[Bug 1766969] Re: DNS cannot be resolved in Public / Hotel / Starbucks WiFi Hotspot

[Steve Langasek]

I confirm that this fixes the problem for the newly rolled out Starbucks
aruba hotspots.

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https://bugs.launchpad.net/bugs/1766969

Title:
  DNS cannot be resolved in Public / Hotel / Starbucks WiFi Hotspot

Status in systemd package in Ubuntu:
  Fix Committed
Status in systemd source package in Artful:
  Confirmed
Status in systemd source package in Bionic:
  Fix Committed
Status in systemd source package in Cosmic:
  Fix Committed

Bug description:
  [Impact]

   * More captive portals have been discovered that do not handle DNS requests with D0 set.
   * Thus extend previous aruba-networks fix from https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1727237 by retrying all NXDOMAIN results with lower feature levels just in case.

  [Test Case]

   * systemd-resolved something-nonexistant.ubuntu.com
   * monitor the logs, and check that the transaction has been downgraded multiple times and tried at least once at a feature level below D0. There should be a downgrade message in the log.
   * Note, it will be cached, thus one may need to call $ systemd-resolved --flush-caches

  [Regression Potential]

   * Legitimate NXDOMAIN queries will now take longer, as they will be
  retried multiple times with different features sets until an answer is
  found. At that point the query will be cached and will return quickly.
  This is needed to work-around bad captive portals that do not support
  dns queries with D0. Post-captive portal, the feature level can
  usually be cranked back up and it does after a grace period.

  [Other Info]
   
   * Original bug report

  I was asked to create a new bug for this in
  https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1727237 as it
  seems to be a different issue.

  I have installed the nightly image of Kubuntu Bionic from 25th of
  April.

  There systemd is in version 237-3ubuntu10.

  When connecting to the wifi hotspot in my hotel (Quality Hotel
  Augsburg) I cannot open the hotspot landing page that should give me
  access to the WIFI. With Windows and on an Iphone it's working.

  For the following distributions I can confirm it not working:
  Kubuntu 17.10
  Kubuntu 18.04 (nightly image 25th of April 2018)

  The logs were taken on 18.04.

  Workaround:
  sudo systemctl disable systemd-resolved.service
  sudo service systemd-resolved stop
  sudo rm /etc/resolv.conf
  sudo nano /etc/NetworkManager/NetworkManager.conf
    >> add "dns=default" under [main]
  sudo service network-manager restart

  Then I can connect to the WIFI and I see the login page in Firefox.

  To capture some data I did the following:
   - connect to Hotspot
   - enter golem.de

  Case 1: Fresh default Kubuntu install
  With a default Kubuntu install it does not work. I can connect to the WIFI and get IP and DNS from DHCP but I cannot resolve any hostname. When trying  to open the router ip directly in the browser it forwards to hotsplots.de which cannot be resolved.

  Case 2: With aforementioned Workaround
  I connect to the wifi, I open firefox and the login page shows up (if I havent been connected yet. In the capture I already was able to connect to the hotspot which allows immediately to connect to the webpage)

  PS: I'll be in this hotel till Friday 27th if more information are
  required.

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