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/******************************************************************************
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* Program: SMTP plugin for Nagios
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* Copyright (c) 1999 Ethan Galstad (nagios@nagios.org)
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* $Id: check_smtp.c,v 1.9.2.2 2003/03/07 07:15:40 kdebisschop Exp $
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* This plugin will attempt to open an SMTP connection with the host.
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* Successul connects return STATE_OK, refusals and timeouts return
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* STATE_CRITICAL, other errors return STATE_UNKNOWN. Successful
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* connects, but incorrect reponse messages from the host result in
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* STATE_WARNING return values.
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* License Information:
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*****************************************************************************/
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const char *progname = "check_smtp";
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#define SMTP_EXPECT "220"
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#define SMTP_HELO "HELO "
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/* sendmail will syslog a "NOQUEUE" error if session does not attempt
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* to do something useful. This can be prevented by giving a command
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* even if syntax is illegal (MAIL requires a FROM:<...> argument)
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* You can disable sending DUMMYCMD by undefining SMTP_USE_DUMMYCMD.
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* According to rfc821 you can include a null reversepath in the from command
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* - but a log message is generated on the smtp server.
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* Use the -f option to provide a FROM address
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#define SMTP_DUMMYCMD "MAIL "
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#define SMTP_USE_DUMMYCMD 1
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#define SMTP_QUIT "QUIT\r\n"
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int process_arguments (int, char **);
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int validate_arguments (void);
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void print_help (void);
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void print_usage (void);
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int server_port = SMTP_PORT;
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char *server_address = NULL;
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char *server_expect = NULL;
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int check_warning_time = FALSE;
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int critical_time = 0;
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int check_critical_time = FALSE;
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main (int argc, char **argv)
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int result = STATE_UNKNOWN;
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char buffer[MAX_INPUT_BUFFER] = "";
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char *from_str = NULL;
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if (process_arguments (argc, argv) != OK)
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usage ("Invalid command arguments supplied\n");
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/* initialize the HELO command with the localhostname */
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#ifndef HOST_MAX_BYTES
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#define HOST_MAX_BYTES 255
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helocmd = malloc (HOST_MAX_BYTES);
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gethostname(helocmd, HOST_MAX_BYTES);
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asprintf (&helocmd, "%s%s%s", SMTP_HELO, helocmd, "\r\n");
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/* initialize the MAIL command with optional FROM command */
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asprintf (&from_str, "%sFROM: %s%s", SMTP_DUMMYCMD, from_arg, "\r\n");
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printf ("FROMCMD: %s\n", from_str);
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/* initialize alarm signal handling */
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signal (SIGALRM, socket_timeout_alarm_handler);
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/* set socket timeout */
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alarm (socket_timeout);
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/* try to connect to the host at the given port number */
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result = my_tcp_connect (server_address, server_port, &sd);
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/* we connected, so close connection before exiting */
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if (result == STATE_OK) {
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/* watch for the SMTP connection string and */
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/* return a WARNING status if we couldn't read any data */
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if (recv (sd, buffer, MAX_INPUT_BUFFER - 1, 0) == -1) {
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printf ("recv() failed\n");
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result = STATE_WARNING;
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/* strip the buffer of carriage returns */
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/* make sure we find the response we are looking for */
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if (!strstr (buffer, server_expect)) {
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if (server_port == SMTP_PORT)
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printf ("Invalid SMTP response received from host\n");
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printf ("Invalid SMTP response received from host on port %d\n",
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result = STATE_WARNING;
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/* send the HELO command */
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send(sd, helocmd, strlen(helocmd), 0);
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/* allow for response to helo command to reach us */
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recv(sd, buffer, MAX_INPUT_BUFFER-1, 0);
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#ifdef SMTP_USE_DUMMYCMD
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send(sd, from_str, strlen(from_str), 0);
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/* allow for response to DUMMYCMD to reach us */
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recv(sd, buffer, MAX_INPUT_BUFFER-1, 0);
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printf("DUMMYCMD: %s\n%s\n",from_str,buffer);
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#endif /* SMTP_USE_DUMMYCMD */
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/* tell the server we're done */
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send (sd, SMTP_QUIT, strlen (SMTP_QUIT), 0);
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/* finally close the connection */
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/* reset the alarm */
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if (check_critical_time == TRUE && (end_time - start_time) > critical_time)
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result = STATE_CRITICAL;
