Why IO::Socket::INET prohibit to bind dynamic port on INADDR_ANY? [rt.cpan.org #91231]

[toddr]

Migrated from rt.cpan.org#91231 (status was 'new')

Requestors:

• n-a@u01.gate01.com

From n-a@u01.gate01.com on 2013-12-07 02:19:52:

Hi all,

I want to listen on dynamically  selected port using IO::Socket::INET.
When I specify LocalAddr to '127.0.0.1' or so, it works.
However it doesn't work for  '0.0.0.0'.

The code in IO/Socket/INET.pm seems intentionally prohibit this.
I'm just curious to know the reason.

N.A.





--- works well --
use IO::Socket;
my $sock = IO::Socket::INET->new( Proto => 'udp', LocalPort => 0,
LocalAddr => '127.0.0.1' );
say $sock->sockport();
------



--- doesn't work --
use IO::Socket;
my $sock = IO::Socket::INET->new( Proto => 'udp', LocalPort => 0,
LocalAddr => '0.0.0.0' );
say $sock->sockport();
------


--- IO/Socket/INET.pm  line 202  --
	if($lport || ($laddr ne INADDR_ANY) || exists $arg->{Listen}) {
	    $sock->bind($lport || 0, $laddr) or
		    return _error($sock, $!, "$!");
	}
-------

[richardleach]

This does seem like a bug to me.

1. The ($laddr ne INADDR_ANY) might exist because of the logic flow in sub configure. It first does this:

    $laddr = defined $laddr ? inet_aton($laddr)
                            : INADDR_ANY;

2. It uses $laddr in a check:

    return _error($sock, $EINVAL, "Bad hostname '",$arg->{LocalAddr},"'")
        unless(defined $laddr);

3. Then does the check to see if it should bind():

	if($lport || ($laddr ne INADDR_ANY) || exists $arg->{Listen}) {
	    $sock->bind($lport || 0, $laddr) or
		    return _error($sock, $!, "$!");
	}

4. Then if exists($arg->{PeerAddr}) is true, it will try to make an outgoing connect() to a remote socket.

The ($laddr ne INADDR_ANY) check seems to be there to stop the module from doing both a bind() and a connect() call, when only a connect() is appropriate.

Changes along these lines might work:

• Combine 1 & 2 into:

    if (defined $laddr) {
        $laddr = inet_aton($laddr);
        return _error($sock, $EINVAL, "Bad hostname '",$arg->{LocalAddr},"'")
            unless(defined $laddr);
    }

• Change 3. to:

	if($lport || $laddr || exists $arg->{Listen}) {
            $laddr = INADDR_ANY unless ($laddr);
	    $sock->bind($lport || 0, $laddr) or
		    return _error($sock, $!, "$!");
	}

All that said:

• IO::Socket::INET will do what the OP wants if the Listen argument is also passed to the constructor.
• IO::Socket::IP is preferred nowadays and seems to do what the OP wants out of the box:

use v5.40;
use IO::Socket::IP;
my $sock = IO::Socket::IP->new( Proto => 'udp', LocalPort => 0, LocalAddr => '0.0.0.0' );
say $sock->sockhost();
say $sock->sockport();

outputs:

0.0.0.0
52246

So is this a wontfix?