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[Michael Vogt <1721223@xxxxxxxxxxxxxxxxxx>]

** Project changed: snappy => snapd

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https://bugs.launchpad.net/bugs/1721223

Title:
  Networkd fail to set ip address between leases if ip address changes
  on UbuntuCore

Status in snapd:
  Fix Committed
Status in systemd package in Ubuntu:
  Fix Released
Status in systemd source package in Xenial:
  Fix Released
Status in systemd source package in Zesty:
  Won't Fix
Status in systemd source package in Artful:
  Fix Released

Bug description:
  [Impact]

   * networkd fails to renew a lease, specifically it fails to change IPv4 address via DHCP renew/rebind.
   * networkd relies on a kernel feature to promote secondary IPv4 address to primary, upon primary address lease expiry.
   * this sysctl tunable was not enabled by default in systemd.

  [Test Case]

  Add a device, and assign two IPv4 addresses. First one, with a short
  lease time. Second one, with a different ip and a longer lease time.
  Second one should be treated as secondary ip address, and upon expiry
  of the first one, should be promoted and become primary ip address.
  The below scripted instructions simulate this:

  sudo ip link add name testleases type dummy

  sudo ip address add 192.0.2.10/27 dev testleases \
    valid_lft 5 preferred_lft 5

  sudo ip address add 192.0.2.11/27 dev testleases \
    valid_lft 11 preferred_lft 11

  ip address list dev testleases | \
  grep -q 'inet 192.0.2.10/27 scope global dynamic testleases' \
  && echo ok || echo not ok

  ip address list dev testleases | \
  grep -q 'inet 192.0.2.11/27 scope global secondary dynamic testleases' \
  && echo ok || echo not ok

  sleep 6

  ip address list dev testleases | \
  grep -q 'inet 192.0.2.11/27 scope global dynamic testleases' \
  && echo ok || echo not ok

  sudo ip link del dev testleases

  [Regression Potential]

   * This changes the default kernel behaviour, previously upon expiry
  of the primary address, secondary addresses were removed as well.
  Which is imho silly.

  * comparing networkd renewal with isc-dhcp renewal the semantics are
  quite different. Upon acquiring new ip address, isc-dhcp would
  instantly flush existing ip address, and add a new one. Networkd add
  the new address as secondary, and waits for old one to expire first
  before promoting / switching to using the new ip address. IMHO kernel
  should have an API to promote secondary ip address to a primary one.

  * This update also applies other safe-looking options, which are
  currently also already applied via sysctls shipped in other packages

  # Source route verification
  net.ipv4.conf.default.rp_filter = 1
  net.ipv4.conf.all.rp_filter = 1

  # Do not accept source routing
  net.ipv4.conf.default.accept_source_route = 0
  net.ipv4.conf.all.accept_source_route = 0

  # Enable hard and soft link protection
  fs.protected_hardlinks = 1
  fs.protected_symlinks = 1

  * This update also applies the following upstream/bufferbloat.net
  recommended setting

  # Fair Queue CoDel packet scheduler to fight bufferbloat
  net.core.default_qdisc = fq_codel

  * [~racb] There are complex network setups out there, such as HA with
  corosync/pacemaker, OpenStack Neutron, and that kind of thing. If this
  fix were SRU'd, will all of these things in the wild cope with this
  sysctl change?

  [Other Info]

   * Original bug report

  Hi there,
  we found a replicable issue that involves the Ubuntu Core networking and causes complete loss of connectivity.
  We run a custom board with ubuntu core: the architecure is amrhf.
  We replicated this issue with an official Ubuntu Core image on a Raspberry Pi: other platform was been tested.
  It shows that it is a snap core problem which interests networkd: we use the default network stack based on networkd + netplan.

  Below steps to replicate the issue.

      1)Setup a dhcp server for lease of about some minutes (i.e 10 minutes).
      2)Boot the board and wait for get an ip from dhcp server
      3)Before the lease expires, set a reservation for a different ip address

  Depending on lease duration before the lease expires( for 10 minute we have 2 minutes before ), networkd configure the new address in addition to the previous one.
  When the lease expire both ip address ( the prevoius and the new one ) disappear from the interested network interface.
  Depending on lease duration before the second lease expires ( for 10 minure we have 2 minutes before ) networkd configure only the new ip address on the network interface and the ping toward an outside host work properly.

  During the test the dhcp server records correctly leases and their
  duration.

