Commit bc800d54 authored by Paolo Abeni's avatar Paolo Abeni Committed by Geliang Tang
Browse files

mptcp: ignore notsent_lowat setting at the subflow level 

mainline inclusion
from mainline-v6.7-rc1
commit 9fdc779331bd3e0b2570c2bced396d53a04a33b9
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I9VYQ9
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=9fdc779331bd3e0b2570c2bced396d53a04a33b9



--------------------------------

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: default avatarMat Martineau <martineau@kernel.org>
Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
Signed-off-by: default avatarMat Martineau <martineau@kernel.org>
Link: https://lore.kernel.org/r/20231023-send-net-next-20231023-2-v1-8-9dc60939d371@kernel.org


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
Reviewed-by: default avatarJackie Liu <liuyun01@kylinos.cn>
Signed-off-by: default avatarGeliang Tang <tanggeliang@kylinos.cn>
parent 18241932

net/mptcp/sockopt.c

+6 −0
Original line number Diff line number Diff line
@@ -1458,6 +1458,12 @@ 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);