Yuchung Cheng and Marek Majkowski independently reported a weird
behavior of TCP_USER_TIMEOUT option when used at connect() time.
When the TCP_USER_TIMEOUT is reached, tcp_write_timeout()
believes the flow should live, and the following condition
in tcp_clamp_rto_to_user_timeout() programs one jiffie timers :
remaining = icsk->icsk_user_timeout - elapsed;
if (remaining <= 0)
return 1; /* user timeout has passed; fire ASAP */
This silly situation ends when the max syn rtx count is reached.
This patch makes sure we honor both TCP_SYNCNT and TCP_USER_TIMEOUT,
avoiding these spurious SYN packets.
Fixes: b701a99e431d ("tcp: Add tcp_clamp_rto_to_user_timeout() helper to
improve accuracy")
Signed-off-by: Eric Dumazet <[email protected]>
Reported-by: Yuchung Cheng <[email protected]>
Reported-by: Marek Majkowski <[email protected]>
Cc: Jon Maxwell <[email protected]>
Link: https://marc.info/?l=linux-netdev&m=156940118307949&w=2
---
net/ipv4/tcp_timer.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index
dbd9d2d0ee63aa46ad2dda417da6ec9409442b77..40de2d2364a1eca14c259d77ebed361d17829eb9
100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -210,7 +210,7 @@ static int tcp_write_timeout(struct sock *sk)
struct inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk);
struct net *net = sock_net(sk);
- bool expired, do_reset;
+ bool expired = false, do_reset;
int retry_until;
if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
@@ -242,9 +242,10 @@ static int tcp_write_timeout(struct sock *sk)
if (tcp_out_of_resources(sk, do_reset))
return 1;
}
+ }
+ if (!expired)
expired = retransmits_timed_out(sk, retry_until,
icsk->icsk_user_timeout);
- }
tcp_fastopen_active_detect_blackhole(sk, expired);
if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RTO_CB_FLAG))
--
2.23.0.444.g18eeb5a265-goog
