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  • Committer: Teddy Hogeborn
  • Date: 2015-05-23 20:18:34 UTC
  • mto: (237.7.304 trunk)
  • mto: This revision was merged to the branch mainline in revision 325.
  • Revision ID: teddy@recompile.se-20150523201834-e89ex4ito93yni8x
mandos: Use multiprocessing module to run checkers.

For a long time, the Mandos server has occasionally logged the message
"ERROR: Child process vanished".  This was never a fatal error, but it
has been annoying and slightly worrying, since a definite cause was
not found.  One potential cause could be the "multiprocessing" and
"subprocess" modules conflicting w.r.t. SIGCHLD.  To avoid this,
change the running of checkers from using subprocess.Popen
asynchronously to instead first create a multiprocessing.Process()
(which is asynchronous) calling a function, and have that function
then call subprocess.call() (which is synchronous).  In this way, the
only thing using any asynchronous subprocesses is the multiprocessing
module.

This makes it necessary to change one small thing in the D-Bus API,
since the subprocesses.call() function does not expose the raw wait(2)
status value.

DBUS-API (CheckerCompleted): Change the second value provided by this
                             D-Bus signal from the raw wait(2) status
                             to the actual terminating signal number.
mandos (subprocess_call_pipe): New function to be called by
                               multiprocessing.Process (starting a
                               separate process).
(Client.last_checker signal): New attribute for signal which
                              terminated last checker.  Like
                              last_checker_status, only not accessible
                              via D-Bus.
(Client.checker_callback): Take new "connection" argument and use it
                           to get returncode; set last_checker_signal.
                           Return False so gobject does not call this
                           callback again.
(Client.start_checker): Start checker using a multiprocessing.Process
                        instead of a subprocess.Popen.
(ClientDBus.checker_callback): Take new "connection" argument.        Call
                               Client.checker_callback early to have
                               it set last_checker_status and
                               last_checker_signal; use those.  Change
                               second value provided to D-Bus signal
                               CheckerCompleted to use
                               last_checker_signal if checker was
                               terminated by signal.
mandos-monitor: Update to reflect DBus API change.
(MandosClientWidget.checker_completed): Take "signal" instead of
                                        "condition" argument.  Use it
                                        accordingly.  Remove dead code
                                        (os.WCOREDUMP case).

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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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        "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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<!ENTITY COMMANDNAME "usplash">
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<!ENTITY TIMESTAMP "2019-02-10">
 
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<!ENTITY TIMESTAMP "2012-01-01">
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<!ENTITY % common SYSTEM "../common.ent">
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%common;
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]>
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    <copyright>
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      <year>2008</year>
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      <year>2009</year>
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      <year>2010</year>
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      <year>2011</year>
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      <year>2012</year>
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      <year>2013</year>
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      <year>2014</year>
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      <year>2015</year>
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      <year>2016</year>
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      <year>2017</year>
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      <year>2018</year>
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      <year>2019</year>
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      <holder>Teddy Hogeborn</holder>
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      <holder>Björn Påhlsson</holder>
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    </copyright>
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        <para>
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          These variables will normally be inherited from
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          <citerefentry><refentrytitle>plugin-runner</refentrytitle>
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          <manvolnum>8mandos</manvolnum></citerefentry>, which might
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          have in turn inherited them from its calling process.
 
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          <manvolnum>8mandos</manvolnum></citerefentry>, which will
 
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          normally have inherited them from
 
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          <filename>/scripts/local-top/cryptroot</filename> in the
 
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          initial <acronym>RAM</acronym> disk environment, which will
 
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          have set them from parsing kernel arguments and
 
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          <filename>/conf/conf.d/cryptroot</filename> (also in the
 
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          initial RAM disk environment), which in turn will have been
 
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          created when the initial RAM disk image was created by
 
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          <filename
 
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          >/usr/share/initramfs-tools/hooks/cryptroot</filename>, by
 
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          extracting the information of the root file system from
 
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          <filename >/etc/crypttab</filename>.
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        </para>
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        <para>
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          This behavior is meant to exactly mirror the behavior of
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      is ugly, but necessary as long as it does not support aborting a
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      password request.
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    </para>
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    <xi:include href="../bugs.xml"/>
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  </refsect1>
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  <refsect1 id="example">
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    <para>
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      <citerefentry><refentrytitle>intro</refentrytitle>
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      <manvolnum>8mandos</manvolnum></citerefentry>,
 
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      <citerefentry><refentrytitle>crypttab</refentrytitle>
 
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      <manvolnum>5</manvolnum></citerefentry>,
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      <citerefentry><refentrytitle>fifo</refentrytitle>
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      <manvolnum>7</manvolnum></citerefentry>,
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      <citerefentry><refentrytitle>plugin-runner</refentrytitle>