[v2,bpf-next,0/8] 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.

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).

Cc: Andrey Ignatov <rdna@fb.com>
Cc: Takshak Chahande <ctakshak@fb.com>

Andrii Nakryiko (8):
  bpf, xdp: maintain info on attached XDP BPF programs in net_device
  bpf, xdp: extract commong 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  |   3 -
 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/netdevice.h                     |  29 +-
 include/net/xdp.h                             |   2 -
 include/uapi/linux/bpf.h                      |  10 +-
 kernel/bpf/syscall.c                          |   5 +
 net/core/dev.c                                | 523 +++++++++++++-----
 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 +
 38 files changed, 601 insertions(+), 350 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