Use slightly better algorithm for random IDs

diff --git a/src/lib/packet.c b/src/lib/packet.c
index 4a8e6ea..f20c9b6 100644 (file)
--- a/src/lib/packet.c
+++ b/src/lib/packet.c
@@ -345,6 +345,36 @@ bool fr_packet_list_socket_del(fr_packet_list_t *pl, int sockfd)
        return true;
 }
 
+
+static void fill_ids_array(fr_packet_socket_t *ps)
+{
+       int i;
+
+       ps->ids_index = 0;
+
+       /*
+        *      initialize the array with 256 IDs
+        */
+       for (i = 0; i < 256; i++) {
+               ps->ids[i] = i;
+       }
+
+       /*
+        *      Swap this one with a random other one from later in
+        *      the list.
+        */
+       for (i = 0; i < 256; i++) {
+               int tmp;
+               int k = fr_rand() % (256 - i);
+
+               tmp = ps->ids[i];
+               ps->ids[i] = ps->ids[i + k];
+               ps->ids[i + k] = tmp;
+       }
+
+       printf("\n");
+}
+
 bool fr_packet_list_socket_add(fr_packet_list_t *pl, int sockfd, int proto,
                              fr_ipaddr_t *dst_ipaddr, int dst_port,
                              void *ctx)
@@ -433,11 +463,7 @@ bool fr_packet_list_socket_add(fr_packet_list_t *pl, int sockfd, int proto,
        /*
         *      Populate the ID array with a random list of IDs.
         */
-       ps->ids_index = 0;
-
-       for (i = 0; i < 256; i++) {
-               ps->ids[fr_rand() & 0xff] = i;
-       }
+       fill_ids_array(ps);
 
        return true;
 }
@@ -766,10 +792,7 @@ bool fr_packet_list_id_alloc(fr_packet_list_t *pl, int proto,
         *      Refill the ID array with random IDs.
         */
        if (ps->ids_index == 256) {
-               for (i = 0; i < 256; i++) {
-                       ps->ids[fr_rand() & 0xff] = i;
-               }
-               ps->ids_index = 0;
+               fill_ids_array(ps);
        }
 
        return true;