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Message-Id: <20231023-send-net-next-20231023-2-v1-8-9dc60939d371@kernel.org> Date: Mon, 23 Oct 2023 13:44:41 -0700 From: Mat Martineau <martineau@...nel.org> To: Matthieu Baerts <matttbe@...nel.org>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com> Cc: netdev@...r.kernel.org, mptcp@...ts.linux.dev, Mat Martineau <martineau@...nel.org> Subject: [PATCH net-next 8/9] mptcp: ignore notsent_lowat setting at the subflow level From: Paolo Abeni <pabeni@...hat.com> Any latency related tuning taking action at the subflow level does not really affect the user-space, as only the main MPTCP socket is relevant. Anyway any limiting setting may foul the MPTCP scheduler, not being able to fully use the subflow-level cwin, leading to very poor b/w usage. Enforce notsent_lowat to be a no-op on every subflow. Note that TCP_NOTSENT_LOWAT is currently not supported, and properly dealing with that will require more invasive changes. Reviewed-by: Mat Martineau <martineau@...nel.org> Signed-off-by: Paolo Abeni <pabeni@...hat.com> Signed-off-by: Mat Martineau <martineau@...nel.org> --- net/mptcp/sockopt.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c index abf0645cb65d..72858d7d8974 100644 --- a/net/mptcp/sockopt.c +++ b/net/mptcp/sockopt.c @@ -1452,6 +1452,12 @@ void mptcp_sockopt_sync_locked(struct mptcp_sock *msk, struct sock *ssk) ssk->sk_rcvlowat = 0; + /* subflows must ignore any latency-related settings: will not affect + * the user-space - only the msk is relevant - but will foul the + * mptcp scheduler + */ + tcp_sk(ssk)->notsent_lowat = UINT_MAX; + if (READ_ONCE(subflow->setsockopt_seq) != msk->setsockopt_seq) { sync_socket_options(msk, ssk); -- 2.41.0
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