Move all code related to IP fragment reassembly to ip_reass.c. Some

function names have changed and comments are reformatted or added, but
there is no functional change.

Claim copyright for me and Adrian.

Sponsored by:	Nginx, Inc.

4 files changed, 667 insertions, 562 deletions

diff --git a/sys/conf/files b/sys/conf/files
index 9e63ffe..7ef7afe 100644
--- a/sys/conf/files
+++ b/sys/conf/files
@@ -3485,6 +3485,7 @@ netinet/ip_ipsec.c		optional inet ipsec
 netinet/ip_mroute.c		optional mrouting inet
 netinet/ip_options.c		optional inet
 netinet/ip_output.c		optional inet
+netinet/ip_reass.c		optional inet
 netinet/raw_ip.c		optional inet | inet6
 netinet/cc/cc.c			optional inet | inet6
 netinet/cc/cc_newreno.c		optional inet | inet6
diff --git a/sys/netinet/in_var.h b/sys/netinet/in_var.h
index f7737ec..0318fb2 100644
--- a/sys/netinet/in_var.h
+++ b/sys/netinet/in_var.h
@@ -176,15 +176,6 @@ do {									\
 } while (0)
 
 /*
- * IP datagram reassembly.
- */
-#define	IPREASS_NHASH_LOG2	6
-#define	IPREASS_NHASH		(1 << IPREASS_NHASH_LOG2)
-#define	IPREASS_HMASK		(IPREASS_NHASH - 1)
-#define	IPREASS_HASH(x,y) \
-	(((((x) & 0xF) | ((((x) >> 8) & 0xF) << 4)) ^ (y)) & IPREASS_HMASK)
-
-/*
  * Legacy IPv4 IGMP per-link structure.
  */
 struct router_info {
diff --git a/sys/netinet/ip_input.c b/sys/netinet/ip_input.c
index e28fcc7..1e139a2 100644
--- a/sys/netinet/ip_input.c
+++ b/sys/netinet/ip_input.c
@@ -89,6 +89,14 @@ __FBSDID("$FreeBSD$");
 CTASSERT(sizeof(struct ip) == 20);
 #endif
 
+/* IP reassembly functions are defined in ip_reass.c. */
+extern void ipreass_init();
+extern void ipreass_drain();
+extern void ipreass_slowtimo();
+#ifdef VIMAGE
+extern void ipreass_destroy();
+#endif
+
 struct	rwlock in_ifaddr_lock;
 RW_SYSINIT(in_ifaddr_lock, &in_ifaddr_lock, "in_ifaddr_lock");
 
@@ -164,57 +172,6 @@ VNET_DEFINE(struct in_ifaddrhead, in_ifaddrhead);  /* first inet address */
 VNET_DEFINE(struct in_ifaddrhashhead *, in_ifaddrhashtbl); /* inet addr hash table  */
 VNET_DEFINE(u_long, in_ifaddrhmask);		/* mask for hash table */
 
-static VNET_DEFINE(uma_zone_t, ipq_zone);
-#define	V_ipq_zone	VNET(ipq_zone)
-struct ipqbucket {
-	TAILQ_HEAD(ipqhead, ipq) head;
-	struct mtx		 lock;
-};
-static VNET_DEFINE(struct ipqbucket, ipq[IPREASS_NHASH]);
-#define	V_ipq		VNET(ipq)
-static VNET_DEFINE(int, noreass);
-#define	V_noreass	VNET(noreass)
-
-#define	IPQ_LOCK(i)	mtx_lock(&V_ipq[i].lock)
-#define	IPQ_TRYLOCK(i)	mtx_trylock(&V_ipq[i].lock)
-#define	IPQ_UNLOCK(i)	mtx_unlock(&V_ipq[i].lock)
-#define	IPQ_LOCK_ASSERT(i)	mtx_assert(&V_ipq[i].lock, MA_OWNED)
-
-static int	sysctl_maxfragpackets(SYSCTL_HANDLER_ARGS);
-static void	ipq_zone_change(void *);
-static void	ip_drain_vnet(void);
-static void	ipq_drain_tomax(void);
-static void	ipq_free(struct ipqhead *, struct ipq *);
-
-static inline void
-ipq_timeout(struct ipqhead *head, struct ipq *fp)
-{
-
-	IPSTAT_ADD(ips_fragtimeout, fp->ipq_nfrags);
-	ipq_free(head, fp);
-}
-
-static inline void
-ipq_drop(struct ipqhead *head, struct ipq *fp)
-{
-
-	IPSTAT_ADD(ips_fragdropped, fp->ipq_nfrags);
-	ipq_free(head, fp);
-}
-
-SYSCTL_PROC(_net_inet_ip, OID_AUTO, maxfragpackets, CTLFLAG_VNET |
-    CTLTYPE_INT | CTLFLAG_RW, NULL, 0, sysctl_maxfragpackets, "I",
-    "Maximum number of IPv4 fragment reassembly queue entries");
-SYSCTL_UMA_CUR(_net_inet_ip, OID_AUTO, fragpackets, CTLFLAG_VNET,
-    &VNET_NAME(ipq_zone),
-    "Current number of IPv4 fragment reassembly queue entries");
-
-static VNET_DEFINE(int, maxfragsperpacket);
-#define	V_maxfragsperpacket	VNET(maxfragsperpacket)
-SYSCTL_INT(_net_inet_ip, OID_AUTO, maxfragsperpacket, CTLFLAG_VNET | CTLFLAG_RW,
-    &VNET_NAME(maxfragsperpacket), 0,
-    "Maximum number of IPv4 fragments allowed per packet");
-
 #ifdef IPCTL_DEFMTU
 SYSCTL_INT(_net_inet_ip, IPCTL_DEFMTU, mtu, CTLFLAG_RW,
     &ip_mtu, 0, "Default MTU");
@@ -349,15 +306,7 @@ ip_init(void)
 	V_in_ifaddrhashtbl = hashinit(INADDR_NHASH, M_IFADDR, &V_in_ifaddrhmask);
 
