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tcp: Fix tcp_hybla zero congestion window growth with small rho and large cwnd.

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Because of rounding, in certain conditions, i.e. when in congestion
avoidance state rho is smaller than 1/128 of the current cwnd, TCP
Hybla congestion control starves and the cwnd is kept constant
forever.

This patch forces an increment by one segment after #send_cwnd calls
without increments(newreno behavior).

Signed-off-by: Daniele Lacamera <root@danielinux.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Daniele Lacamera 2008-10-07 15:58:17 -07:00 committed by David S. Miller
parent 58ec3b4db9
commit 9d2c27e17b
1 changed files with 5 additions and 1 deletions
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6
net/ipv4/tcp_hybla.c
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@ -150,7 +150,11 @@ static void hybla_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
ca->snd_cwnd_cents -= 128; ca->snd_cwnd_cents -= 128;
tp->snd_cwnd_cnt = 0; tp->snd_cwnd_cnt = 0;
} }
/* check when cwnd has not been incremented for a while */
if (increment == 0 && odd == 0 && tp->snd_cwnd_cnt >= tp->snd_cwnd) {
tp->snd_cwnd++;
tp->snd_cwnd_cnt = 0;
}
/* clamp down slowstart cwnd to ssthresh value. */ /* clamp down slowstart cwnd to ssthresh value. */
if (is_slowstart) if (is_slowstart)
tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);