dnsmkptr

早期freebsd实现

#!/usr/bin/perl
#
# $Id: dnsmkptr,v 2.0 90/09/11 11:07:34 hakanson Rel $
#
# Convert DNS master (RFC-1035) file A records to PTR records.
#   Marion Hakanson ([e-mail])
#   Oregon Graduate Institute of Science and Technology
#
# Copyright (c) 1990, Marion Hakanson.
#
# You may distribute under the terms of the GNU General Public License
# as specified in the README file that comes with the dnsparse kit.
#
# Read the master files, and produce PTR records based on the A records
# contained in them.  Note that if multiple names are found mapping to
# a single address, we print out only the first mapping encountered.
#
# This is quite rudimentary, sorts the output by number, and does not
# attempt to split the file by net or subnet number.  Hence it lumps
# multiple domain zones into a single PTR zone file, and thus may be
# less useful than it could be.

do "dnsparse.pl"; die "$@, aborted" if $@;

do dns_init(@ARGV);

open(OFILE, '| sort -n -t. +3 -4 +2 -3 +1 -2 +0 -1')
    || die "Cannot start 'sort', aborted";

# bug -- can we guarantee this goes out first after being sorted?
print OFILE "\$ORIGIN IN-ADDR.ARPA.\n";	# in case we get fed to a nameserver

rr: while ( (@rr = do dns_getrr()) && @rr ) {
    ($domain, $ttl, $class, $type, @data) = @rr;

    next rr if ( $class ne 'IN' || $type ne 'A' );

    # only print out the first one
    next rr if ( defined($addr{$data[0]}) );
    
    $addr{$data[0]} = 1;
    
    $revaddr = join('.',reverse(split(/\./, $data[0])));
    print OFILE "$revaddr\tIN\tPTR\t$domain.\n";
}