[TCP]: Remove TCP Compound

This reverts: f890f921040fef6a35e39d15b729af1fd1a35f29

The inclusion of TCP Compound needs to be reverted at this time
because it is not 100% certain that this code conforms to the
requirements of Developer's Certificate of Origin 1.1 paragraph (b).

Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 0 insertions, 459 deletions

diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
index da33393..8514106 100644
--- a/net/ipv4/Kconfig
+++ b/net/ipv4/Kconfig
@@ -572,16 +572,6 @@ config TCP_CONG_VENO
 	loss packets.
 	See http://www.ntu.edu.sg/home5/ZHOU0022/papers/CPFu03a.pdf
 
-config TCP_CONG_COMPOUND
-	tristate "TCP Compound"
-	depends on EXPERIMENTAL
-	default n
-	---help---
-	TCP Compound is a sender-side only change to TCP that uses
-	a mixed Reno/Vegas approach to calculate the cwnd.
-	For further details look here:
-	  ftp://ftp.research.microsoft.com/pub/tr/TR-2005-86.pdf
-
 endmenu
 
 config TCP_CONG_BIC
diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
index 38b8039..4878fc5 100644
--- a/net/ipv4/Makefile
+++ b/net/ipv4/Makefile
@@ -47,7 +47,6 @@ obj-$(CONFIG_TCP_CONG_VEGAS) += tcp_vegas.o
 obj-$(CONFIG_TCP_CONG_VENO) += tcp_veno.o
 obj-$(CONFIG_TCP_CONG_SCALABLE) += tcp_scalable.o
 obj-$(CONFIG_TCP_CONG_LP) += tcp_lp.o
-obj-$(CONFIG_TCP_CONG_COMPOUND) += tcp_compound.o
 
 obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \
 		      xfrm4_output.o
diff --git a/net/ipv4/tcp_compound.c b/net/ipv4/tcp_compound.c
deleted file mode 100644
index bc54f7e..0000000
--- a/net/ipv4/tcp_compound.c
+++ /dev/null
@@ -1,448 +0,0 @@
-/*
- * TCP Vegas congestion control
- *
- * This is based on the congestion detection/avoidance scheme described in
- *    Lawrence S. Brakmo and Larry L. Peterson.
- *    "TCP Vegas: End to end congestion avoidance on a global internet."
- *    IEEE Journal on Selected Areas in Communication, 13(8):1465--1480,
- *    October 1995. Available from:
- *	ftp://ftp.cs.arizona.edu/xkernel/Papers/jsac.ps
- *
- * See http://www.cs.arizona.edu/xkernel/ for their implementation.
- * The main aspects that distinguish this implementation from the
- * Arizona Vegas implementation are:
- *   o We do not change the loss detection or recovery mechanisms of
- *     Linux in any way. Linux already recovers from losses quite well,
- *     using fine-grained timers, NewReno, and FACK.
- *   o To avoid the performance penalty imposed by increasing cwnd
- *     only every-other RTT during slow start, we increase during
- *     every RTT during slow start, just like Reno.
- *   o Largely to allow continuous cwnd growth during slow start,
- *     we use the rate at which ACKs come back as the "actual"
- *     rate, rather than the rate at which data is sent.
- *   o To speed convergence to the right rate, we set the cwnd
- *     to achieve the right ("actual") rate when we exit slow start.
- *   o To filter out the noise caused by delayed ACKs, we use the
- *     minimum RTT sample observed during the last RTT to calculate
- *     the actual rate.
- *   o When the sender re-starts from idle, it waits until it has
- *     received ACKs for an entire flight of new data before making
- *     a cwnd adjustment decision. The original Vegas implementation
- *     assumed senders never went idle.
- *
- *
- *   TCP Compound based on TCP Vegas
- *
- *   further details can be found here:
- *      ftp://ftp.research.microsoft.com/pub/tr/TR-2005-86.pdf
- */
-
-#include <linux/config.h>
-#include <linux/mm.h>
-#include <linux/module.h>
-#include <linux/skbuff.h>
-#include <linux/inet_diag.h>
-
-#include <net/tcp.h>
-
-/* Default values of the Vegas variables, in fixed-point representation
- * with V_PARAM_SHIFT bits to the right of the binary point.
- */
-#define V_PARAM_SHIFT 1
-
-#define TCP_COMPOUND_ALPHA          3U
-#define TCP_COMPOUND_BETA           1U
-#define TCP_COMPOUND_GAMMA         30
-#define TCP_COMPOUND_ZETA           1
-
-/* TCP compound variables */
-struct compound {
-	u32 beg_snd_nxt;	/* right edge during last RTT */
-	u32 beg_snd_una;	/* left edge  during last RTT */
-	u32 beg_snd_cwnd;	/* saves the size of the cwnd */
-	u8 doing_vegas_now;	/* if true, do vegas for this RTT */
-	u16 cntRTT;		/* # of RTTs measured within last RTT */
-	u32 minRTT;		/* min of RTTs measured within last RTT (in usec) */
-	u32 baseRTT;		/* the min of all Vegas RTT measurements seen (in usec) */
-
-	u32 cwnd;
-	u32 dwnd;
-};
-
-/* There are several situations when we must "re-start" Vegas:
- *
- *  o when a connection is established
- *  o after an RTO
- *  o after fast recovery
- *  o when we send a packet and there is no outstanding
- *    unacknowledged data (restarting an idle connection)
- *
- * In these circumstances we cannot do a Vegas calculation at the
- * end of the first RTT, because any calculation we do is using
- * stale info -- both the saved cwnd and congestion feedback are
- * stale.
- *
- * Instead we must wait until the completion of an RTT during
- * which we actually receive ACKs.
- */
-static inline void vegas_enable(struct sock *sk)
-{
-	const struct tcp_sock *tp = tcp_sk(sk);
-	struct compound *vegas = inet_csk_ca(sk);
-
-	/* Begin taking Vegas samples next time we send something. */
-	vegas->doing_vegas_now = 1;
-
-	/* Set the beginning of the next send window. */
-	vegas->beg_snd_nxt = tp->snd_nxt;
-
-	vegas->cntRTT = 0;
-	vegas->minRTT = 0x7fffffff;
-}
-
-/* Stop taking Vegas samples for now. */
-static inline void vegas_disable(struct sock *sk)
-{
-	struct compound *vegas = inet_csk_ca(sk);
-
-	vegas->doing_vegas_now = 0;
-}
-
-static void tcp_compound_init(struct sock *sk)
-{
-	struct compound *vegas = inet_csk_ca(sk);
-	const struct tcp_sock *tp = tcp_sk(sk);
-
-	vegas->baseRTT = 0x7fffffff;
-	vegas_enable(sk);
-
-	vegas->dwnd = 0;
-	vegas->cwnd = tp->snd_cwnd;
-}
-
-/* Do RTT sampling needed for Vegas.
