NAME
    "IO::Async::Resolver::DNS" - resolve DNS queries using "IO::Async"

SYNOPSIS
     use IO::Async::Loop;
     use IO::Async::Resolver::DNS;
 
     my $loop = IO::Async::Loop->new;
     my $resolver = $loop->resolver;
 
     $resolver->res_query(
        dname => "cpan.org",
        type  => "MX",
        on_resolved => sub {
           my ( $pkt ) = @_;
 
           foreach my $mx ( $pkt->answer ) {
              next unless $mx->type eq "MX";
 
              printf "preference=%d exchange=%s\n",
                 $mx->preference, $mx->exchange;
           }
           $loop->loop_stop;
        },
        on_error => sub { die "Cannot resolve - $_[-1]\n" },
     );
 
     $loop->loop_forever;

DESCRIPTION
    This module extends the IO::Async::Resolver class with extra methods and
    resolver functions to perform DNS-specific resolver lookups. It does not
    directly provide any methods or functions of its own.

    These functions are provided for performing DNS-specific lookups, to
    obtain "MX" or "SRV" records, for example. For regular name resolution,
    the usual "getaddrinfo" and "getnameinfo" methods on the standard
    "IO::Async::Resolver" should be used.

    If Net::LibResolv is installed then it will be used for actually sending
    and receiving DNS packets, in preference to a internally-constructed
    Net::DNS::Resolver object. "Net::LibResolv" will be more efficient and
    shares its implementation with the standard resolver used by the rest of
    the system. "Net::DNS::Resolver" reimplements the logic itself, so it
    may have differences in behaviour from that provided by libresolv. The
    ability to use the latter is provided to allow for an XS-free dependency
    chain, or for other situations where "Net::LibResolv" is not available.

RESOLVER METHODS
  $resolver->res_query( %params )
    Performs a resolver query on the name, class and type, and invokes a
    continuation when a result is obtained.

    Takes the following named parameters:

    dname => STRING
            Domain name to look up

    type => STRING
            Name of the record type to look up (e.g. "MX")

    class => STRING
            Name of the record class to look up. Defaults to "IN" so
            normally this argument is not required.

    on_resolved => CODE
            Continuation which is invoked after a successful lookup. Will be
            passed a Net::DNS::Packet object containing the result.

             $on_resolved->( $pkt )

    on_error => CODE
            Continuation which is invoked after a failed lookup.

  $resolver->res_search( %params )
    Performs a resolver query on the name, class and type, and invokes a
    continuation when a result is obtained. Identical to "res_query" except
    that it additionally implements the default domain name search
    behaviour.

AUTHOR
    Paul Evans <leonerd@leonerd.org.uk>