GNU bug report logs - #40748
28.0.50; Switching wifi networks hangs dns lookups

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Package: emacs; Reported by: Eric Abrahamsen <eric@HIDDEN>; merged with #41234; dated Tue, 21 Apr 2020 17:12:02 UTC; Maintainer for emacs is bug-gnu-emacs@HIDDEN.
Forcibly Merged 40748 41234. Request was from Lars Ingebrigtsen <larsi@HIDDEN> to control <at> debbugs.gnu.org. Full text available.

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From: Dmitry Alexandrov <dag@HIDDEN>
To: Eric Abrahamsen <eric@HIDDEN>
Subject: Re: bug#40748: 28.0.50; Switching wifi networks hangs dns lookups
In-Reply-To: <878sio3gtd.fsf@HIDDEN> (Eric Abrahamsen's message of
 "Tue, 21 Apr 2020 10:10:54 -0700")
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> I often have trouble reconnecting Gnus' nntp servers after sleeping the l=
aptop in one location, and waking it up in another, connecting to a new wif=
i network

> I edebugged `nntp-open-connection', and realized that the error =E2=80=B9=
=E2=80=A6=E2=80=BA is actually a dns error:

Looks familiar!

> Here's the code that opens the connection; in my case it's nntp-open-netw=
ork-stream/network.

Could not it actually be an even deeper issue I outlined in bug#41234: 27.0=
.91; Synchronous network requests are failing with =E2=80=9CName or service=
 not known=E2=80=9D [1]?

[1] <mid:1rnogg6b.dag@HIDDEN>
    <https://bugs.gnu.org/41234>

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Information forwarded to bug-gnu-emacs@HIDDEN:
bug#40748; Package emacs. Full text available.

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From: Eric Abrahamsen <eric@HIDDEN>
To: bug-gnu-emacs@HIDDEN
Subject: 28.0.50; Switching wifi networks hangs dns lookups
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I'm on Emacs master, but this behavior has been evident for quite some
time, a year or two I think.

I often have trouble reconnecting Gnus' nntp servers after sleeping the
laptop in one location, and waking it up in another, connecting to a new
wifi network (I'm using Arch linux, if it matters).

I edebugged `nntp-open-connection', and realized that the error (which
is getting handled by `nnheader-report', that's why I didn't notice it)
is actually a dns error:

(error "news.gmane.io/nntp Temporary failure in name resol...")

Other Emacs network connections behave as normal. But this error for
this particular server persists until I restart Emacs.

Are DNS lookups cached? Cached per connection? Is there anything we can
do to flush whatever's "stuck"?

Here's the code that opens the connection; in my case it's
nntp-open-network-stream/network.

Happy to help with further debugging!

(let ((coding-system-for-read 'binary)
      (coding-system-for-write 'binary)
      (map '((nntp-open-network-stream network)
	     (network-only plain)	; compat
	     (nntp-open-plain-stream plain)
	     (nntp-open-ssl-stream tls)
	     (nntp-open-tls-stream tls))))
  (if (assoc nntp-open-connection-function map)
      (open-network-stream
       "nntpd" pbuffer nntp-address nntp-port-number
       :type (cadr (assoc nntp-open-connection-function map))
       :end-of-command "^\\([2345]\\|[.]\\).*\n"
       :capability-command "HELP\r\n"
       :success "^3"
       :starttls-function
       (lambda (capabilities)
	 (if (not (string-match "STARTTLS" capabilities))
	     nil
	   "STARTTLS\r\n")))
    (funcall nntp-open-connection-function pbuffer)))




Acknowledgement sent to Eric Abrahamsen <eric@HIDDEN>:
New bug report received and forwarded. Copy sent to bug-gnu-emacs@HIDDEN. Full text available.
Report forwarded to bug-gnu-emacs@HIDDEN:
bug#40748; Package emacs. Full text available.
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Last modified: Wed, 29 Jul 2020 05:45:02 UTC

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