net: ip6mr: fix static mfc/dev leaks on table destruction

Similar to ipv4, when destroying an mrt table the static mfc entries and
the static devices are kept, which leads to devices that can never be
destroyed (because of refcnt taken) and leaked memory. Make sure that
everything is cleaned up on netns destruction.

Fixes: 8229efdaef1e ("netns: ip6mr: enable namespace support in ipv6 multicast forwarding code")
CC: Benjamin Thery <[e-mail]>
Signed-off-by: Nikolay Aleksandrov <[e-mail]>
Reviewed-by: Cong Wang <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/ipv6/ip6mr.c

···
 			      int cmd);
 static int ip6mr_rtm_dumproute(struct sk_buff *skb,
 			       struct netlink_callback *cb);
-static void mroute_clean_tables(struct mr6_table *mrt);
+static void mroute_clean_tables(struct mr6_table *mrt, bool all);
 static void ipmr_expire_process(unsigned long arg);
 
 #ifdef CONFIG_IPV6_MROUTE_MULTIPLE_TABLES
···
 static void ip6mr_free_table(struct mr6_table *mrt)
 {
 	del_timer_sync(&mrt->ipmr_expire_timer);
-	mroute_clean_tables(mrt);
+	mroute_clean_tables(mrt, true);
 	kfree(mrt);
 }
 
···
  *	Close the multicast socket, and clear the vif tables etc
  */
 
-static void mroute_clean_tables(struct mr6_table *mrt)
+static void mroute_clean_tables(struct mr6_table *mrt, bool all)
 {
 	int i;
 	LIST_HEAD(list);
···
 	 *	Shut down all active vif entries
 	 */
 	for (i = 0; i < mrt->maxvif; i++) {
-		if (!(mrt->vif6_table[i].flags & VIFF_STATIC))
-			mif6_delete(mrt, i, &list);
+		if (!all && (mrt->vif6_table[i].flags & VIFF_STATIC))
+			continue;
+		mif6_delete(mrt, i, &list);
 	}
 	unregister_netdevice_many(&list);
 
···
 	 */
 	for (i = 0; i < MFC6_LINES; i++) {
 		list_for_each_entry_safe(c, next, &mrt->mfc6_cache_array[i], list) {
-			if (c->mfc_flags & MFC_STATIC)
+			if (!all && (c->mfc_flags & MFC_STATIC))
 				continue;
 			write_lock_bh(&mrt_lock);
 			list_del(&c->list);
···
 						     net->ipv6.devconf_all);
 			write_unlock_bh(&mrt_lock);
 
-			mroute_clean_tables(mrt);
+			mroute_clean_tables(mrt, false);
 			err = 0;
 			break;
 		}