keepalived: high-availability files and data sync

add new package keepalived-sync to synchronize files and data
between master and backup node. The master node uses SSH over rsync
to send and the backup node will use inotifywatch to watch received files.

The master node can track rsync.sh script to send configuration file on
a backup node based on the vrrp_script configuration of the same script.

The backup node will have a keepalived-inotify service, which would watch
for newly received files and it would call hotplug event. Each service
can keep its respective script under the keepalived hotplug directory and
executes commands to stop, start service or update any config in real-time.

Whenever a switchover will happen, the backup node would have the latest
config and data files from the master node.

Hotplug events can be used to apply config when files are received.

Signed-off-by: Jaymin Patel <jem.patel@gmail.com>

net/keepalived/files/keepalived.init

@@ -256,6 +256,21 @@ print_track_bfd_indent() {
 	printf '\n' >> "$KEEPALIVED_CONF"
 }
 
+print_unicast_peer_indent() {
+	local section="$1"
+	local curr_track_elem="$2"
+	local indent="$3"
+	local name address
+
+	config_get name "$section" name
+	[ "$name" != "$curr_track_elem" ] && return 0
+
+	config_get address "$section" address
+	[ -z "$address" ] && return 0
+
+	printf '%b%s\n' "${indent}" "$address">> "$KEEPALIVED_CONF"
+}
+
 static_routes() {
 	local route
 	config_get route "$1" route
@@ -403,7 +418,13 @@ vrrp_instance() {
 	# Handle simple lists of strings (with no spaces in between)
 	for opt in unicast_peer; do
 		config_get "$opt" "$1" "$opt"
-		print_list_indent "$opt"
+		eval optval=\$$opt
+		[ -z "$optval" ] && continue
+		printf '%b%s {\n' "${INDENT_1}" "$opt" >> "$KEEPALIVED_CONF"
+		for t in $optval; do
+			config_foreach print_unicast_peer_indent peer "$t" "$INDENT_2"
+		done
+		printf '%b}\n' "${INDENT_1}" >> "$KEEPALIVED_CONF"
 	done
 	unset optval