 	/* Initialize IP reassembly queue. */
-	for (i = 0; i < IPREASS_NHASH; i++) {
-		TAILQ_INIT(&V_ipq[i].head);
-		mtx_init(&V_ipq[i].lock, "IP reassembly", NULL,
-		    MTX_DEF | MTX_DUPOK);
-	}
-	V_maxfragsperpacket = 16;
-	V_ipq_zone = uma_zcreate("ipq", sizeof(struct ipq), NULL, NULL, NULL,
-	    NULL, UMA_ALIGN_PTR, 0);
-	uma_zone_set_max(V_ipq_zone, nmbclusters / 32);
+	ipreass_init();
 
 	/* Initialize packet filter hooks. */
 	V_inet_pfil_hook.ph_type = PFIL_TYPE_AF;
@@ -390,9 +339,6 @@ ip_init(void)
 				ip_protox[pr->pr_protocol] = pr - inetsw;
 		}
 
-	EVENTHANDLER_REGISTER(nmbclusters_change, ipq_zone_change,
-		NULL, EVENTHANDLER_PRI_ANY);
-
 	netisr_register(&ip_nh);
 #ifdef	RSS
 	netisr_register(&ip_direct_nh);
@@ -413,10 +359,7 @@ ip_destroy(void)
 	hashdestroy(V_in_ifaddrhashtbl, M_IFADDR, V_in_ifaddrhmask);
 
 	/* Destroy IP reassembly queue. */
-	ip_drain_vnet();
-	uma_zdestroy(V_ipq_zone);
-	for (i = 0; i < IPREASS_NHASH; i++)
-		mtx_destroy(&V_ipq[i].lock);
+	ipreass_destroy();
 }
 #endif
 
