[NETFILTER]: Add nf_conntrack subsystem.

The existing connection tracking subsystem in netfilter can only
handle ipv4.  There were basically two choices present to add
connection tracking support for ipv6.  We could either duplicate all
of the ipv4 connection tracking code into an ipv6 counterpart, or (the
choice taken by these patches) we could design a generic layer that
could handle both ipv4 and ipv6 and thus requiring only one sub-protocol
(TCP, UDP, etc.) connection tracking helper module to be written.

In fact nf_conntrack is capable of working with any layer 3
protocol.

The existing ipv4 specific conntrack code could also not deal
with the pecularities of doing connection tracking on ipv6,
which is also cured here.  For example, these issues include:

1) ICMPv6 handling, which is used for neighbour discovery in
   ipv6 thus some messages such as these should not participate
   in connection tracking since effectively they are like ARP
   messages

2) fragmentation must be handled differently in ipv6, because
   the simplistic "defrag, connection track and NAT, refrag"
   (which the existing ipv4 connection tracking does) approach simply
   isn't feasible in ipv6

3) ipv6 extension header parsing must occur at the correct spots
   before and after connection tracking decisions, and there were
   no provisions for this in the existing connection tracking
   design

4) ipv6 has no need for stateful NAT

The ipv4 specific conntrack layer is kept around, until all of
the ipv4 specific conntrack helpers are ported over to nf_conntrack
and it is feature complete.  Once that occurs, the old conntrack
stuff will get placed into the feature-removal-schedule and we will
fully kill it off 6 months later.

Signed-off-by: Yasuyuki Kozakai <yasuyuki.kozakai@toshiba.co.jp>
Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>

1 files changed, 885 insertions, 0 deletions

diff --git a/net/ipv6/netfilter/nf_conntrack_reasm.c b/net/ipv6/netfilter/nf_conntrack_reasm.c
new file mode 100644
index 0000000000000..7640b9bb76949
--- /dev/null
+++ b/net/ipv6/netfilter/nf_conntrack_reasm.c
@@ -0,0 +1,885 @@
+/*
+ * IPv6 fragment reassembly for connection tracking
+ *
+ * Copyright (C)2004 USAGI/WIDE Project
+ *
+ * Author:
+ *	Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
+ *
+ * Based on: net/ipv6/reassembly.c
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/config.h>
+#include <linux/errno.h>
+#include <linux/types.h>
+#include <linux/string.h>
+#include <linux/socket.h>
+#include <linux/sockios.h>
+#include <linux/jiffies.h>
+#include <linux/net.h>
+#include <linux/list.h>
+#include <linux/netdevice.h>
+#include <linux/in6.h>
+#include <linux/ipv6.h>
+#include <linux/icmpv6.h>
+#include <linux/random.h>
+#include <linux/jhash.h>
+
+#include <net/sock.h>
+#include <net/snmp.h>
+
+#include <net/ipv6.h>
+#include <net/protocol.h>
+#include <net/transp_v6.h>
+#include <net/rawv6.h>
+#include <net/ndisc.h>
+#include <net/addrconf.h>
+#include <linux/sysctl.h>
+#include <linux/netfilter.h>
+#include <linux/netfilter_ipv6.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+#if 0
+#define DEBUGP printk
+#else
+#define DEBUGP(format, args...)
