netfilter: don't set F_IFACE on ipv6 fib lookups

"fib" starts to behave strangely when an ipv6 default route is
added - the FIB lookup returns a route using 'oif' in this case.

This behaviour was inherited from ip6tables rpfilter so change
this as well.

Bugzilla: https://bugzilla.netfilter.org/show_bug.cgi?id=1221
Signed-off-by: Florian Westphal <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

net/ipv6/netfilter/ip6t_rpfilter.c

···
 	}
 
 	fl6.flowi6_mark = flags & XT_RPFILTER_VALID_MARK ? skb->mark : 0;
-	if ((flags & XT_RPFILTER_LOOSE) == 0) {
-		fl6.flowi6_oif = dev->ifindex;
-		lookup_flags |= RT6_LOOKUP_F_IFACE;
-	}
 
 	rt = (void *) ip6_route_lookup(net, &fl6, lookup_flags);
 	if (rt->dst.error)

net/ipv6/netfilter/nft_fib_ipv6.c

···
 	}
 
 	*dest = 0;
- again:
 	rt = (void *)ip6_route_lookup(nft_net(pkt), &fl6, lookup_flags);
 	if (rt->dst.error)
 		goto put_rt_err;
···
 	if (rt->rt6i_flags & (RTF_REJECT | RTF_ANYCAST | RTF_LOCAL))
 		goto put_rt_err;
 
-	if (oif && oif != rt->rt6i_idev->dev) {
-		/* multipath route? Try again with F_IFACE */
-		if ((lookup_flags & RT6_LOOKUP_F_IFACE) == 0) {
-			lookup_flags |= RT6_LOOKUP_F_IFACE;
-			fl6.flowi6_oif = oif->ifindex;
-			ip6_rt_put(rt);
-			goto again;
-		}
-	}
+	if (oif && oif != rt->rt6i_idev->dev)
+		goto put_rt_err;
 
 	switch (priv->result) {
 	case NFT_FIB_RESULT_OIF: