OS-7329 Want pluggable TCP congestion control algorithms

Reviewed by: Dan McDonald <danmcd@joyent.com>
Reviewed by: Robert Mustacchi <robert.mustacchi@joyent.com>
Approved by: Robert Mustacchi <robert.mustacchi@joyent.com>

1 files changed, 222 insertions, 0 deletions

diff --git a/usr/src/uts/common/inet/cc/cc_cubic.h b/usr/src/uts/common/inet/cc/cc_cubic.h
new file mode 100644
index 0000000000..c87751d257
--- /dev/null
+++ b/usr/src/uts/common/inet/cc/cc_cubic.h
@@ -0,0 +1,222 @@
+/*
+ * Copyright (c) 2008-2010 Lawrence Stewart <lstewart@freebsd.org>
+ * Copyright (c) 2010 The FreeBSD Foundation
+ * All rights reserved.
+ * Copyright (c) 2017 by Delphix. All rights reserved.
+ * Copyright 2019 Joyent, Inc.
+ *
+ * This software was developed by Lawrence Stewart while studying at the Centre
+ * for Advanced Internet Architectures, Swinburne University of Technology, made
+ * possible in part by a grant from the Cisco University Research Program Fund
+ * at Community Foundation Silicon Valley.
+ *
+ * Portions of this software were developed at the Centre for Advanced
+ * Internet Architectures, Swinburne University of Technology, Melbourne,
+ * Australia by David Hayes under sponsorship from the FreeBSD Foundation.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef _NETINET_CC_CUBIC_H_
+#define	_NETINET_CC_CUBIC_H_
+
+/* Number of bits of precision for fixed point math calcs. */
+#define	CUBIC_SHIFT		8
+
+#define	CUBIC_SHIFT_4		32
+
+/* 0.5 << CUBIC_SHIFT. */
+#define	RENO_BETA		128
+
+/* ~0.8 << CUBIC_SHIFT. */
+#define	CUBIC_BETA		204
+
+/* ~0.2 << CUBIC_SHIFT. */
+#define	ONE_SUB_CUBIC_BETA	51
+
+/* 3 * ONE_SUB_CUBIC_BETA. */
+#define	THREE_X_PT2		153
+
+/* (2 << CUBIC_SHIFT) - ONE_SUB_CUBIC_BETA. */
+#define	TWO_SUB_PT2		461
+
+/* ~0.4 << CUBIC_SHIFT. */
+#define	CUBIC_C_FACTOR		102
+
+/* CUBIC fast convergence factor: ~0.9 << CUBIC_SHIFT. */
+#define	CUBIC_FC_FACTOR		230
+
+/* Don't trust s_rtt until this many rtt samples have been taken. */
+#define	CUBIC_MIN_RTT_SAMPLES	8
+
+/* Userland only bits. */
+#ifndef _KERNEL
+
+extern int hz;
+
+/*
+ * Implementation based on the formulae found in the CUBIC Internet Draft
+ * "draft-rhee-tcpm-cubic-02".
+ *
+ * Note BETA used in cc_cubic is equal to (1-beta) in the I-D
+ */
+
+static __inline float
+theoretical_cubic_k(double wmax_pkts)
+{
+	double C;
+
+	C = 0.4;
+
+	return (pow((wmax_pkts * 0.2) / C, (1.0 / 3.0)) * pow(2, CUBIC_SHIFT));
+}
+
+static __inline uint32_t
+theoretical_cubic_cwnd(int ticks_since_cong, uint32_t wmax, uint32_t smss)
+{
+	double C, wmax_pkts;
+
+	C = 0.4;
+	wmax_pkts = wmax / (double)smss;
+
+	return (smss * (wmax_pkts +
+	    (C * pow(ticks_since_cong / (double)hz -
+	    theoretical_cubic_k(wmax_pkts) / pow(2, CUBIC_SHIFT), 3.0))));
+}
+
+static __inline uint32_t
+theoretical_reno_cwnd(int ticks_since_cong, int rtt_ticks, uint32_t wmax,
+    uint32_t smss)
+{
+
+	return ((wmax * 0.5) + ((ticks_since_cong / (float)rtt_ticks) * smss));
+}
+
+static __inline uint32_t
+theoretical_tf_cwnd(int ticks_since_cong, int rtt_ticks, unsigned long wmax,
+    uint32_t smss)
