NAME

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

SYNOPSIS

    use Net::DNS::Resolver::Programmable;
    use Net::DNS::RR;
    
    my $resolver = Net::DNS::Resolver::Programmable->new(
        records         => {
            'example.com'     => [
                Net::DNS::RR->new('example.com.     NS  ns.example.org.'),
                Net::DNS::RR->new('example.com.     A   192.168.0.1')
            ],
            'ns.example.org'  => [
                Net::DNS::RR->new('ns.example.org.  A   192.168.1.1')
            ]
        },
        
        resolver_code   => sub {
            my ($domain, $rr_type, $class) = @_;
            ...
            return ($result, $aa, @rrs);
        }
    );

DESCRIPTION

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.

Constructor

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:

records

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 => {
        'example.com'     => [
            Net::DNS::RR->new('example.com.     NS  ns.example.org.'),
            Net::DNS::RR->new('example.com.     A   192.168.0.1')
        ],
        'www.example.com' => [
            Net::DNS::RR->new('www.example.com. A   192.168.0.2')
        ],
        'ns.example.org'  => [
            Net::DNS::RR->new('ns.example.org.  A   192.168.1.1')
        ]
    }

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

resolver_code

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.

defnames

dnsrch

domain

searchlist

debug

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

Instance methods

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.
print
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.

AUTHORS

David Precious (BIGPRESH) "<davidp@preshweb.co.uk>" took on maintainership in July 2017

Original author Julian Mehnle "<julian@mehnle.net>"

ACKNOWLEDGEMENTS

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.)