[ Upstream commit 1e08511d5d01884a3c9070afd52a47799312074a ]
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 Tested-by: Aaron Brown aaron.f.brown@intel.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- 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 580d14b49fda..a725dc709632 100644 --- a/drivers/net/ethernet/intel/igb/igb_main.c +++ b/drivers/net/ethernet/intel/igb/igb_main.c @@ -5687,6 +5687,7 @@ 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;