/*
   *	IPv6 output functions

   *	Linux INET6 implementation

   *
   *	Authors:

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

   *

   *	Based on linux/net/ipv4/ip_output.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.
   *
   *	Changes:
   *	A.N.Kuznetsov	:	airthmetics in fragmentation.
   *				extension headers are implemented.
   *				route changes now work.
   *				ip6_forward does not confuse sniffers.
   *				etc.
   *
   *      H. von Brand    :       Added missing #include <linux/string.h>

   *	Imran Patel	:	frag id should be in NBO

   *      Kazunori MIYAZAWA @USAGI
   *			:       add ip6_append_data and related functions
   *				for datagram xmit
   */

  #include <linux/errno.h>

  #include <linux/kernel.h>

  #include <linux/string.h>
  #include <linux/socket.h>
  #include <linux/net.h>
  #include <linux/netdevice.h>
  #include <linux/if_arp.h>
  #include <linux/in6.h>
  #include <linux/tcp.h>
  #include <linux/route.h>

  #include <linux/module.h>

  #include <linux/slab.h>

  #include <linux/bpf-cgroup.h>

  #include <linux/netfilter.h>
  #include <linux/netfilter_ipv6.h>
  
  #include <net/sock.h>
  #include <net/snmp.h>
  
  #include <net/ipv6.h>
  #include <net/ndisc.h>
  #include <net/protocol.h>
  #include <net/ip6_route.h>
  #include <net/addrconf.h>
  #include <net/rawv6.h>
  #include <net/icmp.h>
  #include <net/xfrm.h>
  #include <net/checksum.h>

  #include <linux/mroute6.h>

  #include <net/l3mdev.h>

  #include <net/lwtunnel.h>

  static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff *skb)

  {

  	struct dst_entry *dst = skb_dst(skb);

  	struct net_device *dev = dst->dev;

  	struct neighbour *neigh;

  	struct in6_addr *nexthop;
  	int ret;

  	if (ipv6_addr_is_multicast(&ipv6_hdr(skb)->daddr)) {

  		struct inet6_dev *idev = ip6_dst_idev(skb_dst(skb));

  		if (!(dev->flags & IFF_LOOPBACK) && sk_mc_loop(sk) &&

  		    ((mroute6_socket(net, skb) &&

  		     !(IP6CB(skb)->flags & IP6SKB_FORWARDED)) ||

  		     ipv6_chk_mcast_addr(dev, &ipv6_hdr(skb)->daddr,
  					 &ipv6_hdr(skb)->saddr))) {

  			struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
  
  			/* Do not check for IFF_ALLMULTI; multicast routing
  			   is not supported in any case.
  			 */
  			if (newskb)

  				NF_HOOK(NFPROTO_IPV6, NF_INET_POST_ROUTING,

  					net, sk, newskb, NULL, newskb->dev,

  					dev_loopback_xmit);

  			if (ipv6_hdr(skb)->hop_limit == 0) {

  				IP6_INC_STATS(net, idev,

  					      IPSTATS_MIB_OUTDISCARDS);

  				kfree_skb(skb);
  				return 0;
  			}
  		}

  		IP6_UPD_PO_STATS(net, idev, IPSTATS_MIB_OUTMCAST, skb->len);

  
  		if (IPV6_ADDR_MC_SCOPE(&ipv6_hdr(skb)->daddr) <=
  		    IPV6_ADDR_SCOPE_NODELOCAL &&
  		    !(dev->flags & IFF_LOOPBACK)) {
  			kfree_skb(skb);
  			return 0;
  		}

  	}

  	if (lwtunnel_xmit_redirect(dst->lwtstate)) {
  		int res = lwtunnel_xmit(skb);
  
  		if (res < 0 || res == LWTUNNEL_XMIT_DONE)
  			return res;
  	}

  	rcu_read_lock_bh();

  	nexthop = rt6_nexthop((struct rt6_info *)dst, &ipv6_hdr(skb)->daddr);

  	neigh = __ipv6_neigh_lookup_noref(dst->dev, nexthop);
  	if (unlikely(!neigh))
  		neigh = __neigh_create(&nd_tbl, nexthop, dst->dev, false);
  	if (!IS_ERR(neigh)) {

  		sock_confirm_neigh(skb, neigh);

  		ret = neigh_output(neigh, skb);

  		rcu_read_unlock_bh();
  		return ret;
  	}
  	rcu_read_unlock_bh();

  	IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTNOROUTES);

  	kfree_skb(skb);
  	return -EINVAL;

  }

  static int ip6_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)

  {

  	int ret;
  
  	ret = BPF_CGROUP_RUN_PROG_INET_EGRESS(sk, skb);
  	if (ret) {
  		kfree_skb(skb);
  		return ret;
  	}

  #if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
  	/* Policy lookup after SNAT yielded a new policy */
  	if (skb_dst(skb)->xfrm) {
  		IPCB(skb)->flags |= IPSKB_REROUTED;
  		return dst_output(net, sk, skb);
  	}
  #endif

  	if ((skb->len > ip6_skb_dst_mtu(skb) && !skb_is_gso(skb)) ||

  	    dst_allfrag(skb_dst(skb)) ||
  	    (IP6CB(skb)->frag_max_size && skb->len > IP6CB(skb)->frag_max_size))

  		return ip6_fragment(net, sk, skb, ip6_finish_output2);

  	else

  		return ip6_finish_output2(net, sk, skb);

  }

  int ip6_output(struct net *net, struct sock *sk, struct sk_buff *skb)

  {

  	struct net_device *dev = skb_dst(skb)->dev;

  	struct inet6_dev *idev = ip6_dst_idev(skb_dst(skb));

  	skb->protocol = htons(ETH_P_IPV6);
  	skb->dev = dev;

  	if (unlikely(idev->cnf.disable_ipv6)) {

  		IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTDISCARDS);

  		kfree_skb(skb);
  		return 0;
  	}

  	return NF_HOOK_COND(NFPROTO_IPV6, NF_INET_POST_ROUTING,
  			    net, sk, skb, NULL, dev,

  			    ip6_finish_output,
  			    !(IP6CB(skb)->flags & IP6SKB_REROUTED));

  }

  bool ip6_autoflowlabel(struct net *net, const struct ipv6_pinfo *np)

  {
  	if (!np->autoflowlabel_set)
  		return ip6_default_np_autolabel(net);
  	else
  		return np->autoflowlabel;
  }

  /*

   * xmit an sk_buff (used by TCP, SCTP and DCCP)
   * Note : socket lock is not held for SYNACK packets, but might be modified
   * by calls to skb_set_owner_w() and ipv6_local_error(),
   * which are using proper atomic operations or spinlocks.

   */

  int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,

  	     __u32 mark, struct ipv6_txoptions *opt, int tclass)

  {

  	struct net *net = sock_net(sk);

  	const struct ipv6_pinfo *np = inet6_sk(sk);

  	struct in6_addr *first_hop = &fl6->daddr;

  	struct dst_entry *dst = skb_dst(skb);

  	unsigned int head_room;

  	struct ipv6hdr *hdr;

  	u8  proto = fl6->flowi6_proto;

  	int seg_len = skb->len;

  	int hlimit = -1;

  	u32 mtu;

  	head_room = sizeof(struct ipv6hdr) + LL_RESERVED_SPACE(dst->dev);
  	if (opt)
  		head_room += opt->opt_nflen + opt->opt_flen;
  
  	if (unlikely(skb_headroom(skb) < head_room)) {
  		struct sk_buff *skb2 = skb_realloc_headroom(skb, head_room);
  		if (!skb2) {
  			IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
  				      IPSTATS_MIB_OUTDISCARDS);
  			kfree_skb(skb);
  			return -ENOBUFS;

  		}

  		if (skb->sk)
  			skb_set_owner_w(skb2, skb->sk);
  		consume_skb(skb);
  		skb = skb2;
  	}
  
  	if (opt) {
  		seg_len += opt->opt_nflen + opt->opt_flen;

  		if (opt->opt_flen)
  			ipv6_push_frag_opts(skb, opt, &proto);

  		if (opt->opt_nflen)

  			ipv6_push_nfrag_opts(skb, opt, &proto, &first_hop,
  					     &fl6->saddr);

  	}

  	skb_push(skb, sizeof(struct ipv6hdr));
  	skb_reset_network_header(skb);

  	hdr = ipv6_hdr(skb);

  
  	/*
  	 *	Fill in the IPv6 header
  	 */

  	if (np)

  		hlimit = np->hop_limit;
  	if (hlimit < 0)

  		hlimit = ip6_dst_hoplimit(dst);

  	ip6_flow_hdr(hdr, tclass, ip6_make_flowlabel(net, skb, fl6->flowlabel,

  				ip6_autoflowlabel(net, np), fl6));

  	hdr->payload_len = htons(seg_len);
  	hdr->nexthdr = proto;
  	hdr->hop_limit = hlimit;

  	hdr->saddr = fl6->saddr;
  	hdr->daddr = *first_hop;

  	skb->protocol = htons(ETH_P_IPV6);

  	skb->priority = sk->sk_priority;

  	skb->mark = mark;

  	mtu = dst_mtu(dst);

  	if ((skb->len <= mtu) || skb->ignore_df || skb_is_gso(skb)) {

  		IP6_UPD_PO_STATS(net, ip6_dst_idev(skb_dst(skb)),

  			      IPSTATS_MIB_OUT, skb->len);

  
  		/* if egress device is enslaved to an L3 master device pass the
  		 * skb to its handler for processing
  		 */
  		skb = l3mdev_ip6_out((struct sock *)sk, skb);
  		if (unlikely(!skb))
  			return 0;

  		/* hooks should never assume socket lock is held.
  		 * we promote our socket to non const
  		 */

  		return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT,

  			       net, (struct sock *)sk, skb, NULL, dst->dev,

  			       dst_output);

  	}

  	skb->dev = dst->dev;

  	/* ipv6_local_error() does not require socket lock,
  	 * we promote our socket to non const
  	 */
  	ipv6_local_error((struct sock *)sk, EMSGSIZE, fl6, mtu);

  	IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_FRAGFAILS);

  	kfree_skb(skb);
  	return -EMSGSIZE;
  }

  EXPORT_SYMBOL(ip6_xmit);

  static int ip6_call_ra_chain(struct sk_buff *skb, int sel)
  {
  	struct ip6_ra_chain *ra;
  	struct sock *last = NULL;
  
  	read_lock(&ip6_ra_lock);
  	for (ra = ip6_ra_chain; ra; ra = ra->next) {
  		struct sock *sk = ra->sk;

  		if (sk && ra->sel == sel &&
  		    (!sk->sk_bound_dev_if ||
  		     sk->sk_bound_dev_if == skb->dev->ifindex)) {

  			if (last) {
  				struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);
  				if (skb2)
  					rawv6_rcv(last, skb2);
  			}
  			last = sk;
  		}
  	}
  
  	if (last) {
  		rawv6_rcv(last, skb);
  		read_unlock(&ip6_ra_lock);
  		return 1;
  	}
  	read_unlock(&ip6_ra_lock);
  	return 0;
  }

  static int ip6_forward_proxy_check(struct sk_buff *skb)
  {

  	struct ipv6hdr *hdr = ipv6_hdr(skb);

  	u8 nexthdr = hdr->nexthdr;

  	__be16 frag_off;

  	int offset;
  
  	if (ipv6_ext_hdr(nexthdr)) {

  		offset = ipv6_skip_exthdr(skb, sizeof(*hdr), &nexthdr, &frag_off);

  		if (offset < 0)
  			return 0;
  	} else
  		offset = sizeof(struct ipv6hdr);
  
  	if (nexthdr == IPPROTO_ICMPV6) {
  		struct icmp6hdr *icmp6;

  		if (!pskb_may_pull(skb, (skb_network_header(skb) +
  					 offset + 1 - skb->data)))

  			return 0;

  		icmp6 = (struct icmp6hdr *)(skb_network_header(skb) + offset);

  
  		switch (icmp6->icmp6_type) {
  		case NDISC_ROUTER_SOLICITATION:
  		case NDISC_ROUTER_ADVERTISEMENT:
  		case NDISC_NEIGHBOUR_SOLICITATION:
  		case NDISC_NEIGHBOUR_ADVERTISEMENT:
  		case NDISC_REDIRECT:
  			/* For reaction involving unicast neighbor discovery
  			 * message destined to the proxied address, pass it to
  			 * input function.
  			 */
  			return 1;
  		default:
  			break;
  		}
  	}

  	/*
  	 * The proxying router can't forward traffic sent to a link-local
  	 * address, so signal the sender and discard the packet. This
  	 * behavior is clarified by the MIPv6 specification.
  	 */
  	if (ipv6_addr_type(&hdr->daddr) & IPV6_ADDR_LINKLOCAL) {
  		dst_link_failure(skb);
  		return -1;
  	}

  	return 0;
  }

  static inline int ip6_forward_finish(struct net *net, struct sock *sk,
  				     struct sk_buff *skb)

  {

  	struct dst_entry *dst = skb_dst(skb);
  
  	__IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTFORWDATAGRAMS);
  	__IP6_ADD_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTOCTETS, skb->len);

  	return dst_output(net, sk, skb);

  }

  static unsigned int ip6_dst_mtu_forward(const struct dst_entry *dst)
  {
  	unsigned int mtu;
  	struct inet6_dev *idev;
  
  	if (dst_metric_locked(dst, RTAX_MTU)) {
  		mtu = dst_metric_raw(dst, RTAX_MTU);
  		if (mtu)
  			return mtu;
  	}
  
  	mtu = IPV6_MIN_MTU;
  	rcu_read_lock();
  	idev = __in6_dev_get(dst->dev);
  	if (idev)
  		mtu = idev->cnf.mtu6;
  	rcu_read_unlock();
  
  	return mtu;
  }

  static bool ip6_pkt_too_big(const struct sk_buff *skb, unsigned int mtu)
  {

  	if (skb->len <= mtu)

  		return false;

  	/* ipv6 conntrack defrag sets max_frag_size + ignore_df */

  	if (IP6CB(skb)->frag_max_size && IP6CB(skb)->frag_max_size > mtu)
  		return true;

  	if (skb->ignore_df)

  		return false;

  	if (skb_is_gso(skb) && skb_gso_validate_mtu(skb, mtu))

  		return false;
  
  	return true;
  }

  int ip6_forward(struct sk_buff *skb)
  {

  	struct dst_entry *dst = skb_dst(skb);

  	struct ipv6hdr *hdr = ipv6_hdr(skb);

  	struct inet6_skb_parm *opt = IP6CB(skb);

  	struct net *net = dev_net(dst->dev);

  	u32 mtu;

  	if (net->ipv6.devconf_all->forwarding == 0)

  		goto error;

  	if (skb->pkt_type != PACKET_HOST)
  		goto drop;

  	if (unlikely(skb->sk))
  		goto drop;

  	if (skb_warn_if_lro(skb))
  		goto drop;

  	if (!xfrm6_policy_check(NULL, XFRM_POLICY_FWD, skb)) {

  		__IP6_INC_STATS(net, ip6_dst_idev(dst),
  				IPSTATS_MIB_INDISCARDS);

  		goto drop;
  	}

  	skb_forward_csum(skb);

  
  	/*
  	 *	We DO NOT make any processing on
  	 *	RA packets, pushing them to user level AS IS
  	 *	without ane WARRANTY that application will be able
  	 *	to interpret them. The reason is that we
  	 *	cannot make anything clever here.
  	 *
  	 *	We are not end-node, so that if packet contains
  	 *	AH/ESP, we cannot make anything.
  	 *	Defragmentation also would be mistake, RA packets
  	 *	cannot be fragmented, because there is no warranty
  	 *	that different fragments will go along one path. --ANK
  	 */

  	if (unlikely(opt->flags & IP6SKB_ROUTERALERT)) {
  		if (ip6_call_ra_chain(skb, ntohs(opt->ra)))

  			return 0;
  	}
  
  	/*
  	 *	check and decrement ttl
  	 */
  	if (hdr->hop_limit <= 1) {
  		/* Force OUTPUT device used as source address */
  		skb->dev = dst->dev;

  		icmpv6_send(skb, ICMPV6_TIME_EXCEED, ICMPV6_EXC_HOPLIMIT, 0);

  		__IP6_INC_STATS(net, ip6_dst_idev(dst),
  				IPSTATS_MIB_INHDRERRORS);

  
  		kfree_skb(skb);
  		return -ETIMEDOUT;
  	}

  	/* XXX: idev->cnf.proxy_ndp? */

  	if (net->ipv6.devconf_all->proxy_ndp &&

  	    pneigh_lookup(&nd_tbl, net, &hdr->daddr, skb->dev, 0)) {

  		int proxied = ip6_forward_proxy_check(skb);
  		if (proxied > 0)

  			return ip6_input(skb);

  		else if (proxied < 0) {

  			__IP6_INC_STATS(net, ip6_dst_idev(dst),
  					IPSTATS_MIB_INDISCARDS);

  			goto drop;
  		}

  	}

  	if (!xfrm6_route_forward(skb)) {

  		__IP6_INC_STATS(net, ip6_dst_idev(dst),
  				IPSTATS_MIB_INDISCARDS);

  		goto drop;
  	}

  	dst = skb_dst(skb);

  
  	/* IPv6 specs say nothing about it, but it is clear that we cannot
  	   send redirects to source routed frames.

  	   We don't send redirects to frames decapsulated from IPsec.

  	 */

  	if (IP6CB(skb)->iif == dst->dev->ifindex &&
  	    opt->srcrt == 0 && !skb_sec_path(skb)) {

  		struct in6_addr *target = NULL;

  		struct inet_peer *peer;

  		struct rt6_info *rt;

  
  		/*
  		 *	incoming and outgoing devices are the same
  		 *	send a redirect.
  		 */
  
  		rt = (struct rt6_info *) dst;

  		if (rt->rt6i_flags & RTF_GATEWAY)
  			target = &rt->rt6i_gateway;

  		else
  			target = &hdr->daddr;

  		peer = inet_getpeer_v6(net->ipv6.peers, &hdr->daddr, 1);

  		/* Limit redirects both by destination (here)
  		   and by source (inside ndisc_send_redirect)
  		 */

  		if (inet_peer_xrlim_allow(peer, 1*HZ))

  			ndisc_send_redirect(skb, target);

  		if (peer)
  			inet_putpeer(peer);

  	} else {
  		int addrtype = ipv6_addr_type(&hdr->saddr);

  		/* This check is security critical. */

  		if (addrtype == IPV6_ADDR_ANY ||
  		    addrtype & (IPV6_ADDR_MULTICAST | IPV6_ADDR_LOOPBACK))

  			goto error;
  		if (addrtype & IPV6_ADDR_LINKLOCAL) {
  			icmpv6_send(skb, ICMPV6_DEST_UNREACH,

  				    ICMPV6_NOT_NEIGHBOUR, 0);

  			goto error;
  		}

  	}

  	mtu = ip6_dst_mtu_forward(dst);

  	if (mtu < IPV6_MIN_MTU)
  		mtu = IPV6_MIN_MTU;

  	if (ip6_pkt_too_big(skb, mtu)) {

  		/* Again, force OUTPUT device used as source address */
  		skb->dev = dst->dev;

  		icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);

  		__IP6_INC_STATS(net, ip6_dst_idev(dst),
  				IPSTATS_MIB_INTOOBIGERRORS);
  		__IP6_INC_STATS(net, ip6_dst_idev(dst),
  				IPSTATS_MIB_FRAGFAILS);

  		kfree_skb(skb);
  		return -EMSGSIZE;
  	}
  
  	if (skb_cow(skb, dst->dev->hard_header_len)) {

  		__IP6_INC_STATS(net, ip6_dst_idev(dst),
  				IPSTATS_MIB_OUTDISCARDS);

  		goto drop;
  	}

  	hdr = ipv6_hdr(skb);

  
  	/* Mangling hops number delayed to point after skb COW */

  	hdr->hop_limit--;

  	return NF_HOOK(NFPROTO_IPV6, NF_INET_FORWARD,
  		       net, NULL, skb, skb->dev, dst->dev,

  		       ip6_forward_finish);

  
  error:

