netdev - [PATCH net-next v3 1/2] tcp: derive delack_max with tcp_rto

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Date: Mon,  3 Jun 2024 21:30:53 +0000
From: Kevin Yang <yyd@...gle.com>
To: David Miller <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org, ncardwell@...gle.com, ycheng@...gle.com, 
	kerneljasonxing@...il.com, pabeni@...hat.com, tonylu@...ux.alibaba.com, 
	horms@...nel.org, David.Laight@...lab.com, Kevin Yang <yyd@...gle.com>
Subject: [PATCH net-next v3 1/2] tcp: derive delack_max with tcp_rto_min helper

Rto_min now has multiple sources, ordered by preprecedence high to
low: ip route option rto_min, icsk->icsk_rto_min.

When derive delack_max from rto_min, we should not only use ip
route option, but should use tcp_rto_min helper to get the correct
rto_min.

Signed-off-by: Kevin Yang <yyd@...gle.com>
Reviewed-by: Neal Cardwell <ncardwell@...gle.com>
Reviewed-by: Yuchung Cheng <ycheng@...gle.com>
Reviewed-by: Eric Dumazet <edumazet@...gle.com>
Reviewed-by: Tony Lu <tonylu@...ux.alibaba.com>
Reviewed-by: Jakub Kicinski <kuba@...nel.org>
---
 net/ipv4/tcp_output.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index f97e098f18a5..090fb0c24599 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -4163,16 +4163,9 @@ EXPORT_SYMBOL(tcp_connect);
 
 u32 tcp_delack_max(const struct sock *sk)
 {
-	const struct dst_entry *dst = __sk_dst_get(sk);
-	u32 delack_max = inet_csk(sk)->icsk_delack_max;
-
-	if (dst && dst_metric_locked(dst, RTAX_RTO_MIN)) {
-		u32 rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
-		u32 delack_from_rto_min = max_t(int, 1, rto_min - 1);
+	u32 delack_from_rto_min = max(tcp_rto_min(sk), 2) - 1;
 
-		delack_max = min_t(u32, delack_max, delack_from_rto_min);
-	}
-	return delack_max;
+	return min(inet_csk(sk)->icsk_delack_max, delack_from_rto_min);
 }
 
 /* Send out a delayed ack, the caller does the policy checking
-- 
2.45.1.288.g0e0cd299f1-goog