network() source options
The network()
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 AxoSyslog clients. The AxoSyslog 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 AxoSyslog 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")
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
.
check-hostname()
Type: | boolean (yes or no ) |
Default: | Use the global check-hostname() option, which defaults to no . |
Checks that the hostname contains valid characters. Uses the value of the global option if not specified.
dynamic-window-size()
Type: | number |
Default: | 0 |
Description: The size of the dynamic control window used during flow-control. For details on flow-control, see Managing incoming and outgoing messages with flow-control.
ebpf()
Available in AxoSyslog version 4.2 and newer.
By default, the kernel chooses the receive socket for a specific UDP randomly based on the source IP/port of the sender. You can customize this algorithm using the Extended Berkeley Packet Filter (eBPF) plugin. The ebpf()
option changes the kernel’s SO_REUSEPORT algorithm so that all messages are randomly placed into one of the UDP sockets. The decision which UDP socket buffer a datagram is placed is made for every datagram, and not once for every stream. This means that messages are perfectly load-balanced across your set of UDP sockets. While this resolves the imbalance between the sockets and results in perfect load balancing, you will lose ordering between messages from the same sender, which is the price to pay for increased throughput.
source s_network {
network(
transport("udp")
so-reuseport(1) persist-name("udp1")
ebpf(reuseport(sockets(4)))
);
network(transport("udp") so-reuseport(1) persist-name("udp2"));
network(transport("udp") so-reuseport(1) persist-name("udp3"));
network(transport("udp") so-reuseport(1) persist-name("udp4"));
};
For a detailed introduction, see the Scaling syslog to 1M EPS with eBPF blog post.
encoding()
Type: | string |
Default: |
Description: Specifies the character set (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 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, 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 thevalidate-utf8
flag. -
empty-lines: Use the
empty-lines
flag to keep the empty lines of the messages. By default, AxoSyslog removes empty lines automatically. -
expect-hostname: If the
expect-hostname
flag is enabled, AxoSyslog 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 theno-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 theLOG_KERN | LOG_NOTICE
priority if not specified otherwise. -
no-header: The
no-header
flag triggers AxoSyslog to parse only thePRI
field of incoming messages, and put the rest of the message contents into$MSG
.Its functionality is similar to that of the
no-parse
flag, except theno-header
flag does not skip thePRI
field.Note Essentially, theno-header
flag signals AxoSyslog that thesyslog
header is not present (or does not adhere to the conventions / RFCs), so the entire message (except from thePRI
field) is put into$MSG
.Example: using the no-header flag with the syslog-parser() parser
The following example illustrates using the
no-header
flag with thesyslog-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 AxoSyslog assumes that the first part of the message header is ${PROGRAM} instead of ${HOST}. For example:source s_dell { network( port(2000) flags(no-hostname) ); };
-
no-multi-line: The
no-multi-line
flag disables line-breaking in the messages: the entire message is converted to a single line. Note that this happens only if the underlying transport method actually supports multi-line messages. Currently thefile()
andpipe()
drivers support multi-line messages. -
no-parse: By default, AxoSyslog parses incoming messages as syslog messages. The
no-parse
flag completely disables syslog message parsing and processes the complete line as the message part of a syslog message. The AxoSyslog application will generate a new syslog header (timestamp, host, and so on) automatically and put the entire incoming message into the MESSAGE part of the syslog message (available using the${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, AxoSyslog generates a new syslog header (timestamp, host, and so on) automatically. Note that even thoughflags(no-parse)
disables message parsing, some flags can still be used, for example, theno-multi-line
flag. -
dont-store-legacy-msghdr: By default, AxoSyslog 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 (AxoSyslog 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 thedont-store-legacy-msghdr
flag. -
sanitize-utf8: When using the
sanitize-utf8
flag, AxoSyslog converts non-UTF-8 input to an escaped form, which is valid UTF-8.Prior to version 4.6, this flag worked only when parsing RFC3164 messages. Starting with version 4.6, it works also for RFC5424 and raw messages.
-
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 AxoSyslog node using thesyslog-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 thesyslog
driver, which handles only messages that have a frame header. -
validate-utf8: The
validate-utf8
flag enables encoding-verification for messages.Prior to version 4.6, this flag worked only when parsing RFC3164 messages. Starting with version 4.6, it works also for RFC5424 and raw messages.
For RFC5424-formatted messages, if the BOM character is missing, but the message is otherwise UTF-8 compliant, AxoSyslog automatically adds the BOM character to the message.
The byte order mark (BOM) is a Unicode character used to signal the byte-order of the message text.
-
threaded: The
threaded
flag enables multithreading for the source. For details on multithreading, see Multithreading and scaling.Note Thesyslog
source uses multiple threads only if the source uses thetls
ortcp
transport protocols.
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 hook-commands()
when AxoSyslog starts or stops
To execute an external program when AxoSyslog starts or stops, use the following options:
startup()
Type: | string |
---|---|
Default: | N/A |
Description: Defines the external program that is executed as AxoSyslog starts.
shutdown()
Type: | string |
---|---|
Default: | N/A |
Description: Defines the external program that is executed as AxoSyslog stops.
Using the hook-commands() when AxoSyslog reloads
To execute an external program when the AxoSyslog configuration is initiated or torn down, for example, on startup/shutdown or during a AxoSyslog reload, use the following options:
setup()
Type: | string |
---|---|
Default: | N/A |
Description: Defines an external program that is executed when the AxoSyslog configuration is initiated, for example, on startup or during a AxoSyslog reload.
teardown()
Type: | string |
---|---|
Default: | N/A |
Description: Defines an external program that is executed when the AxoSyslog configuration is stopped or torn down, for example, on shutdown or during a AxoSyslog reload.