@@ -810,466 +753,6 @@ bad:
 }
 
 /*
- * After maxnipq has been updated, propagate the change to UMA.  The UMA zone
- * max has slightly different semantics than the sysctl, for historical
- * reasons.
- */
-static void
-ipq_drain_tomax(void)
-{
-	int target;
-
-	/*
-	 * If we are over the maximum number of fragments,
-	 * drain off enough to get down to the new limit,
-	 * stripping off last elements on queues.  Every
-	 * run we strip the oldest element from each bucket.
-	 */
-	target = uma_zone_get_max(V_ipq_zone);
-	while (uma_zone_get_cur(V_ipq_zone) > target) {
-		struct ipq *fp;
-
-		for (int i = 0; i < IPREASS_NHASH; i++) {
-			IPQ_LOCK(i);
-			fp = TAILQ_LAST(&V_ipq[i].head, ipqhead);
-			if (fp != NULL)
-				ipq_timeout(&V_ipq[i].head, fp);
-			IPQ_UNLOCK(i);
-		}
-	}
-}
-
-static void
-ipq_zone_change(void *tag)
-{
-
-	uma_zone_set_max(V_ipq_zone, nmbclusters / 32);
-	ipq_drain_tomax();
-}
-
-/*
- * Change the limit on the UMA zone, or disable the fragment allocation
- * at all.  Since 0 and -1 is a special values here, we need our own handler,
- * instead of sysctl_handle_uma_zone_max().
- */
-static int
-sysctl_maxfragpackets(SYSCTL_HANDLER_ARGS)
-{
-	int error, max;
-
-	if (V_noreass == 0) {
-		max = uma_zone_get_max(V_ipq_zone);
-		if (max == 0)
-			max = -1;
-	} else 
-		max = 0;
-	error = sysctl_handle_int(oidp, &max, 0, req);
-	if (error || !req->newptr)
-		return (error);
-	if (max > 0) {
-		/*
-		 * XXXRW: Might be a good idea to sanity check the argument
-		 * and place an extreme upper bound.
-		 */
-		max = uma_zone_set_max(V_ipq_zone, max);
-		ipq_drain_tomax();
-		V_noreass = 0;
-	} else if (max == 0) {
-		V_noreass = 1;
-		ip_drain_vnet();
-	} else if (max == -1) {
-		V_noreass = 0;
-		uma_zone_set_max(V_ipq_zone, 0);
-	} else
-		return (EINVAL);
-	return (0);
-}
-
-#define	M_IP_FRAG	M_PROTO9
-
-/*
- * Seek for old fragment queue header that can be reused.  Try to
- * reuse a header from currently locked hash bucket.
- */
-static struct ipq *
-ipq_reuse(int start)
-{
-	struct ipq *fp;
-	int i;
-
-	IPQ_LOCK_ASSERT(start);
-
-	for (i = start;; i++) {
-		if (i == IPREASS_NHASH)
-			i = 0;
-		if (i != start && IPQ_TRYLOCK(i) == 0)
-			continue;
-		fp = TAILQ_LAST(&V_ipq[i].head, ipqhead);
-		if (fp) {
-			struct mbuf *m;
-
-			IPSTAT_ADD(ips_fragtimeout, fp->ipq_nfrags);
-			while (fp->ipq_frags) {
-				m = fp->ipq_frags;
-				fp->ipq_frags = m->m_nextpkt;
-				m_freem(m);
-			}
-			TAILQ_REMOVE(&V_ipq[i].head, fp, ipq_list);
-			if (i != start)
-				IPQ_UNLOCK(i);
-			IPQ_LOCK_ASSERT(start);
-			return (fp);
-		}
-		if (i != start)
-			IPQ_UNLOCK(i);
-	}
-}
-
-/*
- * Take incoming datagram fragment and try to reassemble it into
- * whole datagram.  If the argument is the first fragment or one
- * in between the function will return NULL and store the mbuf
- * in the fragment chain.  If the argument is the last fragment
- * the packet will be reassembled and the pointer to the new
- * mbuf returned for further processing.  Only m_tags attached
- * to the first packet/fragment are preserved.
- * The IP header is *NOT* adjusted out of iplen.
- */
-struct mbuf *
-ip_reass(struct mbuf *m)
-{
-	struct ip *ip;
-	struct mbuf *p, *q, *nq, *t;
-	struct ipq *fp;
-	struct ipqhead *head;
-	int i, hlen, next;
-	u_int8_t ecn, ecn0;
-	u_short hash;
-#ifdef	RSS
-	uint32_t rss_hash, rss_type;
-#endif
-
-	/*
-	 * If no reassembling or maxfragsperpacket are 0,
-	 * never accept fragments.
-	 */
-	if (V_noreass == 1 || V_maxfragsperpacket == 0) {
-		IPSTAT_INC(ips_fragments);
-		IPSTAT_INC(ips_fragdropped);
-		m_freem(m);
-		return (NULL);
-	}
-
-	ip = mtod(m, struct ip *);
-	hlen = ip->ip_hl << 2;
-
-	/*
-	 * Adjust ip_len to not reflect header,
-	 * convert offset of this to bytes.
-	 */
-	ip->ip_len = htons(ntohs(ip->ip_len) - hlen);
-	if (ip->ip_off & htons(IP_MF)) {
-		/*
-		 * Make sure that fragments have a data length
-		 * that's a non-zero multiple of 8 bytes.
-		 */
-		if (ip->ip_len == htons(0) || (ntohs(ip->ip_len) & 0x7) != 0) {
-			IPSTAT_INC(ips_toosmall); /* XXX */
-			IPSTAT_INC(ips_fragdropped);
-			m_freem(m);
-			return (NULL);
-		}
-		m->m_flags |= M_IP_FRAG;
-	} else
-		m->m_flags &= ~M_IP_FRAG;
-	ip->ip_off = htons(ntohs(ip->ip_off) << 3);
-
-	/*
-	 * Attempt reassembly; if it succeeds, proceed.
-	 * ip_reass() will return a different mbuf.
-	 */
-	IPSTAT_INC(ips_fragments);
-	m->m_pkthdr.PH_loc.ptr = ip;
-
-	/*
-	 * Presence of header sizes in mbufs
-	 * would confuse code below.
-	 */
-	m->m_data += hlen;
-	m->m_len -= hlen;
-
-	hash = IPREASS_HASH(ip->ip_src.s_addr, ip->ip_id);
-	head = &V_ipq[hash].head;
-	IPQ_LOCK(hash);
-
-	/*
-	 * Look for queue of fragments
-	 * of this datagram.
-	 */
-	TAILQ_FOREACH(fp, head, ipq_list)
-		if (ip->ip_id == fp->ipq_id &&
-		    ip->ip_src.s_addr == fp->ipq_src.s_addr &&
-		    ip->ip_dst.s_addr == fp->ipq_dst.s_addr &&
-#ifdef MAC
-		    mac_ipq_match(m, fp) &&
-#endif
-		    ip->ip_p == fp->ipq_p)
-			break;
-	/*
-	 * If first fragment to arrive, create a reassembly queue.
-	 */
-	if (fp == NULL) {
-		fp = uma_zalloc(V_ipq_zone, M_NOWAIT);
-		if (fp == NULL)
-			fp = ipq_reuse(hash);
-#ifdef MAC
-		if (mac_ipq_init(fp, M_NOWAIT) != 0) {
-			uma_zfree(V_ipq_zone, fp);
-			fp = NULL;
-			goto dropfrag;
-		}
-		mac_ipq_create(m, fp);
-#endif
-		TAILQ_INSERT_HEAD(head, fp, ipq_list);
-		fp->ipq_nfrags = 1;
-		fp->ipq_ttl = IPFRAGTTL;
-		fp->ipq_p = ip->ip_p;
-		fp->ipq_id = ip->ip_id;
-		fp->ipq_src = ip->ip_src;
-		fp->ipq_dst = ip->ip_dst;
-		fp->ipq_frags = m;
-		m->m_nextpkt = NULL;
-		goto done;
-	} else {
-		fp->ipq_nfrags++;
-#ifdef MAC
-		mac_ipq_update(m, fp);
-#endif
-	}
-
-#define GETIP(m)	((struct ip*)((m)->m_pkthdr.PH_loc.ptr))
-
-	/*
-	 * Handle ECN by comparing this segment with the first one;
-	 * if CE is set, do not lose CE.
-	 * drop if CE and not-ECT are mixed for the same packet.
-	 */
-	ecn = ip->ip_tos & IPTOS_ECN_MASK;
-	ecn0 = GETIP(fp->ipq_frags)->ip_tos & IPTOS_ECN_MASK;
