[Bug 1969901] Re: network-manager fails to renew ipv6 address

[Jeremy Bicha]

** Changed in: network-manager (Ubuntu Bionic)
       Status: Incomplete => In Progress

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Title:
  network-manager fails to renew ipv6 address

Status in network-manager package in Ubuntu:
  Fix Released
Status in network-manager source package in Bionic:
  In Progress

Bug description:
  [Impact]

   * This affects Ubuntu 18.04 where Network Manager version 1.10.6 is
  used.

   * Network manager might kill dhclient(6) and fail to start it again
     causing the IPv6 address to be lost on a network that uses mixed
     IPv4/IPV6.
     The network status will still be seen as online in gnome since ipv4
     is still active.
     The user then have to manually remove the dhcpv6 lease files and
     restart ipv6 connection/restart network manager to regain IPv6
     connectivity.

   * This is a cherry-pick from Network manager 1.10.8 (Ubuntu's version
     is based on 1.10.6):
     https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/commit/7fbbe7ebee99785e38d39c37e515a64a28edef0f

   * Upstream bug:
     https://bugzilla.gnome.org/show_bug.cgi?id=783391

  [Test Plan]

  The test requires three computers
  * one computer runing isc dhcpd server (with network configured static)
  * one computer running patched network manager
  * one computer running vanilla ubuntu

  The idea is to execute on an isolated network and trigger the error by changing
  ip range handed out by the dhcp-server to force a nack response back to the
  clients.

  Expected result
  * patched network keeps dhclient6 alive
  * vanilla network manager will fail to keep dhclient6 alive
    in network manager logs dhcp6 will expire and not be restarted

  ON THE SERVER
  # Disable app-armor, as it has rules restricting dhcpd
  aa-teardown

  # install isc dhcpserver
  isc-dhcp-server

  # configure network static
  sudo nmcli connection modify "${CONNECTION_NAME}" \
       ipv4.method "manual" \
       ipv4.addresses "192.168.1.1/24" \
       ipv4.gateway "192.168.1.254" \
       ipv4.dns "192.168.1.1" \
       ipv6.method "manual" \
       ipv6.addresses "2001:db8:0:1::1/64" \
       ipv6.gateway "2001:db8:0:1::ffbb" \
       ipv6.dns "2001:db8:0:1::1/64"

  mkdir -p tmp
  touch tmp/dhcpd4_a.leases
  touch tmp/dhcpd4_b.leases
  touch tmp/dhcpd6_a.leases
  touch tmp/dhcpd6_b.leases

  Then it is time to execute dhcpd
  -f - run in foreground
  -d - print errors to stderr instead of syslog

  # Start in separate terminals
  dhcpd -f -d -4 -cf dhcp_v4_a.conf -lf tmp/dhcpd4_a.leases enp0s31f6
  dhcpd -f -d -6 -cf dhcp_v6_a.conf -lf tmp/dhcpd6_a.leases enp0s31f6

  Press ctrl-C to kill servers, then restart with the b configurations

  dhcpd -f -d -4 -cf dhcp_v4_b.conf -lf tmp/dhcpd4_b.leases enp0s31f6
  dhcpd -f -d -6 -cf dhcp_v6_b.conf -lf tmp/dhcpd6_b.leases enp0s31f6

  Then leases to expire (check for clients that kills dhclient)
  Press ctrl-C to kill servers, then restart with the a configurations

  ON THE CLIENTS
  Setup:
  Configure ipv6 network in settings to use dhcp (using the gui)

  Test:
  check that dhcp clients are still running:
  ps aux|grep dhclient

  Expected in output
  one client for dhcpv4
  one client for dhcpv6

  Also check network manager status :
  journalctl -u NetworkManager.service
  journalctl -u NetworkManager.service|grep dhcp6 # to only view dhclient6
  journalctl -u NetworkManager.service|grep dhcp4 # to only view dhclient4

  if dhclient is not running:
  stop network in gui
  remove lease files (/var/lib/NetworkManager/dhclient*.lease). Only remove the lease for the client not running.
  start network in gui

  if dhclients are running:
  wait additional ten minutes, repeat from beginning of test

  [Where problems could occur]

   * The change is in the dchp lease expiration handling so verify that
  there is no regression in dhcp renewals on different type of
  configuration include IPv6

  [Other Info]
   * We have tested this patch on a couple of clients where we have seen this
     this problem. If this patch is feasible to include in Ubuntu 18.04 we
     could request more users to test.

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