| Subject: | Net::DNS Crash in Cygwin with more than 200 threads |
Hi:
I'm developing a class C scanner that looks for active DNS servers. It uses threads to speed up the process. (code attached)
When I create more than 200 threads, Perl dies with a segmentation fault in Cygwin (In linux works fine).
Ive done similar things with perl, but without Net::DNS and never get in this situation.
It's a cygwin problem? It's a perl problem? It's a Net::DNS problem?
Thanks in advance
#!/usr/bin/perl
#
# DNSFINDER.pl v0.2 - DNS Server Scanner (multithread)
#
# by The Dark Raver <darkraver@open-labs.org> (10/12/2005)
#
#
# Scans a range of IP address looking for open DNS servers.
#
# Example:
#
# ./dnsfinder.pl 192.168.0.1-254 -v
#
use strict;
use warnings;
use threads;
use Net::DNS; # Not thread safe in Cygwin with +200 threads :(
my $verbose=0;
my $found=0;
if(!$ARGV[0]) { print "Usage: ./dnsfinder.pl xx.xx.xx.xx[-xx] [-v]\n"; exit; }
my @target=split(/-/, $ARGV[0]);
my $start=$target[0];
my @ip=split(/\./, $start);
my $end=$ip[3];
if($target[1]) { $end=$target[1]; } else { $verbose=1; }
if($end > 255) { $end=255; }
if(defined $ARGV[1] and $ARGV[1] eq "-v") { $verbose=1; }
print "\n-- DNSFINDER by The Dark Raver --\n\n";
#print "IP_START: $ip[0].$ip[1].$ip[2].$ip[3]\n\n";
print "
IP Address Host Name Bind Version Recursive Cache
-------------------------------------------------------------------------------
";
my @iplist;
for(my $i=$ip[3];$i<=$end;$i++) {
push(@iplist, $ip[0].".".$ip[1].".".$ip[2].".".$i);
}
my $child;
my @child_list;
foreach my $iplist (@iplist) {
$child = threads->new(\&scan_host, $iplist, $verbose);
push(@child_list, $child);
sleep(1);
}
#print "P\n"; select(STDOUT);
foreach $child (@child_list) {
my $returned_data = $child->join;
#print "Child thread returned: $returned_data\n";
if($returned_data==1) { $found++; }
}
print "\n-- Found $found Active DNS Servers --\n\n";
exit;
sub scan_host {
my ($ipname, $my_verbose) = @_;
my $ok=0;
my $recursive=0;
my $caching=0;
my $name="";
my $version="";
my $random="www.random.org";
#print "C\n"; select(STDOUT);
format STDOUT =
@<<<<<<<<<<<<<< @<<<<<<<<<<<<<<<<<<<<<<<< @<<<<<<<<<<<<<<<<<<<<<<<<<<< @> @>>>>
$ipname, $name, $version, $recursive, $caching
.
my $res = Net::DNS::Resolver->new();
$res->nameservers($ipname);
#__QUERY1__
my $query = $res->search($ipname);
if($query) {
$ok=1;
foreach my $rr ($query->answer) {
if($rr->type eq "PTR") {
$name=$rr->ptrdname;
#print "PTR: ".$rr->ptrdname."\n";
}
}
} else {
if($my_verbose) { print "QUERY1 ($ipname): ".$res->errorstring."\n"; select(STDOUT); $| = 1; }
if($res->errorstring eq "NOERROR") { $ok=1; $name="(none)"}
}
if($ok) {
#__VERSION.BIND__
$query = $res->search("version.bind", "TXT", "CH");
if($query) {
foreach my $rr ($query->answer) {
if($rr->type eq "TXT") {
$version=$rr->txtdata;
#print "TXT: ".$rr->txtdata."\n";
}
}
} else {
if($my_verbose) { print "QUERY2 ($ipname): ".$res->errorstring."\n"; select(STDOUT); $| = 1; }
if($res->errorstring eq "NOTIMP") { $version="(not_implemented)";}
if($res->errorstring eq "SERVFAIL") { $version="(server_failed)";}
}
#__IS.RECURSIVE__
$query = $res->search($random);
if($query) { $recursive=1; }
else { if($my_verbose) { print "QUERY3 ($ipname): ".$res->errorstring."\n"; select(STDOUT); $| = 1; } }
#__IS.CACHING__
$res->recurse(0);
$query = $res->search($random);
if($query) { $caching=1; }
else { if($my_verbose) { print "QUERY4 ($ipname): ".$res->errorstring."\n"; select(STDOUT); $| = 1; } }
write;
select(STDOUT); $| = 1;
return 1;
}
return 0;
}