[NETNS][FRAGS]: Make the inet_frag_queue lookup work in namespaces.

Since fragment management code is consolidated, we cannot have the
pointer from inet_frag_queue to struct net, since we must know what
king of fragment this is.

So, I introduce the netns_frags structure. This one is currently
empty, but will be eventually filled with per-namespace
attributes. Each inet_frag_queue is tagged with this one.

The conntrack_reasm is not "netns-izated", so it has one static
netns_frags instance to keep working in init namespace.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/netns/ipv4.h

@@ -5,6 +5,8 @@
 #ifndef __NETNS_IPV4_H__
 #define __NETNS_IPV4_H__
 
+#include <net/inet_frag.h>
+
 struct ctl_table_header;
 struct ipv4_devconf;
 struct fib_rules_ops;
@@ -22,5 +24,7 @@ struct netns_ipv4 {
 #endif
 	struct hlist_head	*fib_table_hash;
 	struct sock		*fibnl;
+
+	struct netns_frags	frags;
 };
 #endif