From 6b5f0729f0b12a6c7af4ca741fbb1f0687da6d9e Mon Sep 17 00:00:00 2001
From: thechile <scott.mcgillivray@gmail.com>
Date: Tue, 15 Oct 2013 20:15:27 +0800
Subject: [PATCH] avoid duplicate nameserver entries in resolv.conf

currently the deemed best nameserver denoted by "use_server" will occur twice in the resolv.conf output which isn't ideal and in some circumstances could incur delayed lookups if it were to fail before the next cronjob to test for availability.

Proposed change ensures each nameserver exists only once.
---
 nsfailover.sh | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/nsfailover.sh b/nsfailover.sh
index e1ef911..77d64a0 100755
--- a/nsfailover.sh
+++ b/nsfailover.sh
@@ -130,11 +130,16 @@ fi
 info "Best nameserver is ${use_level} (${use_server})"
 
 # Build new config (without comments!)
-resolvconf="nameserver ${use_server}
-nameserver ${NS_1}
-nameserver ${NS_2}
-nameserver ${NS_3}
-options timeout:${NS_TIMEOUT} attempts:${NS_ATTEMPTS}"
+resolvconf="nameserver ${use_server}\n"
+for ns in ${NS_1} ${NS_2} ${NS_3}
+do
+        if [[ "$ns" != "${use_server}" ]]
+        then
+                resolvconf+="nameserver $ns\n"
+        fi
+done
+resolvconf+="options timeout:${NS_TIMEOUT} attempts:${NS_ATTEMPTS}"
+
 # Optionally add search parameter
 [ -n "${NS_SEARCH}" ] && resolvconf="${resolvconf}
 search ${NS_SEARCH}"