net: Make flow cache namespace-aware

flow_cache_lookup will return a cached object (or null pointer) that the
resolver (i.e. xfrm_policy_lookup) previously found for another namespace
using the same key/family/dir.  Instead, make the namespace part of what
identifies entries in the cache.

As before, flow_entry_valid will return 0 for entries where the namespace
has been deleted, and they will be removed from the cache the next time
flow_cache_gc_task is run.

Reported-by: Andrew Dickinson <whydna@whydna.net>
Signed-off-by: David Ward <david.ward@ll.mit.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/flow.c

@@ -30,6 +30,7 @@ struct flow_cache_entry {
 		struct hlist_node	hlist;
 		struct list_head	gc_list;
 	} u;
+	struct net			*net;
 	u16				family;
 	u8				dir;
 	u32				genid;
@@ -232,7 +233,8 @@ flow_cache_lookup(struct net *net, const struct flowi *key, u16 family, u8 dir,
 
 	hash = flow_hash_code(fc, fcp, key);
 	hlist_for_each_entry(tfle, entry, &fcp->hash_table[hash], u.hlist) {
-		if (tfle->family == family &&
+		if (tfle->net == net &&
+		    tfle->family == family &&
 		    tfle->dir == dir &&
 		    flow_key_compare(key, &tfle->key) == 0) {
 			fle = tfle;
@@ -246,6 +248,7 @@ flow_cache_lookup(struct net *net, const struct flowi *key, u16 family, u8 dir,
 
 		fle = kmem_cache_alloc(flow_cachep, GFP_ATOMIC);
 		if (fle) {
+			fle->net = net;
 			fle->family = family;
 			fle->dir = dir;
 			memcpy(&fle->key, key, sizeof(*key));