[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>

net/ipv6/af_inet6.c

@@ -98,6 +98,11 @@ static int inet6_create(struct socket *sock, int protocol)
 	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: