Date: Tue, 16 Mar 2010 19:13:32 -1000 (HST)
From: Antonio Querubin <tony@lava.net>
To: Charles Wilson <cygwin@cwilson.fastmail.fm>
cc: cygwin@cygwin.com
Subject: Re: IPv6 help (Re: inetutils, r* commands)
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On Tue, 16 Mar 2010, Charles Wilson wrote:

> That's not really an option.  I'm the inetutils (e.g. r* clients and
> daemons, telnet client and daemon, etc) maintainer for cygwin -- I'm
> trying to create the next official cygwin release of those tools.
>
> I don't think people would be very happy if they only supported IPv6.

I wasn't suggesting that.  AF_INET6 sockets allow IPv4 connectivity. 
Internally, IPv4 addresses are represented as IPv6-mapped addresses.  You 
only convert them back to IPv4 text for display purposes (optional).

Done correctly, any single-listener server app should be convertible to 
handle both IPv6 and IPv4 clients without converting it to a 
multi-listener server.

Try googling for writing protocol-independent code.

Your other challenge though is how to handle the address comparisons. 
But if you force the use of mapped addresses for any IPv4 address, things 
should be a little easier.

Antonio Querubin
808-545-5282 x3003
e-mail/xmpp:  tony@lava.net

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