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xdp: Allow bpf_xdp_adjust_tail() to grow packet size

Finally, after all drivers have a frame size, allow BPF-helper bpf_xdp_adjust_tail() to grow or extend packet size at frame tail. Remember that helper/macro xdp_data_hard_end have reserved some tailroom. Thus, this helper makes sure that the BPF-prog don't have access to this tailroom area. V2: Remove one chicken check and use WARN_ONCE for other

Jesper Dangaard Brouer committed 6 years ago

Commit c8741e21 parent d628ee42 files · +11 −4Browse files

Unified · Split

2 files
  1. include/uapi/linux/bpf.h +2 −2
  2. net/core/filter.c +9 −2
include/uapi/linux/bpf.h+2−2
@@ -2015,8 +2015,8 @@ union bpf_attr { · 2014 unmodified lines
2015 * int bpf_xdp_adjust_tail(struct xdp_buff *xdp_md, int delta)2015 * int bpf_xdp_adjust_tail(struct xdp_buff *xdp_md, int delta)
2016 * Description2016 * Description
2017 * Adjust (move) *xdp_md*\ **->data_end** by *delta* bytes. It is2017 * Adjust (move) *xdp_md*\ **->data_end** by *delta* bytes. It is
2018 * only possible to shrink the packet as of this writing,2018 * possible to both shrink and grow the packet tail.
2019 * therefore *delta* must be a negative integer.2019 * Shrink done via *delta* being a negative integer.
2020 *2020 *
2021 * A call to this helper is susceptible to change the underlying2021 * A call to this helper is susceptible to change the underlying
2022 * packet buffer. Therefore, at load time, all checks on pointers2022 * packet buffer. Therefore, at load time, all checks on pointers
net/core/filter.c+9−2
@@ -3411,12 +3411,19 @@ static const struct bpf_func_proto bpf_xdp_adjust_head_proto = { · 3410 unmodified lines
3411 3411
3412BPF_CALL_2(bpf_xdp_adjust_tail, struct xdp_buff *, xdp, int, offset)3412BPF_CALL_2(bpf_xdp_adjust_tail, struct xdp_buff *, xdp, int, offset)
3413{3413{
3414 void *data_hard_end = xdp_data_hard_end(xdp); /* use xdp->frame_sz */
3414 void *data_end = xdp->data_end + offset;3415 void *data_end = xdp->data_end + offset;
3415 3416
3416 /* only shrinking is allowed for now. */3417 /* Notice that xdp_data_hard_end have reserved some tailroom */
3417 if (unlikely(offset >= 0))3418 if (unlikely(data_end > data_hard_end))
3418 return -EINVAL;3419 return -EINVAL;
3419 3420
3421 /* ALL drivers MUST init xdp->frame_sz, chicken check below */
3422 if (unlikely(xdp->frame_sz > PAGE_SIZE)) {
3423 WARN_ONCE(1, "Too BIG xdp->frame_sz = %d\n", xdp->frame_sz);
3424 return -EINVAL;
3425 }
3426
3420 if (unlikely(data_end < xdp->data + ETH_HLEN))3427 if (unlikely(data_end < xdp->data + ETH_HLEN))
3421 return -EINVAL;3428 return -EINVAL;
3422 3429