Re: [PATCH mptcp-net 0/6] mptcp: pm: userspace: properly deal with the ID0 case

On Mon, 27 Jul 2026, Matthieu Baerts (NGI0) wrote:

> In MPTCP, the local address and port used by the initial subflow has the
> ID "0". It means that when this address and port are used for some
> operations -- e.g. creating a new subflow -- they should be linked to
> the ID0, and no other addresses and ports can get this special ID while
> the initial IP address and port is used.
>
> Instead of dealing with the ID0 case as an exception, add it to the
> local addr list, and deal with it like the others, with minor
> exceptions. That way, it seems easier to maintain instead of adding new
> exceptions at a few places, at the cost of a few more bytes, which seems
> OK in this mode.
>
> The first patch modifies add the initial address to the list, and the
> others remove exceptions, and validate that in the selftests.
>

The approach looks ok to me. Have you tested with mptcpd?

- Mat


> Signed-off-by: Matthieu Baerts (NGI0) <[email protected]>
> ---
> Matthieu Baerts (NGI0) (6):
>      mptcp: pm: userspace: properly handle the ID0 case
>      mptcp: pm: userspace: allow announcing ID0 addr
>      mptcp: pm: userspace: no ID0 exception for RM_ADDR
>      mptcp: pm: userspace: don't dump initial ID0
>      selftests: mptcp: join: new ID0 subflow from the right IP
>      mptcp: pm: restrict in-kernel worker actions to this PM
>
> net/mptcp/pm.c                                  |  8 ++-
> net/mptcp/pm_userspace.c                        | 69 +++++++++----------------
> net/mptcp/protocol.h                            |  1 +
> tools/testing/selftests/net/mptcp/mptcp_join.sh |  7 +--
> 4 files changed, 37 insertions(+), 48 deletions(-)
> ---
> base-commit: ddf9f880a057486230f16d6a4a8cab7e41c40da1
> change-id: 20260724-mptcp-pm-userspace-id0-case-f074f64466c8
>
> Best regards,
> --
> Matthieu Baerts (NGI0) <[email protected]>
>
>
>