Net::DNS::Resolver::Programmable(3) User Contributed Perl Documentation Net::DNS::Resolver::Programmable(3)

Net::DNS::Resolver::Programmable - programmable DNS resolver class for offline emulation of DNS

use Net::DNS::Resolver::Programmable;
use Net::DNS::RR;

my $resolver = Net::DNS::Resolver::Programmable->new(
    records         => {
        ''     => [
            Net::DNS::RR->new('     NS'),
            Net::DNS::RR->new('     A')
        ''  => [
            Net::DNS::RR->new('  A')

    resolver_code   => sub {
        my ($domain, $rr_type, $class) = @_;
        return ($result, $aa, @rrs);

Net::DNS::Resolver::Programmable is a Net::DNS::Resolver descendant class that allows a virtual DNS to be emulated instead of querying the real DNS. A set of static DNS records may be supplied, or arbitrary code may be specified as a means for retrieving DNS records, or even generating them on the fly.

The following constructor is provided:
new(%options): returns Net::DNS::Resolver::Programmable
Creates a new programmed DNS resolver object.

%options is a list of key/value pairs representing any of the following options:

A reference to a hash of arrays containing a static set of Net::DNS::RR objects. The hash entries must be indexed by fully qualified domain names (lower-case, without any trailing dots), and the entries themselves must be arrays of the RR objects pertaining to these domain names. For example:

records => {
    ''     => [
        Net::DNS::RR->new('     NS'),
        Net::DNS::RR->new('     A')
    '' => [
        Net::DNS::RR->new(' A')
    ''  => [
        Net::DNS::RR->new('  A')

If this option is specified, the resolver retrieves requested RRs from this data structure.

A code reference used as a call-back for dynamically retrieving requested RRs.

The code must take the following query parameters as arguments: the domain, RR type, and class.

It must return a list composed of: the response's RCODE (by name, as returned by Net::DNS::Header->rcode), the "aa" (authoritative answer) flag (boolean, use undef if you don't care), and the Net::DNS::RR answer objects. If an error string is returned instead of a valid RCODE, a Net::DNS::Packet object is not constructed but an error condition for the resolver is signaled instead.

For example:

resolver_code => sub {
    my ($domain, $rr_type, $class) = @_;
    return ($result, $aa, @rrs);

If both this and the "records" option are specified, then statically programmed records are used in addition to any that are returned by the configured resolver code.

These Net::DNS::Resolver options are also meaningful with Net::DNS::Resolver::Programmable. See Net::DNS::Resolver for their descriptions.

The following instance methods of Net::DNS::Resolver are also supported by Net::DNS::Resolver::Programmable:
search: returns Net::DNS::Packet
query: returns Net::DNS::Packet
send: returns Net::DNS::Packet
Performs an offline DNS query, using the statically programmed DNS RRs and/or the configured dynamic resolver code. See the "new" constructor's "records" and "resolver_code" options. See the descriptions of search, query, and send for details about the calling syntax of these methods.
string: returns string
searchlist: returns list of string
defnames: returns boolean
dnsrch: returns boolean
debug: returns boolean
errorstring: returns string
answerfrom: returns string
answersize: returns integer
See "METHODS" in Net::DNS::Resolver.

Currently the following methods of Net::DNS::Resolver are not supported: axfr, axfr_start, axfr_next, nameservers, port, srcport, srcaddr, bgsend, bgread, bgisready, tsig, retrans, retry, recurse, usevc, tcp_timeout, udp_timeout, persistent_tcp, persistent_udp, igntc, dnssec, cdflag, udppacketsize. The effects of using these on Net::DNS::Resolver::Programmable objects are undefined.


For availability, support, and license information, see the README file included with Net::DNS::Resolver::Programmable.

David Precious (BIGPRESH) "<>" took on maintainership in July 2017

Original author Julian Mehnle "<>"

Dick Franks (rwfranks)

(This section was added by BIGPRESH in July 2017, so currently omits acknowledgements for those who contributed things in the past; I may retrospectively add them in future.)

2021-05-24 perl v5.34.0