source: Read, receive, and collect log messages
A source is where syslog-ng receives log messages. Sources consist of one or more drivers, each defining where and how messages are received.
To define a source, add a source statement to the syslog-ng configuration file using the following syntax:
source <identifier> {
source-driver(params); source-driver(params); ...
};
Example: A simple source statement
The following source statement receives messages on the TCP port 1999 of the interface having the 10.1.2.3 IP address.
source s_demo_tcp {
network(ip(10.1.2.3) port(1999));
};
Example: A source statement using two source drivers
The following source statement receives messages on the 1999 TCP port and the 1999 UDP port of the interface having the 10.1.2.3 IP address.
source s_demo_two_drivers {
network(ip(10.1.2.3) port(1999));
network(ip(10.1.2.3) port(1999) transport("udp"));
};
Example: Setting default priority and facility
If the message received by the source does not have a proper syslog header, you can use the default-facility() and default-priority() options to set the facility and priority of the messages. Note that these values are applied only to messages that do not set these parameters in their header.
source headerless_messages { network(default-facility(syslog) default-priority(emerg)); };
Define a source only once. The same source can be used in several log paths. Duplicating sources causes syslog-ng to open the source (TCP/IP port, file, and so on) more than once, which might cause problems. For example, include the /dev/log file source only in one source statement, and use this statement in more than one log path if needed.
To collect log messages on a specific platform, it is important to know how the native syslogd communicates on that platform. The following table summarizes the operation methods of syslogd on some of the tested platforms:
Table 6: Communication methods used between the applications and syslogd
| Linux |
A SOCK_DGRAM unix socket named /dev/log. Newer distributions that use systemd collect log messages into a journal file. |
| BSD flavors |
A SOCK_DGRAM unix socket named /var/run/log. |
| Solaris (2.5 or below) |
An SVR4 style STREAMS device named /dev/log. |
| Solaris (2.6 or above) |
In addition to the STREAMS device used in earlier versions, 2.6 uses a new multithreaded IPC method called door. By default the door used by syslogd is /etc/.syslog_door. |
| HP-UX 11 or later |
HP-UX uses a named pipe called /dev/log that is padded to 2048 bytes, for example, source s_hp-ux {pipe ("/dev/log" pad-size(2048)}. |
| AIX 5.2 and 5.3 |
A SOCK_STREAM or SOCK_DGRAM unix socket called /dev/log. |
Each possible communication mechanism has a corresponding source driver in syslog-ng. For example, to open a unix socket with SOCK_DGRAM style communication use the driver unix-dgram. The same socket using the SOCK_STREAM style — as used under Linux — is called unix-stream.
Example: Source statement on a Linux based operating system
The following source statement collects the following log messages:
-
internal(): Messages generated by syslog-ng.
-
network(transport("udp")): Messages arriving to the 514/UDP port of any interface of the host.
-
unix-dgram("/dev/log");: Messages arriving to the /dev/log socket.
source s_demo {
internal();
network(transport("udp"));
unix-dgram("/dev/log");
};
The following table lists the source drivers available in syslog-ng.
Table 7: Source drivers available in syslog-ng
| file() |
Opens the specified file and reads messages. |
| internal() |
Messages generated internally in syslog-ng. |
| network() |
Receives messages from remote hosts using the BSD-syslog protocol over IPv4 and IPv6. Supports the TCP, UDP, and TLS network protocols. |
| nodejs() |
Receives JSON messages from nodejs applications. |
| mbox() |
Read email messages from local mbox files, and convert them to multiline log messages. |
| osquery() |
Run osquery queries, and convert their results into log messages. |
| pacct() |
Reads messages from the process accounting logs on Linux. |
| pipe() |
Opens the specified named pipe and reads messages. |
| program() |
Opens the specified application and reads messages from its standard output. |
| python() and python-fetcher() |
Receive or fetch messages using a custom source written in Python. |
| snmptrap() |
Read and parse the SNMP traps of the Net-SNMP's snmptrapd application. |
| sun-stream(), sun-streams() |
Opens the specified STREAMS device on Solaris systems and reads incoming messages. |
| syslog() |
Listens for incoming messages using the new IETF-standard syslog protocol. |
| system() |
Automatically detects which platform syslog-ng OSE is running on, and collects the native log messages of that platform. |
| systemd-journal() |
Collects messages directly from the journal of platforms that use systemd. |
| systemd-syslog() |
Collects messages from the journal using a socket on platforms that use systemd. |
| unix-dgram() |
Opens the specified unix socket in SOCK_DGRAM mode and listens for incoming messages. |
| unix-stream() |
Opens the specified unix socket in SOCK_STREAM mode and listens for incoming messages. |
| stdin() |
Collects messages from the standard input stream. |
| wildcard-file() |
Reads messages from multiple files and directories. |
The default-network-drivers() source is a special source that uses multiple source drivers to receive and parse several different types of syslog messages from the network. Available in version 3.16 and later.
