man Net::NBName (3): NetBIOS Name Service Requests

SYNOPSIS

use Net::NBName;
my $nb = Net::NBName->new;
# a unicast node status request
my $ns = $nb->node_status("10.0.0.1");
if ($ns) {
print $ns->as_string;
}
# a unicast name query request
my $nq = $nb->name_query("10.0.1.80", "SPARK", 0x00);
if ($nq) {
print $nq->as_string;
}
# a broadcast name query request
my $nq = $nb->name_query(undef, "SPARK", 0x00);
if ($nq) {
print $nq->as_string;
}

DESCRIPTION

Net::NBName is a class that allows you to perform simple NetBIOS Name Service Requests in your Perl code. It performs these NetBIOS operations over TCP/IP using Perl's built-in socket support.

I've currently implemented two NBNS requests: the node status request and the name query request.

NetBIOS Node Status Request

This allows you to determine the registered NetBIOS names for a specified remote host.

The decoded response is returned as a "Net::NBName::NodeStatus" object.

    querying 192.168.0.10 for node status...
    SPARK          <20> UNIQUE M-node Registered Active
    SPARK          <00> UNIQUE M-node Registered Active
    PLAYGROUND     <00> GROUP  M-node Registered Active
    PLAYGROUND     <1C> GROUP  M-node Registered Active
    PLAYGROUND     <1B> UNIQUE M-node Registered Active
    PLAYGROUND     <1E> GROUP  M-node Registered Active
    SPARK          <03> UNIQUE M-node Registered Active
    PLAYGROUND     <1D> UNIQUE M-node Registered Active
    ..__MSBROWSE__.<01> GROUP  M-node Registered Active
    MAC Address = 00-1C-2B-3A-49-58

NetBIOS Name Query Request

This allows you to resolve a name to an IP address using NetBIOS Name Resolution. These requests can either be unicast (e.g. if you are querying an NBNS server) or broadcast on the local subnet.

In either case, the decoded response is returned as an "Net::NBName::NameQuery" object.

    querying 192.168.0.10 for playground<00>...
    255.255.255.255 GROUP  B-node
    ttl = 0 (default is 300000)
    RA set, this was an NBNS server
    broadcasting for playground<1C>...
    192.168.0.10    GROUP  B-node
    ttl = 0 (default is 300000)
    RA set, this was an NBNS server
    broadcasting for spark<20>...
    192.168.0.10    UNIQUE H-node
    ttl = 0 (default is 300000)
    RA set, this was an NBNS server

CONSTRUCTOR

$nb = Net::NBName->new: Creates a new "Net::NBName" object. This can be used to perform NetBIOS Name Service requests.

METHODS

$ns = $nb->node_status( $host [, $timeout] )

This will query the host for its node status. The response will be returned as a "Net::NBName::NodeStatus" object.

If no response is received from the host, the method will return undef.

You can also optionally specify the timeout in seconds for the node status request. The timeout defaults to .25 seconds.

$nq = $nb->name_query( $host, $name, $suffix [, $flags [, $timeout] ] )

This will query the host for the specified name. The response will be returned as a "Net::NBName::NameQuery" object.

If $host is undef, then a broadcast name query will be performed; otherwise, a unicast name query will be performed.

Broadcast name queries can sometimes receive multiple responses. Only the first positive response will be decoded and returned as a "Net::NBName::NameQuery" object.

If no response is received or a negative name query response is received, the method will return undef.

You can override the flags in the NetBIOS name request, if you *really* want to. See the notes on Hacking Name Query Flags.

You can also optionally specify the timeout in seconds for the name query request. It defaults to .25 seconds for unicast name queries and 1 second for broadcast name queries.

EXAMPLES

Querying NetBIOS Names

You can use this example to query for a NetBIOS name. If you specify a host, it will perform a unicast query; if you don't specify a host, it will perform a broadcast query. I've used the shorthand of specifying the name as <name>#<suffix> where the suffix should be in hex.

