#!/usr/bin/perl

use strict;
use warnings;

use Getopt::Long;
use Socket qw(
   AF_INET
   SOCK_STREAM SOCK_DGRAM SOCK_RAW
   IPPROTO_TCP IPPROTO_UDP IPPROTO_IP
   inet_ntoa unpack_sockaddr_in
);
use Socket::GetAddrInfo qw( getaddrinfo AI_PASSIVE AI_CANONNAME );

# Not sure where we'll find IPv6 things
my $AF_INET6;
BEGIN {
   $AF_INET6 = eval { Socket::AF_INET6() } ||
               eval { require Socket6 and Socket6::AF_INET6() };
   if( defined &Socket::unpack_sockaddr_in6 ) {
      *unpack_sockaddr_in6 = \&Socket::unpack_sockaddr_in6;
      *inet_ntop           = \&Socket::inet_ntop;
   }
   elsif( eval { require Socket6 and defined &Socket6::unpack_sockaddr_in6 } ) {
      *unpack_sockaddr_in6 = \&Socket6::unpack_sockaddr_in6;
      *inet_ntop           = \&Socket6::inet_ntop;
   }
}
use constant CAN_IPv6 => defined &unpack_sockaddr_in6;

sub getfamilybynumber
{
   my ( $family ) = @_;
   return "AF_INET"  if $family == AF_INET;
   return "AF_INET6" if defined $AF_INET6 and $family == $AF_INET6;
   return $family;
}

sub getsocktypebynumber
{
   my ( $socktype ) = @_;
   return "SOCK_STREAM" if $socktype == SOCK_STREAM;
   return "SOCK_DGRAM"  if $socktype == SOCK_DGRAM;
   return "SOCK_RAW"    if $socktype == SOCK_RAW;
   return $socktype;
}

sub getprotocolbynumber
{
   my ( $protocol ) = @_;
   return "IPPROTO_TCP" if $protocol == IPPROTO_TCP;
   return "IPPROTO_UDP" if $protocol == IPPROTO_UDP;
   return "IPPROTO_IP"  if $protocol == IPPROTO_IP;
   return $protocol;
}

sub usage
{
   my ( $exitcode ) = @_;

   my $basename = $0;
   $basename =~ m{/([^/]+?)$} and $basename = $1;

   print STDERR <<"EOF";
Performs a getaddrinfo(3) lookup and prints the returned address structures

Usage:
  $basename [HOST] [SERVICE] [options...]

Options:

  --host, -H HOST       Hostname to resolve
  --service, -S SERVICE Service name or port number to resolve

  -4                    Restrict to just AF_INET (IPv4) results
  -6                    Restrict to just AF_INET6 (IPv6) results

  --stream              Restrict to just SOCK_STREAM results
  --dgram               Restrict to just SOCK_DGRAM results

  --proto PROTO         Restrict to just results of the given IP protocol

  --passive             Set the AI_PASSIVE hint; results will used to bind()
                        and listen() rather than connect()

  --canonical           Retrive the canonical name for the requested host

  --help                Display this help and exit

EOF

   exit $exitcode;
}

my $host;
my $service;
my %hints;

GetOptions(
   'host|H=s'    => \$host,
   'service|S=s' => \$service,

   '4' => sub { $hints{family} = AF_INET },
   '6' => sub { defined $AF_INET6 ? $hints{family} = $AF_INET6
                                  : die "Cannot do AF_INET6\n"; },

   'stream|s' => sub { $hints{socktype} = SOCK_STREAM },
   'dgram'    => sub { $hints{socktype} = SOCK_DGRAM },

   'proto=s' => sub {
      my $proto = $_[1];
      unless( $proto =~ m/^\d+$/ ) {
         my $protonum = getprotobyname( $proto );
         defined $protonum or die "No such protocol - $proto\n";
         $proto = $protonum;
      }
      $hints{protocol} = $proto;
   },

   'passive' => sub { $hints{flags} ||= AI_PASSIVE },

   'canonical' => sub { $hints{flags} ||= AI_CANONNAME },

   'help|h' => sub { usage( 0 ) },
) or usage( 1 );

$host    = shift @ARGV if @ARGV and !defined $host;
$service = shift @ARGV if @ARGV and !defined $service;

defined $host or defined $service or
   usage( 1 );

$host    ||= "";
$service ||= "0";

my ( $err, @res ) = getaddrinfo( $host, $service, \%hints );

die "Cannot getaddrinfo() - $err\n" if $err;

printf "Resolved host '%s', service '%s'\n", $host, $service;

if( $res[0]->{canonname} ) {
   printf "  Canonical name '%s'\n", $res[0]->{canonname};
}

print "\n";

foreach my $res ( @res ) {
   my $address_string;
   if( $res->{family} == AF_INET ) {
      my ( $port, $host ) = unpack_sockaddr_in $res->{addr};
      $address_string = sprintf "%s:%d", inet_ntoa( $host ), $port;
   }
   elsif( CAN_IPv6 and $res->{family} == $AF_INET6 ) {
      my ( $port, $host ) = unpack_sockaddr_in6( $res->{addr} );
      $address_string = sprintf "[%s]:%d", inet_ntop( $res->{family}, $host ), $port;
   }
   else {
      $address_string = sprintf '{family=%d,addr=%v02x}', $res->{family}, $res->{addr};
   }

   printf "socket(%-8s, %-11s, %-11s) + '%s'\n",
      getfamilybynumber($res->{family}),
      getsocktypebynumber($res->{socktype}),
      getprotocolbynumber($res->{protocol}),
      $address_string;
}

__END__

=head1 NAME

C<getaddrinfo> - command-line tool to C<getaddrinfo(3)> resolver

=head1 SYNOPSIS

B<getaddrinfo> [I<options...>] I<host> I<service>

=head1 DESCRIPTION

This tool provides a convenient command-line wrapper around the
C<getaddrinfo(3)> resolver function. It will perform a single lookup and print
the returned results in a human-readable form. This is mainly useful when
debugging address resolution problems, because it allows inspection of the
C<getaddrinfo(3)> behaviour itself, outside of any real program that is trying
to use it.

=head1 OPTIONS

=over 8

=item --host, -H HOST

Hostname to resolve. If not supplied, will use the first positional argument

=item --service, -S SERVICE

Service name or port number to resolve. If not supplied, will use the second
positional argument.

=item -4

Restrict to just C<AF_INET> (IPv4) results

=item -6

Restrict to just C<AF_INET6> (IPv6) results

=item --stream

Restrict to just C<SOCK_STREAM> results

=item --dgram 

Restrict to just C<SOCK_DGRAM> results

=item --proto PROTO

Restrict to just results of the given IP protocol

=item --passive

Set the C<AI_PASSIVE> hint; results will used to bind() and listen() rather
than connect()

=item --canonical

Retrive the canonical name for the requested host

=item --help

Display a help summary and exit

=back

=head1 OUTPUT FORMAT

Each line of output will be given in a form that indicates the four result
fields of C<ai_family>, C<ai_socktype>, C<ai_protocol> and C<ai_addr>. The
first three are printed in the form of a C<socket(2)> call, either
symbolically or numerically, and the latter is printed as a plain string
following it. For example

 socket(AF_INET , SOCK_STREAM, IPPROTO_TCP) + '127.0.0.1:80'

=head1 AUTHOR

Paul Evans <leonerd@leonerd.org.uk>