Hi Andreas,
yes, the thing was, that a (dCache) pool accidentialy did not get an
AAAA assigned, when it got deployed. So, in some sense, the behaviour
was a good smoke test to notice the issue ;)
On the way, I had been thinking, if/what things to consider might be
there, when there are more complex constellations coming, with
IPv4-only, IPv6-only and dual-stack nodes trying to interact with each
other through redirects or such more 'indirect' paths...
Cheers,
Thomas
On 26/11/2020 10.43, Andreas Petzold (SCC) wrote:
> Hi Thomas,
>
> your question sounds a bit like a mix between dCache and SLAC xrootd ;-)?
>
> Of course the experts should comment, but let me add my 2 cents.
>
> If you are talking about SLAC xrootd, I don't see a reason why a
> transition between v6 and v4 would not work.
>
> The dual-stack client connects to the xrootd manager/redirector via v6
> and gets told where to connect to access the file. If that _new_
> connection is made via v4 or v6 should not matter. It is always a new
> connection for the client and that's the beauty of the protocol (IMHO).
>
> How dCache handles a situation like this when you have an xrootd client
> connecting to a dCache xrootd door via v6 and you have dCache pools on
> v4, I don't know.
>
> Cheers,
>
> Andreas
>
>
> On 25/11/2020 14.10, Thomas Hartmann wrote:
>> Hi all,
>>
>> would it be in principle possible, that the xrd client reastablishes a
>> conenction on IPv4 after the initital connection got established over
>> IPv6?
>>
>> E.g.,
>> a dual-stack client connects to a dual-stack redirector/door and the
>> connection is established on v6. The requested file is only available
>> on a IPv4 node and the redirector points to the pools DNS, that only
>> resolves for A but not AAAA.
>> The redirect fails as the non-resolved v6 ends up as an invalid
>> redirect URL.
>>
>> I guess, that client/server do not have much chance, after the IP
>> flavour got negotiated on the network stack, or?
>>
>> Cheers,
>> Thomas
>>
>>
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