/*
   *	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/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>

  int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *));

  int __ip6_local_out(struct sk_buff *skb)
  {
  	int len;
  
  	len = skb->len - sizeof(struct ipv6hdr);
  	if (len > IPV6_MAXPLEN)
  		len = 0;
  	ipv6_hdr(skb)->payload_len = htons(len);

  	return nf_hook(NFPROTO_IPV6, NF_INET_LOCAL_OUT, skb, NULL,
  		       skb_dst(skb)->dev, dst_output);

  }
  
  int ip6_local_out(struct sk_buff *skb)
  {
  	int err;
  
  	err = __ip6_local_out(skb);
  	if (likely(err == 1))
  		err = dst_output(skb);
  
  	return err;
  }
  EXPORT_SYMBOL_GPL(ip6_local_out);

  /* dev_loopback_xmit for use with netfilter. */
  static int ip6_dev_loopback_xmit(struct sk_buff *newskb)
  {

  	skb_reset_mac_header(newskb);

  	__skb_pull(newskb, skb_network_offset(newskb));

  	newskb->pkt_type = PACKET_LOOPBACK;
  	newskb->ip_summed = CHECKSUM_UNNECESSARY;

  	WARN_ON(!skb_dst(newskb));

  	netif_rx_ni(newskb);

  	return 0;
  }

  static int ip6_finish_output2(struct sk_buff *skb)

  {

  	struct dst_entry *dst = skb_dst(skb);

  	struct net_device *dev = dst->dev;

  	struct neighbour *neigh;

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

  	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(skb->sk) &&

  		    ((mroute6_socket(dev_net(dev), 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,
  					newskb, NULL, newskb->dev,

  					ip6_dev_loopback_xmit);

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

  				IP6_INC_STATS(dev_net(dev), idev,
  					      IPSTATS_MIB_OUTDISCARDS);

  				kfree_skb(skb);
  				return 0;
  			}
  		}

  		IP6_UPD_PO_STATS(dev_net(dev), idev, IPSTATS_MIB_OUTMCAST,
  				skb->len);

  	}

  	rcu_read_lock();

  	neigh = dst_get_neighbour_noref(dst);

  	if (neigh) {
  		int res = neigh_output(neigh, skb);

  		rcu_read_unlock();
  		return res;
  	}
  	rcu_read_unlock();

  	IP6_INC_STATS_BH(dev_net(dst->dev),
  			 ip6_dst_idev(dst), IPSTATS_MIB_OUTNOROUTES);
  	kfree_skb(skb);
  	return -EINVAL;

  }

  static int ip6_finish_output(struct sk_buff *skb)
  {
  	if ((skb->len > ip6_skb_dst_mtu(skb) && !skb_is_gso(skb)) ||
  	    dst_allfrag(skb_dst(skb)))
  		return ip6_fragment(skb, ip6_finish_output2);
  	else
  		return ip6_finish_output2(skb);
  }

  int ip6_output(struct sk_buff *skb)
  {

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

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

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

  		IP6_INC_STATS(dev_net(dev), idev,

  			      IPSTATS_MIB_OUTDISCARDS);

  		kfree_skb(skb);
  		return 0;
  	}

  	return NF_HOOK_COND(NFPROTO_IPV6, NF_INET_POST_ROUTING, skb, NULL, dev,
  			    ip6_finish_output,
  			    !(IP6CB(skb)->flags & IP6SKB_REROUTED));

  }

  /*

   *	xmit an sk_buff (used by TCP, SCTP and DCCP)

   */

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

  	     struct ipv6_txoptions *opt, int tclass)

  {

  	struct net *net = sock_net(sk);

  	struct ipv6_pinfo *np = inet6_sk(sk);

  	struct in6_addr *first_hop = &fl6->daddr;

  	struct dst_entry *dst = skb_dst(skb);

  	struct ipv6hdr *hdr;

  	u8  proto = fl6->flowi6_proto;

  	int seg_len = skb->len;

  	int hlimit = -1;

  	u32 mtu;
  
  	if (opt) {

  		unsigned int head_room;

