POE::Component::Client::DNS::Recursive - A recursive DNS client for POE

POE-Component-Client-DNS-Recursive documentation Contained in the POE-Component-Client-DNS-Recursive distribution.

Index

Code Index:

NAME

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POE::Component::Client::DNS::Recursive - A recursive DNS client for POE

SYNOPSIS

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  use strict;
  use warnings;
  use Getopt::Long;

  use POE qw(Component::Client::DNS::Recursive);

  my $trace;
  GetOptions ('trace' => \$trace);

  my $host = shift || die "Nothing to query\n";
  my $type = shift;

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

  $poe_kernel->run();
  exit 0;

  sub _start {
    POE::Component::Client::DNS::Recursive->resolve(
          event => '_response',
          host => $host,
  	( $type ? ( type => $type ) : () ),
  	( $trace ? ( trace => $_[SESSION]->postback( '_trace' ) ) : () ),
    );
    return;
  }

  sub _trace {
    my $packet = $_[ARG1]->[0];
    return unless $packet;
    print $packet->string;
    return;
  }

  sub _response {
    my $packet = $_[ARG0]->{response};
    return unless $packet;
    print $packet->string;
    return;
  }

DESCRIPTION

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POE::Component::Client::DNS::Recursive is a POE component that implements a recursive DNS client.

POE sessions and components can spawn a POE::Component::Client::DNS::Recursive instance to perform a DNS query. The component will perform its task and return the results to the requesting session.

One may also enable tracing of the delegation path from the root name servers for the name being looked up.

CONSTRUCTOR

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resolve

Takes a number of options, only those marked as mandatory are required:

  'event', the event to emit when completed, mandatory;
  'host', what to look up, mandatory;
  'type', defaults to 'A' or 'PTR' if 'host' appears to be an IP address;
  'class', defaults to 'IN';
  'port', the port to use for DNS requests. Default is 53;
  'session', provide an alternative session to send the resultant event to;
  'trace', the event to send trace information to;
  'nameservers', an arrayref of IP addresses that the poco will use instead of built-in 'hints';
  'context', user defined data. Can be anything that can be stored in a scalar;

event and trace are discussed in the OUTPUT EVENTS section below.

event and trace may also be POE::Session postbacks.

session is only required if one wishes to send the resultant events to a different session than the calling one, or if the component is spawned with the POE::Kernel as its parent.

OUTPUT EVENTS

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The output events from the component as specified in the resolve constructor.

If you have opted to use postbacks, then these parameters will be passed in the arrayref in ARG1.

event

Emitted when the query has finished.

ARG0 will contain a hashref with the following fields:

  host     => the host requested,
  type     => the type requested,
  class    => the class requested,
  context  => the context that was passed to us,
  response => a Net::DNS::Packet object,
  error    => an error message ( if applicable )

response contains a Net::DNS::Packet object on success or undef if the lookup failed. The Net::DNS::Packet object describes the response to the program's request. It may contain several DNS records. Please consult Net::DNS and Net::DNS::Packet for more information.

error contains a description of any error that has occurred. It is only valid if response is undefined.

trace

Emitted whenever an element of the delegation path from the root servers is found.

ARG0 will be a Net::DNS::Packet object.

AUTHOR

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Chris BinGOs Williams <chris@bingosnet.co.uk>

LICENSE

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Copyright © Chris Williamss.

This module may be used, modified, and distributed under the same terms as Perl itself. Please see the license that came with your Perl distribution for details.

SEE ALSO

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POE::Component::Client::DNS

Perl Programming

POE-Component-Client-DNS-Recursive documentation Contained in the POE-Component-Client-DNS-Recursive distribution. 
package POE::Component::Client::DNS::Recursive;

use strict;
use warnings;
use Carp;
use Socket;
use File::Spec;
use Net::IP qw(:PROC);
use IO::Socket::INET;
use POE qw(NFA);
use Net::DNS::Packet;
use vars qw($VERSION);