+#endif
+
+#define NF_CT_FRAG6_HIGH_THRESH 262144 /* == 256*1024 */
+#define NF_CT_FRAG6_LOW_THRESH 196608  /* == 192*1024 */
+#define NF_CT_FRAG6_TIMEOUT IPV6_FRAG_TIMEOUT
+
+int nf_ct_frag6_high_thresh = 256*1024;
+int nf_ct_frag6_low_thresh = 192*1024;
+int nf_ct_frag6_timeout = IPV6_FRAG_TIMEOUT;
+
+struct nf_ct_frag6_skb_cb
+{
+	struct inet6_skb_parm	h;
+	int			offset;
+	struct sk_buff		*orig;
+};
+
+#define NFCT_FRAG6_CB(skb)	((struct nf_ct_frag6_skb_cb*)((skb)->cb))
+
+struct nf_ct_frag6_queue
+{
+	struct nf_ct_frag6_queue	*next;
+	struct list_head lru_list;		/* lru list member	*/
+
+	__u32			id;		/* fragment id		*/
+	struct in6_addr		saddr;
+	struct in6_addr		daddr;
+
+	spinlock_t		lock;
+	atomic_t		refcnt;
+	struct timer_list	timer;		/* expire timer		*/
+	struct sk_buff		*fragments;
+	int			len;
+	int			meat;
+	struct timeval		stamp;
+	unsigned int		csum;
+	__u8			last_in;	/* has first/last segment arrived? */
+#define COMPLETE		4
+#define FIRST_IN		2
+#define LAST_IN			1
+	__u16			nhoffset;
+	struct nf_ct_frag6_queue	**pprev;
+};
+
+/* Hash table. */
+
+#define FRAG6Q_HASHSZ	64
+
+static struct nf_ct_frag6_queue *nf_ct_frag6_hash[FRAG6Q_HASHSZ];
+static rwlock_t nf_ct_frag6_lock = RW_LOCK_UNLOCKED;
+static u32 nf_ct_frag6_hash_rnd;
+static LIST_HEAD(nf_ct_frag6_lru_list);
+int nf_ct_frag6_nqueues = 0;
+
+static __inline__ void __fq_unlink(struct nf_ct_frag6_queue *fq)
+{
+	if (fq->next)
+		fq->next->pprev = fq->pprev;
+	*fq->pprev = fq->next;
+	list_del(&fq->lru_list);
+	nf_ct_frag6_nqueues--;
+}
+
+static __inline__ void fq_unlink(struct nf_ct_frag6_queue *fq)
+{
+	write_lock(&nf_ct_frag6_lock);
+	__fq_unlink(fq);
+	write_unlock(&nf_ct_frag6_lock);
+}
+
+static unsigned int ip6qhashfn(u32 id, struct in6_addr *saddr,
+			       struct in6_addr *daddr)
+{
+	u32 a, b, c;
+
+	a = saddr->s6_addr32[0];
+	b = saddr->s6_addr32[1];
+	c = saddr->s6_addr32[2];
+
+	a += JHASH_GOLDEN_RATIO;
+	b += JHASH_GOLDEN_RATIO;
+	c += nf_ct_frag6_hash_rnd;
+	__jhash_mix(a, b, c);
+
+	a += saddr->s6_addr32[3];
+	b += daddr->s6_addr32[0];
+	c += daddr->s6_addr32[1];
+	__jhash_mix(a, b, c);
+
+	a += daddr->s6_addr32[2];
+	b += daddr->s6_addr32[3];
+	c += id;
+	__jhash_mix(a, b, c);
+
+	return c & (FRAG6Q_HASHSZ - 1);
+}
+
+static struct timer_list nf_ct_frag6_secret_timer;
+int nf_ct_frag6_secret_interval = 10 * 60 * HZ;
+
+static void nf_ct_frag6_secret_rebuild(unsigned long dummy)
+{
+	unsigned long now = jiffies;
+	int i;
+
+	write_lock(&nf_ct_frag6_lock);
+	get_random_bytes(&nf_ct_frag6_hash_rnd, sizeof(u32));
+	for (i = 0; i < FRAG6Q_HASHSZ; i++) {
+		struct nf_ct_frag6_queue *q;
+
+		q = nf_ct_frag6_hash[i];
+		while (q) {
+			struct nf_ct_frag6_queue *next = q->next;
+			unsigned int hval = ip6qhashfn(q->id,
+						       &q->saddr,
+						       &q->daddr);
+
+			if (hval != i) {
+				/* Unlink. */
+				if (q->next)
+					q->next->pprev = q->pprev;
+				*q->pprev = q->next;
+
+				/* Relink to new hash chain. */
