[PATCH net-next v5 5/5] tcp: Change SYN ACK retransmit behaviour to account for rehash
From: Akhmat Karakotov <hidden>
Date: 2022-01-31 13:33:38
Also in:
bpf
Subsystem:
networking [general], networking [sockets], networking [tcp], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Kuniyuki Iwashima, Willem de Bruijn, Neal Cardwell, Linus Torvalds
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 <redacted> Reviewed-by: Eric Dumazet <edumazet@google.com> --- 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 @@ int sock_setsockopt(struct socket *sock, int level, int optname, 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) {
--
2.17.1