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

Signed-off-by: John Heffner <jheffner@psc.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
John Heffner 2007-03-25 19:21:45 -07:00 committed by David S. Miller
parent 5ef814753e
commit 886236c124
4 changed files with 32 additions and 9 deletions
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1
include/linux/sysctl.h
View File

@ -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 {

1
include/net/tcp.h
View File

@ -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;

8
net/ipv4/sysctl_net_ipv4.c
View File

@ -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 }
};

31
net/ipv4/tcp_cong.c
View File

@ -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
@ -286,17 +291,25 @@ 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;
if (tp->snd_cwnd < tp->snd_cwnd_clamp)
tp->snd_cwnd++;
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);