Public bug reported:
[Impact]
Some network interfaces on a Xen guest are broken by new behavior
introduced by netplan. On a Xen guest instance, when netplan is run to
'apply' its configuration, under certain circumstances netplan will try
to "reset" the interface by unbinding and then re-binding the interface
driver from the interface, by using the sysfs "bind" and "unbind"
functions of the driver. Normally, this results in the interface being
released and then fully re-initialized by the driver.
However the Xen VIF driver breaks when this is done. The internal Xen
backend state of the interface remains in 'closed' state after the
driver re-connects to the interface, and attempts to open and use the
interface result in a kernel Oops in the Xen VIF driver.
To users, it appears that the interface is unusable because it has an
all 0 mac address; but if the mac is manually set and the interface
brought up the driver Oopses as mentioned above.
This problem makes booting painful because of very long timeouts waiting
for all network interfaces to start, and affected Xen VIF interfaces
will of course never complete startup.
[Fix]
No fix yet. Upstream kernel does not appear fixed.
[Test Case]
Create a guest instance under a Xen hypervisor (e.g. an AWS instance)
that has Ubuntu Artful 17.10 installed. Use only a single interface at
first when creating it. Then once it is ready, attach a second network
interface to the instance. From inside the instance, configure the new
interface in netplan (i.e. add a /etc/netplan/ config for it). Make
sure the new interface is down (netplan does not appear to unbind/bind
interfaces that are up), and then run:
$ sudo netplan apply
or for debug,
$ sudo netplan --debug apply
this will unbind and re-bind the second interface, which will then have
all-0 mac, and will be unusable, as described above.
[Regression Potential]
Changes to the Xen VIF driver can result in unusable network interfaces,
or problems while using Xen VIF interfaces.
[Other Info]
Problem appears to exist upstream also.
** Affects: linux (Ubuntu)
Importance: High
Assignee: Dan Streetman (ddstreet)
Status: In Progress
** Affects: linux (Ubuntu Artful)
Importance: High
Assignee: Dan Streetman (ddstreet)
Status: In Progress
** Affects: linux (Ubuntu Bionic)
Importance: High
Assignee: Dan Streetman (ddstreet)
Status: In Progress
** Tags: sts
** Changed in: linux (Ubuntu)
Status: New => In Progress
** Changed in: linux (Ubuntu)
Assignee: (unassigned) => Dan Streetman (ddstreet)
** Changed in: linux (Ubuntu)
Importance: Undecided => High
** Also affects: linux (Ubuntu Bionic)
Importance: High
Assignee: Dan Streetman (ddstreet)
Status: In Progress
** Also affects: linux (Ubuntu Artful)
Importance: Undecided
Status: New
** Changed in: linux (Ubuntu Artful)
Status: New => In Progress
** Changed in: linux (Ubuntu Artful)
Importance: Undecided => High
** Changed in: linux (Ubuntu Artful)
Assignee: (unassigned) => Dan Streetman (ddstreet)
** Tags added: sts sts-sponsor
** Tags removed: sts-sponsor
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https://bugs.launchpad.net/bugs/1729573
Title:
netplan breaks Xen VIF driver
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