mdns

Description

This plugin reads mDNS records from the local network and responds to queries based on those records.

Useful for providing mDNS records to non-mDNS-aware applications by making them accessible through a standard DNS server.

Syntax

mdns example.com [minimum SRV records] [filter text] [bind address]

Examples

As a prerequisite to using this plugin, there must be systems on the local network broadcasting mDNS records. Note that the .local domain will be replaced with the configured domain. For example, test.local would become test.example.com using the configuration below.

Specify the domain for the records.

example.com {
	mdns example.com
}

And test with dig:

dig @localhost baremetal-test-extra-1.example.com

;; ANSWER SECTION:
baremetal-test-extra-1.example.com. 60 IN A   12.0.0.24
baremetal-test-extra-1.example.com. 60 IN AAAA fe80::f816:3eff:fe49:19b3

If minimum SRV records is specified in the configuration, the plugin will wait until it has at least that many SRV records before responding with any of them. minimum SRV records defaults to 3.

example.com {
    mdns example.com 2
}

This would mean that at least two SRV records of a given type would need to be present for any SRV records to be returned. If only one record is found, any requests for that type of SRV record would receive no results.

If filter text is specified in the configuration, the plugin will ignore any mDNS records that do not include the specified text in the service name. This allows the plugin to be used in environments where there may be mDNS services advertised that are not intended for use with it. When filter text is not set, all records will be processed.

example.com {
    mdns example.com 3 my-id
}

This configuration would ignore any mDNS records that do not contain the string “my-id” in their service name.

If bind address is specified in the configuration, the plugin will only send mDNS traffic to the associated interface. This prevents sending multicast packets on interfaces where that may not be desirable. To use bind address without setting a filter, set filter text to “”.

example.com {
    mdns example.com 3 "" 192.168.1.1
}

This configuration will only send multicast packets to the interface assigned the 192.168.1.1 address. The interface lookup is dynamic each time an mDNS query is sent, so if the address moves to a different interface the plugin will automatically switch to the new one.