Eventscript functions: optimise ctdb_check_tcp_ports() and add debug.

ctdb_check_tcp_ports() runs "netstat -a -t -n" in a loop for each
port.  There are 2 problems with this:

* Netstat is run on each loop iteration when it need only be run once.

* The -a option is used to list all connections but the function only
  cares about the listening ports.  There may be many thousands of
  non-listening ports to grep through.

This changes ctdb_check_tcp_ports() to run netstat with the -l option
instead of the -a option.  It also only runs netstat once before the
main loop.

When a port is found to not be listening the output of the netstat
command is now dumped to help with debugging.

Signed-off-by: Martin Schwenke <martin@meltin.net>

(This used to be ctdb commit 830355a8b18c53cfcc3ad1e3009bbb1a7a681fa0)

ctdb/config/functions

@@ -324,15 +324,26 @@ ctdb_check_directories() {
 # check a set of tcp ports
 # usage: ctdb_check_tcp_ports <ports...>
 ######################################################
-ctdb_check_tcp_ports() {
+ctdb_check_tcp_ports()
+{
+    _cmd='netstat -l -t -n'
+    _ns=$($_cmd)
+    for _p ; do  # process each function argument (port)
+	for _a in '0\.0\.0\.0' '::' ; do
+	    _pat="[[:space:]]${_a}:${_p}[[:space:]]+[^[:space:]]+[[:space:]]+LISTEN"
+	    if echo "$_ns" | grep -E -q "$_pat" ; then
+		# We matched the port, so process next port
+		continue 2
+	    fi
+	done
 
-    for p ; do
-	if ! netstat -a -t -n | grep -q "0\.0\.0\.0:$p .*LISTEN" ; then
-            if ! netstat -a -t -n | grep -q ":::$p .*LISTEN" ; then
-		echo "ERROR: $service_name tcp port $p is not responding"
-		return 1
-            fi
-	fi
+	# We didn't match the port, so flag an error, print some debug
+	cat <<EOF
+ERROR: $service_name tcp port $_p is not responding
+$_cmd shows this output:
+$_ns
+EOF
+	return 1
     done
 }