Mail::SpamAssassin::DnsResolver - DNS resolution engine


This is a DNS resolution engine for SpamAssassin, implemented in order to reduce file descriptor usage by Net::DNS and avoid a response collision bug in that module.


Load the Net::DNS::Resolver object. Returns 0 if Net::DNS cannot be used, 1 if it is available.

$resolver = $res->get_resolver()
Return the Net::DNS::Resolver object.

Wrapper for Net::DNS::Reslolver->nameservers to get or set list of nameservers

Re-connect to the first nameserver listed in /etc/resolv.conf or similar platform-dependent source, as provided by Net::DNS.

Return the IO::Socket::INET object used to communicate with the nameserver.

$packet = new_dns_packet ($host, $type, $class)
A wrapper for Net::DNS::Packet::new() which traps a die thrown by it.

To use this, change calls to Net::DNS::Resolver::bgsend from:

    $res->bgsend($hostname, $type);


    $res->bgsend(Mail::SpamAssassin::DnsResolver::new_dns_packet($hostname, $type, $class));

$id = $res->bgsend($host, $type, $class, $cb)
Quite similar to Net::DNS::Resolver::bgsend, except that when a response packet eventually arrives, and poll_responses is called, the callback sub reference $cb will be called.

Note that $type and $class may be undef, in which case they will default to A and IN, respectively.

The callback sub will be called with two arguments -- the packet that was delivered and an id string that fingerprints the query packet and the expected reply. It is expected that a closure callback be used, like so:

  my $id = $self->{resolver}->bgsend($host, $type, undef, sub {
        my $reply = shift;
        my $reply_id = shift;
        $self->got_a_reply ($reply, $reply_id);

The callback can ignore the reply as an invalid packet sent to the listening port if the reply id does not match the return value from bgsend.

$nfound = $res->poll_responses()
See if there are any bgsend response packets ready, and return the number of such packets delivered to their callbacks.

Call this to release pending requests from memory when aborting backgrounded requests

$packet = $res->send($name, $type, $class)
Emulates Net::DNS::Resolver::send().

Reset socket when done with it.

Clean up for destruction.