diff mbox series

[net-next,8/9] mptcp: ignore notsent_lowat setting at the subflow level

Message ID 20231023-send-net-next-20231023-2-v1-8-9dc60939d371@kernel.org (mailing list archive)
State Accepted
Commit 9fdc779331bd3e0b2570c2bced396d53a04a33b9
Delegated to: Netdev Maintainers
Headers show
Series mptcp: Features and fixes for v6.7 | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net-next, async
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 1365 this patch: 1365
netdev/cc_maintainers success CCed 8 of 8 maintainers
netdev/build_clang success Errors and warnings before: 1389 this patch: 1389
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 1390 this patch: 1390
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 12 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Mat Martineau Oct. 23, 2023, 8:44 p.m. UTC 
From: Paolo Abeni <pabeni@redhat.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@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <martineau@kernel.org>
---
 net/mptcp/sockopt.c | 6 ++++++
 1 file changed, 6 insertions(+)
diff mbox series

Patch

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);