netdev - [PATCH net-next v2] tcp: remove unnecessary update for tp->write_seq in tcp_connect() Commit 783237e8daf13("net-tcp: Fast Open client - sending SYN-data") introduces tcp_connect_queue_skb() and it would overwrite tcp->write_seq, so it is no need to update tp->write_seq before invoking tcp_connect_queue

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Message-Id: <1727999090-19845-1-git-send-email-guoxin0309@gmail.com>
Date: Fri,  4 Oct 2024 07:44:50 +0800
From: "xin.guo" <guoxin0309@...il.com>
To: edumazet@...gle.com
Cc: netdev@...r.kernel.org,
	"xin.guo" <guoxin0309@...il.com>
Subject: [PATCH net-next v2] tcp: remove unnecessary update for tp->write_seq in tcp_connect() Commit 783237e8daf13("net-tcp: Fast Open client - sending SYN-data") introduces tcp_connect_queue_skb() and it would overwrite tcp->write_seq, so it is no need to update tp->write_seq before invoking tcp_connect_queue_skb()

From: "xin.guo" <guoxin0309@...il.com>

Signed-off-by: xin.guo <guoxin0309@...il.com>
---
 net/ipv4/tcp_output.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 4fd746b..3265f34 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -4133,8 +4133,11 @@ int tcp_connect(struct sock *sk)
 	buff = tcp_stream_alloc_skb(sk, sk->sk_allocation, true);
 	if (unlikely(!buff))
 		return -ENOBUFS;
-
-	tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
+        
+        /*SYN eats a sequence byte, write_seq updated by
+         *tcp_connect_queue_skb()
+         */
+	tcp_init_nondata_skb(buff, tp->write_seq, TCPHDR_SYN);
 	tcp_mstamp_refresh(tp);
 	tp->retrans_stamp = tcp_time_stamp_ts(tp);
 	tcp_connect_queue_skb(sk, buff);
-- 
1.8.3.1