  
  		/* First: exthdrs may take lots of space (~8K for now)
  		   MAX_HEADER is not enough.
  		 */
  		head_room = opt->opt_nflen + opt->opt_flen;
  		seg_len += head_room;
  		head_room += sizeof(struct ipv6hdr) + LL_RESERVED_SPACE(dst->dev);
  
  		if (skb_headroom(skb) < head_room) {
  			struct sk_buff *skb2 = skb_realloc_headroom(skb, head_room);

  			if (skb2 == NULL) {

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

  					      IPSTATS_MIB_OUTDISCARDS);
  				kfree_skb(skb);

  				return -ENOBUFS;
  			}

  			kfree_skb(skb);
  			skb = skb2;

  			skb_set_owner_w(skb, sk);

  		}
  		if (opt->opt_flen)
  			ipv6_push_frag_opts(skb, opt, &proto);
  		if (opt->opt_nflen)
  			ipv6_push_nfrag_opts(skb, opt, &proto, &first_hop);
  	}

  	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);

  	*(__be32 *)hdr = htonl(0x60000000 | (tclass << 20)) | fl6->flowlabel;

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

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

  	skb->priority = sk->sk_priority;

  	skb->mark = sk->sk_mark;

  	mtu = dst_mtu(dst);

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

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

  			      IPSTATS_MIB_OUT, skb->len);

  		return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT, skb, NULL,
  			       dst->dev, dst_output);

  	}
  
  	if (net_ratelimit())
  		printk(KERN_DEBUG "IPv6: sending pkt_too_big to self
  ");
  	skb->dev = dst->dev;

  	icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);

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

  	kfree_skb(skb);
  	return -EMSGSIZE;
  }

  EXPORT_SYMBOL(ip6_xmit);

  /*
   *	To avoid extra problems ND packets are send through this
   *	routine. It's code duplication but I really want to avoid
   *	extra checks since ipv6_build_header is used by TCP (which
   *	is for us performance critical)
   */
  
  int ip6_nd_hdr(struct sock *sk, struct sk_buff *skb, struct net_device *dev,

  	       const struct in6_addr *saddr, const struct in6_addr *daddr,

  	       int proto, int len)
  {
  	struct ipv6_pinfo *np = inet6_sk(sk);
  	struct ipv6hdr *hdr;

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

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

  	hdr = ipv6_hdr(skb);

  	*(__be32*)hdr = htonl(0x60000000);

  
  	hdr->payload_len = htons(len);
  	hdr->nexthdr = proto;
  	hdr->hop_limit = np->hop_limit;

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

  
  	return 0;
  }
  
  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 sk_buff *skb)
  {
  	return dst_output(skb);
  }
  
  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);

  	struct neighbour *n;

  	u32 mtu;

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

  		goto error;

  	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;
  	}

  	if (skb->pkt_type != PACKET_HOST)
  		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 (opt->ra) {

  		u8 *ptr = skb_network_header(skb) + opt->ra;

  		if (ip6_call_ra_chain(skb, (ptr[2]<<8) + ptr[3]))
  			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_BH(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.

  	 */

  	n = dst_get_neighbour_noref(dst);

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

  		struct in6_addr *target = NULL;
  		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 = (struct in6_addr*)&n->primary_key;
  		else
  			target = &hdr->daddr;

  		if (!rt->rt6i_peer)
  			rt6_bind_peer(rt, 1);

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

  		if (inet_peer_xrlim_allow(rt->rt6i_peer, 1*HZ))

  			ndisc_send_redirect(skb, n, target);

  	} 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 = dst_mtu(dst);
  	if (mtu < IPV6_MIN_MTU)
  		mtu = IPV6_MIN_MTU;

  	if (skb->len > mtu && !skb_is_gso(skb)) {

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

  		icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);

  		IP6_INC_STATS_BH(net,
  				 ip6_dst_idev(dst), IPSTATS_MIB_INTOOBIGERRORS);
  		IP6_INC_STATS_BH(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--;

  	IP6_INC_STATS_BH(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTFORWDATAGRAMS);

