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Date: Tue, 5 Feb 2013 09:25:17 -0800
From: Stephen Hemminger <stephen@...workplumber.org>
To: David Miller <davem@...emloft.net>
Cc: netdev@...r.kernel.org
Subject: [PATCH] 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@...workplumber.org>
--- a/Documentation/networking/ip-sysctl.txt 2013-02-05 09:22:44.379791669 -0800
+++ b/Documentation/networking/ip-sysctl.txt 2013-02-05 09:23:13.035421064 -0800
@@ -130,17 +130,6 @@ somaxconn - INTEGER
Defaults to 128. See also tcp_max_syn_backlog for additional tuning
for TCP sockets.
-tcp_abc - INTEGER
- Controls Appropriate Byte Count (ABC) defined in RFC3465.
- ABC is a way of increasing congestion window (cwnd) more slowly
- in response to partial acknowledgments.
- Possible values are:
- 0 increase cwnd once per acknowledgment (no ABC)
- 1 increase cwnd once per acknowledgment of full sized segment
- 2 allow increase cwnd by two if acknowledgment is
- of two segments to compensate for delayed acknowledgments.
- Default: 0 (off)
-
tcp_abort_on_overflow - BOOLEAN
If listening service is too slow to accept new connections,
reset them. Default state is FALSE. It means that if overflow
--- a/include/net/tcp.h 2013-02-05 09:22:44.379791669 -0800
+++ b/include/net/tcp.h 2013-02-05 09:23:13.035421064 -0800
@@ -279,7 +279,6 @@ extern int sysctl_tcp_dma_copybreak;
extern int sysctl_tcp_nometrics_save;
extern int sysctl_tcp_moderate_rcvbuf;
extern int sysctl_tcp_tso_win_divisor;
-extern int sysctl_tcp_abc;
extern int sysctl_tcp_mtu_probing;
extern int sysctl_tcp_base_mss;
extern int sysctl_tcp_workaround_signed_windows;
--- a/kernel/sysctl_binary.c 2013-02-05 09:22:44.379791669 -0800
+++ b/kernel/sysctl_binary.c 2013-02-05 09:23:13.035421064 -0800
@@ -387,7 +387,6 @@ static const struct bin_table bin_net_ip
{ CTL_INT, NET_TCP_MODERATE_RCVBUF, "tcp_moderate_rcvbuf" },
{ CTL_INT, NET_TCP_TSO_WIN_DIVISOR, "tcp_tso_win_divisor" },
{ CTL_STR, NET_TCP_CONG_CONTROL, "tcp_congestion_control" },
- { CTL_INT, NET_TCP_ABC, "tcp_abc" },
{ CTL_INT, NET_TCP_MTU_PROBING, "tcp_mtu_probing" },
{ CTL_INT, NET_TCP_BASE_MSS, "tcp_base_mss" },
{ CTL_INT, NET_IPV4_TCP_WORKAROUND_SIGNED_WINDOWS, "tcp_workaround_signed_windows" },
--- a/net/ipv4/sysctl_net_ipv4.c 2013-02-05 09:22:49.035731453 -0800
+++ b/net/ipv4/sysctl_net_ipv4.c 2013-02-05 09:23:13.035421064 -0800
@@ -633,13 +633,6 @@ static struct ctl_table ipv4_table[] = {
.proc_handler = proc_tcp_congestion_control,
},
{
- .procname = "tcp_abc",
- .data = &sysctl_tcp_abc,
- .maxlen = sizeof(int),
- .mode = 0644,
- .proc_handler = proc_dointvec,
- },
- {
.procname = "tcp_mtu_probing",
.data = &sysctl_tcp_mtu_probing,
.maxlen = sizeof(int),
--- a/net/ipv4/tcp_cong.c 2013-02-05 09:22:44.379791669 -0800
+++ b/net/ipv4/tcp_cong.c 2013-02-05 09:23:13.035421064 -0800
@@ -311,26 +311,10 @@ void tcp_slow_start(struct tcp_sock *tp)
int cnt; /* increase in packets */
unsigned int delta = 0;
- /* 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 = tp->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;
@@ -372,20 +356,9 @@ void tcp_reno_cong_avoid(struct sock *sk
/* 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);
--- a/net/ipv4/tcp_input.c 2013-02-05 09:22:49.035731453 -0800
+++ b/net/ipv4/tcp_input.c 2013-02-05 09:23:13.039421013 -0800
@@ -98,7 +98,6 @@ int sysctl_tcp_frto_response __read_most
int sysctl_tcp_thin_dupack __read_mostly;
int sysctl_tcp_moderate_rcvbuf __read_mostly = 1;
-int sysctl_tcp_abc __read_mostly;
int sysctl_tcp_early_retrans __read_mostly = 2;
#define FLAG_DATA 0x01 /* Incoming frame contained data. */
@@ -3608,15 +3607,6 @@ static int tcp_ack(struct sock *sk, cons
if (after(ack, prior_snd_una))
flag |= FLAG_SND_UNA_ADVANCED;
- if (sysctl_tcp_abc) {
- if (icsk->icsk_ca_state < TCP_CA_CWR)
- tp->bytes_acked += ack - prior_snd_una;
- else if (icsk->icsk_ca_state == TCP_CA_Loss)
- /* we assume just one segment left network */
- tp->bytes_acked += min(ack - prior_snd_una,
- tp->mss_cache);
- }
-
prior_fackets = tp->fackets_out;
prior_in_flight = tcp_packets_in_flight(tp);
--
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