System Requirements

In order to run this software, you need Linux kernel version 3.0 or newer. Check whether your network interface supports PTP with the following command.

ethtool -T eth0

This command shows whether a MAC supports hardware or software time stamping. The following example output indicates support for hardware time stamping.

Time stamping parameters for eth6:
        hardware-transmit     (SOF_TIMESTAMPING_TX_HARDWARE)
        software-transmit     (SOF_TIMESTAMPING_TX_SOFTWARE)
        hardware-receive      (SOF_TIMESTAMPING_RX_HARDWARE)
        software-receive      (SOF_TIMESTAMPING_RX_SOFTWARE)
        software-system-clock (SOF_TIMESTAMPING_SOFTWARE)
        hardware-raw-clock    (SOF_TIMESTAMPING_RAW_HARDWARE)
PTP Hardware Clock: 1
Hardware Transmit Timestamp Modes:
        off                   (HWTSTAMP_TX_OFF)
        on                    (HWTSTAMP_TX_ON)
Hardware Receive Filter Modes:
        none                  (HWTSTAMP_FILTER_NONE)
        all                   (HWTSTAMP_FILTER_ALL)

The next example shows the case where the MAC only supports software time stamping. The ptp4l program requires either the -S command line argument or the time_stamping software configuration option when using such interfaces.

Time stamping parameters for enp6s0:
        software-transmit     (SOF_TIMESTAMPING_TX_SOFTWARE)
        software-receive      (SOF_TIMESTAMPING_RX_SOFTWARE)
        software-system-clock (SOF_TIMESTAMPING_SOFTWARE)
PTP Hardware Clock: none
Hardware Transmit Timestamp Modes: none
Hardware Receive Filter Modes: none

Note the software-transmit (SOF_TIMESTAMPING_TX_SOFTWARE) capability. If this is lacking, then the MAC cannot be used at all. However, adding this capability entails adding a single line of code to the device driver.