rdnss/merge-hook.in | 77 ++++++++++++++++++++++++++++-------------------------
 1 file changed, 41 insertions(+), 36 deletions(-)

diff --git a/rdnss/merge-hook.in b/rdnss/merge-hook.in
index 00ddcb2..ee65667 100644
--- a/rdnss/merge-hook.in
+++ b/rdnss/merge-hook.in
@@ -17,52 +17,57 @@
 # *  along with this program. If not, see <http://www.gnu.org/licenses/>. *
 # *************************************************************************
 
-set -e
-
 PATH=/sbin:/bin
+RESOLVCONF_TOOL=/sbin/resolvconf
+RDNSSD_RESOLV_CONF=@LOCALSTATEDIR@/run/rdnssd/resolv.conf
 
-# Max number of nameserver options taken into account. Should be as
-# defined in <resolv.h>
-MAXNS=3
+merge_resolv_conf()
+{
+	set -e
 
-# This script tries to share available nameserver slots with IPv4
-# entries, for example to allow fallback to IPv4 if IPv6 fails. If
-# there is not enough room for all IPv6 and IPv4 entries, this script
-# will limit the IPv6 entries it adds to $RDNSS_LIMIT only.
-RDNSS_LIMIT=$(($MAXNS - 1))
+	# Max number of nameserver options taken into account. Should be as
+	# defined in <resolv.h>
+	MAXNS=3
 
-sysconfdir='@SYSCONFDIR@'
-localstatedir='@LOCALSTATEDIR@'
-resolvconf="$sysconfdir/resolv.conf"
-myresolvconf="$localstatedir/run/rdnssd/resolv.conf"
+	# This script tries to share available nameserver slots with IPv4
+	# entries, for example to allow fallback to IPv4 if IPv6 fails. If
+	# there is not enough room for all IPv6 and IPv4 entries, this script
+	# will limit the IPv6 entries it adds to $RDNSS_LIMIT only.
+	RDNSS_LIMIT=$(($MAXNS - 1))
 
-# These should be POSIX-compliant BREs
-RE_NSV4='^nameserver  *\([0-9]\{1,3\}\.\)\{3,3\}[0-9]\{1,3\} *$'
-RE_NSV4OR6='^nameserver  *[a-fA-F0-9:\.]\{1,46\}\(%[a-zA-Z0-9]\{1,\}\)\{0,1\} *$'
+	sysconfdir='@SYSCONFDIR@'
+	resolvconf="$sysconfdir/resolv.conf"
 
-# Count how many IPv6 nameservers we can fit
+	# These should be POSIX-compliant BREs
+	RE_NSV4='^nameserver  *\([0-9]\{1,3\}\.\)\{3,3\}[0-9]\{1,3\} *$'
+	RE_NSV4OR6='^nameserver  *[a-fA-F0-9:\.]\{1,46\}\(%[a-zA-Z0-9]\{1,\}\)\{0,1\} *$'
 
-limit=$RDNSS_LIMIT
+	# Count how many IPv6 nameservers we can fit
 
-nnsv4=`grep -c "$RE_NSV4" $resolvconf || [ $? -le 1 ]`
-room=$(($MAXNS - $nnsv4))
+	limit=$RDNSS_LIMIT
 
-if [ $limit -lt $room ]; then
-	limit=$room
-fi
+	nnsv4=`grep -c "$RE_NSV4" $resolvconf || [ $? -le 1 ]`
+	room=$(($MAXNS - $nnsv4))
 
-# Merge and write the result. Let rdnssd assume ownership of all IPv6
-# nameservers, and remove extraneous IPv6 entries as expired. However
-# DHCPv4 most often sets up search list entries, and rdnssd cannot
-# clobber these lest it causes counterintuitive breakage. There is no
-# easy way to properly merge and manage DNSSL entries here, so just drop
-# them.
+	if [ $limit -lt $room ]; then
+		limit=$room
+	fi
 
-{
-	sed -e "/$RE_NSV4OR6/d" < $resolvconf
-	grep -m $limit "$RE_NSV4OR6" < $myresolvconf || [ $? -le 1 ]
-	sed -ne "/$RE_NSV4/p" < $resolvconf
-} > $resolvconf.tmp
+	# Merge and write the result
 
-mv -f $resolvconf.tmp $resolvconf
+	{
+		sed -e "/$RE_NSV4OR6/d" < $resolvconf
+		grep -m $limit "$RE_NSV4OR6" < $RDNSSD_RESOLV_CONF || [ $? -le 1 ]
+		sed -ne "/$RE_NSV4/p" < $resolvconf
+	} | awk '!a[$0]++' > $resolvconf.tmp
 
+	mv -f $resolvconf.tmp $resolvconf
+}
+
+[ -f "$RDNSSD_RESOLV_CONF" ] || exit 0
+
+if [ -x "$RESOLVCONF_TOOL" ]; then
+	$RESOLVCONF_TOOL -a 000.rdnssd < "$RDNSSD_RESOLV_CONF"
+else
+	merge_resolv_conf
+fi