Re: Persistent failure to lookup hostname

[<tomas@tuxteam.de>]

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On Tue, Oct 04, 2022 at 09:37:53AM +0200, Robert Pluim wrote:
> >>>>> On Mon, 03 Oct 2022 20:15:19 -0400, Stefan Monnier <monnier@iro.umontreal.ca> said:
> 
>     Stefan> Lars Ingebrigtsen [2022-10-04 01:58:28] wrote:
>     >> Stefan Monnier <monnier@iro.umontreal.ca> writes:
>     >>> My Gnus session occasionally gets into a state where it insists that my
>     >>> mail server's DNS name isn't found.
>     >> Is this with nnimap?  (I'm mostly just wondering whether this could
>     >> somehow be tied to the async code paths, which are more complicated than
>     >> the synchronous code paths and keep more state -- but nnimap doesn't use
>     >> async, so that would rule out that.)
> 
>     Stefan> Hmm... yes, I think it's always been for my IMAP server.
> 
> One thing you absolutely need to check in these situations is if DNS queries
> are making it out of Emacs at all. e.g.
> 
>     sudo tcpdump -i any -n udp and port 53

"Out of Emacs" can mean different things :)

E.g. if nscd is active, that's a caching layer somewhere at libc level (so
Emacs won't be aware of it, but the request won't hit the net, so tcpdump
won't see it). Also, for the young-uns, systemd is said to do DNS caching
itself too (what doesn't it do?), but I can't test that due to lack of
systemd ;-) That one, possibly, is also in limbo between Emacs and what
tcpdump can see (but also possibly, not).

Cheers
-- 
t

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