GNU bug report logs - #36350
[2.2.5] ‘read-headers’ blocks, thereby breaking web servers

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Ludovic Courtès <ludo <at> gnu.org>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#36350: closed ([2.2.5] ‘read-headers’
 blocks, thereby breaking web servers)
Date: Sun, 30 Jun 2019 19:51:01 +0000

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Your message dated Sun, 30 Jun 2019 21:50:17 +0200
with message-id <878stisvie.fsf <at> gnu.org>
and subject line Re: bug#36350: [2.2.5] ‘read-headers’ blocks, thereby breaking web servers
has caused the debbugs.gnu.org bug report #36350,
regarding [2.2.5] ‘read-headers’ blocks, thereby breaking web servers
to be marked as done.

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help-debbugs <at> gnu.org.)


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36350: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=36350
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From: Ludovic Courtès <ludo <at> gnu.org>
To: bug-guile <at> gnu.org
Cc: Mark H Weaver <mhw <at> netris.org>
Subject: [2.2.5] ‘read-headers’ blocks, thereby
 breaking web servers
Date: Mon, 24 Jun 2019 12:32:18 +0200

Hello,

In Guile 2.2.5, if you run:

  ./meta/guile examples/web/hello.scm &
  wget -O - http://localhost:8080

You’ll notice that ‘wget’ hangs (never receives a response) because the
server is actually stuck in a read(2) call that will never complete, in
‘read-headers’.

Reverting 73cde5ed7218a090ecee888870908af5445796f0 solves the problem.

AIUI, before that commit, ‘read-header-line’ would read exactly one
line.  After this change, it calls ‘lookahead-char’, which can block,
and that’s exactly what’s happening here.

I don’t know how HTTP continuation lines work, so I’m not sure what a
correct fix would look like.  Mark, WDYT?

I also noticed that there are no unit tests for (web server), which we
should probably address while we’re at it.  :-)

Thanks,
Ludo’.

[Message part 3 (message/rfc822, inline)]

From: Ludovic Courtès <ludo <at> gnu.org>
To: Mark H Weaver <mhw <at> netris.org>
Cc: 36350-done <at> debbugs.gnu.org
Subject: Re: bug#36350: [2.2.5] ‘read-headers’
 blocks, thereby breaking web servers
Date: Sun, 30 Jun 2019 21:50:17 +0200

Hi,

Mark H Weaver <mhw <at> netris.org> skribis:

> Ludovic Courtès <ludo <at> gnu.org> writes:
>> Perhaps we should consider releasing 2.0.6 soon and use that in Guix
>> on ‘core-updates’.
>
> Sure, sounds like a good idea.

Done in a152a67d3865cc6e7f9d7abd8f17a6e905b8e841.  The test is simple
but would catch regressions like this one.

Ludo’.

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