AnyEvent::DNS blocks on windows when no DNS available

[Cotter, Dan]

Hi,

On windows, AnyEvent::DNS blocks when calling the Net::DNS::Resolver constructor when windows has no network adaptors with DNS.
It seems that localhost is included in the default nameserver list, and the constructor attempts to communicate with localhost if there are otherwise no nameservers.
Due to the default retrans and retry settings, this blocks for a combined 150 seconds on dual stack PC's.

Example (run on windows with no DNS available):

use AnyEvent;
use AnyEvent::DNS;
my $cv = AnyEvent->condvar;
my $tm = AnyEvent->timer(after=>1,interval=>1,cb=>sub{print ".\n"; }); # Never fires
AnyEvent::DNS::a "www.google.de", $cv; # Blocks for 150s
my @addrs = $cv->recv;

A suggested fix is to empty the defaults before the constructor is used to determine name servers:

Net::DNS::Resolver->nameserver4([]);
Net::DNS::Resolver->nameserver6([]);

Though technically this would change behavior for someone running a DNS server at localhost...?

Regards,
Dan






Dan Cotter
Engineering Design & Reliability
Engineering Services
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