net: dsa: Keep a pointer to the skb clone for TX timestamping

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>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index 5bab82d46f0cfae6f1f8c3584d9766bf759ce595..289a6aa4b51c8a32939645100e5ebd196c50fc2e 100644 (file)
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -423,6 +423,8 @@ 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;
 
@@ -460,6 +462,7 @@ 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