``namequery.pl spark#0''

``namequery.pl spark#20 192.168.0.10''

    use strict;
    use Net::NBName;
    my $nb = Net::NBName->new;
    my $param = shift;
    my $host = shift;
    if ($param =~ /^([\w-]+)\#(\w{1,2})$/) {
        my $name = $1;
        my $suffix = hex $2;
        my $nq;
        if (defined($host) && $host =~ /\d+\.\d+\.\d+\.\d+/) {
            printf "querying %s for %s<%02X>...\n", $host, $name, $suffix;
            $nq = $nb->name_query($host, $name, $suffix);
        } else {
            printf "broadcasting for %s<%02X>...\n", $name, $suffix;
            $nq = $nb->name_query(undef, $name, $suffix);
        }
        if ($nq) {
            print $nq->as_string;
        }
    } else {
        die "expected: <name>#<suffix> [<host>]\n";
    }

Querying Remote Name Table

This example emulates the windows nbtstat -A command. By specifying the ip address of the remote host, you can check its NetBIOS Name Table.

``nodestat.pl 192.168.0.10''

    use Net::NBName;
    my $nb = Net::NBName->new;
    my $host = shift;
    if (defined($host) && $host =~ /\d+\.\d+\.\d+\.\d+/) {
        my $ns = $nb->node_status($host);
        if ($ns) {
            print $ns->as_string;
        } else {
            print "no response\n";
        }
    } else {
        die "expected: <host>\n";
    }

Scanning for NetBIOS hosts

This example can be used to scan for NetBIOS hosts on a subnet. It uses Net::Netmask to parse the subnet parameter and enumerate the hosts in that subnet.

``nodescan.pl 192.168.0.0/24''

    use Net::NBName;
    use Net::Netmask;
    $mask = shift or die "expected: <subnet>\n";
    $nb = Net::NBName->new;
    $subnet = Net::Netmask->new2($mask);
    for $ip ($subnet->enumerate) {
        print "$ip ";
        $ns = $nb->node_status($ip);
        if ($ns) {
            for my $rr ($ns->names) {
                if ($rr->suffix == 0 && $rr->G eq "GROUP") {
                    $domain = $rr->name;
                }
                if ($rr->suffix == 3 && $rr->G eq "UNIQUE") {
                    $user = $rr->name;
                }
                if ($rr->suffix == 0 && $rr->G eq "UNIQUE") {
                    $machine = $rr->name unless $rr->name =~ /^IS~/;
                }
            }
            $mac_address = $ns->mac_address;
            print "$mac_address $domain\\$machine $user";
        }
        print "\n";
    }

NOTES

Microsoft's WINS Server Implementation

When performing name queries, you should note that when Microsoft implemented their NBNS Name Server (Microsoft WINS Server) they mapped group names to the single IP address 255.255.255.255 (the limited broadcast address). In order to support real group names, Microsoft modified WINS to provide support for special groups. These groups appear differently in WINS. For example, the Domain Controllers (0x1C) group appears as ``Domain Name'' instead of ``Group''.

The complete set of WINS mapping types is:

    Unique
    Group
    Domain Name
    Internet group
    Multihomed

Unique and Group map to a single IP address. Domain Name, Internet group, and Multihomed are special groups that can include up to 25 IP addresses.

Hacking Name Query Flags

NetBIOS Name Service Requests have a number of flags associated with them. These are set to sensible defaults by the code when sending node status and name query requests.

However, it is possible to override these settings by calling the name_query method of a "Net::NBName" object with a fourth parameter:

    $nb->name_query( $host, $name, $suffix, $flags );

For a unicast name query, the flags default to 0x0100 which sets the RD (recursion desired) flag. For a broadcast name query, the flags default to 0x0010 which sets the B (broadcast) flag.

Experimentation gave the following results:

If B is set, the remote name table will be used. There will be no response if the queried name is not present.
If B is not set and the host is an NBNS server, the NBNS server will be used before the remote name table and you will get a negative response if the name is not present; if the host is not an NBNS server, you will get no response if the name is not present.