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... :)
-Toke