+				if ((q->next = nf_ct_frag6_hash[hval]) != NULL)
+					q->next->pprev = &q->next;
+				nf_ct_frag6_hash[hval] = q;
+				q->pprev = &nf_ct_frag6_hash[hval];
+			}
+
+			q = next;
+		}
+	}
+	write_unlock(&nf_ct_frag6_lock);
+
+	mod_timer(&nf_ct_frag6_secret_timer, now + nf_ct_frag6_secret_interval);
+}
+
+atomic_t nf_ct_frag6_mem = ATOMIC_INIT(0);
+
+/* Memory Tracking Functions. */
+static inline void frag_kfree_skb(struct sk_buff *skb)
+{
+	atomic_sub(skb->truesize, &nf_ct_frag6_mem);
+	if (NFCT_FRAG6_CB(skb)->orig)
+		kfree_skb(NFCT_FRAG6_CB(skb)->orig);
+
+	kfree_skb(skb);
+}
+
+static inline void frag_free_queue(struct nf_ct_frag6_queue *fq)
+{
+	atomic_sub(sizeof(struct nf_ct_frag6_queue), &nf_ct_frag6_mem);
+	kfree(fq);
+}
+
+static inline struct nf_ct_frag6_queue *frag_alloc_queue(void)
+{
+	struct nf_ct_frag6_queue *fq = kmalloc(sizeof(struct nf_ct_frag6_queue), GFP_ATOMIC);
+
+	if (!fq)
+		return NULL;
+	atomic_add(sizeof(struct nf_ct_frag6_queue), &nf_ct_frag6_mem);
+	return fq;
+}
+
+/* Destruction primitives. */
+
+/* Complete destruction of fq. */
+static void nf_ct_frag6_destroy(struct nf_ct_frag6_queue *fq)
+{
+	struct sk_buff *fp;
+
+	BUG_TRAP(fq->last_in&COMPLETE);
+	BUG_TRAP(del_timer(&fq->timer) == 0);
+
+	/* Release all fragment data. */
+	fp = fq->fragments;
+	while (fp) {
+		struct sk_buff *xp = fp->next;
+
+		frag_kfree_skb(fp);
+		fp = xp;
+	}
+
+	frag_free_queue(fq);
+}
+
+static __inline__ void fq_put(struct nf_ct_frag6_queue *fq)
+{
+	if (atomic_dec_and_test(&fq->refcnt))
+		nf_ct_frag6_destroy(fq);
+}
+
+/* Kill fq entry. It is not destroyed immediately,
+ * because caller (and someone more) holds reference count.
+ */
+static __inline__ void fq_kill(struct nf_ct_frag6_queue *fq)
+{
+	if (del_timer(&fq->timer))
+		atomic_dec(&fq->refcnt);
+
+	if (!(fq->last_in & COMPLETE)) {
+		fq_unlink(fq);
+		atomic_dec(&fq->refcnt);
+		fq->last_in |= COMPLETE;
+	}
+}
+
+static void nf_ct_frag6_evictor(void)
+{
+	struct nf_ct_frag6_queue *fq;
+	struct list_head *tmp;
+
+	for (;;) {
+		if (atomic_read(&nf_ct_frag6_mem) <= nf_ct_frag6_low_thresh)
+			return;
+		read_lock(&nf_ct_frag6_lock);
+		if (list_empty(&nf_ct_frag6_lru_list)) {
+			read_unlock(&nf_ct_frag6_lock);
+			return;
+		}
+		tmp = nf_ct_frag6_lru_list.next;
+		fq = list_entry(tmp, struct nf_ct_frag6_queue, lru_list);
+		atomic_inc(&fq->refcnt);
+		read_unlock(&nf_ct_frag6_lock);
+
+		spin_lock(&fq->lock);
+		if (!(fq->last_in&COMPLETE))
+			fq_kill(fq);
+		spin_unlock(&fq->lock);
+
+		fq_put(fq);
+	}
+}
+
+static void nf_ct_frag6_expire(unsigned long data)
+{
+	struct nf_ct_frag6_queue *fq = (struct nf_ct_frag6_queue *) data;
+
+	spin_lock(&fq->lock);
+
+	if (fq->last_in & COMPLETE)
+		goto out;
+
+	fq_kill(fq);
+
+out:
+	spin_unlock(&fq->lock);
+	fq_put(fq);
+}
+
+/* Creation primitives. */
+
+
+static struct nf_ct_frag6_queue *nf_ct_frag6_intern(unsigned int hash,
+					  struct nf_ct_frag6_queue *fq_in)
+{
+	struct nf_ct_frag6_queue *fq;
+
+	write_lock(&nf_ct_frag6_lock);
+#ifdef CONFIG_SMP
+	for (fq = nf_ct_frag6_hash[hash]; fq; fq = fq->next) {
+		if (fq->id == fq_in->id && 
+		    !ipv6_addr_cmp(&fq_in->saddr, &fq->saddr) &&
+		    !ipv6_addr_cmp(&fq_in->daddr, &fq->daddr)) {
+			atomic_inc(&fq->refcnt);
+			write_unlock(&nf_ct_frag6_lock);
+			fq_in->last_in |= COMPLETE;
+			fq_put(fq_in);
+			return fq;
+		}
+	}
+#endif
+	fq = fq_in;
+
+	if (!mod_timer(&fq->timer, jiffies + nf_ct_frag6_timeout))
+		atomic_inc(&fq->refcnt);
+
+	atomic_inc(&fq->refcnt);
+	if ((fq->next = nf_ct_frag6_hash[hash]) != NULL)
+		fq->next->pprev = &fq->next;
+	nf_ct_frag6_hash[hash] = fq;
+	fq->pprev = &nf_ct_frag6_hash[hash];
+	INIT_LIST_HEAD(&fq->lru_list);
+	list_add_tail(&fq->lru_list, &nf_ct_frag6_lru_list);
+	nf_ct_frag6_nqueues++;
+	write_unlock(&nf_ct_frag6_lock);
+	return fq;
+}
+
+
+static struct nf_ct_frag6_queue *
+nf_ct_frag6_create(unsigned int hash, u32 id, struct in6_addr *src,				   struct in6_addr *dst)
+{
+	struct nf_ct_frag6_queue *fq;
+
+	if ((fq = frag_alloc_queue()) == NULL) {
+		DEBUGP("Can't alloc new queue\n");
+		goto oom;
+	}
+
+	memset(fq, 0, sizeof(struct nf_ct_frag6_queue));
+
+	fq->id = id;
+	ipv6_addr_copy(&fq->saddr, src);
+	ipv6_addr_copy(&fq->daddr, dst);
+
+	init_timer(&fq->timer);
+	fq->timer.function = nf_ct_frag6_expire;
+	fq->timer.data = (long) fq;
+	fq->lock = SPIN_LOCK_UNLOCKED;
+	atomic_set(&fq->refcnt, 1);
+
+	return nf_ct_frag6_intern(hash, fq);
+
+oom:
+	return NULL;
+}
+
+static __inline__ struct nf_ct_frag6_queue *
+fq_find(u32 id, struct in6_addr *src, struct in6_addr *dst)
+{
+	struct nf_ct_frag6_queue *fq;
+	unsigned int hash = ip6qhashfn(id, src, dst);
+
+	read_lock(&nf_ct_frag6_lock);
+	for (fq = nf_ct_frag6_hash[hash]; fq; fq = fq->next) {
+		if (fq->id == id && 
+		    !ipv6_addr_cmp(src, &fq->saddr) &&
+		    !ipv6_addr_cmp(dst, &fq->daddr)) {
+			atomic_inc(&fq->refcnt);
+			read_unlock(&nf_ct_frag6_lock);
+			return fq;
+		}
+	}
+	read_unlock(&nf_ct_frag6_lock);
+
+	return nf_ct_frag6_create(hash, id, src, dst);
+}
+
+
+static int nf_ct_frag6_queue(struct nf_ct_frag6_queue *fq, struct sk_buff *skb, 
+			     struct frag_hdr *fhdr, int nhoff)
+{
+	struct sk_buff *prev, *next;
+	int offset, end;
+
+	if (fq->last_in & COMPLETE) {
+		DEBUGP("Allready completed\n");
+		goto err;
+	}
+
+	offset = ntohs(fhdr->frag_off) & ~0x7;
+	end = offset + (ntohs(skb->nh.ipv6h->payload_len) -
+			((u8 *) (fhdr + 1) - (u8 *) (skb->nh.ipv6h + 1)));
+
+	if ((unsigned int)end > IPV6_MAXPLEN) {
+		DEBUGP("offset is too large.\n");
+ 		return -1;
+	}
+
+ 	if (skb->ip_summed == CHECKSUM_HW)
+ 		skb->csum = csum_sub(skb->csum,
+ 				     csum_partial(skb->nh.raw,
+						  (u8*)(fhdr + 1) - skb->nh.raw,
+						  0));
+
+	/* Is this the final fragment? */
+	if (!(fhdr->frag_off & htons(IP6_MF))) {
+		/* If we already have some bits beyond end
+		 * or have different end, the segment is corrupted.
