150.4. Batched compression (im_batchcompress)

Table of Contents

The im_batchcompress module provides a compressed network transport with optional SSL encryption. It uses its own protocol to receive and decompress a batch of messages sent by om_batchcompress.

Note	To examine the supported platforms, see the list of installer packages in the Available Modules chapter.

150.4.1. Configuration

The im_batchcompress module accepts the following directives in addition to the common module directives.

ListenAddr: The module accepts connections on the IP address or hostname and port defined here. The default address is localhost and the default port is 2514. The port number can be defined by appending it at the end of the hostname or IP address using a colon as a separator (host:port). The port section of this directive and the Port directive are mutually exclusive. In case both is defined, the port number defined here takes precedence over a port defined in the Port directive. In case none of them is defined, the default port is used.
To listen on multiple addresses or ports in a single module instance, this directive can be repeated multiple times. Both IPv4 and IPv6 addresses are supported. If a DNS name is used, the number of addresses or cnames should be kept below 16 to avoid potential issues caused by DNS response size limits.

Note

When the Host directive is used with a hostname instead of an IP address, the the hostname will be resolved to an IP address for each new connection. If a resolver, e.g. DNS, returns multiple IP addresses, the module will connect to the first IP address. If a single output instance is configured with multiple Host directives or the resolver returns multiple addresses for a name, these hosts are accessed in failover mode. If a Host directive is configured with a hostname, the product performs a name lookup and establishes the connection to the first reachable address in the returned set of addresses. The module will remain connected to that address until it is stopped, or the connection is severed. DNS changes are therefore not picked up by the module without intervention. If the connection fails to the first address of the set, the module will attempt to connect to the next address, until it reaches the end of the set of addresses. Then it performs a lookup on the next Host directive, if so configured. Once all options are exhausted, the module will start over from the first Host directive, cycling through them again until connection can be reestablished.

Note

When the ListenAddr (or similar) directive specifies a hostname, the module binds to the first IP address that is exposed by the system for that hostname. On most systems that support IPv6, this address will be an IPv6 address. This means that client applications and the systems they run on will also need to have IPv6 support enabled, and must be able to connect to the same IPv6 address. NXLog output modules achieve this requirement through failover. For third-party client applications, the configuration details are application-specific but they should have the ability to detect which IP address the server is listening on when using a hostname to connect.

For client applications that don’t support IPv6, to avoid the behavior described above the ListenAddr directive of the listening module may be set to an IPv4 address e.g. 0.0.0.0.

Alternatively, the server-side system may be configured to prioritize IPv4 addresses for the hostname specified by the ListenAddr directive, although this is a more complicated and potentially intrusive approach. On most Linux-based systems, this can be achieved through the /etc/gai.conf configuration file. On BSD-based systems, the ip6addrctl command can be used. Windows is more limited and can only be configured to prioritize IPv4 over IPv6 addresses for ALL hostnames resolved on the system, by setting the following registry value to 0x20:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters\DisabledComponents

For more information see the Microsoft documentation on Configuring IPv6 in Windows for advanced users.

This limitation will be addressed in a future release by making listening modules bind to all available IPv4/IPv6 addresses that a hostname resolves to.

Port: The module listens for incoming connections on the port defined in this directive. The default is port 2514.

Important

The Port directive will become deprecated from NXLog EE 6.0. After that, the port can only be defined in the ListenAddr directive.

AllowIP

This optional directive may be used to specify a whitelist of IP addresses and/or networks that are allowed to connect. The directive can be specified more than once to add different IPs or networks to the whitelist. This directive is only active when the Listen or ListenAddr directives are present. In the absence of this directive, there is no restriction on the hosts which may connect to a listening module. The following formats may be used:

0.0.0.0 (IPv4 address)
0.0.0.0/32 (IPv4 network with subnet bits)
0.0.0.0/0.0.0.0 (IPv4 network with subnet address)
aa::1 (IPv6 address)
aa::12/64 (IPv6 network with subnet bits)

AllowExpired: This boolean directive specifies whether the connection should be allowed with an expired certificate. If set to TRUE, the remote client will be able to connect with an expired certificate. The default is FALSE: the certificate must not be expired. This directive is only valid if RequireCert is set to TRUE.

AllowUntrusted: This boolean directive specifies that the remote connection should be allowed regardless of the certificate verification results. If set to TRUE, the remote client will be able to connect with any unexpired certificate. The default value is FALSE: the remote server must present a trusted certificate.

CADir

This directive specifies a path to a directory containing certificate authority (CA) certificates. These certificates will be used to verify the certificate presented by the remote client. The certificate files must be named using the OpenSSL hashed format, i.e. the hash of the certificate followed by .0, .1 etc. To find the hash of a certificate using OpenSSL:

$ openssl x509 -hash -noout -in ca.crt

For example if the certificate hash is e2f14e4a, then the certificate filename should be e2f14e4a.0. If there is another certificate with the same hash then it should be named e2f14e4a.1 and so on.

A remote client’s self-signed certificate (which is not signed by a CA) can also be trusted by including a copy of the certificate in this directory.

