[PATCH bpf-next v2 0/8] xdp: hints via kfuncs

Stanislav Fomichev
2022-11-21T18:26:00Z

Please see the first patch in the series for the overall
design and use-cases.

Changes since v1:

- Drop xdp->skb metadata path (Jakub)

No consensus yet on exposing xdp_skb_metadata in UAPI. Exploring
whether everyone would be ok with kfunc to access that part..
Will follow up separately.

- Drop kfunc unrolling (Alexei)

Starting with simple code to resolve per-device ndo kfuncs.
We can always go back to unrolling and keep the same kfuncs
interface in the future.

- Add rx hash metadata (Toke)

Not adding the rest (csum/hash_type/etc), I'd like us to agree on
the framework.

- use dev_get_by_index and add proper refcnt (Toke)

Changes since last RFC:

- drop ice/bnxt example implementation (Alexander)

-ENOHARDWARE to test

- fix/test mlx4 implementation

Confirmed that I get reasonable looking timestamp.
The last patch in the series is the small xsk program that can
be used to dump incoming metadata.

- bpf_push64/bpf_pop64 (Alexei)

x86_64+arm64(untested)+disassembler

- struct xdp_to_skb_metadata -> struct xdp_skb_metadata (Toke)

s/xdp_to_skb/xdp_skb/

- Documentation/bpf/xdp-rx-metadata.rst

Documents functionality, assumptions and limitations.

- bpf_xdp_metadata_export_to_skb returns true/false (Martin)

Plus xdp_md->skb_metadata field to access it.

- BPF_F_XDP_HAS_METADATA flag (Toke/Martin)

Drop magic, use the flag instead.

- drop __randomize_layout

Not sure it's possible to sanely expose it via UAPI. Because every
.o potentially gets its own randomized layout, test_progs
refuses to link.

- remove __net_timestamp in veth driver (John/Jesper)

Instead, calling ktime_get from the kfunc; enough for the selftests.

Future work on RX side:

- Support more devices besides veth and mlx4
- Support more metadata besides RX timestamp.
- Convert skb_metadata_set() callers to xdp_convert_skb_metadata()
which handles extra xdp_skb_metadata

Prior art (to record pros/cons for different approaches):

- Stable UAPI approach:
https://lore.kernel.org/bpf/20220628194812.1453059-1-alexandr.lobakin@intel.com/
- Metadata+BTF_ID appoach:
https://lore.kernel.org/bpf/166256538687.1434226.15760041133601409770.stgit@firesoul/
- v1:
https://lore.kernel.org/bpf/20221115030210.3159213-1-sdf@google.com/T/#t
- kfuncs v2 RFC:
https://lore.kernel.org/bpf/20221027200019.4106375-1-sdf@google.com/
- kfuncs v1 RFC:
https://lore.kernel.org/bpf/20221104032532.1615099-1-sdf@google.com/

Cc: John Fastabend <john.fastabend@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Anatoly Burakov <anatoly.burakov@intel.com>
Cc: Alexander Lobakin <alexandr.lobakin@intel.com>
Cc: Magnus Karlsson <magnus.karlsson@gmail.com>
Cc: Maryam Tahhan <mtahhan@redhat.com>
Cc: xdp-hints@xdp-project.net
Cc: netdev@vger.kernel.org

Stanislav Fomichev (8):
bpf: Document XDP RX metadata
bpf: XDP metadata RX kfuncs
veth: Introduce veth_xdp_buff wrapper for xdp_buff
veth: Support RX XDP metadata
selftests/bpf: Verify xdp_metadata xdp->af_xdp path
mlx4: Introduce mlx4_xdp_buff wrapper for xdp_buff
mxl4: Support RX XDP metadata
selftests/bpf: Simple program to dump XDP RX metadata

Documentation/bpf/xdp-rx-metadata.rst | 90 ++++
.../net/ethernet/mellanox/mlx4/en_netdev.c | 10 +
drivers/net/ethernet/mellanox/mlx4/en_rx.c | 78 +++-
drivers/net/veth.c | 88 ++--
include/linux/bpf.h | 1 +
include/linux/mlx4/device.h | 7 +
include/linux/netdevice.h | 5 +
include/net/xdp.h | 20 +
include/uapi/linux/bpf.h | 5 +
kernel/bpf/core.c | 1 +
kernel/bpf/syscall.c | 17 +-
kernel/bpf/verifier.c | 33 ++
net/core/dev.c | 5 +
net/core/xdp.c | 52 +++
tools/include/uapi/linux/bpf.h | 5 +
tools/testing/selftests/bpf/.gitignore | 1 +
tools/testing/selftests/bpf/Makefile | 8 +-
.../selftests/bpf/prog_tests/xdp_metadata.c | 365 ++++++++++++++++
.../selftests/bpf/progs/xdp_hw_metadata.c | 93 ++++
.../selftests/bpf/progs/xdp_metadata.c | 57 +++
tools/testing/selftests/bpf/xdp_hw_metadata.c | 405 ++++++++++++++++++
tools/testing/selftests/bpf/xdp_metadata.h | 7 +
22 files changed, 1311 insertions(+), 42 deletions(-)
create mode 100644 Documentation/bpf/xdp-rx-metadata.rst
create mode 100644 tools/testing/selftests/bpf/prog_tests/xdp_metadata.c
create mode 100644 tools/testing/selftests/bpf/progs/xdp_hw_metadata.c
create mode 100644 tools/testing/selftests/bpf/progs/xdp_metadata.c
create mode 100644 tools/testing/selftests/bpf/xdp_hw_metadata.c
create mode 100644 tools/testing/selftests/bpf/xdp_metadata.h

--
2.38.1.584.g0f3c55d4c2-goog