[chrony/f17] improve chrony-helper to keep track of servers added from DHCP (#787042)

[Miroslav Lichvar]

commit 2ca8fa688241e0648987c4e655b85f25c1d868db
Author: Miroslav Lichvar <mlichvar at redhat.com>
Date:   Fri Feb 10 17:22:48 2012 +0100

    improve chrony-helper to keep track of servers added from DHCP (#787042)

 chrony.dhclient |   16 +++++++---------
 chrony.helper   |   52 ++++++++++++++++++++++++++++++++++++++++++++--------
 2 files changed, 51 insertions(+), 17 deletions(-)
---
diff --git a/chrony.dhclient b/chrony.dhclient
index a01138e..f779ac8 100644
--- a/chrony.dhclient
+++ b/chrony.dhclient
@@ -5,20 +5,18 @@ SERVERFILE=$SAVEDIR/chrony.servers.$interface
 chrony_config() {
 	rm -f $SERVERFILE
 	if [ "$PEERNTP" != "no" ]; then
-		/usr/libexec/chrony-helper command "$(
-			for server in $new_ntp_servers; do
-				echo "add server $server $NTPSERVERARGS"
-				echo "$server $NTPSERVERARGS" >> $SERVERFILE
-			done)" &> /dev/null || :
+		for server in $new_ntp_servers; do
+			echo "$server $NTPSERVERARGS" >> $SERVERFILE
+		done
+		/usr/libexec/chrony-helper is-running &&
+			/usr/libexec/chrony-helper add-dhclient-servers || :
 	fi
 }
 
 chrony_restore() {
 	if [ -f $SERVERFILE ]; then
-		/usr/libexec/chrony-helper command "$(
-			while read server serverargs; do
-				echo "delete $server"
-			done < $SERVERFILE)" &> /dev/null
 		rm -f $SERVERFILE
+		/usr/libexec/chrony-helper is-running &&
+			/usr/libexec/chrony-helper remove-dhclient-servers || :
 	fi
 }
diff --git a/chrony.helper b/chrony.helper
index 9158ae3..809794e 100644
--- a/chrony.helper
+++ b/chrony.helper
@@ -4,6 +4,7 @@ config=/etc/chrony.conf
 keyfile=/etc/chrony.keys
 chronyc=/usr/bin/chronyc
 dhclient_servers=/var/lib/dhclient/chrony.servers.*
+dhclient_added_servers=/var/lib/dhclient/chrony.added_servers
 service_name=chronyd.service
 
 get_key() {
@@ -36,14 +37,43 @@ generate_commandkey() {
     [ -n "$commandkey" ] && echo "$commandkeyid $commandkey" >> $keyfile
 }
 
+update_dhclient_added_servers() {
+    new_servers=$(echo "$1" | sort -u)
+    old_servers=$(cat $dhclient_added_servers 2> /dev/null)
+    [ "$old_servers" = "$new_servers" ] && return 0
+    [ -n "$new_servers" ] && echo "$new_servers" > $dhclient_added_servers ||
+        rm -f $dhclient_added_servers
+}
+
 add_dhclient_servers() {
-    command=$(cat $dhclient_servers 2> /dev/null |
-        while read server serverargs; do
-            echo "add server $server $serverargs"
-        done)
-    if [ -n "$command" ]; then
-        chrony_command "$command" &> /dev/null
-    fi
+    shopt -s nullglob
+    servers_files=($dhclient_servers)
+    shopt -u nullglob
+    (( ${#servers_files[*]} )) || return 0
+
+    added_servers=$(
+        cat $dhclient_added_servers 2> /dev/null
+        cat ${servers_files[*]} |
+            while read server serverargs; do
+                chrony_command "add server $server $serverargs" &> /dev/null &&
+                    echo "$server"
+            done)
+    update_dhclient_added_servers "$added_servers"
+}
+
+remove_dhclient_servers() {
+    [ -f $dhclient_added_servers ] || return 0
+    all_servers=$(
+        cat $dhclient_servers 2> /dev/null |
+            while read server serverargs; do
+                echo "$server"
+            done | sort -u)
+    echo "$all_servers" | comm -23 $dhclient_added_servers - |
+        while read server; do
+            chrony_command "delete $server" &> /dev/null
+        done
+    added_servers=$(echo "$all_servers" | comm -12 $dhclient_added_servers -)
+    update_dhclient_added_servers "$added_servers"
 }
 
 is_running() {
@@ -57,6 +87,12 @@ case "$1" in
     add-dhclient-servers)
         add_dhclient_servers
         ;;
+    remove-dhclient-servers)
+        remove_dhclient_servers
+        ;;
+    is-running)
+        is_running
+        ;;
     command)
         is_running && chrony_command "$2"
         ;;
@@ -64,7 +100,7 @@ case "$1" in
         chrony_command "$2"
         ;;
     *)
-        echo $"Usage: $0 {generate-commandkey|add-dhclient-servers|command|forced-command}"
+        echo $"Usage: $0 {generate-commandkey|add-dhclient-servers|remove-dhclient-servers|is-running|command|forced-command}"
         exit 2
 esac
 exit $?