Alexei Starovoitov wrote:
> On Fri, Jul 28, 2023 at 07:39:14PM +0200, Larysa Zaremba wrote:
> >
> > +union xdp_csum_info {
> > + /* Checksum referred to by ``csum_start + csum_offset`` is considered
> > + * valid, but was never calculated, TX device has to do this,
> > + * starting from csum_start packet byte.
> > + * Any preceding checksums are also considered valid.
> > + * Available, if ``status == XDP_CHECKSUM_PARTIAL``.
> > + */
> > + struct {
> > + u16 csum_start;
> > + u16 csum_offset;
> > + };
> > +
>
> CHECKSUM_PARTIAL makes sense on TX, but this RX. I don't see in the above.
It can be observed on RX when packets are looped.
This may be observed even in XDP on veth.
> > + /* Checksum, calculated over the whole packet.
> > + * Available, if ``status & XDP_CHECKSUM_COMPLETE``.
> > + */
> > + u32 checksum;
>
> imo XDP RX should only support XDP_CHECKSUM_COMPLETE with u32 checksum
> or XDP_CHECKSUM_UNNECESSARY.
>
> > +};
> > +
> > +enum xdp_csum_status {
> > + /* HW had parsed several transport headers and validated their
> > + * checksums, same as ``CHECKSUM_UNNECESSARY`` in ``sk_buff``.
> > + * 3 least significant bytes contain number of consecutive checksums,
> > + * starting with the outermost, reported by hardware as valid.
> > + * ``sk_buff`` checksum level (``csum_level``) notation is provided
> > + * for driver developers.
> > + */
> > + XDP_CHECKSUM_VALID_LVL0 = 1, /* 1 outermost checksum */
> > + XDP_CHECKSUM_VALID_LVL1 = 2, /* 2 outermost checksums */
> > + XDP_CHECKSUM_VALID_LVL2 = 3, /* 3 outermost checksums */
> > + XDP_CHECKSUM_VALID_LVL3 = 4, /* 4 outermost checksums */
> > + XDP_CHECKSUM_VALID_NUM_MASK = GENMASK(2, 0),
> > + XDP_CHECKSUM_VALID = XDP_CHECKSUM_VALID_NUM_MASK,
>
> I don't see what bpf prog suppose to do with these levels.
> The driver should pick between 3:
> XDP_CHECKSUM_UNNECESSARY, XDP_CHECKSUM_COMPLETE, XDP_CHECKSUM_NONE.
>
> No levels and no anything partial. please.
This levels business is an unfortunate side effect of
CHECKSUM_UNNECESSARY. For a packet with multiple checksum fields, what
does the boolean actually mean? With these levels, at least that is
well defined: the first N checksum fields.
