> -----Original Message-----
> From: Aya Levin <a...@nvidia.com>
> Sent: Thursday, May 13, 2021 4:37 AM
> To: linuxptp-devel@lists.sourceforge.net
> Subject: [Linuxptp-devel] ptp4l L2 with rx-fcs
>
> Hi,
>
> While debugging the same issue, I found this thread
> https://sourceforge.net/p/linuxptp/mailman/linuxptp-
> users/thread/1382880293.15328.YahooMailBasic%40web161603.mail.bf1.yahoo.
> com/#msg31567827
>
> I also see that ptp4l fails when using the L2 option AND rx-fcs is set
> (ethtool feature is specifically set).
>
> From documentation about rx-fcs:
> This requests that the NIC append the Ethernet Frame Checksum (FCS)
> to the end of the skb data. This allows sniffers and other tools to
> read the CRC recorded by the NIC on receipt of the packet.
> Documentation/networking/netdev-features.rst
>
It sure seems like this is guaranteed to cause problems for any software that
processes the SKBs.. the FCS is now in the data section so it will be treated
as the last 4 bytes of the data... I don't see how you could expect any
different behavior?
> So having these extra 4 bytes is expected. But still ptp4l regard this
> suffix as TLVs. Since both (fcs and tlv) are appended at the end of the
> packet, is there a way which is which?
>
> Was there any progress in that direction? Is this a known issue?
>
> Thanks in advanced,
> Aya
>
>
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