# NAME DNS::Unbound - Query DNS recursively via [libunbound](https://www.nlnetlabs.nl/documentation/unbound/libunbound/) # 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](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Using_promises). Assuming you’re using an off-the-shelf event loop, you can do something like: my $dns = DNS::Unbound::AnyEvent->new(); 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 { ... }, ); You can also integrate with a custom event loop; see ["EVENT LOOPS"](#event-loops) below. # DESCRIPTION
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Typical DNS lookups involve a request to a local server that caches information from DNS. The caching makes it fast, but it also means updates to DNS aren’t always available via that local server right away. Most applications don’t need to care and so can enjoy the speed of cached results. Applications that need up-to-date DNS query results, though, need _fully-recursive_ DNS queries. NLnet Labs’s [libunbound](https://www.nlnetlabs.nl/documentation/unbound/libunbound/) is a popular solution for such queries; the present Perl module is an interface to that library. # CHARACTER ENCODING DNS doesn’t know about character encodings, so neither does Unbound. Thus, all strings given to this module must be **byte** **strings**. All returned strings will be byte strings as well. # EVENT LOOPS This distribution includes the classes [DNS::Unbound::AnyEvent](https://metacpan.org/pod/DNS%3A%3AUnbound%3A%3AAnyEvent), [DNS::Unbound::IOAsync](https://metacpan.org/pod/DNS%3A%3AUnbound%3A%3AIOAsync), and [DNS::Unbound::Mojo](https://metacpan.org/pod/DNS%3A%3AUnbound%3A%3AMojo), which provide out-of-the-box compatibility with those popular event loop interfaces. You should probably use one of these. You can also integrate with a custom event loop via the `fd()` method of this class: wait for that file descriptor to be readable, then call this class’s `perform()` method. # MEMORY LEAK DETECTION Objects in this namespace will, if left alive at global destruction, throw a warning about memory leaks. To silence these warnings, either allow all queries to complete, or cancel queries you no longer care about. # CONSTANTS The following from `libunbound/context.h` are defined here: `UB_NOERROR`, `UB_SOCKET`, `UB_NOMEM`, `UB_SYNTAX`, `UB_SERVFAIL`, `UB_FORKFAIL`, `UB_AFTERFINAL`, `UB_INITFAIL`, `UB_PIPE`, `UB_READFILE`, `UB_NOID` # 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](https://metacpan.org/pod/DNS%3A%3AUnbound%3A%3AResult) 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](https://metacpan.org/pod/DNS%3A%3AUnbound%3A%3AAsyncQuery) (a subclass thereof, to be precise). If you’re using one of the special event interface subclasses (e.g., [DNS::Unbound::IOAsync](https://metacpan.org/pod/DNS%3A%3AUnbound%3A%3AIOAsync)) then the returned promise will resolve on its own. Otherwise, [see below](#custom-event-loop-integration) 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_. ## _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 ) # CUSTOM EVENT LOOP INTEGRATION Unless otherwise noted, the following methods correspond to their equivalents in libunbound. They return the same values as the libunbound equivalents. You don’t need these if you use one of the event loop subclasses (which is recommended). ## _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( $TA ) ## _OBJ_->add\_ta\_autr( $PATH ) ## _OBJ_->add\_ta\_file( $PATH ) ## _OBJ_->trustedkeys( $PATH ) # 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](https://metacpan.org/pod/Socket) provides the `inet_ntoa()` and `inet_ntop()` functions for decoding the values of `A` and `AAAA` records. **NOTE:** Consider parsing [DNS::Unbound::Result](https://metacpan.org/pod/DNS%3A%3AUnbound%3A%3AResult)’s `answer_packet()` with [Net::DNS::Packet](https://metacpan.org/pod/Net%3A%3ADNS%3A%3APacket) 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. # SEE ALSO [Net::DNS::Resolver::Recurse](https://metacpan.org/pod/Net%3A%3ADNS%3A%3AResolver%3A%3ARecurse) provides comparable logic to this module in pure Perl. Like Unbound, it is maintained by ["NLnet Labs"](#nlnet-labs). # LICENSE & COPYRIGHT Copyright 2019-2021 Gasper Software Consulting. This library is licensed under the same terms as Perl itself. # REPOSITORY [https://github.com/FGasper/p5-DNS-Unbound](https://github.com/FGasper/p5-DNS-Unbound) # THANK YOU Special thanks to [ATOOMIC](https://metacpan.org/author/ATOOMIC) for making some helpful review notes.