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#! /usr/bin/env perl
# Script does an snmp walk through the ports of one or more network
# switch, gathering MAC addresses assigned to each port.
#
# requires snmp running on this machine. Also uses YAML::Tiny perl module
# under debian and derivatives, use the following command to install
# apt-get -y install snmp libyaml-tiny-perl
#
# It then does an snmp walk through the arp table of one or
# more routers to determine IP and DNS entries for the MAC address
#
# Information gathered is stored in persistent storage (a yaml formatted file
# in the same directory), then reloaded at the next start of the program.
# As new entries become available, they are added. A time stamp
# records the last time an entry was "seen"
# Data is stored in the hash %switchports with the following structure
# %switchports =
# {switch} (from $config{'switches'} key)
# {name} (scalar, from snmp)
# {location} (scalar, from snmp)
# {'ports'} (constant key for sub hash)
# {port number} (from snmp)
# {connection} (uniqe id from snmp, basically the MAC)
# {mac} (from snmp walk of switch)
# {ip} (from snmp walk of router)
# {hostname} (from reverse dns query)
# {lastseen} (last time this was active as unix timestamp)
# 20190407 RWR
# converted to use external config file in YAML format
# added the ability to ignore ports on the switches
use strict;
use warnings;
use Data::Dumper; # only used for debugging
use Socket; # for reverse dns entries
use YAML::Tiny; # apt-get libyaml-tiny-perl under debian
use File::Spec; # find location of script so we can put storage in same directory
use File::Basename;
my %config;
# where the script is located
my $scriptDir = dirname( File::Spec->rel2abs( __FILE__ ) );
# put the statefile in there
my $STATEFILE = $scriptDir . '/mapSwitches.yaml';
my $CONFIGFILE = $scriptDir . '/mapSwitches.config.yaml';
# main hash that holds the data we collect
my %switchports;
# some OIDS we need for the program
my $SWITCHPORTMIB = 'iso.3.6.1.2.1.17.4.3.1.2';
my $SWITCHMACMIB = 'iso.3.6.1.2.1.17.4.3.1.1';
my $ROUTERIPMACMIB = 'iso.3.6.1.2.1.4.22.1.2'; #'iso.3.6.1.2.1.3.1.1.2';
my $DEVICENAMEMIB = '1.3.6.1.2.1.1.5';
my $DEVICELOCMIB = '1.3.6.1.2.1.1.6';
sub makeMAC {
my $string = shift;
my @octets = split( '\.', $string );
for ( my $i = 0; $i < @octets; $i++ ) {
$octets[$i] = sprintf( "%02x", $octets[$i] );
}
return join( '', @octets );
}
sub updateValue {
my ( $oldValue, $newValue ) = @_;
$newValue = '' unless defined $newValue;
if ( $newValue ) {
$$oldValue = $newValue unless $newValue eq $$oldValue;
return 1;
}
return 0;
}
sub getOneSNMPValue {
my ( $oid, $community, $ip, $regex ) = @_;
my $line = `snmpwalk -v1 -c $community $ip $oid`;
$line =~ m/$regex/i;
return $1;
}
sub initialize {
my ( $hash, $name, @keys ) = @_;
foreach my $key ( @keys ) {
$hash->{$name}->{$key} = '' unless $hash->{$name}->{$key};
}
}
sub updateIP {
my ( $switchports, $ip, $mac ) = @_;
foreach my $switch ( keys %$switchports ) {
my $thisSwitch = $switchports->{$switch}->{'ports'};
foreach my $port ( keys %$thisSwitch ) {
my $thisPort = $thisSwitch->{$port};
foreach my $connection ( keys %$thisPort ) {
&initialize( $thisPort,$connection,'mac','ip','hostname','lastseen' );
if ( $switchports->{$switch}->{'ports'}->{$port}->{$connection}->{'mac'} eq $mac ) {
my $modified = &updateValue( \$switchports->{$switch}->{'ports'}->{$port}->{$connection}->{'ip'}, $ip );
$modified |= &updateValue( \$switchports->{$switch}->{'ports'}->{$port}->{$connection}->{'hostname'},gethostbyaddr( inet_aton( $ip ), AF_INET ));
$switchports->{$switch}->{'ports'}->{$port}->{$connection}->{'lastseen'} = time() if $modified;
return;
} # if we found it
} # for connection
} # for port
} # for switch
} # updateIP
if ( -e $CONFIGFILE ) {
my $yaml = YAML::Tiny->read( $CONFIGFILE );
%config = %{ $yaml->[0] };
} else {
die "could not locate config file $CONFIGFILE\n";
}
# read the saved state into memory if it exists
if ( -e $STATEFILE ) {
my $yaml = YAML::Tiny->read( $STATEFILE );
%switchports = %{ $yaml->[0] };
}
# first, get all of the MAC/Port assignments from the switches
foreach my $switch ( keys %{$config{'switches'}} ) {
&initialize( \%switchports, $switch, 'name','location' );
&updateValue(
\$switchports{$switch}{'name'},
&getOneSNMPValue( $DEVICENAMEMIB,$config{'switches'}{$switch}{'community'},$switch, '= STRING: "?([^"]*)"?' )
);
&updateValue(
\$switchports{$switch}{'location'},
&getOneSNMPValue( $DEVICELOCMIB,$config{'switches'}{$switch}{'community'},$switch, '= STRING: "?([^"]*)"?' )
);
my $values = `snmpwalk -v1 -c $config{switches}{$switch}{'community'} $switch $SWITCHPORTMIB`;
my @lines = split( "\n", $values );
foreach my $line ( @lines ) {
$line =~ m/$SWITCHPORTMIB\.([0-9.]+)\s=\sINTEGER:\s+(\d+)/;
my $uuid = $1; # this is the ID string of this MAC; normally the MAC itself in decimal form
my $port = $2; # this is the port number
next unless $port; # skip port 0, or any port which has nothing
next if $config{'switches'}{$switch}{'portsToIgnore'} && grep( /^$port$/, @{$config{'switches'}{$switch}{'portsToIgnore'}} );
$switchports{$switch}{'ports'}{$port}{$uuid}{'mac'} = &makeMAC( $1 );
}
}
# die Dumper( \%switchports );
# Now, try to match up the MAC address. Read the ARP table from the router(s)
foreach my $router ( keys %{$config{'routers'}} ) {
my $values = `snmpwalk -v1 -c $config{routers}{$router}{community} $router $ROUTERIPMACMIB`;
my @lines = split( "\n", $values );
foreach my $line ( @lines ) {
$line =~ m/$ROUTERIPMACMIB\.([0-9]+)\.([0-9.]+)\s=\sHex-STRING:\s([0-9a-z ]+)/i;
my $interface = $1;
my $ip = $2;
my $mac = lc $3;
$mac =~ s/ //g;
&updateIP( \%switchports, $ip, $mac );
}
}
#die Dumper( \%switchports );
# save the state file for later, so we can find things which disappear from the network
my $yaml = YAML::Tiny->new( \%switchports );
$yaml->write( $STATEFILE );
#print Dumper( \%switchports );
1;