Re: [RFC net-next v1 4/5] net: macsec: introduce mdo_insert_tx_tag

[Radu Pirea (OSS)]

On 11.08.2023 20:42, Andrew Lunn wrote:
> On Fri, Aug 11, 2023 at 06:32:48PM +0300, Radu Pirea (NXP OSS) wrote:
>
> > +	if (macsec->offload == MACSEC_OFFLOAD_OFF) {
> > +		dev->needed_headroom -= ops->needed_headroom;
> > +		dev->needed_headroom += MACSEC_NEEDED_HEADROOM;
> > +		dev->needed_tailroom -= ops->needed_tailroom;
> > +		dev->needed_tailroom += MACSEC_NEEDED_TAILROOM;
> > +	} else {
> > +		dev->needed_headroom -= MACSEC_NEEDED_HEADROOM;
> > +		dev->needed_headroom += ops->needed_headroom;
> > +		dev->needed_tailroom -= MACSEC_NEEDED_TAILROOM;
> > +		dev->needed_tailroom += ops->needed_tailroom;
> > +	}
>
> It is not obvious to me what this is doing. Should this actually be in
> macsec_dev_init()? My main problem is why there is an else condition?

The user can enable/disable offloading after the interface is created, 
that's why the else condition is needed.

> > +static struct sk_buff *insert_tx_tag(struct sk_buff *skb,
> > +				     struct net_device *dev)
> > +{
> > +	struct macsec_dev *macsec = macsec_priv(dev);
> > +	const struct macsec_ops *ops;
> > +	struct macsec_context ctx;
> > +	int err;
> > +
> > +	if (!macsec_is_offloaded(macsec))
> > +		return ERR_PTR(-EINVAL);
>
> Hasn't this already been checked in macsec_start_xmit()
Yes. This check is useless.

> > +
> > +	ops = macsec_get_ops(macsec, &ctx);
> > +	if (!ops)
> > +		return ERR_PTR(-EINVAL);
> > +
> > +	if (!ops->mdo_insert_tx_tag)
> > +		return skb;
>
> You are in the hot path here. You don't expect this to change from
> frame to frame. So could you evaluate this once and store it
> somewhere? Maybe in macsec_dev ?

The macsec_dev struct seems to be the right place.

> 	Andrew

--
Radu P.