Re: [PATCH net-next v4 04/10] tsnep: Add adapter down state

On 10.01.23 17:05, Alexander H Duyck wrote:

On Mon, 2023-01-09 at 20:15 +0100, Gerhard Engleder wrote:

quoted

Add adapter state with flag for down state. This flag will be used by
the XDP TX path to deny TX if adapter is down.

Signed-off-by: Gerhard Engleder <redacted>

What value is this bit adding?

 From what I can tell you could probably just use netif_carrier_ok in
place of this and actually get better coverage in terms of identifying
state in which the Tx queue is able to function. So in your XDP_TX
patch you could do that if you really need it.

TX does not check the link state, because the hardware just drops all
packets if there is no link. I would like to keep it like that, because
it minimizes special behavior if the link is down. netif_carrier_ok()
would include the link state.

As far as the use in your close function it is redundant since the
IFF_UP is only set if ndo_open completes, and ndo_stop is only called
if IFF_UP is set. So your down flag would be redundant with !IFF_UP in
that case.

tsnep_netdev_close() is called directly during bpf prog setup (see last
commit). If the following tsnep_netdev_open() call fails, then this
flag signals that the device is actually down even if IFF_UP is set. So
in this case the down flag is not redundant to !IFF_UP.

Is this a good enough reason for the flag?

Gerhard