Subject: Re: [PATCH net-next 1/3] net: Do not unconditionally turn on carrier when clearing protodown

From: Ido Schimmel <[email-masked]>
Date: Sun, 3 May 2026 21:08:03 +0300

On Fri, May 01, 2026 at 06:08:43PM -0700, Jakub Kicinski wrote:
> On Wed, 29 Apr 2026 15:46:22 +0300 Ido Schimmel wrote:
> > Solve this by adding a new NDO that allows different drivers to react
> > differently to protodown being cleared. Change the core to invoke the
> > NDO and implement it for vxlan and macvlan. Maintain the current
> > behavior for the former, but for macvlan implement the NDO by
> > transferring the operational state from its lower device.
> 
> Maybe just me but an NDO for this seems like an overkill.
> Isn't our range of options for the callback either follow
> lower or carrier on? Do you expect more complex logic?

Thanks for reviewing. I don't expect more complex logic, but resolving
the linked device via the driver is more straightforward (unless I'm
missing something).

There are drivers that only implement ndo_get_iflink(), but don't
implement get_link_net(), so it's unclear in which netns we need to look
up the device using the ifindex we got from ndo_get_iflink(). Netdevsim
is one example. There are also some drivers that only implement
get_link_net() such as vxlan.

The popular drivers such as vlan, macvlan and veth obviously implement
both.

I added a helper [1] that resolves the linked device if these operations
are present and otherwise returns the device itself. Similar to
dev_get_iflink() which only gives us the ifindex.

Another option is to add a new NDO that gives us a pointer to the linked
device.

[1] https://github.com/idosch/linux/commit/34c57bceb1a7e52da0f973914f8a4dd08b7f9072.patch