netdev - [RFC PATCH net-next 4/4] tcp: change SYN ACK retransmit behaviour to account for rehash

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Date:   Mon, 25 Oct 2021 23:35:21 +0300
From:   Akhmat Karakotov <hmukos@...dex-team.ru>
To:     netdev@...r.kernel.org
Cc:     eric.dumazet@...il.com, tom@...bertland.com,
        mitradir@...dex-team.ru, zeil@...dex-team.ru, hmukos@...dex-team.ru
Subject: [RFC PATCH net-next 4/4] tcp: change SYN ACK retransmit behaviour to account for rehash

Disabling rehash behavior did not affect SYN ACK retransmits because hash
was forcefully changed bypassing the sk_rethink_hash function. This patch
adds a condition which checks for rehash mode before resetting hash.

Signed-off-by: Akhmat Karakotov <hmukos@...dex-team.ru>
---
 net/ipv4/tcp_output.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 6d72f3ea48c4..7d54bbe00cde 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -4108,7 +4108,8 @@ int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
 	struct flowi fl;
 	int res;
 
-	tcp_rsk(req)->txhash = net_tx_rndhash();
+	if (sk->sk_txrehash == SOCK_TXREHASH_ENABLED)
+		tcp_rsk(req)->txhash = net_tx_rndhash();
 	res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL,
 				  NULL);
 	if (!res) {
-- 
2.17.1