Steffen Klassert <steffen.klass...@secunet.com> wrote: > Cc Wei Wang > > On Sun, Feb 04, 2018 at 01:21:18PM +0200, Eyal Birger wrote: > > Hi, > > > > We've encountered a non released device reference upon device > > unregistration which seems to stem from xfrm policy code. > > > > The setup includes: > > - an underlay device (e.g. eth0) using IPv4 > > - an xfrm IPv6 over IPv4 tunnel routed via the underlay device > > - an ipip6 tunnel over the xfrm IPv6 tunnel > > > > When tearing down the underlay device, after traffic had passed via the > > ipip6 > > tunnel, log messages of the following form are observed: > > > > unregister_netdevice: waiting for eth0 to become free. Usage count = 2 > > Looks like this happened when the dst garbage collection code was > removed. I could not point to a commit that introduced it so I > did a bisection and this pointed to: > > commit 9514528d92d4cbe086499322370155ed69f5d06c > ipv6: call dst_dev_put() properly > > With this commit we leak the one refcount and some further commit > leaked the second one. > Subject: [PATCH RFC] xfrm: Fix netdev refcount leak when flushing the percpu > dst cache. > > The dst garbage collection code is removed, so we need to call > dst_dev_put() on cached dst entries before we release them. > Otherwise we leak the refcount to the netdev.
I don't think this is related to the xfrm pcpu cache at all. AFAIU any xfrm dst that gets cached in a tunnel dst cache will hold the device reference. Perhaps its best to add a device notifier to the tunnel code and put device refcount there. I'll try to come up with a patch *unless* I'm wrong and this is really just because of xfrm pcpu cache.
