[RFC PATCH 08/10] net: dsa: forward timestamping callbacks to switch drivers

[Andrew Lunn <andrew@lunn.ch>]

From: Brandon Streiff <brandon.streiff@ni.com>

Forward the rx/tx timestamp machinery from the dsa infrastructure to the
switch driver.

On the rx side, defer delivery of skbs until we have an rx timestamp.
This mimicks the behavior of skb_defer_rx_timestamp.

On the tx side, identify PTP packets, clone them, and pass them to the
underlying switch driver before we transmit. This mimicks the behavior
of skb_tx_timestamp.

Adjusted txstamp API to keep the allocation and freeing of the clone
in the same central function by Richard Cochran

Signed-off-by: Brandon Streiff <brandon.streiff@ni.com>
Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
---
 include/net/dsa.h |  5 +++++
 net/dsa/dsa.c     | 36 ++++++++++++++++++++++++++++++++++++
 net/dsa/slave.c   | 30 ++++++++++++++++++++++++++++++
 3 files changed, 71 insertions(+)

diff --git a/include/net/dsa.h b/include/net/dsa.h
index 4c0df83dddaf..0ad17b63684d 100644
--- a/include/net/dsa.h
+++ b/include/net/dsa.h
@@ -102,6 +102,7 @@ struct dsa_platform_data {
 };
 
 struct packet_type;
+struct dsa_switch;
 
 struct dsa_device_ops {
 	struct sk_buff *(*xmit)(struct sk_buff *skb, struct net_device *dev);
@@ -484,6 +485,10 @@ struct dsa_switch_ops {
 				     struct ifreq *ifr);
 	int	(*port_hwtstamp_set)(struct dsa_switch *ds, int port,
 				     struct ifreq *ifr);
+	bool	(*port_txtstamp)(struct dsa_switch *ds, int port,
+				 struct sk_buff *clone, unsigned int type);
+	bool	(*port_rxtstamp)(struct dsa_switch *ds, int port,
+				 struct sk_buff *skb, unsigned int type);
 };
 
 struct dsa_switch_driver {
diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
index 6a9d0f50fbee..e63c554e0623 100644
--- a/net/dsa/dsa.c
+++ b/net/dsa/dsa.c
@@ -23,6 +23,7 @@
 #include <linux/netdevice.h>
 #include <linux/sysfs.h>
 #include <linux/phy_fixed.h>
+#include <linux/ptp_classify.h>
 #include <linux/gpio/consumer.h>
 #include <linux/etherdevice.h>
 
@@ -122,6 +123,38 @@ struct net_device *dsa_dev_to_net_device(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(dsa_dev_to_net_device);
 
+/* Determine if we should defer delivery of skb until we have a rx timestamp.
+ *
+ * Called from dsa_switch_rcv. For now, this will only work if tagging is
+ * enabled on the switch. Normally the MAC driver would retrieve the hardware
+ * timestamp when it reads the packet out of the hardware. However in a DSA
+ * switch, the DSA driver owning the interface to which the packet is
+ * delivered is never notified unless we do so here.
+ */
+static bool dsa_skb_defer_rx_timestamp(struct dsa_slave_priv *p,
+				       struct sk_buff *skb)
+{
+	struct dsa_switch *ds = p->dp->ds;
+	unsigned int type;
+
+	if (skb_headroom(skb) < ETH_HLEN)
+		return false;
+
+	__skb_push(skb, ETH_HLEN);
+
+	type = ptp_classify_raw(skb);
+
+	__skb_pull(skb, ETH_HLEN);
+
+	if (type == PTP_CLASS_NONE)
+		return false;
+
+	if (likely(ds->ops->port_rxtstamp))
+		return ds->ops->port_rxtstamp(ds, p->dp->index, skb, type);
+
+	return false;
+}
+
 static int dsa_switch_rcv(struct sk_buff *skb, struct net_device *dev,
 			  struct packet_type *pt, struct net_device *unused)
 {
@@ -157,6 +190,9 @@ static int dsa_switch_rcv(struct sk_buff *skb, struct net_device *dev,
 	s->rx_bytes += skb->len;
 	u64_stats_update_end(&s->syncp);
 
+	if (dsa_skb_defer_rx_timestamp(p, skb))
+		return 0;
+
 	netif_receive_skb(skb);
 
 	return 0;
diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index 935d93f0d36c..3376dad6dcfd 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -21,6 +21,7 @@
 #include <net/tc_act/tc_mirred.h>
 #include <linux/if_bridge.h>
 #include <linux/netpoll.h>
+#include <linux/ptp_classify.h>
 
 #include "dsa_priv.h"
 
@@ -401,6 +402,30 @@ static inline netdev_tx_t dsa_slave_netpoll_send_skb(struct net_device *dev,
 	return NETDEV_TX_OK;
 }
 
+static void dsa_skb_tx_timestamp(struct dsa_slave_priv *p,
+				 struct sk_buff *skb)
+{
+	struct dsa_switch *ds = p->dp->ds;
+	struct sk_buff *clone;
+	unsigned int type;
+
+	type = ptp_classify_raw(skb);
+	if (type == PTP_CLASS_NONE)
+		return;
+
+	if (!ds->ops->port_txtstamp)
+		return;
+
+	clone = skb_clone_sk(skb);
+	if (!clone)
+		return;
+
+	if (ds->ops->port_txtstamp(ds, p->dp->index, clone, type))
+		return;
+
+	kfree_skb(clone);
+}
+
 static netdev_tx_t dsa_slave_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct dsa_slave_priv *p = netdev_priv(dev);
@@ -413,6 +438,11 @@ static netdev_tx_t dsa_slave_xmit(struct sk_buff *skb, struct net_device *dev)
 	s->tx_bytes += skb->len;
 	u64_stats_update_end(&s->syncp);
 
+	/* Identify PTP protocol packets, clone them, and pass them to the
+	 * switch driver
+	 */
+	dsa_skb_tx_timestamp(p, skb);
+
 	/* Transmit function may have to reallocate the original SKB,
 	 * in which case it must have freed it. Only free it here on error.
 	 */
-- 
2.15.1