gtp: initial random seed for the hash tables

I think it's very hard to deploy any hashbomb attack since the
entries are created via netlink, but let's just avoid that someone
generates traffic to spend cycles on a busy hashtable chain.

gtp.c

@@ -27,9 +27,6 @@
 #include "gtp.h"
 #include "gtp_nl.h"
 
-/* implementation-specific definitions */
-
-/* FIXME: initialize this !! */
 static uint32_t gtp_h_initval;
 
 struct gsn {
@@ -1196,6 +1193,8 @@ static int __init gtp_init(void)
 {
 	int err;
 
+	get_random_bytes(&gtp_h_initval, sizeof(gtp_h_initval));
+
 	err = genl_register_family_with_ops(&gtp_genl_family, gtp_genl_ops);
 	if (err < 0)
 		return err;