  	__IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_INADDRERRORS);

  drop:
  	kfree_skb(skb);
  	return -EINVAL;
  }
  
  static void ip6_copy_metadata(struct sk_buff *to, struct sk_buff *from)
  {
  	to->pkt_type = from->pkt_type;
  	to->priority = from->priority;
  	to->protocol = from->protocol;

  	skb_dst_drop(to);
  	skb_dst_set(to, dst_clone(skb_dst(from)));

  	to->dev = from->dev;

  	to->mark = from->mark;

  	skb_copy_hash(to, from);

  #ifdef CONFIG_NET_SCHED
  	to->tc_index = from->tc_index;
  #endif

  	nf_copy(to, from);

  	skb_copy_secmark(to, from);

  }

  int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
  		 int (*output)(struct net *, struct sock *, struct sk_buff *))

  {

  	struct sk_buff *frag;

  	struct rt6_info *rt = (struct rt6_info *)skb_dst(skb);

  	struct ipv6_pinfo *np = skb->sk && !dev_recursion_level() ?
  				inet6_sk(skb->sk) : NULL;

  	struct ipv6hdr *tmp_hdr;
  	struct frag_hdr *fh;
  	unsigned int mtu, hlen, left, len;

  	int hroom, troom;

  	__be32 frag_id;

  	int ptr, offset = 0, err = 0;

  	u8 *prevhdr, nexthdr = 0;

  	err = ip6_find_1stfragopt(skb, &prevhdr);
  	if (err < 0)

  		goto fail;

  	hlen = err;

  	nexthdr = *prevhdr;

  	mtu = ip6_skb_dst_mtu(skb);

  
  	/* We must not fragment if the socket is set to force MTU discovery

  	 * or if the skb it not generated by a local socket.

  	 */

  	if (unlikely(!skb->ignore_df && skb->len > mtu))
  		goto fail_toobig;

  	if (IP6CB(skb)->frag_max_size) {
  		if (IP6CB(skb)->frag_max_size > mtu)
  			goto fail_toobig;
  
  		/* don't send fragments larger than what we received */
  		mtu = IP6CB(skb)->frag_max_size;
  		if (mtu < IPV6_MIN_MTU)
  			mtu = IPV6_MIN_MTU;

  	}

  	if (np && np->frag_size < mtu) {
  		if (np->frag_size)
  			mtu = np->frag_size;
  	}

  	if (mtu < hlen + sizeof(struct frag_hdr) + 8)

  		goto fail_toobig;

  	mtu -= hlen + sizeof(struct frag_hdr);

  	frag_id = ipv6_select_ident(net, &ipv6_hdr(skb)->daddr,
  				    &ipv6_hdr(skb)->saddr);

  	if (skb->ip_summed == CHECKSUM_PARTIAL &&
  	    (err = skb_checksum_help(skb)))
  		goto fail;

  	hroom = LL_RESERVED_SPACE(rt->dst.dev);

  	if (skb_has_frag_list(skb)) {

  		unsigned int first_len = skb_pagelen(skb);

  		struct sk_buff *frag2;

  
  		if (first_len - hlen > mtu ||
  		    ((first_len - hlen) & 7) ||

  		    skb_cloned(skb) ||
  		    skb_headroom(skb) < (hroom + sizeof(struct frag_hdr)))

  			goto slow_path;

  		skb_walk_frags(skb, frag) {

  			/* Correct geometry. */
  			if (frag->len > mtu ||
  			    ((frag->len & 7) && frag->next) ||

  			    skb_headroom(frag) < (hlen + hroom + sizeof(struct frag_hdr)))

  				goto slow_path_clean;

  			/* Partially cloned skb? */
  			if (skb_shared(frag))

  				goto slow_path_clean;

  
  			BUG_ON(frag->sk);
  			if (skb->sk) {

  				frag->sk = skb->sk;
  				frag->destructor = sock_wfree;

  			}

  			skb->truesize -= frag->truesize;

  		}
  
  		err = 0;
  		offset = 0;

  		/* BUILD HEADER */

  		*prevhdr = NEXTHDR_FRAGMENT;

  		tmp_hdr = kmemdup(skb_network_header(skb), hlen, GFP_ATOMIC);

  		if (!tmp_hdr) {

  			err = -ENOMEM;
  			goto fail;

  		}

  		frag = skb_shinfo(skb)->frag_list;
  		skb_frag_list_init(skb);

  		__skb_pull(skb, hlen);

  		fh = __skb_push(skb, sizeof(struct frag_hdr));

  		__skb_push(skb, hlen);
  		skb_reset_network_header(skb);

  		memcpy(skb_network_header(skb), tmp_hdr, hlen);

  		fh->nexthdr = nexthdr;
  		fh->reserved = 0;
  		fh->frag_off = htons(IP6_MF);

  		fh->identification = frag_id;

  
  		first_len = skb_pagelen(skb);
  		skb->data_len = first_len - skb_headlen(skb);
  		skb->len = first_len;

  		ipv6_hdr(skb)->payload_len = htons(first_len -
  						   sizeof(struct ipv6hdr));

  		for (;;) {
  			/* Prepare header of the next frame,
  			 * before previous one went down. */
  			if (frag) {
  				frag->ip_summed = CHECKSUM_NONE;

  				skb_reset_transport_header(frag);

  				fh = __skb_push(frag, sizeof(struct frag_hdr));

  				__skb_push(frag, hlen);
  				skb_reset_network_header(frag);

  				memcpy(skb_network_header(frag), tmp_hdr,
  				       hlen);

  				offset += skb->len - hlen - sizeof(struct frag_hdr);
  				fh->nexthdr = nexthdr;
  				fh->reserved = 0;
  				fh->frag_off = htons(offset);

  				if (frag->next)

  					fh->frag_off |= htons(IP6_MF);
  				fh->identification = frag_id;

  				ipv6_hdr(frag)->payload_len =
  						htons(frag->len -
  						      sizeof(struct ipv6hdr));

  				ip6_copy_metadata(frag, skb);
  			}

  			err = output(net, sk, skb);

  			if (!err)

  				IP6_INC_STATS(net, ip6_dst_idev(&rt->dst),

  					      IPSTATS_MIB_FRAGCREATES);

  			if (err || !frag)
  				break;
  
  			skb = frag;
  			frag = skb->next;
  			skb->next = NULL;
  		}

  		kfree(tmp_hdr);

  
  		if (err == 0) {

  			IP6_INC_STATS(net, ip6_dst_idev(&rt->dst),

  				      IPSTATS_MIB_FRAGOKS);

  			return 0;
  		}

  		kfree_skb_list(frag);

  		IP6_INC_STATS(net, ip6_dst_idev(&rt->dst),

  			      IPSTATS_MIB_FRAGFAILS);

  		return err;

  
  slow_path_clean:
  		skb_walk_frags(skb, frag2) {
  			if (frag2 == frag)
  				break;
  			frag2->sk = NULL;
  			frag2->destructor = NULL;
  			skb->truesize += frag2->truesize;
  		}

  	}
  
  slow_path:
  	left = skb->len - hlen;		/* Space per frame */
  	ptr = hlen;			/* Where to start from */
  