  We check directly from console the network interface setting with the
  tool ip, checking continuously the value for ip address and valid_lft
  fields for the interested network interface.

  Please note that if the ip address setting are the same between leases
  the problem doesn’t jump out.

  Please note that if the ip address setting are different between lease
  the problem jumps out and it is very bad:

  Typically the lease time on consumer router are about some day, then a
  board that change ip between lease loses the network connectivity for
  some day without a direct action.

  Please, after a confirmation from your side of the issue, could you
  fix the problem or escalate the issue at the upstream project?

  We are available for further testing.

  Below syslog annotated with ip address state:

  Oct  4 09:48:06 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct  4 09:49:36 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
  Oct  4 09:49:25 localhost systemd-timesyncd[996]: Network configuration changed, trying to establish connection.
  Oct  4 09:49:26 localhost systemd-timesyncd[996]: Synchronized to time server 91.189.89.199:123 (ntp.ubuntu.com).
  Oct  4 09:49:26 localhost systemd[1]: Starting Update resolvconf for networkd DNS...
  Oct  4 09:49:26 localhost systemd[1]: Started Update resolvconf for networkd DNS.
  Oct  4 09:49:37 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct  4 09:51:07 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
  Oct  4 09:51:09 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct  4 09:52:39 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
  Oct  4 09:52:40 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct  4 09:54:10 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
  Oct  4 09:54:11 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct  4 09:55:41 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
  Oct  4 09:54:23 localhost systemd-timesyncd[996]: Network configuration changed, trying to establish connection.
  Oct  4 09:54:23 localhost systemd[1]: Starting Update resolvconf for networkd DNS...
  Oct  4 09:54:23 localhost systemd-timesyncd[996]: Synchronized to time server 91.189.89.199:123 (ntp.ubuntu.com).
  Oct  4 09:54:23 localhost systemd[1]: Started Update resolvconf for networkd DNS.
  Oct  4 09:55:43 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct  4 09:57:13 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
  Oct  4 09:57:14 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct  4 09:58:44 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
  Oct  4 09:58:46 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct  4 10:00:16 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
  Oct  4 10:00:17 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct  4 10:01:47 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
  Oct  4 10:01:48 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct  4 10:03:18 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]

  Oct  4 10:03:05 localhost systemd-networkd[623]: eth0: DHCPv4 address
  192.168.5.124/24 via 192.168.5.1 -----> here begin two ip address
  state

  Oct  4 10:03:05 localhost systemd-timesyncd[996]: Network configuration changed, trying to establish connection.
  Oct  4 10:03:05 localhost systemd[1]: Starting Update resolvconf for networkd DNS...
  Oct  4 10:03:05 localhost systemd[1]: Started Update resolvconf for networkd DNS.
  Oct  4 10:03:15 localhost systemd-timesyncd[996]: Timed out waiting for reply from 91.189.89.199:123 (ntp.ubuntu.com).
  Oct  4 10:03:16 localhost systemd-timesyncd[996]: Synchronized to time server 91.189.89.198:123 (ntp.ubuntu.com).
  Oct  4 10:03:20 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct  4 10:04:50 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]

  Oct  4 10:04:23 localhost systemd-timesyncd[996]: Network
  configuration changed, trying to establish connection. ----> disappear
  any address

  Oct  4 10:04:23 localhost systemd[1]: Starting Update resolvconf for networkd DNS...
  Oct  4 10:04:23 localhost systemd[1]: Started Update resolvconf for networkd DNS.
  Oct  4 10:04:51 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct  4 10:06:21 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
  Oct  4 10:06:23 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct  4 10:07:53 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
  Oct  4 10:07:54 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct  4 10:09:24 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
  Oct  4 10:09:24 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct  4 10:10:54 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
  Oct  4 10:10:55 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct  4

  10:12:25 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ] ------>
  before this line interface eth0 don't have address, after this line
  the interfaces get 192.168.5.124/24( the second lise adddress)

  Oct  4 10:11:49 localhost systemd[1]: Starting Update resolvconf for networkd DNS...
  Oct  4 10:11:49 localhost systemd[1]: Started Update resolvconf for networkd DNS.
  Oct  4 10:12:25 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct  4 10:13:55 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
  Oct  4 10:13:18 localhost systemd[1]: Started Session 23 of user domotz.

  Cheers,
  Nicolino

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