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

  		       ip6_forward_finish);

  
  error:

  	IP6_INC_STATS_BH(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;

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

  	nf_copy(to, from);

  #if defined(CONFIG_NETFILTER_XT_TARGET_TRACE) || \
      defined(CONFIG_NETFILTER_XT_TARGET_TRACE_MODULE)
  	to->nf_trace = from->nf_trace;
  #endif

  	skb_copy_secmark(to, from);

  }
  
  int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr)
  {
  	u16 offset = sizeof(struct ipv6hdr);

  	struct ipv6_opt_hdr *exthdr =
  				(struct ipv6_opt_hdr *)(ipv6_hdr(skb) + 1);

  	unsigned int packet_len = skb->tail - skb->network_header;

  	int found_rhdr = 0;

  	*nexthdr = &ipv6_hdr(skb)->nexthdr;

  
  	while (offset + 1 <= packet_len) {
  
  		switch (**nexthdr) {
  
  		case NEXTHDR_HOP:

  			break;

  		case NEXTHDR_ROUTING:

  			found_rhdr = 1;
  			break;

  		case NEXTHDR_DEST:

  #if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)

  			if (ipv6_find_tlv(skb, offset, IPV6_TLV_HAO) >= 0)
  				break;
  #endif
  			if (found_rhdr)
  				return offset;

  			break;
  		default :
  			return offset;
  		}

  
  		offset += ipv6_optlen(exthdr);
  		*nexthdr = &exthdr->nexthdr;

  		exthdr = (struct ipv6_opt_hdr *)(skb_network_header(skb) +
  						 offset);

  	}
  
  	return offset;
  }

  void ipv6_select_ident(struct frag_hdr *fhdr, struct rt6_info *rt)
  {
  	static atomic_t ipv6_fragmentation_id;
  	int old, new;

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

  		struct inet_peer *peer;
  
  		if (!rt->rt6i_peer)
  			rt6_bind_peer(rt, 1);
  		peer = rt->rt6i_peer;
  		if (peer) {
  			fhdr->identification = htonl(inet_getid(peer, 0));
  			return;
  		}
  	}
  	do {
  		old = atomic_read(&ipv6_fragmentation_id);
  		new = old + 1;
  		if (!new)
  			new = 1;
  	} while (atomic_cmpxchg(&ipv6_fragmentation_id, old, new) != old);
  	fhdr->identification = htonl(new);
  }

  int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))

  {

  	struct sk_buff *frag;

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

  	struct ipv6_pinfo *np = skb->sk ? 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 = 0;

  	int ptr, offset = 0, err=0;
  	u8 *prevhdr, nexthdr = 0;

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

  	hlen = ip6_find_1stfragopt(skb, &prevhdr);
  	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 (!skb->local_df && skb->len > mtu) {

  		skb->dev = skb_dst(skb)->dev;

  		icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);

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

  			      IPSTATS_MIB_FRAGFAILS);

  		kfree_skb(skb);
  		return -EMSGSIZE;
  	}

  	if (np && np->frag_size < mtu) {
  		if (np->frag_size)
  			mtu = np->frag_size;
  	}
  	mtu -= hlen + sizeof(struct frag_hdr);

  	if (skb_has_frag_list(skb)) {

  		int first_len = skb_pagelen(skb);

  		struct sk_buff *frag2;

  
  		if (first_len - hlen > mtu ||
  		    ((first_len - hlen) & 7) ||
  		    skb_cloned(skb))
  			goto slow_path;

  		skb_walk_frags(skb, frag) {

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

  				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;
  		frag = skb_shinfo(skb)->frag_list;

  		skb_frag_list_init(skb);

  		/* BUILD HEADER */

  		*prevhdr = NEXTHDR_FRAGMENT;

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

  		if (!tmp_hdr) {

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

  				      IPSTATS_MIB_FRAGFAILS);

  			return -ENOMEM;
  		}

  		__skb_pull(skb, hlen);
  		fh = (struct frag_hdr*)__skb_push(skb, sizeof(struct frag_hdr));

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

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

  		ipv6_select_ident(fh, rt);

