Handling of multiline output in checks via LiveStatus

[llange]

As described in naemon/naemon-core#387, outputs (from passive checks) submitted through LiveStatus were not properly processed, in that the whole output was assigned to plugin_output regardless of whether it had multiple lines - or not.

The main reason is that LiveStatus being a line-oriented protocol, it was not easy to submit outputs with a linefeed \n in them - as this would truncate the line at the \n boundary.

This PR intends to fix that, by allowing an escaped syntax for linefeed : \\n (and other control characters) when processing output submitted via LiveStatus. (This was the behaviour of Nagios 3.x - but the implementation may differ).

This PR works by introducing a new unescape_newlines function shamelessly stolen from Nagios, that will convert \\n (or any \\X control characters) to their proper value.

A test scenario has been written to validate and protect against possible future regression.

Example:

echo "COMMAND [$(date +%s)] PROCESS_SERVICE_CHECK_RESULT;HOST;SERVICE;0;A short output\\nFirst line of long output\\nSecond line of long output" | unixcat /var/spool/nagios/rw/live

[sni]

I'd rather not use code from nagios tbh. Haven't looked into their licenses lately, but i doubt it is compatibly with open source anymore. Besides that, it looks good. Bonus points for the test case :1st_place_medal:

[llange]

Hi, I understand your concern, but I double-checked the license first to be extra sure it would be compatible withe the GPL-2 of naemon-livestatus :

1) The file is : https://github.com/NagiosEnterprises/nagioscore/blob/master/cgi/cgiutils.c and the license in the header is GPL-2:

 *
 * CGIUTILS.C - Common utilities for Nagios CGIs
 *
 *
 * License:
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

2) Additionally the repo https://github.com/NagiosEnterprises/nagioscore states in the README file the following:

Nagios is a host/service/network monitoring program written in C and released under the GNU General Public License, version 2

3) And last the LICENSE file (21 yr old !!!) for the whole repo is the proper GPL-2.

However, if you so prefer, I can craft another implementation.

[sni]

alright, then my only remark is to please move the source reference into the git commit message instead of the code.

[llange]

Done, thanks for your review.

[sni]

great, thanks