Hi Greg,

On 16/10/2025 15:25, gregkh@linuxfoundation.org wrote:

This is a note to let you know that I've just added the patch titled

selftests: mptcp: join: validate C-flag + def limit

to the 5.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: selftests-mptcp-join-validate-c-flag-def-limit.patch and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

I do! :)

From 008385efd05e04d8dff299382df2e8be0f91d8a0 Mon Sep 17 00:00:00 2001 From: "Matthieu Baerts (NGI0)" matttbe@kernel.org Date: Thu, 25 Sep 2025 12:32:37 +0200 Subject: selftests: mptcp: join: validate C-flag + def limit

From: Matthieu Baerts (NGI0) matttbe@kernel.org

commit 008385efd05e04d8dff299382df2e8be0f91d8a0 upstream.

The previous commit adds an exception for the C-flag case. The 'mptcp_join.sh' selftest is extended to validate this case.

In this subtest, there is a typical CDN deployment with a client where MPTCP endpoints have been 'automatically' configured:

• the server set net.mptcp.allow_join_initial_addr_port=0

• the client has multiple 'subflow' endpoints, and the default limits: not accepting ADD_ADDRs.

Without the parent patch, the client is not able to establish new subflows using its 'subflow' endpoints. The parent commit fixes that.

The 'Fixes' tag here below is the same as the one from the previous commit: this patch here is not fixing anything wrong in the selftests, but it validates the previous fix for an issue introduced by this commit ID.

Fixes: df377be38725 ("mptcp: add deny_join_id0 in mptcp_options_received")

This commit has been introduced in v5.14, and not backported before. Do you mind dropping it from v5.10 please? :)

Cheers, Matt