omrelp: RELP Output Module

Module Name:	omrelp
Author:	Rainer Gerhards <rgerhards@adiscon.com>

Purpose

This module supports sending syslog messages over the reliable RELP protocol. For RELP’s advantages over plain tcp syslog, please see the documentation for imrelp (the server counterpart).

Setup

Please note that librelp is required for imrelp (it provides the core relp protocol implementation).

Configuration Parameters

Note

Parameter names are case-insensitive; camelCase is recommended for readability.

Module Parameters

Parameter	Summary
tls.tlslib	Specifies which TLS library librelp uses for RELP operations.

Action Parameters

Parameter	Summary
Target	Defines the remote server omrelp connects to.
Port	Specifies the TCP port number or service name for the RELP connection.
Template	Selects the output template used to format RELP messages.
Timeout	Sets the RELP session timeout before a connection is considered dead.
Conn.Timeout	Controls how long the socket connection attempt is allowed to take.
RebindInterval	Forces periodic reconnection after a configured number of transmitted messages.
KeepAlive	Enables or disables TCP keep-alive packets for the RELP connection.
KeepAlive.Probes	Sets how many keepalive probes are sent before a connection is deemed dead.
KeepAlive.Interval	Configures the time between successive TCP keepalive probes.
KeepAlive.Time	Specifies the idle time before the first TCP keepalive probe is sent.
WindowSize	Overrides the RELP client window size used for message transmission.
TLS	Enables TLS encryption for the RELP connection.
TLS.Compression	Controls whether the TLS stream is compressed.
TLS.PermittedPeer	Restricts which peers may connect based on expected names or fingerprints.
TLS.AuthMode	Chooses the mutual authentication mode (fingerprint or name) for TLS.
TLS.CaCert	Specifies the CA certificate used to verify peer certificates.
TLS.MyCert	Provides the path to the machine’s public certificate.
TLS.MyPrivKey	Specifies the path to the machine’s private key for TLS.
TLS.PriorityString	Passes a custom GnuTLS priority string to control TLS parameters.
tls.tlscfgcmd	Passes OpenSSL configuration commands to librelp when using the OpenSSL TLS backend.
LocalClientIp	Sets the local client IP address used when connecting to the remote log server.

Examples

Sending msgs with omrelp

The following sample sends all messages to the central server “centralserv” at port 2514 (note that the server must run imrelp on port 2514).

module(load="omrelp")
action(type="omrelp" target="centralserv" port="2514")

Sending msgs with omrelp via TLS

This is the same as the previous example but uses TLS (via OpenSSL) for operations.

Certificate files must exist at configured locations. Note that authmode “certvalid” is not very strong - you may want to use a different one for actual deployments. For details, see parameter descriptions.

module(load="omrelp" tls.tlslib="openssl")
action(type="omrelp"
             target="centralserv" port="2514" tls="on"
             tls.cacert="tls-certs/ca.pem"
             tls.mycert="tls-certs/cert.pem"
             tls.myprivkey="tls-certs/key.pem"
             tls.authmode="certvalid"
             tls.permittedpeer="rsyslog")

obsolete legacy directives

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

*.*  :omrelp:<server>:<port>;<template>

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© 2008–2025 Rainer Gerhards and others. Licensed under the Apache License 2.0.