Commit f086edef authored by Kevin Yang's avatar Kevin Yang Committed by David S. Miller
Browse files

tcp: add sysctl_tcp_rto_min_us 



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: default avatarKevin Yang <yyd@google.com>
Reviewed-by: default avatarNeal Cardwell <ncardwell@google.com>
Reviewed-by: default avatarYuchung Cheng <ycheng@google.com>
Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarTony Lu <tonylu@linux.alibaba.com>
Reviewed-by: default avatarJakub Kicinski <kuba@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 512bd0f9

Documentation/networking/ip-sysctl.rst

+13 −0
Original line number Diff line number Diff line
@@ -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

=============

include/net/netns/ipv4.h

+1 −0
Original line number Diff line number Diff line
@@ -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;

net/ipv4/sysctl_net_ipv4.c

+8 −0
Original line number Diff line number Diff line
@@ -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)

net/ipv4/tcp.c

+3 −1
Original line number Diff line number Diff line
@@ -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);

net/ipv4/tcp_ipv4.c

+1 −0
Original line number Diff line number Diff line
@@ -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;

}