[v4,bpf-next,0/9] BPF XDP link

Following cgroup and netns examples, implement bpf_link support for XDP.

The semantics is described in patch #2. Program and link attachments are
mutually exclusive, in the sense that neither link can replace attached
program nor program can replace attached link. Link can't replace attached
link as well, as is the case for any other bpf_link implementation.

Patch #1 refactors existing BPF program-based attachment API and centralizes
high-level query/attach decisions in generic kernel code, while drivers are
kept simple and are instructed with low-level decisions about attaching and
detaching specific bpf_prog. This also makes QUERY command unnecessary, and
patch #8 removes support for it from all kernel drivers. If that's a bad idea,
we can drop that patch altogether.

With refactoring in patch #1, adding bpf_xdp_link is completely transparent to
drivers, they are still functioning at the level of "effective" bpf_prog, that
should be called in XDP data path.

Corresponding libbpf support for BPF XDP link is added in patch #5.

v3->v4:
- fix a compilation warning in one of drivers (Jakub);

v2->v3:
- fix build when CONFIG_BPF_SYSCALL=n (kernel test robot);

v1->v2:
- fix prog refcounting bug (David);
- split dev_change_xdp_fd() changes into 2 patches (David);
- add extack messages to all user-induced errors (David).


Andrii Nakryiko (9):
  bpf: make bpf_link API available indepently of CONFIG_BPF_SYSCALL
  bpf, xdp: maintain info on attached XDP BPF programs in net_device
  bpf, xdp: extract common XDP program attachment logic
  bpf, xdp: add bpf_link-based XDP attachment API
  bpf, xdp: implement LINK_UPDATE for BPF XDP link
  bpf: implement BPF XDP link-specific introspection APIs
  libbpf: add support for BPF XDP link
  selftests/bpf: add BPF XDP link selftests
  bpf, xdp: remove XDP_QUERY_PROG and XDP_QUERY_PROG_HW XDP commands

 drivers/net/ethernet/amazon/ena/ena_netdev.c  |   6 -
 drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c |   4 -
 .../net/ethernet/cavium/thunder/nicvf_main.c  |   3 -
 .../net/ethernet/freescale/dpaa2/dpaa2-eth.c  |   5 -
 drivers/net/ethernet/intel/i40e/i40e_main.c   |   3 -
 drivers/net/ethernet/intel/ice/ice_main.c     |   3 -
 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c |   4 -
 .../net/ethernet/intel/ixgbevf/ixgbevf_main.c |   6 -
 drivers/net/ethernet/marvell/mvneta.c         |   5 -
 .../net/ethernet/marvell/mvpp2/mvpp2_main.c   |   3 -
 .../net/ethernet/mellanox/mlx4/en_netdev.c    |  24 -
 .../net/ethernet/mellanox/mlx5/core/en_main.c |  18 -
 .../ethernet/netronome/nfp/nfp_net_common.c   |   4 -
 .../net/ethernet/qlogic/qede/qede_filter.c    |   3 -
 drivers/net/ethernet/sfc/efx.c                |   5 -
 drivers/net/ethernet/socionext/netsec.c       |   3 -
 drivers/net/ethernet/ti/cpsw_priv.c           |   3 -
 drivers/net/hyperv/netvsc_bpf.c               |  21 +-
 drivers/net/netdevsim/bpf.c                   |   4 -
 drivers/net/netdevsim/netdevsim.h             |   2 +-
 drivers/net/tun.c                             |  15 -
 drivers/net/veth.c                            |  15 -
 drivers/net/virtio_net.c                      |  17 -
 drivers/net/xen-netfront.c                    |  21 -
 include/linux/bpf.h                           |  81 ++-
 include/linux/netdevice.h                     |  29 +-
 include/net/xdp.h                             |   2 -
 include/uapi/linux/bpf.h                      |  10 +-
 kernel/bpf/syscall.c                          |   5 +
 net/core/dev.c                                | 530 +++++++++++++-----
 net/core/rtnetlink.c                          |   5 +-
 net/core/xdp.c                                |   9 -
 tools/include/uapi/linux/bpf.h                |  10 +-
 tools/lib/bpf/libbpf.c                        |   9 +-
 tools/lib/bpf/libbpf.h                        |   2 +
 tools/lib/bpf/libbpf.map                      |   1 +
 .../selftests/bpf/prog_tests/section_names.c  |   2 +-
 .../selftests/bpf/prog_tests/xdp_link.c       | 137 +++++
 .../selftests/bpf/progs/test_xdp_link.c       |  12 +
 39 files changed, 658 insertions(+), 383 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/xdp_link.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_link.c

On Tue, Jul 21, 2020 at 11:46 PM Andrii Nakryiko <andriin@fb.com> wrote:
>
> Following cgroup and netns examples, implement bpf_link support for XDP.
>
> The semantics is described in patch #2. Program and link attachments are
> mutually exclusive, in the sense that neither link can replace attached
> program nor program can replace attached link. Link can't replace attached
> link as well, as is the case for any other bpf_link implementation.
>
> Patch #1 refactors existing BPF program-based attachment API and centralizes
> high-level query/attach decisions in generic kernel code, while drivers are
> kept simple and are instructed with low-level decisions about attaching and
> detaching specific bpf_prog. This also makes QUERY command unnecessary, and
> patch #8 removes support for it from all kernel drivers. If that's a bad idea,
> we can drop that patch altogether.
>
> With refactoring in patch #1, adding bpf_xdp_link is completely transparent to
> drivers, they are still functioning at the level of "effective" bpf_prog, that
> should be called in XDP data path.
>
> Corresponding libbpf support for BPF XDP link is added in patch #5.
>
> v3->v4:
> - fix a compilation warning in one of drivers (Jakub);

As far as I could review everything looks fine,
so I've applied the set.
The code is delicate. I wish people were more active doing code reviews.
So I encourage folks to still look at it. If there is anything missing I'm sure
Andrii will fix it up in the follow up.