netdev - [PATCH net-next 2/4] tcp_metrics: properly set tp->snd_ssthresh in tcp_init

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Date: Fri, 22 Sep 2023 22:03:54 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Neal Cardwell <ncardwell@...gle.com>, Yuchung Cheng <ycheng@...gle.com>, netdev@...r.kernel.org, 
	eric.dumazet@...il.com, Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 2/4] tcp_metrics: properly set tp->snd_ssthresh in tcp_init_metrics()

We need to set tp->snd_ssthresh to TCP_INFINITE_SSTHRESH
in the case tcp_get_metrics() fails for some reason.

Fixes: 9ad7c049f0f7 ("tcp: RFC2988bis + taking RTT sample from 3WHS for the passive open side")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv4/tcp_metrics.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index 4bfa2fb27de5481ca3d1300d7e7b2c80d1577a31..0c03f564878ff0a0dbefd9b631f54697346c8fa9 100644
--- a/net/ipv4/tcp_metrics.c
+++ b/net/ipv4/tcp_metrics.c
@@ -470,6 +470,10 @@ void tcp_init_metrics(struct sock *sk)
 	u32 val, crtt = 0; /* cached RTT scaled by 8 */
 
 	sk_dst_confirm(sk);
+	/* ssthresh may have been reduced unnecessarily during.
+	 * 3WHS. Restore it back to its initial default.
+	 */
+	tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
 	if (!dst)
 		goto reset;
 
@@ -489,11 +493,6 @@ void tcp_init_metrics(struct sock *sk)
 		tp->snd_ssthresh = val;
 		if (tp->snd_ssthresh > tp->snd_cwnd_clamp)
 			tp->snd_ssthresh = tp->snd_cwnd_clamp;
-	} else {
-		/* ssthresh may have been reduced unnecessarily during.
-		 * 3WHS. Restore it back to its initial default.
-		 */
-		tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
 	}
 	val = tcp_metric_get(tm, TCP_METRIC_REORDERING);
 	if (val && tp->reordering != val)
-- 
2.42.0.515.g380fc7ccd1-goog