net/ipv6/netfilter/nf_dup_ipv6.c

   1 /*
   2  * (C) 2007 by Sebastian Claßen <sebastian.classen@freenet.ag>
   3  * (C) 2007-2010 by Jan Engelhardt <jengelh@medozas.de>
   4  *
   5  * Extracted from xt_TEE.c
   6  *
   7  * This program is free software; you can redistribute it and/or modify it
   8  * under the terms of the GNU General Public License version 2 or later, as
   9  * published by the Free Software Foundation.
  10  */
  11 #include <linux/module.h>
  12 #include <linux/percpu.h>
  13 #include <linux/skbuff.h>
  14 #include <linux/netfilter.h>
  15 #include <net/ipv6.h>
  16 #include <net/ip6_route.h>
  17 #include <net/netfilter/ipv6/nf_dup_ipv6.h>
  18 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
  19 #include <net/netfilter/nf_conntrack.h>
  20 #endif
  21
  22 static bool nf_dup_ipv6_route(struct net *net, struct sk_buff *skb,
  23                               const struct in6_addr *gw, int oif)
  24 {
  25         const struct ipv6hdr *iph = ipv6_hdr(skb);
  26         struct dst_entry *dst;
  27         struct flowi6 fl6;
  28
  29         memset(&fl6, 0, sizeof(fl6));
  30         if (oif != -1)
  31                 fl6.flowi6_oif = oif;
  32
  33         fl6.daddr = *gw;
  34         fl6.flowlabel = (__force __be32)(((iph->flow_lbl[0] & 0xF) << 16) |
  35                         (iph->flow_lbl[1] << 8) | iph->flow_lbl[2]);
  36         fl6.flowi6_flags = FLOWI_FLAG_KNOWN_NH;
  37         dst = ip6_route_output(net, NULL, &fl6);
  38         if (dst->error) {
  39                 dst_release(dst);
  40                 return false;
  41         }
  42         skb_dst_drop(skb);
  43         skb_dst_set(skb, dst);
  44         skb->dev      = dst->dev;
  45         skb->protocol = htons(ETH_P_IPV6);
  46
  47         return true;
  48 }
  49
  50 void nf_dup_ipv6(struct net *net, struct sk_buff *skb, unsigned int hooknum,
  51                  const struct in6_addr *gw, int oif)
  52 {
  53         if (this_cpu_read(nf_skb_duplicated))
  54                 return;
  55         skb = pskb_copy(skb, GFP_ATOMIC);
  56         if (skb == NULL)
  57                 return;
  58
  59 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
  60         nf_reset(skb);
  61         nf_ct_set(skb, NULL, IP_CT_UNTRACKED);
  62 #endif
  63         if (hooknum == NF_INET_PRE_ROUTING ||
  64             hooknum == NF_INET_LOCAL_IN) {
  65                 struct ipv6hdr *iph = ipv6_hdr(skb);
  66                 --iph->hop_limit;
  67         }
  68         if (nf_dup_ipv6_route(net, skb, gw, oif)) {
  69                 __this_cpu_write(nf_skb_duplicated, true);
  70                 ip6_local_out(net, skb->sk, skb);
  71                 __this_cpu_write(nf_skb_duplicated, false);
  72         } else {
  73                 kfree_skb(skb);
  74         }
  75 }
  76 EXPORT_SYMBOL_GPL(nf_dup_ipv6);
  77
  78 MODULE_AUTHOR("Sebastian Claßen <sebastian.classen@freenet.ag>");
  79 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
  80 MODULE_DESCRIPTION("nf_dup_ipv6: IPv6 packet duplication");
  81 MODULE_LICENSE("GPL");