netdev - [PATCH bpf-next v4 0/4] XDP: Support atomic replacement of XDP interface attachments

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Date:   Wed, 25 Mar 2020 18:23:25 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     netdev@...r.kernel.org
Cc:     bpf@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        John Fastabend <john.fastabend@...il.com>,
        Lorenz Bauer <lmb@...udflare.com>, Andrey Ignatov <rdna@...com>
Subject: [PATCH bpf-next v4 0/4] XDP: Support atomic replacement of XDP
 interface attachments

This series adds support for atomically replacing the XDP program loaded on an
interface. This is achieved by means of a new netlink attribute that can specify
the expected previous program to replace on the interface. If set, the kernel
will compare this "expected id" attribute with the program currently loaded on
the interface, and reject the operation if it does not match.

With this primitive, userspace applications can avoid stepping on each other's
toes when simultaneously updating the loaded XDP program.

Changelog:

v4:
- Switch back to passing FD instead of ID (Andrii)
- Rename flag to XDP_FLAGS_REPLACE (for consistency with other similar uses)

v3:
- Pass existing ID instead of FD (Jakub)
- Use opts struct for new libbpf function (Andrii)

v2:
- Fix checkpatch nits and add .strict_start_type to netlink policy (Jakub)

---

Toke Høiland-Jørgensen (4):
      xdp: Support specifying expected existing program when attaching XDP
      tools: Add EXPECTED_FD-related definitions in if_link.h
      libbpf: Add function to set link XDP fd while specifying old program
      selftests/bpf: Add tests for attaching XDP programs


 include/linux/netdevice.h                          |  2 +-
 include/uapi/linux/if_link.h                       |  4 +-
 net/core/dev.c                                     | 26 +++++++--
 net/core/rtnetlink.c                               | 14 +++++
 tools/include/uapi/linux/if_link.h                 |  4 +-
 tools/lib/bpf/libbpf.h                             |  8 +++
 tools/lib/bpf/libbpf.map                           |  1 +
 tools/lib/bpf/netlink.c                            | 34 +++++++++++-
 .../testing/selftests/bpf/prog_tests/xdp_attach.c  | 62 ++++++++++++++++++++++
 9 files changed, 146 insertions(+), 9 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/xdp_attach.c