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

  		dst_hold(&rt->dst);

  
  		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 = (struct frag_hdr*)__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 != NULL)
  					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(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);

  			dst_release(&rt->dst);

  			return 0;
  		}
  
  		while (frag) {
  			skb = frag->next;
  			kfree_skb(frag);
  			frag = skb;
  		}

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

  			      IPSTATS_MIB_FRAGFAILS);

  		dst_release(&rt->dst);

  		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.
  	 */
  
  	*prevhdr = NEXTHDR_FRAGMENT;

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

  
  	/*
  	 *	Keep copying data until we run out.
  	 */
  	while(left > 0)	{
  		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.
  		 */

  		if ((frag = alloc_skb(len + hlen + sizeof(struct frag_hdr) +
  				      hroom + troom, GFP_ATOMIC)) == NULL) {

  			NETDEBUG(KERN_INFO "IPv6: frag: no memory for new fragment!
  ");

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

  				      IPSTATS_MIB_FRAGFAILS);

  			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);

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

  		if (!frag_id) {

  			ipv6_select_ident(fh, rt);

  			frag_id = fh->identification;
  		} else
  			fh->identification = frag_id;
  
  		/*
  		 *	Copy a block of the IP datagram.
  		 */

  		if (skb_copy_bits(skb, ptr, skb_transport_header(frag), len))

  			BUG();
  		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(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);

  	kfree_skb(skb);

  	return err;
  
  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 == NULL || !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 = (struct rt6_info *)dst;

  	if (!dst)
  		goto out;
  
  	/* 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_oif && fl6->flowi6_oif != dst->dev->ifindex)) {

  		dst_release(dst);
  		dst = NULL;

  	}

  out:
  	return dst;
  }
  
  static int ip6_dst_lookup_tail(struct sock *sk,

  			       struct dst_entry **dst, struct flowi6 *fl6)

  {

  	struct net *net = sock_net(sk);

  #ifdef CONFIG_IPV6_OPTIMISTIC_DAD
  	struct neighbour *n;
  #endif
  	int err;

  	if (*dst == NULL)

  		*dst = ip6_route_output(net, sk, fl6);

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

  	if (ipv6_addr_any(&fl6->saddr)) {

  		struct rt6_info *rt = (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;

  	}

  #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
  	 */

  	rcu_read_lock();

  	n = dst_get_neighbour_noref(*dst);

  	if (n && !(n->nud_state & NUD_VALID)) {

  		struct inet6_ifaddr *ifp;

  		struct flowi6 fl_gw6;

  		int redirect;

  		rcu_read_unlock();

  		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);

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

  		}

  	} else {
  		rcu_read_unlock();

  	}

  #endif

  	return 0;
  
  out_err_release:

  	if (err == -ENETUNREACH)

  		IP6_INC_STATS_BH(net, NULL, IPSTATS_MIB_OUTNOROUTES);

  	dst_release(*dst);
  	*dst = NULL;
  	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 sock *sk, struct dst_entry **dst, struct flowi6 *fl6)

  {
  	*dst = NULL;

  	return ip6_dst_lookup_tail(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

   *	@can_sleep: we are in a sleepable context

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

  				      const struct in6_addr *final_dst,

  				      bool can_sleep)

  {
  	struct dst_entry *dst = NULL;
  	int err;

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

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

  		fl6->daddr = *final_dst;

  	if (can_sleep)

  		fl6->flowi6_flags |= FLOWI_FLAG_CAN_SLEEP;

  	return xfrm_lookup(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

   *	@can_sleep: we are in a sleepable context

   *
   *	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,

  					 bool can_sleep)

  {

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

  	dst = ip6_sk_dst_check(sk, dst, fl6);

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

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

  		fl6->daddr = *final_dst;

  	if (can_sleep)

  		fl6->flowi6_flags |= FLOWI_FLAG_CAN_SLEEP;

