tcp: remove Appropriate Byte Count support

TCP Appropriate Byte Count was added by me, but later disabled.
There is no point in maintaining it since it is a potential source
of bugs and Linux already implements other better window protection
heuristics.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 29 deletions

diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index cdf2e707bb10..019c2389a341 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -317,28 +317,11 @@ void tcp_slow_start(struct tcp_sock *tp)
 		snd_cwnd = 1U;
 	}
 
-	/* RFC3465: ABC Slow start
-	 * Increase only after a full MSS of bytes is acked
-	 *
-	 * TCP sender SHOULD increase cwnd by the number of
-	 * previously unacknowledged bytes ACKed by each incoming
-	 * acknowledgment, provided the increase is not more than L
-	 */
-	if (sysctl_tcp_abc && tp->bytes_acked < tp->mss_cache)
-		return;
-
 	if (sysctl_tcp_max_ssthresh > 0 && tp->snd_cwnd > sysctl_tcp_max_ssthresh)
 		cnt = sysctl_tcp_max_ssthresh >> 1;	/* limited slow start */
 	else
 		cnt = snd_cwnd;				/* exponential increase */
 
-	/* RFC3465: ABC
-	 * 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;
-
 	tp->snd_cwnd_cnt += cnt;
 	while (tp->snd_cwnd_cnt >= snd_cwnd) {
 		tp->snd_cwnd_cnt -= snd_cwnd;
@@ -378,20 +361,9 @@ void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
 	/* In "safe" area, increase. */
 	if (tp->snd_cwnd <= tp->snd_ssthresh)
 		tcp_slow_start(tp);
-
 	/* In dangerous area, increase slowly. */
-	else if (sysctl_tcp_abc) {
-		/* RFC3465: Appropriate Byte Count
-		 * increase once for each full cwnd acked
-		 */
-		if (tp->bytes_acked >= tp->snd_cwnd*tp->mss_cache) {
-			tp->bytes_acked -= tp->snd_cwnd*tp->mss_cache;
-			if (tp->snd_cwnd < tp->snd_cwnd_clamp)
-				tp->snd_cwnd++;
-		}
-	} else {
+	else
 		tcp_cong_avoid_ai(tp, tp->snd_cwnd);
-	}
 }
 EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid);