/*
   *	IPv6 fragment reassembly

   *	Linux INET6 implementation

   *
   *	Authors:

   *	Pedro Roque		<roque@di.fc.ul.pt>

   *

   *	Based on: net/ipv4/ip_fragment.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.
   */

  /*
   *	Fixes:

   *	Andi Kleen	Make it work with multiple hosts.
   *			More RFC compliance.
   *
   *      Horst von Brand Add missing #include <linux/string.h>
   *	Alexey Kuznetsov	SMP races, threading, cleanup.
   *	Patrick McHardy		LRU queue of frag heads for evictor.
   *	Mitsuru KANDA @USAGI	Register inet6_protocol{}.
   *	David Stevens and
   *	YOSHIFUJI,H. @USAGI	Always remove fragment header to
   *				calculate ICV correctly.
   */

  
  #define pr_fmt(fmt) "IPv6: " fmt

  #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 <linux/skbuff.h>

  #include <linux/slab.h>

  #include <linux/export.h>

  
  #include <net/sock.h>
  #include <net/snmp.h>
  
  #include <net/ipv6.h>

  #include <net/ip6_route.h>

  #include <net/protocol.h>
  #include <net/transp_v6.h>
  #include <net/rawv6.h>
  #include <net/ndisc.h>
  #include <net/addrconf.h>

  #include <net/inet_frag.h>

  #include <net/inet_ecn.h>

  static const char ip6_frag_cache_name[] = "ip6-frags";

  struct ip6frag_skb_cb {

  	struct inet6_skb_parm	h;
  	int			offset;
  };

  #define FRAG6_CB(skb)	((struct ip6frag_skb_cb *)((skb)->cb))

  static u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h)

  {
  	return 1 << (ipv6_get_dsfield(ipv6h) & INET_ECN_MASK);
  }

  static struct inet_frags ip6_frags;

  static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *prev,
  			  struct net_device *dev);

  /*
   * callers should be careful not to use the hash value outside the ipfrag_lock
   * as doing so could race with ipfrag_hash_rnd being recalculated.
   */

  static unsigned int inet6_hash_frag(__be32 id, const struct in6_addr *saddr,
  				    const struct in6_addr *daddr)

  {

  	net_get_random_once(&ip6_frags.rnd, sizeof(ip6_frags.rnd));

  	return jhash_3words(ipv6_addr_hash(saddr), ipv6_addr_hash(daddr),
  			    (__force u32)id, ip6_frags.rnd);

  }

  static unsigned int ip6_hashfn(const struct inet_frag_queue *q)

  {

  	const struct frag_queue *fq;

  	fq = container_of(q, struct frag_queue, q);

  	return inet6_hash_frag(fq->id, &fq->saddr, &fq->daddr);

  }

  bool ip6_frag_match(const struct inet_frag_queue *q, const void *a)

  {

  	const struct frag_queue *fq;
  	const struct ip6_create_arg *arg = a;

  
  	fq = container_of(q, struct frag_queue, q);

  	return	fq->id == arg->id &&
  		fq->user == arg->user &&
  		ipv6_addr_equal(&fq->saddr, arg->src) &&

  		ipv6_addr_equal(&fq->daddr, arg->dst) &&
  		(arg->iif == fq->iif ||
  		 !(ipv6_addr_type(arg->dst) & (IPV6_ADDR_MULTICAST |
  					       IPV6_ADDR_LINKLOCAL)));

  }
  EXPORT_SYMBOL(ip6_frag_match);

  void ip6_frag_init(struct inet_frag_queue *q, const void *a)

  {

  	struct frag_queue *fq = container_of(q, struct frag_queue, q);

  	const struct ip6_create_arg *arg = a;

  
  	fq->id = arg->id;

  	fq->user = arg->user;

  	fq->saddr = *arg->src;
  	fq->daddr = *arg->dst;

  	fq->ecn = arg->ecn;

  }

  EXPORT_SYMBOL(ip6_frag_init);

  void ip6_expire_frag_queue(struct net *net, struct frag_queue *fq,
  			   struct inet_frags *frags)

  {

  	struct net_device *dev = NULL;

  	spin_lock(&fq->q.lock);

  	if (fq->q.flags & INET_FRAG_COMPLETE)

  		goto out;

  	inet_frag_kill(&fq->q, frags);

  	rcu_read_lock();
  	dev = dev_get_by_index_rcu(net, fq->iif);

  	if (!dev)

  		goto out_rcu_unlock;

  	IP6_INC_STATS_BH(net, __in6_dev_get(dev), IPSTATS_MIB_REASMFAILS);

  	if (inet_frag_evicting(&fq->q))

  		goto out_rcu_unlock;
  
  	IP6_INC_STATS_BH(net, __in6_dev_get(dev), IPSTATS_MIB_REASMTIMEOUT);

  	/* Don't send error if the first segment did not arrive. */

  	if (!(fq->q.flags & INET_FRAG_FIRST_IN) || !fq->q.fragments)

  		goto out_rcu_unlock;

  	/* But use as source device on which LAST ARRIVED
  	 * segment was received. And do not use fq->dev
  	 * pointer directly, device might already disappeared.

  	 */

  	fq->q.fragments->dev = dev;

  	icmpv6_send(fq->q.fragments, ICMPV6_TIME_EXCEED, ICMPV6_EXC_FRAGTIME, 0);

  out_rcu_unlock:
  	rcu_read_unlock();

  out:

  	spin_unlock(&fq->q.lock);

  	inet_frag_put(&fq->q, frags);
  }
  EXPORT_SYMBOL(ip6_expire_frag_queue);
  
  static void ip6_frag_expire(unsigned long data)
  {
  	struct frag_queue *fq;
  	struct net *net;
  
  	fq = container_of((struct inet_frag_queue *)data, struct frag_queue, q);
  	net = container_of(fq->q.net, struct net, ipv6.frags);
  
  	ip6_expire_frag_queue(net, fq, &ip6_frags);

  }

  static struct frag_queue *

  fq_find(struct net *net, __be32 id, const struct in6_addr *src,

  	const struct in6_addr *dst, int iif, u8 ecn)

  {

  	struct inet_frag_queue *q;
  	struct ip6_create_arg arg;

  	unsigned int hash;

  	arg.id = id;

  	arg.user = IP6_DEFRAG_LOCAL_DELIVER;

  	arg.src = src;
  	arg.dst = dst;

  	arg.iif = iif;

  	arg.ecn = ecn;

  	hash = inet6_hash_frag(id, src, dst);

  	q = inet_frag_find(&net->ipv6.frags, &ip6_frags, &arg, hash);

  	if (IS_ERR_OR_NULL(q)) {
  		inet_frag_maybe_warn_overflow(q, pr_fmt());

  		return NULL;

  	}

  	return container_of(q, struct frag_queue, q);

  }

  static int ip6_frag_queue(struct frag_queue *fq, struct sk_buff *skb,

  			   struct frag_hdr *fhdr, int nhoff)
  {
  	struct sk_buff *prev, *next;

  	struct net_device *dev;

  	int offset, end;

  	struct net *net = dev_net(skb_dst(skb)->dev);

  	u8 ecn;

  	if (fq->q.flags & INET_FRAG_COMPLETE)

  		goto err;
  
  	offset = ntohs(fhdr->frag_off) & ~0x7;

  	end = offset + (ntohs(ipv6_hdr(skb)->payload_len) -
  			((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1)));

  
  	if ((unsigned int)end > IPV6_MAXPLEN) {

  		IP6_INC_STATS_BH(net, ip6_dst_idev(skb_dst(skb)),

  				 IPSTATS_MIB_INHDRERRORS);

  		icmpv6_param_prob(skb, ICMPV6_HDR_FIELD,
  				  ((u8 *)&fhdr->frag_off -
  				   skb_network_header(skb)));

  		return -1;

  	}

  	ecn = ip6_frag_ecn(ipv6_hdr(skb));

  	if (skb->ip_summed == CHECKSUM_COMPLETE) {
  		const unsigned char *nh = skb_network_header(skb);

  		skb->csum = csum_sub(skb->csum,

  				     csum_partial(nh, (u8 *)(fhdr + 1) - nh,
  						  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->q.len ||

  		    ((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len))

  			goto err;

  		fq->q.flags |= INET_FRAG_LAST_IN;

  		fq->q.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
  			 */

  			IP6_INC_STATS_BH(net, ip6_dst_idev(skb_dst(skb)),

  					 IPSTATS_MIB_INHDRERRORS);

  			icmpv6_param_prob(skb, ICMPV6_HDR_FIELD,

  					  offsetof(struct ipv6hdr, payload_len));

  			return -1;

  		}

  		if (end > fq->q.len) {

  			/* Some bits beyond end -> corruption. */

  			if (fq->q.flags & INET_FRAG_LAST_IN)

  				goto err;

  			fq->q.len = end;

  		}
  	}
  
  	if (end == offset)
  		goto err;
  
  	/* Point into the IP datagram 'data' part. */
  	if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data))
  		goto err;

  	if (pskb_trim_rcsum(skb, end - offset))
  		goto err;

  
  	/* 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 = fq->q.fragments_tail;
  	if (!prev || FRAG6_CB(prev)->offset < offset) {
  		next = NULL;
  		goto found;
  	}

  	prev = NULL;

  	for (next = fq->q.fragments; next != NULL; next = next->next) {

  		if (FRAG6_CB(next)->offset >= offset)
  			break;	/* bingo! */
  		prev = next;
  	}

  found:

  	/* RFC5722, Section 4, amended by Errata ID : 3089
  	 *                          When reassembling an IPv6 datagram, if

  	 *   one or more its constituent fragments is determined to be an
  	 *   overlapping fragment, the entire datagram (and any constituent

  	 *   fragments) MUST be silently discarded.

  	 */

  	/* Check for overlap with preceding fragment. */
  	if (prev &&

  	    (FRAG6_CB(prev)->offset + prev->len) > offset)

  		goto discard_fq;

  	/* Look for overlap with succeeding segment. */
  	if (next && FRAG6_CB(next)->offset < end)
  		goto discard_fq;

  
  	FRAG6_CB(skb)->offset = offset;
  
  	/* Insert this fragment in the chain of fragments. */
  	skb->next = next;

  	if (!next)
  		fq->q.fragments_tail = skb;

  	if (prev)
  		prev->next = skb;
  	else

  		fq->q.fragments = skb;

  	dev = skb->dev;
  	if (dev) {
  		fq->iif = dev->ifindex;
  		skb->dev = NULL;
  	}

  	fq->q.stamp = skb->tstamp;
  	fq->q.meat += skb->len;

  	fq->ecn |= ecn;

  	add_frag_mem_limit(fq->q.net, skb->truesize);

  
  	/* The first fragment.
  	 * nhoffset is obtained from the first fragment, of course.
  	 */
  	if (offset == 0) {
  		fq->nhoffset = nhoff;

  		fq->q.flags |= INET_FRAG_FIRST_IN;

  	}

  	if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&

  	    fq->q.meat == fq->q.len) {
  		int res;
  		unsigned long orefdst = skb->_skb_refdst;
  
  		skb->_skb_refdst = 0UL;
  		res = ip6_frag_reasm(fq, prev, dev);
  		skb->_skb_refdst = orefdst;
  		return res;
  	}

  	skb_dst_drop(skb);

  	return -1;

  discard_fq:

  	inet_frag_kill(&fq->q, &ip6_frags);

  err:

  	IP6_INC_STATS_BH(net, ip6_dst_idev(skb_dst(skb)),
  			 IPSTATS_MIB_REASMFAILS);

  	kfree_skb(skb);

  	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 int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *prev,

  			  struct net_device *dev)
  {

  	struct net *net = container_of(fq->q.net, struct net, ipv6.frags);

  	struct sk_buff *fp, *head = fq->q.fragments;

  	int    payload_len;
  	unsigned int nhoff;

  	int sum_truesize;

  	u8 ecn;

  	inet_frag_kill(&fq->q, &ip6_frags);

  	ecn = ip_frag_ecn_table[fq->ecn];
  	if (unlikely(ecn == 0xff))
  		goto out_fail;

  	/* Make the one we just received the head. */
  	if (prev) {
  		head = prev->next;
  		fp = skb_clone(head, GFP_ATOMIC);
  
  		if (!fp)
  			goto out_oom;
  
  		fp->next = head->next;

  		if (!fp->next)
  			fq->q.fragments_tail = fp;

  		prev->next = fp;

  		skb_morph(head, fq->q.fragments);
  		head->next = fq->q.fragments->next;

  		consume_skb(fq->q.fragments);

  		fq->q.fragments = head;

  	}

  	WARN_ON(head == NULL);
  	WARN_ON(FRAG6_CB(head)->offset != 0);

  
  	/* Unfragmented part is taken from the first segment. */

  	payload_len = ((head->data - skb_network_header(head)) -

  		       sizeof(struct ipv6hdr) + fq->q.len -

  		       sizeof(struct frag_hdr));

  	if (payload_len > IPV6_MAXPLEN)
  		goto out_oversize;
  
  	/* Head of list must not be cloned. */

  	if (skb_unclone(head, GFP_ATOMIC))

  		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_has_frag_list(head)) {

  		struct sk_buff *clone;
  		int i, plen = 0;

  		clone = alloc_skb(0, GFP_ATOMIC);

  		if (!clone)

  			goto out_oom;
  		clone->next = head->next;
  		head->next = clone;
  		skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;

  		skb_frag_list_init(head);

  		for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
  			plen += skb_frag_size(&skb_shinfo(head)->frags[i]);

  		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;

  		add_frag_mem_limit(fq->q.net, clone->truesize);

  	}
  
  	/* We have to remove fragment header from datagram and to relocate
  	 * header in order to calculate ICV correctly. */
  	nhoff = fq->nhoffset;

  	skb_network_header(head)[nhoff] = skb_transport_header(head)[0];

  	memmove(head->head + sizeof(struct frag_hdr), head->head,

  		(head->data - head->head) - sizeof(struct frag_hdr));

  	head->mac_header += sizeof(struct frag_hdr);
  	head->network_header += sizeof(struct frag_hdr);

  	skb_reset_transport_header(head);

  	skb_push(head, head->data - skb_network_header(head));

  	sum_truesize = head->truesize;
  	for (fp = head->next; fp;) {
  		bool headstolen;
  		int delta;
  		struct sk_buff *next = fp->next;
  
  		sum_truesize += fp->truesize;

  		if (head->ip_summed != fp->ip_summed)
  			head->ip_summed = CHECKSUM_NONE;

  		else if (head->ip_summed == CHECKSUM_COMPLETE)

  			head->csum = csum_add(head->csum, fp->csum);

  
  		if (skb_try_coalesce(head, fp, &headstolen, &delta)) {
  			kfree_skb_partial(fp, headstolen);
  		} else {
  			if (!skb_shinfo(head)->frag_list)
  				skb_shinfo(head)->frag_list = fp;
  			head->data_len += fp->len;
  			head->len += fp->len;
  			head->truesize += fp->truesize;
  		}
  		fp = next;

  	}

  	sub_frag_mem_limit(fq->q.net, sum_truesize);

  
  	head->next = NULL;
  	head->dev = dev;

  	head->tstamp = fq->q.stamp;

  	ipv6_hdr(head)->payload_len = htons(payload_len);

  	ipv6_change_dsfield(ipv6_hdr(head), 0xff, ecn);

  	IP6CB(head)->nhoff = nhoff;

  	IP6CB(head)->flags |= IP6SKB_FRAGMENTED;

  	/* Yes, and fold redundant checksum back. 8) */

  	skb_postpush_rcsum(head, skb_network_header(head),
  			   skb_network_header_len(head));

  	rcu_read_lock();

  	IP6_INC_STATS_BH(net, __in6_dev_get(dev), IPSTATS_MIB_REASMOKS);

  	rcu_read_unlock();

  	fq->q.fragments = NULL;

  	fq->q.fragments_tail = NULL;

  	return 1;
  
  out_oversize:

  	net_dbg_ratelimited("ip6_frag_reasm: payload len = %d
  ", payload_len);

  	goto out_fail;
  out_oom:

  	net_dbg_ratelimited("ip6_frag_reasm: no memory for reassembly
  ");

  out_fail:

  	rcu_read_lock();

  	IP6_INC_STATS_BH(net, __in6_dev_get(dev), IPSTATS_MIB_REASMFAILS);

  	rcu_read_unlock();

  	return -1;
  }

  static int ipv6_frag_rcv(struct sk_buff *skb)

  {

  	struct frag_hdr *fhdr;
  	struct frag_queue *fq;

  	const struct ipv6hdr *hdr = ipv6_hdr(skb);

  	struct net *net = dev_net(skb_dst(skb)->dev);

  	if (IP6CB(skb)->flags & IP6SKB_FRAGMENTED)
  		goto fail_hdr;

  	IP6_INC_STATS_BH(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMREQDS);

  
  	/* Jumbo payload inhibits frag. header */

  	if (hdr->payload_len == 0)

  		goto fail_hdr;

  	if (!pskb_may_pull(skb, (skb_transport_offset(skb) +

  				 sizeof(struct frag_hdr))))
  		goto fail_hdr;

  	hdr = ipv6_hdr(skb);

  	fhdr = (struct frag_hdr *)skb_transport_header(skb);

  
  	if (!(fhdr->frag_off & htons(0xFFF9))) {
  		/* It is not a fragmented frame */

  		skb->transport_header += sizeof(struct frag_hdr);

  		IP6_INC_STATS_BH(net,

  				 ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMOKS);

  		IP6CB(skb)->nhoff = (u8 *)fhdr - skb_network_header(skb);

  		IP6CB(skb)->flags |= IP6SKB_FRAGMENTED;

  		return 1;
  	}

  	fq = fq_find(net, fhdr->identification, &hdr->saddr, &hdr->daddr,

  		     skb->dev ? skb->dev->ifindex : 0, ip6_frag_ecn(hdr));

  	if (fq) {

  		int ret;

  		spin_lock(&fq->q.lock);

  		ret = ip6_frag_queue(fq, skb, fhdr, IP6CB(skb)->nhoff);

  		spin_unlock(&fq->q.lock);

  		inet_frag_put(&fq->q, &ip6_frags);

  		return ret;
  	}

  	IP6_INC_STATS_BH(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMFAILS);

  	kfree_skb(skb);
  	return -1;

  
  fail_hdr:

  	IP6_INC_STATS_BH(net, ip6_dst_idev(skb_dst(skb)),
  			 IPSTATS_MIB_INHDRERRORS);

  	icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, skb_network_header_len(skb));
  	return -1;

  }

  static const struct inet6_protocol frag_protocol = {

  	.handler	=	ipv6_frag_rcv,
  	.flags		=	INET6_PROTO_NOPOLICY,
  };

  #ifdef CONFIG_SYSCTL

  static int zero;

  static struct ctl_table ip6_frags_ns_ctl_table[] = {

  	{

  		.procname	= "ip6frag_high_thresh",

  		.data		= &init_net.ipv6.frags.high_thresh,

  		.maxlen		= sizeof(int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_minmax,
  		.extra1		= &init_net.ipv6.frags.low_thresh

  	},
  	{

  		.procname	= "ip6frag_low_thresh",

  		.data		= &init_net.ipv6.frags.low_thresh,

  		.maxlen		= sizeof(int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_minmax,
  		.extra1		= &zero,
  		.extra2		= &init_net.ipv6.frags.high_thresh

  	},
  	{

  		.procname	= "ip6frag_time",

  		.data		= &init_net.ipv6.frags.timeout,

  		.maxlen		= sizeof(int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},

  	{ }
  };

  /* secret interval has been deprecated */
  static int ip6_frags_secret_interval_unused;

  static struct ctl_table ip6_frags_ctl_table[] = {

  	{

  		.procname	= "ip6frag_secret_interval",

  		.data		= &ip6_frags_secret_interval_unused,

  		.maxlen		= sizeof(int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},
  	{ }
  };

  static int __net_init ip6_frags_ns_sysctl_register(struct net *net)

  {

  	struct ctl_table *table;

  	struct ctl_table_header *hdr;

  	table = ip6_frags_ns_ctl_table;

  	if (!net_eq(net, &init_net)) {

  		table = kmemdup(table, sizeof(ip6_frags_ns_ctl_table), GFP_KERNEL);

  		if (!table)

  			goto err_alloc;

  		table[0].data = &net->ipv6.frags.high_thresh;

  		table[0].extra1 = &net->ipv6.frags.low_thresh;
  		table[0].extra2 = &init_net.ipv6.frags.high_thresh;

  		table[1].data = &net->ipv6.frags.low_thresh;

  		table[1].extra2 = &net->ipv6.frags.high_thresh;

  		table[2].data = &net->ipv6.frags.timeout;

