MPTCP already advertises IP_RECVERR/IPV6_RECVERR as supported, but the
parent socket does not currently provide usable MSG_ERRQUEUE handling.

This series wires the MPTCP socket up to the IPv4/IPv6 error queue
paths. It propagates RECVERR-related sockopts to existing and future
subflows, makes poll() report pending errqueue activity through the
parent socket, and allows recvmsg(MSG_ERRQUEUE) on the MPTCP socket to
consume queued errors with the parent socket ABI.

The series also handles mixed-family subflows by applying the matching
sockopt according to each subflow family, and avoids silently losing an
error skb if requeueing to the parent socket fails under rmem pressure.

v1 -> v2:
  - Retargeted to mptcp-next per Matthieu Baerts' feedback (net-next
    closed during the merge window; iterate on the MPTCP tree).
  - Guard mptcp_setsockopt_v6_recverr() and its dispatch cases in
    mptcp_setsockopt_v6() with #if IS_ENABLED(CONFIG_IPV6) to fix
    the MPTCP CI link break on without_ipv6/with_mptcp configs
    (undefined reference to ipv6_setsockopt).

v1: https://lore.kernel.org/mptcp/20260421152216.38127-1-devnexen@gmail.com/

David Carlier (3):
  mptcp: propagate RECVERR sockopts to subflows
  mptcp: support MSG_ERRQUEUE on the parent socket
  selftests: mptcp: cover RECVERR and MSG_ERRQUEUE

 net/mptcp/protocol.c                          | 121 +++++++++++---
 net/mptcp/sockopt.c                           | 129 +++++++++++++++
 .../selftests/net/mptcp/mptcp_sockopt.c       | 152 ++++++++++++++++++
 3 files changed, 384 insertions(+), 18 deletions(-)


base-commit: 4464afe97dc56e817a23b730979cbc6fc48f1912
-- 
2.53.0

Hi David,

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): Unstable: 1 failed test(s): selftest_mptcp_sockopt ⚠️ 
- KVM Validation: normal (only selftest_mptcp_join): Unstable: 1 failed test(s): selftest_mptcp_join ⚠️ 
- KVM Validation: debug (except selftest_mptcp_join): Unstable: 1 failed test(s): selftest_mptcp_sockopt ⚠️ 
- KVM Validation: debug (only selftest_mptcp_join): Unstable: 1 failed test(s): selftest_mptcp_join ⚠️ 
- 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/24742390998

Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/150b821b1924
Patchwork: https://patchwork.kernel.org/project/mptcp/list/?series=1083991


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)