[libvirt-users] "error: error creating bridge interface virbr0: Operation not supported" occurred what net-start default

[Laine Stump]

On 08/24/2015 11:26 PM, Michal Privoznik wrote:
> On 23.08.2015 07:20, chenhongzhen at zhicloud.com wrote:
>> Hi, All!
>>
>> I found a bug!
>> When I start the default network, I got a error shown as below:
>>
>> [root at localhost ~]# virsh net-start default
>> error: Failed to start network default
>> error: error creating bridge interface virbr0: Operation not supported
>>
> I think it's caused by commit fc7b23db (released in 1.2.14). For some
> reason, older kernels do not know how to create a bridge via netlink. I
> wonder if we should workaround it somehow.

Yep, I had come to the same conclusion earlier today, but was going to
confirm it before replying and haven't yet had time (chasing other ugly
regressions caused by modifying perfectly good working code - someday
maybe I will learn!). The horrible part is I'm almost certain that I had
either tested it on RHEL6, or was given verification by someone else in
an apparent position of knowledge that it would work properly (but I see
there's no indication of that in the bugzilla record or commit log, so
either it happened in IRC or I'm just on crack).

Definitely if it doesn't work, we need to work around it. Even though
the official downstream version of libvirt on RHEL6/CentOS6 doesn't have
that patch, we so far are supporting upstream builds on RHEL6/CentOS6.
Of course if creating a bridge with netlink doesn't work, then deleting
the bridge with netlink also likely won't work, and changing back to the
old ioctl method will potentially reintroduce a bug that had been
stamped out by the switch :-(