- * Basically we:
- *   o min-filter RTT samples from within an RTT to get the current
- *     propagation delay + queuing delay (we are min-filtering to try to
- *     avoid the effects of delayed ACKs)
- *   o min-filter RTT samples from a much longer window (forever for now)
- *     to find the propagation delay (baseRTT)
- */
-static void tcp_compound_rtt_calc(struct sock *sk, u32 usrtt)
-{
-	struct compound *vegas = inet_csk_ca(sk);
-	u32 vrtt = usrtt + 1;	/* Never allow zero rtt or baseRTT */
-
-	/* Filter to find propagation delay: */
-	if (vrtt < vegas->baseRTT)
-		vegas->baseRTT = vrtt;
-
-	/* Find the min RTT during the last RTT to find
-	 * the current prop. delay + queuing delay:
-	 */
-
-	vegas->minRTT = min(vegas->minRTT, vrtt);
-	vegas->cntRTT++;
-}
-
-static void tcp_compound_state(struct sock *sk, u8 ca_state)
-{
-
-	if (ca_state == TCP_CA_Open)
-		vegas_enable(sk);
-	else
-		vegas_disable(sk);
-}
-
-
-/* 64bit divisor, dividend and result. dynamic precision */
-static inline u64 div64_64(u64 dividend, u64 divisor)
-{
-	u32 d = divisor;
-
-	if (divisor > 0xffffffffULL) {
-		unsigned int shift = fls(divisor >> 32);
-
-		d = divisor >> shift;
-		dividend >>= shift;
-	}
-
-	/* avoid 64 bit division if possible */
-	if (dividend >> 32)
-		do_div(dividend, d);
-	else
-		dividend = (u32) dividend / d;
-
-	return dividend;
-}
-
-/* calculate the quartic root of "a" using Newton-Raphson */
-static u32 qroot(u64 a)
-{
-	u32 x, x1;
-
-	/* Initial estimate is based on:
-	 * qrt(x) = exp(log(x) / 4)
-	 */
-	x = 1u << (fls64(a) >> 2);
-
-	/*
-	 * Iteration based on:
-	 *                         3
-	 * x    = ( 3 * x  +  a / x  ) / 4
-	 *  k+1          k         k
-	 */
-	do {
-		u64 x3 = x;
-
-		x1 = x;
-		x3 *= x;
-		x3 *= x;
-
-		x = (3 * x + (u32) div64_64(a, x3)) / 4;
-	} while (abs(x1 - x) > 1);
-
-	return x;
-}
-
-
-/*
- * If the connection is idle and we are restarting,
- * then we don't want to do any Vegas calculations
- * until we get fresh RTT samples.  So when we
- * restart, we reset our Vegas state to a clean
- * slate. After we get acks for this flight of
- * packets, _then_ we can make Vegas calculations
- * again.
- */
-static void tcp_compound_cwnd_event(struct sock *sk, enum tcp_ca_event event)
-{
-	if (event == CA_EVENT_CWND_RESTART || event == CA_EVENT_TX_START)
-		tcp_compound_init(sk);
-}
-
-static void tcp_compound_cong_avoid(struct sock *sk, u32 ack,
-				    u32 seq_rtt, u32 in_flight, int flag)
-{
-	struct tcp_sock *tp = tcp_sk(sk);
-	struct compound *vegas = inet_csk_ca(sk);
-	u8 inc = 0;
-
-	if (vegas->cwnd + vegas->dwnd > tp->snd_cwnd) {
-		if (vegas->cwnd > tp->snd_cwnd || vegas->dwnd > tp->snd_cwnd) {
-			vegas->cwnd = tp->snd_cwnd;
-			vegas->dwnd = 0;
-		} else
-			vegas->cwnd = tp->snd_cwnd - vegas->dwnd;
-
-	}
-
-	if (!tcp_is_cwnd_limited(sk, in_flight))
-		return;
-
-	if (vegas->cwnd <= tp->snd_ssthresh)
-		inc = 1;
-	else if (tp->snd_cwnd_cnt < tp->snd_cwnd)
-		tp->snd_cwnd_cnt++;
-
-	if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
-		inc = 1;
-		tp->snd_cwnd_cnt = 0;
-	}
-
-	if (inc && tp->snd_cwnd < tp->snd_cwnd_clamp)
-		vegas->cwnd++;
-
-	/* The key players are v_beg_snd_una and v_beg_snd_nxt.
-	 *
-	 * These are so named because they represent the approximate values
-	 * of snd_una and snd_nxt at the beginning of the current RTT. More
-	 * precisely, they represent the amount of data sent during the RTT.
-	 * At the end of the RTT, when we receive an ACK for v_beg_snd_nxt,
-	 * we will calculate that (v_beg_snd_nxt - v_beg_snd_una) outstanding
-	 * bytes of data have been ACKed during the course of the RTT, giving
-	 * an "actual" rate of:
-	 *
-	 *     (v_beg_snd_nxt - v_beg_snd_una) / (rtt duration)
-	 *
-	 * Unfortunately, v_beg_snd_una is not exactly equal to snd_una,
-	 * because delayed ACKs can cover more than one segment, so they
-	 * don't line up nicely with the boundaries of RTTs.
-	 *
-	 * Another unfortunate fact of life is that delayed ACKs delay the
-	 * advance of the left edge of our send window, so that the number
-	 * of bytes we send in an RTT is often less than our cwnd will allow.
-	 * So we keep track of our cwnd separately, in v_beg_snd_cwnd.
-	 */
-
-	if (after(ack, vegas->beg_snd_nxt)) {
-		/* Do the Vegas once-per-RTT cwnd adjustment. */
-		u32 old_wnd, old_snd_cwnd;
-
-		/* Here old_wnd is essentially the window of data that was
-		 * sent during the previous RTT, and has all
-		 * been acknowledged in the course of the RTT that ended
