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Commit 89e8c703 authored by JP Abgrall's avatar JP Abgrall Committed by Amit Pundir
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ANDROID: net: ipv4: 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

[AmitP: Folded following android-4.9 commit changes into this patch
        3823c8b26e6e ("ANDROID: tcp: fix tcp_default_init_rwnd() for 4.1")]
Signed-off-by: default avatarAmit Pundir <amit.pundir@linaro.org>
parent 8f414ea4

include/net/tcp.h

+2 −0
Original line number Diff line number Diff line
@@ -248,6 +248,8 @@ extern long sysctl_tcp_mem[3]; 
#define TCP_RACK_STATIC_REO_WND  0x2 /* Use static RACK reo wnd */

#define TCP_RACK_NO_DUPTHRESH    0x4 /* Do not use DUPACK threshold in RACK */



extern int sysctl_tcp_default_init_rwnd;



extern atomic_long_t tcp_memory_allocated;

extern struct percpu_counter tcp_sockets_allocated;

extern unsigned long tcp_memory_pressure;

net/ipv4/sysctl_net_ipv4.c

+22 −0
Original line number Diff line number Diff line
@@ -218,6 +218,21 @@ static int ipv4_fwd_update_priority(struct ctl_table *table, int write, 
	return ret;

}



/* Validate changes from /proc interface. */

static int proc_tcp_default_init_rwnd(struct 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)

{
@@ -525,6 +540,13 @@ static struct ctl_table ipv4_table[] = { 
		.mode		= 0444,

		.proc_handler   = proc_tcp_available_ulp,

	},

	{

		.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
@@ -81,6 +81,7 @@ 
#include <net/busy_poll.h>



int sysctl_tcp_max_orphans __read_mostly = NR_FILE;

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
@@ -187,7 +187,7 @@ 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);