net/ipv6/reassembly.c - kernel/common - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *	IPv6 fragment reassembly
  *	Linux INET6 implementation
  *
  *	Authors:
  *	Pedro Roque		<[email protected]>
  *
  *	Based on: net/ipv4/ip_fragment.c
  */

 /*
  *	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/ipv6_frag.h>
 #include <net/inet_ecn.h>

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

 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 *skb,
 			  struct sk_buff *prev_tail, struct net_device *dev);

 static void ip6_frag_expire(struct timer_list *t)
 {
 	struct inet_frag_queue *frag = from_timer(frag, t, timer);
 	struct frag_queue *fq;

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

 	ip6frag_expire_frag_queue(fq->q.fqdir->net, fq);
 }

 static struct frag_queue *
 fq_find(struct net *net, __be32 id, const struct ipv6hdr *hdr, int iif)
 {
 	struct frag_v6_compare_key key = {
 		.id = id,
 		.saddr = hdr->saddr,
 		.daddr = hdr->daddr,
 		.user = IP6_DEFRAG_LOCAL_DELIVER,
 		.iif = iif,
 	};
 	struct inet_frag_queue *q;

 	if (!(ipv6_addr_type(&hdr->daddr) & (IPV6_ADDR_MULTICAST |
 					    IPV6_ADDR_LINKLOCAL)))
 		key.iif = 0;

 	q = inet_frag_find(net->ipv6.fqdir, &key);
 	if (!q)
 		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,
 			  u32 *prob_offset)
 {
 	struct net *net = dev_net(skb_dst(skb)->dev);
 	int offset, end, fragsize;
 	struct sk_buff *prev_tail;
 	struct net_device *dev;
 	int err = -ENOENT;
 	u8 ecn;

 	if (fq->q.flags & INET_FRAG_COMPLETE)
 		goto err;

 	err = -EINVAL;
 	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) {
 		*prob_offset = (u8 *)&fhdr->frag_off - skb_network_header(skb);
 		/* note that if prob_offset is set, the skb is freed elsewhere,
 		 * we do not free it here.
 		 */
 		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 discard_fq;
 		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
 			 */
 			*prob_offset = 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 discard_fq;
 			fq->q.len = end;
 		}
 	}

 	if (end == offset)
 		goto discard_fq;

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

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

 	/* Note : skb->rbnode and skb->dev share the same location. */
 	dev = skb->dev;
 	/* Makes sure compiler wont do silly aliasing games */
 	barrier();

 	prev_tail = fq->q.fragments_tail;
 	err = inet_frag_queue_insert(&fq->q, skb, offset, end);
 	if (err)
 		goto insert_error;

 	if (dev)
 		fq->iif = dev->ifindex;

 	fq->q.stamp = skb->tstamp;
 	fq->q.meat += skb->len;
 	fq->ecn |= ecn;
 	add_frag_mem_limit(fq->q.fqdir, skb->truesize);

 	fragsize = -skb_network_offset(skb) + skb->len;
 	if (fragsize > fq->q.max_size)
 		fq->q.max_size = fragsize;

 	/* 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) {
 		unsigned long orefdst = skb->_skb_refdst;

 		skb->_skb_refdst = 0UL;
 		err = ip6_frag_reasm(fq, skb, prev_tail, dev);
 		skb->_skb_refdst = orefdst;
 		return err;
 	}

 	skb_dst_drop(skb);
 	return -EINPROGRESS;

 insert_error:
 	if (err == IPFRAG_DUP) {
 		kfree_skb(skb);
 		return -EINVAL;
 	}
 	err = -EINVAL;
 	__IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
 			IPSTATS_MIB_REASM_OVERLAPS);
 discard_fq:
 	inet_frag_kill(&fq->q);
 	__IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
 			IPSTATS_MIB_REASMFAILS);
 err:
 	kfree_skb(skb);
 	return err;
 }

 /*
  *	Check if this packet is complete.
  *
  *	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 *skb,
 			  struct sk_buff *prev_tail, struct net_device *dev)
 {
 	struct net *net = fq->q.fqdir->net;
 	unsigned int nhoff;
 	void *reasm_data;
 	int payload_len;
 	u8 ecn;

 	inet_frag_kill(&fq->q);

