MPTCP_RST_EMPTCP (reset reason 1) is currently used as a catch-all for
several distinct conditions across subflow setup, authentication, and
data-path validation.  This series adds per-event MIB counters at each
of those use sites and validates them from mptcp_join.sh.

Patch 1 adds seven counters (MD5SigReset, MPJoinSynAckNoMPJoin,
MPJoinAckNoMPJoin, MPJoinAckNoCtx, MPJoinNoIdFound, DssReset,
MPJoinNotEstablished) and increments them in mib.c/mib.h, subflow.c and
protocol.c.

Patch 2 adds named env-var expectations for each counter: the
JOIN-related ones in chk_join_nr() and the two reset ones in
chk_rst_nr(), both on fixed namespaces.  It also adds one test inside
signal_address_tests that triggers MPJoinSynAckNoMPJoin from the
existing ns1/ns2 setup.

v4 (this version):
  patch 1: add MPJoinNoIdFound for an MP_JOIN that carries a valid token
           but for which the path manager returns no local id; it
           reaches the same MPTCP_RST_EMPTCP that MPJoinNoTokenFound
           only counts the no-token half of (Matt).
  patch 2: move the MPJoin* checks into chk_join_nr() with fixed
           namespaces, leaving only MD5SigReset and DssReset in
           chk_rst_nr() (Matt); rename the env vars (join_* / rst_md5sig
           / rst_dss); the new test uses mptcp_lib_wait_local_port_listen()
           and asserts with chk_join_nr().
v3: https://lore.kernel.org/all/20260512103331.1934343-1-shardul.b@mpiricsoftware.com/
v2: https://lore.kernel.org/all/20260509183335.969018-1-shardul.b@mpiricsoftware.com/
v1: https://lore.kernel.org/all/20260421095646.3741956-1-shardul.b@mpiricsoftware.com/

Shardul Bankar (2):
  mptcp: add per-event MIB counters for MPTCP_RST_EMPTCP resets
  selftests: mptcp: check per-event MPTCP_RST_EMPTCP counters

 net/mptcp/mib.c                               |  7 ++
 net/mptcp/mib.h                               |  7 ++
 net/mptcp/protocol.c                          |  1 +
 net/mptcp/subflow.c                           | 10 ++
 .../testing/selftests/net/mptcp/mptcp_join.sh | 93 +++++++++++++++++++
 5 files changed, 118 insertions(+)

-- 
2.34.1

Hi Shardul,

Thank you for your modifications, that's great!

Our CI did some validations and here is its report:

- KVM Validation: normal (except selftest_mptcp_join): Success! ✅
- KVM Validation: normal (only selftest_mptcp_join): Success! ✅
- KVM Validation: debug (except selftest_mptcp_join): Success! ✅
- KVM Validation: debug (only selftest_mptcp_join): Success! ✅
- KVM Validation: btf-normal (only bpftest_all): Success! ✅
- KVM Validation: btf-debug (only bpftest_all): Success! ✅
- Task: https://github.com/multipath-tcp/mptcp_net-next/actions/runs/27376133346

Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/5d23d993f27c
Patchwork: https://patchwork.kernel.org/project/mptcp/list/?series=1110277


If there are some issues, you can reproduce them using the same environment as
the one used by the CI thanks to a docker image, e.g.:

    $ cd [kernel source code]
    $ docker run -v "${PWD}:${PWD}:rw" -w "${PWD}" --privileged --rm -it \
        --pull always mptcp/mptcp-upstream-virtme-docker:latest \
        auto-normal

For more details:

    https://github.com/multipath-tcp/mptcp-upstream-virtme-docker


Please note that despite all the efforts that have been already done to have a
stable tests suite when executed on a public CI like here, it is possible some
reported issues are not due to your modifications. Still, do not hesitate to
help us improve that ;-)

Cheers,
MPTCP GH Action bot
Bot operated by Matthieu Baerts (NGI0 Core)