+		 */
+		if (end < fq->len ||
+		    ((fq->last_in & LAST_IN) && end != fq->len)) {
+			DEBUGP("already received last fragment\n");
+			goto err;
+		}
+		fq->last_in |= LAST_IN;
+		fq->len = end;
+	} else {
+		/* Check if the fragment is rounded to 8 bytes.
+		 * Required by the RFC.
+		 */
+		if (end & 0x7) {
+			/* RFC2460 says always send parameter problem in
+			 * this case. -DaveM
+			 */
+			DEBUGP("the end of this fragment is not rounded to 8 bytes.\n");
+			return -1;
+		}
+		if (end > fq->len) {
+			/* Some bits beyond end -> corruption. */
+			if (fq->last_in & LAST_IN) {
+				DEBUGP("last packet already reached.\n");
+				goto err;
+			}
+			fq->len = end;
+		}
+	}
+
+	if (end == offset)
+		goto err;
+
+	/* Point into the IP datagram 'data' part. */
+	if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data)) {
+		DEBUGP("queue: message is too short.\n");
+		goto err;
+	}
+	if (end-offset < skb->len) {
+		if (pskb_trim(skb, end - offset)) {
+			DEBUGP("Can't trim\n");
+			goto err;
+		}
+		if (skb->ip_summed != CHECKSUM_UNNECESSARY)
+			skb->ip_summed = CHECKSUM_NONE;
+	}
+
+	/* Find out which fragments are in front and at the back of us
+	 * in the chain of fragments so far.  We must know where to put
+	 * this fragment, right?
+	 */
+	prev = NULL;
+	for (next = fq->fragments; next != NULL; next = next->next) {
+		if (NFCT_FRAG6_CB(next)->offset >= offset)
+			break;	/* bingo! */
+		prev = next;
+	}
+
+	/* We found where to put this one.  Check for overlap with
+	 * preceding fragment, and, if needed, align things so that
+	 * any overlaps are eliminated.
+	 */
+	if (prev) {
+		int i = (NFCT_FRAG6_CB(prev)->offset + prev->len) - offset;
+
+		if (i > 0) {
+			offset += i;
+			if (end <= offset) {
+				DEBUGP("overlap\n");
+				goto err;
+			}
+			if (!pskb_pull(skb, i)) {
+				DEBUGP("Can't pull\n");
+				goto err;
+			}
+			if (skb->ip_summed != CHECKSUM_UNNECESSARY)
+				skb->ip_summed = CHECKSUM_NONE;
+		}
+	}
+
+	/* Look for overlap with succeeding segments.
+	 * If we can merge fragments, do it.
+	 */
+	while (next && NFCT_FRAG6_CB(next)->offset < end) {
+		/* overlap is 'i' bytes */
+		int i = end - NFCT_FRAG6_CB(next)->offset;
+
+		if (i < next->len) {
+			/* Eat head of the next overlapped fragment
+			 * and leave the loop. The next ones cannot overlap.
+			 */
+			DEBUGP("Eat head of the overlapped parts.: %d", i);
+			if (!pskb_pull(next, i))
+				goto err;
+
+			/* next fragment */
+			NFCT_FRAG6_CB(next)->offset += i;
+			fq->meat -= i;
+			if (next->ip_summed != CHECKSUM_UNNECESSARY)
+				next->ip_summed = CHECKSUM_NONE;
+			break;
+		} else {
+			struct sk_buff *free_it = next;
+
+			/* Old fragmnet is completely overridden with
+			 * new one drop it.
+			 */
+			next = next->next;
+
+			if (prev)
+				prev->next = next;
+			else
+				fq->fragments = next;
+
+			fq->meat -= free_it->len;
+			frag_kfree_skb(free_it);
+		}
+	}
+
+	NFCT_FRAG6_CB(skb)->offset = offset;
+
+	/* Insert this fragment in the chain of fragments. */
+	skb->next = next;
+	if (prev)
+		prev->next = skb;
+	else
+		fq->fragments = skb;
+
+	skb->dev = NULL;
+	skb_get_timestamp(skb, &fq->stamp);
+	fq->meat += skb->len;
+	atomic_add(skb->truesize, &nf_ct_frag6_mem);
+
+	/* The first fragment.
