Re: [lwip-devel] Single TCP socket to handle IPv4 and IPv6 traffic

[Sylvain Rochet]

hello,

On Thu, Mar 26, 2015 at 08:18:26PM +0100, address@hidden wrote:
> Rahul Gundecha wrote:
> >Hi all,
> >
> >I need to support IPv6 connections with an existing IPv4 socket
> >based HTTP server. There are two possibilities to accomplish this:
> >1) Have 2 sockets, one for IPv4, other for IPv6.
> >2) Have single socket handling both IPv4 and IPv6. Such support do
> >not seem to be present in lwip at this moment.
> 
> Without digging too deep in your question (sorry, no time right
> now), I want to point out that using the socket API, please do not
> try to do anything what lwIP allows. Try to find out how the API
> standard wants you to do things, do it like that and tell us if lwIP
> doesn't work the standard way. Because if it doesn't and you use it
> in a way it happens to work for you, chances are that we fix lwIP to
> follow the standard which might brake things for you...
> 
> Anyway, IPv6 is far from finished in lwIP, so there might well be
> things not working, yet.
> 
> Given that, does your approach of handling IPv4 and IPv6 work on
> linux, unix or win32? If yes, how do you open the socket?

I guess he is talking about IPv4-mapped IPv6 addresses, it works very 
well in Linux and is actually the default. IPv6-ready software (if they 
want to) only needs to bind&listen to IPv6 and will then accept IPv4 
connection using IPv4-mapped IPv6 addresses.

Sylvain


[1] http://en.wikipedia.org/wiki/IPv6#IPv4-mapped_IPv6_addresses

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