[Bug 1545302] Re: wpa-roam broken by fix for ifupdown #1337873

[Martin Pitt]

Thanks Dariusz! I sponsored the trusty and wily fixes, sitting in the
SRU review queues now.

** Also affects: wpa (Ubuntu Trusty)
   Importance: Undecided
       Status: New

** Also affects: wpa (Ubuntu Wily)
   Importance: Undecided
       Status: New

** Changed in: wpa (Ubuntu)
       Status: Confirmed => Fix Released

** Changed in: wpa (Ubuntu Trusty)
       Status: New => In Progress

** Changed in: wpa (Ubuntu Wily)
       Status: New => In Progress

** Changed in: wpa (Ubuntu Trusty)
     Assignee: (unassigned) => Dariusz Gadomski (dgadomski)

** Changed in: wpa (Ubuntu Wily)
     Assignee: (unassigned) => Dariusz Gadomski (dgadomski)

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https://bugs.launchpad.net/bugs/1545302

Title:
  wpa-roam broken by fix for ifupdown #1337873

Status in wpa package in Ubuntu:
  Fix Released
Status in wpa source package in Trusty:
  In Progress
Status in wpa source package in Wily:
  In Progress

Bug description:
  [Impact]

   * In some configurations recurrent ifup/down calls are broken due to
  a false-positive recursion detection.

   * In certain situations it leaves interfaces unconfigured (in this
  case: WLAN interface connected to WiFi network, but dhcp fails).

  [Test Case]

   * Setup wpa-roam configuration based on what is in comment #6
   
   * Wait until wpa_supplicant connects to a wifi network

   * Run ifconfig to check if the WLAN interface received dhcp info

   * Expected result: WLAN is fully configured according to dhcp settings
   
   * Actual result: WLAN is connected to WiFi but not configured

  [Regression Potential]

   * Fixed upstream, fix present in Xenial.

   * Debdiffs contain a backport of an upstream fix.

  [Other Info]
   
   * Original bug description:

  The following versions of ifupdown introduced a recursion check using "IFUPDOWN_<interface>" environment variables along with a new locking mechanism for ifup (see #1337873):
  0.7.47.2ubuntu4.2 (in Trusty)
  0.7.54ubuntu1.1 (in Wily)
  0.7.54ubuntu2 (in Xenial)

  This recursion check breaks the wpa-roam feature of wpasupplicant,
  preventing it from loading the logical interface specified by id_str
  after associating with an AP.  Specifically, after upgrading to one of
  the above ifupdown versions, the '/sbin/ifup -v --force
  "$WPA_IFACE=$WPA_LOGICAL_IFACE"' command run by wpa_action in
  functions.sh fails with an "ifup: recursion detected for parent
  interface wlan0 in post-up phase" error.

  To fix the issue, functions.sh needs to run `unset
  "IFDOWN_$WPA_IFACE"` before calling /sbin/ifup to prevent ifup from
  detecting the recursion.  The attached patch implements this change.

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