  	/*
  	 *	Fragment the datagram.
  	 */

  	troom = rt->dst.dev->needed_tailroom;

  
  	/*
  	 *	Keep copying data until we run out.
  	 */

  	while (left > 0)	{

  		u8 *fragnexthdr_offset;

  		len = left;
  		/* IF: it doesn't fit, use 'mtu' - the data space left */
  		if (len > mtu)
  			len = mtu;

  		/* IF: we are not sending up to and including the packet end

  		   then align the next start on an eight byte boundary */
  		if (len < left)	{
  			len &= ~7;
  		}

  		/* Allocate buffer */
  		frag = alloc_skb(len + hlen + sizeof(struct frag_hdr) +
  				 hroom + troom, GFP_ATOMIC);
  		if (!frag) {

  			err = -ENOMEM;
  			goto fail;
  		}
  
  		/*
  		 *	Set up data on packet
  		 */
  
  		ip6_copy_metadata(frag, skb);

  		skb_reserve(frag, hroom);

  		skb_put(frag, len + hlen + sizeof(struct frag_hdr));

  		skb_reset_network_header(frag);

  		fh = (struct frag_hdr *)(skb_network_header(frag) + hlen);

  		frag->transport_header = (frag->network_header + hlen +
  					  sizeof(struct frag_hdr));

  
  		/*
  		 *	Charge the memory for the fragment to any owner
  		 *	it might possess
  		 */
  		if (skb->sk)
  			skb_set_owner_w(frag, skb->sk);
  
  		/*
  		 *	Copy the packet header into the new buffer.
  		 */

  		skb_copy_from_linear_data(skb, skb_network_header(frag), hlen);

  		fragnexthdr_offset = skb_network_header(frag);
  		fragnexthdr_offset += prevhdr - skb_network_header(skb);
  		*fragnexthdr_offset = NEXTHDR_FRAGMENT;

  		/*
  		 *	Build fragment header.
  		 */
  		fh->nexthdr = nexthdr;
  		fh->reserved = 0;

  		fh->identification = frag_id;

  
  		/*
  		 *	Copy a block of the IP datagram.
  		 */

  		BUG_ON(skb_copy_bits(skb, ptr, skb_transport_header(frag),
  				     len));

  		left -= len;
  
  		fh->frag_off = htons(offset);
  		if (left > 0)
  			fh->frag_off |= htons(IP6_MF);

  		ipv6_hdr(frag)->payload_len = htons(frag->len -
  						    sizeof(struct ipv6hdr));

  
  		ptr += len;
  		offset += len;
  
  		/*
  		 *	Put this fragment into the sending queue.
  		 */

  		err = output(net, sk, frag);

  		if (err)
  			goto fail;

  		IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),

  			      IPSTATS_MIB_FRAGCREATES);

  	}

  	IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),

  		      IPSTATS_MIB_FRAGOKS);

  	consume_skb(skb);

  	return err;

  fail_toobig:
  	if (skb->sk && dst_allfrag(skb_dst(skb)))
  		sk_nocaps_add(skb->sk, NETIF_F_GSO_MASK);

  	icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
  	err = -EMSGSIZE;

  fail:

  	IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),

  		      IPSTATS_MIB_FRAGFAILS);

  	kfree_skb(skb);

  	return err;
  }

  static inline int ip6_rt_check(const struct rt6key *rt_key,
  			       const struct in6_addr *fl_addr,
  			       const struct in6_addr *addr_cache)

  {

  	return (rt_key->plen != 128 || !ipv6_addr_equal(fl_addr, &rt_key->addr)) &&

  		(!addr_cache || !ipv6_addr_equal(fl_addr, addr_cache));

  }

  static struct dst_entry *ip6_sk_dst_check(struct sock *sk,
  					  struct dst_entry *dst,

  					  const struct flowi6 *fl6)

  {

  	struct ipv6_pinfo *np = inet6_sk(sk);

  	struct rt6_info *rt;

  	if (!dst)
  		goto out;

  	if (dst->ops->family != AF_INET6) {
  		dst_release(dst);
  		return NULL;
  	}
  
  	rt = (struct rt6_info *)dst;

  	/* Yes, checking route validity in not connected
  	 * case is not very simple. Take into account,
  	 * that we do not support routing by source, TOS,

  	 * and MSG_DONTROUTE		--ANK (980726)

  	 *

  	 * 1. ip6_rt_check(): If route was host route,
  	 *    check that cached destination is current.

  	 *    If it is network route, we still may
  	 *    check its validity using saved pointer
  	 *    to the last used address: daddr_cache.
  	 *    We do not want to save whole address now,
  	 *    (because main consumer of this service
  	 *    is tcp, which has not this problem),
  	 *    so that the last trick works only on connected
  	 *    sockets.
  	 * 2. oif also should be the same.
  	 */

  	if (ip6_rt_check(&rt->rt6i_dst, &fl6->daddr, np->daddr_cache) ||

  #ifdef CONFIG_IPV6_SUBTREES

  	    ip6_rt_check(&rt->rt6i_src, &fl6->saddr, np->saddr_cache) ||

  #endif

  	   (!(fl6->flowi6_flags & FLOWI_FLAG_SKIP_NH_OIF) &&
  	      (fl6->flowi6_oif && fl6->flowi6_oif != dst->dev->ifindex))) {

  		dst_release(dst);
  		dst = NULL;

  	}

  out:
  	return dst;
  }

  static int ip6_dst_lookup_tail(struct net *net, const struct sock *sk,

  			       struct dst_entry **dst, struct flowi6 *fl6)

  {

  #ifdef CONFIG_IPV6_OPTIMISTIC_DAD
  	struct neighbour *n;

  	struct rt6_info *rt;

  #endif
  	int err;

  	int flags = 0;

  	/* The correct way to handle this would be to do
  	 * ip6_route_get_saddr, and then ip6_route_output; however,
  	 * the route-specific preferred source forces the
  	 * ip6_route_output call _before_ ip6_route_get_saddr.
  	 *
  	 * In source specific routing (no src=any default route),
  	 * ip6_route_output will fail given src=any saddr, though, so
  	 * that's why we try it again later.
  	 */
  	if (ipv6_addr_any(&fl6->saddr) && (!*dst || !(*dst)->error)) {
  		struct rt6_info *rt;
  		bool had_dst = *dst != NULL;

  		if (!had_dst)
  			*dst = ip6_route_output(net, sk, fl6);
  		rt = (*dst)->error ? NULL : (struct rt6_info *)*dst;

  		err = ip6_route_get_saddr(net, rt, &fl6->daddr,
  					  sk ? inet6_sk(sk)->srcprefs : 0,
  					  &fl6->saddr);

  		if (err)

  			goto out_err_release;

  
  		/* If we had an erroneous initial result, pretend it
  		 * never existed and let the SA-enabled version take
  		 * over.
  		 */
  		if (!had_dst && (*dst)->error) {
  			dst_release(*dst);
  			*dst = NULL;
  		}

  
  		if (fl6->flowi6_oif)
  			flags |= RT6_LOOKUP_F_IFACE;

