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

[Carsten Bäcker]

Am 19.11.2020 um 03:22 schrieb YongHyeon PYUN:
> On Wed, Nov 18, 2020 at 10:47:08AM +0100, Carsten Bäcker wrote:
>
> [...]
>
>> Sorry, that's my fault - i overlooked your request for a test with pf
>> enabled.
>> The example-ruleset is attached again. I added a line to allow the
>> incoming ping to 5555.
>>
>> I don't see a difference until i enable the redirection to the jail
>> which makes the packet with extended data-length fail.
>> Once i disable RXCSUM it works.
>>
> Thanks for testing.  Unfortunately I couldn't find a driver issue
> on patched smsc(4).  Quick looking pf(4) makes me wonder how it
> verifies UDP datagrams.
>
> Kristof, does pf(4) take advantage of H/W checksummed result for
> UDP datagrams?  It seems pf_check_proto_cksum() always pass
> IPPROTO_TCP such that UDP pseudo checksum is not computed in the
> function.  I'm under the impression that incremental checksum
> update for UDP datagrams with only CSUM_DATA_VALID bit wouldn't
> work.
Just did a quick test with the RPI4, using the sd-card from the previous
run.
The lengthly packet fails even with pf disabled.

Surprisingly the original problem (within the NAT-ted jail) disappeared.