+	 * nhoffset is obtained from the first fragment, of course.
+	 */
+	if (offset == 0) {
+		fq->nhoffset = nhoff;
+		fq->last_in |= FIRST_IN;
+	}
+	write_lock(&nf_ct_frag6_lock);
+	list_move_tail(&fq->lru_list, &nf_ct_frag6_lru_list);
+	write_unlock(&nf_ct_frag6_lock);
+	return 0;
+
+err:
+	return -1;
+}
+
+/*
+ *	Check if this packet is complete.
+ *	Returns NULL on failure by any reason, and pointer
+ *	to current nexthdr field in reassembled frame.
+ *
+ *	It is called with locked fq, and caller must check that
+ *	queue is eligible for reassembly i.e. it is not COMPLETE,
+ *	the last and the first frames arrived and all the bits are here.
+ */
+static struct sk_buff *
+nf_ct_frag6_reasm(struct nf_ct_frag6_queue *fq, struct net_device *dev)
+{
+	struct sk_buff *fp, *op, *head = fq->fragments;
+	int    payload_len;
+
+	fq_kill(fq);
+
+	BUG_TRAP(head != NULL);
+	BUG_TRAP(NFCT_FRAG6_CB(head)->offset == 0);
+
+	/* Unfragmented part is taken from the first segment. */
+	payload_len = (head->data - head->nh.raw) - sizeof(struct ipv6hdr) + fq->len - sizeof(struct frag_hdr);
+	if (payload_len > IPV6_MAXPLEN) {
+		DEBUGP("payload len is too large.\n");
+		goto out_oversize;
+	}
+
+	/* Head of list must not be cloned. */
+	if (skb_cloned(head) && pskb_expand_head(head, 0, 0, GFP_ATOMIC)) {
+		DEBUGP("skb is cloned but can't expand head");
+		goto out_oom;
+	}
+
+	/* If the first fragment is fragmented itself, we split
+	 * it to two chunks: the first with data and paged part
+	 * and the second, holding only fragments. */
+	if (skb_shinfo(head)->frag_list) {
+		struct sk_buff *clone;
+		int i, plen = 0;
+
+		if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL) {
+			DEBUGP("Can't alloc skb\n");
+			goto out_oom;
+		}
+		clone->next = head->next;
+		head->next = clone;
+		skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
+		skb_shinfo(head)->frag_list = NULL;
+		for (i=0; i<skb_shinfo(head)->nr_frags; i++)
+			plen += skb_shinfo(head)->frags[i].size;
+		clone->len = clone->data_len = head->data_len - plen;
+		head->data_len -= clone->len;
+		head->len -= clone->len;
+		clone->csum = 0;
+		clone->ip_summed = head->ip_summed;
+
+		NFCT_FRAG6_CB(clone)->orig = NULL;
+		atomic_add(clone->truesize, &nf_ct_frag6_mem);
+	}
+
+	/* We have to remove fragment header from datagram and to relocate
+	 * header in order to calculate ICV correctly. */
+	head->nh.raw[fq->nhoffset] = head->h.raw[0];
+	memmove(head->head + sizeof(struct frag_hdr), head->head, 
+		(head->data - head->head) - sizeof(struct frag_hdr));
+	head->mac.raw += sizeof(struct frag_hdr);
+	head->nh.raw += sizeof(struct frag_hdr);
+
+	skb_shinfo(head)->frag_list = head->next;
+	head->h.raw = head->data;
+	skb_push(head, head->data - head->nh.raw);
+	atomic_sub(head->truesize, &nf_ct_frag6_mem);
+
+	for (fp=head->next; fp; fp = fp->next) {
+		head->data_len += fp->len;
+		head->len += fp->len;
+		if (head->ip_summed != fp->ip_summed)
