From: Eric Dumazet edumazet@google.com
[ Upstream commit a66b10c05ee2d744189e9a2130394b070883d289 ]
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 edumazet@google.com Reported-by: Yuchung Cheng ycheng@google.com Reported-by: Marek Majkowski marek@cloudflare.com Cc: Jon Maxwell jmaxwell37@gmail.com Link: https://marc.info/?l=linux-netdev&m=156940118307949&w=2 Acked-by: Jon Maxwell jmaxwell37@gmail.com Tested-by: Marek Majkowski marek@cloudflare.com Signed-off-by: Marek Majkowski marek@cloudflare.com Acked-by: Yuchung Cheng ycheng@google.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/tcp_timer.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
--- a/net/ipv4/tcp_timer.c +++ b/net/ipv4/tcp_timer.c @@ -219,7 +219,7 @@ static int tcp_write_timeout(struct sock 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)) { @@ -251,9 +251,10 @@ static int tcp_write_timeout(struct sock 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))