[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>
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index 34ae3f1..ccd8840 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -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 @@
/*
- * 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 @@
*/
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);