Hi Simon, On 11/03/2026 23:08, Simon Baatz wrote: > On Wed, Mar 11, 2026 at 07:27:34PM +0100, Matthieu Baerts wrote: >> On 09/03/2026 09:02, Simon Baatz via B4 Relay wrote: >>> From: Simon Baatz <[email protected]> >>> >>> 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 <[email protected]> >>> --- >>> 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 :) ) > > I wanted to keep tcp_update_max_rcv_wnd_seq() calls close to the > respective update sites (same pattern everywhere).
Thanks, I now understand the reason. > In the original form > > tp->rcv_wnd = min_t(u64, win, U32_MAX); > tcp_update_max_rcv_wnd_seq(tp); > new_win = tp->rcv_wnd; > > the ordering suggests that tcp_update_max_rcv_wnd_seq() might modify > tp->rcv_wnd. Note that if tp->rcv_mwnd_seq always needs to be modified when tp->rcv_wnd and/or tp->rcv_wup are modified, maybe a single helper could be called to modify all of them, so it might be less likely to forget about modifying tp->rcv_mwnd_seq as well in the future. But probably it might be unlikely to have new places where tp->rcv_wnd and/or tp->rcv_wup need to be modified like here with MPTCP. So probably fine like that. Cheers, Matt -- Sponsored by the NGI0 Core fund.
