Re: [PATCH 0/2] net: add USB CDC Ethernet NCSI support and fix unregister UAF

[Andrew Lunn <andrew@lunn.ch>]

On Mon, Sep 07, 2026 at 08:15:54PM +0800, Potin Lai wrote:
> This series introduces NCSI (Network Controller Sideband Interface)
> passthrough support for USB CDC Ethernet devices and fixes a
> use-after-free race condition in the NCSI core unregistration path.
> 
> In DPU (Data Processing Unit) platforms such as the NVIDIA BlueField
> series, the Baseboard Management Controller (BMC) communicates with the
> host or DPU via a dedicated USB CDC Ethernet connection for out-of-band
> management traffic.

I'm confused with the architecture here. What normally happens is the
BMC has a standard Ethernet interface which outputs RGMII. That goes
into what is in effect a little 3 port switch in the host
interface. That switch allows packets to flow to the host, to the BMC,
or out the PHY to the medium.

Because the PHY is in effect being shared by two interfaces,
management of that PHY becomes "Interesting". You don't want either of
the interfaces setting the PHY down because it would cut the other off
from the medium.

What is the architecture then USB is used?

     Andrew