From cb6cd2cec799356e5e2f75a8591894599a6ad49d Mon Sep 17 00:00:00 2001
From: Akhmat Karakotov <hmukos@yandex-team.ru>
Date: Mon, 31 Jan 2022 16:31:25 +0300
Subject: [PATCH] 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@yandex-team.ru>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
net/core/sock.c | 3 ++-
net/ipv4/tcp_output.c | 4 +++-
2 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/net/core/sock.c b/net/core/sock.c
index 5e711b42898f..d6804685f17f 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1452,7 +1452,8 @@ set_sndbuf:
ret = -EINVAL;
break;
}
- sk->sk_txrehash = (u8)val;
+ /* Paired with READ_ONCE() in tcp_rtx_synack() */
+ WRITE_ONCE(sk->sk_txrehash, (u8)val);
break;
default:
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 11c06b9db801..e76bf1e9251e 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -4092,7 +4092,9 @@ int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
struct flowi fl;
int res;
- tcp_rsk(req)->txhash = net_tx_rndhash();
+ /* Paired with WRITE_ONCE() in sock_setsockopt() */
+ if (READ_ONCE(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) {
--
2.42.0