> Lorenzo Bianconi <lorenzo.bianconi@xxxxxxxxxx> writes:
>
> >> Lorenzo Bianconi <lorenzo@xxxxxxxxxx> writes:
> >>
> > [...]
> >> > + * Description
> >> > + * For XDP frames split over multiple buffers, the
> >> > + * *xdp_md*\ **->data** and*xdp_md *\ **->data_end** pointers
> >> > + * will point to the start and end of the first fragment only.
> >> > + * This helper can be used to access subsequent fragments by
> >> > + * moving the data pointers. To use, an XDP program can call
> >> > + * this helper with the byte offset of the packet payload that
> >> > + * it wants to access; the helper will move *xdp_md*\ **->data**
> >> > + * and *xdp_md *\ **->data_end** so they point to the requested
> >> > + * payload offset and to the end of the fragment containing this
> >> > + * byte offset, and return the byte offset of the start of the
> >> > + * fragment.
> >>
> >> This comment is wrong now :)
> >
> > actually we are still returning the byte offset of the start of the fragment
> > (base_offset).
>
> Hmm, right, I was looking at the 'return 0':
>
> > +BPF_CALL_2(bpf_xdp_adjust_data, struct xdp_buff *, xdp, u32, offset)
> > +{
> > + struct skb_shared_info *sinfo = xdp_get_shared_info_from_buff(xdp);
> > + u32 base_offset = xdp->mb.headlen;
> > + int i;
> > +
> > + if (!xdp_buff_is_mb(xdp) || offset > sinfo->xdp_frags_size)
> > + return -EINVAL;
> > +
> > + if (offset < xdp->mb.headlen) {
> > + /* linear area */
> > + xdp->data = xdp->data_hard_start + xdp->mb.headroom;
> > + xdp->data_end = xdp->data + xdp->mb.headlen;
> > + return 0;
> > + }
>
> But I guess that's an offset; but that means the helper is not doing
> what it says it's doing if it's within the first fragment. That should
> probably be made consistent... :)
ack, right. I will fix it in v12, thanks.
Regards,
Lorenzo
>
> -Toke
>
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