[net PATCH] fib_trie: leaf_walk_rcu should not compute key if key is less than pn->key

[Alexander Duyck <aduyck@mirantis.com>]

We were computing the child index in cases where the key value we were
looking for was actually less than the base key of the tnode.  As a result
we were getting incorrect index values that would cause us to skip over
some children.

To fix this I have added a test that will force us to use child index 0 if
the key we are looking for is less than the key of the current tnode.

Fixes: 8be33e955cb9 ("fib_trie: Fib walk rcu should take a tnode and key instead of a trie and a leaf")
Reported-by: Brian Rak <brak@gameservers.com>
Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
---

This will need to be queued up for stable as well.  This applies to 4.1 and
4.2 kernels as well.

 net/ipv4/fib_trie.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 6c2af797f2f9..744e5936c10d 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -1569,7 +1569,7 @@ static struct key_vector *leaf_walk_rcu(struct key_vector **tn, t_key key)
 	do {
 		/* record parent and next child index */
 		pn = n;
-		cindex = key ? get_index(key, pn) : 0;
+		cindex = (key > pn->key) ? get_index(key, pn) : 0;
 
 		if (cindex >> pn->bits)
 			break;