NAME¶

Mail::SpamAssassin::DnsResolver - DNS resolution engine

DESCRIPTION¶

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.

METHODS¶

$res->load_resolver()

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.

$res->configured_nameservers()

Get a list of nameservers as configured by dns_server directives or as provided by Net::DNS, typically from /etc/resolv.conf

$res->available_nameservers()

Get or set a list of currently available nameservers, which is typically a known-to-be-good subset of configured nameservers

$res->connect_sock()

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

$res->get_sock()

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

$packet = new_dns_packet ($domain, $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:

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

to:

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

$id = $res->bgsend($domain, $type, $class, $cb)

Quite similar to "Net::DNS::Resolver::bgsend", except that when a reply 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 three arguments -- the packet that was delivered, and an id string that fingerprints the query packet and the expected reply. The third argument is a timestamp (Unix time, floating point), captured at the time the packet was collected. It is expected that a closure callback be used, like so:

  my $id = $self->{resolver}->bgsend($domain, $type, undef, sub {
        my ($reply, $reply_id, $timestamp) = @_;
        $self->got_a_reply ($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.

$id = $res->bgread()

Similar to "Net::DNS::Resolver::bgread". Reads a DNS packet from a supplied socket, decodes it, and returns a Net::DNS::Packet object if successful. Dies on error.

$nfound = $res->poll_responses()

See if there are any "bgsend" reply packets ready, and return the number of such packets delivered to their callbacks.

$res->bgabort()

Call this to release pending requests from memory, when aborting backgrounded requests, or when the scan is complete. "Mail::SpamAssassin::PerMsgStatus::check" calls this before returning.

$packet = $res->send($name, $type, $class)

Emulates "Net::DNS::Resolver::send()".

This subroutine is a simple synchronous leftover from SpamAssassin version 3.3 and does not participate in packet query caching and callback grouping as implemented by AsyncLoop::bgsend_and_start_lookup(). As such it should be avoided for mainstream usage. Currently used through Mail::SPF::Server by the SPF plugin.

$res->errorstring()

Little more than a stub for callers expecting this from "Net::DNS::Resolver".

If called immediately after a call to $res->send this will return "query timed out" if the $res->send DNS query timed out. Otherwise "unknown error or no error" will be returned.

No other errors are reported.

$res->finish_socket()

Reset socket when done with it.

$res->finish()

Clean up for destruction.