Example: Using the hook-commands() with a network source
In the following example, the hook-commands()
is used with the network()
driver and it opens an iptables port automatically as AxoSyslog is started/stopped.
The assumption in this example is that the LOGCHAIN
chain is part of a larger ruleset that routes traffic to it. Whenever the AxoSyslog created rule is there, packets can flow, otherwise the port is closed.
source {
network(transport(udp)
hook-commands(
startup("iptables -I LOGCHAIN 1 -p udp --dport 514 -j ACCEPT")
shutdown("iptables -D LOGCHAIN 1")
)
);
};
host-override()
Type: | string |
Default: |
Description: Replaces the ${HOST} part of the message with the parameter string.
interface()
Type: | string |
Default: | None |
Description: Bind to the specified interface instead of an IP address. Available in 3.19 and later.
ip() or localip()
Type: | string |
Default: | 0.0.0.0 |
Description: The IP address to bind to. By default, AxoSyslog 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, AxoSyslog 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 AxoSyslog is forced to reload its configuration (upon the receipt of a SIGHUP signal). Note that this applies to the server (source) side of the AxoSyslog 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)
), AxoSyslog assumes that the incoming log message was sent by the host specified in theHOST
field of the message. -
If disabled (
keep-hostname(no)
), AxoSyslog rewrites theHOST
field of the message, either to the IP address (if theuse-dns()
parameter is set tono
), or to the hostname (if theuse-dns()
parameter is set toyes
and the IP address can be resolved to a hostname) of the host sending the message to AxoSyslog. For details on using name resolution in AxoSyslog, see Using name resolution in syslog-ng.
If the log message does not contain a hostname in its HOST
field, AxoSyslog 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, AxoSyslog 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.
keep-timestamp()
Type: | yes or no |
Default: | yes |
Description: Specifies whether AxoSyslog 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.
S_
macros, the keep-timestamp()
option must be enabled (this is the default behavior of AxoSyslog).
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. Its value cannot be lower than 100, unless the dynamic-window-size()
option is enabled. For details on flow-control, see Managing incoming and outgoing messages with 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 AxoSyslog clients, make sure that the window size is larger than the flush-lines()
option set in the destination of your clients.
Example: 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 (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.
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()
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. The AxoSyslog 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()
, AxoSyslog 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: 514 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 AxoSyslog 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.
When receiving messages using the UDP protocol, increase the size of the UDP receive buffer on the receiver host (that is, the AxoSyslog 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 this 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-reuseport()
Type: | yes or no |
Default: | no |
Description: Enables SO_REUSEPORT on systems that support it. When enabled, the kernel allows multiple UDP sockets to be bound to the same port, and the kernel load-balances incoming UDP datagrams to the sockets. The sockets are distributed based on the hash of (srcip, dstip, srcport, dstport), so the same listener should be receiving packets from the same endpoint. For example:
source {
network(transport("udp") so-reuseport(1) port(2000) persist-name("udp1"));
network(so-reuseport(1) port(2000) persist-name("udp2"));
network(so-reuseport(1) port(2000) persist-name("udp3"));
network(so-reuseport(1) port(2000) persist-name("udp4"));
};
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-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 version 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 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.
transport()
Type: | udp, tcp, tls, proxied-tcp, proxied-tls, proxied-tls-passthrough, text-with-nuls |
Default: | tcp |
Description: Specifies the protocol used to receive messages from the source.
For detailed information about how AxoSyslog supports the proxied-tcp
, the proxied-tls
, and the proxied-tls-passthrough
parameters, see Proxy Protocol support.
text-with-nuls
: Allows embedded NUL
characters in the message from a TCP source, that is, AxoSyslog will not delimiter the incoming messages on NUL
characters, only on newline
characters (contrary to tcp
transport, which splits the incoming log on newline
characters and NUL
characters).
NUL
characters everywhere, so it is recommended that you also use flags(no-multi-line)
that causes NUL
characters to be replaced by space.
When receiving messages using the UDP protocol, increase the size of the UDP receive buffer on the receiver host (that is, the AxoSyslog 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 this 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.
trim-large-messages()
Type: | `yes |
Default: | Use the global trim-large-messages() option, which defaults to no . |
Description: Determines what AxoSyslog does with incoming log messages that are received using the IETF-syslog protocol using the syslog()
driver, and are longer than the value of log-msg-size()
. Other drivers ignore the trim-large-messages()
option.
-
If set to
no
, AxoSyslog drops the incoming log message. -
If set to
yes
, AxoSyslog trims the incoming log message to the size set inlog-msg-size()
, and adds thetrimmed
tag to the message. The rest of the message is dropped. You can use the tag to filter on such messages.filter f_trimmed { tags("trimmed"); };
If AxoSyslog trims a log message, it sends a debug-level log message to its
internal()
source.As a result of trimming, a parser could fail to parse the trimmed message. For example, a trimmed JSON or XML message will not be valid JSON or XML.
Available in AxoSyslog version 3.21 and later.
Uses the value of the global option if not specified.
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.
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 AxoSyslog application blocks on DNS queries, so enabling DNS may lead to a Denial of Service attack. To prevent DoS, protect your AxoSyslog network endpoint with firewall rules, and make sure that all hosts which may get to AxoSyslog 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.
keep-hostname()
option is enabled (keep-hostname(yes)
) and the message contains a hostname.
use-fqdn()
Type: | yes or no |
Default: | no |
Description: Use this option to add a Fully Qualified Domain Name (FQDN) instead of a short hostname. You can specify this option either globally or per-source. The local setting of the source overrides the global option if available.
use-fqdn()
to yes
if you want to use the custom-domain()
global option.
keep-hostname()
option is enabled (keep-hostname(yes)
) and the message contains a hostname.