From 69c312572ec2543f2f52a1dccf3f95d7be5e6937 Mon Sep 17 00:00:00 2001
From: Zhongqiu Duan <dzq.aishenghu0@gmail.com>
Date: Thu, 2 Jan 2025 17:14:26 +0000
Subject: [PATCH] tcp/dccp: allow a connection when sk_max_ack_backlog is zero
[ Upstream commit 3479c7549fb1dfa7a1db4efb7347c7b8ef50de4b ]
If the backlog of listen() is set to zero, sk_acceptq_is_full() allows
one connection to be made, but inet_csk_reqsk_queue_is_full() does not.
When the net.ipv4.tcp_syncookies is zero, inet_csk_reqsk_queue_is_full()
will cause an immediate drop before the sk_acceptq_is_full() check in
tcp_conn_request(), resulting in no connection can be made.
This patch tries to keep consistent with 64a146513f8f ("[NET]: Revert
incorrect accept queue backlog changes.").
Link: https://lore.kernel.org/netdev/20250102080258.53858-1-kuniyu@amazon.com/
Fixes: ef547f2ac16b ("tcp: remove max_qlen_log")
Signed-off-by: Zhongqiu Duan <dzq.aishenghu0@gmail.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250102171426.915276-1-dzq.aishenghu0@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/net/inet_connection_sock.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h
index c81bbfc5f4dfe..05f07bf60c89b 100644
--- a/include/net/inet_connection_sock.h
+++ b/include/net/inet_connection_sock.h
@@ -285,7 +285,7 @@ static inline int inet_csk_reqsk_queue_len(const struct sock *sk)
static inline int inet_csk_reqsk_queue_is_full(const struct sock *sk)
{
- return inet_csk_reqsk_queue_len(sk) >= READ_ONCE(sk->sk_max_ack_backlog);
+ return inet_csk_reqsk_queue_len(sk) > READ_ONCE(sk->sk_max_ack_backlog);
}
bool inet_csk_reqsk_queue_drop(struct sock *sk, struct request_sock *req);
--
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