zebra: change router-id selection algo

The router-id table looks like is supposed to be sorted in current
quagga code, but the nodes are not added with the sorting
function.

The sorting function is host byte order dependent.
The values need to converted before comparison.

Fixing this causes Zebra to choose the largest IP address
as router-id, rather than the last address. This probably will
surprise some users. The other option would be to just remove the
comparison function and keep the existing LIFO behavior.

Lastly, simple subtraction works well for comparing.

* zebra/router-id.c
  * router_id_add_address(): employ listnode_add_sort()
  * router_id_cmp(): employ ntohl(), then compare integers

diff --git a/zebra/router-id.c b/zebra/router-id.c
index 41bab5456bc37e1d6253f897abc6a8c05f66b5b4..3d6b511c53c223fc349c489d00b9c794b9f7b2b0 100644 (file)
--- a/zebra/router-id.c
+++ b/zebra/router-id.c
@@ -136,7 +136,7 @@ router_id_add_address (struct connected *ifc)
     l = &rid_all_sorted_list;
   
   if (!router_id_find_node (l, ifc))
-    listnode_add (l, ifc);
+    listnode_add_sort (l, ifc);
 
   router_id_get (&after);
 
@@ -228,16 +228,12 @@ DEFUN (no_router_id,
 static int
 router_id_cmp (void *a, void *b)
 {
-  unsigned int A, B;
+  const struct connected *ifa = (const struct connected *)a;
+  const struct connected *ifb = (const struct connected *)b;
+  unsigned int A = ntohl(ifa->address->u.prefix4.s_addr);
+  unsigned int B = ntohl(ifb->address->u.prefix4.s_addr);
 
-  A = ((struct connected *) a)->address->u.prefix4.s_addr;
-  B = ((struct connected *) b)->address->u.prefix4.s_addr;
-
-  if (A > B)
-    return 1;
-  else if (A < B)
-    return -1;
-  return 0;
+  return (int) (A - B);
 }
 
 void