From: Chenguang Zhao <zhaochenguang@kylinos.cn>

As suggested by Paolo, on MP_FAIL reception bound the MP_FAIL
reply and the infinite mapping in the same ACK.

Patch1:
 Add MPFailFallback MIB.

Patch2:
 Makes a pure ACK able to carry an infinite mapping: when
 send_infinite_map is set, mptcp_established_options_dss() fills
 a DSS map with data_len=0 even without a data skb. After the ACK
 that carries both the MP_FAIL reply and that mapping is sent,
 mptcp_try_fallback() is called immediately so the connection leaves
 MPTCP mode without waiting for a later data transmit.

Chenguang Zhao (2):
  mptcp: add MPFailFallback MIB
  mptcp: send MP_FAIL and infinite mapping on the same ACK

 net/mptcp/mib.c      |  1 +
 net/mptcp/mib.h      |  1 +
 net/mptcp/options.c  | 33 ++++++++++++++++++++++++++++++++-
 net/mptcp/pm.c       |  5 +++++
 net/mptcp/protocol.c |  8 +-------
 5 files changed, 40 insertions(+), 8 deletions(-)

--
v3:
 https://lore.kernel.org/all/20260812054653.43799-1-chenguang.zhao@linux.dev/

v2:
 https://lore.kernel.org/all/20260715061830.1057851-1-chenguang.zhao@linux.dev/

v1:
 https://lore.kernel.org/all/20260713064134.914507-1-chenguang.zhao@linux.dev/
-- 
2.25.1

Hi Chenguang,

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/32122351648

Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/02ed8cd94c7c
Patchwork: https://patchwork.kernel.org/project/mptcp/list/?series=1147672


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)