+			head->ip_summed = CHECKSUM_NONE;
+		else if (head->ip_summed == CHECKSUM_HW)
+			head->csum = csum_add(head->csum, fp->csum);
+		head->truesize += fp->truesize;
+		atomic_sub(fp->truesize, &nf_ct_frag6_mem);
+	}
+
+	head->next = NULL;
+	head->dev = dev;
+	skb_set_timestamp(head, &fq->stamp);
+	head->nh.ipv6h->payload_len = htons(payload_len);
+
+	/* Yes, and fold redundant checksum back. 8) */
+	if (head->ip_summed == CHECKSUM_HW)
+		head->csum = csum_partial(head->nh.raw, head->h.raw-head->nh.raw, head->csum);
+
+	fq->fragments = NULL;
+
+	/* all original skbs are linked into the NFCT_FRAG6_CB(head).orig */
+	fp = skb_shinfo(head)->frag_list;
+	if (NFCT_FRAG6_CB(fp)->orig == NULL)
+		/* at above code, head skb is divided into two skbs. */
+		fp = fp->next;
+
+	op = NFCT_FRAG6_CB(head)->orig;
+	for (; fp; fp = fp->next) {
+		struct sk_buff *orig = NFCT_FRAG6_CB(fp)->orig;
+
+		op->next = orig;
+		op = orig;
+		NFCT_FRAG6_CB(fp)->orig = NULL;
+	}
+
+	return head;
+
+out_oversize:
+	if (net_ratelimit())
+		printk(KERN_DEBUG "nf_ct_frag6_reasm: payload len = %d\n", payload_len);
+	goto out_fail;
+out_oom:
+	if (net_ratelimit())
+		printk(KERN_DEBUG "nf_ct_frag6_reasm: no memory for reassembly\n");
+out_fail:
+	return NULL;
+}
+
+/*
+ * find the header just before Fragment Header.
+ *
+ * if success return 0 and set ...
+ * (*prevhdrp): the value of "Next Header Field" in the header
+ *		just before Fragment Header.
+ * (*prevhoff): the offset of "Next Header Field" in the header
+ *		just before Fragment Header.
+ * (*fhoff)   : the offset of Fragment Header.
+ *
+ * Based on ipv6_skip_hdr() in net/ipv6/exthdr.c
+ *
+ */
+static int
+find_prev_fhdr(struct sk_buff *skb, u8 *prevhdrp, int *prevhoff, int *fhoff)
+{
+        u8 nexthdr = skb->nh.ipv6h->nexthdr;
+	u8 prev_nhoff = (u8 *)&skb->nh.ipv6h->nexthdr - skb->data;
+	int start = (u8 *)(skb->nh.ipv6h+1) - skb->data;
+	int len = skb->len - start;
+	u8 prevhdr = NEXTHDR_IPV6;
+
+        while (nexthdr != NEXTHDR_FRAGMENT) {
+                struct ipv6_opt_hdr hdr;
+                int hdrlen;
+
+		if (!ipv6_ext_hdr(nexthdr)) {
+			return -1;
+		}
+                if (len < (int)sizeof(struct ipv6_opt_hdr)) {
+			DEBUGP("too short\n");
+			return -1;
+		}
+                if (nexthdr == NEXTHDR_NONE) {
+			DEBUGP("next header is none\n");
+			return -1;
+		}
+                if (skb_copy_bits(skb, start, &hdr, sizeof(hdr)))
+                        BUG();
+                if (nexthdr == NEXTHDR_AUTH)
+                        hdrlen = (hdr.hdrlen+2)<<2;
+                else
+                        hdrlen = ipv6_optlen(&hdr);
+
+		prevhdr = nexthdr;
+		prev_nhoff = start;
+
+                nexthdr = hdr.nexthdr;
+                len -= hdrlen;
+                start += hdrlen;
+        }
+
+	if (len < 0)
+		return -1;
+
+	*prevhdrp = prevhdr;
+	*prevhoff = prev_nhoff;
+	*fhoff = start;
+
+	return 0;
+}
+