-	if (ecn == IPTOS_ECN_CE) {
-		if (ecn0 == IPTOS_ECN_NOTECT)
-			goto dropfrag;
-		if (ecn0 != IPTOS_ECN_CE)
-			GETIP(fp->ipq_frags)->ip_tos |= IPTOS_ECN_CE;
-	}
-	if (ecn == IPTOS_ECN_NOTECT && ecn0 != IPTOS_ECN_NOTECT)
-		goto dropfrag;
-
-	/*
-	 * Find a segment which begins after this one does.
-	 */
-	for (p = NULL, q = fp->ipq_frags; q; p = q, q = q->m_nextpkt)
-		if (ntohs(GETIP(q)->ip_off) > ntohs(ip->ip_off))
-			break;
-
-	/*
-	 * If there is a preceding segment, it may provide some of
-	 * our data already.  If so, drop the data from the incoming
-	 * segment.  If it provides all of our data, drop us, otherwise
-	 * stick new segment in the proper place.
-	 *
-	 * If some of the data is dropped from the preceding
-	 * segment, then it's checksum is invalidated.
-	 */
-	if (p) {
-		i = ntohs(GETIP(p)->ip_off) + ntohs(GETIP(p)->ip_len) -
-		    ntohs(ip->ip_off);
-		if (i > 0) {
-			if (i >= ntohs(ip->ip_len))
-				goto dropfrag;
-			m_adj(m, i);
-			m->m_pkthdr.csum_flags = 0;
-			ip->ip_off = htons(ntohs(ip->ip_off) + i);
-			ip->ip_len = htons(ntohs(ip->ip_len) - i);
-		}
-		m->m_nextpkt = p->m_nextpkt;
-		p->m_nextpkt = m;
-	} else {
-		m->m_nextpkt = fp->ipq_frags;
-		fp->ipq_frags = m;
-	}
-
-	/*
-	 * While we overlap succeeding segments trim them or,
-	 * if they are completely covered, dequeue them.
-	 */
-	for (; q != NULL && ntohs(ip->ip_off) + ntohs(ip->ip_len) >
-	    ntohs(GETIP(q)->ip_off); q = nq) {
-		i = (ntohs(ip->ip_off) + ntohs(ip->ip_len)) -
-		    ntohs(GETIP(q)->ip_off);
-		if (i < ntohs(GETIP(q)->ip_len)) {
-			GETIP(q)->ip_len = htons(ntohs(GETIP(q)->ip_len) - i);
-			GETIP(q)->ip_off = htons(ntohs(GETIP(q)->ip_off) + i);
-			m_adj(q, i);
-			q->m_pkthdr.csum_flags = 0;
-			break;
-		}
-		nq = q->m_nextpkt;
-		m->m_nextpkt = nq;
-		IPSTAT_INC(ips_fragdropped);
-		fp->ipq_nfrags--;
-		m_freem(q);
-	}
-
-	/*
-	 * Check for complete reassembly and perform frag per packet
-	 * limiting.
-	 *
-	 * Frag limiting is performed here so that the nth frag has
-	 * a chance to complete the packet before we drop the packet.
-	 * As a result, n+1 frags are actually allowed per packet, but
-	 * only n will ever be stored. (n = maxfragsperpacket.)
-	 *
-	 */
-	next = 0;
-	for (p = NULL, q = fp->ipq_frags; q; p = q, q = q->m_nextpkt) {
-		if (ntohs(GETIP(q)->ip_off) != next) {
-			if (fp->ipq_nfrags > V_maxfragsperpacket)
-				ipq_drop(head, fp);
-			goto done;
-		}
-		next += ntohs(GETIP(q)->ip_len);
-	}
-	/* Make sure the last packet didn't have the IP_MF flag */
-	if (p->m_flags & M_IP_FRAG) {
-		if (fp->ipq_nfrags > V_maxfragsperpacket)
-			ipq_drop(head, fp);
-		goto done;
-	}
-
-	/*
-	 * Reassembly is complete.  Make sure the packet is a sane size.
-	 */
-	q = fp->ipq_frags;
-	ip = GETIP(q);
-	if (next + (ip->ip_hl << 2) > IP_MAXPACKET) {
-		IPSTAT_INC(ips_toolong);
-		ipq_drop(head, fp);
-		goto done;
-	}
-
-	/*
-	 * Concatenate fragments.
-	 */
-	m = q;
-	t = m->m_next;
-	m->m_next = NULL;
-	m_cat(m, t);
-	nq = q->m_nextpkt;
-	q->m_nextpkt = NULL;
-	for (q = nq; q != NULL; q = nq) {
-		nq = q->m_nextpkt;
-		q->m_nextpkt = NULL;
-		m->m_pkthdr.csum_flags &= q->m_pkthdr.csum_flags;
-		m->m_pkthdr.csum_data += q->m_pkthdr.csum_data;
-		m_cat(m, q);
-	}
-	/*
-	 * In order to do checksumming faster we do 'end-around carry' here
-	 * (and not in for{} loop), though it implies we are not going to
-	 * reassemble more than 64k fragments.
-	 */
-	while (m->m_pkthdr.csum_data & 0xffff0000)
-		m->m_pkthdr.csum_data = (m->m_pkthdr.csum_data & 0xffff) +
-		    (m->m_pkthdr.csum_data >> 16);
-#ifdef MAC
-	mac_ipq_reassemble(fp, m);
-	mac_ipq_destroy(fp);
-#endif
-
-	/*
-	 * Create header for new ip packet by modifying header of first
-	 * packet;  dequeue and discard fragment reassembly header.
-	 * Make header visible.
-	 */
-	ip->ip_len = htons((ip->ip_hl << 2) + next);
-	ip->ip_src = fp->ipq_src;
-	ip->ip_dst = fp->ipq_dst;
-	TAILQ_REMOVE(head, fp, ipq_list);
-	uma_zfree(V_ipq_zone, fp);
-	m->m_len += (ip->ip_hl << 2);
-	m->m_data -= (ip->ip_hl << 2);
-	/* some debugging cruft by sklower, below, will go away soon */
-	if (m->m_flags & M_PKTHDR)	/* XXX this should be done elsewhere */
-		m_fixhdr(m);
-	IPSTAT_INC(ips_reassembled);
-	IPQ_UNLOCK(hash);
-
-#ifdef	RSS
-	/*
-	 * Query the RSS layer for the flowid / flowtype for the
-	 * mbuf payload.
-	 *
-	 * For now, just assume we have to calculate a new one.
-	 * Later on we should check to see if the assigned flowid matches
-	 * what RSS wants for the given IP protocol and if so, just keep it.
-	 *
-	 * We then queue into the relevant netisr so it can be dispatched
-	 * to the correct CPU.
-	 *
-	 * Note - this may return 1, which means the flowid in the mbuf
-	 * is correct for the configured RSS hash types and can be used.
-	 */
-	if (rss_mbuf_software_hash_v4(m, 0, &rss_hash, &rss_type) == 0) {
-		m->m_pkthdr.flowid = rss_hash;
-		M_HASHTYPE_SET(m, rss_type);
-	}
-
-	/*
-	 * Queue/dispatch for reprocessing.
-	 *
-	 * Note: this is much slower than just handling the frame in the
-	 * current receive context.  It's likely worth investigating
-	 * why this is.
-	 */
-	netisr_dispatch(NETISR_IP_DIRECT, m);
-	return (NULL);
-#endif
-
-	/* Handle in-line */
-	return (m);
-
-dropfrag:
-	IPSTAT_INC(ips_fragdropped);
-	if (fp != NULL)
-		fp->ipq_nfrags--;
-	m_freem(m);
-done:
-	IPQ_UNLOCK(hash);
-	return (NULL);
-
-#undef GETIP
-}
-
-/*
- * Free a fragment reassembly header and all
- * associated datagrams.
- */
-static void
-ipq_free(struct ipqhead *fhp, struct ipq *fp)
-{
-	struct mbuf *q;
-
-	while (fp->ipq_frags) {
-		q = fp->ipq_frags;
-		fp->ipq_frags = q->m_nextpkt;
-		m_freem(q);
-	}
-	TAILQ_REMOVE(fhp, fp, ipq_list);
-	uma_zfree(V_ipq_zone, fp);
-}
-
-/*
  * IP timer processing;
  * if a timer expires on a reassembly
  * queue, discard it.
@@ -1278,40 +761,16 @@ void
 ip_slowtimo(void)
 {
 	VNET_ITERATOR_DECL(vnet_iter);
-	struct ipq *fp, *tmp;
-	int i;
 
