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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html><head>
<meta http-equiv="Content-Language" content="en"><title>RELP Output Module (omrelp)</title>
</head>
<body>
<a href="rsyslog_conf_modules.html">back to rsyslog module documentation</a>
<h1>RELP Output Module (omrelp)</h1>
<p><b>Module Name: omrelp</b></p>
<p><b>Author: </b>Rainer Gerhards
<rgerhards@adiscon.com></p>
<p><b>Description</b>:</p>
<p>This module supports sending syslog messages over the reliable
RELP protocol. For RELP's advantages over plain tcp syslog, please see
the documentation for <a href="imrelp.html">imrelp</a>
(the server counterpart). </p>
<span style="font-weight: bold;">Setup</span>
<p>Please note that <a href="http://www.librelp.com">librelp</a>
is required for imrelp (it provides the core relp protocol
implementation).</p>
<p><b>Action Configuration Parameters</b>:</p>
<p>This module supports RainerScript configuration starting with
rsyslog 7.3.10. For older versions, legacy configuration directives
must be used.
<ul>
<li><b>target</b> (mandatory)<br>
The target server to connect to.
</li>
<li><b>template</b> (not mandatory, default "RSYSLOG_ForwardFormat")<br>
Defines the template to be used for the output.
</li>
<li><b>timeout</b> (not mandatory, default 90)<br>
Timeout for relp sessions. If set too low, valid sessions
may be considered dead and tried to recover.
</li>
<li><b>windowSize</b> (not mandatory, default 0)<br>
This is an <b>expert parameter</b>. It permits to override the
RELP window size being used by the client. Changing the window
size has both an effect on performance as well as potential
message duplication in failure case. A larger window size means
more performance, but also potentially more duplicated
messages - and vice versa. The default 0 means that librelp's
default window size is being used, which is considered a
compromise between goals reached. For your information:
at the time of this writing, the librelp default window size
is 128 messages, but this may change at any time.
<br>Note that there is no equivalent server parameter, as the
client proposes and manages the window size in RELP protocol.
<li><b>tls</b> (not mandatory, values "on","off", default "off")<br>
If set to "on", the RELP connection will be encrypted by TLS, so that the data is protected against observers. Please note that both the client and the server must have set TLS to either "on" or "off". Other combinations lead to unpredictable results.
</li>
<li><b>tls.compression</b> (not mandatory, values "on","off", default "off")<br>
The controls if the TLS stream should be compressed (zipped). While this
increases CPU use, the network bandwidth should be reduced. Note that
typical text-based log records usually compress rather well.
</li>
<li><b>tls.permittedPeer</b> peer</br>
Places access restrictions on this forwarder. Only peers which
have been listed in this parameter may be connected to.
This guards against rouge servers and man-in-the-middle
attacks. The validation
bases on the certficate the remote peer presents.<br>
The <i>peer</i> parameter lists permitted certificate
fingerprints. Note that it is an array parameter, so either
a single or multiple fingerprints can be listed. When a
non-permitted peer is connected to, the refusal is logged together
with it's fingerprint. So if the administrator knows this was
a valid request, he can simple add the fingerprint by copy and
paste from the logfile to rsyslog.conf. It must be noted, though,
that this situation should usually not happen after initial
client setup and administrators should be alert in this case.
<br>Note that usually a single remote peer should be all that
is ever needed. Support for multiple peers is primarily included
in support of load balancing scenarios. If the connection
goes to a specific server, only one specific certificate is ever
expected (just like when connecting to a specific ssh server).
<br>To specify multiple fingerprints, just enclose them
in braces like this:
<br>tls.permittedPeer=["SHA1:...1", "SHA1:....2"]
<br>To specify just a single peer, you can either
specify the string directly or enclose it in braces.
</li>
<li><b>tls.authMode</b> mode</br>
Sets the mode used for mutual authentication. Supported values are
either "<i>fingerprint</i>" or "<i>name"</i>.
<br>Fingerprint mode basically is what SSH
does. It does not require a full PKI to be present, instead self-signed
certs can be used on all peers. Even if a CA certificate is given, the
validity of the peer cert is NOT verified against it. Only the
certificate fingerprint counts.
<br>In "name" mode, certificate validation happens. Here, the matching
is done against the certificate's subjectAltName and, as a fallback,
the subject common name. If the certificate contains multiple names,
a match on any one of these names is considered good and permits the
peer to talk to rsyslog.
<li><b>tls.prioritystring</b> (not mandatory, string)<br>
This parameter permits to specify the so-called "priority string" to
GnuTLS. This string gives complete control over all crypto parameters,
including compression setting. For this reason, when the prioritystring
is specified, the "tls.compression" parameter has no effect and is
ignored.
<br>Full information about how to construct a priority string can be
found in the GnuTLS manual. At the time of this writing, this
information was contained in
<a href="http://gnutls.org/manual/html_node/Priority-Strings.html">section 6.10 of the GnuTLS manual</a>.
<br><b>Note: this is an expert parameter.</b> Do not use if you do
not exactly know what you are doing.
</li>
</ul>
<p><b>Sample:</b></p>
<p>The following sample sends all messages to the central server
"centralserv" at port 2514 (note that that server must run imrelp on
port 2514).
</p>
<textarea rows="3" cols="60">module(load="omrelp")
action(type="omrelp" target="centralserv" port="2514")
</textarea>
<p><b>Legacy Configuration Directives</b>:</p>
<p>This module uses old-style action configuration to keep
consistent with the forwarding rule. So far, no additional
configuration directives can be specified. To send a message via RELP,
use</p>
<p>*.*
:omrelp:<sever>:<port>;<template></p>
<p>just as you use </p>
<p>*.*
@@<sever>:<port>;<template></p>
<p>to forward a message via plain tcp syslog.</p>
<b>Caveats/Known Bugs:</b>
<p>See <a href="imrelp.html">imrelp</a>,
which documents them. </p>
<p><b>Legacy Sample:</b></p>
<p>The following sample sends all messages to the central server
"centralserv" at port 2514 (note that that server must run imrelp on
port 2514).
</p>
<textarea rows="3" cols="60">$ModLoad omrelp
*.* :omrelp:centralserv:2514
</textarea>
<p>Note: to use IPv6 addresses, encode them in [::1] format.
<p>[<a href="rsyslog_conf.html">rsyslog.conf overview</a>]
[<a href="manual.html">manual index</a>] [<a href="http://www.rsyslog.com/">rsyslog site</a>]</p>
<p><font size="2">This documentation is part of the
<a href="http://www.rsyslog.com/">rsyslog</a>
project.<br>
Copyright © 2008 by <a href="http://www.gerhards.net/rainer">Rainer
Gerhards</a> and
<a href="http://www.adiscon.com/">Adiscon</a>.
Released under the GNU GPL version 3 or higher.</font></p>
</body></html>
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