On Tue, Sep 15, 2009 at 08:12:03AM +0200, Bas Wijnen wrote:
> On Tue, Sep 15, 2009 at 07:51:00AM +0200, Roland Clobus wrote:
> > On Sat, 2009-09-12 at 15:57 +0200, Bas Wijnen wrote:
> > > I'm a bit confused: this is a Debian bug, so the problem presumably
> > > exists on Debian systems.  This may be different on GNU/kFreeBSD, but
> > > the reporter is using GNU/Linux, like the system I'm testing on.

> > > Anyway, I'm attaching the patch.

> > That patch does not work as advertised. I get the error, and the result
> > (according to netstat) is that the server only listens on IPv4.

> > Somewhere when I upgraded to kernel 2.6.30 Pioneers broke, so I assume
> > that the automatic IPv6<->IPv4 bridge was removed.

> In that case, the bug may not actually be in Pioneers.  At least it
> explains my confusion: I tested it on a stable system, with a 2.6.26
> kernel.

> I don't see how this can be fixed, if the approach of the patch to
> listen twice doesn't work.  In the ipv6(7) man page, it says:

>       IPv4 connections can be handled with the v6 API by using the
>       v4-mapped-on-v6  address type; thus a program only needs only to
>       support this API type to support both protocols.  This is
>       handled transparently by  the address handling functions in
>       libc.

> The reverse does not seem to be the case, however.  So the problem is
> that the IPv4 address is returned first, it is listened on, then the
> IPv6 address is returned, and the address is already in use.

> A solution might be to do the listening in two rounds, first ignoring
> all IPv4 addresses and after that using only them (and not warning about
> address already in use failures there).  While this works, I consider it
> a kernel bug if it really is so hard to do it right.

> Steve, do you know more about this?

Well, I don't think there's any kernel bug here, because all the other
IPv6-aware network services I have are listening just fine on both types of
addresses.  I'm meaning to dig into this, but won't really have time to do
so until the weekend.

-- 
Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
Ubuntu Developer                                    http://www.debian.org/
slanga...@ubuntu.com                                     vor...@debian.org

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