+{
+
+	return ((wmax * 0.8) + ((3 * 0.2) / (2 - 0.2) *
+	    (ticks_since_cong / (float)rtt_ticks) * smss));
+}
+
+#endif /* !_KERNEL */
+
+/*
+ * Compute the CUBIC K value used in the cwnd calculation, using an
+ * implementation of eqn 2 in the I-D. The method used
+ * here is adapted from Apple Computer Technical Report #KT-32.
+ */
+static __inline int64_t
+cubic_k(uint32_t wmax_pkts)
+{
+	int64_t s, K;
+	uint16_t p;
+
+	K = s = 0;
+	p = 0;
+
+	/* (wmax * beta)/C with CUBIC_SHIFT worth of precision. */
+	s = ((wmax_pkts * ONE_SUB_CUBIC_BETA) << CUBIC_SHIFT) / CUBIC_C_FACTOR;
+
+	/* Rebase s to be between 1 and 1/8 with a shift of CUBIC_SHIFT. */
+	while (s >= 256) {
+		s >>= 3;
+		p++;
+	}
+
+	/*
+	 * Some magic constants taken from the Apple TR with appropriate
+	 * shifts: 275 == 1.072302 << CUBIC_SHIFT, 98 == 0.3812513 <<
+	 * CUBIC_SHIFT, 120 == 0.46946116 << CUBIC_SHIFT.
+	 */
+	K = (((s * 275) >> CUBIC_SHIFT) + 98) -
+	    (((s * s * 120) >> CUBIC_SHIFT) >> CUBIC_SHIFT);
+
+	/* Multiply by 2^p to undo the rebasing of s from above. */
+	return (K <<= p);
+}
+
+/*
+ * Compute the new cwnd value using an implementation of eqn 1 from the I-D.
+ * Thanks to Kip Macy for help debugging this function.
+ *
+ * XXXLAS: Characterise bounds for overflow.
+ */
+static __inline uint32_t
+cubic_cwnd(hrtime_t nsecs_since_cong, uint32_t wmax, uint32_t smss, int64_t K)
+{
+	int64_t t, cwnd;
+
+	/*
+	 * Convert nsecs_since_cong to milliseconds, with CUBIC_SHIFT worth
+	 * of precision.
+	 */
+	t = NSEC2MSEC(nsecs_since_cong << CUBIC_SHIFT);
+
+	/*
+	 * K is the time period in seconds that it will take to reach wmax. The
+	 * value is kept in fixed point form with CUBIC_SHIFT worth of
+	 * precision.
+	 *
+	 * For comparison with t, we convert K to milliseconds, and then convert
+	 * the result back to seconds.
+	 *
+	 * cwnd = t - K, with CUBIC_SHIFT worth of precision.
+	 */
+	cwnd = (t - K * MILLISEC) / MILLISEC;
+
+	/* cwnd = (t - K)^3, with CUBIC_SHIFT^3 worth of precision. */
+	cwnd *= (cwnd * cwnd);
+
+	/*
+	 * C(t - K)^3 + wmax
+	 * The down shift by CUBIC_SHIFT_4 is because cwnd has 4 lots of
+	 * CUBIC_SHIFT included in the value. 3 from the cubing of cwnd above,
+	 * and an extra from multiplying through by CUBIC_C_FACTOR.
+	 */
+	cwnd = ((cwnd * CUBIC_C_FACTOR * smss) >> CUBIC_SHIFT_4) + wmax;
+
+	return ((uint32_t)cwnd);
+}
+
+/*
+ * Compute an approximation of the "TCP friendly" cwnd some number of
+ * nanoseconds after a congestion event that is designed to yield the same
+ * average cwnd as NewReno while using CUBIC's beta of 0.8. RTT should be the
+ * average RTT estimate for the path measured over the previous congestion
+ * epoch and wmax is the value of cwnd at the last congestion event.
+ */
+static __inline uint32_t
+tf_cwnd(hrtime_t nsecs_since_cong, hrtime_t rtt_nsecs, uint32_t wmax,
+    uint32_t smss)
+{
+
+	/* Equation 4 of I-D. */
+	return (((wmax * CUBIC_BETA) + (((THREE_X_PT2 * nsecs_since_cong *
+	    smss) << CUBIC_SHIFT) / TWO_SUB_PT2 / rtt_nsecs)) >> CUBIC_SHIFT);
+}
+
+#endif /* _NETINET_CC_CUBIC_H_ */