[bpf-next,00/13] Introduce BPF STRUCT_OPS

This series introduces BPF STRUCT_OPS.  It is an infra to allow
implementing some specific kernel's function pointers in BPF.
The first use case included in this series is to implement
TCP congestion control algorithm in BPF  (i.e. implement
struct tcp_congestion_ops in BPF).

There has been attempt to move the TCP CC to the user space
(e.g. CCP in TCP).   The common arguments are faster turn around,
get away from long-tail kernel versions in production...etc,
which are legit points.

BPF has been the continuous effort to join both kernel and
userspace upsides together (e.g. XDP to gain the performance
advantage without bypassing the kernel).  The recent BPF
advancements (in particular BTF-aware verifier, BPF trampoline,
BPF CO-RE...) made implementing kernel struct ops (e.g. tcp cc)
possible in BPF.

The idea is to allow implementing tcp_congestion_ops in bpf.
It allows a faster turnaround for testing algorithm in the
production while leveraging the existing (and continue growing) BPF
feature/framework instead of building one specifically for
userspace TCP CC.

Please see individual patch for details.

The bpftool support will be posted in follow-up patches.

Martin KaFai Lau (13):
  bpf: Save PTR_TO_BTF_ID register state when spilling to stack
  bpf: Avoid storing modifier to info->btf_id
  bpf: Add enum support to btf_ctx_access()
  bpf: Support bitfield read access in btf_struct_access
  bpf: Introduce BPF_PROG_TYPE_STRUCT_OPS
  bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS
  bpf: tcp: Support tcp_congestion_ops in bpf
  bpf: Add BPF_FUNC_tcp_send_ack helper
  bpf: Add BPF_FUNC_jiffies
  bpf: Synch uapi bpf.h to tools/
  bpf: libbpf: Add STRUCT_OPS support
  bpf: Add bpf_dctcp example
  bpf: Add bpf_cubic example

 arch/x86/net/bpf_jit_comp.c                   |  10 +-
 include/linux/bpf.h                           |  80 ++-
 include/linux/bpf_types.h                     |   7 +
 include/linux/btf.h                           |  45 ++
 include/linux/filter.h                        |   2 +
 include/net/tcp.h                             |   1 +
 include/uapi/linux/bpf.h                      |  33 +-
 kernel/bpf/Makefile                           |   2 +-
 kernel/bpf/bpf_struct_ops.c                   | 585 +++++++++++++++++
 kernel/bpf/bpf_struct_ops_types.h             |   9 +
 kernel/bpf/btf.c                              | 132 ++--
 kernel/bpf/core.c                             |   1 +
 kernel/bpf/helpers.c                          |  25 +
 kernel/bpf/map_in_map.c                       |   3 +-
 kernel/bpf/syscall.c                          |  64 +-
 kernel/bpf/trampoline.c                       |   5 +-
 kernel/bpf/verifier.c                         | 140 +++-
 net/core/filter.c                             |   4 +-
 net/ipv4/Makefile                             |   4 +
 net/ipv4/bpf_tcp_ca.c                         | 247 ++++++++
 net/ipv4/tcp_cong.c                           |  14 +-
 net/ipv4/tcp_ipv4.c                           |   6 +-
 net/ipv4/tcp_minisocks.c                      |   4 +-
 net/ipv4/tcp_output.c                         |   4 +-
 tools/include/uapi/linux/bpf.h                |  33 +-
 tools/lib/bpf/bpf.c                           |  10 +-
 tools/lib/bpf/bpf.h                           |   5 +-
 tools/lib/bpf/libbpf.c                        | 599 +++++++++++++++++-
 tools/lib/bpf/libbpf.h                        |   3 +-
 tools/lib/bpf/libbpf_probes.c                 |   2 +
 tools/testing/selftests/bpf/bpf_tcp_helpers.h | 228 +++++++
 .../selftests/bpf/prog_tests/bpf_tcp_ca.c     | 220 +++++++
 tools/testing/selftests/bpf/progs/bpf_cubic.c | 502 +++++++++++++++
 tools/testing/selftests/bpf/progs/bpf_dctcp.c | 194 ++++++
 34 files changed, 3089 insertions(+), 134 deletions(-)
 create mode 100644 kernel/bpf/bpf_struct_ops.c
 create mode 100644 kernel/bpf/bpf_struct_ops_types.h
 create mode 100644 net/ipv4/bpf_tcp_ca.c
 create mode 100644 tools/testing/selftests/bpf/bpf_tcp_helpers.h
 create mode 100644 tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
 create mode 100644 tools/testing/selftests/bpf/progs/bpf_cubic.c
 create mode 100644 tools/testing/selftests/bpf/progs/bpf_dctcp.c

On 12/13/19 4:47 PM, Martin KaFai Lau wrote:
> This series introduces BPF STRUCT_OPS.  It is an infra to allow
> implementing some specific kernel's function pointers in BPF.
> The first use case included in this series is to implement
> TCP congestion control algorithm in BPF  (i.e. implement
> struct tcp_congestion_ops in BPF).
> 
> There has been attempt to move the TCP CC to the user space
> (e.g. CCP in TCP).   The common arguments are faster turn around,
> get away from long-tail kernel versions in production...etc,
> which are legit points.
> 
> BPF has been the continuous effort to join both kernel and
> userspace upsides together (e.g. XDP to gain the performance
> advantage without bypassing the kernel).  The recent BPF
> advancements (in particular BTF-aware verifier, BPF trampoline,
> BPF CO-RE...) made implementing kernel struct ops (e.g. tcp cc)
> possible in BPF.
> 
> The idea is to allow implementing tcp_congestion_ops in bpf.
> It allows a faster turnaround for testing algorithm in the
> production while leveraging the existing (and continue growing) BPF
> feature/framework instead of building one specifically for
> userspace TCP CC.
>

This is awesome work Martin !