[INET]: Use jhash + random secret for ehash.

The days are gone when this was not an issue, there are folks out
there with huge bot networks that can be used to attack the
established hash tables on remote systems.

So just like the routing cache and connection tracking
hash, use Jenkins hash with random secret input.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 82572b5..df31cdd 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -98,6 +98,11 @@
 	int try_loading_module = 0;
 	int err;
 
+	if (sock->type != SOCK_RAW &&
+	    sock->type != SOCK_DGRAM &&
+	    !inet_ehash_secret)
+		build_ehash_secret();
+
 	/* Look for the requested type/protocol pair. */
 	answer = NULL;
 lookup_protocol: