[lkml]   [2019]   [Jul]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    Patch in this message
    Subject[PATCH AUTOSEL 5.2 204/249] igb: clear out skb->tstamp after reading the txtime
    From: Vedang Patel <>

    [ 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 <>
    Tested-by: Aaron Brown <>
    Signed-off-by: David S. Miller <>
    Signed-off-by: Sasha Levin <>
    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 39f33afc479c..005c1693efc8 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;
     \ /
      Last update: 2019-07-15 16:15    [W:3.192 / U:26.788 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site