NAME
    POE::Component::Server::DNS - A non-blocking, concurrent DNS server POE
    component

VERSION
    version 0.28

SYNOPSIS
      use strict;
      use Net::DNS::RR;
      use POE qw(Component::Server::DNS);

      my $dns_server = POE::Component::Server::DNS->spawn( alias => 'dns_server' );

      POE::Session->create(
            package_states => [ 'main' => [ qw(_start handler log) ], ],
      );

      $poe_kernel->run();
      exit 0;

      sub _start {
        my ($kernel,$heap) = @_[KERNEL,HEAP];

        # Tell the component that we want log events to go to 'log'
        $kernel->post( 'dns_server', 'log_event', 'log' );

        # register a handler for any foobar.com suffixed domains
        $kernel->post( 'dns_server', 'add_handler',
            {
              event => 'handler',
              label => 'foobar',
              match => 'foobar\.com$',
            }
        );
        undef;
      }

      sub handler {
        my ($qname,$qclass,$qtype,$callback) = @_[ARG0..ARG3];
        my ($rcode, @ans, @auth, @add);

        if ($qtype eq "A") {
          my ($ttl, $rdata) = (3600, "10.1.2.3");
          push @ans, Net::DNS::RR->new("$qname $ttl $qclass $qtype $rdata");
          $rcode = "NOERROR";
        } else {
          $rcode = "NXDOMAIN";
        }

        $callback->($rcode, \@ans, \@auth, \@add, { aa => 1 });
        undef;
      }

      sub log {
        my ($ip_port,$net_dns_packet) = @_[ARG0..ARG1];
        $net_dns_packet->print();
        undef;
      }

DESCRIPTION
    POE::Component::Server::DNS is a POE component that implements a DNS
    server.

    It uses POE::Component::Client::DNS to handle resolving when configured
    as 'forward_only' and Net::DNS::Resolver::Recurse wrapped by
    POE::Component::Generic to perform recursion.

    One may add handlers to massage and manipulate responses to particular
    queries which is vaguely modelled after Net::DNS::Nameserver.

CONSTRUCTOR
    spawn
        Starts a POE::Component::Server::DNS component session and returns
        an object. Takes a number of optional arguments:

          "alias", an alias to address the component by;
          "port", which udp port to listen on. Default is 53, which requires 'root' privilege on UN*X type systems;
          "address", which local IP address to listen on.  Default is INADDR_ANY;
          "resolver_opts", a set of options to pass to the POE::Component::Client::DNS constructor;
          "forward_only", be a forwarding only DNS server. Default is 0, be recursive.
          "no_clients", do not spawn client code (See following notes);

        "no_clients" disables the spawning of client code
        (PoCo::Client::DNS, Net::DNS::Resolver::Recursive), and doesn't
        attempt to forward or recurse inbound requests. Any request not
        handled by one of your handlers will be "REFUSED". Saves some
        resources when you intend your server to be authoritative only (as
        opposed to a general resolver for DNS client software to point at
        directly). Additionally, this argument changes the default
        "Recursion Available" flag in responses to off instead of on.

METHODS
    These are methods that may be used with the object returned by spawn().

    session_id
        Returns the POE::Session ID of the component's session.

    resolver
        Returns a reference to the POE::Component::Client::DNS object.

    shutdown
        Terminates the component and associated resolver.

    sockport
        Returns the port of the socket that the component is listening on.

INPUT EVENTS
    These are states that the component will accept:

    add_handler
        Accepts a hashref as an argument with the following keys:

          "event", the event the component will post to, mandatory;
          "label", a unique name for this handler, mandatory;
          "match", a regex expression ( without // ) to match against the host part of queries, mandatory;
          "session", the session where this handler event should be sent to, defaults to SENDER;

        See OUTPUT EVENTS for details of what happens when a handler is
        triggered.

    del_handler
        Accepts a handler label to remove.

    log_event
        Tells the component that a session wishes to receive or stop
        receiving DNS log events. Specify the event you wish to receive log
        events as the first argument. If no event is specified you stop
        receiving log events.

    shutdown
        Terminates the component and associated resolver.

HANDLER EVENTS
    These events are triggered by a DNS query matching a handler. The
    applicable event is fired in the requested session with the following
    paramters:

      ARG0, query name
      ARG1, query class
      ARG2, query type
      ARG3, a callback coderef
      ARG4, the IP address and port of the requestor, 'IPaddr:port'

    Do your manipulating then use the callback to fire the response back to
    the component, returning a response code and references to the answer,
    authority, and additional sections of the response. For advanced usage
    there is an optional argument containing an hashref with the settings
    for the aa, ra, and ad header bits. The argument is of the form { ad =>
    1, aa => 0, ra => 1 }.

      $callback->( $rcode, \@ans, \@auth, \@add, { aa => 1 } );

LOG EVENTS
    These events are triggered whenever a DNS response is sent to a client.

      ARG0, the IP address and port of the requestor, 'IPaddr:port';
      ARG1, the Net::DNS::Packet object;

    See Net::DNS::Packet for details.

HISTORY
    The component's genesis was inspired by Jan-Pieter's 'Fun with POE' talk
    at YAPC::EU 2006, which lay much of the ground-work code such as the
    POE::Driver and POE::Filter used internally. BinGOs wrapped it all up in
    a component, added the tests ( borrowed shamelessly from
    POE::Component::Client::DNS's testsuite ) and documentation.

    Other suggestions as to the API were provided by Ben 'integral' Smith.

    Rocco Caputo brought POE::Component::Client::DNS to the party.

SEE ALSO
    POE::Component::Client::DNS

    POE::Component::Generic

    Net::DNS

    Net::DNS::Packet

AUTHORS
    *   Chris Williams <chris@bingosnet.co.uk>

    *   Jan-Pieter Cornet <johnpc@xs4all.nl>

    *   Brandon Black <blblack@gmail.com>

COPYRIGHT AND LICENSE
    This software is copyright (c) 2012 by Chris Williams, Jan-Pieter Cornet
    and Brandon Black.

    This is free software; you can redistribute it and/or modify it under
    the same terms as the Perl 5 programming language system itself.