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

 	reasm_data = inet_frag_reasm_prepare(&fq->q, skb, prev_tail);
 	if (!reasm_data)
 		goto out_oom;

 	payload_len = ((skb->data - skb_network_header(skb)) -
 		       sizeof(struct ipv6hdr) + fq->q.len -
 		       sizeof(struct frag_hdr));
 	if (payload_len > IPV6_MAXPLEN)
 		goto out_oversize;

 	/* We have to remove fragment header from datagram and to relocate
 	 * header in order to calculate ICV correctly. */
 	nhoff = fq->nhoffset;
 	skb_network_header(skb)[nhoff] = skb_transport_header(skb)[0];
 	memmove(skb->head + sizeof(struct frag_hdr), skb->head,
 		(skb->data - skb->head) - sizeof(struct frag_hdr));
 	if (skb_mac_header_was_set(skb))
 		skb->mac_header += sizeof(struct frag_hdr);
 	skb->network_header += sizeof(struct frag_hdr);

 	skb_reset_transport_header(skb);

 	inet_frag_reasm_finish(&fq->q, skb, reasm_data);

 	skb->dev = dev;
 	ipv6_hdr(skb)->payload_len = htons(payload_len);
 	ipv6_change_dsfield(ipv6_hdr(skb), 0xff, ecn);
 	IP6CB(skb)->nhoff = nhoff;
 	IP6CB(skb)->flags |= IP6SKB_FRAGMENTED;
 	IP6CB(skb)->frag_max_size = fq->q.max_size;

 	/* Yes, and fold redundant checksum back. 8) */
 	skb_postpush_rcsum(skb, skb_network_header(skb),
 			   skb_network_header_len(skb));

 	rcu_read_lock();
 	__IP6_INC_STATS(net, __in6_dev_stats_get(dev, skb), IPSTATS_MIB_REASMOKS);
 	rcu_read_unlock();
 	fq->q.rb_fragments = RB_ROOT;
 	fq->q.fragments_tail = NULL;
 	fq->q.last_run_head = NULL;
 	return 1;

 out_oversize:
 	net_dbg_ratelimited("ip6_frag_reasm: payload len = %d\n", payload_len);
 	goto out_fail;
 out_oom:
 	net_dbg_ratelimited("ip6_frag_reasm: no memory for reassembly\n");
 out_fail:
 	rcu_read_lock();
 	__IP6_INC_STATS(net, __in6_dev_stats_get(dev, skb), IPSTATS_MIB_REASMFAILS);
 	rcu_read_unlock();
 	inet_frag_kill(&fq->q);
 	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);
 	int iif;

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

 	__IP6_INC_STATS(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(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;
 	}

 	iif = skb->dev ? skb->dev->ifindex : 0;
 	fq = fq_find(net, fhdr->identification, hdr, iif);
 	if (fq) {
 		u32 prob_offset = 0;
 		int ret;

 		spin_lock(&fq->q.lock);

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

 		spin_unlock(&fq->q.lock);
 		inet_frag_put(&fq->q);
 		if (prob_offset) {
 			__IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),
 					IPSTATS_MIB_INHDRERRORS);
 			/* icmpv6_param_prob() calls kfree_skb(skb) */
 			icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, prob_offset);
 		}
 		return ret;
 	}

 	__IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMFAILS);
 	kfree_skb(skb);
 	return -1;

 fail_hdr:
 	__IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),
 			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 struct ctl_table ip6_frags_ns_ctl_table[] = {
 	{
 		.procname	= "ip6frag_high_thresh",
 		.maxlen		= sizeof(unsigned long),
 		.mode		= 0644,
 		.proc_handler	= proc_doulongvec_minmax,
 	},
 	{
 		.procname	= "ip6frag_low_thresh",
 		.maxlen		= sizeof(unsigned long),
 		.mode		= 0644,
 		.proc_handler	= proc_doulongvec_minmax,
 	},
 	{
 		.procname	= "ip6frag_time",
 		.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.fqdir->high_thresh;
 	table[0].extra1	= &net->ipv6.fqdir->low_thresh;
 	table[1].data	= &net->ipv6.fqdir->low_thresh;
 	table[1].extra2	= &net->ipv6.fqdir->high_thresh;
 	table[2].data	= &net->ipv6.fqdir->timeout;

