Previously it was not possible to make a distinction between plain TCP sockets and MPTCP subflow sockets on the BPF_PROG_TYPE_SOCK_OPS hook.

This patch series now enables a fine control of subflow sockets. In its current state, it allows to put different sockopt on each subflow from a same MPTCP connection (socket mark, TCP congestion algorithm, ...) using BPF programs.

It should also be the basis of exposing MPTCP-specific fields through BPF.

v2 -> v3: - minor modifications in new MPTCP selftests (Song). More details in patch notes. - rebase on latest bpf-next - the new is_mptcp field in bpf_tcp_sock is left as an __u32 to keep cohesion with the is_fullsock field from bpf_sock_ops. Also it seems easier with a __u32 on the verifier side.

v1 -> v2: - add basic mandatory selftests for the new helper and is_mptcp field (Alexei) - rebase on latest bpf-next

Nicolas Rybowski (5): bpf: expose is_mptcp flag to bpf_tcp_sock mptcp: attach subflow socket to parent cgroup bpf: add 'bpf_mptcp_sock' structure and helper bpf: selftests: add MPTCP test base bpf: selftests: add bpf_mptcp_sock() verifier tests

include/linux/bpf.h | 33 +++++ include/uapi/linux/bpf.h | 15 +++ kernel/bpf/verifier.c | 30 +++++ net/core/filter.c | 13 +- net/mptcp/Makefile | 2 + net/mptcp/bpf.c | 72 +++++++++++ net/mptcp/subflow.c | 27 ++++ scripts/bpf_helpers_doc.py | 2 + tools/include/uapi/linux/bpf.h | 15 +++ tools/testing/selftests/bpf/config | 1 + tools/testing/selftests/bpf/network_helpers.c | 37 +++++- tools/testing/selftests/bpf/network_helpers.h | 3 + .../testing/selftests/bpf/prog_tests/mptcp.c | 118 ++++++++++++++++++ tools/testing/selftests/bpf/progs/mptcp.c | 48 +++++++ tools/testing/selftests/bpf/verifier/sock.c | 63 ++++++++++ 15 files changed, 473 insertions(+), 6 deletions(-) create mode 100644 net/mptcp/bpf.c create mode 100644 tools/testing/selftests/bpf/prog_tests/mptcp.c create mode 100644 tools/testing/selftests/bpf/progs/mptcp.c