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Unbound mixed-mode module

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Use the module at your own risk
This page describes HIGHLY EXPERIMENTAL and unofficial module for unbound server!

This page describes the purpose, function and usage of experimental unbound mixed-mode module. Please that this module is highly experimental, it is not accepted nor (yet) proposed to the unbound upstream for inclusion. The module is also NOT included in the official unbound Fedora package. Purpose of this wiki is to provide a HOWTO for testers and possible developers/reviewers of the module and overall functionality/concept.

The module is targeted to be included in Fedora 23 unbound package, after it is accepted by the upstream. The intention of the module is to solve some particular users use-cases, that are described later on this page. The intention is to provide secure, seamless and user-friendly DNSSEC experience on the client side.

The testing build of unbound server with the mixed-mode module can be found in the COPR repo




Method described below is covered by US patent application named "USING DOMAIN NAME SYSTEM SECURITY EXTENSIONS IN A MIXED-MODE ENVIRONMENT". See Red Hat, Inc. Statement of Position and Our Promise on Software Patents



The configuration may change at any time
The configuration syntax and any configuration options related to the mixed-mode may change in the future!

To be able to use the module, one has to edit the unbound server configuration file /etc/unbound/unbound.conf.

Most importantly add the mixed-mode module into list of modules. The module has to be placed before the validator module. This is due to the fact, that mixed-mode module acts upon the final DNSSEC verification of the DNS Answer.

    module-config: "mixed-mode validator iterator"

Static configuration

The mixed-mode module can be configured statically in the unbound configuration file /etc/unbound/unbound.conf. This can be done using the mixed-mode-fwd statement, inside the server section. The static configuration will be used after every server star/restart.

The mixed-mode-fwd statement is followed by the IPv4 or IPv6 address of DNSSEC-not-enabled resolver.

mixed-mode-fwd: <IP address>

It is possible to specify IP addresses for multiple resolvers by using multiple mixed-mode-fwd statements.

In the end, a static configuration of unbound server using the mixed-mode module can look like the following example:

    module-config: "mixed-mode validator iterator"
    mixed-mode-fwd: fd00:dead:beef:55::1

Dynamic configuration

The mixed-mode module can be configured during unbound runtime using the unbound-control tool. To do this, use the unbound-control with mixed_module_fwds command. The usage is also included in the tool help output:

# unbound-control -h
  mixed_mode_fwds [off | addr ...]	without arg show mixed-mode forwarders in use
					or off to turn off mixed-mode and delete forwardrs list
					or give list of ip addresses of forwarders to use

Inspecting the current configuration

To inspect the forwarders used by mixed-mode module use the mixed_module_fwds command without any arguments. In case there are some forwarders configured, the list is printed to the console:

# unbound-control mixed_mode_fwds fd00:dead:beef:55::1

In case there are not any forwarders configured the fact is also printed to the console:

# unbound-control mixed_mode_fwds
not using any mixed-mode forwarders

Configuring new set of forwarders

To configure mixed-mode module to use new set of forwarders, use the mixed_module_fwds command followed by the IP addresses of new forwarders:

# unbound-control mixed_mode_fwds

Clearing the set of forwarders

To clear the list of forwarders used by the mixed-mode module (and effectively disable the module functionality), use the mixed_module_fwds command followed by the off keyword:

# unbound-control mixed_mode_fwds off





Feel free to add a question.