syslog-ng Open Source Edition 3.18 - Administration Guide

network() destination options

The network() driver sends messages to a remote host (for example a syslog-ng server or relay) on the local intranet or internet using the RFC3164 syslog protocol (for details about the protocol, see BSD-syslog or legacy-syslog messages). The network() driver supports sending messages using the UDP, TCP, or the encrypted TLS networking protocols.

These destinations have the following options:

disk-buffer()

Description: This option enables putting outgoing messages into the disk buffer of the destination to avoid message loss in case of a system failure on the destination side. It has the following options:

Options reliable() and disk-buf-size() are required options.

destination d_demo {
    network(
        "127.0.0.1"
        port(3333)
        disk-buffer(
            mem-buf-size(10000)
            disk-buf-size(2000000)
            reliable(yes)
            dir("/tmp/disk-buffer")
        )
    );
};

destination d_demo {
    network(
        "127.0.0.1"
        port(3333)
           disk-buffer(
            mem-buf-length(10000)
            disk-buf-size(2000000)
            reliable(no)
            dir("/tmp/disk-buffer")
        )
    );
};

failover()

Description: Available only in syslog-ng Open Source Edition version 3.17 and later. For details about how client-side failover works, see Client-side failover.

flags()

Description: Flags influence the behavior of the destination driver.

• no-multi-line: The no-multi-line flag disables line-breaking in the messages: the entire message is converted to a single line.

• syslog-protocol: The syslog-protocol flag instructs the driver to format the messages according to the new IETF syslog protocol standard (RFC5424), but without the frame header. If this flag is enabled, macros used for the message have effect only for the text of the message, the message header is formatted to the new standard. Note that this flag is not needed for the syslog driver, and that the syslog driver automatically adds the frame header to the messages.

flush-lines()

Description: Specifies how many lines are flushed to a destination at a time. The syslog-ng OSE application waits for this number of lines to accumulate and sends them off in a single batch. Increasing this number increases throughput as more messages are sent in a single batch, but also increases message latency.

The syslog-ng OSE application flushes the messages if it has sent flush-lines() number of messages, or the queue became empty. If you stop or reload syslog-ng OSE or in case of network sources, the connection with the client is closed, syslog-ng OSE automatically sends the unsent messages to the destination.

For optimal performance when sending messages to an syslog-ng OSE server, make sure that the flush-lines() is smaller than the window size set using the log-iw-size() option in the source of your server.

frac-digits()

Description: The syslog-ng application can store fractions of a second in the timestamps according to the ISO8601 format. The frac-digits() parameter specifies the number of digits stored. The digits storing the fractions are padded by zeros if the original timestamp of the message specifies only seconds. Fractions can always be stored for the time the message was received. Note that syslog-ng can add the fractions to non-ISO8601 timestamps as well.

hook-commands()

Description: This option makes it possible to execute external programs when the relevant driver is initialized or torn down. The hook-commands() can be used with all source and destination drivers with the exception of the usertty() and internal() drivers.

Using the hook-commands() when syslog-ng OSE starts or stops

To execute an external program when syslog-ng OSE starts or stops, use the following options:

Using the hook-commands() when syslog-ng OSE reloads

To execute an external program when the syslog-ng OSE configuration is initiated or torn down, for example, on startup/shutdown or during a syslog-ng OSE reload, use the following options:

source {
   network(transport(udp)
	hook-commands(
          startup("iptables -I LOGCHAIN 1 -p udp --dport 514 -j ACCEPT")
          shutdown("iptables -D LOGCHAIN 1")
        )
     );
};

ip-protocol()

Description: Determines the internet protocol version of the given driver (network() or syslog()). The possible values are 4 and 6, corresponding to IPv4 and IPv6. The default value is ip-protocol(4).

Note that listening on a port using IPv6 automatically means that you are also listening on that port using IPv4. That is, if you want to have receive messages on an IP-address/port pair using both IPv4 and IPv6, create a source that uses the ip-protocol(6). You cannot have two sources with the same IP-address/port pair, but with different ip-protocol() settings (it causes an Address already in use error).

