = pbuf_clen(p);
LWIP_ASSERT("ip6_reass_pbufcount >= clen", ip6_reass_pbufcount >= clen);
ip6_reass_pbufcount = (u16_t)(ip6_reass_pbufcount - clen);
/* Move pbuf back to IPv6 header. This should never fail. */
if (pbuf_header_force(p, (s16_t)((u8_t*)p->payload - (u8_t*)iphdr_ptr))) {
LWIP_ASSERT("ip6_reass: moving p->payload to ip6 header failed\n", 0);
pbuf_free(p);
return NULL;
}
/* Return the pbuf chain */
return p;
}
/* the datagram is not (yet?) reassembled completely */
return NULL;
nullreturn:
IP6_FRAG_STATS_INC(ip6_frag.drop);
pbuf_free(p);
return NULL;
}
