=head1 NAME

Zonemaster::Engine::Overview - The Zonemaster Test Engine

=head1 INTRODUCTION

The Zonemaster system is a quality control tool for DNS zones, produced in cooperation between AFNIC and IIS (the top-level registries for respectively France and Sweden). It is a successor both to AFNIC's tool Zonecheck and IIS's tool DNSCheck, and is intended to be an improvement over both.

The system as a whole consists of the test engine and, as distributed by the project, two different front ends. One is a command-line interface intended for use by experienced technicians, and one is a web interface meant for use by anyone. This document only talks about the test engine.

=head1 DESCRIPTION

=head2 Brief overview

Conceptually, the test engine consists of a number of test implementation modules surrounded by a support framework. Anyone wanting to use Zonemaster to perform tests communicates with the framework from the "outside", and all modules implementing tests see the world entirely through the framework. Doing things this way lets us have features like the ability to test domains before they are published, to record entire test runs for later analysis and to make sure that test results are (as far as reality allows) predictable and repeatable.

=head2 For users of Zonemaster

If all you want to do is run tests, you need to care about four or five modules. L<Zonemaster::Engine> is the main access point to the framework, and it is via its methods that you set the configuration (if needed), request that tests be started and access the logger. The logger is where the test results end up, so that's pretty important. On top of those, you may want to use the L<Zonemaster::Engine::Translator> to turn the results into human-readable messages.

There are two ways that you can get the results of a test you've requested: the simple-but-inflexible way and the flexible-but-complex way.

The simple-but-inflexible way is that all the methods in L<Zonemaster::Engine> that run tests return lists of L<Zonemaster::Engine::Logger::Entry> objects. Those lists include all the results that the writer of the test module(s) considered important enough to return by default. The advantage of this method is that it is extremely easy to use. The following is a functional (if not very useful) way to run a full test and print the results from a command-line prompt:

 perl -MZonemaster::Engine -E 'say "$_" for Zonemaster::Engine->new->test_zone("example.org")'

The main drawbacks of this method are that there is no choice about what
messages to see, and it's entirely synchronous.
The code that started the test does not get a chance to do anything at
all until the whole test suite has finished, which may be several minutes later.

To get around those drawbacks there is the flexible-but-complex way,
which consists of installing a callback that gets executed every time
a message is logged.
It's not that much more complicated, code-wise.
The following example does roughly the same thing as the one above:

 perl -MZonemaster::Engine -E 'Zonemaster::Engine->logger->callback(sub {say "$_[0]"}); Zonemaster::Engine->new->test_zone("example.org");'

If you try running those, you'll notice two main differences. First, the second variant prints results as they are generated. Second, it generates a B<lot> more output. On my machine right now, the first example gives me 94 lines of output. The second example gives me 17684.

You can do pretty much whatever you want with the message objects in the callback (including modifying them, although we don't promise that behavior will stay around). If the callback code throws an exception, and that exception is not a subclass of L<Zonemaster::Engine::Exception>, the callback will be removed. Note also that while the callback is running, the test engine itself is not. So think twice before you do potentially time-consuming tasks (like sticking the message in a database) in the callback. After waiting for responses from remote name servers (which usually stands for more than 90% of the time used), the result logging is the single most time-consuming task in a Zonemaster test run.

From here, you probably want to look at the documentation for L<Zonemaster::Engine>, L<Zonemaster::Engine::Logger>, L<Zonemaster::Engine::Logger::Entry>, L<Zonemaster::Engine::Profile> and L<Zonemaster::Engine::Translator>.

=head2 For developers of Zonemaster Test Modules

If you want to develop a test module of your own, the standard set of modules serve as examples.

As an entry point to the "inside" of the Zonemaster framework, you want to read L<Zonemaster::Engine::Zone> and follow references from there. Of particular interest after the L<Zone|Zonemaster::Engine::Zone> class should be the L<Zonemaster::Engine::Nameserver> and possibly L<Zonemaster::Engine::Recursor> classes.

If you do write your own test module, I would very much appreciate feedback on which parts were tricky to figure out, because I'm honestly not sure what I need to explain here. So please, if there's something that you think really needs to be written about, create an issue at L<https://github.com/zonemaster/zonemaster-engine/issues>.

=head2 For developers of the Zonemaster Test Framework

Random recommendations and advice. May be replaced with more coherent developer documentation in the future.

=over

=item

Stability, predictability and reliability are more important than performance.

=item

Don't forget that starting with Perl version 5.18, the order in which you get the keys out of a hash will be different every time the script is run. Get used to always writing C<sort keys %hash>.

=item

If two (or more) test modules implement the same (or very similar) thing, it should probably be extracted into the framework.

=item

The unit tests run against pre-recorded data, unless the environment variable C<ZONEMASTER_RECORD> is set to a (perl-)true value. In that case, it runs against the live DNS world and records all results for future use. Unfortunately this sometime means that some tests fail, when we were relying on seeing certain problems in certain domains, and those no longer look the same.

=item

The translation strings returned from a test module are used as keys in the GNU gettext system, so if you change anything in them don't forget to also change the translation C<.po> files in F<share>.

=item

Adding a new message tag is more work than it first looks, since it needs to be added to the test module metadata, the default profile and the translation system in order to be fully functional.

=back

=head1 REFERENCES

=over

=item L<https://github.com/zonemaster/zonemaster>

Main repository, holding among other things our test specifications.

=back

=head2 List of all RFCs referred to in the test specifications

=over

=item

L<RFC0822 "STANDARD FOR THE FORMAT OF ARPA INTERNET TEXT MESSAGES"|http://www.rfc-editor.org/info/rfc822>

=item

L<RFC0919 "Broadcasting Internet Datagrams"|http://www.rfc-editor.org/info/rfc919>

=item

L<RFC0952 "DoD Internet host table specification"|http://www.rfc-editor.org/info/rfc952>

=item

L<RFC1033 "Domain Administrators Operations Guide"|http://www.rfc-editor.org/info/rfc1033>

=item

L<RFC1034 "Domain names - concepts and facilities"|http://www.rfc-editor.org/info/rfc1034>

=item

L<RFC1035 "Domain names - implementation and specification"|http://www.rfc-editor.org/info/rfc1035>

=item

L<RFC1112 "Host extensions for IP multicasting"|http://www.rfc-editor.org/info/rfc1112>

=item

L<RFC1122 "Requirements for Internet Hosts - Communication Layers"|http://www.rfc-editor.org/info/rfc1122>

=item

L<RFC1123 "Requirements for Internet Hosts - Application and Support"|http://www.rfc-editor.org/info/rfc1123>

=item

L<RFC1912 "Common DNS Operational and Configuration Errors"|http://www.rfc-editor.org/info/rfc1912>

=item

L<RFC1918 "Address Allocation for Private Internets"|http://www.rfc-editor.org/info/rfc1918>

=item

L<RFC1930 "Guidelines for creation, selection, and registration of an Autonomous System (AS)"|http://www.rfc-editor.org/info/rfc1930>

=item

L<RFC1982 "Serial Number Arithmetic"|http://www.rfc-editor.org/info/rfc1982>

=item

L<RFC1996 "A Mechanism for Prompt Notification of Zone Changes (DNS NOTIFY)"|http://www.rfc-editor.org/info/rfc1996>

=item

L<RFC2142 "Mailbox Names for Common Services, Roles and Functions"|http://www.rfc-editor.org/info/rfc2142>

=item

L<RFC2181 "Clarifications to the DNS Specification"|http://www.rfc-editor.org/info/rfc2181>

=item

L<RFC2182 "Selection and Operation of Secondary DNS Servers"|http://www.rfc-editor.org/info/rfc2182>

=item

L<RFC2308 "Negative Caching of DNS Queries (DNS NCACHE)"|http://www.rfc-editor.org/info/rfc2308>

=item

L<RFC2544 "Benchmarking Methodology for Network Interconnect Devices"|http://www.rfc-editor.org/info/rfc2544>

=item

L<RFC2671 "Extension Mechanisms for DNS (EDNS0)"|http://www.rfc-editor.org/info/rfc2671>

=item

L<RFC2822 "Internet Message Format"|http://www.rfc-editor.org/info/rfc2822>

=item

L<RFC2870 "Root Name Server Operational Requirements"|http://www.rfc-editor.org/info/rfc2870>

=item

L<RFC2928 "Initial IPv6 Sub-TLA ID Assignments"|http://www.rfc-editor.org/info/rfc2928>

=item

L<RFC3056 "Connection of IPv6 Domains via IPv4 Clouds"|http://www.rfc-editor.org/info/rfc3056>

=item

L<RFC3068 "An Anycast Prefix for 6to4 Relay Routers"|http://www.rfc-editor.org/info/rfc3068>

=item

L<RFC3658 "Delegation Signer (DS) Resource Record (RR)"|http://www.rfc-editor.org/info/rfc3658>

=item

L<RFC3696 "Application Techniques for Checking and Transformation of Names"|http://www.rfc-editor.org/info/rfc3696>

=item

L<RFC3701 "6bone (IPv6 Testing Address Allocation) Phaseout"|http://www.rfc-editor.org/info/rfc3701>

=item

L<RFC3849 "IPv6 Address Prefix Reserved for Documentation"|http://www.rfc-editor.org/info/rfc3849>

=item

L<RFC3927 "Dynamic Configuration of IPv4 Link-Local Addresses"|http://www.rfc-editor.org/info/rfc3927>

=item

L<RFC4034 "Resource Records for the DNS Security Extensions"|http://www.rfc-editor.org/info/rfc4034>

=item

L<RFC4035 "Protocol Modifications for the DNS Security Extensions"|http://www.rfc-editor.org/info/rfc4035>

=item

L<RFC4074 "Common Misbehavior Against DNS Queries for IPv6 Addresses"|http://www.rfc-editor.org/info/rfc4074>

=item

L<RFC4193 "Unique Local IPv6 Unicast Addresses"|http://www.rfc-editor.org/info/rfc4193>

=item

L<RFC4291 "IP Version 6 Addressing Architecture"|http://www.rfc-editor.org/info/rfc4291>

=item

L<RFC4343 "Domain Name System (DNS) Case Insensitivity Clarification"|http://www.rfc-editor.org/info/rfc4343>

=item

L<RFC4380 "Teredo: Tunneling IPv6 over UDP through Network Address Translations (NATs)"|http://www.rfc-editor.org/info/rfc4380>

=item

L<RFC4843 "An IPv6 Prefix for Overlay Routable Cryptographic Hash Identifiers (ORCHID)"|http://www.rfc-editor.org/info/rfc4843>

=item

L<RFC5155 "DNS Security (DNSSEC) Hashed Authenticated Denial of Existence"|http://www.rfc-editor.org/info/rfc5155>

=item

L<RFC5156 "Special-Use IPv6 Addresses"|http://www.rfc-editor.org/info/rfc5156>

=item

L<RFC5180 "IPv6 Benchmarking Methodology for Network Interconnect Devices"|http://www.rfc-editor.org/info/rfc5180>

=item

L<RFC5321 "Simple Mail Transfer Protocol"|http://www.rfc-editor.org/info/rfc5321>

=item

L<RFC5358 "Preventing Use of Recursive Nameservers in Reflector Attacks"|http://www.rfc-editor.org/info/rfc5358>

=item

L<RFC5737 "IPv4 Address Blocks Reserved for Documentation"|http://www.rfc-editor.org/info/rfc5737>

=item

L<RFC5771 "IANA Guidelines for IPv4 Multicast Address Assignments"|http://www.rfc-editor.org/info/rfc5771>

=item

L<RFC5892 "The Unicode Code Points and Internationalized Domain Names for Applications (IDNA)"|http://www.rfc-editor.org/info/rfc5892>

=item

L<RFC5936 "DNS Zone Transfer Protocol (AXFR)"|http://www.rfc-editor.org/info/rfc5936>

=item

L<RFC6052 "IPv6 Addressing of IPv4/IPv6 Translators"|http://www.rfc-editor.org/info/rfc6052>

=item

L<RFC6333 "Dual-Stack Lite Broadband Deployments Following IPv4 Exhaustion"|http://www.rfc-editor.org/info/rfc6333>

=item

L<RFC6598 "IANA-Reserved IPv4 Prefix for Shared Address Space"|http://www.rfc-editor.org/info/rfc6598>

=item

L<RFC6666 "A Discard Prefix for IPv6"|http://www.rfc-editor.org/info/rfc6666>

=item

L<RFC6781 "DNSSEC Operational Practices, Version 2"|http://www.rfc-editor.org/info/rfc6781>

=item

L<RFC6890 "Special-Purpose IP Address Registries"|http://www.rfc-editor.org/info/rfc6890>

=item

L<RFC6891 "Extension Mechanisms for DNS (EDNS(0))"|http://www.rfc-editor.org/info/rfc6891>

=item

L<RFC7050 "Discovery of the IPv6 Prefix Used for IPv6 Address Synthesis"|http://www.rfc-editor.org/info/rfc7050>

=back

=cut
