Re: [libmicrohttpd] How is MHD_USE_IPv6 supposed to work?

[Christian Grothoff]

On 12/13/2011 07:26 PM, Sven Geggus wrote:
> Hello,
>
> to support dual stack I just changed my code from:
>
> MHD_start_daemon(MHD_NO,...
> to
> MHD_start_daemon(MHD_USE_IPv6,...
>
> Unfortunately the daemon seems to be ipv6 _only_ now.
>
> How ist this supposed to work?
>
>  From generic socket-programming I usually assume AF_INET6 on to
> serverside to be both IPv4 and IPv6. Is this different as far as
> libmicrohttpd is concerned?

Yes, assuming an IPv6-socket is for both v4 and v6 is considered bad 
style and will NOT work on all OSes (and on Linux it'll only work if 
your kernel uses a particular, outdated configuration).

The correct way to get dual-stack is to call MHD_start_daemon twice, 
once for IPv4 and once for IPv6.

If you want to insist on one listen-socket for both v4 and v6, you can 
still force that by doing the bind/listen manually yourself (with the 
right socket options and appropriate amount of praying) and then give 
that pre-bound listen socket to MHD (MHD_OPTION_LISTEN_SOCKET).  But 
again, this is NOT the recommended or portable approach.

Happy hacking,

Christian