To use the default-network-drivers() source, the scl.conf file must be included in your syslog-ng OSE configuration:
@include "scl.conf"
Also, make sure that your SELinux, AppArmor, and firewall settings permit syslog-ng Open Source Edition to access the ports where you want to receive messages, and that no other application is using these ports. By default, the default-network-drivers() source accepts messages on the following ports:
-
514, both TCP and UDP, for RFC3164 (BSD-syslog) formatted traffic
-
601 TCP, for RFC5424 (IETF-syslog) formatted traffic
-
6514 TCP, for TLS-encrypted traffic
In addition to receiving messages on different ports and in different formats, this source tries to parse the messages automatically. If successful, it sets the ${.app.name} name-value pair to the name of the application that sent the log message. Currently it uses the following procedures.
|
|
Caution:
If you do not configure the TLS keys to dislay to the clients, syslog-ng OSE cannot accept encrypted connections. The application starts and listens on TCP:6514, and can receive messages on other ports, but will display a warning messages about missing keys. |
Parsing RFC3164-formatted messages
For RFC3164-formatted messages (that is, messages received on the ports set in options udp-port() and tcp-port() which default to port 514), syslog-ng OSE attempts to use the following parsers. If a parser cannot parse the message, it passes the original message to the next parser.
-
Parse the incoming raw message as a message from a Cisco device.
-
Parse the incoming message as an RFC3164-formatted message.
-
If the incoming message was sent by a syslog-ng OSE client using the syslog-ng() destination, parse its fields as a syslog-ng message.
The Enterprise-wide message model or EWMM allows you to deliver structured messages from the initial receiving syslog-ng component right up to the central log server, through any number of hops. It does not matter if you parse the messages on the client, on a relay, or on the central server, their structured results will be available where you store the messages. Optionally, you can also forward the original raw message as the first syslog-ng component in your infrastructure has received it, which is important if you want to forward a message for example, to a SIEM system. To make use of the enterprise-wide message model, you have to use the syslog-ng() destination on the sender side, and the default-network-drivers() source on the receiver side.
-
Otherwise, apply the application adapters if the message was sent from an application that already has a specific parser in syslog-ng OSE (for example, Splunk Common Information Model (CIM), iptables, or sudo).
Parsing RFC5424-formatted messages
For RFC5424-formatted messages (that is, messages received on the ports set in options rfc5424-tls-port() and rfc5424-tcp-port(), which default to port 601 and 6514), syslog-ng OSE parses the message according to RFC5424, then attempts apply the application adapters if the message was sent from an application that already has a specific parser in syslog-ng OSE (for example, Splunk Common Information Model (CIM), iptables, or sudo).
Example: Using the default-network-drivers() driver
The following example uses only the default settings.
source s_network {
default-network-drivers();
};
The following example can receive TLS-encrypted connections on the default port (port 6514).
source s_network {
default-network-drivers(
tls(
key-file("/path/to/ssl-private-key")
cert-file("/path/to/ssl-cert")
)
);
};
The systemd-journal() driver has the following options.
ca-dir()
| Accepted values: |
Directory name |
| Default: |
none |
Description: The name of a directory that contains a set of trusted CA certificates in PEM format. The CA certificate files have to be named after the 32-bit hash of the subject's name. This naming can be created using the c_rehash utility in openssl. For an example, see Configuring TLS on the syslog-ng clients. The syslog-ng OSE application uses the CA certificates in this directory to validate the certificate of the peer.
