[PATCH net] tcp: make TCP_USER_TIMEOUT accurate for zero window probes
From: Enke Chen <hidden>
Date: 2021-01-22 19:35:24
Also in:
lkml
Subsystem:
networking [general], networking [tcp], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Neal Cardwell, Linus Torvalds
From: Enke Chen <redacted>
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 <redacted>
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