Import the ERTT (Enhanced Round Trip Time) Khelp module. ERTT uses the

Khelp/Hhook KPIs to hook into the TCP stack and maintain a per-connection, low
noise estimate of the instantaneous RTT. ERTT's implementation is robust even in
the face of delayed acknowledgements and/or TSO being in use for a connection.

A high quality, low noise RTT estimate is a requirement for applications such as
delay-based congestion control, for which we will be importing some algorithm
implementations shortly.

In collaboration with:	David Hayes <dahayes at swin edu au> and
				Grenville Armitage <garmitage at swin edu au>
Sponsored by:	FreeBSD Foundation
Reviewed by:	bz and others along the way
MFC after:	3 months

1 files changed, 89 insertions, 0 deletions

diff --git a/sys/netinet/khelp/h_ertt.h b/sys/netinet/khelp/h_ertt.h
new file mode 100644
index 0000000..8051a6c
--- /dev/null
+++ b/sys/netinet/khelp/h_ertt.h
@@ -0,0 +1,89 @@
+/*-
+ * Copyright (c) 2009-2010
+ * 	Swinburne University of Technology, Melbourne, Australia
+ * Copyright (c) 2010 Lawrence Stewart <lstewart@freebsd.org>
+ * All rights reserved.
+ *
+ * This software was developed at the Centre for Advanced Internet
+ * Architectures, Swinburne University, by David Hayes, made possible in part by
+ * a grant from the Cisco University Research Program Fund at Community
+ * Foundation Silicon Valley.
+ *
+ * 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.
+ *
+ * $FreeBSD$
+ */
+
+/*
+ * The ERTT (Enhanced Round Trip Time) Khelp module calculates an estimate of
+ * the instantaneous TCP RTT which, for example, is used by delay-based
+ * congestion control schemes. When the module is loaded, ERTT data is
+ * calculated for each active TCP connection and encapsulated within a
+ * "struct ertt".
+ *
+ * This software was first released in 2010 by David Hayes and Lawrence Stewart
+ * whilst working on the NewTCP research project at Swinburne University's
+ * Centre for Advanced Internet Architectures, Melbourne, Australia, which was
+ * made possible in part by a grant from the Cisco University Research Program
+ * Fund at Community Foundation Silicon Valley. Testing and development was
+ * further assisted by a grant from the FreeBSD Foundation. More details are
+ * available at:
+ *   http://caia.swin.edu.au/urp/newtcp/
+ */
+
+#ifndef	_NETINET_KHELP_H_ERTT_
+#define	_NETINET_KHELP_H_ERTT_
+
+struct txseginfo;
+
+/* Structure used as the ertt data block. */
+struct ertt {
+	/* Information about transmitted segments to aid in RTT calculation. */
+	TAILQ_HEAD(txseginfo_head, txseginfo) txsegi_q;
+	/* Bytes TX so far in marked RTT. */
+	long		bytes_tx_in_rtt;
+	/* Final version of above. */
+	long		bytes_tx_in_marked_rtt;
+	/* cwnd for marked RTT. */
+	unsigned long	marked_snd_cwnd;
+	/* Per-packet measured RTT. */
+	int		rtt;
+	/* Maximum RTT measured. */
+	int		maxrtt;
+	/* Minimum RTT measured. */
+	int		minrtt;
+	/* Guess if the receiver is using delayed ack. */
+	int		dlyack_rx;
+	/* Keep track of inconsistencies in packet timestamps. */
+	int		timestamp_errors;
+	/* RTT for a marked packet. */
+	int		markedpkt_rtt;
+	/* Flags to signal conditions between hook function calls. */
+	uint32_t	flags;
+};
+
+/* Flags for struct ertt. */
+#define	ERTT_NEW_MEASUREMENT		0x01
+#define	ERTT_MEASUREMENT_IN_PROGRESS	0x02
+#define	ERTT_TSO_DISABLED		0x04
+
+#endif /* _NETINET_KHELP_H_ERTT_ */