+struct sk_buff *nf_ct_frag6_gather(struct sk_buff *skb)
+{
+	struct sk_buff *clone; 
+	struct net_device *dev = skb->dev;
+	struct frag_hdr *fhdr;
+	struct nf_ct_frag6_queue *fq;
+	struct ipv6hdr *hdr;
+	int fhoff, nhoff;
+	u8 prevhdr;
+	struct sk_buff *ret_skb = NULL;
+
+	/* Jumbo payload inhibits frag. header */
+	if (skb->nh.ipv6h->payload_len == 0) {
+		DEBUGP("payload len = 0\n");
+		return skb;
+	}
+
+	if (find_prev_fhdr(skb, &prevhdr, &nhoff, &fhoff) < 0)
+		return skb;
+
+	clone = skb_clone(skb, GFP_ATOMIC);
+	if (clone == NULL) {
+		DEBUGP("Can't clone skb\n");
+		return skb;
+	}
+
+	NFCT_FRAG6_CB(clone)->orig = skb;
+
+	if (!pskb_may_pull(clone, fhoff + sizeof(*fhdr))) {
+		DEBUGP("message is too short.\n");
+		goto ret_orig;
+	}
+
+	clone->h.raw = clone->data + fhoff;
+	hdr = clone->nh.ipv6h;
+	fhdr = (struct frag_hdr *)clone->h.raw;
+
+	if (!(fhdr->frag_off & htons(0xFFF9))) {
+		DEBUGP("Invalid fragment offset\n");
+		/* It is not a fragmented frame */
+		goto ret_orig;
+	}
+
+	if (atomic_read(&nf_ct_frag6_mem) > nf_ct_frag6_high_thresh)
+		nf_ct_frag6_evictor();
+
+	fq = fq_find(fhdr->identification, &hdr->saddr, &hdr->daddr);
+	if (fq == NULL) {
+		DEBUGP("Can't find and can't create new queue\n");
+		goto ret_orig;
+	}
+
+	spin_lock(&fq->lock);
+
+	if (nf_ct_frag6_queue(fq, clone, fhdr, nhoff) < 0) {
+		spin_unlock(&fq->lock);
+		DEBUGP("Can't insert skb to queue\n");
+		fq_put(fq);
+		goto ret_orig;
+	}
+
+	if (fq->last_in == (FIRST_IN|LAST_IN) && fq->meat == fq->len) {
+		ret_skb = nf_ct_frag6_reasm(fq, dev);
+		if (ret_skb == NULL)
+			DEBUGP("Can't reassemble fragmented packets\n");
+	}
+	spin_unlock(&fq->lock);
+
+	fq_put(fq);
+	return ret_skb;
+
+ret_orig:
+	kfree_skb(clone);
+	return skb;
+}
+
+void nf_ct_frag6_output(unsigned int hooknum, struct sk_buff *skb,
+			struct net_device *in, struct net_device *out,
+			int (*okfn)(struct sk_buff *))
+{
+	struct sk_buff *s, *s2;
+
+	for (s = NFCT_FRAG6_CB(skb)->orig; s;) {
+		nf_conntrack_put_reasm(s->nfct_reasm);
+		nf_conntrack_get_reasm(skb);
+		s->nfct_reasm = skb;
+
+		s2 = s->next;
+		NF_HOOK_THRESH(PF_INET6, hooknum, s, in, out, okfn,
+			       NF_IP6_PRI_CONNTRACK_DEFRAG + 1);
+		s = s2;
+	}
+	nf_conntrack_put_reasm(skb);
+}
+
+int nf_ct_frag6_kfree_frags(struct sk_buff *skb)
+{
+	struct sk_buff *s, *s2;
+
+	for (s = NFCT_FRAG6_CB(skb)->orig; s; s = s2) {
+
+		s2 = s->next;
+		kfree_skb(s);
+	}
+
+	kfree_skb(skb);
+
+	return 0;
+}
+
+int nf_ct_frag6_init(void)
+{
+	nf_ct_frag6_hash_rnd = (u32) ((num_physpages ^ (num_physpages>>7)) ^
+				   (jiffies ^ (jiffies >> 6)));
+
+	init_timer(&nf_ct_frag6_secret_timer);
+	nf_ct_frag6_secret_timer.function = nf_ct_frag6_secret_rebuild;
+	nf_ct_frag6_secret_timer.expires = jiffies
+					   + nf_ct_frag6_secret_interval;
+	add_timer(&nf_ct_frag6_secret_timer);
+
+	return 0;
+}
+
+void nf_ct_frag6_cleanup(void)
+{
+	del_timer(&nf_ct_frag6_secret_timer);
+	nf_ct_frag6_evictor();
+}