Re: [PATCH net-next RFC 6/9] net: dsa: forward timestamping callbacks to switch drivers

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. The implementation
does have to thread through the tagging protocol handlers because
it is where that we know which switch and port the skb goes to.

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.

Signed-off-by: Brandon Streiff <redacted>
---
 include/net/dsa.h     | 13 +++++++++++--
 net/dsa/dsa.c         | 39 ++++++++++++++++++++++++++++++++++++++-
 net/dsa/slave.c       | 25 +++++++++++++++++++++++++
 net/dsa/tag_brcm.c    |  6 +++++-
 net/dsa/tag_dsa.c     |  6 +++++-
 net/dsa/tag_edsa.c    |  6 +++++-
 net/dsa/tag_ksz.c     |  6 +++++-
 net/dsa/tag_lan9303.c |  6 +++++-
 net/dsa/tag_mtk.c     |  6 +++++-
 net/dsa/tag_qca.c     |  6 +++++-
 net/dsa/tag_trailer.c |  6 +++++-
 11 files changed, 114 insertions(+), 11 deletions(-)

diff --git a/include/net/dsa.h b/include/net/dsa.h
index 1163af1..4daf7f7 100644
--- a/include/net/dsa.h
+++ b/include/net/dsa.h

@@ -101,11 +101,14 @@ 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);
 	struct sk_buff *(*rcv)(struct sk_buff *skb, struct net_device *dev,
-			       struct packet_type *pt);
+			       struct packet_type *pt,
+			       struct dsa_switch **src_dev,
+			       int *src_port);
 	int (*flow_dissect)(const struct sk_buff *skb, __be16 *proto,
 			    int *offset);
 };

@@ -134,7 +137,9 @@ struct dsa_switch_tree {
 	/* Copy of tag_ops->rcv for faster access in hot path */
 	struct sk_buff *	(*rcv)(struct sk_buff *skb,
 				       struct net_device *dev,
-				       struct packet_type *pt);
+				       struct packet_type *pt,
+				       struct dsa_switch **src_dev,
+				       int *src_port);
 
 	/*
 	 * The switch port to which the CPU is attached.

@@ -449,6 +454,10 @@ struct dsa_switch_ops {
 				     struct ifreq *ifr);
 	int	(*port_hwtstamp_set)(struct dsa_switch *ds, int port,
 				     struct ifreq *ifr);
+	void	(*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 81c852e..42e7286 100644
--- a/net/dsa/dsa.c
+++ b/net/dsa/dsa.c

@@ -22,6 +22,7 @@
 #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>
 

@@ -157,6 +158,37 @@ 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_switch *ds, int port,
+				       struct sk_buff *skb)

+
 static int dsa_switch_rcv(struct sk_buff *skb, struct net_device *dev,
 			  struct packet_type *pt, struct net_device *unused)
 {

@@ -164,6 +196,8 @@ static int dsa_switch_rcv(struct sk_buff *skb, struct net_device *dev,
 	struct sk_buff *nskb = NULL;
 	struct pcpu_sw_netstats *s;
 	struct dsa_slave_priv *p;
+	struct dsa_switch *ds = NULL;
+	int source_port;
 
 	if (unlikely(dst == NULL)) {
 		kfree_skb(skb);

@@ -174,7 +208,7 @@ static int dsa_switch_rcv(struct sk_buff *skb, struct net_device *dev,
 	if (!skb)
 		return 0;
 
-	nskb = dst->rcv(skb, dev, pt);
+	nskb = dst->rcv(skb, dev, pt, &ds, &source_port);

 	if (!nskb) {
 		kfree_skb(skb);
 		return 0;

@@ -192,6 +226,9 @@ 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(ds, source_port, skb))
+		return 0;

+
 	netif_receive_skb(skb);
 
 	return 0;

diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index 2cf6a83..a278335 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c

@@ -22,6 +22,7 @@
 #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"
 

@@ -407,6 +408,25 @@ 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;