From: Enke Chen <enkechen2020@gmail.com>
To: Eric Dumazet <edumazet@google.com>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
Neal Cardwell <ncardwell@google.com>,
enkechen2020@gmail.com
Subject: [PATCH net] tcp: make TCP_USER_TIMEOUT accurate for zero window probes
Date: Fri, 22 Jan 2021 11:13:06 -0800 [thread overview]
Message-ID: <20210122191306.GA99540@localhost.localdomain> (raw)
From: Enke Chen <enchen@paloaltonetworks.com>
The TCP_USER_TIMEOUT is checked by the 0-window probe timer. As the
timer has backoff with a max interval of about two minutes, the
actual timeout for TCP_USER_TIMEOUT can be off by up to two minutes.
In this patch the TCP_USER_TIMEOUT is made more accurate by taking it
into account when computing the timer value for the 0-window probes.
This patch is similar to the one that made TCP_USER_TIMEOUT accurate for
RTOs in commit b701a99e431d ("tcp: Add tcp_clamp_rto_to_user_timeout()
helper to improve accuracy").
Signed-off-by: Enke Chen <enchen@paloaltonetworks.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
---
include/net/tcp.h | 1 +
net/ipv4/tcp_input.c | 4 ++--
net/ipv4/tcp_output.c | 2 ++
net/ipv4/tcp_timer.c | 18 ++++++++++++++++++
4 files changed, 23 insertions(+), 2 deletions(-)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 78d13c88720f..ca7e2c6cc663 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -630,6 +630,7 @@ static inline void tcp_clear_xmit_timers(struct sock *sk)
unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
unsigned int tcp_current_mss(struct sock *sk);
+u32 tcp_clamp_probe0_to_user_timeout(const struct sock *sk, u32 when);
/* Bound MSS / TSO packet size with the half of the window */
static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index bafcab75f425..4923cdbea95a 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3392,8 +3392,8 @@ static void tcp_ack_probe(struct sock *sk)
} else {
unsigned long when = tcp_probe0_when(sk, TCP_RTO_MAX);
- tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
- when, TCP_RTO_MAX);
+ when = tcp_clamp_probe0_to_user_timeout(sk, when);
+ tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0, when, TCP_RTO_MAX);
}
}
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index ab458697881e..8478cf749821 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -4099,6 +4099,8 @@ void tcp_send_probe0(struct sock *sk)
*/
timeout = TCP_RESOURCE_PROBE_INTERVAL;
}
+
+ timeout = tcp_clamp_probe0_to_user_timeout(sk, timeout);
tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0, timeout, TCP_RTO_MAX);
}
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 454732ecc8f3..90722e30ad90 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -40,6 +40,24 @@ static u32 tcp_clamp_rto_to_user_timeout(const struct sock *sk)
return min_t(u32, icsk->icsk_rto, msecs_to_jiffies(remaining));
}
+u32 tcp_clamp_probe0_to_user_timeout(const struct sock *sk, u32 when)
+{
+ struct inet_connection_sock *icsk = inet_csk(sk);
+ u32 remaining;
+ s32 elapsed;
+
+ if (!icsk->icsk_user_timeout || !icsk->icsk_probes_tstamp)
+ return when;
+
+ elapsed = tcp_jiffies32 - icsk->icsk_probes_tstamp;
+ if (unlikely(elapsed < 0))
+ elapsed = 0;
+ remaining = msecs_to_jiffies(icsk->icsk_user_timeout) - elapsed;
+ remaining = max_t(u32, remaining, TCP_TIMEOUT_MIN);
+
+ return min_t(u32, remaining, when);
+}
+
/**
* tcp_write_err() - close socket and save error info
* @sk: The socket the error has appeared on.
--
2.29.2
next reply other threads:[~2021-01-22 19:35 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-22 19:13 Enke Chen [this message]
2021-01-22 20:41 ` [PATCH net] tcp: make TCP_USER_TIMEOUT accurate for zero window probes Eric Dumazet
2021-01-23 1:43 ` Jakub Kicinski
2021-01-23 2:28 ` Enke Chen
2021-01-23 2:34 ` Jakub Kicinski
2021-01-23 2:45 ` Enke Chen
2021-01-24 0:19 ` Neal Cardwell
2021-01-24 0:56 ` Enke Chen
2021-01-24 3:36 ` Jakub Kicinski
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