$VERSION = '1.00';

my @hc_hints = qw(
198.41.0.4
192.58.128.30
192.112.36.4
202.12.27.33
192.5.5.241
128.63.2.53
192.36.148.17
192.33.4.12
192.228.79.201
199.7.83.42
128.8.10.90
193.0.14.129
192.203.230.10
);

sub resolve {
  my $package = shift;
  my %opts = @_;
  $opts{lc $_} = delete $opts{$_} for keys %opts;
  croak "$package requires a 'host' argument\n"
	unless $opts{host};
  croak "$package requires an 'event' argument\n"
	unless $opts{event};
  $opts{nameservers} = [ ] unless $opts{nameservers} and ref $opts{nameservers} eq 'ARRAY';
  @{ $opts{nameservers} } = grep { ip_get_version( $_ ) } @{ $opts{nameservers} };
  my $options = delete $opts{options};
  my $self = bless \%opts, $package;
  my $sender = $poe_kernel->get_active_session();
  $self->{_sender} = $sender;
  POE::NFA->spawn(
  object_states => {
    initial => [
	$self => { setup => '_start' },
	$self => [qw(_default)],
    ],
    hints   => [
	$self => {
	_init  => '_hints_go',
        _setup => '_send',
        _read  => '_hints',
        _timeout => '_hints_timeout',
	},
    ],
    query   => [
	$self => {
        _setup => '_send',
        _read  => '_query',
        _timeout => '_query_timeout',
	},
    ],
    done    => [
        $self => [qw(_close _error)],
    ],
  },
  runstate => $self,
  )->goto_state( 'initial' => 'setup' );
  return $self;
}

sub _default {
  return 0;
}

sub _start {
  my ($kernel,$machine,$runstate) = @_[KERNEL,MACHINE,RUNSTATE];
  my $sender = $runstate->{_sender};
  if ( $kernel == $sender and !$runstate->{session} ) {
	croak "Not called from another POE session and 'session' wasn't set\n";
  }
  my $sender_id;
  if ( $runstate->{session} ) {
    if ( my $ref = $kernel->alias_resolve( $runstate->{session} ) ) {
	$sender_id = $ref->ID();
    }
    else {
	croak "Could not resolve 'session' to a valid POE session\n";
    }
  }
  else {
    $sender_id = $sender->ID();
  }
  $kernel->refcount_increment( $sender_id, __PACKAGE__ )
     unless ref $runstate->{event} eq 'POE::Session::AnonEvent';
  $kernel->detach_myself();
  $runstate->{sender_id} = $sender_id;
  my $type = $runstate->{type} || ( ip_get_version( $runstate->{host} ) ? 'PTR' : 'A' );
  my $class = $runstate->{class} || 'IN';
  $runstate->{qstack} = [ ];
  $runstate->{current} = {
        query => $runstate->{host},
        type  => $type,
        packet => Net::DNS::Packet->new($runstate->{host},$type,$class),
  };
  $runstate->{socket} = IO::Socket::INET->new( Proto => 'udp' );
  $machine->goto_state( 'hints', '_init' );
  return;
}

sub _hints_go {
  my ($kernel,$machine,$runstate) = @_[KERNEL,MACHINE,RUNSTATE];
  my $hints;
  if ( scalar @{ $runstate->{nameservers} } ) {
     $hints = $runstate->{nameservers};
  }
  else {
     $hints = \@hc_hints;
  }
  $runstate->{_hints} = $hints;
  $machine->goto_state( 'hints', '_setup', Net::DNS::Packet->new('.','NS','IN'), splice( @$hints, rand($#{$hints}), 1) );
  return;
}

sub _send {
  my ($machine,$runstate,$state,$packet,$ns) = @_[MACHINE,RUNSTATE,STATE,ARG0,ARG1];
  my $socket = $runstate->{socket};
  my $data = $packet->data;
  my $server_address;
  eval {
     $server_address = pack_sockaddr_in( ( $runstate->{port} || 53 ), inet_aton($ns) );
  };
  unless ( $server_address ) {
     warn "'$ns' didn't produce an valid server address\n";
     $machine->goto_state( 'done', '_error', $@ );
     return;
  }
  unless ( send( $socket, $data, 0, $server_address ) == length($data) ) {
     $machine->goto_state( 'done', '_error', $! );
     return;
  }
  $poe_kernel->select_read( $socket, '_read' );
  $poe_kernel->delay( '_timeout', $runstate->{timeout} || 5 );
  return;
}

