check_by_ssh: Add "-U" flag (#1123). (#1774)

This causes a 255 exit value from ssh(1), which indicates a connection failure,
to return UNKNOWN instead of CRITICAL; similar to check_nrpe's "-u" flag.

1 files changed, 16 insertions, 2 deletions

diff --git a/plugins/check_by_ssh.c b/plugins/check_by_ssh.c
index 39d49070..1ad547ed 100644
--- a/plugins/check_by_ssh.c
+++ b/plugins/check_by_ssh.c
@@ -50,6 +50,7 @@ unsigned int services = 0;
 int skip_stdout = 0;
 int skip_stderr = 0;
 int warn_on_stderr = 0;
+bool unknown_timeout = FALSE;
 char *remotecmd = NULL;
 char **commargv = NULL;
 int commargc = 0;
@@ -101,6 +102,13 @@ main (int argc, char **argv)
 
         result = cmd_run_array (commargv, &chld_out, &chld_err, 0);
 
+        /* SSH returns 255 if connection attempt fails; include the first line of error output */
+        if (result == 255 && unknown_timeout) {
+                printf (_("SSH connection failed: %s\n"),
+                        chld_err.lines > 0 ? chld_err.line[0] : "(no error output)");
+                return STATE_UNKNOWN;
+        }
+
         if (verbose) {
                 for(i = 0; i < chld_out.lines; i++)
                         printf("stdout: %s\n", chld_out.line[i]);
@@ -180,6 +188,7 @@ process_arguments (int argc, char **argv)
                 {"verbose", no_argument, 0, 'v'},
                 {"fork", no_argument, 0, 'f'},
                 {"timeout", required_argument, 0, 't'},
+                {"unknown-timeout", no_argument, 0, 'U'},
                 {"host", required_argument, 0, 'H'},    /* backward compatibility */
                 {"hostname", required_argument, 0, 'H'},
                 {"port", required_argument,0,'p'},
@@ -212,7 +221,7 @@ process_arguments (int argc, char **argv)
                         strcpy (argv[c], "-t");
 
         while (1) {
-                c = getopt_long (argc, argv, "Vvh1246fqt:H:O:p:i:u:l:C:S::E::n:s:o:F:", longopts,
+                c = getopt_long (argc, argv, "Vvh1246fqt:UH:O:p:i:u:l:C:S::E::n:s:o:F:", longopts,
                                  &option);
 
                 if (c == -1 || c == EOF)
@@ -234,6 +243,9 @@ process_arguments (int argc, char **argv)
                         else
                                 timeout_interval = atoi (optarg);
                         break;
+                case 'U':
+                        unknown_timeout = TRUE;
+                        break;
                 case 'H':                                                                       /* host */
                         hostname = optarg;
                         break;
@@ -445,6 +457,8 @@ print_help (void)
   printf ("    %s\n", _("Tell ssh to suppress warning and diagnostic messages [optional]"));
         printf (UT_WARN_CRIT);
         printf (UT_CONN_TIMEOUT, DEFAULT_SOCKET_TIMEOUT);
+        printf (" %s\n","-U, --unknown-timeout");
+        printf ("    %s\n", _("Make connection problems return UNKNOWN instead of CRITICAL"));
         printf (UT_VERBOSE);
         printf("\n");
   printf (" %s\n", _("The most common mode of use is to refer to a local identity file with"));
@@ -474,7 +488,7 @@ void
 print_usage (void)
 {
         printf ("%s\n", _("Usage:"));
-        printf (" %s -H <host> -C <command> [-fqv] [-1|-2] [-4|-6]\n"
+        printf (" %s -H <host> -C <command> [-fqvU] [-1|-2] [-4|-6]\n"
                 "       [-S [lines]] [-E [lines]] [-W] [-t timeout] [-i identity]\n"
                 "       [-l user] [-n name] [-s servicelist] [-O outputfile]\n"
                 "       [-p port] [-o ssh-option] [-F configfile]\n",