From b415564df9531103dec10930f43dc557f9c2f2c3 Mon Sep 17 00:00:00 2001
From: david <david@e0a8ed71-7df4-0310-8962-fdc924857419>
Date: Sun, 30 Jun 2013 17:38:15 +0000
Subject: [PATCH] Sort routes first by netmask, then by metric.

Metric is used to break ties between routes with the same size netmask.
---
 CHANGELOG             |  5 +++++
 libnetutil/netutil.cc | 14 +++++++-------
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/CHANGELOG b/CHANGELOG
index 7a64415e5..5ca0e0b72 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,5 +1,10 @@
 # Nmap Changelog ($Id$); -*-text-*-
 
+o Nmap's routing table is now sorted first by netmask, then by metric.
+  Previously it was the other way around, which could cause a very
+  general route with a low metric to be preferred over a specific
+  route with a higher metric.
+
 o [Ncat] The -i option (idle timeout) now works in listen mode as well
   as connect mode. [Tomas Hozza]
 
diff --git a/libnetutil/netutil.cc b/libnetutil/netutil.cc
index 687384599..e7d5a5bfc 100644
--- a/libnetutil/netutil.cc
+++ b/libnetutil/netutil.cc
@@ -1200,7 +1200,7 @@ void tcppacketoptinfo(u8 *optp, int len, char *result, int bufsize) {
 
 
 
-/* A trivial function used with qsort to sort the routes by metric and netmask */
+/* A trivial function used with qsort to sort the routes by netmask and metric */
 static int routecmp(const void *a, const void *b) {
   struct sys_route *r1 = (struct sys_route *) a;
   struct sys_route *r2 = (struct sys_route *) b;
@@ -1209,16 +1209,16 @@ static int routecmp(const void *a, const void *b) {
   else if (r1->dest.ss_family > r2->dest.ss_family)
     return 1;
 
-  if (r1->metric < r2->metric)
-    return -1;
-  else if (r1->metric > r2->metric)
-    return 1;
-
   if (r1->netmask_bits < r2->netmask_bits)
     return 1;
   else if (r1->netmask_bits > r2->netmask_bits)
     return -1;
 
+  if (r1->metric < r2->metric)
+    return -1;
+  else if (r1->metric > r2->metric)
+    return 1;
+
   /* Compare addresses of equal elements to make the sort stable, as suggested
      by the Glibc manual. */
   if (a < b)
@@ -1698,7 +1698,7 @@ struct sys_route *getsysroutes(int *howmany, char *errstr, size_t errstrlen) {
     return NULL;
   }else{
     numroutes = *howmany;
-    /* Ensure that the route array is sorted by metric and netmask */
+    /* Ensure that the route array is sorted by netmask and metric */
     qsort(routes, numroutes, sizeof(routes[0]), routecmp);
   }
   return routes;