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: NDaniel Lezcano <dlezcano@fr.ibm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/reassembly.c

@@ -197,6 +197,7 @@ static void ip6_frag_expire(unsigned long data)
 {
 	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 @@ static void ip6_frag_expire(unsigned long data)
 
 	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;