 	VNET_LIST_RLOCK_NOSLEEP();
 	VNET_FOREACH(vnet_iter) {
 		CURVNET_SET(vnet_iter);
-		for (i = 0; i < IPREASS_NHASH; i++) {
-			IPQ_LOCK(i);
-			TAILQ_FOREACH_SAFE(fp, &V_ipq[i].head, ipq_list, tmp)
-				if (--fp->ipq_ttl == 0)
-					ipq_timeout(&V_ipq[i].head, fp);
-			IPQ_UNLOCK(i);
-		}
+		ipreass_slowtimo();
 		CURVNET_RESTORE();
 	}
 	VNET_LIST_RUNLOCK_NOSLEEP();
 }
 
-/*
- * Drain off all datagram fragments.
- */
-static void
-ip_drain_vnet(void)
-{
-	int     i;
-
-	for (i = 0; i < IPREASS_NHASH; i++) {
-		IPQ_LOCK(i);
-		while(!TAILQ_EMPTY(&V_ipq[i].head))
-			ipq_drop(&V_ipq[i].head, TAILQ_FIRST(&V_ipq[i].head));
-		IPQ_UNLOCK(i);
-	}
-}
-
 void
 ip_drain(void)
 {
@@ -1320,7 +779,7 @@ ip_drain(void)
 	VNET_LIST_RLOCK_NOSLEEP();
 	VNET_FOREACH(vnet_iter) {
 		CURVNET_SET(vnet_iter);
-		ip_drain_vnet();
+		ipreass_drain();
 		CURVNET_RESTORE();
 	}
 	VNET_LIST_RUNLOCK_NOSLEEP();
diff --git a/sys/netinet/ip_reass.c b/sys/netinet/ip_reass.c
new file mode 100644
index 0000000..a7c5d38
--- /dev/null
+++ b/sys/netinet/ip_reass.c
@@ -0,0 +1,654 @@
+/*-
+ * Copyright (c) 2015 Gleb Smirnoff <glebius@FreeBSD.org>
+ * Copyright (c) 2015 Adrian Chadd <adrian@FreeBSD.org>
+ * Copyright (c) 1982, 1986, 1988, 1993
+ *	The Regents of the University of California.  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.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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.
+ *
+ *	@(#)ip_input.c	8.2 (Berkeley) 1/4/94
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include "opt_rss.h"
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/eventhandler.h>
+#include <sys/mbuf.h>
+#include <sys/malloc.h>
+#include <sys/lock.h>
+#include <sys/mutex.h>
+#include <sys/sysctl.h>
+
+#include <net/rss_config.h>
+#include <net/vnet.h>
+
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/ip_var.h>
+#include <netinet/in_rss.h>
+#ifdef MAC
+#include <security/mac/mac_framework.h>
+#endif
+
+SYSCTL_DECL(_net_inet_ip);
+
+/*
+ * Reassembly headers are stored in hash buckets.
+ */
+#define	IPREASS_NHASH_LOG2	6
+#define	IPREASS_NHASH		(1 << IPREASS_NHASH_LOG2)
+#define	IPREASS_HMASK		(IPREASS_NHASH - 1)
+#define	IPREASS_HASH(x,y) \
+	(((((x) & 0xF) | ((((x) >> 8) & 0xF) << 4)) ^ (y)) & IPREASS_HMASK)
+
+struct ipqbucket {
+	TAILQ_HEAD(ipqhead, ipq) head;
+	struct mtx		 lock;
+};
+
+static VNET_DEFINE(struct ipqbucket, ipq[IPREASS_NHASH]);
+#define	V_ipq		VNET(ipq)
+
+#define	IPQ_LOCK(i)	mtx_lock(&V_ipq[i].lock)
+#define	IPQ_TRYLOCK(i)	mtx_trylock(&V_ipq[i].lock)
+#define	IPQ_UNLOCK(i)	mtx_unlock(&V_ipq[i].lock)
+#define	IPQ_LOCK_ASSERT(i)	mtx_assert(&V_ipq[i].lock, MA_OWNED)
+
+void		ipreass_init(void);
+void		ipreass_drain(void);
+void		ipreass_slowtimo(void);
+#ifdef VIMAGE
+void		ipreass_destroy(void);
+#endif
+static int	sysctl_maxfragpackets(SYSCTL_HANDLER_ARGS);
+static void	ipreass_zone_change(void *);
+static void	ipreass_drain_tomax(void);
+static void	ipq_free(struct ipqhead *, struct ipq *);
+static struct ipq * ipq_reuse(int);
+
+static inline void
+ipq_timeout(struct ipqhead *head, struct ipq *fp)
+{
+
+	IPSTAT_ADD(ips_fragtimeout, fp->ipq_nfrags);
+	ipq_free(head, fp);
+}
+
+static inline void
+ipq_drop(struct ipqhead *head, struct ipq *fp)
+{
+
+	IPSTAT_ADD(ips_fragdropped, fp->ipq_nfrags);
+	ipq_free(head, fp);
+}
+
+static VNET_DEFINE(uma_zone_t, ipq_zone);
+#define	V_ipq_zone	VNET(ipq_zone)
+SYSCTL_PROC(_net_inet_ip, OID_AUTO, maxfragpackets, CTLFLAG_VNET |
+    CTLTYPE_INT | CTLFLAG_RW, NULL, 0, sysctl_maxfragpackets, "I",
+    "Maximum number of IPv4 fragment reassembly queue entries");
+SYSCTL_UMA_CUR(_net_inet_ip, OID_AUTO, fragpackets, CTLFLAG_VNET,
+    &VNET_NAME(ipq_zone),
+    "Current number of IPv4 fragment reassembly queue entries");
+
+static VNET_DEFINE(int, noreass);
+#define	V_noreass	VNET(noreass)
+
+static VNET_DEFINE(int, maxfragsperpacket);
+#define	V_maxfragsperpacket	VNET(maxfragsperpacket)
+SYSCTL_INT(_net_inet_ip, OID_AUTO, maxfragsperpacket, CTLFLAG_VNET | CTLFLAG_RW,
+    &VNET_NAME(maxfragsperpacket), 0,
+    "Maximum number of IPv4 fragments allowed per packet");
+
+/*
+ * Take incoming datagram fragment and try to reassemble it into
+ * whole datagram.  If the argument is the first fragment or one
+ * in between the function will return NULL and store the mbuf
+ * in the fragment chain.  If the argument is the last fragment
+ * the packet will be reassembled and the pointer to the new
+ * mbuf returned for further processing.  Only m_tags attached
+ * to the first packet/fragment are preserved.
+ * The IP header is *NOT* adjusted out of iplen.
+ */
+#define	M_IP_FRAG	M_PROTO9
+struct mbuf *
+ip_reass(struct mbuf *m)
+{
+	struct ip *ip;
+	struct mbuf *p, *q, *nq, *t;
+	struct ipq *fp;
+	struct ipqhead *head;
+	int i, hlen, next;
+	u_int8_t ecn, ecn0;
+	u_short hash;
+#ifdef	RSS
+	uint32_t rss_hash, rss_type;
+#endif
+
+	/*
+	 * If no reassembling or maxfragsperpacket are 0,
+	 * never accept fragments.
+	 */
+	if (V_noreass == 1 || V_maxfragsperpacket == 0) {
+		IPSTAT_INC(ips_fragments);
+		IPSTAT_INC(ips_fragdropped);
+		m_freem(m);
+		return (NULL);
+	}
+
+	ip = mtod(m, struct ip *);
+	hlen = ip->ip_hl << 2;
+
+	/*
+	 * Adjust ip_len to not reflect header,
+	 * convert offset of this to bytes.
+	 */
+	ip->ip_len = htons(ntohs(ip->ip_len) - hlen);
+	if (ip->ip_off & htons(IP_MF)) {
+		/*
+		 * Make sure that fragments have a data length
+		 * that's a non-zero multiple of 8 bytes.
+		 */
+		if (ip->ip_len == htons(0) || (ntohs(ip->ip_len) & 0x7) != 0) {
+			IPSTAT_INC(ips_toosmall); /* XXX */
+			IPSTAT_INC(ips_fragdropped);
+			m_freem(m);
+			return (NULL);
+		}
+		m->m_flags |= M_IP_FRAG;
+	} else
+		m->m_flags &= ~M_IP_FRAG;
+	ip->ip_off = htons(ntohs(ip->ip_off) << 3);
+
+	/*
+	 * Attempt reassembly; if it succeeds, proceed.
+	 * ip_reass() will return a different mbuf.
+	 */
+	IPSTAT_INC(ips_fragments);
+	m->m_pkthdr.PH_loc.ptr = ip;
+
+	/*
+	 * Presence of header sizes in mbufs
+	 * would confuse code below.
+	 */
+	m->m_data += hlen;
+	m->m_len -= hlen;
+
+	hash = IPREASS_HASH(ip->ip_src.s_addr, ip->ip_id);
+	head = &V_ipq[hash].head;
+	IPQ_LOCK(hash);
+
+	/*
+	 * Look for queue of fragments
+	 * of this datagram.
+	 */
+	TAILQ_FOREACH(fp, head, ipq_list)
+		if (ip->ip_id == fp->ipq_id &&
+		    ip->ip_src.s_addr == fp->ipq_src.s_addr &&
+		    ip->ip_dst.s_addr == fp->ipq_dst.s_addr &&
+#ifdef MAC
+		    mac_ipq_match(m, fp) &&
+#endif
+		    ip->ip_p == fp->ipq_p)
+			break;
+	/*
+	 * If first fragment to arrive, create a reassembly queue.
+	 */
+	if (fp == NULL) {
+		fp = uma_zalloc(V_ipq_zone, M_NOWAIT);
+		if (fp == NULL)
+			fp = ipq_reuse(hash);
+#ifdef MAC
+		if (mac_ipq_init(fp, M_NOWAIT) != 0) {
+			uma_zfree(V_ipq_zone, fp);
+			fp = NULL;
+			goto dropfrag;
+		}
+		mac_ipq_create(m, fp);
+#endif
+		TAILQ_INSERT_HEAD(head, fp, ipq_list);
+		fp->ipq_nfrags = 1;
+		fp->ipq_ttl = IPFRAGTTL;
+		fp->ipq_p = ip->ip_p;
+		fp->ipq_id = ip->ip_id;
+		fp->ipq_src = ip->ip_src;
+		fp->ipq_dst = ip->ip_dst;
+		fp->ipq_frags = m;
+		m->m_nextpkt = NULL;
+		goto done;
+	} else {
+		fp->ipq_nfrags++;
+#ifdef MAC
+		mac_ipq_update(m, fp);
+#endif
+	}
+
+#define GETIP(m)	((struct ip*)((m)->m_pkthdr.PH_loc.ptr))
+
+	/*
+	 * Handle ECN by comparing this segment with the first one;
+	 * if CE is set, do not lose CE.
+	 * drop if CE and not-ECT are mixed for the same packet.
+	 */
+	ecn = ip->ip_tos & IPTOS_ECN_MASK;
+	ecn0 = GETIP(fp->ipq_frags)->ip_tos & IPTOS_ECN_MASK;
+	if (ecn == IPTOS_ECN_CE) {
+		if (ecn0 == IPTOS_ECN_NOTECT)
+			goto dropfrag;
+		if (ecn0 != IPTOS_ECN_CE)
+			GETIP(fp->ipq_frags)->ip_tos |= IPTOS_ECN_CE;
+	}
+	if (ecn == IPTOS_ECN_NOTECT && ecn0 != IPTOS_ECN_NOTECT)
+		goto dropfrag;
+
+	/*
+	 * Find a segment which begins after this one does.
+	 */
+	for (p = NULL, q = fp->ipq_frags; q; p = q, q = q->m_nextpkt)
+		if (ntohs(GETIP(q)->ip_off) > ntohs(ip->ip_off))
+			break;
+
+	/*
+	 * If there is a preceding segment, it may provide some of
+	 * our data already.  If so, drop the data from the incoming
+	 * segment.  If it provides all of our data, drop us, otherwise
+	 * stick new segment in the proper place.
+	 *
+	 * If some of the data is dropped from the preceding
+	 * segment, then it's checksum is invalidated.
+	 */
+	if (p) {
+		i = ntohs(GETIP(p)->ip_off) + ntohs(GETIP(p)->ip_len) -
+		    ntohs(ip->ip_off);
+		if (i > 0) {
+			if (i >= ntohs(ip->ip_len))
+				goto dropfrag;
+			m_adj(m, i);
+			m->m_pkthdr.csum_flags = 0;
+			ip->ip_off = htons(ntohs(ip->ip_off) + i);
+			ip->ip_len = htons(ntohs(ip->ip_len) - i);
+		}