  	}

  	if (!*dst)

  		*dst = ip6_route_output_flags(net, sk, fl6, flags);

  
  	err = (*dst)->error;
  	if (err)
  		goto out_err_release;

  #ifdef CONFIG_IPV6_OPTIMISTIC_DAD

  	/*
  	 * Here if the dst entry we've looked up
  	 * has a neighbour entry that is in the INCOMPLETE
  	 * state and the src address from the flow is
  	 * marked as OPTIMISTIC, we release the found
  	 * dst entry and replace it instead with the
  	 * dst entry of the nexthop router
  	 */

  	rt = (struct rt6_info *) *dst;

  	rcu_read_lock_bh();

  	n = __ipv6_neigh_lookup_noref(rt->dst.dev,
  				      rt6_nexthop(rt, &fl6->daddr));

  	err = n && !(n->nud_state & NUD_VALID) ? -EINVAL : 0;
  	rcu_read_unlock_bh();
  
  	if (err) {

  		struct inet6_ifaddr *ifp;

  		struct flowi6 fl_gw6;

  		int redirect;

  		ifp = ipv6_get_ifaddr(net, &fl6->saddr,

  				      (*dst)->dev, 1);
  
  		redirect = (ifp && ifp->flags & IFA_F_OPTIMISTIC);
  		if (ifp)
  			in6_ifa_put(ifp);
  
  		if (redirect) {
  			/*
  			 * We need to get the dst entry for the
  			 * default router instead
  			 */
  			dst_release(*dst);

  			memcpy(&fl_gw6, fl6, sizeof(struct flowi6));
  			memset(&fl_gw6.daddr, 0, sizeof(struct in6_addr));
  			*dst = ip6_route_output(net, sk, &fl_gw6);

  			err = (*dst)->error;
  			if (err)

  				goto out_err_release;

  		}

  	}

  #endif

  	if (ipv6_addr_v4mapped(&fl6->saddr) &&

  	    !(ipv6_addr_v4mapped(&fl6->daddr) || ipv6_addr_any(&fl6->daddr))) {
  		err = -EAFNOSUPPORT;
  		goto out_err_release;
  	}

  	return 0;
  
  out_err_release:
  	dst_release(*dst);
  	*dst = NULL;

  	if (err == -ENETUNREACH)
  		IP6_INC_STATS(net, NULL, IPSTATS_MIB_OUTNOROUTES);

  	return err;
  }

  /**
   *	ip6_dst_lookup - perform route lookup on flow
   *	@sk: socket which provides route info
   *	@dst: pointer to dst_entry * for result

   *	@fl6: flow to lookup

   *
   *	This function performs a route lookup on the given flow.
   *
   *	It returns zero on success, or a standard errno code on error.
   */

  int ip6_dst_lookup(struct net *net, struct sock *sk, struct dst_entry **dst,
  		   struct flowi6 *fl6)

  {
  	*dst = NULL;

  	return ip6_dst_lookup_tail(net, sk, dst, fl6);

  }

  EXPORT_SYMBOL_GPL(ip6_dst_lookup);

  /**

   *	ip6_dst_lookup_flow - perform route lookup on flow with ipsec
   *	@sk: socket which provides route info

   *	@fl6: flow to lookup

   *	@final_dst: final destination address for ipsec lookup

   *
   *	This function performs a route lookup on the given flow.
   *
   *	It returns a valid dst pointer on success, or a pointer encoded
   *	error code.
   */

  struct dst_entry *ip6_dst_lookup_flow(const struct sock *sk, struct flowi6 *fl6,

  				      const struct in6_addr *final_dst)

  {
  	struct dst_entry *dst = NULL;
  	int err;

  	err = ip6_dst_lookup_tail(sock_net(sk), sk, &dst, fl6);

  	if (err)
  		return ERR_PTR(err);
  	if (final_dst)

  		fl6->daddr = *final_dst;

  	return xfrm_lookup_route(sock_net(sk), dst, flowi6_to_flowi(fl6), sk, 0);

  }
  EXPORT_SYMBOL_GPL(ip6_dst_lookup_flow);
  
  /**
   *	ip6_sk_dst_lookup_flow - perform socket cached route lookup on flow

   *	@sk: socket which provides the dst cache and route info

   *	@fl6: flow to lookup

   *	@final_dst: final destination address for ipsec lookup

   *
   *	This function performs a route lookup on the given flow with the
   *	possibility of using the cached route in the socket if it is valid.
   *	It will take the socket dst lock when operating on the dst cache.
   *	As a result, this function can only be used in process context.
   *

   *	It returns a valid dst pointer on success, or a pointer encoded
   *	error code.

   */

  struct dst_entry *ip6_sk_dst_lookup_flow(struct sock *sk, struct flowi6 *fl6,

  					 const struct in6_addr *final_dst)

  {

  	struct dst_entry *dst = sk_dst_check(sk, inet6_sk(sk)->dst_cookie);

  	dst = ip6_sk_dst_check(sk, dst, fl6);

  	if (!dst)
  		dst = ip6_dst_lookup_flow(sk, fl6, final_dst);

  	return dst;

  }

  EXPORT_SYMBOL_GPL(ip6_sk_dst_lookup_flow);

  static inline struct ipv6_opt_hdr *ip6_opt_dup(struct ipv6_opt_hdr *src,
  					       gfp_t gfp)
  {
  	return src ? kmemdup(src, (src->hdrlen + 1) * 8, gfp) : NULL;
  }
  
  static inline struct ipv6_rt_hdr *ip6_rthdr_dup(struct ipv6_rt_hdr *src,
  						gfp_t gfp)
  {
  	return src ? kmemdup(src, (src->hdrlen + 1) * 8, gfp) : NULL;
  }

  static void ip6_append_data_mtu(unsigned int *mtu,

  				int *maxfraglen,
  				unsigned int fragheaderlen,
  				struct sk_buff *skb,

  				struct rt6_info *rt,

  				unsigned int orig_mtu)

  {
  	if (!(rt->dst.flags & DST_XFRM_TUNNEL)) {

  		if (!skb) {

  			/* first fragment, reserve header_len */

  			*mtu = orig_mtu - rt->dst.header_len;

  
  		} else {
  			/*
  			 * this fragment is not first, the headers
  			 * space is regarded as data space.
  			 */

  			*mtu = orig_mtu;

  		}
  		*maxfraglen = ((*mtu - fragheaderlen) & ~7)
  			      + fragheaderlen - sizeof(struct frag_hdr);
  	}
  }

  static int ip6_setup_cork(struct sock *sk, struct inet_cork_full *cork,

  			  struct inet6_cork *v6_cork, struct ipcm6_cookie *ipc6,

  			  struct rt6_info *rt, struct flowi6 *fl6)
  {
  	struct ipv6_pinfo *np = inet6_sk(sk);
  	unsigned int mtu;

  	struct ipv6_txoptions *opt = ipc6->opt;

  
  	/*
  	 * setup for corking
  	 */
  	if (opt) {
  		if (WARN_ON(v6_cork->opt))
  			return -EINVAL;

  		v6_cork->opt = kzalloc(sizeof(*opt), sk->sk_allocation);

  		if (unlikely(!v6_cork->opt))

  			return -ENOBUFS;

  		v6_cork->opt->tot_len = sizeof(*opt);

  		v6_cork->opt->opt_flen = opt->opt_flen;
  		v6_cork->opt->opt_nflen = opt->opt_nflen;
  
  		v6_cork->opt->dst0opt = ip6_opt_dup(opt->dst0opt,
  						    sk->sk_allocation);
  		if (opt->dst0opt && !v6_cork->opt->dst0opt)
  			return -ENOBUFS;
  
  		v6_cork->opt->dst1opt = ip6_opt_dup(opt->dst1opt,
  						    sk->sk_allocation);
  		if (opt->dst1opt && !v6_cork->opt->dst1opt)
  			return -ENOBUFS;
  
  		v6_cork->opt->hopopt = ip6_opt_dup(opt->hopopt,
  						   sk->sk_allocation);
  		if (opt->hopopt && !v6_cork->opt->hopopt)
  			return -ENOBUFS;
  
  		v6_cork->opt->srcrt = ip6_rthdr_dup(opt->srcrt,
  						    sk->sk_allocation);
  		if (opt->srcrt && !v6_cork->opt->srcrt)
  			return -ENOBUFS;
  
  		/* need source address above miyazawa*/
  	}
  	dst_hold(&rt->dst);
  	cork->base.dst = &rt->dst;
  	cork->fl.u.ip6 = *fl6;

  	v6_cork->hop_limit = ipc6->hlimit;
  	v6_cork->tclass = ipc6->tclass;

  	if (rt->dst.flags & DST_XFRM_TUNNEL)
  		mtu = np->pmtudisc >= IPV6_PMTUDISC_PROBE ?

  		      READ_ONCE(rt->dst.dev->mtu) : dst_mtu(&rt->dst);

  	else
  		mtu = np->pmtudisc >= IPV6_PMTUDISC_PROBE ?

  		      READ_ONCE(rt->dst.dev->mtu) : dst_mtu(rt->dst.path);

  	if (np->frag_size < mtu) {
  		if (np->frag_size)
  			mtu = np->frag_size;
  	}

  	if (mtu < IPV6_MIN_MTU)
  		return -EINVAL;

  	cork->base.fragsize = mtu;
  	if (dst_allfrag(rt->dst.path))
  		cork->base.flags |= IPCORK_ALLFRAG;
  	cork->base.length = 0;
  
  	return 0;
  }

  static int __ip6_append_data(struct sock *sk,
  			     struct flowi6 *fl6,
  			     struct sk_buff_head *queue,
  			     struct inet_cork *cork,
  			     struct inet6_cork *v6_cork,
  			     struct page_frag *pfrag,
  			     int getfrag(void *from, char *to, int offset,
  					 int len, int odd, struct sk_buff *skb),
  			     void *from, int length, int transhdrlen,

  			     unsigned int flags, struct ipcm6_cookie *ipc6,

  			     const struct sockcm_cookie *sockc)

  {

  	struct sk_buff *skb, *skb_prev = NULL;

  	unsigned int maxfraglen, fragheaderlen, mtu, orig_mtu, pmtu;

  	int exthdrlen = 0;
  	int dst_exthdrlen = 0;

  	int hh_len;

  	int copy;
  	int err;
  	int offset = 0;

  	__u8 tx_flags = 0;

  	u32 tskey = 0;

  	struct rt6_info *rt = (struct rt6_info *)cork->dst;
  	struct ipv6_txoptions *opt = v6_cork->opt;

  	int csummode = CHECKSUM_NONE;

  	unsigned int maxnonfragsize, headersize;

  	skb = skb_peek_tail(queue);
  	if (!skb) {
  		exthdrlen = opt ? opt->opt_flen : 0;

  		dst_exthdrlen = rt->dst.header_len - rt->rt6i_nfheader_len;

  	}

  	mtu = cork->fragsize;

  	orig_mtu = mtu;

  	hh_len = LL_RESERVED_SPACE(rt->dst.dev);

  	fragheaderlen = sizeof(struct ipv6hdr) + rt->rt6i_nfheader_len +

  			(opt ? opt->opt_nflen : 0);

  	maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen -
  		     sizeof(struct frag_hdr);

  	headersize = sizeof(struct ipv6hdr) +
  		     (opt ? opt->opt_flen + opt->opt_nflen : 0) +
  		     (dst_allfrag(&rt->dst) ?
  		      sizeof(struct frag_hdr) : 0) +
  		     rt->rt6i_nfheader_len;

  	/* as per RFC 7112 section 5, the entire IPv6 Header Chain must fit
  	 * the first fragment
  	 */
  	if (headersize + transhdrlen > mtu)
  		goto emsgsize;

  	if (cork->length + length > mtu - headersize && ipc6->dontfrag &&

  	    (sk->sk_protocol == IPPROTO_UDP ||
  	     sk->sk_protocol == IPPROTO_RAW)) {
  		ipv6_local_rxpmtu(sk, fl6, mtu - headersize +
  				sizeof(struct ipv6hdr));
  		goto emsgsize;
  	}

  	if (ip6_sk_ignore_df(sk))
  		maxnonfragsize = sizeof(struct ipv6hdr) + IPV6_MAXPLEN;
  	else
  		maxnonfragsize = mtu;

  	if (cork->length + length > maxnonfragsize - headersize) {

  emsgsize:

  		pmtu = max_t(int, mtu - headersize + sizeof(struct ipv6hdr), 0);
  		ipv6_local_error(sk, EMSGSIZE, fl6, pmtu);

  		return -EMSGSIZE;

  	}

  	/* CHECKSUM_PARTIAL only with no extension headers and when
  	 * we are not going to fragment
  	 */
  	if (transhdrlen && sk->sk_protocol == IPPROTO_UDP &&
  	    headersize == sizeof(struct ipv6hdr) &&

  	    length <= mtu - headersize &&

  	    !(flags & MSG_MORE) &&

  	    rt->dst.dev->features & (NETIF_F_IPV6_CSUM | NETIF_F_HW_CSUM))

  		csummode = CHECKSUM_PARTIAL;

  	if (sk->sk_type == SOCK_DGRAM || sk->sk_type == SOCK_RAW) {

  		sock_tx_timestamp(sk, sockc->tsflags, &tx_flags);

  		if (tx_flags & SKBTX_ANY_SW_TSTAMP &&
  		    sk->sk_tsflags & SOF_TIMESTAMPING_OPT_ID)
  			tskey = sk->sk_tskey++;
  	}

  	/*
  	 * Let's try using as much space as possible.
  	 * Use MTU if total length of the message fits into the MTU.
  	 * Otherwise, we need to reserve fragment header and
  	 * fragment alignment (= 8-15 octects, in total).
  	 *
  	 * Note that we may need to "move" the data from the tail of

  	 * of the buffer to the new fragment when we split

  	 * the message.
  	 *

  	 * FIXME: It may be fragmented into multiple chunks

  	 *        at once if non-fragmentable extension headers
  	 *        are too large.