-		 * with the ACK we just received. Likewise, old_snd_cwnd
-		 * is the cwnd during the previous RTT.
-		 */
-		if (!tp->mss_cache)
-			return;
-
-		old_wnd = (vegas->beg_snd_nxt - vegas->beg_snd_una) /
-		    tp->mss_cache;
-		old_snd_cwnd = vegas->beg_snd_cwnd;
-
-		/* Save the extent of the current window so we can use this
-		 * at the end of the next RTT.
-		 */
-		vegas->beg_snd_una = vegas->beg_snd_nxt;
-		vegas->beg_snd_nxt = tp->snd_nxt;
-		vegas->beg_snd_cwnd = tp->snd_cwnd;
-
-		/* We do the Vegas calculations only if we got enough RTT
-		 * samples that we can be reasonably sure that we got
-		 * at least one RTT sample that wasn't from a delayed ACK.
-		 * If we only had 2 samples total,
-		 * then that means we're getting only 1 ACK per RTT, which
-		 * means they're almost certainly delayed ACKs.
-		 * If  we have 3 samples, we should be OK.
-		 */
-
-		if (vegas->cntRTT > 2) {
-			u32 rtt, target_cwnd, diff;
-			u32 brtt, dwnd;
-
-			/* We have enough RTT samples, so, using the Vegas
-			 * algorithm, we determine if we should increase or
-			 * decrease cwnd, and by how much.
-			 */
-
-			/* Pluck out the RTT we are using for the Vegas
-			 * calculations. This is the min RTT seen during the
-			 * last RTT. Taking the min filters out the effects
-			 * of delayed ACKs, at the cost of noticing congestion
-			 * a bit later.
-			 */
-			rtt = vegas->minRTT;
-
-			/* Calculate the cwnd we should have, if we weren't
-			 * going too fast.
-			 *
-			 * This is:
-			 *     (actual rate in segments) * baseRTT
-			 * We keep it as a fixed point number with
-			 * V_PARAM_SHIFT bits to the right of the binary point.
-			 */
-			if (!rtt)
-				return;
-
-			brtt = vegas->baseRTT;
-			target_cwnd = ((old_wnd * brtt)
-				       << V_PARAM_SHIFT) / rtt;
-
-			/* Calculate the difference between the window we had,
-			 * and the window we would like to have. This quantity
-			 * is the "Diff" from the Arizona Vegas papers.
-			 *
-			 * Again, this is a fixed point number with
-			 * V_PARAM_SHIFT bits to the right of the binary
-			 * point.
-			 */
-
-			diff = (old_wnd << V_PARAM_SHIFT) - target_cwnd;
-
-			dwnd = vegas->dwnd;
-
-			if (diff < (TCP_COMPOUND_GAMMA << V_PARAM_SHIFT)) {
-				u64 v;
-				u32 x;
-
-				/*
-				 * The TCP Compound paper describes the choice
-				 * of "k" determines the agressiveness,
-				 * ie. slope of the response function.
-				 *
-				 * For same value as HSTCP would be 0.8
-				 * but for computaional reasons, both the
-				 * original authors and this implementation
-				 * use 0.75.
-				 */
-				v = old_wnd;
-				x = qroot(v * v * v) >> TCP_COMPOUND_ALPHA;
-				if (x > 1)
-					dwnd = x - 1;
-				else
-					dwnd = 0;
-
-				dwnd += vegas->dwnd;
-
-			} else if ((dwnd << V_PARAM_SHIFT) <
-				   (diff * TCP_COMPOUND_BETA))
-				dwnd = 0;
-			else
-				dwnd =
-				    ((dwnd << V_PARAM_SHIFT) -
-				     (diff *
-				      TCP_COMPOUND_BETA)) >> V_PARAM_SHIFT;
-
-			vegas->dwnd = dwnd;
-
-		}
-
-		/* Wipe the slate clean for the next RTT. */
-		vegas->cntRTT = 0;
-		vegas->minRTT = 0x7fffffff;
-	}
-
-	tp->snd_cwnd = vegas->cwnd + vegas->dwnd;
-}
-
-/* Extract info for Tcp socket info provided via netlink. */
-static void tcp_compound_get_info(struct sock *sk, u32 ext, struct sk_buff *skb)
-{
-	const struct compound *ca = inet_csk_ca(sk);
-	if (ext & (1 << (INET_DIAG_VEGASINFO - 1))) {
-		struct tcpvegas_info *info;
-
-		info = RTA_DATA(__RTA_PUT(skb, INET_DIAG_VEGASINFO,
-					  sizeof(*info)));
-
-		info->tcpv_enabled = ca->doing_vegas_now;
-		info->tcpv_rttcnt = ca->cntRTT;
-		info->tcpv_rtt = ca->baseRTT;
-		info->tcpv_minrtt = ca->minRTT;
-	rtattr_failure:;
-	}
-}
-
-static struct tcp_congestion_ops tcp_compound = {
-	.init		= tcp_compound_init,
-	.ssthresh	= tcp_reno_ssthresh,
-	.cong_avoid	= tcp_compound_cong_avoid,
-	.rtt_sample	= tcp_compound_rtt_calc,
-	.set_state	= tcp_compound_state,
-	.cwnd_event	= tcp_compound_cwnd_event,
-	.get_info	= tcp_compound_get_info,
-
-	.owner		= THIS_MODULE,
-	.name		= "compound",
-};
-
-static int __init tcp_compound_register(void)
-{
-	BUG_ON(sizeof(struct compound) > ICSK_CA_PRIV_SIZE);
-	tcp_register_congestion_control(&tcp_compound);
-	return 0;
-}
-
-static void __exit tcp_compound_unregister(void)
-{
-	tcp_unregister_congestion_control(&tcp_compound);
-}
-
-module_init(tcp_compound_register);
-module_exit(tcp_compound_unregister);
-
-MODULE_AUTHOR("Angelo P. Castellani, Stephen Hemminger");
-MODULE_LICENSE("GPL");
-MODULE_DESCRIPTION("TCP Compound");