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

  }

  EXPORT_SYMBOL_GPL(ip6_sk_dst_lookup_flow);

  static inline int ip6_ufo_append_data(struct sock *sk,

  			int getfrag(void *from, char *to, int offset, int len,
  			int odd, struct sk_buff *skb),
  			void *from, int length, int hh_len, int fragheaderlen,

  			int transhdrlen, int mtu,unsigned int flags,
  			struct rt6_info *rt)

  
  {
  	struct sk_buff *skb;
  	int err;
  
  	/* There is support for UDP large send offload by network
  	 * device, so create one single skb packet containing complete
  	 * udp datagram
  	 */
  	if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL) {
  		skb = sock_alloc_send_skb(sk,
  			hh_len + fragheaderlen + transhdrlen + 20,
  			(flags & MSG_DONTWAIT), &err);
  		if (skb == NULL)

  			return err;

  
  		/* reserve space for Hardware header */
  		skb_reserve(skb, hh_len);
  
  		/* create space for UDP/IP header */
  		skb_put(skb,fragheaderlen + transhdrlen);
  
  		/* initialize network header pointer */

  		skb_reset_network_header(skb);

  
  		/* initialize protocol header pointer */

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

  		skb->ip_summed = CHECKSUM_PARTIAL;

  		skb->csum = 0;

  	}
  
  	err = skb_append_datato_frags(sk,skb, getfrag, from,
  				      (length - transhdrlen));
  	if (!err) {
  		struct frag_hdr fhdr;

  		/* Specify the length of each IPv6 datagram fragment.
  		 * It has to be a multiple of 8.
  		 */
  		skb_shinfo(skb)->gso_size = (mtu - fragheaderlen -
  					     sizeof(struct frag_hdr)) & ~7;

  		skb_shinfo(skb)->gso_type = SKB_GSO_UDP;

  		ipv6_select_ident(&fhdr, rt);

  		skb_shinfo(skb)->ip6_frag_id = fhdr.identification;
  		__skb_queue_tail(&sk->sk_write_queue, skb);
  
  		return 0;
  	}
  	/* There is not enough support do UPD LSO,
  	 * so follow normal path
  	 */
  	kfree_skb(skb);
  
  	return err;
  }

  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;
  }

  int ip6_append_data(struct sock *sk, int getfrag(void *from, char *to,
  	int offset, int len, int odd, struct sk_buff *skb),
  	void *from, int length, int transhdrlen,

  	int hlimit, int tclass, struct ipv6_txoptions *opt, struct flowi6 *fl6,

  	struct rt6_info *rt, unsigned int flags, int dontfrag)

  {
  	struct inet_sock *inet = inet_sk(sk);
  	struct ipv6_pinfo *np = inet6_sk(sk);

  	struct inet_cork *cork;

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

  	int dst_exthdrlen;

  	int hh_len;
  	int mtu;
  	int copy;
  	int err;
  	int offset = 0;
  	int csummode = CHECKSUM_NONE;

  	__u8 tx_flags = 0;

  
  	if (flags&MSG_PROBE)
  		return 0;

  	cork = &inet->cork.base;

  	if (skb_queue_empty(&sk->sk_write_queue)) {
  		/*
  		 * setup for corking
  		 */
  		if (opt) {

  			if (WARN_ON(np->cork.opt))

  				return -EINVAL;

  
  			np->cork.opt = kmalloc(opt->tot_len, sk->sk_allocation);
  			if (unlikely(np->cork.opt == NULL))
  				return -ENOBUFS;
  
  			np->cork.opt->tot_len = opt->tot_len;
  			np->cork.opt->opt_flen = opt->opt_flen;
  			np->cork.opt->opt_nflen = opt->opt_nflen;
  
  			np->cork.opt->dst0opt = ip6_opt_dup(opt->dst0opt,
  							    sk->sk_allocation);
  			if (opt->dst0opt && !np->cork.opt->dst0opt)
  				return -ENOBUFS;
  
  			np->cork.opt->dst1opt = ip6_opt_dup(opt->dst1opt,
  							    sk->sk_allocation);
  			if (opt->dst1opt && !np->cork.opt->dst1opt)
  				return -ENOBUFS;
  
  			np->cork.opt->hopopt = ip6_opt_dup(opt->hopopt,
  							   sk->sk_allocation);
  			if (opt->hopopt && !np->cork.opt->hopopt)
  				return -ENOBUFS;
  
  			np->cork.opt->srcrt = ip6_rthdr_dup(opt->srcrt,
  							    sk->sk_allocation);
  			if (opt->srcrt && !np->cork.opt->srcrt)
  				return -ENOBUFS;