  
  		/* Don't export sysctls to unprivileged users */
  		if (net->user_ns != &init_user_ns)
  			table[0].procname = NULL;

  	}

  	hdr = register_net_sysctl(net, "net/ipv6", table);

  	if (!hdr)

  		goto err_reg;
  
  	net->ipv6.sysctl.frags_hdr = hdr;
  	return 0;
  
  err_reg:

  	if (!net_eq(net, &init_net))

  		kfree(table);
  err_alloc:
  	return -ENOMEM;
  }

  static void __net_exit ip6_frags_ns_sysctl_unregister(struct net *net)

  {
  	struct ctl_table *table;
  
  	table = net->ipv6.sysctl.frags_hdr->ctl_table_arg;
  	unregister_net_sysctl_table(net->ipv6.sysctl.frags_hdr);

  	if (!net_eq(net, &init_net))
  		kfree(table);

  }

  
  static struct ctl_table_header *ip6_ctl_header;
  
  static int ip6_frags_sysctl_register(void)
  {

  	ip6_ctl_header = register_net_sysctl(&init_net, "net/ipv6",

  			ip6_frags_ctl_table);
  	return ip6_ctl_header == NULL ? -ENOMEM : 0;
  }
  
  static void ip6_frags_sysctl_unregister(void)
  {
  	unregister_net_sysctl_table(ip6_ctl_header);
  }

  #else

  static int ip6_frags_ns_sysctl_register(struct net *net)

  {

  	return 0;
  }

  static void ip6_frags_ns_sysctl_unregister(struct net *net)

  {
  }

  static int ip6_frags_sysctl_register(void)

  {
  	return 0;
  }

  static void ip6_frags_sysctl_unregister(void)

  {
  }

  #endif

  static int __net_init ipv6_frags_init_net(struct net *net)

  {

  	int res;

  	net->ipv6.frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
  	net->ipv6.frags.low_thresh = IPV6_FRAG_LOW_THRESH;

  	net->ipv6.frags.timeout = IPV6_FRAG_TIMEOUT;

  	res = inet_frags_init_net(&net->ipv6.frags);
  	if (res)
  		return res;
  	res = ip6_frags_ns_sysctl_register(net);
  	if (res)
  		inet_frags_uninit_net(&net->ipv6.frags);
  	return res;

  }

  static void __net_exit ipv6_frags_exit_net(struct net *net)

  {

  	ip6_frags_ns_sysctl_unregister(net);

  	inet_frags_exit_net(&net->ipv6.frags, &ip6_frags);
  }
  
  static struct pernet_operations ip6_frags_ops = {
  	.init = ipv6_frags_init_net,
  	.exit = ipv6_frags_exit_net,
  };

  int __init ipv6_frag_init(void)

  {

  	int ret;

  	ret = inet6_add_protocol(&frag_protocol, IPPROTO_FRAGMENT);
  	if (ret)
  		goto out;

  	ret = ip6_frags_sysctl_register();
  	if (ret)
  		goto err_sysctl;

  	ret = register_pernet_subsys(&ip6_frags_ops);
  	if (ret)
  		goto err_pernet;

  	ip6_frags.hashfn = ip6_hashfn;

  	ip6_frags.constructor = ip6_frag_init;

  	ip6_frags.destructor = NULL;

  	ip6_frags.qsize = sizeof(struct frag_queue);

  	ip6_frags.match = ip6_frag_match;

  	ip6_frags.frag_expire = ip6_frag_expire;

  	ip6_frags.frags_cache_name = ip6_frag_cache_name;
  	ret = inet_frags_init(&ip6_frags);
  	if (ret)
  		goto err_pernet;

  out:
  	return ret;

  
  err_pernet:

  	ip6_frags_sysctl_unregister();
  err_sysctl:

  	inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT);
  	goto out;

  }
  
  void ipv6_frag_exit(void)
  {
  	inet_frags_fini(&ip6_frags);

  	ip6_frags_sysctl_unregister();

  	unregister_pernet_subsys(&ip6_frags_ops);

  	inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT);

  }