[dnsdist] Does dnsdist support pipelining on TCP?

[Remi Gacogne]

On 1/15/20 11:40 AM, Daniel Stirnimann wrote:
> On 15.01.20 11:07, Stephane Bortzmeyer wrote:
>> On Wed, Jan 15, 2020 at 10:54:55AM +0100,
>>  Daniel Stirnimann <daniel.stirnimann at switch.ch> wrote 
>>  a message of 13 lines which said:
>>
>>> The last time I looked at it (a few weeks ago) the authors confirmed
>>> that it supports TCP pipelining but not with out of order responses.
>>
>> Well, pipelining in that case is just a buffering of incoming
>> requests, it is not really useful.

I agree pipelining by itself is not very useful, but at the very least
it prevents breaking the connection even if out-of-order is not supported.

Implementing out-of-order would have been very painful before 1.4.0
because of the way TCP connections were handled. It should be much
easier since 1.4.0 but as far as I know nobody cared enough to start
working on it. The fact that very few real-life clients actually make
use of it can probably begin to explain why :-/

> I should have said that it supports TCP pipelining with ordered
> responses from clients but supports TCP pipelining with out of order
> responses when talking to the backend (if the backend supports it). See
> also
> https://dnsprivacy.org/wiki/display/DP/DNS+Privacy+Implementation+Status

That does not sound right, we don't support out-of-order, period, be it
client-side or server-side.

Best regards,
-- 
Remi Gacogne
PowerDNS.COM BV - https://www.powerdns.com/

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