Problem with checksum offloading on RPi3 (PF + Jails involved)

[Kristof Provost]

On 29 Oct 2020, at 16:30, Carsten Bäcker wrote:
> Sure, i am willing to help.
>
> Device is a Raspberry Pi 3B (not +), using the onboard-ethernet.
> I attached a bunch of information.
>
> Configuration is stripped down to the minimum required to reproduce 
> the
> problem.
>
Okay, so that’s an SMC2 LAN9514_ETH device.
That’s the dev/usb/net/if_smsc.c driver.

However, before we dig into that driver we should make sure that we’re 
really looking at a checksum problem.
It’s entirely normal for TX checksums to be incorrect when logged on 
the sending host itself (if the hardware does checksum offloading the 
checksum in the packet sent to the MAC is incorrect, and left to the 
hardware to fix).

So, can you confirm that the `"[bad udp cksum 0xe58a -> 0x482d!]` you 
reported was on an inbound packet? And let’s be safe: try to capture 
packets on a different machine. That’ll give us the true packet, after 
the hardware has done checksum calculations.

Best regards,
Kristof