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Commit 886236c1 authored by John Heffner's avatar John Heffner Committed by David S. Miller
Browse files

[TCP]: Add RFC3742 Limited Slow-Start, controlled by variable sysctl_tcp_max_ssthresh. 



Signed-off-by: default avatarJohn Heffner <jheffner@psc.edu>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 5ef81475

include/linux/sysctl.h

+1 −0
Original line number Diff line number Diff line
@@ -438,6 +438,7 @@ enum 
	NET_CIPSOV4_RBM_STRICTVALID=121,

	NET_TCP_AVAIL_CONG_CONTROL=122,

	NET_TCP_ALLOWED_CONG_CONTROL=123,

	NET_TCP_MAX_SSTHRESH=124,

};



enum {

include/net/tcp.h

+1 −0
Original line number Diff line number Diff line
@@ -230,6 +230,7 @@ extern int sysctl_tcp_mtu_probing; 
extern int sysctl_tcp_base_mss;

extern int sysctl_tcp_workaround_signed_windows;

extern int sysctl_tcp_slow_start_after_idle;

extern int sysctl_tcp_max_ssthresh;



extern atomic_t tcp_memory_allocated;

extern atomic_t tcp_sockets_allocated;

net/ipv4/sysctl_net_ipv4.c

+8 −0
Original line number Diff line number Diff line
@@ -803,6 +803,14 @@ ctl_table ipv4_table[] = { 
		.proc_handler   = &proc_allowed_congestion_control,

		.strategy	= &strategy_allowed_congestion_control,

	},

	{

		.ctl_name	= NET_TCP_MAX_SSTHRESH,

		.procname	= "tcp_max_ssthresh",

		.data		= &sysctl_tcp_max_ssthresh,

		.maxlen		= sizeof(int),

		.mode		= 0644,

		.proc_handler	= &proc_dointvec,

	},

	{ .ctl_name = 0 }

};

net/ipv4/tcp_cong.c

+22 −9
Original line number Diff line number Diff line
@@ -12,6 +12,8 @@ 
#include <linux/list.h>

#include <net/tcp.h>



int sysctl_tcp_max_ssthresh = 0;



static DEFINE_SPINLOCK(tcp_cong_list_lock);

static LIST_HEAD(tcp_cong_list);
@@ -274,10 +276,13 @@ int tcp_set_congestion_control(struct sock *sk, const char *name) 




/*

 * Linear increase during slow start

 * Slow start (exponential increase) with

 * RFC3742 Limited Slow Start (fast linear increase) support.

 */

void tcp_slow_start(struct tcp_sock *tp)

{

	int cnt = 0;



	if (sysctl_tcp_abc) {

		/* RFC3465: Slow Start

		 * TCP sender SHOULD increase cwnd by the number of
@@ -286,18 +291,26 @@ void tcp_slow_start(struct tcp_sock *tp) 
		 */

		if (tp->bytes_acked < tp->mss_cache)

			return;



		/* We MAY increase by 2 if discovered delayed ack */

		if (sysctl_tcp_abc > 1 && tp->bytes_acked >= 2*tp->mss_cache) {

			if (tp->snd_cwnd < tp->snd_cwnd_clamp)

				tp->snd_cwnd++;

		}

	}



	if (sysctl_tcp_max_ssthresh > 0 &&

	    tp->snd_cwnd > sysctl_tcp_max_ssthresh)

		cnt += sysctl_tcp_max_ssthresh>>1;

	else

		cnt += tp->snd_cwnd;



	/* RFC3465: We MAY increase by 2 if discovered delayed ack */

	if (sysctl_tcp_abc > 1 && tp->bytes_acked >= 2*tp->mss_cache)

		cnt <<= 1;

	tp->bytes_acked = 0;



	tp->snd_cwnd_cnt += cnt;

	while (tp->snd_cwnd_cnt >= tp->snd_cwnd) {

		tp->snd_cwnd_cnt -= tp->snd_cwnd;

		if (tp->snd_cwnd < tp->snd_cwnd_clamp)

			tp->snd_cwnd++;

	}

}

EXPORT_SYMBOL_GPL(tcp_slow_start);



/*