[ntp:questions] ipv6 support on linux - bind problem

Danny Mayer mayer at ntp.isc.org
Mon Apr 9 01:32:15 UTC 2007

Wolfgang S. Rupprecht wrote:
> mayer at ntp.isc.org (Danny Mayer) writes:
>> This definitely shows a problem. Either there is something else running
>> and binding to the wildcard IPv6 socket or there is a problem with
>> support of IPv6.
> I've seen this problem with other programs under linux's ipv6.  The
> problem is that the linux stack unlike the Kame stack used in BSD's
> uses mapped ipv4 addresses in ipv6.  If one opens up a whildcard
> listening socket for both the ipv4 stack (with AF_INET) and then again
> for the ipv6 stack (with AF_INET6), one ends up trying to open the v4
> port a second time through the mapped-address.  The trick is to only
> open up the AF_INET6 socket - it implies the ipv4 mapping.
> I imagine this effects any daemon listening on an ipv6 socket in
> linux.
> -wolfgang

This is probably what is causing the problems in bug #135 and bug #716.
If this true then it's a bug in the IP stack of the O/S and should get
fixed. IPv6 addresses are unrelated to IPv4 addresses and should never
be mixed. Such attempts to do so cause many problems and this is just
one symptom. You should get your O/S vendor to address the problem. I
will try one thing and try and bind the IPv6 wildcard address (::) first
and then the IPv4 address ( but I don't know if that will really
make a difference if this is badly architected by the O/S.


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