A subflow closed after an error is never re-created, even once the path
is back (#440).

v2 has no extra list or timer. The PM opens a new subflow to the same
addresses right away, and if it fails, the same socket is used for the
next try. A new sysctl, net.mptcp.subflow_retries, sets the max tries.

Is a sysctl fine, or should it be a netlink setting?

Patch 1: I saw the EAGAIN error only with the new tests, also with the
retries disabled.

Changes in v2:
 - use the subflow sockets, no list or timer
 - sysctl is now the max number of tries
 - code moved to pm_kernel.c
 - Fixes tag on patch 1
 - one selftest with netfilter
 - Assisted-by on all patches

v1: https://lore.kernel.org/mptcp/20261012171740.464517-1-anilkaushikwireless@gmail.com/

Anil Kaushik (3):
  selftests: mptcp: connect: retry write() on EAGAIN
  mptcp: pm: kernel: retry subflows closed after an error
  selftests: mptcp: join: validate subflow retry after link failure

 Documentation/networking/mptcp-sysctl.rst     |  15 +++
 net/mptcp/ctrl.c                              |  13 ++
 net/mptcp/mib.c                               |   1 +
 net/mptcp/mib.h                               |   1 +
 net/mptcp/pm_kernel.c                         | 116 ++++++++++++++++++
 net/mptcp/protocol.c                          |   9 ++
 net/mptcp/protocol.h                          |  20 +++
 net/mptcp/subflow.c                           |  53 ++++++++
 .../selftests/net/mptcp/mptcp_connect.c       |   8 ++
 .../testing/selftests/net/mptcp/mptcp_join.sh |  90 ++++++++++++++
 10 files changed, 326 insertions(+)

-- 
2.25.1

Hi Anil,

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! ✅
- Perf: Success! ✅
- Task: https://github.com/multipath-tcp/mptcp_net-next/actions/runs/38341335050

Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/067b2bf37cb1
Patchwork: https://patchwork.kernel.org/project/mptcp/list/?series=1184306


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)