NAME

DNS::Unbound - libunbound in Perl

SYNOPSIS

    my $dns = DNS::Unbound->new()->set_option( verbosity => 2 );

    # This appears to be safe:
    $dns->enable_threads();

    my $verbosity = $dns->get_option( 'verbosity' );

    $dns->set_option( verbosity => 1 + $verbosity );

Synchronous queries:

    my $res_hr = $dns->resolve( 'cpan.org', 'NS' );

    # See below about encodings in “data”.
    my @ns = map { $dns->decode_name($_) } @{ $res_hr->data() };

Asynchronous queries use the “Promise” pattern:

    my $query1 = $dns->resolve_async( 'usa.gov', 'A' )->then(
        sub { my $data = shift()->data(); ... },  # success handler
        sub { ... },                              # failure handler
    );

    my $query2 = $dns->resolve_async( 'in-addr.arpa', 'NS' )->then(
        sub { ... },
        sub { ... },
    );

    # As an alternative to wait(), see below for documentation on
    # the fd(), poll(), and process() methods.

    $dns->wait();

See examples/ in the distribution for demonstrations of making this module interface with AnyEvent or IO::Async.

DESCRIPTION

This library is a Perl interface to NLNetLabs’s widely-used Unbound recursive DNS resolver.

METHODS

CLASS->new()

Instantiates this class.

$result_hr = OBJ->resolve( $NAME, $TYPE [, $CLASS ] )

Runs a synchronous query for a given $NAME and $TYPE. $TYPE may be expressed numerically or, for convenience, as a string. $CLASS is optional and defaults to 1 (IN), which is probably what you want.

Returns a DNS::Unbound::Result instance.

NOTE: libunbound doesn’t seem to offer effective controls for timing out a synchronous query. If timeouts are relevant for you, you probably need to use resolve_async() instead.

$query = OBJ->resolve_async( $NAME, $TYPE [, $CLASS ] );

Like resolve() but starts an asynchronous query rather than a synchronous one.

This returns an instance of DNS::Unbound::AsyncQuery (a subclass thereof, to be precise).

See below for the methods you’ll need to use in tandem with this one.

OBJ->enable_threads()

Sets OBJ’s asynchronous queries to use threads rather than forking. Off by default. Throws an exception if called after an asynchronous query has already been sent.

Returns OBJ.

NOTE: Despite Perl’s iffy relationship with threads, this appears to work without issue.

OBJ->set_option( $NAME => $VALUE )

Sets a configuration option. Returns OBJ.

Note that this is basically just a passthrough to the underlying ub_ctx_set_option() function and is thus subject to the same limitations as that function; for example, you can’t set verbosity after the configuration has been “finalized”. (So use debuglevel() for that instead.)

$value = OBJ->get_option( $NAME )

Gets a configuration option’s value.

OBJ->debuglevel( $LEVEL )

Sets the debug level (an integer). Returns OBJ.

As of libunbound v1.9.2, this is just a way to set the verbosity option regardless of whether the configuration is finalized.

OBJ->debugout( $FD_OR_FH )

Accepts a file descriptor or Perl filehandle and designates that as the destination for libunbound diagnostic information.

Returns OBJ.

$str = CLASS->unbound_version()

Gives the libunbound version string.

METHODS FOR ALTERING RESOLVER LOGIC

The following parallel their equivalents in libunbound. They return OBJ and throw errors on failure.

OBJ->hosts( $FILENAME )

OBJ->resolveconf( $FILENAME )

METHODS FOR DEALING WITH ASYNCHRONOUS QUERIES

Unless otherwise noted, the following methods correspond to their equivalents in libunbound. They return the same values as the libunbound equivalents.

OBJ->poll()

OBJ->fd()

OBJ->wait()

OBJ->process()

OBJ->count_pending_queries()

Returns the number of outstanding asynchronous queries.

METHODS FOR DEALING WITH DNSSEC

The following correspond to their equivalents in libunbound and will only work if the underlying libunbound version supports them.

They return OBJ and throw errors on failure.

OBJ->add_ta()

OBJ->add_ta_autr()

OBJ->add_ta_file()

OBJ->trustedkeys()

CONVENIENCE FUNCTIONS

The following may be called either as object methods or as static functions (but not as class methods). In addition to these, Socket provides the inet_ntoa() and inet_ntop() functions for decoding the values of A and AAAA records.

NOTE: Consider parsing DNS::Unbound::Result’s answer_packet() with Net::DNS::Packet as a more robust, albeit heavier, way to parse query result data.

$decoded = decode_name($encoded)

Decodes a DNS name. Useful for, e.g., NS, CNAME, and PTR query results.

Note that this function’s return will normally include a trailing . because of the trailing NUL byte in an encoded DNS name. This is normal and expected.

$strings_ar = decode_character_strings($encoded)

Decodes a list of character-strings into component strings, returned as an array reference. Useful for TXT query results.

LICENSE & COPYRIGHT

Copyright 2019 Gasper Software Consulting.

This library is licensed under the same terms as Perl itself.

REPOSITORY

https://github.com/FGasper/p5-DNS-Unbound

THANK YOU

Special thanks to ATOOMIC for making some helpful review notes.

cpanm DNS::Unbound

perl -MCPAN -e shell
install DNS::Unbound