# Selima Website Content Management System
# RemoHost.pm: The subroutine to DNS reverse-query the domain name of the remote host.

#  Copyright (c) 2003-2018 imacat.
#
#  Licensed under the Apache License, Version 2.0 (the "License");
#  you may not use this file except in compliance with the License.
#  You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
#  Unless required by applicable law or agreed to in writing, software
#  distributed under the License is distributed on an "AS IS" BASIS,
#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#  See the License for the specific language governing permissions and
#  limitations under the License.

# Author: imacat <imacat@mail.imacat.idv.tw>
# First written: 2003-04-07

package Selima::RemoHost;
use 5.008;
use strict;
use warnings;
use base qw(Exporter);
use vars qw(@EXPORT @EXPORT_OK);
BEGIN {
@EXPORT = qw(remote_host);
@EXPORT_OK = @EXPORT;
# Prototype declaration
sub remote_host();
}

use Socket qw(inet_aton AF_INET);

use Selima::DataVars qw(:env);

BEGIN {
if (exists $ENV{"MOD_PERL_API_VERSION"} && $ENV{"MOD_PERL_API_VERSION"} >= 2) {
    require Apache2::Connection;
}
}

use Selima::Cache qw(:remohost);
use Selima::DataVars qw(:env);

# remote_host: Look up the remote host domain name
sub remote_host() {
    local ($_, %_);
    my ($r, $addr);
    
    # Looked-up before
    if (defined $RemoHost_remote) {
        return $RemoHost_remote ne "-"? $RemoHost_remote: undef;
    }
    
    if ($IS_MODPERL) {
        $r = $IS_MP2? Apache2::RequestUtil->request:
            Apache->request;
        $addr = $r->connection->remote_ip;
        $_ = $IS_MP2? $r->connection->get_remote_host:
            $r->get_remote_host;
        return ($RemoHost_remote = $_)
            if defined $_ && $_ ne $addr;
    } else {
        $addr = $ENV{"REMOTE_ADDR"};
        # The server had done the job
        return ($RemoHost_remote = $ENV{"REMOTE_HOST"})
            if  exists $ENV{"REMOTE_HOST"}
                && $ENV{"REMOTE_HOST"} ne $addr;
    }
    
    # Look up now
    $_ = gethostbyaddr inet_aton($addr), AF_INET;
    return ($RemoHost_remote = $_) if defined $_;
    
    # Return not found
    $RemoHost_remote = "-";
    return undef;
}

return 1;