On 07/16, Lorenzo Bianconi wrote: > On Jul 16, Stanislav Fomichev wrote: > > On 07/15, Lorenzo Bianconi wrote: > > > Add a test that verifies skb->ip_summed is set to CHECKSUM_NONE > > > when a device running in XDP mode creates an skb from a xdp_buff > > > if the attached ebpf program returns an XDP_PASS. > > > The test attaches an XDP program returning XDP_PASS, and a TC > > > ingress program that runs the bpf_skb_rx_checksum() kfunc to > > > inspect the resulting skb. After XDP_PASS the driver must invalidate > > > any previously computed hardware RX checksum since XDP may have > > > modified the packet data. > > > The BPF program counts packets per checksum type in a map, and the > > > test runner verifies that after sending traffic the CHECKSUM_NONE > > > counter is non-zero while CHECKSUM_UNNECESSARY and CHECKSUM_COMPLETE > > > counters are zero. > > > > > > Signed-off-by: Lorenzo Bianconi <[email protected]> > > > --- > > > Documentation/networking/xdp-rx-metadata.rst | 5 ++ > > > .../selftests/drivers/net/hw/xdp_metadata.py | 55 +++++++++++++++- > > > .../selftests/net/lib/skb_metadata_csum.bpf.c | 73 > > > ++++++++++++++++++++++ > > > 3 files changed, 132 insertions(+), 1 deletion(-) > > > > > > diff --git a/Documentation/networking/xdp-rx-metadata.rst > > > b/Documentation/networking/xdp-rx-metadata.rst > > > index 93918b3769a3..7434ac98242a 100644 > > > --- a/Documentation/networking/xdp-rx-metadata.rst > > > +++ b/Documentation/networking/xdp-rx-metadata.rst > > > @@ -90,6 +90,11 @@ conversion, and the XDP metadata is not used by the > > > kernel when building > > > ``skbs``. However, TC-BPF programs can access the XDP metadata area using > > > the ``data_meta`` pointer. > > > > [..] > > > > > +If a driver is running in XDP mode, any existing hardware RX checksum > > > +(``CHECKSUM_UNNECESSARY`` or ``CHECKSUM_COMPLETE``) must be invalidated > > > +by setting ``skb->ip_summed`` to ``CHECKSUM_NONE`` before passing the > > > +skb to the kernel, since XDP may have modified the packet data. > > > + > > > In the future, we'd like to support a case where an XDP program > > > can override some of the metadata used for building ``skbs``. > > > > Sorry for keeping nitpicking on this, but I'm still not convinced that > > it is what we currently do. From my previous reply: > > no worries :) > My current take-away from the previous discussion is we just need to document > what would be the driver expected behaviour adding a kselftest for it (without > modifying any driver). > > > > > > > Looking at a few drivers: > > > > - bnxt (bnxt_rx_pkt) does UNNECESSARY - ok > > > > - mlx5 (mlx5e_handle_csum) does UNNECESSARY and skips COMPLETE if there > > > > is > > > > bpf prog attached > > > > - fbnic (fbnic_rx_csum) - can do COMPLETE even with xdp attached? > > > > - gve (gve_rx) - can do COMPLETE even with xdp attached? > > > > (although for gve I might be wrong, there is also gve_rx_skb_csum that only > > does UNNECESSARY). > > > > I'd wait for Jakub to chime in, but it feels like we should just document > > what we currently do as a recommended approach: for the drivers > > that support COMPLETE, do not report it when the bpf program is attached. > > Both NONE and UNNECESSARY are ok. > > I am not completely sure the UNNECESSARY case is different from the COMPLETE > one. What are we supposed to do if the driver reports UNNECESSARY and the ebpf > program modifies some fields covered by the rx-checksum?
For unnecessary, I think the safe expectation is that the bpf program will update the value of the checksum in the packet if it touches the data? > > Also, did you run this test on real HW? NIPA now has HW tests, maybe it > > makes sense to route this series via net-next to get the real coverage? > > What about splitting this series and have two different series: > - bpf-next: add xdp rx kfunc and related selftest > - net-next: add kselftest for the driver expected behaviour. > > What do you think? I'd post everything to net-next to get the HW coverage. Once you get all the acks we can ask the maintainers' guidance.