 	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;

 	res = fqdir_init(&net->ipv6.fqdir, &ip6_frags, net);
 	if (res < 0)
 		return res;

 	net->ipv6.fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH;
 	net->ipv6.fqdir->low_thresh = IPV6_FRAG_LOW_THRESH;
 	net->ipv6.fqdir->timeout = IPV6_FRAG_TIMEOUT;

 	res = ip6_frags_ns_sysctl_register(net);
 	if (res < 0)
 		fqdir_exit(net->ipv6.fqdir);
 	return res;
 }

 static void __net_exit ipv6_frags_pre_exit_net(struct net *net)
 {
 	fqdir_pre_exit(net->ipv6.fqdir);
 }

 static void __net_exit ipv6_frags_exit_net(struct net *net)
 {
 	ip6_frags_ns_sysctl_unregister(net);
 	fqdir_exit(net->ipv6.fqdir);
 }

 static struct pernet_operations ip6_frags_ops = {
 	.init		= ipv6_frags_init_net,
 	.pre_exit	= ipv6_frags_pre_exit_net,
 	.exit		= ipv6_frags_exit_net,
 };

 static const struct rhashtable_params ip6_rhash_params = {
 	.head_offset		= offsetof(struct inet_frag_queue, node),
 	.hashfn			= ip6frag_key_hashfn,
 	.obj_hashfn		= ip6frag_obj_hashfn,
 	.obj_cmpfn		= ip6frag_obj_cmpfn,
 	.automatic_shrinking	= true,
 };

 int __init ipv6_frag_init(void)
 {
 	int ret;

 	ip6_frags.constructor = ip6frag_init;
 	ip6_frags.destructor = NULL;
 	ip6_frags.qsize = sizeof(struct frag_queue);
 	ip6_frags.frag_expire = ip6_frag_expire;
 	ip6_frags.frags_cache_name = ip6_frag_cache_name;
 	ip6_frags.rhash_params = ip6_rhash_params;
 	ret = inet_frags_init(&ip6_frags);
 	if (ret)
 		goto out;

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

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

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

 out:
 	return ret;

 err_pernet:
 	ip6_frags_sysctl_unregister();
 err_sysctl:
 	inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT);
 err_protocol:
 	inet_frags_fini(&ip6_frags);
 	goto out;
 }

 void ipv6_frag_exit(void)
 {
 	ip6_frags_sysctl_unregister();
 	unregister_pernet_subsys(&ip6_frags_ops);
 	inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT);
 	inet_frags_fini(&ip6_frags);
 }
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* IPv6 fragment reassembly
	* Linux INET6 implementation
	*
	* Authors:
	* Pedro Roque <[email protected]>
	*
	* Based on: net/ipv4/ip_fragment.c
	*/

	/*
	* 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/ipv6_frag.h>
	#include <net/inet_ecn.h>

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

	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 skb,
	struct sk_buff prev_tail, struct net_device dev);

	static void ip6_frag_expire(struct timer_list *t)
	{
	struct inet_frag_queue *frag = from_timer(frag, t, timer);
	struct frag_queue *fq;

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

	ip6frag_expire_frag_queue(fq->q.fqdir->net, fq);
	}

	static struct frag_queue *
	fq_find(struct net net, __be32 id, const struct ipv6hdr hdr, int iif)
	{
	struct frag_v6_compare_key key = {
	.id = id,
	.saddr = hdr->saddr,
	.daddr = hdr->daddr,
	.user = IP6_DEFRAG_LOCAL_DELIVER,
	.iif = iif,
	};
	struct inet_frag_queue *q;

	if (!(ipv6_addr_type(&hdr->daddr) & (IPV6_ADDR_MULTICAST \|
	IPV6_ADDR_LINKLOCAL)))
	key.iif = 0;

	q = inet_frag_find(net->ipv6.fqdir, &key);
	if (!q)
	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,
	u32 *prob_offset)
	{
	struct net *net = dev_net(skb_dst(skb)->dev);
	int offset, end, fragsize;
	struct sk_buff *prev_tail;
	struct net_device *dev;
	int err = -ENOENT;
	u8 ecn;

	if (fq->q.flags & INET_FRAG_COMPLETE)
	goto err;

	err = -EINVAL;
	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) {
	prob_offset = (u8 )&fhdr->frag_off - skb_network_header(skb);
	/* note that if prob_offset is set, the skb is freed elsewhere,
	* we do not free it here.
	*/
	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 discard_fq;
	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
	*/
	*prob_offset = 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 discard_fq;
	fq->q.len = end;
	}
	}

	if (end == offset)
	goto discard_fq;

