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From: Vedang Patel <vedang.patel@intel.com>
To: netdev@vger.kernel.org
Cc: jeffrey.t.kirsher@intel.com, davem@davemloft.net,
	jhs@mojatatu.com, xiyou.wangcong@gmail.com, jiri@resnulli.us,
	intel-wired-lan@lists.osuosl.org, vinicius.gomes@intel.com,
	l@dorileo.org, jakub.kicinski@netronome.com, m-karicheri2@ti.com,
	sergei.shtylyov@cogentembedded.com, eric.dumazet@gmail.com,
	aaron.f.brown@intel.com, Vedang Patel <vedang.patel@intel.com>
Subject: [PATCH net-next v5 1/7] igb: clear out skb->tstamp after reading the txtime
Date: Fri, 21 Jun 2019 10:28:22 -0700	[thread overview]
Message-ID: <1561138108-12943-2-git-send-email-vedang.patel@intel.com> (raw)
In-Reply-To: <1561138108-12943-1-git-send-email-vedang.patel@intel.com>

If a packet which is utilizing the launchtime feature (via SO_TXTIME socket
option) also requests the hardware transmit timestamp, the hardware
timestamp is not delivered to the userspace. This is because the value in
skb->tstamp is mistaken as the software timestamp.

Applications, like ptp4l, request a hardware timestamp by setting the
SOF_TIMESTAMPING_TX_HARDWARE socket option. Whenever a new timestamp is
detected by the driver (this work is done in igb_ptp_tx_work() which calls
igb_ptp_tx_hwtstamps() in igb_ptp.c[1]), it will queue the timestamp in the
ERR_QUEUE for the userspace to read. When the userspace is ready, it will
issue a recvmsg() call to collect this timestamp.  The problem is in this
recvmsg() call. If the skb->tstamp is not cleared out, it will be
interpreted as a software timestamp and the hardware tx timestamp will not
be successfully sent to the userspace. Look at skb_is_swtx_tstamp() and the
callee function __sock_recv_timestamp() in net/socket.c for more details.

Signed-off-by: Vedang Patel <vedang.patel@intel.com>
---
 drivers/net/ethernet/intel/igb/igb_main.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index fc925adbd9fa..f66dae72fe37 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -5688,6 +5688,7 @@ static void igb_tx_ctxtdesc(struct igb_ring *tx_ring,
 	 */
 	if (tx_ring->launchtime_enable) {
 		ts = ns_to_timespec64(first->skb->tstamp);
+		first->skb->tstamp = 0;
 		context_desc->seqnum_seed = cpu_to_le32(ts.tv_nsec / 32);
 	} else {
 		context_desc->seqnum_seed = 0;
-- 
2.7.3


WARNING: multiple messages have this Message-ID (diff)
From: Vedang Patel <vedang.patel@intel.com>
To: intel-wired-lan@osuosl.org
Subject: [Intel-wired-lan] [PATCH net-next v5 1/7] igb: clear out skb->tstamp after reading the txtime
Date: Fri, 21 Jun 2019 10:28:22 -0700	[thread overview]
Message-ID: <1561138108-12943-2-git-send-email-vedang.patel@intel.com> (raw)
In-Reply-To: <1561138108-12943-1-git-send-email-vedang.patel@intel.com>

If a packet which is utilizing the launchtime feature (via SO_TXTIME socket
option) also requests the hardware transmit timestamp, the hardware
timestamp is not delivered to the userspace. This is because the value in
skb->tstamp is mistaken as the software timestamp.

Applications, like ptp4l, request a hardware timestamp by setting the
SOF_TIMESTAMPING_TX_HARDWARE socket option. Whenever a new timestamp is
detected by the driver (this work is done in igb_ptp_tx_work() which calls
igb_ptp_tx_hwtstamps() in igb_ptp.c[1]), it will queue the timestamp in the
ERR_QUEUE for the userspace to read. When the userspace is ready, it will
issue a recvmsg() call to collect this timestamp.  The problem is in this
recvmsg() call. If the skb->tstamp is not cleared out, it will be
interpreted as a software timestamp and the hardware tx timestamp will not
be successfully sent to the userspace. Look at skb_is_swtx_tstamp() and the
callee function __sock_recv_timestamp() in net/socket.c for more details.

Signed-off-by: Vedang Patel <vedang.patel@intel.com>
---
 drivers/net/ethernet/intel/igb/igb_main.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index fc925adbd9fa..f66dae72fe37 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -5688,6 +5688,7 @@ static void igb_tx_ctxtdesc(struct igb_ring *tx_ring,
 	 */
 	if (tx_ring->launchtime_enable) {
 		ts = ns_to_timespec64(first->skb->tstamp);
+		first->skb->tstamp = 0;
 		context_desc->seqnum_seed = cpu_to_le32(ts.tv_nsec / 32);
 	} else {
 		context_desc->seqnum_seed = 0;
-- 
2.7.3


  reply	other threads:[~2019-06-21 17:28 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-21 17:28 [PATCH net-next v5 0/7] net/sched: Add txtime-assist support for taprio Vedang Patel
2019-06-21 17:28 ` [Intel-wired-lan] " Vedang Patel
2019-06-21 17:28 ` Vedang Patel [this message]
2019-06-21 17:28   ` [Intel-wired-lan] [PATCH net-next v5 1/7] igb: clear out skb->tstamp after reading the txtime Vedang Patel
2019-06-21 17:28 ` [PATCH net-next v5 2/7] etf: Add skip_sock_check Vedang Patel
2019-06-21 17:28   ` [Intel-wired-lan] " Vedang Patel
2019-06-24 21:40   ` Jakub Kicinski
2019-06-24 21:40     ` [Intel-wired-lan] " Jakub Kicinski
2019-06-24 23:34     ` Patel, Vedang
2019-06-24 23:34       ` [Intel-wired-lan] " Patel, Vedang
2019-06-21 17:28 ` [PATCH net-next v5 3/7] taprio: calculate cycle_time when schedule is installed Vedang Patel
2019-06-21 17:28   ` [Intel-wired-lan] " Vedang Patel
2019-06-21 17:28 ` [PATCH net-next v5 4/7] taprio: Remove inline directive Vedang Patel
2019-06-21 17:28   ` [Intel-wired-lan] " Vedang Patel
2019-06-21 17:28 ` [PATCH net-next v5 5/7] taprio: Add support for txtime-assist mode Vedang Patel
2019-06-21 17:28   ` [Intel-wired-lan] " Vedang Patel
2019-06-23  3:29   ` kbuild test robot
2019-06-23  3:29     ` [Intel-wired-lan] " kbuild test robot
2019-06-21 17:28 ` [PATCH net-next v5 6/7] taprio: make clock reference conversions easier Vedang Patel
2019-06-21 17:28   ` [Intel-wired-lan] " Vedang Patel
2019-06-21 17:28 ` [PATCH net-next v5 7/7] taprio: Adjust timestamps for TCP packets Vedang Patel
2019-06-21 17:28   ` [Intel-wired-lan] " Vedang Patel

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