ever the registers can't be read early otherwise there is no way to correlate them to the packet. This patch introduces a filter function which can be used to determine if a packet should have been timestamped. Supplied with the filter setup by the hwtstamp ioctl, check to make sure the PTP protocol and message type match the expected values. If so, then read the timestamp registers (to free them.) At this point check the descriptor bit, if the bit is set then we know this packet correlates to the timestamp stored in the RXTSTAMP registers. Otherwise, assume that packet was dropped by the hardware, and ignore this timestamp value. However, we have at least unlocked the rxtstamp registers for future timestamping. Due to the way the driver handles skb data, it cannot be directly accessed. In order to work around this, a copy of the skb data into a linear buffer is made. From this buffer it becomes possible to read the data correctly Signed-off-by: Jacob Keller Reviewed-by: Richard Cochran Tested-by: Phil Schmitt Signed-off-by: Jeff Kirsher çLŠØšBx