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   1  package Net::netent;
   2  use strict;
   3  
   4  use 5.006_001;
   5  our $VERSION = '1.00';
   6  our(@EXPORT, @EXPORT_OK, %EXPORT_TAGS);
   7  BEGIN { 
   8      use Exporter   ();
   9      @EXPORT      = qw(getnetbyname getnetbyaddr getnet);
  10      @EXPORT_OK   = qw(
  11              $n_name            @n_aliases
  12              $n_addrtype     $n_net
  13             );
  14      %EXPORT_TAGS = ( FIELDS => [ @EXPORT_OK, @EXPORT ] );
  15  }
  16  use vars      @EXPORT_OK;
  17  
  18  # Class::Struct forbids use of @ISA
  19  sub import { goto &Exporter::import }
  20  
  21  use Class::Struct qw(struct);
  22  struct 'Net::netent' => [
  23     name        => '$',
  24     aliases    => '@',
  25     addrtype    => '$',
  26     net        => '$',
  27  ];
  28  
  29  sub populate (@) {
  30      return unless @_;
  31      my $nob = new();
  32      $n_name      =    $nob->[0]              = $_[0];
  33      @n_aliases     = @{ $nob->[1] } = split ' ', $_[1];
  34      $n_addrtype  =    $nob->[2]          = $_[2];
  35      $n_net     =    $nob->[3]          = $_[3];
  36      return $nob;
  37  } 
  38  
  39  sub getnetbyname ($)  { populate(CORE::getnetbyname(shift)) } 
  40  
  41  sub getnetbyaddr ($;$) { 
  42      my ($net, $addrtype);
  43      $net = shift;
  44      require Socket if @_;
  45      $addrtype = @_ ? shift : Socket::AF_INET();
  46      populate(CORE::getnetbyaddr($net, $addrtype)) 
  47  } 
  48  
  49  sub getnet($) {
  50      if ($_[0] =~ /^\d+(?:\.\d+(?:\.\d+(?:\.\d+)?)?)?$/) {
  51      require Socket;
  52      &getnetbyaddr(Socket::inet_aton(shift));
  53      } else {
  54      &getnetbyname;
  55      } 
  56  } 
  57  
  58  1;
  59  __END__
  60  
  61  =head1 NAME
  62  
  63  Net::netent - by-name interface to Perl's built-in getnet*() functions
  64  
  65  =head1 SYNOPSIS
  66  
  67   use Net::netent qw(:FIELDS);
  68   getnetbyname("loopback")         or die "bad net";
  69   printf "%s is %08X\n", $n_name, $n_net;
  70  
  71   use Net::netent;
  72  
  73   $n = getnetbyname("loopback")         or die "bad net";
  74   { # there's gotta be a better way, eh?
  75       @bytes = unpack("C4", pack("N", $n->net));
  76       shift @bytes while @bytes && $bytes[0] == 0;
  77   }
  78   printf "%s is %08X [%d.%d.%d.%d]\n", $n->name, $n->net, @bytes;
  79  
  80  =head1 DESCRIPTION
  81  
  82  This module's default exports override the core getnetbyname() and
  83  getnetbyaddr() functions, replacing them with versions that return
  84  "Net::netent" objects.  This object has methods that return the similarly
  85  named structure field name from the C's netent structure from F<netdb.h>;
  86  namely name, aliases, addrtype, and net.  The aliases 
  87  method returns an array reference, the rest scalars.  
  88  
  89  You may also import all the structure fields directly into your namespace
  90  as regular variables using the :FIELDS import tag.  (Note that this still
  91  overrides your core functions.)  Access these fields as variables named
  92  with a preceding C<n_>.  Thus, C<$net_obj-E<gt>name()> corresponds to
  93  $n_name if you import the fields.  Array references are available as
  94  regular array variables, so for example C<@{ $net_obj-E<gt>aliases()
  95  }> would be simply @n_aliases.
  96  
  97  The getnet() function is a simple front-end that forwards a numeric
  98  argument to getnetbyaddr(), and the rest
  99  to getnetbyname().
 100  
 101  To access this functionality without the core overrides,
 102  pass the C<use> an empty import list, and then access
 103  function functions with their full qualified names.
 104  On the other hand, the built-ins are still available
 105  via the C<CORE::> pseudo-package.
 106  
 107  =head1 EXAMPLES
 108  
 109  The getnet() functions do this in the Perl core:
 110  
 111      sv_setiv(sv, (I32)nent->n_net);
 112  
 113  The gethost() functions do this in the Perl core:
 114  
 115      sv_setpvn(sv, hent->h_addr, len);
 116  
 117  That means that the address comes back in binary for the
 118  host functions, and as a regular perl integer for the net ones.
 119  This seems a bug, but here's how to deal with it:
 120  
 121   use strict;
 122   use Socket;
 123   use Net::netent;
 124  
 125   @ARGV = ('loopback') unless @ARGV;
 126  
 127   my($n, $net);
 128  
 129   for $net ( @ARGV ) {
 130  
 131       unless ($n = getnetbyname($net)) {
 132       warn "$0: no such net: $net\n";
 133       next;
 134       }
 135  
 136       printf "\n%s is %s%s\n", 
 137           $net, 
 138           lc($n->name) eq lc($net) ? "" : "*really* ",
 139           $n->name;
 140  
 141       print "\taliases are ", join(", ", @{$n->aliases}), "\n"
 142           if @{$n->aliases};     
 143  
 144       # this is stupid; first, why is this not in binary?
 145       # second, why am i going through these convolutions
 146       # to make it looks right
 147       {
 148       my @a = unpack("C4", pack("N", $n->net));
 149       shift @a while @a && $a[0] == 0;
 150       printf "\taddr is %s [%d.%d.%d.%d]\n", $n->net, @a;
 151       }
 152  
 153       if ($n = getnetbyaddr($n->net)) {
 154       if (lc($n->name) ne lc($net)) {
 155           printf "\tThat addr reverses to net %s!\n", $n->name;
 156           $net = $n->name;
 157           redo;
 158       } 
 159       }
 160   }
 161  
 162  =head1 NOTE
 163  
 164  While this class is currently implemented using the Class::Struct
 165  module to build a struct-like class, you shouldn't rely upon this.
 166  
 167  =head1 AUTHOR
 168  
 169  Tom Christiansen