netns: Fix reassembly timer to use the right namespace

This trivial fix retrieves the network namespace from frag queue
and use it to get the network device in the right namespace.

Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/reassembly.c b/net/ipv6/reassembly.c
index 7b247e3..798cabc 100644
--- a/net/ipv6/reassembly.c
+++ b/net/ipv6/reassembly.c
@@ -197,6 +197,7 @@
 {
 	struct frag_queue *fq;
 	struct net_device *dev = NULL;
+	struct net *net;
 
 	fq = container_of((struct inet_frag_queue *)data, struct frag_queue, q);
 
@@ -207,7 +208,8 @@
 
 	fq_kill(fq);
 
-	dev = dev_get_by_index(&init_net, fq->iif);
+	net = container_of(fq->q.net, struct net, ipv6.frags);
+	dev = dev_get_by_index(net, fq->iif);
 	if (!dev)
 		goto out;