Re: [RFC PATCH net-next 2/5] net: dsa: propagate flags down towards drivers

[Vladimir Oltean <olteanv@gmail.com>]

On Tue, Jan 17, 2023 at 07:57:11PM +0100, Hans J. Schultz wrote:
> Dynamic FDB flag needs to be propagated through the DSA layer to be
> added to drivers.
> Use a u16 for fdb flags for future use, so that other flags can also be
> sent the same way without having to change function interfaces.
> 
> Signed-off-by: Hans J. Schultz <netdev@kapio-technology.com>
> ---
> @@ -3364,6 +3368,7 @@ static int dsa_slave_fdb_event(struct net_device *dev,
>  	struct dsa_port *dp = dsa_slave_to_port(dev);
>  	bool host_addr = fdb_info->is_local;
>  	struct dsa_switch *ds = dp->ds;
> +	u16 fdb_flags = 0;
>  
>  	if (ctx && ctx != dp)
>  		return 0;
> @@ -3410,6 +3415,9 @@ static int dsa_slave_fdb_event(struct net_device *dev,
>  		   orig_dev->name, fdb_info->addr, fdb_info->vid,
>  		   host_addr ? " as host address" : "");
>  
> +	if (fdb_info->is_dyn)
> +		fdb_flags |= DSA_FDB_FLAG_DYNAMIC;
> +

Hmm, I don't think this is going to work with the assisted_learning_on_cpu_port
feature ("if (switchdev_fdb_is_dynamically_learned(fdb_info))"). The reason being
that a "dynamically learned" FDB entry (defined as this):

static inline bool
switchdev_fdb_is_dynamically_learned(const struct switchdev_notifier_fdb_info *fdb_info)
{
	return !fdb_info->added_by_user && !fdb_info->is_local;
}

is also dynamic in the DSA_FDB_FLAG_DYNAMIC sense. But we install a
static FDB entry for it on the CPU port.

And in your follow-up patch 3/5, you make all drivers except mv88e6xxx
ignore all DSA_FDB_FLAG_DYNAMIC entries (including the ones snooped from
address learning on software interfaces). So this breaks those drivers
which don't implement DSA_FDB_FLAG_DYNAMIC but do set ds->assisted_learning_on_cpu_port
to true.

I think you also want to look at the added_by_user flag to disambiguate
between a dynamic FDB entry added from learning (which it's ok to
offload as static, because software ageing will remove it) and one added
by the user.

>  	INIT_WORK(&switchdev_work->work, dsa_slave_switchdev_event_work);
>  	switchdev_work->event = event;
>  	switchdev_work->dev = dev;
> @@ -3418,6 +3426,7 @@ static int dsa_slave_fdb_event(struct net_device *dev,
>  	ether_addr_copy(switchdev_work->addr, fdb_info->addr);
>  	switchdev_work->vid = fdb_info->vid;
>  	switchdev_work->host_addr = host_addr;
> +	switchdev_work->fdb_flags = fdb_flags;
>  
>  	dsa_schedule_work(&switchdev_work->work);
>