[PATCH] net: igmp: Use ingress interface rather than vrf device

[David Ahern <dsahern@gmail.com>]

Anuradha reported that statically added groups for interfaces enslaved
to a VRF device were not persisting. The problem is that igmp queries
and reports need to use the data in the in_dev for the real ingress
device rather than the VRF device. Update igmp_rcv accordingly.

Fixes: e58e41596811 ("net: Enable support for VRF with ipv4 multicast")
Reported-by: Anuradha Karuppiah <anuradhak@cumulusnetworks.com>
Signed-off-by: David Ahern <dsahern@gmail.com>
---
 net/ipv4/igmp.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 9f86b5133605..ab183af0b5b6 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -1007,10 +1007,18 @@ int igmp_rcv(struct sk_buff *skb)
 {
 	/* This basically follows the spec line by line -- see RFC1112 */
 	struct igmphdr *ih;
-	struct in_device *in_dev = __in_dev_get_rcu(skb->dev);
+	struct net_device *dev = skb->dev;
+	struct in_device *in_dev;
 	int len = skb->len;
 	bool dropped = true;
 
+	if (netif_is_l3_master(dev)) {
+		dev = dev_get_by_index_rcu(dev_net(dev), IPCB(skb)->iif);
+		if (!dev)
+			goto drop;
+	}
+
+	in_dev = __in_dev_get_rcu(dev);
 	if (!in_dev)
 		goto drop;
 
-- 
2.1.4