[ovs-dev] [PATCH] dpif-netlink-rtnl: Fix ovs_geneve probing after restart

Eric Garver e at erig.me
Wed Oct 25 17:39:22 UTC 2017


On Tue, Oct 24, 2017 at 02:43:31PM -0700, William Tu wrote:

Hi William,
Thanks for taking a look at this.

> When using the out-of-tree (openvswitch compat) geneve module,
> the first time oot tunnel probing returns true (correct).
> Without unloading the geneve module, if the userspace ovs-vswitchd
> restarts, because the 'geneve_sys_6081' still exists, the probing
> incorrectly returns false and loads the in-tree (upstream kernel)
> geneve module.

The reason for this is because rtnl sees the existing device and tries
to call ->changelink, but since the out-of-tree tunnel has no handler it
returns EOPNOTSUPP.

> The patch fixes it by adding NLM_F_EXCL flags, so if geneve already
> exists, the dpif_netlink_rtnl_create return EEXIST and the oot tunnel
> probing returns true.  To reproduce the issue, start the ovs

While this fixes this scenario, it breaks another; an existing device
in-tree/kernel geneve tunnel. We'll end up with the opposite occurring -
it returns true when it should return false.

So in addition to adding NLM_F_EXCL, this needs to also try to delete
the existing device in the case of EEXISTS, then restart the probe.

> > /etc/init.d/openvswitch-switch start
> > creat a bridge and attach a geneve port using out-of-tree geneve
> > /etc/init.d/openvswitch-switch restart
> 
> Fixes: 921c370a9df5 ("dpif-netlink: Probe for out-of-tree tunnels, decides used interface")
> Signed-off-by: William Tu <u9012063 at gmail.com>
> Cc: Eric Garver <e at erig.me>
> Cc: Gurucharan Shetty <guru at ovn.org>
> ---
>  lib/dpif-netlink-rtnl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/dpif-netlink-rtnl.c b/lib/dpif-netlink-rtnl.c
> index 0c32e7d8ccb4..ab9737b8cc4b 100644
> --- a/lib/dpif-netlink-rtnl.c
> +++ b/lib/dpif-netlink-rtnl.c
> @@ -451,7 +451,7 @@ dpif_netlink_rtnl_probe_oot_tunnels(void)
>          error = dpif_netlink_rtnl_create(tnl_cfg, name, OVS_VPORT_TYPE_GENEVE,
>                                           "ovs_geneve",
>                                           (NLM_F_REQUEST | NLM_F_ACK
> -                                          | NLM_F_CREATE));
> +                                          | NLM_F_CREATE | NLM_F_EXCL));
>          if (error != EOPNOTSUPP) {
>              if (!error) {
>                  dpif_netlink_rtnl_destroy(name);
> -- 
> 2.7.4
> 
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