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   /*
    *      IPv6 input
    *      Linux INET6 implementation
    *
    *      Authors:
    *      Pedro Roque             <roque@di.fc.ul.pt>
    *      Ian P. Morris           <I.P.Morris@soton.ac.uk>
    *
    *      Based in linux/net/ipv4/ip_input.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
   *
   *      Mitsuru KANDA @USAGI and
   *      YOSHIFUJI Hideaki @USAGI: Remove ipv6_parse_exthdrs().
   */
  
  #include <linux/errno.h>
  #include <linux/types.h>
  #include <linux/socket.h>
  #include <linux/sockios.h>
  #include <linux/net.h>
  #include <linux/netdevice.h>
  #include <linux/in6.h>
  #include <linux/icmpv6.h>
  #include <linux/mroute6.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/protocol.h>
  #include <net/transp_v6.h>
  #include <net/rawv6.h>
  #include <net/ndisc.h>
  #include <net/ip6_route.h>
  #include <net/addrconf.h>
  #include <net/xfrm.h>
  
  
  
  int ip6_rcv_finish(struct sk_buff *skb)
  {
          if (sysctl_ip_early_demux && !skb_dst(skb)) {
                  const struct inet6_protocol *ipprot;
  
                  ipprot = rcu_dereference(inet6_protos[ipv6_hdr(skb)->nexthdr]);
                  if (ipprot && ipprot->early_demux)
                          ipprot->early_demux(skb);
          }
          if (!skb_dst(skb))
                  ip6_route_input(skb);
  
          return dst_input(skb);
  }
  
  int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
  {
          const struct ipv6hdr *hdr;
          u32             pkt_len;
          struct inet6_dev *idev;
          struct net *net = dev_net(skb->dev);
  
          if (skb->pkt_type == PACKET_OTHERHOST) {
                  kfree_skb(skb);
                  return NET_RX_DROP;
          }
  
          rcu_read_lock();
  
          idev = __in6_dev_get(skb->dev);
  
          IP6_UPD_PO_STATS_BH(net, idev, IPSTATS_MIB_IN, skb->len);
  
          if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL ||
              !idev || unlikely(idev->cnf.disable_ipv6)) {
                  IP6_INC_STATS_BH(net, idev, IPSTATS_MIB_INDISCARDS);
                  goto drop;
          }
  
          memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
  
          /*
           * Store incoming device index. When the packet will
           * be queued, we cannot refer to skb->dev anymore.
           *
           * BTW, when we send a packet for our own local address on a
           * non-loopback interface (e.g. ethX), it is being delivered
           * via the loopback interface (lo) here; skb->dev = loopback_dev.
           * It, however, should be considered as if it is being
           * arrived via the sending interface (ethX), because of the
          * nature of scoping architecture. --yoshfuji
          */
         IP6CB(skb)->iif = skb_dst(skb) ? ip6_dst_idev(skb_dst(skb))->dev->ifindex : dev->ifindex;
 
         if (unlikely(!pskb_may_pull(skb, sizeof(*hdr))))
                 goto err;
 
         hdr = ipv6_hdr(skb);
 
         if (hdr->version != 6)
                 goto err;
 
         /*
          * RFC4291 2.5.3
          * A packet received on an interface with a destination address
          * of loopback must be dropped.
          */
         if (!(dev->flags & IFF_LOOPBACK) &&
             ipv6_addr_loopback(&hdr->daddr))
                 goto err;
 
         /* RFC4291 Errata ID: 3480
          * Interface-Local scope spans only a single interface on a
          * node and is useful only for loopback transmission of
          * multicast.  Packets with interface-local scope received
          * from another node must be discarded.
          */
         if (!(skb->pkt_type == PACKET_LOOPBACK ||
               dev->flags & IFF_LOOPBACK) &&
             ipv6_addr_is_multicast(&hdr->daddr) &&
             IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 1)
                 goto err;
 
         /* RFC4291 2.7
          * Nodes must not originate a packet to a multicast address whose scope
          * field contains the reserved value 0; if such a packet is received, it
          * must be silently dropped.
          */
         if (ipv6_addr_is_multicast(&hdr->daddr) &&
             IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 0)
                 goto err;
 
         /*
          * RFC4291 2.7
          * Multicast addresses must not be used as source addresses in IPv6
          * packets or appear in any Routing header.
          */
         if (ipv6_addr_is_multicast(&hdr->saddr))
                 goto err;
 
         skb->transport_header = skb->network_header + sizeof(*hdr);
         IP6CB(skb)->nhoff = offsetof(struct ipv6hdr, nexthdr);
 
         pkt_len = ntohs(hdr->payload_len);
 
         /* pkt_len may be zero if Jumbo payload option is present */
         if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
                 if (pkt_len + sizeof(struct ipv6hdr) > skb->len) {
                         IP6_INC_STATS_BH(net,
                                          idev, IPSTATS_MIB_INTRUNCATEDPKTS);
                         goto drop;
                 }
                 if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr))) {
                         IP6_INC_STATS_BH(net, idev, IPSTATS_MIB_INHDRERRORS);
                         goto drop;
                 }
                 hdr = ipv6_hdr(skb);
         }
 
         if (hdr->nexthdr == NEXTHDR_HOP) {
                 if (ipv6_parse_hopopts(skb) < 0) {
                         IP6_INC_STATS_BH(net, idev, IPSTATS_MIB_INHDRERRORS);
                         rcu_read_unlock();
                         return NET_RX_DROP;
                 }
         }
 
         rcu_read_unlock();
 
