# Net::Domain.pm
#
# Copyright (c) 1995-1998 Graham Barr <[email protected]>. All rights reserved.
# This program is free software; you can redistribute it and/or
# modify it under the same terms as Perl itself.

package Net::Domain;

require Exporter;

use Carp;
use strict;
use vars qw($VERSION @ISA @EXPORT_OK);
use Net::Config;

@ISA = qw(Exporter);
@EXPORT_OK = qw(hostname hostdomain hostfqdn domainname);

$VERSION = "2.20";

my ($host, $domain, $fqdn) = (undef, undef, undef);

# Try every conceivable way to get hostname.


sub _hostname {

# we already know it
return $host
if (defined $host);

if ($^O eq 'MSWin32') {
require Socket;
my ($name, $alias, $type, $len, @addr) = gethostbyname($ENV{'COMPUTERNAME'} || 'localhost');
while (@addr) {
my $a = shift(@addr);
$host = gethostbyaddr($a, Socket::AF_INET());
last if defined $host;
}
if (defined($host) && index($host, '.') > 0) {
$fqdn = $host;
($host, $domain) = $fqdn =~ /^([^\.]+)\.(.*)$/;
}
return $host;
}
elsif ($^O eq 'MacOS') {
chomp($host = `hostname`);
}
elsif ($^O eq 'VMS') { ## multiple varieties of net s/w makes this hard
$host = $ENV{'UCX$INET_HOST'} if defined($ENV{'UCX$INET_HOST'});
$host = $ENV{'MULTINET_HOST_NAME'} if defined($ENV{'MULTINET_HOST_NAME'});
if (index($host, '.') > 0) {
$fqdn = $host;
($host, $domain) = $fqdn =~ /^([^\.]+)\.(.*)$/;
}
return $host;
}
else {
local $SIG{'__DIE__'};

# syscall is preferred since it avoids tainting problems
eval {
my $tmp = "\0" x 256; ## preload scalar
eval {
package main;
require "syscall.ph";
defined(&main::SYS_gethostname);
}
|| eval {
package main;
require "sys/syscall.ph";
defined(&main::SYS_gethostname);
}
and $host =
(syscall(&main::SYS_gethostname, $tmp, 256) == 0)
? $tmp
: undef;
}

# POSIX
|| eval {
require POSIX;
$host = (POSIX::uname())[1];
}

# trusty old hostname command
|| eval {
chop($host = `(hostname) 2>/dev/null`); # BSD'ish
}

# sysV/POSIX uname command (may truncate)
|| eval {
chop($host = `uname -n 2>/dev/null`); ## SYSV'ish && POSIX'ish
}

# Apollo pre-SR10
|| eval { $host = (split(/[:\. ]/, `/com/host`, 6))[0]; }

|| eval { $host = ""; };
}

# remove garbage
$host =~ s/[\0\r\n]+//go;
$host =~ s/(\A\.+|\.+\Z)//go;
$host =~ s/\.\.+/\./go;

$host;
}


sub _hostdomain {

# we already know it
return $domain
if (defined $domain);

local $SIG{'__DIE__'};

return $domain = $NetConfig{'inet_domain'}
if defined $NetConfig{'inet_domain'};

# try looking in /etc/resolv.conf
# putting this here and assuming that it is correct, eliminates
# calls to gethostbyname, and therefore DNS lookups. This helps
# those on dialup systems.

local *RES;
local ($_);

if (open(RES, "/etc/resolv.conf")) {
while (<RES>) {
$domain = $1
if (/\A\s*(?:domain|search)\s+(\S+)/);
}
close(RES);

return $domain
if (defined $domain);
}

# just try hostname and system calls

my $host = _hostname();
my (@hosts);

