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Commit 7220b97d authored by JP Abgrall's avatar JP Abgrall Committed by Dmitry Shmidt
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ANDROID: tcp: add a sysctl to config the tcp_default_init_rwnd 

The default initial rwnd is hardcoded to 10.

Now we allow it to be controlled via
  /proc/sys/net/ipv4/tcp_default_init_rwnd
which limits the values from 3 to 100

This is somewhat needed because ipv6 routes are
autoconfigured by the kernel.

See "An Argument for Increasing TCP's Initial Congestion Window"
in https://developers.google.com/speed/articles/tcp_initcwnd_paper.pdf



Change-Id: I386b2a9d62de0ebe05c1ebe1b4bd91b314af5c54
Signed-off-by: default avatarJP Abgrall <jpa@google.com>

Conflicts:
	net/ipv4/sysctl_net_ipv4.c
	net/ipv4/tcp_input.c
parent f84e6a1c

include/net/tcp.h

+1 −0
Original line number Diff line number Diff line
@@ -271,6 +271,7 @@ extern int sysctl_tcp_autocorking; 
extern int sysctl_tcp_invalid_ratelimit;

extern int sysctl_tcp_pacing_ss_ratio;

extern int sysctl_tcp_pacing_ca_ratio;

extern int sysctl_tcp_default_init_rwnd;



extern atomic_long_t tcp_memory_allocated;

extern struct percpu_counter tcp_sockets_allocated;

net/ipv4/sysctl_net_ipv4.c

+22 −0
Original line number Diff line number Diff line
@@ -151,6 +151,21 @@ static int ipv4_ping_group_range(struct ctl_table *table, int write, 
	return ret;

}



/* Validate changes from /proc interface. */

static int proc_tcp_default_init_rwnd(ctl_table *ctl, int write,

				      void __user *buffer,

				      size_t *lenp, loff_t *ppos)

{

	int old_value = *(int *)ctl->data;

	int ret = proc_dointvec(ctl, write, buffer, lenp, ppos);

	int new_value = *(int *)ctl->data;



	if (write && ret == 0 && (new_value < 3 || new_value > 100))

		*(int *)ctl->data = old_value;



	return ret;

}



static int proc_tcp_congestion_control(struct ctl_table *ctl, int write,

				       void __user *buffer, size_t *lenp, loff_t *ppos)

{
@@ -623,6 +638,13 @@ static struct ctl_table ipv4_table[] = { 
		.mode		= 0644,

		.proc_handler	= proc_dointvec_ms_jiffies,

	},

	{

		.procname       = "tcp_default_init_rwnd",

		.data           = &sysctl_tcp_default_init_rwnd,

		.maxlen         = sizeof(int),

		.mode           = 0644,

		.proc_handler   = proc_tcp_default_init_rwnd

	},

	{

		.procname	= "icmp_msgs_per_sec",

		.data		= &sysctl_icmp_msgs_per_sec,

net/ipv4/tcp_input.c

+1 −0
Original line number Diff line number Diff line
@@ -100,6 +100,7 @@ int sysctl_tcp_thin_dupack __read_mostly; 
int sysctl_tcp_moderate_rcvbuf __read_mostly = 1;

int sysctl_tcp_early_retrans __read_mostly = 3;

int sysctl_tcp_invalid_ratelimit __read_mostly = HZ/2;

int sysctl_tcp_default_init_rwnd __read_mostly = TCP_INIT_CWND * 2;



#define FLAG_DATA		0x01 /* Incoming frame contained data.		*/

#define FLAG_WIN_UPDATE		0x02 /* Incoming ACK was a window update.	*/

net/ipv4/tcp_output.c

+1 −1
Original line number Diff line number Diff line
@@ -188,7 +188,7 @@ u32 tcp_default_init_rwnd(u32 mss) 
	 * (RFC 3517, Section 4, NextSeg() rule (2)). Further place a

	 * limit when mss is larger than 1460.

	 */

	u32 init_rwnd = TCP_INIT_CWND * 2;

	u32 init_rwnd = sysctl_tcp_default_init_rwnd;



	if (mss > 1460)

		init_rwnd = max((1460 * init_rwnd) / mss, 2U);