         /* Must drop socket now because of tproxy. */
         skb_orphan(skb);
 
         return NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING, skb, dev, NULL,
                        ip6_rcv_finish);
 err:
         IP6_INC_STATS_BH(net, idev, IPSTATS_MIB_INHDRERRORS);
 drop:
         rcu_read_unlock();
         kfree_skb(skb);
         return NET_RX_DROP;
 }
 
 /*
  *      Deliver the packet to the host
  */
 
 
 static int ip6_input_finish(struct sk_buff *skb)
 {
         struct net *net = dev_net(skb_dst(skb)->dev);
         const struct inet6_protocol *ipprot;
         struct inet6_dev *idev;
         unsigned int nhoff;
         int nexthdr;
         bool raw;
 
         /*
          *      Parse extension headers
          */
 
         rcu_read_lock();
 resubmit:
         idev = ip6_dst_idev(skb_dst(skb));
         if (!pskb_pull(skb, skb_transport_offset(skb)))
                 goto discard;
         nhoff = IP6CB(skb)->nhoff;
         nexthdr = skb_network_header(skb)[nhoff];
 
         raw = raw6_local_deliver(skb, nexthdr);
         if ((ipprot = rcu_dereference(inet6_protos[nexthdr])) != NULL) {
                 int ret;
 
                 if (ipprot->flags & INET6_PROTO_FINAL) {
                         const struct ipv6hdr *hdr;
 
                         /* Free reference early: we don't need it any more,
                            and it may hold ip_conntrack module loaded
                            indefinitely. */
                         nf_reset(skb);
 
                         skb_postpull_rcsum(skb, skb_network_header(skb),
                                            skb_network_header_len(skb));
                         hdr = ipv6_hdr(skb);
                         if (ipv6_addr_is_multicast(&hdr->daddr) &&
                             !ipv6_chk_mcast_addr(skb->dev, &hdr->daddr,
                             &hdr->saddr) &&
                             !ipv6_is_mld(skb, nexthdr, skb_network_header_len(skb)))
                                 goto discard;
                 }
                 if (!(ipprot->flags & INET6_PROTO_NOPOLICY) &&
                     !xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb))
                         goto discard;
 
                 ret = ipprot->handler(skb);
                 if (ret > 0)
                         goto resubmit;
                 else if (ret == 0)
                         IP6_INC_STATS_BH(net, idev, IPSTATS_MIB_INDELIVERS);
         } else {
                 if (!raw) {
                         if (xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
                                 IP6_INC_STATS_BH(net, idev,
                                                  IPSTATS_MIB_INUNKNOWNPROTOS);
                                 icmpv6_send(skb, ICMPV6_PARAMPROB,
                                             ICMPV6_UNK_NEXTHDR, nhoff);
                         }
                         kfree_skb(skb);
                 } else {
                         IP6_INC_STATS_BH(net, idev, IPSTATS_MIB_INDELIVERS);
                         consume_skb(skb);
                 }
         }
         rcu_read_unlock();
         return 0;
 
 discard:
         IP6_INC_STATS_BH(net, idev, IPSTATS_MIB_INDISCARDS);
         rcu_read_unlock();
         kfree_skb(skb);
         return 0;
 }
 
 
 int ip6_input(struct sk_buff *skb)
 {
         return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_IN, skb, skb->dev, NULL,
                        ip6_input_finish);
 }
 
 int ip6_mc_input(struct sk_buff *skb)
 {
         const struct ipv6hdr *hdr;
         bool deliver;
 
         IP6_UPD_PO_STATS_BH(dev_net(skb_dst(skb)->dev),
                          ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_INMCAST,
                          skb->len);
 
         hdr = ipv6_hdr(skb);
         deliver = ipv6_chk_mcast_addr(skb->dev, &hdr->daddr, NULL);
 
 #ifdef CONFIG_IPV6_MROUTE
         /*
          *      IPv6 multicast router mode is now supported ;)
          */
         if (dev_net(skb->dev)->ipv6.devconf_all->mc_forwarding &&
             !(ipv6_addr_type(&hdr->daddr) &
               (IPV6_ADDR_LOOPBACK|IPV6_ADDR_LINKLOCAL)) &&
             likely(!(IP6CB(skb)->flags & IP6SKB_FORWARDED))) {
                 /*
                  * Okay, we try to forward - split and duplicate
                  * packets.
                  */
                 struct sk_buff *skb2;
                 struct inet6_skb_parm *opt = IP6CB(skb);
 
                 /* Check for MLD */
                 if (unlikely(opt->flags & IP6SKB_ROUTERALERT)) {
                         /* Check if this is a mld message */
                         u8 nexthdr = hdr->nexthdr;
                         __be16 frag_off;
                         int offset;
 
                         /* Check if the value of Router Alert
                          * is for MLD (0x0000).
                          */
                         if (opt->ra == htons(IPV6_OPT_ROUTERALERT_MLD)) {
                                 deliver = false;
 
                                 if (!ipv6_ext_hdr(nexthdr)) {
                                         /* BUG */
                                         goto out;
                                 }
                                 offset = ipv6_skip_exthdr(skb, sizeof(*hdr),
                                                           &nexthdr, &frag_off);
                                 if (offset < 0)
                                         goto out;
 
                                 if (!ipv6_is_mld(skb, nexthdr, offset))
                                         goto out;
 
                                 deliver = true;
                         }
                         /* unknown RA - process it normally */
                 }
 
                 if (deliver)
                         skb2 = skb_clone(skb, GFP_ATOMIC);
                 else {
                         skb2 = skb;
                         skb = NULL;
                 }
 
                 if (skb2) {
                         ip6_mr_input(skb2);
                 }
         }
 out:
 #endif
         if (likely(deliver))
                 ip6_input(skb);
         else {
                 /* discard */
                 kfree_skb(skb);
         }
 
         return 0;
 }
 

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