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else if (check_warning_time == TRUE && (end_time - start_time) > warning_time)
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result = STATE_WARNING;
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printf ("SMTP %s - %d sec. response time, %s\n",
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state_text (result), (int) (end_time - start_time), buffer);
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printf ("SMTP %s - %d second response time\n", state_text (result), (int) (end_time - start_time));
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/* process command-line arguments */
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process_arguments (int argc, char **argv)
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int option_index = 0;
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static struct option long_options[] = {
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{"hostname", required_argument, 0, 'H'},
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{"expect", required_argument, 0, 'e'},
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{"critical", required_argument, 0, 'c'},
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{"warning", required_argument, 0, 'w'},
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{"port", required_argument, 0, 'p'},
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{"from", required_argument, 0, 'f'},
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{"verbose", no_argument, 0, 'v'},
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{"version", no_argument, 0, 'V'},
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{"help", no_argument, 0, 'h'},
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for (c = 1; c < argc; c++) {
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if (strcmp ("-to", argv[c]) == 0)
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strcpy (argv[c], "-t");
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else if (strcmp ("-wt", argv[c]) == 0)
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strcpy (argv[c], "-w");
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else if (strcmp ("-ct", argv[c]) == 0)
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strcpy (argv[c], "-c");
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getopt_long (argc, argv, "+hVvt:p:f:e:c:w:H:", long_options,
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c = getopt (argc, argv, "+?hVvt:p:f:e:c:w:H:");
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if (c == -1 || c == EOF)
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case 'H': /* hostname */
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if (is_host (optarg)) {
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server_address = optarg;
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usage ("Invalid host name\n");
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if (is_intpos (optarg)) {
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server_port = atoi (optarg);
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usage ("Server port must be a positive integer\n");
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case 'f': /* from argument */
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case 'e': /* server expect string on 220 */
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server_expect = optarg;
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case 'c': /* critical time threshold */
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if (is_intnonneg (optarg)) {
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critical_time = atoi (optarg);
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check_critical_time = TRUE;
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usage ("Critical time must be a nonnegative integer\n");
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case 'w': /* warning time threshold */
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if (is_intnonneg (optarg)) {
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warning_time = atoi (optarg);
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check_warning_time = TRUE;
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usage ("Warning time must be a nonnegative integer\n");
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case 'v': /* verbose */
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case 't': /* timeout */
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if (is_intnonneg (optarg)) {
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socket_timeout = atoi (optarg);
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usage ("Time interval must be a nonnegative integer\n");
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case 'V': /* version */
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print_revision (progname, "$Revision: 1.9.2.2 $");
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usage ("Invalid argument\n");
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if (server_address == NULL) {
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if (is_host (argv[c]))
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server_address = argv[c];
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usage ("Invalid host name");
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asprintf (&server_address, "127.0.0.1");
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if (server_expect == NULL)
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asprintf (&server_expect, SMTP_EXPECT);
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return validate_arguments ();
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validate_arguments (void)
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print_revision (progname, "$Revision: 1.9.2.2 $");
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("Copyright (c) 2000 Ethan Galstad/Karl DeBisschop\n\n"
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"This plugin test the SMTP service on the specified host.\n\n");
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" -H, --hostname=STRING or IPADDRESS\n"
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" Check server on the indicated host\n"
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" -p, --port=INTEGER\n"
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" Make connection on the indicated port (default: %d)\n"
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" -e, --expect=STRING\n"
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" String to expect in first line of server response (default: %s)\n"
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" -f, --from=STRING\n"
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" from address to include in MAIL command (default NULL, Exchange2000 requires one)\n"
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" -w, --warning=INTEGER\n"
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" Seconds necessary to result in a warning status\n"
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" -c, --critical=INTEGER\n"
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" Seconds necessary to result in a critical status\n"
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" -t, --timeout=INTEGER\n"
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" Seconds before connection attempt times out (default: %d)\n"
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" Print extra information (command-line use only)\n"
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" Print detailed help screen\n"
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" Print version information\n\n",
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SMTP_PORT, SMTP_EXPECT, DEFAULT_SOCKET_TIMEOUT);
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("Usage: %s -H host [-e expect] [-p port] [-f from addr] [-w warn] [-c crit] [-t timeout] [-v]\n"
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" %s --version\n", progname, progname, progname);
added
removed
plugins/check_smtp.c