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

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

	/* Note : skb->rbnode and skb->dev share the same location. */
	dev = skb->dev;
	/* Makes sure compiler wont do silly aliasing games */
	barrier();

	prev_tail = fq->q.fragments_tail;
	err = inet_frag_queue_insert(&fq->q, skb, offset, end);
	if (err)
	goto insert_error;

	if (dev)
	fq->iif = dev->ifindex;

	fq->q.stamp = skb->tstamp;
	fq->q.meat += skb->len;
	fq->ecn \|= ecn;
	add_frag_mem_limit(fq->q.fqdir, skb->truesize);

	fragsize = -skb_network_offset(skb) + skb->len;
	if (fragsize > fq->q.max_size)
	fq->q.max_size = fragsize;

	/* 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) {
	unsigned long orefdst = skb->_skb_refdst;

	skb->_skb_refdst = 0UL;
	err = ip6_frag_reasm(fq, skb, prev_tail, dev);
	skb->_skb_refdst = orefdst;
	return err;
	}

	skb_dst_drop(skb);
	return -EINPROGRESS;

	insert_error:
	if (err == IPFRAG_DUP) {
	kfree_skb(skb);
	return -EINVAL;
	}
	err = -EINVAL;
	__IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
	IPSTATS_MIB_REASM_OVERLAPS);
	discard_fq:
	inet_frag_kill(&fq->q);
	__IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
	IPSTATS_MIB_REASMFAILS);
	err:
	kfree_skb(skb);
	return err;
	}

	/*
	* Check if this packet is complete.
	*
	* 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 skb,
	struct sk_buff prev_tail, struct net_device dev)
	{
	struct net *net = fq->q.fqdir->net;
	unsigned int nhoff;
	void *reasm_data;
	int payload_len;
	u8 ecn;

	inet_frag_kill(&fq->q);

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

	reasm_data = inet_frag_reasm_prepare(&fq->q, skb, prev_tail);
	if (!reasm_data)
	goto out_oom;

	payload_len = ((skb->data - skb_network_header(skb)) -
	sizeof(struct ipv6hdr) + fq->q.len -
	sizeof(struct frag_hdr));
	if (payload_len > IPV6_MAXPLEN)
	goto out_oversize;

	/* We have to remove fragment header from datagram and to relocate
	* header in order to calculate ICV correctly. */
	nhoff = fq->nhoffset;
	skb_network_header(skb)[nhoff] = skb_transport_header(skb)[0];
	memmove(skb->head + sizeof(struct frag_hdr), skb->head,
	(skb->data - skb->head) - sizeof(struct frag_hdr));
	if (skb_mac_header_was_set(skb))
	skb->mac_header += sizeof(struct frag_hdr);
	skb->network_header += sizeof(struct frag_hdr);

	skb_reset_transport_header(skb);

	inet_frag_reasm_finish(&fq->q, skb, reasm_data);

	skb->dev = dev;
	ipv6_hdr(skb)->payload_len = htons(payload_len);
	ipv6_change_dsfield(ipv6_hdr(skb), 0xff, ecn);
	IP6CB(skb)->nhoff = nhoff;
	IP6CB(skb)->flags \|= IP6SKB_FRAGMENTED;
	IP6CB(skb)->frag_max_size = fq->q.max_size;

	/* Yes, and fold redundant checksum back. 8) */
	skb_postpush_rcsum(skb, skb_network_header(skb),
	skb_network_header_len(skb));

	rcu_read_lock();
	__IP6_INC_STATS(net, __in6_dev_stats_get(dev, skb), IPSTATS_MIB_REASMOKS);
	rcu_read_unlock();
	fq->q.rb_fragments = RB_ROOT;
	fq->q.fragments_tail = NULL;
	fq->q.last_run_head = NULL;
	return 1;

	out_oversize:
	net_dbg_ratelimited("ip6_frag_reasm: payload len = %d\n", payload_len);
	goto out_fail;
	out_oom:
	net_dbg_ratelimited("ip6_frag_reasm: no memory for reassembly\n");
	out_fail:
	rcu_read_lock();
	__IP6_INC_STATS(net, __in6_dev_stats_get(dev, skb), IPSTATS_MIB_REASMFAILS);
	rcu_read_unlock();
	inet_frag_kill(&fq->q);
	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);
	int iif;

