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tcp: add sysctl_tcp_rto_min_us

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Adding a sysctl knob to allow user to specify a default
rto_min at socket init time, other than using the hard
coded 200ms default rto_min.

Note that the rto_min route option has the highest precedence
for configuring this setting, followed by the TCP_BPF_RTO_MIN
socket option, followed by the tcp_rto_min_us sysctl.

Signed-off-by: Kevin Yang <yyd@google.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Yuchung Cheng <ycheng@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Tony Lu <tonylu@linux.alibaba.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Kevin Yang 2024-06-03 21:30:54 +00:00 committed by David S. Miller
parent 512bd0f9f9
commit f086edef71
5 changed files with 26 additions and 1 deletions
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13
Documentation/networking/ip-sysctl.rst
View File

@ -1196,6 +1196,19 @@ tcp_pingpong_thresh - INTEGER
Default: 1
tcp_rto_min_us - INTEGER
Minimal TCP retransmission timeout (in microseconds). Note that the
rto_min route option has the highest precedence for configuring this
setting, followed by the TCP_BPF_RTO_MIN socket option, followed by
this tcp_rto_min_us sysctl.
The recommended practice is to use a value less or equal to 200000
microseconds.
Possible Values: 1 - INT_MAX
Default: 200000
UDP variables
=============

1
include/net/netns/ipv4.h
View File

@ -170,6 +170,7 @@ struct netns_ipv4 {
u8 sysctl_tcp_sack;
u8 sysctl_tcp_window_scaling;
u8 sysctl_tcp_timestamps;
int sysctl_tcp_rto_min_us;
u8 sysctl_tcp_recovery;
u8 sysctl_tcp_thin_linear_timeouts;
u8 sysctl_tcp_slow_start_after_idle;

8
net/ipv4/sysctl_net_ipv4.c
View File

@ -1503,6 +1503,14 @@ static struct ctl_table ipv4_net_table[] = {
.proc_handler = proc_dou8vec_minmax,
.extra1 = SYSCTL_ONE,
},
{
.procname = "tcp_rto_min_us",
.data = &init_net.ipv4.sysctl_tcp_rto_min_us,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ONE,
},
};
static __net_init int ipv4_sysctl_init_net(struct net *net)

4
net/ipv4/tcp.c
View File

@ -420,6 +420,7 @@ 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;
tp->out_of_order_queue = RB_ROOT;
sk->tcp_rtx_queue = RB_ROOT;
@ -428,7 +429,8 @@ void tcp_init_sock(struct sock *sk)
INIT_LIST_HEAD(&tp->tsorted_sent_queue);
icsk->icsk_rto = TCP_TIMEOUT_INIT;
icsk->icsk_rto_min = TCP_RTO_MIN;
rto_min_us = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rto_min_us);
icsk->icsk_rto_min = usecs_to_jiffies(rto_min_us);
icsk->icsk_delack_max = TCP_DELACK_MAX;
tp->mdev_us = jiffies_to_usecs(TCP_TIMEOUT_INIT);
minmax_reset(&tp->rtt_min, tcp_jiffies32, ~0U);

1
net/ipv4/tcp_ipv4.c
View File

@ -3502,6 +3502,7 @@ static int __net_init tcp_sk_init(struct net *net)
net->ipv4.sysctl_tcp_shrink_window = 0;
net->ipv4.sysctl_tcp_pingpong_thresh = 1;
net->ipv4.sysctl_tcp_rto_min_us = jiffies_to_usecs(TCP_RTO_MIN);
return 0;
}