[TCP]: Fix snd_cwnd adjustments in tcp_highspeed.c
Xiaoliang (David) Wei wrote:
> Hi gurus,
>
> I am reading the code of tcp_highspeed.c in the kernel and have a
> question on the hstcp_cong_avoid function, specifically the following
> AI part (line 136~143 in net/ipv4/tcp_highspeed.c ):
>
> /* Do additive increase */
> if (tp->snd_cwnd < tp->snd_cwnd_clamp) {
> tp->snd_cwnd_cnt += ca->ai;
> if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
> tp->snd_cwnd++;
> tp->snd_cwnd_cnt -= tp->snd_cwnd;
> }
> }
>
> In this part, when (tp->snd_cwnd_cnt == tp->snd_cwnd),
> snd_cwnd_cnt will be -1... snd_cwnd_cnt is defined as u16, will this
> small chance of getting -1 becomes a problem?
> Shall we change it by reversing the order of the cwnd++ and cwnd_cnt -=
> cwnd?
Absolutely correct. Thanks.
Signed-off-by: John Heffner <jheffner@psc.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_highspeed.c b/net/ipv4/tcp_highspeed.c
index e0e9d13..b72fa55 100644
--- a/net/ipv4/tcp_highspeed.c
+++ b/net/ipv4/tcp_highspeed.c
@@ -137,8 +137,8 @@
if (tp->snd_cwnd < tp->snd_cwnd_clamp) {
tp->snd_cwnd_cnt += ca->ai;
if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
- tp->snd_cwnd++;
tp->snd_cwnd_cnt -= tp->snd_cwnd;
+ tp->snd_cwnd++;
}
}
}
