imtcp: TCP Syslog Input Module
==============================

Provides the ability to receive syslog messages via TCP. Encryption is
natively provided by selecting the approprioate network stream driver
and can also be provided by using `stunnel <rsyslog_stunnel.html>`_ (an
alternative is the use the `imgssapi <imgssapi.html>`_ module).

**Author:**\ Rainer Gerhards <rgerhards@adiscon.com>

Configuration Parameters
------------------------

Module Parameters
^^^^^^^^^^^^^^^^^

Note: parameter names are case-insensitive.

.. function:: AddtlFrameDelimiter <Delimiter>

   This directive permits to specify an additional frame delimiter for
   Multiple receivers may be configured by specifying $InputTCPServerRun
   multiple times. This is available since version 4.3.1, earlier
   versions do NOT support it.

.. function:: DisableLFDelimiter on/off

   *Default is off*

   Industry-strandard plain text tcp syslog uses the LF to delimit
   syslog frames. However, some users brought up the case that it may be
   useful to define a different delimiter and totally disable LF as a
   delimiter (the use case named were multi-line messages). This mode is
   non-standard and will probably come with a lot of problems. However,
   as there is need for it and it is relatively easy to support, we do
   so. Be sure to turn this setting to "on" only if you exactly know
   what you are doing. You may run into all sorts of troubles, so be
   prepared to wrangle with that!

.. function:: maxFrameSize <int>

   *Default: 200000; Max: 200000000*

   When in octet counted mode, the frame size is given at the beginning
   of the message. With this parameter the max size this frame can have
   is specified and when the frame gets to large the mode is switched to
   octet stuffing.
   The max value this parameter can have was specified because otherwise
   the integer could become negative and this would result in a
   Segmentation Fault.

.. function:: NotifyOnConnectionClose on/off

   *Default is off*

   Instructs imtcp to emit a message if the remote peer closes a
   connection.

   **Important:** This directive is global to all listeners and must be
   given right after loading imtcp, otherwise it may have no effect.

.. function:: KeepAlive on/off

   *Default is off*

   enable of disable keep-alive packets at the tcp socket layer. The
   default is to disable them.

.. function:: KeepAlive.Probes <number>

   The number of unacknowledged probes to send before considering the
   connection dead and notifying the application layer. The default, 0,
   means that the operating system defaults are used. This has only
   effect if keep-alive is enabled. The functionality may not be
   available on all platforms.

.. function:: KeepAlive.Interval <number>

   The interval between subsequential keepalive probes, regardless of
   what the connection has exchanged in the meantime. The default, 0,
   means that the operating system defaults are used. This has only
   effect if keep-alive is enabled. The functionality may not be
   available on all platforms.

.. function:: KeepAlive.Time <number>

   The interval between the last data packet sent (simple ACKs are not
   considered data) and the first keepalive probe; after the connection
   is marked to need keepalive, this counter is not used any further.
   The default, 0, means that the operating system defaults are used.
   This has only effect if keep-alive is enabled. The functionality may
   not be available on all platforms.

.. function:: FlowControl on/off

   *Default is on*

   This setting specifies whether some message flow control shall be
   exercised on the related TCP input. If set to on, messages are
   handled as "light delayable", which means the sender is throttled a
   bit when the queue becomes near-full. This is done in order to
   preserve some queue space for inputs that can not throttle (like
   UDP), but it may have some undesired effect in some configurations.
   Still, we consider this as a useful setting and thus it is the
   default. To turn the handling off, simply configure that explicitely.

.. function:: MaxListeners <number>

   *Default is 20*

   Sets the maximum number of listeners (server ports) supported.
   This must be set before the first $InputTCPServerRun directive.

.. function:: MaxSessions <number>

   *Default is 200*

   Sets the maximum number of sessions supported. This must be set
   before the first $InputTCPServerRun directive

.. function:: StreamDriver.Name <string>

   Selects :doc:`network stream driver <../../concepts/netstrm_drvr>`
   for all inputs using this module.

.. function:: StreamDriver.Mode <number>

   Sets the driver mode for the currently selected
   :doc:`network stream driver <../../concepts/netstrm_drvr>`.
   <number> is driver specific.

.. function:: StreamDriver.AuthMode <mode-string>

   Sets permitted peer IDs. Only these peers are able to connect to
   the listener. <id-string> semantics depend on the currently
   selected AuthMode and
   :doc:`network stream driver <../../concepts/netstrm_drvr>`.
   PermittedPeers may not be set in anonymous modes.

.. function:: PermittedPeer <id-string>

   Sets permitted peer IDs. Only these peers are able to connect to
   the listener. <id-string> semantics depend on the currently
   selected AuthMode and
   :doc:`network stream driver <../../concepts/netstrm_drvr>`.
   PermittedPeer may not be set in anonymous modes. PermittedPeer may
   be set either to a single peer or an array of peers either of type
   IP or name, depending on the tls certificate.

   Single peer: PermittedPeer="127.0.0.1"

   Array of peers:
   PermittedPeer=["test1.example.net","10.1.2.3","test2.example.net","..."]

.. function:: discardTruncatedMsg on/off

   *Default is off*

   Normally when a message is truncated in octet stuffing mode the part that
   is cut off is processed as the next message. When this parameter is activated,
   the part that is cut off after a truncation is discarded and not processed.

.. function:: gnutlsPriorityString <string>

   *Default is NULL*

   *Available since 8.29.0*

   The GnuTLS priority strings specify the TLS session's handshake algorithms and
   options. These strings are intended as a user-specified override of the library
   defaults. If this parameter is NULL, the default settings are used. More
   information about priority Strings
   `here <https://gnutls.org/manual/html_node/Priority-Strings.html>`_.

Input Parameters
^^^^^^^^^^^^^^^^

Note: parameter names are case-insensitive.

.. function:: Port <port>

   Starts a TCP server on selected port

.. function:: address <name>

   *Default: all interfaces*

   On multi-homed machines, specifies to which local address the
   listerner should be bound.

.. function:: Name <name>

   Sets a name for the inputname property. If no name is set "imtcp" is
   used by default. Setting a name is not strictly necessary, but can be
   useful to apply filtering based on which input the message was
   received from.

.. function:: Ruleset <ruleset>

   Binds the listener to a specific :doc:`ruleset <../../concepts/multi_ruleset>`.

.. function:: SupportOctetCountedFraming on/off

   *Default is on*

   If set to "on", the legacy octed-counted framing (similar to RFC5425
   framing) is activated. This should be left unchanged until you know
   very well what you do. It may be useful to turn it off, if you know
   this framing is not used and some senders emit multi-line messages
   into the message stream.

.. function:: RateLimit.Interval [number]

   Specifies the rate-limiting interval in seconds. Default value is 0,
   which turns off rate limiting. Set it to a number of seconds (5
   recommended) to activate rate-limiting.

.. function:: RateLimit.Burst [number]

   Specifies the rate-limiting burst in number of messages. Default is
   10,000.

Statistic Counter
-----------------

This plugin maintains :doc:`statistics <../rsyslog_statistic_counter>` for each listener. The statistic is named
after the given input name (or "imtcp" if none is configured), followed by
the listener port in parenthesis. For example, the counter for a listener
on port 514 with no set name is called "imtcp(514)".

The following properties are maintained for each listener:

-  **submitted** - total number of messages submitted for processing since startup

Caveats/Known Bugs
------------------

-  module always binds to all interfaces
-  can not be loaded together with `imgssapi <imgssapi.html>`_ (which
   includes the functionality of imtcp)

See also
--------

- `rsyslog video tutorial on how to store remote messages in a separate file <http://www.rsyslog.com/howto-store-remote-messages-in-a-separate-file/>`_ (for legacy syntax, but you get the idea).

Example
-------

This sets up a TCP server on port 514 and permits it to accept up to 500
connections:

::

  module(load="imtcp" MaxSessions="500")
  input(type="imtcp" port="514")

Note that the global parameters (here: max sessions) need to be set when
the module is loaded. Otherwise, the parameters will not apply.

Legacy Configuration Directives
-------------------------------

.. function:: $InputTCPServerAddtlFrameDelimiter <Delimiter>

   equivalent to: AddtlFrameDelimiter

.. function:: $InputTCPServerDisableLFDelimiter on/off

   equivalent to: DisableLFDelimiter

.. function:: $InputTCPServerNotifyOnConnectionClose on/off

   equivalent to: NotifyOnConnectionClose

.. function:: $InputTCPServerKeepAlive** <on/**off**>

   equivalent to: KeepAlive

.. function:: $InputTCPServerKeepAlive\_probes <number>

   Equivalent to: KeepAlive.Probes

.. function:: $InputTCPServerKeepAlive\_intvl <number>

   Equivalent to: KeepAlive.Interval

.. function:: $InputTCPServerKeepAlive\_time <number>

   Equivalent to: KeepAlive.Time

.. function:: $InputTCPServerRun <port>

   equivalent to: Port

.. function:: $InputTCPFlowControl on/off

   equivalent to: FlowControl

.. function:: $InputTCPMaxListeners <number>

   equivalent to: MaxListeners

.. function:: $InputTCPMaxSessions <number>

   equivalent to: MaxSessions

.. function:: $InputTCPServerStreamDriverMode <number>

   equivalent to: StreamDriver.Mode

.. function:: $InputTCPServerInputName <name>

   equivalent to: Name

.. function:: $InputTCPServerStreamDriverAuthMode <mode-string>

   equivalent to: StreamDriver.AuthMode

.. function:: $InputTCPServerStreamDriverPermittedPeer <id-string>

   equivalent to: PermittedPeer.

.. function:: $InputTCPServerBindRuleset <ruleset>

   equivalent to: Ruleset.

.. function:: $InputTCPSupportOctetCountedFraming on/off

   equivalent to: SupportOctetCountedFraming

Caveats/Known Bugs
------------------

-  module always binds to all interfaces
-  can not be loaded together with `imgssapi <imgssapi.html>`_ (which
   includes the functionality of imtcp)
-  increasing MaxSessions and MaxListeners doesn't change MaxOpenFiles,
   consider increasing this global configuration parameter too (on Linux
   check the actual value for running process by in /proc/PID/limits; default
   limit on Linux is 1024)

Example
-------

This sets up a TCP server on port 514 and permits it to accept up to 500
connections:

::

  $ModLoad imtcp # needs to be done just once
  $InputTCPMaxSessions 500
  $InputTCPServerRun 514

Note that the parameters (here: max sessions) need to be set **before**
the listener is activated. Otherwise, the parameters will not apply.
