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Message-ID: <20250207152830.2527578-6-edumazet@google.com>
Date: Fri, 7 Feb 2025 15:28:30 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, Neal Cardwell <ncardwell@...gle.com>,
Kuniyuki Iwashima <kuniyu@...zon.com>, Jason Xing <kernelxing@...cent.com>,
Simon Horman <horms@...nel.org>, eric.dumazet@...il.com,
Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 5/5] tcp: add tcp_rto_max_ms sysctl
Previous patch added a TCP_RTO_MAX_MS socket option
to tune a TCP socket max RTO value.
Many setups prefer to change a per netns sysctl.
This patch adds /proc/sys/net/ipv4/tcp_rto_max_ms
Its initial value is 120000 (120 seconds).
Keep in mind that a decrease of tcp_rto_max_ms
means shorter overall timeouts, unless tcp_retries2
sysctl is increased.
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
Documentation/networking/ip-sysctl.rst | 13 +++++++++++++
.../networking/net_cachelines/netns_ipv4_sysctl.rst | 1 +
include/net/netns/ipv4.h | 1 +
net/ipv4/sysctl_net_ipv4.c | 10 ++++++++++
net/ipv4/tcp.c | 6 +++---
net/ipv4/tcp_ipv4.c | 1 +
6 files changed, 29 insertions(+), 3 deletions(-)
diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index 363b4950d542aa32fbf6ab1617de46a900061f82..054561f8dcae77d4183f5b7e45f671ba8979390a 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -705,6 +705,8 @@ tcp_retries2 - INTEGER
seconds and is a lower bound for the effective timeout.
TCP will effectively time out at the first RTO which exceeds the
hypothetical timeout.
+ If tcp_rto_max_ms is decreased, it is recommended to also
+ change tcp_retries2.
RFC 1122 recommends at least 100 seconds for the timeout,
which corresponds to a value of at least 8.
@@ -1237,6 +1239,17 @@ tcp_rto_min_us - INTEGER
Default: 200000
+tcp_rto_max_ms - INTEGER
+ Maximal TCP retransmission timeout (in ms).
+ Note that TCP_RTO_MAX_MS socket option has higher precedence.
+
+ When changing tcp_rto_max_ms, it is important to understand
+ that tcp_retries2 might need a change.
+
+ Possible Values: 1000 - 120,000
+
+ Default: 120,000
+
UDP variables
=============
diff --git a/Documentation/networking/net_cachelines/netns_ipv4_sysctl.rst b/Documentation/networking/net_cachelines/netns_ipv4_sysctl.rst
index de0263302f16dd815593671c4f75a93ed6f7cac4..6e7b20afd2d4984233e91d713ee9acd4b2e007f2 100644
--- a/Documentation/networking/net_cachelines/netns_ipv4_sysctl.rst
+++ b/Documentation/networking/net_cachelines/netns_ipv4_sysctl.rst
@@ -86,6 +86,7 @@ u8 sysctl_tcp_sack
u8 sysctl_tcp_window_scaling tcp_syn_options,tcp_parse_options
u8 sysctl_tcp_timestamps
u8 sysctl_tcp_early_retrans read_mostly tcp_schedule_loss_probe(tcp_write_xmit)
+u32 sysctl_tcp_rto_max_ms
u8 sysctl_tcp_recovery tcp_fastretrans_alert
u8 sysctl_tcp_thin_linear_timeouts tcp_retrans_timer(on_thin_streams)
u8 sysctl_tcp_slow_start_after_idle unlikely(tcp_cwnd_validate-network-not-starved)
diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index 46452da352061007d19d00fdacddd25bbe56444d..45ac125e8aebb99d4083d540c907f0d560dac0b0 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -181,6 +181,7 @@ struct netns_ipv4 {
u8 sysctl_tcp_window_scaling;
u8 sysctl_tcp_timestamps;
int sysctl_tcp_rto_min_us;
+ int sysctl_tcp_rto_max_ms;
u8 sysctl_tcp_recovery;
u8 sysctl_tcp_thin_linear_timeouts;
u8 sysctl_tcp_slow_start_after_idle;
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 42cb5dc9cb245c26f9a38f8c8c4b26b1adddca39..3a43010d726fb103beaad2b11d6797424b0c946e 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -28,6 +28,7 @@ static int tcp_adv_win_scale_max = 31;
static int tcp_app_win_max = 31;
static int tcp_min_snd_mss_min = TCP_MIN_SND_MSS;
static int tcp_min_snd_mss_max = 65535;
+static int tcp_rto_max_max = TCP_RTO_MAX_SEC * MSEC_PER_SEC;
static int ip_privileged_port_min;
static int ip_privileged_port_max = 65535;
static int ip_ttl_min = 1;
@@ -1583,6 +1584,15 @@ static struct ctl_table ipv4_net_table[] = {
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ONE,
},
+ {
+ .procname = "tcp_rto_max_ms",
+ .data = &init_net.ipv4.sysctl_tcp_rto_max_ms,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = SYSCTL_ONE_THOUSAND,
+ .extra2 = &tcp_rto_max_max,
+ },
};
static __net_init int ipv4_sysctl_init_net(struct net *net)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index a9b92d8bfb5644431683ec214aedd0e9756e8a0a..d01f42cf3863bd87ac0a91ab01505616a1bd4225 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -423,7 +423,7 @@ void tcp_init_sock(struct sock *sk)
{
struct inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk);
- int rto_min_us;
+ int rto_min_us, rto_max_ms;
tp->out_of_order_queue = RB_ROOT;
sk->tcp_rtx_queue = RB_ROOT;
@@ -433,8 +433,8 @@ void tcp_init_sock(struct sock *sk)
icsk->icsk_rto = TCP_TIMEOUT_INIT;
- /* Use a sysctl ? */
- icsk->icsk_rto_max = TCP_RTO_MAX;
+ rto_max_ms = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rto_max_ms);
+ icsk->icsk_rto_max = msecs_to_jiffies(rto_max_ms);
rto_min_us = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rto_min_us);
icsk->icsk_rto_min = usecs_to_jiffies(rto_min_us);
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 06fb0123d2d60e22f19ea48b73ac3668c51465a2..d1fd2128ac6cce9b845b1f8d278a194c511db87b 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -3532,6 +3532,7 @@ static int __net_init tcp_sk_init(struct net *net)
net->ipv4.sysctl_tcp_pingpong_thresh = 1;
net->ipv4.sysctl_tcp_rto_min_us = jiffies_to_usecs(TCP_RTO_MIN);
+ net->ipv4.sysctl_tcp_rto_max_ms = TCP_RTO_MAX_SEC * MSEC_PER_SEC;
return 0;
}
--
2.48.1.502.g6dc24dfdaf-goog
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