When converting the real bandwidth to the composite bandwidth, truncate

before applying the scaling factor.

When converting the composite bandwidth to the real bandwidth, apply
the scaling factor before the division and only then truncate.

This is to keep consistent with what Cisco does, the draft is unclear
on this point.

diff --git a/usr.sbin/eigrpd/rde_dual.c b/usr.sbin/eigrpd/rde_dual.c
index 3134e95..b1df17e 100644 (file)
--- a/usr.sbin/eigrpd/rde_dual.c
+++ b/usr.sbin/eigrpd/rde_dual.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: rde_dual.c,v 1.8 2015/10/25 00:39:14 renato Exp $ */
+/*     $OpenBSD: rde_dual.c,v 1.9 2015/10/25 00:42:02 renato Exp $ */
 
 /*
  * Copyright (c) 2015 Renato Westphal <renato@openbsd.org>
@@ -328,13 +328,18 @@ eigrp_real_delay(uint32_t delay)
 uint32_t
 eigrp_composite_bandwidth(uint32_t bandwidth)
 {
-       return ((EIGRP_SCALING_FACTOR * (uint32_t)10000000) / bandwidth);
+       /* truncate before applying the scaling factor */
+       bandwidth = 10000000 / bandwidth;
+       return (EIGRP_SCALING_FACTOR * bandwidth);
 }
 
-/* the formula is the same but let's focus on keeping the code readable */
 uint32_t
 eigrp_real_bandwidth(uint32_t bandwidth)
 {
+       /*
+        * apply the scaling factor before the division and only then truncate.
+        * this is to keep consistent with what cisco does.
+        */
        return ((EIGRP_SCALING_FACTOR * (uint32_t)10000000) / bandwidth);
 }