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

["Radu Pirea (OSS)" <radu-nicolae.pirea@oss.nxp.com>]

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.