[openstack-dev] [TripleO] dhclient spawned by dhcp-all-interfaces doesn't exit when os-net-config runs

Bob Fournier bfournie at redhat.com
Fri Nov 11 00:35:43 UTC 2016

----- Original Message -----
> From: "Dan Sneddon" <dsneddon at redhat.com>
> To: openstack-dev at lists.openstack.org
> Sent: Wednesday, November 9, 2016 4:28:55 PM
> Subject: [openstack-dev] [TripleO] dhclient spawned by dhcp-all-interfaces doesn't exit when os-net-config runs
> I just opened a bug [1] for behavior which has recently been observed
> when deploying nodes with TripleO. The problem is that the dhclient
> processes that are being started by the dhcp-all-interfaces element in
> disk-image-builder are not stopping after os-net-config runs.
> Step 1) Image deploys with udev rule to create
> dhcp-interface@<iface>.service, which configures each interface via DHCP.
> Step 2) The deployment scripts run, including os-net-config, which
> configures and restarts the interfaces. The udev rule is removed.
> At this point, the dhclient which was created by the udev rule is no
> longer needed, except it is still running and configuring IP and routes
> on the interface, possibly in conflict with the desired configuration.
> For instance, the same IP appearing on a bridge and on an interface, or
> a rogue default route and IP that hijack the default route.
> I believe this behavior is new in RHEL 7.3, but I don't know if any
> versions of CentOS are affected yet (testing is in progress).
> Running 'systemctl restart network' after os-net-config runs will kill
> the dhclient processes, so inserting that into the scripts after
> os-net-config is run is one possible workaround, although the brief
> interruption in networking might cause unknown issues in
> high-availability environments.
> Does anyone have a suggestion for a kinder, gentler, less hacky
> approach than either restarting the network service or running kill on
> the dhclient processes? Also, does anyone have any idea why running
> "ifdown <iface>" followed by "ifup <iface>" doesn't stop the dhclient
> process started by the udev rule? Or why this behavior appears to be
> new to RHEL 7.3?


Fix proposed here[2] to stop dhclient instances in os-net-config using
'-r' argument if the interface is not configured for DHCP. 



> [1] - https://bugs.launchpad.net/tripleo/+bug/1640598
> --
> Dan Sneddon         |  Senior Principal OpenStack Engineer
> dsneddon at redhat.com |  redhat.com/openstack
> dsneddon:irc        |  @dxs:twitter
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