tcp: tcp_vegas ssthresh bugfix
This patch fixes ssthresh accounting issues in tcp_vegas when cwnd decreases
Signed-off-by: Doug Leith <doug.leith@nuim.ie>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_vegas.c b/net/ipv4/tcp_vegas.c
index a453aac..c6743ee 100644
--- a/net/ipv4/tcp_vegas.c
+++ b/net/ipv4/tcp_vegas.c
@@ -158,6 +158,11 @@
}
EXPORT_SYMBOL_GPL(tcp_vegas_cwnd_event);
+static inline u32 tcp_vegas_ssthresh(struct tcp_sock *tp)
+{
+ return min(tp->snd_ssthresh, tp->snd_cwnd-1);
+}
+
static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
{
struct tcp_sock *tp = tcp_sk(sk);
@@ -221,11 +226,10 @@
*/
diff = tp->snd_cwnd * (rtt-vegas->baseRTT) / vegas->baseRTT;
- if (diff > gamma && tp->snd_ssthresh > 2 ) {
+ if (diff > gamma && tp->snd_cwnd <= tp->snd_ssthresh) {
/* Going too fast. Time to slow down
* and switch to congestion avoidance.
*/
- tp->snd_ssthresh = 2;
/* Set cwnd to match the actual rate
* exactly:
@@ -235,6 +239,7 @@
* utilization.
*/
tp->snd_cwnd = min(tp->snd_cwnd, (u32)target_cwnd+1);
+ tp->snd_ssthresh = tcp_vegas_ssthresh(tp);
} else if (tp->snd_cwnd <= tp->snd_ssthresh) {
/* Slow start. */
@@ -250,6 +255,8 @@
* we slow down.
*/
tp->snd_cwnd--;
+ tp->snd_ssthresh
+ = tcp_vegas_ssthresh(tp);
} else if (diff < alpha) {
/* We don't have enough extra packets
* in the network, so speed up.