168 lines
4.4 KiB
Perl
168 lines
4.4 KiB
Perl
package Net::netent;
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use strict;
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BEGIN {
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use Exporter ();
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use vars qw(@EXPORT @EXPORT_OK %EXPORT_TAGS);
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@EXPORT = qw(getnetbyname getnetbyaddr getnet);
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@EXPORT_OK = qw(
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$n_name @n_aliases
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$n_addrtype $n_net
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);
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%EXPORT_TAGS = ( FIELDS => [ @EXPORT_OK, @EXPORT ] );
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}
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use vars @EXPORT_OK;
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# Class::Struct forbids use of @ISA
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sub import { goto &Exporter::import }
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use Class::Struct qw(struct);
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struct 'Net::netent' => [
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name => '$',
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aliases => '@',
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addrtype => '$',
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net => '$',
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];
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sub populate (@) {
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return unless @_;
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my $nob = new();
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$n_name = $nob->[0] = $_[0];
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@n_aliases = @{ $nob->[1] } = split ' ', $_[1];
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$n_addrtype = $nob->[2] = $_[2];
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$n_net = $nob->[3] = $_[3];
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return $nob;
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}
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sub getnetbyname ($) { populate(CORE::getnetbyname(shift)) }
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sub getnetbyaddr ($;$) {
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my ($net, $addrtype);
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$net = shift;
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require Socket if @_;
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$addrtype = @_ ? shift : Socket::AF_INET();
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populate(CORE::getnetbyaddr($net, $addrtype))
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}
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sub getnet($) {
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if ($_[0] =~ /^\d+(?:\.\d+(?:\.\d+(?:\.\d+)?)?)?$/) {
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require Socket;
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&getnetbyaddr(Socket::inet_aton(shift));
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} else {
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&getnetbyname;
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}
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}
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1;
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__END__
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=head1 NAME
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Net::netent - by-name interface to Perl's built-in getnet*() functions
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=head1 SYNOPSIS
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use Net::netent qw(:FIELDS);
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getnetbyname("loopback") or die "bad net";
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printf "%s is %08X\n", $n_name, $n_net;
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use Net::netent;
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$n = getnetbyname("loopback") or die "bad net";
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{ # there's gotta be a better way, eh?
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@bytes = unpack("C4", pack("N", $n->net));
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shift @bytes while @bytes && $bytes[0] == 0;
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}
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printf "%s is %08X [%d.%d.%d.%d]\n", $n->name, $n->net, @bytes;
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=head1 DESCRIPTION
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This module's default exports override the core getnetbyname() and
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getnetbyaddr() functions, replacing them with versions that return
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"Net::netent" objects. This object has methods that return the similarly
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named structure field name from the C's netent structure from F<netdb.h>;
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namely name, aliases, addrtype, and net. The aliases
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method returns an array reference, the rest scalars.
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You may also import all the structure fields directly into your namespace
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as regular variables using the :FIELDS import tag. (Note that this still
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overrides your core functions.) Access these fields as variables named
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with a preceding C<n_>. Thus, C<$net_obj-E<gt>name()> corresponds to
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$n_name if you import the fields. Array references are available as
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regular array variables, so for example C<@{ $net_obj-E<gt>aliases()
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}> would be simply @n_aliases.
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The getnet() function is a simple front-end that forwards a numeric
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argument to getnetbyaddr(), and the rest
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to getnetbyname().
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To access this functionality without the core overrides,
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pass the C<use> an empty import list, and then access
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function functions with their full qualified names.
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On the other hand, the built-ins are still available
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via the C<CORE::> pseudo-package.
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=head1 EXAMPLES
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The getnet() functions do this in the Perl core:
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sv_setiv(sv, (I32)nent->n_net);
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The gethost() functions do this in the Perl core:
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sv_setpvn(sv, hent->h_addr, len);
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That means that the address comes back in binary for the
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host functions, and as a regular perl integer for the net ones.
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This seems a bug, but here's how to deal with it:
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use strict;
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use Socket;
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use Net::netent;
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@ARGV = ('loopback') unless @ARGV;
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my($n, $net);
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for $net ( @ARGV ) {
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unless ($n = getnetbyname($net)) {
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warn "$0: no such net: $net\n";
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next;
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}
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printf "\n%s is %s%s\n",
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$net,
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lc($n->name) eq lc($net) ? "" : "*really* ",
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$n->name;
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print "\taliases are ", join(", ", @{$n->aliases}), "\n"
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if @{$n->aliases};
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# this is stupid; first, why is this not in binary?
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# second, why am i going through these convolutions
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# to make it looks right
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{
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my @a = unpack("C4", pack("N", $n->net));
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shift @a while @a && $a[0] == 0;
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printf "\taddr is %s [%d.%d.%d.%d]\n", $n->net, @a;
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}
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if ($n = getnetbyaddr($n->net)) {
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if (lc($n->name) ne lc($net)) {
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printf "\tThat addr reverses to net %s!\n", $n->name;
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$net = $n->name;
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redo;
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}
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}
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}
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=head1 NOTE
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While this class is currently implemented using the Class::Struct
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module to build a struct-like class, you shouldn't rely upon this.
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=head1 AUTHOR
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Tom Christiansen
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