/*
 *      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);

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;
        struct rt6_info *rt;

        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,
                                        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();
        rt = (struct rt6_info *) dst;
        neigh = rt->n;
        if (neigh) {
                int res = dst_neigh_output(dst, 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;
                        }
                        consume_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);
        }

        net_dbg_ratelimited("IPv6: sending pkt_too_big to self\n");
        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);
        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.
         */
        if (skb->dev == dst->dev && 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, &rt->rt6i_dst.addr, 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 = 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);
        IP6_ADD_STATS_BH(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTOCTETS, skb->len);
        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;
                struct net *net;

                net = dev_net(rt->dst.dev);
                peer = inet_getpeer_v6(net->ipv6.peers, &rt->rt6i_dst.addr, 1);
                if (peer) {
                        fhdr->identification = htonl(inet_getid(peer, 0));
                        inet_putpeer(peer);
                        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 (unlikely(!skb->local_df && skb->len > mtu)) {
                if (skb->sk && dst_allfrag(skb_dst(skb)))
                        sk_nocaps_add(skb->sk, NETIF_F_GSO_MASK);

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

        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!\n");
                        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);
        consume_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;
        struct rt6_info *rt;
#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();
        rt = (struct rt6_info *) *dst;
        n = rt->n;
        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;
}

static void ip6_append_data_mtu(int *mtu,
                                int *maxfraglen,
                                unsigned int fragheaderlen,
                                struct sk_buff *skb,
                                struct rt6_info *rt)
{
        if (!(rt->dst.flags & DST_XFRM_TUNNEL)) {
                if (skb == NULL) {
                        /* first fragment, reserve header_len */
                        *mtu = *mtu - rt->dst.header_len;

                } else {
                        /*
                         * this fragment is not first, the headers
                         * space is regarded as data space.
                         */
                        *mtu = dst_mtu(rt->dst.path);
                }
                *maxfraglen = ((*mtu - fragheaderlen) & ~7)
                              + fragheaderlen - sizeof(struct frag_hdr);
        }
}

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, *skb_prev = NULL;
        unsigned int maxfraglen, fragheaderlen;
        int exthdrlen;
        int dst_exthdrlen;
        int hh_len;
        int mtu;
        int copy;
        int err;
        int offset = 0;
        __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;
                if (rt->dst.flags & DST_XFRM_TUNNEL)
                        mtu = np->pmtudisc == IPV6_PMTUDISC_PROBE ?
                              rt->dst.dev->mtu : dst_mtu(&rt->dst);
                else
                        mtu = np->pmtudisc == IPV6_PMTUDISC_PROBE ?
                              rt->dst.dev->mtu : dst_mtu(rt->dst.path);
                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;
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 == NULL || skb_prev == NULL)
                                ip6_append_data_mtu(&mtu, &maxfraglen,
                                                    fragheaderlen, skb, rt);

                        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);

                        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 = CHECKSUM_NONE;
                        skb->csum = 0;
                        /* reserve for fragmentation and ipsec header */
                        skb_reserve(skb, hh_len + sizeof(struct frag_hdr) +
                                    dst_exthdrlen);

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

                        /*
                         *      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);
                        }
                        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;

                        /*
                         * 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;
}
EXPORT_SYMBOL_GPL(ip6_append_data);

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;
}
EXPORT_SYMBOL_GPL(ip6_push_pending_frames);

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));
}
EXPORT_SYMBOL_GPL(ip6_flush_pending_frames);