CAFile: This specifies the path of the certificate authority (CA) certificate that will be used to verify the certificate presented by the remote client. A remote client’s self-signed certificate (which is not signed by a CA) can be trusted by specifying the remote client certificate itself. In case of certificates signed by an intermediate CA, the certificate specified must contain the complete certificate chain (certificate bundle).

CAThumbprint: This optional directive specifies the thumbprint of the certificate authority (CA) certificate that will be used to verify the certificate presented by the remote client. The hexadecimal fingerprint string can be copied from Windows Certificate Manager (certmgr.msc). Whitespaces are automatically removed. The certificate must be imported to the Local Computer\Personal certificate store for NXLog to find it. This directive is only supported on Windows and is mutually exclusive with the CADir and CAFile directives.

CertFile: This specifies the path of the certificate file that will be presented to the remote client during the SSL handshake.

CertKeyFile: This specifies the path of the private key file that was used to generate the certificate specified by the CertFile directive. This is used for the SSL handshake.

CertThumbprint

This optional directive specifies the thumbprint of the certificate that will be presented to the remote client during the SSL handshake. The hexadecimal fingerprint string can be copied from Windows Certificate Manager (certmgr.msc). Whitespaces are automatically removed. The certificate must be imported to the Local Computer\Personal certificate store in PFX format for NXLog to find it. To create a PFX file from the certificate and private key using OpenSSL:

$ openssl pkcs12 -export -out server.pfx -inkey server.key -in server.pem

This directive is only supported on Windows and is mutually exclusive with the CertFile and CertKeyFile directives.

CRLDir

This directive specifies a path to a directory containing certificate revocation list (CRL) files. These CRL files will be used to check for certificates that were revoked and should no longer be accepted. The files must be named using the OpenSSL hashed format, i.e. the hash of the issuer followed by .r0, .r1 etc. To find the hash of the issuer of a CRL file using OpenSSL:

$ openssl crl -hash -noout -in crl.pem

For example if the hash is e2f14e4a, then the filename should be e2f14e4a.r0. If there is another file with the same hash then it should be named e2f14e4a.r1 and so on.

CRLFile

This specifies the path of the certificate revocation list (CRL) which will be used to check for certificates that have been revoked and should no longer be accepted. Example to generate a CRL file using OpenSSL:

$ openssl ca -gencrl -out crl.pem

DHFile: This optional directive specifies a file with dh-parameters for Diffie-Hellman key exchange. These parameters can be generated with dhparam(1ssl). If this directive is not specified, default parameters will be used. See the OpenSSL Wiki for further details.

KeyPass

This directive specifies the passphrase of the private key specified by the CertKeyFile directive. A passphrase is required when the private key is encrypted. Example to generate a private key with Triple DES encryption using OpenSSL:

$ openssl genrsa -des3 -out server.key 2048

This directive is not needed for passwordless private keys.

RequireCert: This boolean value specifies that the remote client must present a certificate. If set to TRUE and a certificate is not presented during the SSL handshake, the connection will be refused. The default value is TRUE: each connection must use a certificate.

SSLCipher: This optional directive can be used to set the permitted cipher list for TLSv1.2 and below, overriding the default. Use the format described in the ciphers(1ssl) man page. For example specify RSA:!COMPLEMENTOFALL to include all ciphers with RSA authentication but leave out ciphers without encryption.

Note	If RSA or DSA ciphers with Diffie-Hellman key exchange are used, DHFile can be set for specifying custom dh-parameters.

SSLCiphersuites

This optional directive can be used to set the permitted cipher list for TLSv1.3. Use the same format as in the SSLCipher directive. Refer to the OpenSSL documentation for a list of valid TLS v1.3 cipher suites. The default value is:

TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256

SSLProtocol: This directive can be used to set the allowed SSL/TLS protocol(s). It takes a comma-separated list of values which can be any of the following: SSLv2, SSLv3, TLSv1, TLSv1.1, TLSv1.2, and TLSv1.3. By default, the TLSv1.2 and TLSv1.3 protocols are allowed. Note that the OpenSSL library shipped by Linux distributions may not support SSLv2 and SSLv3, and these will not work even if enabled with this directive.

150.4.2. Fields

The following fields are used by im_batchcompress.

$MessageSourceAddress (type: string): The IP address of the remote host.

150.4.3. Examples

Pre-v5 syntax examples are included, they will become invalid with NXLog EE 6.0.

Example 845. Reading batch compressed data

This configuration listens on port 2514 for incoming log batches and writes them to file.

nxlog.conf

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  <Input batchcompress>
    Module      im_batchcompress
    ListenAddr  0.0.0.0:2514
</Input>

# Using the syntax prior to NXLog EE 5,
# where the port is defined in a separate directive.
#<Input batchcompress>
#    Module      im_batchcompress
#    ListenAddr  0.0.0.0
#    Port        2514
#</Input>

<Output file>
    Module      om_file
    File        "tmp/output"
</Output>

<Route batchcompress_to_file>
    Path        batchcompress => file
</Route>

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