Commit b3ca9eef authored by Gerhard Engleder's avatar Gerhard Engleder Committed by Jakub Kicinski
Browse files

tsnep: fix timestamping with a stacked DSA driver 



This driver is susceptible to a form of the bug explained in commit
c26a2c2d ("gianfar: Fix TX timestamping with a stacked DSA driver")
and in Documentation/networking/timestamping.rst section "Other caveats
for MAC drivers", specifically it timestamps any skb which has
SKBTX_HW_TSTAMP, and does not consider if timestamping has been enabled
in adapter->hwtstamp_config.tx_type.

Evaluate the proper TX timestamping condition only once on the TX
path (in tsnep_xmit_frame_ring()) and store the result in an additional
TX entry flag. Evaluate the new TX entry flag in the TX confirmation path
(in tsnep_tx_poll()).

This way SKBTX_IN_PROGRESS is set by the driver as required, but never
evaluated. SKBTX_IN_PROGRESS shall not be evaluated as it can be set
by a stacked DSA driver and evaluating it would lead to unwanted
timestamps.

Fixes: 403f69bb ("tsnep: Add TSN endpoint Ethernet MAC driver")
Suggested-by: default avatarVladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: default avatarGerhard Engleder <gerhard@engleder-embedded.com>
Reviewed-by: default avatarVladimir Oltean <vladimir.oltean@nxp.com>
Link: https://patch.msgid.link/20250514195657.25874-1-gerhard@engleder-embedded.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 491deb9b

drivers/net/ethernet/engleder/tsnep_main.c

+19 −11
Original line number Diff line number Diff line
@@ -67,6 +67,8 @@ 
#define TSNEP_TX_TYPE_XDP_NDO_MAP_PAGE	(TSNEP_TX_TYPE_XDP_NDO | TSNEP_TX_TYPE_MAP_PAGE)

#define TSNEP_TX_TYPE_XDP		(TSNEP_TX_TYPE_XDP_TX | TSNEP_TX_TYPE_XDP_NDO)

#define TSNEP_TX_TYPE_XSK		BIT(12)

#define TSNEP_TX_TYPE_TSTAMP		BIT(13)

#define TSNEP_TX_TYPE_SKB_TSTAMP	(TSNEP_TX_TYPE_SKB | TSNEP_TX_TYPE_TSTAMP)



#define TSNEP_XDP_TX		BIT(0)

#define TSNEP_XDP_REDIRECT	BIT(1)
@@ -386,8 +388,7 @@ static void tsnep_tx_activate(struct tsnep_tx *tx, int index, int length, 
	if (entry->skb) {

		entry->properties = length & TSNEP_DESC_LENGTH_MASK;

		entry->properties |= TSNEP_DESC_INTERRUPT_FLAG;

		if ((entry->type & TSNEP_TX_TYPE_SKB) &&

		    (skb_shinfo(entry->skb)->tx_flags & SKBTX_IN_PROGRESS))

		if ((entry->type & TSNEP_TX_TYPE_SKB_TSTAMP) == TSNEP_TX_TYPE_SKB_TSTAMP)

			entry->properties |= TSNEP_DESC_EXTENDED_WRITEBACK_FLAG;



		/* toggle user flag to prevent false acknowledge
@@ -479,7 +480,8 @@ static int tsnep_tx_map_frag(skb_frag_t *frag, struct tsnep_tx_entry *entry, 
	return mapped;

}



static int tsnep_tx_map(struct sk_buff *skb, struct tsnep_tx *tx, int count)

static int tsnep_tx_map(struct sk_buff *skb, struct tsnep_tx *tx, int count,

			bool do_tstamp)

{

	struct device *dmadev = tx->adapter->dmadev;

	struct tsnep_tx_entry *entry;
@@ -505,6 +507,9 @@ static int tsnep_tx_map(struct sk_buff *skb, struct tsnep_tx *tx, int count) 
				entry->type = TSNEP_TX_TYPE_SKB_INLINE;

				mapped = 0;

			}



			if (do_tstamp)

				entry->type |= TSNEP_TX_TYPE_TSTAMP;

		} else {

			skb_frag_t *frag = &skb_shinfo(skb)->frags[i - 1];
@@ -558,11 +563,12 @@ static int tsnep_tx_unmap(struct tsnep_tx *tx, int index, int count) 
static netdev_tx_t tsnep_xmit_frame_ring(struct sk_buff *skb,

					 struct tsnep_tx *tx)

{

	int count = 1;

	struct tsnep_tx_entry *entry;

	bool do_tstamp = false;

	int count = 1;

	int length;

	int i;

	int retval;

	int i;



	if (skb_shinfo(skb)->nr_frags > 0)

		count += skb_shinfo(skb)->nr_frags;
@@ -579,7 +585,13 @@ static netdev_tx_t tsnep_xmit_frame_ring(struct sk_buff *skb, 
	entry = &tx->entry[tx->write];

	entry->skb = skb;



	retval = tsnep_tx_map(skb, tx, count);

	if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP) &&

	    tx->adapter->hwtstamp_config.tx_type == HWTSTAMP_TX_ON) {

		skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;

		do_tstamp = true;

	}



	retval = tsnep_tx_map(skb, tx, count, do_tstamp);

	if (retval < 0) {

		tsnep_tx_unmap(tx, tx->write, count);

		dev_kfree_skb_any(entry->skb);
@@ -591,9 +603,6 @@ static netdev_tx_t tsnep_xmit_frame_ring(struct sk_buff *skb, 
	}

	length = retval;



	if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP)

		skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;



	for (i = 0; i < count; i++)

		tsnep_tx_activate(tx, (tx->write + i) & TSNEP_RING_MASK, length,

				  i == count - 1);
@@ -844,8 +853,7 @@ static bool tsnep_tx_poll(struct tsnep_tx *tx, int napi_budget) 


		length = tsnep_tx_unmap(tx, tx->read, count);



		if ((entry->type & TSNEP_TX_TYPE_SKB) &&

		    (skb_shinfo(entry->skb)->tx_flags & SKBTX_IN_PROGRESS) &&

		if (((entry->type & TSNEP_TX_TYPE_SKB_TSTAMP) == TSNEP_TX_TYPE_SKB_TSTAMP) &&

		    (__le32_to_cpu(entry->desc_wb->properties) &

		     TSNEP_DESC_EXTENDED_WRITEBACK_FLAG)) {

			struct skb_shared_hwtstamps hwtstamps;