For example, the following source receives messages on TCP, using the network() driver, on every available interface of the host on both IPv4 and IPv6.

source s_network_tcp { network( transport("tcp") ip("::") ip-protocol(6) port(601) ); };

ip-tos()

Description: Specifies the Type-of-Service value of outgoing packets.

ip-ttl()

Description: Specifies the Time-To-Live value of outgoing packets.

keep-alive()

Description: Specifies whether connections to destinations should be closed when syslog-ng is reloaded. Note that this applies to the client (destination) side of the syslog-ng connections, server-side (source) connections are always reopened after receiving a HUP signal unless the keep-alive option is enabled for the source.

localip()

Description: The IP address to bind to before connecting to target.

localport()

Description: The port number to bind to. Messages are sent from this port.

log-fifo-size()

Description: The number of messages that the output queue can store.

mark-freq()

Description: An alias for the obsolete mark() option, retained for compatibility with syslog-ng version 1.6.x. The number of seconds between two MARK messages. MARK messages are generated when there was no message traffic to inform the receiver that the connection is still alive. If set to zero (0), no MARK messages are sent. The mark-freq() can be set for global option and/or every MARK capable destination driver if mark-mode() is periodical or dst-idle or host-idle. If mark-freq() is not defined in the destination, then the mark-freq() will be inherited from the global options. If the destination uses internal mark-mode(), then the global mark-freq() will be valid (does not matter what mark-freq() set in the destination side).

mark-mode()

Description: The mark-mode() option can be set for the following destination drivers: file(), program(), unix-dgram(), unix-stream(), network(), pipe(), syslog() and in global option.

• internal: When internal mark mode is selected, internal source should be placed in the log path as this mode does not generate mark by itself at the destination. This mode only yields the mark messages from internal source. This is the mode as syslog-ng OSE 3.3 worked. MARK will be generated by internal source if there was NO traffic on local sources:

  file(), pipe(), unix-stream(), unix-dgram(), program()

• dst-idle: Sends MARK signal if there was NO traffic on destination drivers. MARK signal from internal source will be dropped.

  MARK signal can be sent by the following destination drivers: network(), syslog(), program(), file(), pipe(), unix-stream(), unix-dgram().

• host-idle: Sends MARK signal if there was NO local message on destination drivers. For example MARK is generated even if messages were received from tcp. MARK signal from internal source will be dropped.

  MARK signal can be sent by the following destination drivers: network(), syslog(), program(), file(), pipe(), unix-stream(), unix-dgram().

• periodical: Sends MARK signal perodically, regardless of traffic on destination driver. MARK signal from internal source will be dropped.

  MARK signal can be sent by the following destination drivers: network(), syslog(), program(), file(), pipe(), unix-stream(), unix-dgram().

• none: Destination driver drops all MARK messages. If an explicit mark-mode() is not given to the drivers where none is the default value, then none will be used.

• global: Destination driver uses the global mark-mode() setting. Note that setting the global mark-mode() to global causes a syntax error in syslog-ng OSE.

Available in syslog-ng OSE 3.4 and later.

port() or destport()

Description: The port number to connect to. Note that the default port numbers used by syslog-ng do not comply with the latest RFC which was published after the release of syslog-ng 3.0.2, therefore the default port numbers will change in the future releases.

so-broadcast()

Description: This option controls the SO_BROADCAST socket option required to make syslog-ng send messages to a broadcast address. For details, see the socket(7) manual page.

so-keepalive()

Description: Enables keep-alive messages, keeping the socket open. This only effects TCP and UNIX-stream sockets. For details, see the socket(7) manual page.

so-rcvbuf()

Description: Specifies the size of the socket receive buffer in bytes. For details, see the socket(7) manual page.

so-sndbuf()

Description: Specifies the size of the socket send buffer in bytes. For details, see the socket(7) manual page.

spoof-source()

Description: Enables source address spoofing. This means that the host running syslog-ng generates UDP packets with the source IP address matching the original sender of the message. It is useful when you want to perform some kind of preprocessing via syslog-ng then forward messages to your central log management solution with the source address of the original sender. This option only works for UDP destinations though the original message can be received by TCP as well. This option is only available if syslog-ng was compiled using the --enable-spoof-source configuration option.

suppress()

Description: If several identical log messages would be sent to the destination without any other messages between the identical messages (for example, an application repeated an error message ten times), syslog-ng can suppress the repeated messages and send the message only once, followed by the Last message repeated n times. message. The parameter of this option specifies the number of seconds syslog-ng waits for identical messages.

tcp-keepalive-intvl()

Description: Specifies the interval (number of seconds) between subsequential keepalive probes, regardless of the traffic exchanged in the connection. This option is equivalent to /proc/sys/net/ipv4/tcp_keepalive_intvl. The default value is 0, which means using the kernel default.

Available in syslog-ng OSE version 3.4 and later.

tcp-keepalive-probes()

Description: Specifies the number of unacknowledged probes to send before considering the connection dead. This option is equivalent to /proc/sys/net/ipv4/tcp_keepalive_probes. The default value is 0, which means using the kernel default.

Available in syslog-ng OSE version 3.4 and later.

tcp-keepalive-time()

Description: Specifies the interval (in seconds) between the last data packet sent and the first keepalive probe. This option is equivalent to /proc/sys/net/ipv4/tcp_keepalive_time. The default value is 0, which means using the kernel default.

Available in syslog-ng OSE version 3.4 and later.

template()

Description: Specifies a template defining the logformat to be used in the destination. Macros are described in Macros of syslog-ng OSE. Please note that for network destinations it might not be appropriate to change the template as it changes the on-wire format of the syslog protocol which might not be tolerated by stock syslog receivers (like syslogd or syslog-ng itself). For network destinations make sure the receiver can cope with the custom format defined.

template-escape()

Description: Turns on escaping for the ', ", and backspace characters in templated output files. This is useful for generating SQL statements and quoting string contents so that parts of the log message are not interpreted as commands to the SQL server.

throttle()

Description: Sets the maximum number of messages sent to the destination per second. Use this output-rate-limiting functionality only when using disk-buffer as well to avoid the risk of losing messages. Specifying 0 or a lower value sets the output limit to unlimited.

time-zone()

Description: Convert timestamps to the timezone specified by this option. If this option is not set, then the original timezone information in the message is used. Converting the timezone changes the values of all date-related macros derived from the timestamp, for example, HOUR. For the complete list of such macros, see Date-related macros.

The timezone can be specified by using the name, for example, time-zone("Europe/Budapest")), or as the timezone offset in +/-HH:MM format, for example, +01:00). On Linux and UNIX platforms, the valid timezone names are listed under the /usr/share/zoneinfo directory.

tls()

Description: This option sets various options related to TLS encryption, for example, key/certificate files and trusted CA locations. TLS can be used only with tcp-based transport protocols. For details, see TLS options.

transport()

Description: Specifies the protocol used to send messages to the destination server.

If you use the udp transport, syslog-ng OSE automatically sends multicast packets if a multicast destination address is specified. The tcp transport does not support multicasting.

ts-format()

Description: Override the global timestamp format (set in the global ts-format() parameter) for the specific destination. For details, see ts-format().

osquery: Sending log messages to osquery's syslog table

The osquery() driver sends log messages to osquery's syslog table.

The syslog table contains logs forwarded over a named pipe from syslog-ng. When an osquery process that supports the syslog table starts up, it creates (and properly sets permissions for) a named pipe for syslog-ng to write to.

osqueryi --enable_syslog
         --disable-events=false

osqueryi --enable_syslog
         --disable-events=false
         --database_path=/tmp/osquery.db

osqueryi --enable_syslog
         --disable-events=false
         --database_path=/tmp/osquery.db
         --syslog_pipe_path=/tmp/osq.pipe

@version: 3.12
@include "scl.conf"

source s_net {
  network(port(5514));
};

destination d_osquery {
  # custom pipe path:
  #osquery(pipe("/tmp/osq.pipe"));

  # backup outgoing logs:
  #osquery(file("/var/log/osquery_inserts.log" template(t_osquery)));

  # defaults
  osquery();
};

log {
 source(s_net);
 destination(d_osquery);
 flags(flow-control);
};

osquery() destination options

The osquery() destination has the following options:

file()

Description: Specifies a path to the file where log messages are stored, for example, for debug purposes.

Specifying this option is optional. However, when you start losing logs for some reason, then it is recommended to write outgoing log messages to a specified file, in the same format that messages are written to the pipe. You can also use a template() function called t_osquery, which re-formats messages so they comply with the text-based protocol that osquery accepts.

hook-commands()

Description: This option makes it possible to execute external programs when the relevant driver is initialized or torn down. The hook-commands() can be used with all source and destination drivers with the exception of the usertty() and internal() drivers.

Using the hook-commands() when syslog-ng OSE starts or stops

To execute an external program when syslog-ng OSE starts or stops, use the following options:

Using the hook-commands() when syslog-ng OSE reloads

To execute an external program when the syslog-ng OSE configuration is initiated or torn down, for example, on startup/shutdown or during a syslog-ng OSE reload, use the following options:

source {
   network(transport(udp)
	hook-commands(
          startup("iptables -I LOGCHAIN 1 -p udp --dport 514 -j ACCEPT")
          shutdown("iptables -D LOGCHAIN 1")
        )
     );
};

pipe()

Description: Specifies a custom path to the named pipe that acts as the interface between osquery and syslog-ng. (The default path is set in the SCL file.)

Specifying this option is optional.

pipe: Sending messages to named pipes

The pipe() driver sends messages to a named pipe like /dev/xconsole.

The pipe driver has a single required parameter, specifying the filename of the pipe to open. The filename can include macros. For the list of available optional parameters, see pipe() destination options.

Declaration:

pipe(filename);

destination d_pipe { pipe("/dev/xconsole"); };