  	 * --yoshfuji

  	 */

  	cork->length += length;

  	if (!skb)

  		goto alloc_new_skb;
  
  	while (length > 0) {
  		/* Check if the remaining data fits into current packet. */

  		copy = (cork->length <= mtu && !(cork->flags & IPCORK_ALLFRAG) ? mtu : maxfraglen) - skb->len;

  		if (copy < length)
  			copy = maxfraglen - skb->len;
  
  		if (copy <= 0) {
  			char *data;
  			unsigned int datalen;
  			unsigned int fraglen;
  			unsigned int fraggap;
  			unsigned int alloclen;

  alloc_new_skb:

  			/* There's no room in the current skb */

  			if (skb)
  				fraggap = skb->len - maxfraglen;

  			else
  				fraggap = 0;

  			/* update mtu and maxfraglen if necessary */

  			if (!skb || !skb_prev)

  				ip6_append_data_mtu(&mtu, &maxfraglen,

  						    fragheaderlen, skb, rt,

  						    orig_mtu);

  
  			skb_prev = skb;

  
  			/*
  			 * If remaining data exceeds the mtu,
  			 * we know we need more fragment(s).
  			 */
  			datalen = length + fraggap;

  			if (datalen > (cork->length <= mtu && !(cork->flags & IPCORK_ALLFRAG) ? mtu : maxfraglen) - fragheaderlen)
  				datalen = maxfraglen - fragheaderlen - rt->dst.trailer_len;

  			if ((flags & MSG_MORE) &&

  			    !(rt->dst.dev->features&NETIF_F_SG))

  				alloclen = mtu;
  			else
  				alloclen = datalen + fragheaderlen;

  			alloclen += dst_exthdrlen;

  			if (datalen != length + fraggap) {
  				/*
  				 * this is not the last fragment, the trailer
  				 * space is regarded as data space.
  				 */
  				datalen += rt->dst.trailer_len;
  			}
  
  			alloclen += rt->dst.trailer_len;
  			fraglen = datalen + fragheaderlen;

  
  			/*
  			 * We just reserve space for fragment header.

  			 * Note: this may be overallocation if the message

  			 * (without MSG_MORE) fits into the MTU.
  			 */
  			alloclen += sizeof(struct frag_hdr);

  			copy = datalen - transhdrlen - fraggap;
  			if (copy < 0) {
  				err = -EINVAL;
  				goto error;
  			}

  			if (transhdrlen) {
  				skb = sock_alloc_send_skb(sk,
  						alloclen + hh_len,
  						(flags & MSG_DONTWAIT), &err);
  			} else {
  				skb = NULL;

  				if (refcount_read(&sk->sk_wmem_alloc) <=

  				    2 * sk->sk_sndbuf)
  					skb = sock_wmalloc(sk,
  							   alloclen + hh_len, 1,
  							   sk->sk_allocation);

  				if (unlikely(!skb))

  					err = -ENOBUFS;
  			}

  			if (!skb)

  				goto error;
  			/*
  			 *	Fill in the control structures
  			 */

  			skb->protocol = htons(ETH_P_IPV6);

  			skb->ip_summed = csummode;

  			skb->csum = 0;

  			/* reserve for fragmentation and ipsec header */
  			skb_reserve(skb, hh_len + sizeof(struct frag_hdr) +
  				    dst_exthdrlen);

  			/* Only the initial fragment is time stamped */
  			skb_shinfo(skb)->tx_flags = tx_flags;
  			tx_flags = 0;

  			skb_shinfo(skb)->tskey = tskey;
  			tskey = 0;

  			/*
  			 *	Find where to start putting bytes
  			 */

  			data = skb_put(skb, fraglen);
  			skb_set_network_header(skb, exthdrlen);
  			data += fragheaderlen;

  			skb->transport_header = (skb->network_header +
  						 fragheaderlen);

  			if (fraggap) {
  				skb->csum = skb_copy_and_csum_bits(
  					skb_prev, maxfraglen,
  					data + transhdrlen, fraggap, 0);
  				skb_prev->csum = csum_sub(skb_prev->csum,
  							  skb->csum);
  				data += fraggap;

  				pskb_trim_unique(skb_prev, maxfraglen);

  			}

  			if (copy > 0 &&
  			    getfrag(from, data + transhdrlen, offset,
  				    copy, fraggap, skb) < 0) {

  				err = -EFAULT;
  				kfree_skb(skb);
  				goto error;
  			}
  
  			offset += copy;
  			length -= datalen - fraggap;
  			transhdrlen = 0;
  			exthdrlen = 0;

  			dst_exthdrlen = 0;

  			if ((flags & MSG_CONFIRM) && !skb_prev)
  				skb_set_dst_pending_confirm(skb, 1);

  			/*
  			 * Put the packet on the pending queue
  			 */

  			__skb_queue_tail(queue, skb);

  			continue;
  		}
  
  		if (copy > length)
  			copy = length;

  		if (!(rt->dst.dev->features&NETIF_F_SG) &&
  		    skb_tailroom(skb) >= copy) {

  			unsigned int off;
  
  			off = skb->len;
  			if (getfrag(from, skb_put(skb, copy),
  						offset, copy, off, skb) < 0) {
  				__skb_trim(skb, off);
  				err = -EFAULT;
  				goto error;
  			}
  		} else {
  			int i = skb_shinfo(skb)->nr_frags;

  			err = -ENOMEM;
  			if (!sk_page_frag_refill(sk, pfrag))

  				goto error;

  
  			if (!skb_can_coalesce(skb, i, pfrag->page,
  					      pfrag->offset)) {
  				err = -EMSGSIZE;
  				if (i == MAX_SKB_FRAGS)
  					goto error;
  
  				__skb_fill_page_desc(skb, i, pfrag->page,
  						     pfrag->offset, 0);
  				skb_shinfo(skb)->nr_frags = ++i;
  				get_page(pfrag->page);

  			}

  			copy = min_t(int, copy, pfrag->size - pfrag->offset);

  			if (getfrag(from,

  				    page_address(pfrag->page) + pfrag->offset,
  				    offset, copy, skb->len, skb) < 0)
  				goto error_efault;
  
  			pfrag->offset += copy;
  			skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);

  			skb->len += copy;
  			skb->data_len += copy;

  			skb->truesize += copy;

  			refcount_add(copy, &sk->sk_wmem_alloc);

  		}
  		offset += copy;
  		length -= copy;
  	}

  	return 0;

  
  error_efault:
  	err = -EFAULT;

  error: