[Linuxptp-users] Truncated jumbo frames on igc when running ptp4l

[Giammarco Z. <g.z...@gm...>]

Hi all,

I noticed a strange behavior when using ptp4l with MTU>1500 on an
i225-based adapter. Namely, when ptp4l is running (I was trying
automotive-slave or -master configurations), incoming frames larger than
1500 bytes are truncated at the end of the payload.
I have attached a pcap trace where I was sending 4000-byte ping requests -
once I started ptp4l in slave mode on the same interface, the received
replies are missing the last 16 bytes and ping would no longer receive them
properly. The only way to restore the correct behavior on the board is to
stop ptp4l, set the MTU back to 1500, then again to the previous value.
It's probably an issue with the igc driver, but I also wanted to circle
this issue on this channel. Please let me know if you have any suggestions
on how to debug this issue.

Best,
Giammarco