[PATCH 5.10 199/252] net: packetmmap: fix only tx timestamp on request

[Greg Kroah-Hartman]

From: Richard Sanger <rsanger@xxxxxxxxxxx>

[ Upstream commit 171c3b151118a2fe0fc1e2a9d1b5a1570cfe82d2 ]

The packetmmap tx ring should only return timestamps if requested via
setsockopt PACKET_TIMESTAMP, as documented. This allows compatibility
with non-timestamp aware user-space code which checks
tp_status == TP_STATUS_AVAILABLE; not expecting additional timestamp
flags to be set in tp_status.

Fixes: b9c32fb27170 ("packet: if hw/sw ts enabled in rx/tx ring, report which ts we got")
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: Willem de Bruijn <willemdebruijn.kernel@xxxxxxxxx>
Signed-off-by: Richard Sanger <rsanger@xxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/packet/af_packet.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 449625c2ccc7..ddb68aa836f7 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -421,7 +421,8 @@ static __u32 tpacket_get_timestamp(struct sk_buff *skb, struct timespec64 *ts,
 	    ktime_to_timespec64_cond(shhwtstamps->hwtstamp, ts))
 		return TP_STATUS_TS_RAW_HARDWARE;
 
-	if (ktime_to_timespec64_cond(skb->tstamp, ts))
+	if ((flags & SOF_TIMESTAMPING_SOFTWARE) &&
+	    ktime_to_timespec64_cond(skb->tstamp, ts))
 		return TP_STATUS_TS_SOFTWARE;
 
 	return 0;
@@ -2339,7 +2340,12 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
 
 	skb_copy_bits(skb, 0, h.raw + macoff, snaplen);
 
-	if (!(ts_status = tpacket_get_timestamp(skb, &ts, po->tp_tstamp)))
+	/* Always timestamp; prefer an existing software timestamp taken
+	 * closer to the time of capture.
+	 */
+	ts_status = tpacket_get_timestamp(skb, &ts,
+					  po->tp_tstamp | SOF_TIMESTAMPING_SOFTWARE);
+	if (!ts_status)
 		ktime_get_real_ts64(&ts);
 
 	status |= ts_status;
-- 
2.30.2