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RE: [EXTERNAL] RE: IPv6 resolution problems for IPv4 resolve mode

From: Dmitry Karpov via curl-library <curl-library_at_lists.haxx.se>
Date: Mon, 19 Sep 2022 20:24:11 +0000

> I previously expressed my concerns and ideas about the approach in the patch.
> Did that go anywhere?

I think I replied on all the concerns in the e-mail thread and explained why using dual queries in the IPv4-resolve only mode is a potential source of IPv6-related regressions - even for the case for which the dual queries were introduced.

Yes, in the thread there were some ideas expressed about separation of the "IP resolve" mode for DNS and connection establishment (i.e. additional bits or option(s)), but I didn't see that there was some concrete conclusion about a good solution for this problem, which was easy to understand, use and implement.

And without these new additional options, using explicit "IPv4 only" resolve mode should provide protection from bad IPv6 side effects for the transfers which don't want to do anything IPv6-related and that's what my patch is doing.
Maybe, it is a temporary or intermediate solution, but it makes IPv6-enabled libcurl to behave the same way as IPv4 single-stack libcurl for "IPv4 only" transfers.

> I propose you go ahead and make a pull-request out of it to get it tracked, tested, reviewed and commented on further.

Sounds good, I will try to do that.

Thanks,
Dmitry Karpov

-----Original Message-----
From: Daniel Stenberg <daniel_at_haxx.se>
Sent: Monday, September 19, 2022 12:19 AM
To: Dmitry Karpov via curl-library <curl-library_at_lists.haxx.se>
Cc: Dmitry Karpov <dkarpov_at_roku.com>
Subject: [EXTERNAL] RE: IPv6 resolution problems for IPv4 resolve mode

On Fri, 16 Sep 2022, Dmitry Karpov via curl-library wrote:

> As I still see problems with IPv6 name resolutions on a large
> population (62M+ instances in my case), I would like this subject not to be forgotten.
> My patch (provided at the beginning of this thread) prohibiting using
> IPv6 name resolutions for IPv4-only resolve mode in dual-stack enabled
> libcurl, proved to be helpful to mitigate bad IPv6 side effects for the IPv4 mode.

I previously expressed my concerns and ideas about the approach in the patch.
Did that go anywhere?

I propose you go ahead and make a pull-request out of it to get it tracked, tested, reviewed and commented on further.

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Received on 2022-09-19