dns

Milestone: 2

DNS Filter

This filter will resolve any IP addresses from a field of your choosing.

The DNS filter performs a lookup (either an A record/CNAME record lookup or a reverse lookup at the PTR record) on records specified under the “reverse” and “resolve” arrays.

The config should look like this:

filter {
  dns {
    type => 'type'
    reverse => [ "source_host", "field_with_address" ]
    resolve => [ "field_with_fqdn" ]
    action => "replace"
  }
}

Caveats: at the moment, there’s no way to tune the timeout with the ‘resolv’ core library. It does seem to be fixed in here:

http://redmine.ruby-lang.org/issues/5100

but isn’t currently in JRuby.

Synopsis

This is what it might look like in your config file:
filter {
  dns {
    action => ... # string, one of ["append", "replace"] (optional), default: "append"
    add_field => ... # hash (optional), default: {}
    add_tag => ... # array (optional), default: []
    nameserver => ... # string (optional)
    remove_field => ... # array (optional), default: []
    remove_tag => ... # array (optional), default: []
    resolve => ... # array (optional)
    reverse => ... # array (optional)
    timeout => ... # number (optional), default: 2
  }
}

Details

action

  • Value can be any of: "append", "replace"
  • Default value is "append"

Determine what action to do: append or replace the values in the fields specified under “reverse” and “resolve.”

add_field

  • Value type is hash
  • Default value is {}

If this filter is successful, add any arbitrary fields to this event. Field names can be dynamic and include parts of the event using the %{field} Example:

filter {
  dns {
    add_field => { "foo_%{somefield}" => "Hello world, from %{host}" }
  }
}

# You can also add multiple fields at once:

filter {
  dns {
    add_field => { 
      "foo_%{somefield}" => "Hello world, from %{host}"
      "new_field" => "new_static_value"
    }
  }
}

If the event has field “somefield” == “hello” this filter, on success, would add field “foo_hello” if it is present, with the value above and the %{host} piece replaced with that value from the event. The second example would also add a hardcoded field.

add_tag

  • Value type is array
  • Default value is []

If this filter is successful, add arbitrary tags to the event. Tags can be dynamic and include parts of the event using the %{field} syntax. Example:

filter {
  dns {
    add_tag => [ "foo_%{somefield}" ]
  }
}

# You can also add multiple tags at once:
filter {
  dns {
    add_tag => [ "foo_%{somefield}", "taggedy_tag"]
  }
}

If the event has field “somefield” == “hello” this filter, on success, would add a tag “foo_hello” (and the second example would of course add a “taggedy_tag” tag).

exclude_tags DEPRECATED

  • DEPRECATED WARNING: This config item is deprecated. It may be removed in a further version.
  • Value type is array
  • Default value is []

Only handle events without all/any (controlled by exclude_any config option) of these tags. Optional.

nameserver

  • Value type is string
  • There is no default value for this setting.

Use custom nameserver.

remove_field

  • Value type is array
  • Default value is []

If this filter is successful, remove arbitrary fields from this event. Fields names can be dynamic and include parts of the event using the %{field} Example:

filter {
  dns {
    remove_field => [ "foo_%{somefield}" ]
  }
}

# You can also remove multiple fields at once:

filter {
  dns {
    remove_field => [ "foo_%{somefield}" "my_extraneous_field" ]
  }
}

If the event has field “somefield” == “hello” this filter, on success, would remove the field with name “foo_hello” if it is present. The second example would remove an additional, non-dynamic field.

remove_tag

  • Value type is array
  • Default value is []

If this filter is successful, remove arbitrary tags from the event. Tags can be dynamic and include parts of the event using the %{field} syntax. Example:

filter {
  dns {
    remove_tag => [ "foo_%{somefield}" ]
  }
}

# You can also remove multiple tags at once:

filter {
  dns {
    remove_tag => [ "foo_%{somefield}", "sad_unwanted_tag"]
  }
}

If the event has field “somefield” == “hello” this filter, on success, would remove the tag “foo_hello” if it is present. The second example would remove a sad, unwanted tag as well.

resolve

  • Value type is array
  • There is no default value for this setting.

Forward resolve one or more fields.

reverse

  • Value type is array
  • There is no default value for this setting.

Reverse resolve one or more fields.

tags DEPRECATED

  • DEPRECATED WARNING: This config item is deprecated. It may be removed in a further version.
  • Value type is array
  • Default value is []

Only handle events with all/any (controlled by include_any config option) of these tags. Optional.

timeout

  • Value type is number
  • Default value is 2

TODO(sissel): make ‘action’ required? This was always the intent, but it due to a typo it was never enforced. Thus the default behavior in past versions was ‘append’ by accident. resolv calls will be wrapped in a timeout instance

type DEPRECATED

  • DEPRECATED WARNING: This config item is deprecated. It may be removed in a further version.
  • Value type is string
  • Default value is ""

Note that all of the specified routing options (type,tags.exclude_tags,include_fields,exclude_fields) must be met in order for the event to be handled by the filter. The type to act on. If a type is given, then this filter will only act on messages with the same type. See any input plugin’s “type” attribute for more. Optional.


This is documentation from lib/logstash/filters/dns.rb