jantelar has asked for the wisdom of the Perl Monks concerning the following question:

I'm trying to scan a bunch of networks with Nmap::Scanner, and it usually works pretty nice. From time to time though I get this error:

<nmap-error>
  <pid="22631"/>
  <cmdline="'/usr/bin/nmap' -v -v -v -v -sP 10.8.179.48/28 -oX -"/>
  <nmap-err>RTTVAR has grown to over 2.3 seconds, decreasing to 2.0
</nmap-msg>
</nmap-error>

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I suspect this is related to the fact that some networks are based on GSM/EDGE, ie very sloooow. The problem is that the scanner breaks the while loop. I want to catch the error, and move on to the next net.

My simplified code:

#!/usr/bin/perl

use warnings;
use strict;
use DBI;
use Nmap::Scanner;

my $sth = $dbh->prepare("Some valid SQL");
$sth->execute();

while(my @r = $sth->fetchrow_array()) {
    print STDERR "Scan network $r[0], mask $r[1]\n";
    my $scanner = new Nmap::Scanner;
    $scanner->max_rtt_timeout(10000);
    $scanner->min_rtt_timeout(1000);
    $scanner->host_timeout(5000);
    $scanner->max_parallelism(8);
    my $results = $scanner->scan("-v -sP $r[0]/$r[1]");
    print STDERR "Scan completed\n";

    my $hsts = $results->get_host_list();
    while(my $host = $hsts->get_next()) {
        # Do stuff for each ...
    }
}

exit 0;

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Any hints on how to solve this is appreciated.

Replies are listed 'Best First'.
Re: Nmap::Scanner breaks my while loop, I think
by choroba (Cardinal) on Feb 13, 2012 at 16:19 UTC
    If calling ->scan calls die inside, you can use eval:
    my $results;
eval { $results = $scanner->scan("-v -sP $r[0]/$r[1]"); 1; } or warn "
+Error catched: $@";

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      I really dont know what ->scan does upon errors. What I have tried is this:

      my $results;
eval{ $results = $scanner->scan("-v -sP $r[0]/$r[1]"); };
print STDERR "Error catched: $@\n" if($@);

      [download]

      But, this does not catch it. The while loop still ends right there.

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        The while loop still ends right there.
        Are you sure? Is not it one line later? You should not call 
        $results->get_host_list();

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        if $results is empty.
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Re: Nmap::Scanner breaks my while loop, I think
by roboticus (Chancellor) on Feb 13, 2012 at 16:14 UTC

    jantelar:

    Breaks the while loop? What do you mean?

    ...roboticus

    When your only tool is a hammer, all problems look like your thumb.

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Re: Nmap::Scanner breaks my while loop, I think
by Khen1950fx (Canon) on Feb 13, 2012 at 16:52 UTC
    Works for me. 
    #!/usr/bin/perl 

use strict;
use Nmap::Scanner;

$| = 1;

my @targets = "209.197.123.153", "216.92.34.251";

my $scanner = new Nmap::Scanner;
$scanner->tcp_syn_scan();
$scanner->debug(1);
$scanner->add_scan_port('1-1024');
$scanner->guess_os();
$scanner->max_rtt_timeout("200ms");
$scanner->add_target("66.39.54.27");
$scanner->max_parallelism(8);
    
my $results = $scanner->scan(@targets);
print $results->as_xml;

my $host_list = $results->get_host_list();
while(my $host = $host_list->get_next()) {
     print "Found host named: ", $host->hostname() . "\n";
}
exit 0;

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