check_dig: patch to make dig honor -t option

When a timeout value is specified with the -t option, dig will sometimes
timeout before the timer is actually reached.

The problem occurs because the check_dig plugin does not pass the specified
timeout value to dig, leaving dig to timeout with it's default value which
seems to be around 10-15seconds.

To reproduce:
time ./check_dig -H 127.0.0.2 -l www.google.com -t 30

It will not run for 30secs, which is the expected behaviour.

The following will work, because the timeout is less than the default dig
timeout, so the plugin cancels the dig command:
time ./check_dig -H 127.0.0.2 -l www.google.com -t 2

This fix passes the timeout value to dig, and sets the number of retries which tends to vary from system to system by default.

Closes #1168

2 files changed, 10 insertions, 2 deletions

diff --git a/THANKS.in b/THANKS.in
index aef787c..2cfa54e 100644
--- a/THANKS.in
+++ b/THANKS.in
@@ -305,3 +305,4 @@ Geoff Oakham
 Tim Laszlo
 Stéphane Bortzmeyer
 Luca Corti
+Jethro Carr
diff --git a/plugins/check_dig.c b/plugins/check_dig.c
index 7575995..5638017 100644
--- a/plugins/check_dig.c
+++ b/plugins/check_dig.c
@@ -48,6 +48,8 @@ void print_usage (void);
 
 #define UNDEFINED 0
 #define DEFAULT_PORT 53
+#define DEFAULT_TRIES 3
+#define DEFAULT_TIMEOUT 10
 
 char *query_address = NULL;
 char *record_type = "A";
@@ -57,6 +59,7 @@ char *dig_args = "";
 char *query_transport = "";
 int verbose = FALSE;
 int server_port = DEFAULT_PORT;
+int number_tries = DEFAULT_TRIES;
 double warning_interval = UNDEFINED;
 double critical_interval = UNDEFINED;
 struct timeval tv;
@@ -72,6 +75,7 @@ main (int argc, char **argv)
   long microsec;
   double elapsed_time;
   int result = STATE_UNKNOWN;
+  timeout_interval = DEFAULT_TIMEOUT;
 
   setlocale (LC_ALL, "");
   bindtextdomain (PACKAGE, LOCALEDIR);
@@ -87,9 +91,12 @@ main (int argc, char **argv)
   if (process_arguments (argc, argv) == ERROR)
     usage_va(_("Could not parse arguments"));
 
+  /* dig applies the timeout to each try, so we need to work around this */
+  int timeout_interval_dig = ceil((double) timeout_interval / (double) number_tries);
+
   /* get the command to run */
-  xasprintf (&command_line, "%s %s @%s -p %d %s -t %s %s",
-            PATH_TO_DIG, query_transport, dns_server, server_port, query_address, record_type, dig_args);
+  xasprintf (&command_line, "%s @%s -p %d %s -t %s %s %s +tries=%d +time=%d",
+            PATH_TO_DIG, dns_server, server_port, query_address, record_type, dig_args, query_transport, number_tries, timeout_interval_dig);
 
   alarm (timeout_interval);
   gettimeofday (&tv, NULL);