linux/net/ipv4/tcp_scalable.c
Pengcheng Yang 5415e3c37a tcp: fix stretch ACK bugs in Scalable
Change Scalable to properly handle stretch ACKs in additive
increase mode by passing in the count of ACKed packets to
tcp_cong_avoid_ai().

In addition, because we are now precisely accounting for
stretch ACKs, including delayed ACKs, we can now change
TCP_SCALABLE_AI_CNT to 100.

Signed-off-by: Pengcheng Yang <yangpc@wangsu.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2020-03-16 18:26:54 -07:00

66 lines
1.4 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/* Tom Kelly's Scalable TCP
*
* See http://www.deneholme.net/tom/scalable/
*
* John Heffner <jheffner@sc.edu>
*/
#include <linux/module.h>
#include <net/tcp.h>
/* These factors derived from the recommended values in the aer:
* .01 and and 7/8.
*/
#define TCP_SCALABLE_AI_CNT 100U
#define TCP_SCALABLE_MD_SCALE 3
static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 acked)
{
struct tcp_sock *tp = tcp_sk(sk);
if (!tcp_is_cwnd_limited(sk))
return;
if (tcp_in_slow_start(tp)) {
acked = tcp_slow_start(tp, acked);
if (!acked)
return;
}
tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT),
acked);
}
static u32 tcp_scalable_ssthresh(struct sock *sk)
{
const struct tcp_sock *tp = tcp_sk(sk);
return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U);
}
static struct tcp_congestion_ops tcp_scalable __read_mostly = {
.ssthresh = tcp_scalable_ssthresh,
.undo_cwnd = tcp_reno_undo_cwnd,
.cong_avoid = tcp_scalable_cong_avoid,
.owner = THIS_MODULE,
.name = "scalable",
};
static int __init tcp_scalable_register(void)
{
return tcp_register_congestion_control(&tcp_scalable);
}
static void __exit tcp_scalable_unregister(void)
{
tcp_unregister_congestion_control(&tcp_scalable);
}
module_init(tcp_scalable_register);
module_exit(tcp_scalable_unregister);
MODULE_AUTHOR("John Heffner");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Scalable TCP");