6.14.1. syslog() source options

The syslog() driver has the following options.

encoding()

Type: string
Default:  

Description: Specifies the characterset (encoding, for example UTF-8) of messages using the legacy BSD-syslog protocol. To list the available character sets on a host, execute the iconv -l command. For details on how encoding affects the size of the message, see Section Message size and encoding.

flags()

Type: assume-utf8, empty-lines, expect-hostname, kernel, no-hostname, no-multi-line, no-parse, sanitize-utf8, store-legacy-msghdr, syslog-protocol, validate-utf8
Default: empty set

Description: Specifies the log parsing options of the source.

  • assume-utf8: The assume-utf8 flag assumes that the incoming messages are UTF-8 encoded, but does not verify the encoding. If you explicitly want to validate the UTF-8 encoding of the incoming message, use the validate-utf8 flag.

  • empty-lines: Use the empty-lines flag to keep the empty lines of the messages. By default, syslog-ng OSE removes empty lines automatically.

  • expect-hostname: If the expect-hostname flag is enabled, syslog-ng OSE will assume that the log message contains a hostname and parse the message accordingly. This is the default behavior for TCP sources. Note that pipe sources use the no-hostname flag by default.

  • kernel: The kernel flag makes the source default to the LOG_KERN | LOG_NOTICE priority if not specified otherwise.

  • no-hostname: Enable the no-hostname flag if the log message does not include the hostname of the sender host. That way syslog-ng OSE assumes that the first part of the message header is ${PROGRAM} instead of ${HOST}. For example:

    source s_dell { network(port(2000) flags(no-hostname)); };
  • no-multi-line: The no-multi-line flag disables line-breaking in the messages: the entire message is converted to a single line. Note that this happens only if the underlying transport method actually supports multi-line messages. Currently the file() and pipe() drivers support multi-line messages.

  • no-parse: By default, syslog-ng OSE parses incoming messages as syslog messages. The no-parse flag completely disables syslog message parsing and processes the complete line as the message part of a syslog message. The syslog-ng OSE application will generate a new syslog header (timestamp, host, and so on) automatically and put the entire incoming message into the MESSAGE part of the syslog message (available using the ${MESSAGE} macro). This flag is useful for parsing messages not complying to the syslog format.

    If you are using the flags(no-parse) option, then syslog message parsing is completely disabled, and the entire incoming message is treated as the ${MESSAGE} part of a syslog message. In this case, syslog-ng OSE generates a new syslog header (timestamp, host, and so on) automatically. Note that since flags(no-parse) disables message parsing, it interferes with other flags, for example, disables flags(no-multi-line).

  • dont-store-legacy-msghdr: By default, syslog-ng stores the original incoming header of the log message. This is useful of the original format of a non-syslog-compliant message must be retained (syslog-ng automatically corrects minor header errors, for example, adds a whitespace before msg in the following message: Jan 22 10:06:11 host program:msg). If you do not want to store the original header of the message, enable the dont-store-legacy-msghdr flag.

  • sanitize-utf8: When using the sanitize-utf8 flag, syslog-ng OSE converts non-UTF-8 input to an escaped form, which is valid UTF-8.

  • syslog-protocol: The syslog-protocol flag specifies that incoming messages are expected to be formatted according to the new IETF syslog protocol standard (RFC5424), but without the frame header. Note that this flag is not needed for the syslog driver, which handles only messages that have a frame header.

  • validate-utf8: The validate-utf8 flag enables encoding-verification for messages formatted according to the new IETF syslog standard (for details, see Section 2.8.2, IETF-syslog messages). If theBOM[10]character is missing, but the message is otherwise UTF-8 compliant, syslog-ng automatically adds the BOM character to the message.

host-override()

Type: string
Default:  

Description: Replaces the ${HOST} part of the message with the parameter string.

ip() or localip()

Type: string
Default: 0.0.0.0

Description: The IP address to bind to. By default, syslog-ng OSE listens on every available interface. Note that this is not the address where messages are accepted from.

