On 3/29/17 11:05 AM, Vlad Yasevich wrote:

On 03/29/2017 12:37 PM, Roopa Prabhu wrote:

quoted

On 3/29/17, 5:23 AM, Vlad Yasevich wrote:

quoted

[ resending to list.  hit the wrong reply button last time ]

On 03/27/2017 06:58 PM, David Miller wrote:

quoted

From: Vladislav Yasevich <redacted>
Date: Sat, 25 Mar 2017 21:59:47 -0400

quoted

RTNL currently generates notifications on some netdev notifier events.
However, user space has no idea what changed.  All it sees is the
data and has to infer what has changed.  For some events that is not
possible.

This patch adds a new field to RTM_NEWLINK message called IFLA_EVENT
that would have an encoding of the which event triggered this
notification.  Currectly, only 2 events (NETDEV_NOTIFY_PEERS and
NETDEV_MTUCHANGED) are supported.  These events could be interesting
in the virt space to trigger additional configuration commands to VMs.
Other events of interest may be added later.

Signed-off-by: Vladislav Yasevich <redacted>

At what point do we start providing the metadata for the changed
values as well?  You'd probably need to provide both the old and
new values to cover all cases.

I don't think if that would be possible because of when events are triggered.
We send these notifications after all the changes have already been made, so
it might be tough to carry old data.

Looking at just the two events I am supporting in this patch, we could actually
supply the old mtu data through a NETDEV_PRECHANGEMTU event, if it is necessary.

But, NETDEV_PRECHANGEMTU will be a unnecessary notification to userspace without
changes. There are already enough notifications generated for links (I know you are not
suggesting adding it here)

Actually, this one already triggers a link notification to userspace.  It just has
no event data in it to tell you that. :)

Is it intentional or unintentional? perhaps rtnetlink_event should be a
whitelist -- events that userspace should be notified about. Seems like
NETDEV_ events have been added without rtnetlink_event getting updated.
For example, does userspace care about NETDEV_UDP_TUNNEL_PUSH_INFO or
NETDEV_CHANGE_TX_QUEUE_LEN?