Want to win a PS4? Go Premium and enter to win our High-Tech Treats giveaway. Enter to Win

x
?
Solved

Invalid ICMP type 69

Posted on 2006-11-03
4
Medium Priority
?
1,331 Views
Last Modified: 2008-01-09
I'm writing a small UDP port scanner that just relys on an ICMP response to detect non-filtered/closed ports.

For some reason my code is returning an ICMP type 69 Code 1 which is not a valid type that I can see. I'd expect a type 3 ( Destination Unreachable ) not an undefined type.

Am I deciphering the ICMP packet I'm receiving wrong? Here is the code I am using:

#!/usr/bin/perl

use IO::Socket;

#
#    Scan UDP ports
#
$|++;
my @ports = ( 53, 514, 15555 );
scan_udp_ports( 'localhost', \@ports );


sub scan_udp_ports {
    my $host = shift;
    my $ports = shift;

    my($closed, $open, $filtered);

    #    Setup ICMP listen
    my $icmp = IO::Socket::INET->new(
                        Proto        =>    'icmp',
                        Blocking    =>    0
                        ) or die("No ICMP listen");

    foreach my $port ( @$ports ) {

        print "Scanning $port\n";

        #    Setup UDP send connection
        $client = IO::Socket::INET->new(
                        PeerPort    =>    $port,
                        PeerAddr    =>    $host,
                        Proto        =>    'udp',
                        Blocking    =>    0
                        ) or die("No server $!");

        #    Send UDP packet
        $client->send( undef );
        sleep( 5 );
        my $icmpbuffer = icmp_recv( $icmp );

        #    Check for response
        my $flags;
        if( $client->recv( $dgram, 10, $flags ) ) {
            print "This udp port $port at host $host responded!\n";
        }
    }
}

sub icmp_recv {
    my $icmp = shift;

    #    Listen for ICMP response
    my $icmpbuffer;
    if( my $icmpr = $icmp->recv( $icmpbuffer, 1024, 0 ) ) {
        print "ICMP Type: " . unpack("%8C", $icmpbuffer) . "\n";
        print "ICMP Code: " . unpack("%8c", substr($icmpbuffer, 9)) . "\n";
        print "ICMP Checksum: " . unpack("%8c", substr($icmpbuffer, 33)) . "\n";
    }
    return $icmpbuffer;
}

0
Comment
Question by:rivusglobal
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
  • 2
4 Comments
 
LVL 16

Expert Comment

by:manav_mathur
ID: 17868839
Since you have already recieved the data in $icmp->recv inside icmp_recv(), why are you again doing $client_recv in scan_udp_ports.

AFAIK, you should set the listening socket ($icmp) in blocking mode; and just test the value of $icmpbuffer to see if data has  arrived....
0
 
LVL 10

Author Comment

by:rivusglobal
ID: 17869069
I'm doing the $client->recv just in case any data actually gets returned over the UDP port, which would be a confirmation of the port being open.

In blocking mode, if there is no ICMP response ( ie. filtered port ) then the script would never receive a response.
0
 
LVL 16

Accepted Solution

by:
manav_mathur earned 2000 total points
ID: 17869145
0
 
LVL 10

Author Comment

by:rivusglobal
ID: 17870121
My unpacking routine wasn't working at all.  After looking at Net::Ping I understand that the actual start of the ICMP type in the returned packet starts 20 bytes into the packet.  This line of code returns the proper ICMP Type and SubCode.

my($fromtype, $fromsubcode) = unpack("C2", substr($icmpbuffer, 20, 2) );

Thanks for pointing me in the right direction manav_mathur.
0

Featured Post

Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

There are many situations when we need to display the data in sorted order. For example: Student details by name or by rank or by total marks etc. If you are working on data driven based projects then you will use sorting techniques very frequently.…
In the distant past (last year) I hacked together a little toy that would allow a couple of Manager types to query, preview, and extract data from a number of MongoDB instances, to their tool of choice: Excel (http://dilbert.com/strips/comic/2007-08…
Explain concepts important to validation of email addresses with regular expressions. Applies to most languages/tools that uses regular expressions. Consider email address RFCs: Look at HTML5 form input element (with type=email) regex pattern: T…
Six Sigma Control Plans

650 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question