Re: [PATCH net-next v3 2/6] mptcp: keep rcv_mwnd_seq in sync with subflow rcv_wnd

[Matthieu Baerts]

Hi Simon,

On 09/03/2026 09:02, Simon Baatz via B4 Relay wrote:
> From: Simon Baatz <gmbnomis@xxxxxxxxx>
> 
> MPTCP shares a receive window across subflows and applies it at the
> subflow level by adjusting each subflow's rcv_wnd when needed.  With
> the new TCP tracking of the maximum advertised window sequence,
> rcv_mwnd_seq must stay consistent with these subflow-level rcv_wnd
> adjustments.

Thank you for these modifications!

> Signed-off-by: Simon Baatz <gmbnomis@xxxxxxxxx>
> ---
>  net/mptcp/options.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/net/mptcp/options.c b/net/mptcp/options.c
> index 43df4293f58bfbd8a8df6bf24b9f15e0f9e238f6..8a1c5698983cff3082d68290626dd8f1e044527f 100644
> --- a/net/mptcp/options.c
> +++ b/net/mptcp/options.c

(...)

> @@ -1338,8 +1339,9 @@ static void mptcp_set_rwin(struct tcp_sock *tp, struct tcphdr *th)
>  		 */
>  		rcv_wnd_new = rcv_wnd_old;
>  		win = rcv_wnd_old - ack_seq;
> -		tp->rcv_wnd = min_t(u64, win, U32_MAX);
> -		new_win = tp->rcv_wnd;
> +		new_win = min_t(u64, win, U32_MAX);
> +		tp->rcv_wnd = new_win;

Out of curiosity, why did you change the two lines above?
(even if it makes sense, the diff is a bit confusing, and the commit
message doesn't mention this :) )

> +		tcp_update_max_rcv_wnd_seq(tp);


This patch adding this new helper each time rcv_wnd is modified looks
good to me:

Reviewed-by: Matthieu Baerts (NGI0) <matttbe@xxxxxxxxxx>


Note: just in case a new version is needed, checkpatch reported an error
in patch 4/6 because of a trailing whitespace (+ No space is necessary
after a cast in patch 1/6), see:

  https://github.com/multipath-tcp/mptcp_net-next/actions/runs/22844479818

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.