+		m->m_nextpkt = p->m_nextpkt;
+		p->m_nextpkt = m;
+	} else {
+		m->m_nextpkt = fp->ipq_frags;
+		fp->ipq_frags = m;
+	}
+
+	/*
+	 * While we overlap succeeding segments trim them or,
+	 * if they are completely covered, dequeue them.
+	 */
+	for (; q != NULL && ntohs(ip->ip_off) + ntohs(ip->ip_len) >
+	    ntohs(GETIP(q)->ip_off); q = nq) {
+		i = (ntohs(ip->ip_off) + ntohs(ip->ip_len)) -
+		    ntohs(GETIP(q)->ip_off);
+		if (i < ntohs(GETIP(q)->ip_len)) {
+			GETIP(q)->ip_len = htons(ntohs(GETIP(q)->ip_len) - i);
+			GETIP(q)->ip_off = htons(ntohs(GETIP(q)->ip_off) + i);
+			m_adj(q, i);
+			q->m_pkthdr.csum_flags = 0;
+			break;
+		}
+		nq = q->m_nextpkt;
+		m->m_nextpkt = nq;
+		IPSTAT_INC(ips_fragdropped);
+		fp->ipq_nfrags--;
+		m_freem(q);
+	}
+
+	/*
+	 * Check for complete reassembly and perform frag per packet
+	 * limiting.
+	 *
+	 * Frag limiting is performed here so that the nth frag has
+	 * a chance to complete the packet before we drop the packet.
+	 * As a result, n+1 frags are actually allowed per packet, but
+	 * only n will ever be stored. (n = maxfragsperpacket.)
+	 *
+	 */
+	next = 0;
+	for (p = NULL, q = fp->ipq_frags; q; p = q, q = q->m_nextpkt) {
+		if (ntohs(GETIP(q)->ip_off) != next) {
+			if (fp->ipq_nfrags > V_maxfragsperpacket)
+				ipq_drop(head, fp);
+			goto done;
+		}
+		next += ntohs(GETIP(q)->ip_len);
+	}
+	/* Make sure the last packet didn't have the IP_MF flag */
+	if (p->m_flags & M_IP_FRAG) {
+		if (fp->ipq_nfrags > V_maxfragsperpacket)
+			ipq_drop(head, fp);
+		goto done;
+	}
+
+	/*
+	 * Reassembly is complete.  Make sure the packet is a sane size.
+	 */
+	q = fp->ipq_frags;
+	ip = GETIP(q);
+	if (next + (ip->ip_hl << 2) > IP_MAXPACKET) {
+		IPSTAT_INC(ips_toolong);
+		ipq_drop(head, fp);
+		goto done;
+	}
+
+	/*
+	 * Concatenate fragments.
+	 */
+	m = q;
+	t = m->m_next;
+	m->m_next = NULL;
+	m_cat(m, t);
+	nq = q->m_nextpkt;
+	q->m_nextpkt = NULL;
+	for (q = nq; q != NULL; q = nq) {
+		nq = q->m_nextpkt;
+		q->m_nextpkt = NULL;
+		m->m_pkthdr.csum_flags &= q->m_pkthdr.csum_flags;
+		m->m_pkthdr.csum_data += q->m_pkthdr.csum_data;
+		m_cat(m, q);
+	}
+	/*
+	 * In order to do checksumming faster we do 'end-around carry' here
+	 * (and not in for{} loop), though it implies we are not going to
+	 * reassemble more than 64k fragments.
+	 */
+	while (m->m_pkthdr.csum_data & 0xffff0000)
+		m->m_pkthdr.csum_data = (m->m_pkthdr.csum_data & 0xffff) +
+		    (m->m_pkthdr.csum_data >> 16);
+#ifdef MAC
+	mac_ipq_reassemble(fp, m);
+	mac_ipq_destroy(fp);
+#endif
+
+	/*
+	 * Create header for new ip packet by modifying header of first
+	 * packet;  dequeue and discard fragment reassembly header.
+	 * Make header visible.
+	 */
+	ip->ip_len = htons((ip->ip_hl << 2) + next);
+	ip->ip_src = fp->ipq_src;
+	ip->ip_dst = fp->ipq_dst;
+	TAILQ_REMOVE(head, fp, ipq_list);
+	uma_zfree(V_ipq_zone, fp);
+	m->m_len += (ip->ip_hl << 2);
+	m->m_data -= (ip->ip_hl << 2);
+	/* some debugging cruft by sklower, below, will go away soon */
+	if (m->m_flags & M_PKTHDR)	/* XXX this should be done elsewhere */
+		m_fixhdr(m);
+	IPSTAT_INC(ips_reassembled);
+	IPQ_UNLOCK(hash);
+
+#ifdef	RSS
+	/*
+	 * Query the RSS layer for the flowid / flowtype for the
+	 * mbuf payload.
+	 *
+	 * For now, just assume we have to calculate a new one.
+	 * Later on we should check to see if the assigned flowid matches
+	 * what RSS wants for the given IP protocol and if so, just keep it.
+	 *
+	 * We then queue into the relevant netisr so it can be dispatched
+	 * to the correct CPU.
+	 *
+	 * Note - this may return 1, which means the flowid in the mbuf
+	 * is correct for the configured RSS hash types and can be used.
+	 */
+	if (rss_mbuf_software_hash_v4(m, 0, &rss_hash, &rss_type) == 0) {
+		m->m_pkthdr.flowid = rss_hash;
+		M_HASHTYPE_SET(m, rss_type);
+	}
+
+	/*
+	 * Queue/dispatch for reprocessing.
+	 *
+	 * Note: this is much slower than just handling the frame in the
+	 * current receive context.  It's likely worth investigating
+	 * why this is.
+	 */
+	netisr_dispatch(NETISR_IP_DIRECT, m);
+	return (NULL);
+#endif
+
+	/* Handle in-line */
+	return (m);
+
+dropfrag:
+	IPSTAT_INC(ips_fragdropped);
+	if (fp != NULL)
+		fp->ipq_nfrags--;
+	m_freem(m);
+done:
+	IPQ_UNLOCK(hash);
+	return (NULL);
+
+#undef GETIP
+}
+
+/*
