[PATCH v2] net: netfilter: Fix ipv6 rp_filter dropping vrf packets by mistake

[linmiaohe]

From: Miaohe Lin <linmiaohe@xxxxxxxxxx>

When firewall is enabled with rp_filter, vrf ipv6 packets
will be dropped because in device is vrf but out device
is an enslaved device. So rt->rt6i_idev->dev != dev and
maybe return false in func rpfilter_lookup_reverse6.

Here is the out message when I ping the peer:
ip vrf exec vrf1 ping 2013::2 -c 1
1 packets transmitted, 0 received, 100% packet loss, time 0ms

The drop info in /var/log/message:
Apr 24 14:59:45 localhost kernel: [81316.158259] rpfilter_DROP: IN=vrf1
OUT= MAC=52:54:00:9e:dd:c1:52:54:00:4f:81:38:86:dd
SRC=2013:0000:0000:0000:0000:0000:0000:0002
DST=2013:0000:0000:0000:0000:0000:0000:0001 LEN=104 TC=0 HOPLIMIT=64
FLOWLBL=1032942 PROTO=ICMPv6 TYPE=129 CODE=0 ID=14943 SEQ=1

Signed-off-by: linmiaohe <linmiaohe@xxxxxxxxxx>
---
 net/ipv6/netfilter/ip6t_rpfilter.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/ipv6/netfilter/ip6t_rpfilter.c b/net/ipv6/netfilter/ip6t_rpfilter.c
index c3c6b09acdc4..cf1070ab1252 100644
--- a/net/ipv6/netfilter/ip6t_rpfilter.c
+++ b/net/ipv6/netfilter/ip6t_rpfilter.c
@@ -73,6 +73,12 @@ static bool rpfilter_lookup_reverse6(struct net *net, const struct sk_buff *skb,
 		goto out;
 	}

+	if (netif_is_l3_master(dev)) {
+		dev = dev_get_by_index_rcu(dev_net(dev), IP6CB(skb)->iif);
+		if (!dev)
+			goto out;
+	}
+
 	if (rt->rt6i_idev->dev == dev || (flags & XT_RPFILTER_LOOSE))
 		ret = true;
  out:
-- 
2.19.1