[PATCH v2 net-next 01/10] net: dsa: Keep a pointer to the skb clone for TX timestamping

[Vladimir Oltean <olteanv@gmail.com>]

For drivers that use deferred_xmit for PTP frames (such as sja1105),
there is no need to perform matching between PTP frames and their egress
timestamps, since the sending process can be serialized.

In that case, it makes sense to have the pointer to the skb clone that
DSA made directly in the skb->cb. It will be used for pushing the egress
timestamp back in the application socket's error queue.

Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
---
Changes in v2:

Patch is new. Forgot to send in v1.

 net/dsa/slave.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index 1e2ae9d59b88..59d7c9e0270f 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -427,6 +427,8 @@ static void dsa_skb_tx_timestamp(struct dsa_slave_priv *p,
 	if (!clone)
 		return;
 
+	DSA_SKB_CB(skb)->clone = clone;
+
 	if (ds->ops->port_txtstamp(ds, p->dp->index, clone, type))
 		return;
 
@@ -464,6 +466,7 @@ static netdev_tx_t dsa_slave_xmit(struct sk_buff *skb, struct net_device *dev)
 	u64_stats_update_end(&s->syncp);
 
 	DSA_SKB_CB(skb)->deferred_xmit = false;
+	DSA_SKB_CB(skb)->clone = NULL;
 
 	/* Identify PTP protocol packets, clone them, and pass them to the
 	 * switch driver
-- 
2.17.1