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

	__IP6_INC_STATS(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(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;
	}

	iif = skb->dev ? skb->dev->ifindex : 0;
	fq = fq_find(net, fhdr->identification, hdr, iif);
	if (fq) {
	u32 prob_offset = 0;
	int ret;

	spin_lock(&fq->q.lock);

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

	spin_unlock(&fq->q.lock);
	inet_frag_put(&fq->q);
	if (prob_offset) {
	__IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),
	IPSTATS_MIB_INHDRERRORS);
	/* icmpv6_param_prob() calls kfree_skb(skb) */
	icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, prob_offset);
	}
	return ret;
	}

	__IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMFAILS);
	kfree_skb(skb);
	return -1;

	fail_hdr:
	__IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),
	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 struct ctl_table ip6_frags_ns_ctl_table[] = {
	{
	.procname = "ip6frag_high_thresh",
	.maxlen = sizeof(unsigned long),
	.mode = 0644,
	.proc_handler = proc_doulongvec_minmax,
	},
	{
	.procname = "ip6frag_low_thresh",
	.maxlen = sizeof(unsigned long),
	.mode = 0644,
	.proc_handler = proc_doulongvec_minmax,
	},
	{
	.procname = "ip6frag_time",
	.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.fqdir->high_thresh;
	table[0].extra1 = &net->ipv6.fqdir->low_thresh;
	table[1].data = &net->ipv6.fqdir->low_thresh;
	table[1].extra2 = &net->ipv6.fqdir->high_thresh;
	table[2].data = &net->ipv6.fqdir->timeout;

	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;

	res = fqdir_init(&net->ipv6.fqdir, &ip6_frags, net);
	if (res < 0)
	return res;

	net->ipv6.fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH;
	net->ipv6.fqdir->low_thresh = IPV6_FRAG_LOW_THRESH;
	net->ipv6.fqdir->timeout = IPV6_FRAG_TIMEOUT;

	res = ip6_frags_ns_sysctl_register(net);
	if (res < 0)
	fqdir_exit(net->ipv6.fqdir);
	return res;
	}

	static void __net_exit ipv6_frags_pre_exit_net(struct net *net)
	{
	fqdir_pre_exit(net->ipv6.fqdir);
	}

	static void __net_exit ipv6_frags_exit_net(struct net *net)
	{
	ip6_frags_ns_sysctl_unregister(net);
	fqdir_exit(net->ipv6.fqdir);
	}

	static struct pernet_operations ip6_frags_ops = {
	.init = ipv6_frags_init_net,
	.pre_exit = ipv6_frags_pre_exit_net,
	.exit = ipv6_frags_exit_net,
	};

	static const struct rhashtable_params ip6_rhash_params = {
	.head_offset = offsetof(struct inet_frag_queue, node),
	.hashfn = ip6frag_key_hashfn,
	.obj_hashfn = ip6frag_obj_hashfn,
	.obj_cmpfn = ip6frag_obj_cmpfn,
	.automatic_shrinking = true,
	};

	int __init ipv6_frag_init(void)
	{
	int ret;

	ip6_frags.constructor = ip6frag_init;
	ip6_frags.destructor = NULL;
	ip6_frags.qsize = sizeof(struct frag_queue);
	ip6_frags.frag_expire = ip6_frag_expire;
	ip6_frags.frags_cache_name = ip6_frag_cache_name;
	ip6_frags.rhash_params = ip6_rhash_params;
	ret = inet_frags_init(&ip6_frags);
	if (ret)
	goto out;

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

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

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

	out:
	return ret;

	err_pernet:
	ip6_frags_sysctl_unregister();
	err_sysctl:
	inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT);
	err_protocol:
	inet_frags_fini(&ip6_frags);
	goto out;
	}

	void ipv6_frag_exit(void)
	{
	ip6_frags_sysctl_unregister();
	unregister_pernet_subsys(&ip6_frags_ops);
	inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT);
	inet_frags_fini(&ip6_frags);
	}