Re: [PATCH net-next 0/3] net: introduce IFF_PROTO_DOWN flag.

On Fri, Mar 20, 2015 at 8:11 AM,  [off-list ref] wrote:

From: Anuradha Karuppiah <redacted>

Applications can detect errors in the network that would require
disabling the device independent of the admin state. In the presence of
these errors traffic could be black holed or looped resulting in a
network meltdown. Clearing the IFF_UP flag for error disabling the
device can be problematic because -

1. The administrator cannot distinguish between a user space daemon’s
error-disable and a regular device disable.
2. Applications can monitor the error state and enable the device once
the error is removed. If IFF_UP is used for this purpose the application
may end up enabling a device that the administrator has intentionally
disabled for other reasons. This could result in network changes not
expected by the admin.

Both reasons look like workaround for user space issues.
Just keep this fake-down state in userspace.
What's the point pushing it to kernel?
looking at 3rd patch:
+ * @IF_LINK_PROTO_DOWN_MLAG: proto_down by a multi-chassis LAG application.
+ * @IF_LINK_PROTO_DOWN_STP: proto_down by an STP application.

so there will be new flag for every application that cannot deal with
normal down?