Re: [PATCH v4 mptcp-next 2/6] mptcp: fix receive space timestamp initialization.

[Mat Martineau <martineau@kernel.org>]

On Wed, 12 Nov 2025, Paolo Abeni wrote:

> MPTCP initialize the receive buffer stamp in mptcp_rcv_space_init(),
> using the provided subflow stamp. Such helper is invoked in several
> places; for passive sockets, space init happened at clone time.
>
> In such scenario, MPTCP ends-up accesses the subflow stamp before
> its initialization, leading to quite randomic timing for the first
> receive buffer auto-tune event, as the timestamp for newly created
> subflow is not refreshed there.
>
> Fix the issue moving the stamp initialization of the mentioned helper, as
> soon at the data transfer start, and always using a fresh timestamp.
>
> This will also make the next patch cleaner.
>
> Fixes: 013e3179dbd2 ("mptcp: fix rcv space initialization")
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> ---
> v1 -> v2:
> -- factor out only the tstamp change for better reviewability
> ---
> net/mptcp/protocol.c | 7 ++++---
> net/mptcp/protocol.h | 5 +++++
> 2 files changed, 9 insertions(+), 3 deletions(-)

Reviewed-by: Mat Martineau <martineau@kernel.org>