Generate empty mmdb files

empty_mmdb.pl

# run 'mcpan MaxMind::DB::Writer::Tree' beforehand

use MaxMind::DB::Writer::Tree;
use Net::Works::Network;

my %types = ();

my $tree = MaxMind::DB::Writer::Tree->new(
    ip_version            => 4,
    record_size           => 24,
    database_type         => 'Empty',
    description           => { en => 'Empty database' },
    map_key_type_callback => sub { $types{ $_[0] } },
);

open my $fh, '>:raw', 'GeoLite2-Empty.mmdb';
$tree->write_tree($fh);

test.sh

mmdblookup \
  --file GeoLite2-Empty.mmdb \
  --ip 0.0.0.0