  			/* need source address above miyazawa*/
  		}

  		dst_hold(&rt->dst);

  		cork->dst = &rt->dst;

  		inet->cork.fl.u.ip6 = *fl6;

  		np->cork.hop_limit = hlimit;

  		np->cork.tclass = tclass;

  		mtu = np->pmtudisc == IPV6_PMTUDISC_PROBE ?

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

  		if (np->frag_size < mtu) {

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

  		cork->fragsize = mtu;

  		if (dst_allfrag(rt->dst.path))

  			cork->flags |= IPCORK_ALLFRAG;
  		cork->length = 0;

  		sk->sk_sndmsg_page = NULL;
  		sk->sk_sndmsg_off = 0;

  		exthdrlen = (opt ? opt->opt_flen : 0) - rt->rt6i_nfheader_len;

  		length += exthdrlen;
  		transhdrlen += exthdrlen;

  		dst_exthdrlen = rt->dst.header_len;

  	} else {

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

  		fl6 = &inet->cork.fl.u.ip6;

  		opt = np->cork.opt;

  		transhdrlen = 0;
  		exthdrlen = 0;

  		dst_exthdrlen = 0;

  		mtu = cork->fragsize;

  	}

  	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);
  
  	if (mtu <= sizeof(struct ipv6hdr) + IPV6_MAXPLEN) {

  		if (cork->length + length > sizeof(struct ipv6hdr) + IPV6_MAXPLEN - fragheaderlen) {

  			ipv6_local_error(sk, EMSGSIZE, fl6, mtu-exthdrlen);

  			return -EMSGSIZE;
  		}
  	}

  	/* For UDP, check if TX timestamp is enabled */
  	if (sk->sk_type == SOCK_DGRAM) {
  		err = sock_tx_timestamp(sk, &tx_flags);
  		if (err)
  			goto error;
  	}

  	/*
  	 * 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 (length > mtu) {
  		int proto = sk->sk_protocol;
  		if (dontfrag && (proto == IPPROTO_UDP || proto == IPPROTO_RAW)){

  			ipv6_local_rxpmtu(sk, fl6, mtu-exthdrlen);

  			return -EMSGSIZE;
  		}

  		if (proto == IPPROTO_UDP &&

  		    (rt->dst.dev->features & NETIF_F_UFO)) {

  
  			err = ip6_ufo_append_data(sk, getfrag, from, length,
  						  hh_len, fragheaderlen,

  						  transhdrlen, mtu, flags, rt);

  			if (err)
  				goto error;
  			return 0;
  		}

  	}

  
  	if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
  		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;
  			struct sk_buff *skb_prev;
  alloc_new_skb:
  			skb_prev = skb;
  
  			/* There's no room in the current skb */
  			if (skb_prev)
  				fraggap = skb_prev->len - maxfraglen;
  			else
  				fraggap = 0;
  
  			/*
  			 * 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;
  
  			fraglen = datalen + fragheaderlen;
  			if ((flags & MSG_MORE) &&

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

  				alloclen = mtu;
  			else
  				alloclen = datalen + fragheaderlen;

  			alloclen += dst_exthdrlen;

  			/*
  			 * The last fragment gets additional space at tail.
  			 * Note: we overallocate on fragments with MSG_MODE
  			 * because we have no idea if we're the last one.
  			 */
  			if (datalen == length + fraggap)

  				alloclen += rt->dst.trailer_len;