sub _hints {
  my ($machine,$runstate,$socket) = @_[MACHINE,RUNSTATE,ARG0];
  $poe_kernel->delay( '_timeout' );
  my $packet = _read_socket( $socket );
    my %hints;
    if (my @ans = $packet->answer) {
      foreach my $rr (@ans) {
        if ($rr->name =~ /^\.?$/ and
            $rr->type eq "NS") {
          # Found root authority
          my $server = lc $rr->rdatastr;
          $server =~ s/\.$//;
          $hints{$server} = [];
        }
      }
      foreach my $rr ($packet->additional) {
        if (my $server = lc $rr->name){
          if ( $rr->type eq "A") {
            if ($hints{$server}) {
              push @{ $hints{$server} }, $rr->rdatastr;
            }
          }
        }
      }
    }
  if ( $runstate->{trace} ) {
    if ( ref $runstate->{trace} eq 'POE::Session::AnonEvent' ) {
       $runstate->{trace}->( $packet );
    }
    else {
       $poe_kernel->post( $runstate->{sender_id}, $runstate->{trace}, $packet );
    }
  }
  $runstate->{hints} = \%hints;
  my @ns = _ns_from_cache( $runstate->{hints} );
  unless ( scalar @ns ) {
     $machine->goto_state( 'hints', '_init' );
     return;
  }
  my $query = $runstate->{current};
  $query->{servers} = \@ns;
  my ($nameserver) = splice @ns, rand($#ns), 1;
  $machine->goto_state( 'query', '_setup', $query->{packet}, $nameserver );
  return;
}

sub _hints_timeout {
  my ($machine,$runstate) = @_[MACHINE,RUNSTATE];
  my $hints = $runstate->{_hints};
  if ( scalar @{ $hints } ) {
     $machine->goto_state( 'hints', '_setup', Net::DNS::Packet->new('.','NS','IN'), splice( @$hints, rand($#{$hints}), 1) );
  }
  elsif ( defined $runstate->{nameservers} ) {
     $machine->goto_state( 'hints', '_init' );
     return;
  }
  else {
     $machine->goto_state( 'done', '_error', 'Ran out of authority records' );
  }
  return;
}

sub _query {
  my ($machine,$runstate,$socket) = @_[MACHINE,RUNSTATE,ARG0];
  $poe_kernel->delay( '_timeout' );
  my $packet = _read_socket( $socket );
  my @ns;
  my $status = $packet->header->rcode;
  if ( $status ne 'NOERROR' ) {
	$machine->goto_state( 'done', '_error', $status );
        return;
  }
  if (my @ans = $packet->answer) {
     # This is the end of the chain.
     unless ( scalar @{ $runstate->{qstack} } ) {
	$machine->goto_state( 'done', '_close', $packet );
        return;
     }
     # Okay we have queries pending.
     push @ns, $_->rdatastr for grep { $_->type eq 'A' } @ans;
     $runstate->{current} = pop @{ $runstate->{qstack} };
  }
  else {
     if ( $runstate->{trace} ) {
        $poe_kernel->post( $runstate->{sender_id}, $runstate->{trace}, $packet );
     }
     my $authority = _authority( $packet );
     @ns = _ns_from_cache( $authority );
     unless ( scalar @ns ) {
        $runstate->{current}->{authority} = $authority;
        push @{ $runstate->{qstack} }, $runstate->{current};
        my $host = ( keys %{ $authority } )[rand scalar keys %{ $authority }];
        delete $authority->{$host};
        $runstate->{current} = {
           query => $host,
           type  => 'A',
           packet => Net::DNS::Packet->new($host,'A','IN'),
        };
        @ns = _ns_from_cache( $runstate->{hints} );
     }
  }
  my $query = $runstate->{current};
  $query->{servers} = \@ns;
  my ($nameserver) = splice @ns, rand($#ns), 1;
  $poe_kernel->yield( '_setup', $query->{packet}, $nameserver );
  return;
}

