[PATCH net 1/1] af_packet: Fix wrong timestamps in tcpdump

[PATCH net 1/1] af_packet: Fix wrong timestamps in tcpdump

[KhaiWenTan]

From: Vinicius Costa Gomes <vinicius.gomes@intel.com>

Since commit 97dc7cd92ac6 ("ptp: Support late timestamp determination"),
timestamps may need to be retrieved with input from the driver
.ndo_get_tstamp(). Support was missing from mmap'ed AF_PACKET sockets.

The problem was noticed using the igc driver, that since commit
069b142f5819 ("igc: Add support for PTP .getcyclesx64()") has migrated to
use .ndo_get_tstamp() that timestamps were wrong on the receiving side,
when using tcpdump.

Fixes: 069b142f5819 ("igc: Add support for PTP .getcyclesx64()")
Cc: stable@vger.kernel.org
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Signed-off-by: KhaiWenTan <khai.wen.tan@linux.intel.com>
---
 net/packet/af_packet.c | 29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index cf6429f09477..7197236c8a3b 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -456,15 +456,20 @@ static int __packet_get_status(const struct packet_sock *po, void *frame)
 	}
 }
 
-static __u32 tpacket_get_timestamp(struct sk_buff *skb, struct timespec64 *ts,
-				   unsigned int flags)
+static __u32 tpacket_get_timestamp(struct net_device *dev, struct sk_buff *skb,
+				   struct timespec64 *ts, unsigned int flags,
+				   unsigned int sk_tsflags)
 {
 	struct skb_shared_hwtstamps *shhwtstamps = skb_hwtstamps(skb);
 
-	if (shhwtstamps &&
-	    (flags & SOF_TIMESTAMPING_RAW_HARDWARE) &&
-	    ktime_to_timespec64_cond(shhwtstamps->hwtstamp, ts))
-		return TP_STATUS_TS_RAW_HARDWARE;
+	bool cycles = sk_tsflags & SOF_TIMESTAMPING_BIND_PHC;
+
+	if (shhwtstamps && shhwtstamps->hwtstamp &&
+	    (flags & SOF_TIMESTAMPING_RAW_HARDWARE)) {
+		ktime_t tstamp = netdev_get_tstamp(dev, shhwtstamps, cycles);
+
+		return ktime_to_timespec64_cond(tstamp, ts) ? TP_STATUS_TS_RAW_HARDWARE : 0;
+	}
 
 	if ((flags & SOF_TIMESTAMPING_SOFTWARE) &&
 	    ktime_to_timespec64_cond(skb_tstamp(skb), ts))
@@ -476,11 +481,16 @@ static __u32 tpacket_get_timestamp(struct sk_buff *skb, struct timespec64 *ts,
 static __u32 __packet_set_timestamp(struct packet_sock *po, void *frame,
 				    struct sk_buff *skb)
 {
+	struct net_device *dev = skb->dev;
+	unsigned int sk_tsflags;
 	union tpacket_uhdr h;
 	struct timespec64 ts;
 	__u32 ts_status;
 
-	if (!(ts_status = tpacket_get_timestamp(skb, &ts, READ_ONCE(po->tp_tstamp))))
+	sk_tsflags = READ_ONCE(po->sk.sk_tsflags);
+	ts_status = tpacket_get_timestamp(dev, skb, &ts, READ_ONCE(po->tp_tstamp), sk_tsflags);
+
+	if (!(ts_status))
 		return 0;
 
 	h.raw = frame;
@@ -2424,9 +2434,10 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
 	/* Always timestamp; prefer an existing software timestamp taken
 	 * closer to the time of capture.
 	 */
-	ts_status = tpacket_get_timestamp(skb, &ts,
+	ts_status = tpacket_get_timestamp(dev, skb, &ts,
 					  READ_ONCE(po->tp_tstamp) |
-					  SOF_TIMESTAMPING_SOFTWARE);
+					  SOF_TIMESTAMPING_SOFTWARE,
+					  READ_ONCE(sk->sk_tsflags));
 	if (!ts_status)
 		ktime_get_real_ts64(&ts);
 
-- 
2.34.1