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[ Upstream commit7b90f5a665] PTP TX timestamp handling was observed to be broken with this driver when using the raw Layer 2 PTP encapsulation. ptp4l was not receiving the expected TX timestamp after transmitting a packet, causing it to enter a failure state. The problem appears to be due to the way that the driver pads packets which are smaller than the Ethernet minimum of 60 bytes. If headroom space was available in the SKB, this caused the driver to move the data back to utilize it. However, this appears to cause other data references in the SKB to become inconsistent. In particular, this caused the ptp_one_step_sync function to later (in the TX completion path) falsely detect the packet as a one-step SYNC packet, even when it was not, which caused the TX timestamp to not be processed when it should be. Using the headroom for this purpose seems like an unnecessary complexity as this is not a hot path in the driver, and in most cases it appears that there is sufficient tailroom to not require using the headroom anyway. Remove this usage of headroom to prevent this inconsistency from occurring and causing other problems. Fixes:653e92a917("net: macb: add support for padding and fcs computation") Signed-off-by: Robert Hancock <robert.hancock@calian.com> Reviewed-by: Jacob Keller <jacob.e.keller@intel.com> Tested-by: Claudiu Beznea <claudiu.beznea@microchip.com> # on SAMA7G5 Reviewed-by: Claudiu Beznea <claudiu.beznea@microchip.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.