sub _query_timeout {
  my ($machine,$runstate) = @_[MACHINE,RUNSTATE];
  my $query = $runstate->{current};
  my $servers = $query->{servers};
  my ($nameserver) = splice @{ $servers }, rand($#{ $servers }), 1;
  # actually check here if there is something on the stack.
  # pop off the most recent, and get the next authority record
  # push back on to the stack and do a lookup for the authority
  # record. No authority records left, then complain and bailout.
  unless ( $nameserver ) {
    if ( scalar @{ $runstate->{qstack} } ) {
        $runstate->{current} = pop @{ $runstate->{qstack} };
        my $host = ( keys %{ $runstate->{current}->{authority} } )[rand scalar keys %{ $runstate->{current}->{authority} }];
        unless ( $host ) { # Oops
           $machine->goto_state( 'done', '_error', 'Ran out of authority records' );
           return; # OMG
	}
        delete $runstate->{current}->{authority}->{ $host };
        push @{ $runstate->{qstack} }, $runstate->{current};
        $runstate->{current} = {
           query => $host,
           type  => 'A',
           packet => Net::DNS::Packet->new($host,'A','IN'),
        };
        my @ns = _ns_from_cache( $runstate->{hints} );
        $runstate->{current}->{servers} = \@ns;
        ($nameserver) = splice @ns, rand($#ns), 1;
    }
    else {
        $machine->goto_state( 'done', '_error', 'Ran out of authority records' );
        return; # OMG
    }
  }
  unless ( $nameserver ) {  # SERVFAIL? maybe
    $machine->goto_state( 'done', '_error', 'Ran out of nameservers to query' );
    return;
  }
  $poe_kernel->yield( '_setup', $query->{packet}, $nameserver );
  return;
}

sub _error {
  my ($kernel,$machine,$runstate,$error) = @_[KERNEL,MACHINE,RUNSTATE,ARG0];
  $kernel->select_read( $runstate->{socket} ); # Just in case
  my $resp = {};
  $resp->{$_} = $runstate->{$_} for qw(host type class context);
  $resp->{response} = undef;
  $resp->{error} = $error;
  delete $runstate->{trace};
  if ( ref $runstate->{event} eq 'POE::Session::AnonEvent' ) {
     my $postback = delete $runstate->{event};
     $postback->( $resp );
  }
  else {
     $kernel->post( $runstate->{sender_id}, $runstate->{event}, $resp );
     $kernel->refcount_decrement( $runstate->{sender_id}, __PACKAGE__ );
  }
  return;
}

sub _close {
  my ($kernel,$machine,$runstate,$packet) = @_[KERNEL,MACHINE,RUNSTATE,ARG0];
  $kernel->select_read( $runstate->{socket} ); # Just in case
  my $resp = {};
  $resp->{$_} = $runstate->{$_} for qw(host type class context);
  $resp->{response} = $packet;
  delete $runstate->{trace};
  if ( ref $runstate->{event} eq 'POE::Session::AnonEvent' ) {
     my $postback = delete $runstate->{event};
     $postback->( $resp );
  }
  else {
     $kernel->post( $runstate->{sender_id}, $runstate->{event}, $resp );
     $kernel->refcount_decrement( $runstate->{sender_id}, __PACKAGE__ );
  }
  return;
}

sub _authority {
  my $packet = shift || return;
    my %hints;
    if (my @ans = $packet->authority) {
      foreach my $rr (@ans) {
            if ( $rr->type eq 'NS') {
          # Found root authority
          my $server = lc $rr->rdatastr;
          $server =~ s/\.$//;
          $hints{$server} = [];
        }
      }
      foreach my $rr ($packet->additional) {
        if (my $server = lc $rr->name){
              push @{ $hints{$server} }, $rr->rdatastr if $rr->type eq 'A' and $hints{$server};
        }
      }
    }
  return \%hints;
}

sub _read_socket {
  my $socket = shift || return;
  $poe_kernel->select_read( $socket );
  my $message;
  unless ( $socket->recv( $message, 512 ) ) {
     warn "$!\n";
     return;
  }
  my ($in,$err);
  {
     local *STDOUT;
     open STDOUT, '>' . File::Spec->devnull();
     ($in, $err) = Net::DNS::Packet->new( \$message, 1 );
  }
  if ( $err ) {
     warn "$err\n";
     return;
  }
  my $size = length( $in->data );
  unless ( $size ) {
     warn "Bad size\n";
     return;
  }
  return $in;
}

sub _ns_from_cache {
  my $hashref = shift || return;
  my @ns;
  foreach my $ns (keys %{ $hashref }) {
    push @ns, @{ $hashref->{$ns} } if scalar @{ $hashref->{$ns} };
  }
  return @ns;
}

'Recursive lookup, recursive lookup, recursive lookup ....';
__END__