+ * Initialize IP reassembly structures.
+ */
+void
+ipreass_init(void)
+{
+
+	for (int i = 0; i < IPREASS_NHASH; i++) {
+		TAILQ_INIT(&V_ipq[i].head);
+		mtx_init(&V_ipq[i].lock, "IP reassembly", NULL,
+		    MTX_DEF | MTX_DUPOK);
+	}
+	V_maxfragsperpacket = 16;
+	V_ipq_zone = uma_zcreate("ipq", sizeof(struct ipq), NULL, NULL, NULL,
+	    NULL, UMA_ALIGN_PTR, 0);
+	uma_zone_set_max(V_ipq_zone, nmbclusters / 32);
+
+	if (IS_DEFAULT_VNET(curvnet))
+		EVENTHANDLER_REGISTER(nmbclusters_change, ipreass_zone_change,
+		    NULL, EVENTHANDLER_PRI_ANY);
+}
+
+/*
+ * If a timer expires on a reassembly queue, discard it.
+ */
+void
+ipreass_slowtimo(void)
+{
+	struct ipq *fp, *tmp;
+
+	for (int i = 0; i < IPREASS_NHASH; i++) {
+		IPQ_LOCK(i);
+		TAILQ_FOREACH_SAFE(fp, &V_ipq[i].head, ipq_list, tmp)
+		if (--fp->ipq_ttl == 0)
+				ipq_timeout(&V_ipq[i].head, fp);
+		IPQ_UNLOCK(i);
+	}
+}
+
+/*
+ * Drain off all datagram fragments.
+ */
+void
+ipreass_drain(void)
+{
+
+	for (int i = 0; i < IPREASS_NHASH; i++) {
+		IPQ_LOCK(i);
+		while(!TAILQ_EMPTY(&V_ipq[i].head))
+			ipq_drop(&V_ipq[i].head, TAILQ_FIRST(&V_ipq[i].head));
+		IPQ_UNLOCK(i);
+	}
+}
+
+#ifdef VIMAGE
+/*
+ * Destroy IP reassembly structures.
+ */
+void
+ipreass_destroy(void)
+{
+
+	ipreass_drain();
+	uma_zdestroy(V_ipq_zone);
+	for (int i = 0; i < IPREASS_NHASH; i++)
+		mtx_destroy(&V_ipq[i].lock);
+}
+#endif
+
+/*
+ * After maxnipq has been updated, propagate the change to UMA.  The UMA zone
+ * max has slightly different semantics than the sysctl, for historical
+ * reasons.
+ */
+static void
+ipreass_drain_tomax(void)
+{
+	int target;
+
+	/*
+	 * If we are over the maximum number of fragments,
+	 * drain off enough to get down to the new limit,
+	 * stripping off last elements on queues.  Every
+	 * run we strip the oldest element from each bucket.
+	 */
+	target = uma_zone_get_max(V_ipq_zone);
+	while (uma_zone_get_cur(V_ipq_zone) > target) {
+		struct ipq *fp;
+
+		for (int i = 0; i < IPREASS_NHASH; i++) {
+			IPQ_LOCK(i);
+			fp = TAILQ_LAST(&V_ipq[i].head, ipqhead);
+			if (fp != NULL)
+				ipq_timeout(&V_ipq[i].head, fp);
+			IPQ_UNLOCK(i);
+		}
+	}
+}
+
+static void
+ipreass_zone_change(void *tag)
+{
+
+	uma_zone_set_max(V_ipq_zone, nmbclusters / 32);
+	ipreass_drain_tomax();
+}
+
+/*
+ * Change the limit on the UMA zone, or disable the fragment allocation
+ * at all.  Since 0 and -1 is a special values here, we need our own handler,
+ * instead of sysctl_handle_uma_zone_max().
+ */
+static int
+sysctl_maxfragpackets(SYSCTL_HANDLER_ARGS)
+{
+	int error, max;
+
+	if (V_noreass == 0) {
+		max = uma_zone_get_max(V_ipq_zone);
+		if (max == 0)
+			max = -1;
+	} else 
+		max = 0;
+	error = sysctl_handle_int(oidp, &max, 0, req);
+	if (error || !req->newptr)
+		return (error);
+	if (max > 0) {
+		/*
+		 * XXXRW: Might be a good idea to sanity check the argument
+		 * and place an extreme upper bound.
+		 */
+		max = uma_zone_set_max(V_ipq_zone, max);
+		ipreass_drain_tomax();
+		V_noreass = 0;
+	} else if (max == 0) {
+		V_noreass = 1;
+		ipreass_drain();
+	} else if (max == -1) {
+		V_noreass = 0;
+		uma_zone_set_max(V_ipq_zone, 0);
+	} else
+		return (EINVAL);
+	return (0);
+}
+
+/*
+ * Seek for old fragment queue header that can be reused.  Try to
+ * reuse a header from currently locked hash bucket.
+ */
+static struct ipq *
+ipq_reuse(int start)
+{
+	struct ipq *fp;
+	int i;
+
+	IPQ_LOCK_ASSERT(start);
+
+	for (i = start;; i++) {
+		if (i == IPREASS_NHASH)
+			i = 0;
+		if (i != start && IPQ_TRYLOCK(i) == 0)
+			continue;
+		fp = TAILQ_LAST(&V_ipq[i].head, ipqhead);
+		if (fp) {
+			struct mbuf *m;
+
+			IPSTAT_ADD(ips_fragtimeout, fp->ipq_nfrags);
+			while (fp->ipq_frags) {
+				m = fp->ipq_frags;
+				fp->ipq_frags = m->m_nextpkt;
+				m_freem(m);
+			}
+			TAILQ_REMOVE(&V_ipq[i].head, fp, ipq_list);
+			if (i != start)
+				IPQ_UNLOCK(i);
+			IPQ_LOCK_ASSERT(start);
+			return (fp);
+		}
+		if (i != start)
+			IPQ_UNLOCK(i);
+	}
+}
+
+/*
+ * Free a fragment reassembly header and all associated datagrams.
+ */
+static void
+ipq_free(struct ipqhead *fhp, struct ipq *fp)
+{
+	struct mbuf *q;
+
+	while (fp->ipq_frags) {
+		q = fp->ipq_frags;
+		fp->ipq_frags = q->m_nextpkt;
+		m_freem(q);
+	}
+	TAILQ_REMOVE(fhp, fp, ipq_list);
+	uma_zfree(V_ipq_zone, fp);
+}