@hosts = ($host, "localhost");

unless (defined($host) && $host =~ /\./) {
my $dom = undef;
eval {
my $tmp = "\0" x 256; ## preload scalar
eval {
package main;
require "syscall.ph";
}
|| eval {
package main;
require "sys/syscall.ph";
}
and $dom =
(syscall(&main::SYS_getdomainname, $tmp, 256) == 0)
? $tmp
: undef;
};

if ($^O eq 'VMS') {
$dom ||= $ENV{'TCPIP$INET_DOMAIN'}
|| $ENV{'UCX$INET_DOMAIN'};
}

chop($dom = `domainname 2>/dev/null`)
unless (defined $dom || $^O =~ /^(?:cygwin|MSWin32)/);

if (defined $dom) {
my @h = ();
$dom =~ s/^\.+//;
while (length($dom)) {
push(@h, "$host.$dom");
$dom =~ s/^[^.]+.+// or last;
}
unshift(@hosts, @h);
}
}

# Attempt to locate FQDN

foreach (grep { defined $_ } @hosts) {
my @info = gethostbyname($_);

next unless @info;

# look at real name & aliases
my $site;
foreach $site ($info[0], split(/ /, $info[1])) {
if (rindex($site, ".") > 0) {

# Extract domain from FQDN

($domain = $site) =~ s/\A[^\.]+\.//;
return $domain;
}
}
}

# Look for environment variable

$domain ||= $ENV{LOCALDOMAIN} || $ENV{DOMAIN};

if (defined $domain) {
$domain =~ s/[\r\n\0]+//g;
$domain =~ s/(\A\.+|\.+\Z)//g;
$domain =~ s/\.\.+/\./g;
}

$domain;
}


sub domainname {

return $fqdn
if (defined $fqdn);

_hostname();
_hostdomain();

# Assumption: If the host name does not contain a period
# and the domain name does, then assume that they are correct
# this helps to eliminate calls to gethostbyname, and therefore
# eleminate DNS lookups

return $fqdn = $host . "." . $domain
if (defined $host
and defined $domain
and $host !~ /\./
and $domain =~ /\./);

# For hosts that have no name, just an IP address
return $fqdn = $host if defined $host and $host =~ /^\d+(\.\d+){3}$/;

my @host = defined $host ? split(/\./, $host) : ('localhost');
my @domain = defined $domain ? split(/\./, $domain) : ();
my @fqdn = ();

# Determine from @host & @domain the FQDN

my @d = @domain;

LOOP:
while (1) {
my @h = @host;
while (@h) {
my $tmp = join(".", @h, @d);
if ((gethostbyname($tmp))[0]) {
@fqdn = (@h, @d);
$fqdn = $tmp;
last LOOP;
}
pop @h;
}
last unless shift @d;
}

if (@fqdn) {
$host = shift @fqdn;
until ((gethostbyname($host))[0]) {
$host .= "." . shift @fqdn;
}
$domain = join(".", @fqdn);
}
else {
undef $host;
undef $domain;
undef $fqdn;
}

$fqdn;
}


sub hostfqdn { domainname() }


sub hostname {
domainname()
unless (defined $host);
return $host;
}


sub hostdomain {
domainname()
unless (defined $domain);
return $domain;
}

1; # Keep require happy

__END__

=head1 NAME

Net::Domain - Attempt to evaluate the current host's internet name and domain

=head1 SYNOPSIS

use Net::Domain qw(hostname hostfqdn hostdomain domainname);

=head1 DESCRIPTION

Using various methods B<attempt> to find the Fully Qualified Domain Name (FQDN)
of the current host. From this determine the host-name and the host-domain.

Each of the functions will return I<undef> if the FQDN cannot be determined.

=over 4

=item hostfqdn ()

Identify and return the FQDN of the current host.

=item domainname ()

An alias for hostfqdn ().

=item hostname ()

Returns the smallest part of the FQDN which can be used to identify the host.

=item hostdomain ()

Returns the remainder of the FQDN after the I<hostname> has been removed.

=back

=head1 AUTHOR

Graham Barr <[email protected]>.
Adapted from Sys::Hostname by David Sundstrom <[email protected]>

=head1 COPYRIGHT

Copyright (c) 1995-1998 Graham Barr. All rights reserved.
This program is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.

=cut