netfilter: ipv6: Preserve link scope traffic original oif

When ip6_route_me_harder is invoked, it resets outgoing interface of:
  - link-local scoped packets sent by neighbor discovery
  - multicast packets sent by MLD host
  - multicast packets send by MLD proxy daemon that sets outgoing
    interface through IPV6_PKTINFO ipi6_ifindex

Link-local and multicast packets must keep their original oif after
ip6_route_me_harder is called.

Signed-off-by: Alin Nastac <alin.nastac@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/ipv6/netfilter.c b/net/ipv6/netfilter.c
index 5ae8e1c51079cb2cb36324af300762c5463134ba..8b075f0bc35169b4098bda738950d631b62ec415 100644 (file)
--- a/net/ipv6/netfilter.c
+++ b/net/ipv6/netfilter.c
@@ -24,7 +24,8 @@ int ip6_route_me_harder(struct net *net, struct sk_buff *skb)
        unsigned int hh_len;
        struct dst_entry *dst;
        struct flowi6 fl6 = {
-               .flowi6_oif = sk ? sk->sk_bound_dev_if : 0,
+               .flowi6_oif = sk && sk->sk_bound_dev_if ? sk->sk_bound_dev_if :
+                       rt6_need_strict(&iph->daddr) ? skb_dst(skb)->dev->ifindex : 0,
                .flowi6_mark = skb->mark,
                .flowi6_uid = sock_net_uid(net, sk),
                .daddr = iph->daddr,