netdev - [PATCH stable-5.4 1/4] tcp: refactor tcp_retransmit

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Message-ID: <20240716015401.2365503-2-edumazet@google.com>
Date: Tue, 16 Jul 2024 01:53:57 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Neal Cardwell <ncardwell@...gle.com>, Jason Xing <kerneljasonxing@...il.com>, 
	Jon Maxwell <jmaxwell37@...il.com>, Kuniyuki Iwashima <kuniyu@...zon.com>, 
	Eric Dumazet <edumazet@...gle.com>, Willem de Bruijn <willemb@...gle.com>, 
	Soheil Hassas Yeganeh <soheil@...gle.com>
Subject: [PATCH stable-5.4 1/4] tcp: refactor tcp_retransmit_timer()

commit 0d580fbd2db084a5c96ee9c00492236a279d5e0f upstream.

It appears linux-4.14 stable needs a backport of commit
88f8598d0a30 ("tcp: exit if nothing to retransmit on RTO timeout")

Since tcp_rtx_queue_empty() is not in pre 4.15 kernels,
let's refactor tcp_retransmit_timer() to only use tcp_rtx_queue_head()

I will provide to stable teams the squashed patches.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Willem de Bruijn <willemb@...gle.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Acked-by: Soheil Hassas Yeganeh <soheil@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
---
 net/ipv4/tcp_timer.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index e20fced3c9cf691c83b494e11e551161e17d6619..e0bd7999d6d51602fcd868a72d00618234bd0c27 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -452,6 +452,7 @@ void tcp_retransmit_timer(struct sock *sk)
 	struct net *net = sock_net(sk);
 	struct inet_connection_sock *icsk = inet_csk(sk);
 	struct request_sock *req;
+	struct sk_buff *skb;
 
 	req = rcu_dereference_protected(tp->fastopen_rsk,
 					lockdep_sock_is_held(sk));
@@ -464,7 +465,12 @@ void tcp_retransmit_timer(struct sock *sk)
 		 */
 		return;
 	}
-	if (!tp->packets_out || WARN_ON_ONCE(tcp_rtx_queue_empty(sk)))
+
+	if (!tp->packets_out)
+		return;
+
+	skb = tcp_rtx_queue_head(sk);
+	if (WARN_ON_ONCE(!skb))
 		return;
 
 	if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) &&
@@ -496,7 +502,7 @@ void tcp_retransmit_timer(struct sock *sk)
 			goto out;
 		}
 		tcp_enter_loss(sk);
-		tcp_retransmit_skb(sk, tcp_rtx_queue_head(sk), 1);
+		tcp_retransmit_skb(sk, skb, 1);
 		__sk_dst_reset(sk);
 		goto out_reset_timer;
 	}
-- 
2.45.2.993.g49e7a77208-goog