6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Aananth V <aananthv@xxxxxxxxxx>
[ Upstream commit e326578a21414738de45f77badd332fb00bd0f58 ]
For passive TCP Fast Open sockets that had SYN/ACK timeout and did not
send more data in SYN_RECV, upon receiving the final ACK in 3WHS, the
congestion state may awkwardly stay in CA_Loss mode unless the CA state
was undone due to TCP timestamp checks. However, if
tcp_rcv_synrecv_state_fastopen() decides not to undo, then we should
enter CA_Open, because at that point we have received an ACK covering
the retransmitted SYNACKs. Currently, the icsk_ca_state is only set to
CA_Open after we receive an ACK for a data-packet. This is because
tcp_ack does not call tcp_fastretrans_alert (and tcp_process_loss) if
!prior_packets
Note that tcp_process_loss() calls tcp_try_undo_recovery(), so having
tcp_rcv_synrecv_state_fastopen() decide that if we're in CA_Loss we
should call tcp_try_undo_recovery() is consistent with that, and
low risk.
Fixes: dad8cea7add9 ("tcp: fix TFO SYNACK undo to avoid double-timestamp-undo")
Signed-off-by: Aananth V <aananthv@xxxxxxxxxx>
Signed-off-by: Neal Cardwell <ncardwell@xxxxxxxxxx>
Signed-off-by: Yuchung Cheng <ycheng@xxxxxxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
net/ipv4/tcp_input.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 804821d6bd4d4..1f9d1d445fb3b 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6450,22 +6450,23 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
static void tcp_rcv_synrecv_state_fastopen(struct sock *sk)
{
+ struct tcp_sock *tp = tcp_sk(sk);
struct request_sock *req;
/* If we are still handling the SYNACK RTO, see if timestamp ECR allows
* undo. If peer SACKs triggered fast recovery, we can't undo here.
*/
- if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss)
- tcp_try_undo_loss(sk, false);
+ if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss && !tp->packets_out)
+ tcp_try_undo_recovery(sk);
/* Reset rtx states to prevent spurious retransmits_timed_out() */
- tcp_sk(sk)->retrans_stamp = 0;
+ tp->retrans_stamp = 0;
inet_csk(sk)->icsk_retransmits = 0;
/* Once we leave TCP_SYN_RECV or TCP_FIN_WAIT_1,
* we no longer need req so release it.
*/
- req = rcu_dereference_protected(tcp_sk(sk)->fastopen_rsk,
+ req = rcu_dereference_protected(tp->fastopen_rsk,
lockdep_sock_is_held(sk));
reqsk_fastopen_remove(sk, req, false);
--
2.42.0
