netdev - Bridge port userspace events broken?

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Message-ID: <CAFLxGvwnOi6dSq5yLM78XskweQOY6aPbRt==G9wv5qS+dfj8bw@mail.gmail.com>
Date:   Mon, 14 Oct 2019 22:33:22 +0200
From:   Richard Weinberger <richard.weinberger@...il.com>
To:     netdev@...r.kernel.org
Cc:     Roopa Prabhu <roopa@...ulusnetworks.com>,
        nikolay@...ulusnetworks.com, bridge@...ts.linux-foundation.org,
        Greg KH <gregkh@...uxfoundation.org>
Subject: Bridge port userspace events broken?

Hi!

My userspace needs /sys/class/net/eth0/brport/group_fwd_mask, so I set
up udev rules
to wait for the sysfs file.
Without luck.
Also "udevadm monitor" does not show any event related to
/sys/class/net/eth0/brport when I assign eth0 to a bridge.

First I thought that the bridge code just misses to emit some events but
br_add_if() calls kobject_uevent() which is good.

Greg gave me the hint that the bridge code might not use the kobject model
correctly.

Enabling kobjekt debugging shows that all events are dropped:
[   36.904602] device eth0 entered promiscuous mode
[   36.904786] kobject: 'brport' (0000000028a47e33): kobject_uevent_env
[   36.904789] kobject: 'brport' (0000000028a47e33):
kobject_uevent_env: filter function caused the event to drop!

If I understood Greg correctly this is because the bridge code uses
plain kobjects which
have a parent object. Therefore all events are dropped.

Shouldn't brport be a kset just like net_device->queues_kset?

-- 
Thanks,
//richard