netns: ipmr: enable namespace support in ipv4 multicast routing code

This last patch makes the appropriate changes to use and propagate the
network namespace where needed in IPv4 multicast routing code.

This consists mainly in replacing all the remaining init_net occurences
with current netns pointer retrieved from sockets, net devices or
mfc_caches depending on the routines' contexts.

Some routines receive a new 'struct net' parameter to propagate the current
netns:
* vif_add/vif_delete
* ipmr_new_tunnel
* mroute_clean_tables
* ipmr_cache_find
* ipmr_cache_report
* ipmr_cache_unresolved
* ipmr_mfc_add/ipmr_mfc_delete
* ipmr_get_route
* rt_fill_info (in route.c)

Signed-off-by: Benjamin Thery <benjamin.thery@bull.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/mroute.h

@@ -256,7 +256,8 @@ void mfc_net_set(struct mfc_cache *mfc, struct net *net)
 
 #ifdef __KERNEL__
 struct rtmsg;
-extern int ipmr_get_route(struct sk_buff *skb, struct rtmsg *rtm, int nowait);
+extern int ipmr_get_route(struct net *net, struct sk_buff *skb,
+			  struct rtmsg *rtm, int nowait);
 #endif
 
 #endif