[PATCH bpf-next/net v3 0/5] bpf: Add mptcp_subflow bpf_iter support

["Matthieu Baerts (NGI0)" <matttbe@kernel.org>]

Here is a series from Geliang, adding mptcp_subflow bpf_iter support.

We are working on extending MPTCP with BPF, e.g. to control the path
manager -- in charge of the creation, deletion, and announcements of
subflows (paths) -- and the packet scheduler -- in charge of selecting
which available path the next data will be sent to. These extensions
need to iterate over the list of subflows attached to an MPTCP
connection, and do some specific actions via some new kfunc that will be
added later on.

This preparation work is split in different patches:

- Patch 1: register some "basic" MPTCP kfunc.

- Patch 2: add mptcp_subflow bpf_iter support. Note that previous
           versions of this single patch have already been shared to the
           BPF mailing list. The changelog has been kept with a comment,
           but the version number has been reset to avoid confusions.

- Patch 3: add more MPTCP endpoints in the selftests, in order to create
           more than 2 subflows.

- Patch 4: add a very simple test validating mptcp_subflow bpf_iter
           support. This test could be written without the new bpf_iter,
           but it is there only to make sure this specific feature works
           as expected.

- Patch 5: a small fix to drop an unused parameter in the selftests.

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
Changes in v3:
- Previous patches 1, 2 and 5 were no longer needed. (Martin)
- Patch 2: Switch to 'struct sock' and drop unneeded checks. (Martin)
- Patch 4: Adapt the test accordingly.
- Patch 5: New small fix for the selftests.
- Examples and questions for BPF maintainers have been added in Patch 2.
- Link to v2: https://lore.kernel.org/r/20241219-bpf-next-net-mptcp-bpf_iter-subflows-v2-0-ae244d3cdbbc@kernel.org

Changes in v2:
- Patches 1-2: new ones.
- Patch 3: remove two kfunc, more restrictions. (Martin)
- Patch 4: add BUILD_BUG_ON(), more restrictions. (Martin)
- Patch 7: adaptations due to modifications in patches 1-4.
- Link to v1: https://lore.kernel.org/r/20241108-bpf-next-net-mptcp-bpf_iter-subflows-v1-0-cf16953035c1@kernel.org

---
Geliang Tang (5):
      bpf: Register mptcp common kfunc set
      bpf: Add mptcp_subflow bpf_iter
      selftests/bpf: More endpoints for endpoint_init
      selftests/bpf: Add mptcp_subflow bpf_iter subtest
      selftests/bpf: Drop cgroup_fd of run_mptcpify

 net/mptcp/bpf.c                                    |  87 +++++++++++++-
 tools/testing/selftests/bpf/bpf_experimental.h     |   8 ++
 tools/testing/selftests/bpf/prog_tests/mptcp.c     | 133 +++++++++++++++++++--
 tools/testing/selftests/bpf/progs/mptcp_bpf.h      |   4 +
 .../testing/selftests/bpf/progs/mptcp_bpf_iters.c  |  59 +++++++++
 5 files changed, 282 insertions(+), 9 deletions(-)
---
base-commit: dad704ebe38642cd405e15b9c51263356391355c
change-id: 20241108-bpf-next-net-mptcp-bpf_iter-subflows-027f6d87770e

Best regards,
-- 
Matthieu Baerts (NGI0) <matttbe@kernel.org>