From: Daniel Phillips <redacted>
Date: Sun, 13 Aug 2006 14:22:31 -0700

David Miller wrote:

quoted

The reason is that there is no refcounting performed on these devices
when they are attached to the skb, for performance reasons, and thus
the device can be downed, the module for it removed, etc. long before
the skb is freed up.

The virtual block device can refcount the network device on virtual
device create and un-refcount on virtual device delete.

What if the packet is originally received on the device in question,
and then gets redirected to another device by a packet scheduler
traffic classifier action or a netfilter rule?

It is necessary to handle the case where the device changes on the
skb, and the skb gets freed up in a context and assosciation different
from when the skb was allocated (for example, different from the
device attached to the virtual block device).