[ntp] ignore duplicate servers from dhclient

[Miroslav Lichvar]

commit cc2495980d2b6c80da9bae752356b0bf69b6ac57
Author: Miroslav Lichvar <mlichvar at redhat.com>
Date:   Mon Jul 15 14:34:25 2013 +0200

    ignore duplicate servers from dhclient

 ntp.dhclient |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/ntp.dhclient b/ntp.dhclient
index 9608d93..1cc9f43 100755
--- a/ntp.dhclient
+++ b/ntp.dhclient
@@ -39,9 +39,12 @@ ntp_config() {
     if [ ! "${PEERNTP}" = "no" ] && [ -n "${new_ntp_servers}" ] &&
         [ -e ${CONF} ] && [ -d ${SAVEDIR} ]; then
         local conf=$(grep -v '^server .*  # added by /sbin/dhclient-script$' < ${CONF})
+        local unique_servers=$(comm -23 \
+            <(for s in ${new_ntp_servers}; do echo $s; done | sort -u) \
+            <(echo "$conf" | awk '$1=="peer"||$1=="server"{print $2}' | sort -u))
 
         conf=$(echo "$conf"
-            for s in ${new_ntp_servers}; do
+            for s in ${unique_servers}; do
                 echo "server ${s} ${NTPSERVERARGS}  # added by /sbin/dhclient-script"
             done)