  
  			/*
  			 * 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);
  
  			if (transhdrlen) {
  				skb = sock_alloc_send_skb(sk,
  						alloclen + hh_len,
  						(flags & MSG_DONTWAIT), &err);
  			} else {
  				skb = NULL;
  				if (atomic_read(&sk->sk_wmem_alloc) <=
  				    2 * sk->sk_sndbuf)
  					skb = sock_wmalloc(sk,
  							   alloclen + hh_len, 1,
  							   sk->sk_allocation);
  				if (unlikely(skb == NULL))
  					err = -ENOBUFS;

  				else {
  					/* Only the initial fragment
  					 * is time stamped.
  					 */
  					tx_flags = 0;
  				}

  			}
  			if (skb == NULL)
  				goto error;
  			/*
  			 *	Fill in the control structures
  			 */
  			skb->ip_summed = csummode;
  			skb->csum = 0;
  			/* reserve for fragmentation */
  			skb_reserve(skb, hh_len+sizeof(struct frag_hdr));

  			if (sk->sk_type == SOCK_DGRAM)
  				skb_shinfo(skb)->tx_flags = tx_flags;

  			/*
  			 *	Find where to start putting bytes
  			 */

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

  			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);

  			}
  			copy = datalen - transhdrlen - fraggap;

  			if (copy < 0) {
  				err = -EINVAL;
  				kfree_skb(skb);
  				goto error;
  			} else 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;

  			csummode = CHECKSUM_NONE;
  
  			/*
  			 * Put the packet on the pending queue
  			 */
  			__skb_queue_tail(&sk->sk_write_queue, skb);
  			continue;
  		}
  
  		if (copy > length)
  			copy = length;

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

  			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;
  			skb_frag_t *frag = &skb_shinfo(skb)->frags[i-1];
  			struct page *page = sk->sk_sndmsg_page;
  			int off = sk->sk_sndmsg_off;
  			unsigned int left;
  
  			if (page && (left = PAGE_SIZE - off) > 0) {
  				if (copy >= left)
  					copy = left;

  				if (page != skb_frag_page(frag)) {

  					if (i == MAX_SKB_FRAGS) {
  						err = -EMSGSIZE;
  						goto error;
  					}

  					skb_fill_page_desc(skb, i, page, sk->sk_sndmsg_off, 0);

  					skb_frag_ref(skb, i);

  					frag = &skb_shinfo(skb)->frags[i];
  				}
  			} else if(i < MAX_SKB_FRAGS) {
  				if (copy > PAGE_SIZE)
  					copy = PAGE_SIZE;
  				page = alloc_pages(sk->sk_allocation, 0);
  				if (page == NULL) {
  					err = -ENOMEM;
  					goto error;
  				}
  				sk->sk_sndmsg_page = page;
  				sk->sk_sndmsg_off = 0;
  
  				skb_fill_page_desc(skb, i, page, 0, 0);
  				frag = &skb_shinfo(skb)->frags[i];

  			} else {
  				err = -EMSGSIZE;
  				goto error;
  			}

  			if (getfrag(from,
  				    skb_frag_address(frag) + skb_frag_size(frag),

  				    offset, copy, skb->len, skb) < 0) {

  				err = -EFAULT;
  				goto error;
  			}
  			sk->sk_sndmsg_off += copy;

  			skb_frag_size_add(frag, copy);

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

  			skb->truesize += copy;
  			atomic_add(copy, &sk->sk_wmem_alloc);

  		}
  		offset += copy;
  		length -= copy;
  	}
  	return 0;
  error:

  	cork->length -= length;

  	IP6_INC_STATS(sock_net(sk), rt->rt6i_idev, IPSTATS_MIB_OUTDISCARDS);

  	return err;
  }

  static void ip6_cork_release(struct inet_sock *inet, struct ipv6_pinfo *np)
  {

  	if (np->cork.opt) {
  		kfree(np->cork.opt->dst0opt);
  		kfree(np->cork.opt->dst1opt);
  		kfree(np->cork.opt->hopopt);
  		kfree(np->cork.opt->srcrt);
  		kfree(np->cork.opt);
  		np->cork.opt = NULL;
  	}

  	if (inet->cork.base.dst) {
  		dst_release(inet->cork.base.dst);
  		inet->cork.base.dst = NULL;
  		inet->cork.base.flags &= ~IPCORK_ALLFRAG;