This option can be used together with the optional ca-file() option.
ca-file()
| Accepted values: |
File name |
| Default: |
empty |
Description: Optional. The name of a file that contains a set of trusted CA certificates in PEM format. The syslog-ng OSE application uses the CA certificates in this file to validate the certificate of the peer.
Example format in configuration:
ca-file("/etc/pki/tls/certs/ca-bundle.crt")
NOTE: The ca-file() option can be used together with the ca-dir() option, and it is relevant when peer-verify() is set to other than no or optional-untrusted.
flags()
| Type: |
assume-utf8, empty-lines, expect-hostname, kernel, no-hostname, no-multi-line, no-parse, sanitize-utf8, store-legacy-msghdr, store-raw-message, 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.
-
guess-timezone: Attempt to guess the timezone of the message if this information is not available in the message. Works when the incoming message stream is close to real time, and the timezone information is missing from the timestamp.
-
kernel: The kernel flag makes the source default to the LOG_KERN | LOG_NOTICE priority if not specified otherwise.
-
no-header: The no-header flag triggers syslog-ng OSE to parse only the PRI field of incoming messages, and put the rest of the message contents into $MSG.
Its functionality is similar to that of the no-parse flag, except the no-header flag does not skip the PRI field.
NOTE: Essentially, the no-header flag signals syslog-ng OSE that the syslog header is not present (or does not adhere to the conventions / RFCs), so the entire message (except from the PRI field) is put into $MSG.
Example: using the no-header flag with the syslog-parser() parser
The following example illustrates using the no-header flag with the syslog-parser() parser:
parser p_syslog {
syslog-parser(
flags(no-header)
);
};
-
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 if 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.
-
store-raw-message: Save the original message as received from the client in the ${RAWMSG} macro. You can forward this raw message in its original form to another syslog-ng node using the syslog-ng() destination, or to a SIEM system, ensuring that the SIEM can process it. Available only in 3.16 and later.
-
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 IETF-syslog messages). If the BOM character is missing, but the message is otherwise UTF-8 compliant, syslog-ng automatically adds the BOM character to the message.
log-msg-size()
| Type: |
number (bytes) |
| Default: |
Use the global log-msg-size() option, which defaults to 65536 (64 KiB). |
Description: Maximum length of an incoming message in bytes. This length includes the entire message (the data structure and individual fields). The maximal value that can be set is 268435456 bytes (256 MiB).
For messages using the IETF-syslog message format (RFC5424), the maximal size of the value of an SDATA field is 64 KiB.
NOTE: In most cases, log-msg-size() does not need to be set higher than 10 MiB.
For details on how encoding affects the size of the message, see Message size and encoding.
You can use human-readable units when setting configuration options. For details, seeNotes about the configuration syntax.
Uses the value of the global option if not specified.
max-connections()
Description: Specifies the maximum number of simultaneous connections.
Note that the total number of connections the default-network-drivers() source can use is 3*max-connections(), because this value applies to the network(tcp), syslog(tcp), and syslog(tls) connections individually.
rfc5424-tcp-port()
| Type: |
number |
| Default: |
601 |
Description: The TCP port number where the default-network-drivers() source receives RFC5424-formatted (IETF-syslog) messages.
rfc5424-tls-port()
| Type: |
number |
| Default: |
6514 |
Description: The TCP port number where the default-network-drivers() source receives RFC5424-formatted (IETF-syslog), TLS-encrypted messages.
|
|
Caution:
To receive messages using a TLS-encrypted connection, you must set the tls(key-file() cert-file()) options of the default-network-drivers() source. For example: source s_network {
default-network-drivers(
tls(
key-file("/path/to/ssl-private-key")
cert-file("/path/to/ssl-cert")
)
);
}; |
tcp-port()
| Type: |
number |
| Default: |
514 |
Description: The TCP port number where the default-network-drivers() source receives RFC3164-formatted (BSD-syslog) messages.
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 TLS options.
udp-port()
| Type: |
number |
| Default: |
514 |
Description: The UDP port number where the default-network-drivers() source receives RFC3164-formatted (BSD-syslog) messages.
