Re: VRF/IPv4/ARP: unregister_netdevice waiting for dev to become free -> Who's responsible for releasing dst_entry created by ip_route_input_noref?

On 6/5/21 11:16 AM, Oliver Herms wrote:

Processing the incoming ARP request causes a call to ip_route_input_noref => ip_route_input_rcu => ip_route_input_slow => rt_dst_alloc => dst_alloc => dev_hold.
In a non VRF use-case the dst->dev would be the loopback interface that is never deleted. In the VRF use-case dst->dev is the VRF interface. And that one I would like to delete.

I've tracked down that dst_release() would call dev_put() but it seems dst_release is not called here (but should be I guess?). Thus, causing a dst_entry leak that causes the VRF device to be unremovable.
At least that's what it looks like to me.

I see what the problem is -- rtable is on cached on the l3mdev port
device. I have an idea how to fix it; I will send a patch within a few
days. Thanks for the detailed analysis and report.