  	}
  	memset(&inet->cork.fl, 0, sizeof(inet->cork.fl));
  }

  int ip6_push_pending_frames(struct sock *sk)
  {
  	struct sk_buff *skb, *tmp_skb;
  	struct sk_buff **tail_skb;
  	struct in6_addr final_dst_buf, *final_dst = &final_dst_buf;
  	struct inet_sock *inet = inet_sk(sk);
  	struct ipv6_pinfo *np = inet6_sk(sk);

  	struct net *net = sock_net(sk);

  	struct ipv6hdr *hdr;
  	struct ipv6_txoptions *opt = np->cork.opt;

  	struct rt6_info *rt = (struct rt6_info *)inet->cork.base.dst;

  	struct flowi6 *fl6 = &inet->cork.fl.u.ip6;
  	unsigned char proto = fl6->flowi6_proto;

  	int err = 0;
  
  	if ((skb = __skb_dequeue(&sk->sk_write_queue)) == NULL)
  		goto out;
  	tail_skb = &(skb_shinfo(skb)->frag_list);
  
  	/* move skb->data to ip header from ext header */

  	if (skb->data < skb_network_header(skb))

  		__skb_pull(skb, skb_network_offset(skb));

  	while ((tmp_skb = __skb_dequeue(&sk->sk_write_queue)) != NULL) {

  		__skb_pull(tmp_skb, skb_network_header_len(skb));

  		*tail_skb = tmp_skb;
  		tail_skb = &(tmp_skb->next);
  		skb->len += tmp_skb->len;
  		skb->data_len += tmp_skb->len;

  		skb->truesize += tmp_skb->truesize;

  		tmp_skb->destructor = NULL;
  		tmp_skb->sk = NULL;

  	}

  	/* Allow local fragmentation. */

  	if (np->pmtudisc < IPV6_PMTUDISC_DO)

  		skb->local_df = 1;

  	*final_dst = fl6->daddr;

  	__skb_pull(skb, skb_network_header_len(skb));

  	if (opt && opt->opt_flen)
  		ipv6_push_frag_opts(skb, opt, &proto);
  	if (opt && opt->opt_nflen)
  		ipv6_push_nfrag_opts(skb, opt, &proto, &final_dst);

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

  	hdr = ipv6_hdr(skb);

  	*(__be32*)hdr = fl6->flowlabel |

  		     htonl(0x60000000 | ((int)np->cork.tclass << 20));

  	hdr->hop_limit = np->cork.hop_limit;
  	hdr->nexthdr = proto;

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

  	skb->priority = sk->sk_priority;

  	skb->mark = sk->sk_mark;

  	skb_dst_set(skb, dst_clone(&rt->dst));

  	IP6_UPD_PO_STATS(net, rt->rt6i_idev, IPSTATS_MIB_OUT, skb->len);

  	if (proto == IPPROTO_ICMPV6) {

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

  		ICMP6MSGOUT_INC_STATS_BH(net, idev, icmp6_hdr(skb)->icmp6_type);

  		ICMP6_INC_STATS_BH(net, idev, ICMP6_MIB_OUTMSGS);

  	}

  	err = ip6_local_out(skb);

  	if (err) {
  		if (err > 0)

  			err = net_xmit_errno(err);

  		if (err)
  			goto error;
  	}
  
  out:

  	ip6_cork_release(inet, np);

  	return err;
  error:

  	IP6_INC_STATS(net, rt->rt6i_idev, IPSTATS_MIB_OUTDISCARDS);

  	goto out;
  }
  
  void ip6_flush_pending_frames(struct sock *sk)
  {

  	struct sk_buff *skb;
  
  	while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL) {

  		if (skb_dst(skb))
  			IP6_INC_STATS(sock_net(sk), ip6_dst_idev(skb_dst(skb)),

  				      IPSTATS_MIB_OUTDISCARDS);

  		kfree_skb(skb);
  	}

  	ip6_cork_release(inet_sk(sk), inet6_sk(sk));

  }