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

On 11.08.2023 20:42, Andrew Lunn wrote:

On Fri, Aug 11, 2023 at 06:32:48PM +0300, Radu Pirea (NXP OSS) wrote:

quoted

+	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.

quoted

+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.

quoted

+
+	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.