If you specify a multicast bind address and use the udp transport, syslog-ng OSE automatically joins the necessary multicast group. TCP does not support multicasting.

ip-protocol()

Type: number
Default: 4

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()

Type: number
Default: 0

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

ip-ttl()

Type: number
Default: 0

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

keep-alive()

Type: yes or no
Default: yes

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

keep-hostname()

Type: yes or no
Default: no

Description: Enable or disable hostname rewriting.

  • If enabled (keep-hostname(yes)), syslog-ng OSE assumes that the incoming log message was sent by the host specified in the HOST field of the message.

  • If disabled (keep-hostname(no)), syslog-ng OSE rewrites the HOST field of the message, either to the IP address (if the use-dns() parameter is set to no), or to the hostname (if the use-dns() parameter is set to yes and the IP address can be resolved to a hostname) of the host sending the message to syslog-ng OSE. For details on using name resolution in syslog-ng OSE, see Section 19.3, Using name resolution in syslog-ng.

Note

If the log message does not contain a hostname in its HOST field, syslog-ng OSE automatically adds a hostname to the message.

  • For messages received from the network, this hostname is the address of the host that sent the message (this means the address of the last hop if the message was transferred via a relay).

  • For messages received from the local host, syslog-ng OSE adds the name of the host.

This option can be specified globally, and per-source as well. The local setting of the source overrides the global option if available.

Note

When relaying messages, enable this option on the syslog-ng OSE server and also on every relay, otherwise syslog-ng OSE will treat incoming messages as if they were sent by the last relay.

keep-timestamp()

Type: yes or no
Default: yes

Description: Specifies whether syslog-ng should accept the timestamp received from the sending application or client. If disabled, the time of reception will be used instead. This option can be specified globally, and per-source as well. The local setting of the source overrides the global option if available.

Warning

To use the S_ macros, the keep-timestamp() option must be enabled (this is the default behavior of syslog-ng OSE).

listen-backlog()

Type: integer
Default: 256

Description: Available only for stream based transports (unix-stream, tcp, tls). In TCP, connections are treated incomplete until the three-way handshake is completed between the server and the client. Incomplete connection requests wait on the TCP port for the listener to accept the request. The listen-backlog() option sets the maximum number of incomplete connection requests. For example:

source s_network {
    network(
        ip("192.168.1.1")
        transport("tcp")
        listen-backlog(2048)
        );
};

log-fetch-limit()

Type: number
Default: 100

Description: The maximum number of messages fetched from a source during a single poll loop. The destination queues might fill up before flow-control could stop reading if log-fetch-limit() is too high.

log-iw-size()

Type: number
Default: 100

Description: The size of the initial window, this value is used during flow control. If the max-connections() option is set, the log-iw-size() will be divided by the number of connections, otherwise log-iw-size() is divided by 10 (the default value of the max-connections() option). The resulting number is the initial window size of each connection. For optimal performance when receiving messages from syslog-ng OSE clients, make sure that the window size is larger than the flush-lines() option set in the destination of your clients.

Example 6.32. Initial window size of a connection

If log-iw-size(1000) and max-connections(10), then each connection will have an initial window size of 100.

log-msg-size()

Type: number
Default: Use the global log-msg-size() option, which defaults to 65536.

Description: Specifies the maximum length of incoming log messages. Uses the value of the global option if not specified. For details on how encoding affects the size of the message, see Section Message size and encoding.

max-connections()

Type: number
Default: 10

Description: Specifies the maximum number of simultaneous connections.

pad-size()

Type: number
Default: 0

Description: Specifies input padding. Some operating systems (such as HP-UX) pad all messages to block boundary. This option can be used to specify the block size. (HP-UX uses 2048 bytes). The syslog-ng OSE application will pad reads from the associated device to the number of bytes set in pad-size(). Mostly used on HP-UX where /dev/log is a named pipe and every write is padded to 2048 bytes. If pad-size() was given and the incoming message does not fit into pad-size(), syslog-ng will not read anymore from this pipe and displays the following error message:

Padding was set, and couldn't read enough bytes

port() or localport()

Type: number
Default:

In case of TCP transport: 601

In case of UDP transport: 514

Description: The port number to bind to.

program-override()

Type: string
Default:  

Description: Replaces the ${PROGRAM} part of the message with the parameter string. For example, to mark every message coming from the kernel, include the program-override("kernel") option in the source containing /proc/kmsg.

so-broadcast()

Type: yes or no
Default: no

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()

Type: yes or no
Default: no

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()

Type: number
Default: 0

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

Warning

When receiving messages using the UDP protocol, increase the size of the UDP receive buffer on the receiver host (that is, the syslog-ng OSE server or relay receiving the messages). Note that on certain platforms, for example, on Red Hat Enterprise Linux 5, even low message load (~200 messages per second) can result in message loss, unless the so-rcvbuf() option of the source is increased. In such cases, you will need to increase the net.core.rmem_max parameter of the host (for example, to 1024000), but do not modify net.core.rmem_default parameter.

As a general rule, increase the so-rcvbuf() so that the buffer size in kilobytes is higher than the rate of incoming messages per second. For example, to receive 2000 messages per second, set the so-rcvbuf() at least to 2 097 152 bytes.

so-sndbuf()

Type: number
Default: 0

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

tags()

Type: string
Default:  

Description: Label the messages received from the source with custom tags. Tags must be unique, and enclosed between double quotes. When adding multiple tags, separate them with comma, for example tags("dmz", "router"). This option is available only in syslog-ng 3.1 and later.

time-zone()

Type: name of the timezone, or the timezone offset
Default:  

Description: The default timezone for messages read from the source. Applies only if no timezone is specified within the message itself.

The timezone can be specified as using the name of the (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.

transport()

Type: udp, tcp, or tls
Default: tcp

Description: Specifies the protocol used to receive messages from the source.

Warning

When receiving messages using the UDP protocol, increase the size of the UDP receive buffer on the receiver host (that is, the syslog-ng OSE server or relay receiving the messages). Note that on certain platforms, for example, on Red Hat Enterprise Linux 5, even low message load (~200 messages per second) can result in message loss, unless the so-rcvbuf() option of the source is increased. In such cases, you will need to increase the net.core.rmem_max parameter of the host (for example, to 1024000), but do not modify net.core.rmem_default parameter.

As a general rule, increase the so-rcvbuf() so that the buffer size in kilobytes is higher than the rate of incoming messages per second. For example, to receive 2000 messages per second, set the so-rcvbuf() at least to 2 097 152 bytes.

tls()

Type: tls options
Default: n/a

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 Section 10.4, TLS options.

use-dns()

Type: yes, no, persist_only
Default: yes

Description: Enable or disable DNS usage. The persist_only option attempts to resolve hostnames locally from file (for example from /etc/hosts). The syslog-ng OSE application blocks on DNS queries, so enabling DNS may lead to a Denial of Service attack. To prevent DoS, protect your syslog-ng network endpoint with firewall rules, and make sure that all hosts which may get to syslog-ng are resolvable. This option can be specified globally, and per-source as well. The local setting of the source overrides the global option if available.

Note

This option has no effect if the keep-hostname() option is enabled (keep-hostname(yes)) and the message contains a hostname.

use-fqdn()

Type: yes or no
Default: no

Description: Add Fully Qualified Domain Name instead of short hostname. This option can be specified globally, and per-source as well. The local setting of the source overrides the global option if available.

Note

This option has no effect if the keep-hostname() option is enabled (keep-hostname(yes)) and the message contains a hostname.




[10] The byte order mark (BOM) is a Unicode character used to signal the byte-order of the message text.