[ovs-dev] [PATCH] ovs-ctl: Don't overwrite external-id hostname

[Han Zhou]

On Mon, May 25, 2020 at 8:28 AM Daniel Alvarez <dalvarez at redhat.com> wrote:
>
> ovs-ctl started to add the hostname as external-id [0] at some point.
>
> However, this can be problematic as if it's already set by an external
> entity it will get overwritten. In RHEL systems, systemd will invoke
> ovs-ctl to start OVS and that will overwrite it to the hostname of the
> machine.
>
> For OVN this can have a big impact because if, for whatever reason the
> hostname changes and the host gets restarted, ovn-controller won't
> claim the ports back leaving the workloads unaccessible.
>
> Also, it makes sense to not overwrite it as 1) it's an external_id,
> so it will actually let external entities to configure it (unlike now),
> and 2) it's optional. In the case that some systems were relying on
> ovs-ctl to set the external-id for the first time (e.g onboarding
> of a new hypervisor), this patch is not changing such behavior.
>
> For more details, see discussion at [1].
>
> [0] https://mail.openvswitch.org/pipermail/ovs-dev/2016-March/312054.html
> [1] https://mail.openvswitch.org/pipermail/ovs-dev/2020-May/370813.html
>
> Signed-off-by: Daniel Alvarez <dalvarez at redhat.com>
> ---
>  utilities/ovs-ctl.in | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/utilities/ovs-ctl.in b/utilities/ovs-ctl.in
> index 8c5cd7032..9be9c9871 100644
> --- a/utilities/ovs-ctl.in
> +++ b/utilities/ovs-ctl.in
> @@ -43,7 +43,8 @@ set_hostname () {
>      else
>          hn="$(uname -n)"
>      fi
> -    ovs_vsctl set Open_vSwitch . external-ids:hostname="$hn"
> +    # Set the hostname if it wasn't set before
> +    ovs_vsctl add Open_vSwitch . external-ids hostname="$hn"
>  }
>
>  set_system_ids () {
> --
>
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Acked-by: Han Zhou <hzhou at ovn.org>