ipv4: harden fnhe_hashfun()

Lets make this hash function a bit secure, as ICMP attacks are still
in the wild.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 4 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 44b0cbdd76f1..234a43e233dc 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -596,12 +596,12 @@ static struct fib_nh_exception *fnhe_oldest(struct fnhe_hash_bucket *hash)
 
 static inline u32 fnhe_hashfun(__be32 daddr)
 {
+        static u32 fnhe_hashrnd __read_mostly;
         u32 hval;
 
-        hval = (__force u32) daddr;
-        hval ^= (hval >> 11) ^ (hval >> 22);
-
-        return hval & (FNHE_HASH_SIZE - 1);
+        net_get_random_once(&fnhe_hashrnd, sizeof(fnhe_hashrnd));
+        hval = jhash_1word((__force u32) daddr, fnhe_hashrnd);
+        return hash_32(hval, FNHE_HASH_SHIFT);
 }
 
 static void fill_route_from_fnhe(struct rtable *rt, struct fib_nh_exception *fnhe)