Add the best master clock algorithm.

This commit also introduces clock and port objects, but only with the
minimal interface needed by the BMC.

Signed-off-by: Richard Cochran <[email protected]>

bmc.c

@@ -0,0 +1,148 @@
+/**
+ * @file bmc.c
+ * @note Copyright (C) 2011 Richard Cochran <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+#include <string.h>
+
+#include "bmc.h"
+#include "ds.h"
+
+#define A_BETTER  1
+#define B_BETTER -1
+
+static int dscmp2(struct dataset *a, struct dataset *b)
+{
+	int diff;
+	unsigned int A = a->stepsRemoved, B = b->stepsRemoved;
+
+	if (A + 1 < B)
+		return A_BETTER;
+	if (B + 1 < A)
+		return B_BETTER;
+	/*
+	 * We ignore the "error-1" conditions mentioned in the
+	 * standard, since there is nothing we can do about it anyway.
+	 */
+	if (A < B)
+		return A_BETTER;
+	if (A > B)
+		return B_BETTER;
+
+	diff = memcmp(&a->sender, &b->sender, sizeof(a->sender));
+	if (diff < 0)
+		return A_BETTER;
+	if (diff > 0)
+		return B_BETTER;
+
+	if (a->receiver.portNumber < b->receiver.portNumber)
+		return A_BETTER;
+	if (a->receiver.portNumber > b->receiver.portNumber)
+		return B_BETTER;
+	/*
+	 * If we got this far, it means "error-2" has occured.
+	 */
+	return 0;
+}
+
+int dscmp(struct dataset *a, struct dataset *b)
+{
+	int diff;
+
+	if (a == b)
+		return 0;
+	if (a && !b)
+		return A_BETTER;
+	if (b && !a)
+		return B_BETTER;
+
+	diff = memcmp(&a->identity, &b->identity, sizeof(a->identity));
+
+	if (!diff)
+		return dscmp2(a, b);
+
+	if (a->priority1 < b->priority1)
+		return A_BETTER;
+	if (a->priority1 > b->priority1)
+		return B_BETTER;
+
+	if (a->quality.clockClass < b->quality.clockClass)
+		return A_BETTER;
+	if (a->quality.clockClass > b->quality.clockClass)
+		return B_BETTER;
+
+	if (a->quality.clockAccuracy < b->quality.clockAccuracy)
+		return A_BETTER;
+	if (a->quality.clockAccuracy > b->quality.clockAccuracy)
+		return B_BETTER;
+
+	if (a->quality.offsetScaledLogVariance <
+	    b->quality.offsetScaledLogVariance)
+		return A_BETTER;
+	if (a->quality.offsetScaledLogVariance >
+	    b->quality.offsetScaledLogVariance)
+		return B_BETTER;
+
+	if (a->priority2 < b->priority2)
+		return A_BETTER;
+	if (a->priority2 > b->priority2)
+		return B_BETTER;
+
+	return diff < 0 ? A_BETTER : B_BETTER;
+}
+
+enum port_state bmc_state_decision(struct clock *c, struct port *r)
+{
+	struct dataset *clock_ds, *clock_best, *port_best;
+	enum port_state ps;
+
+	clock_ds = clock_default_ds(c);
+	clock_best = clock_best_foreign(c);
+	port_best = port_best_foreign(r);
+	ps = port_state(r);
+
+	if (!port_best) {
+		if (PS_LISTENING == ps)
+			return ps;
+		else
+			return PS_FAULTY;
+	}
+
+	if (!clock_best)
+		return PS_FAULTY;
+
+	if (clock_class(c) <= 127) {
+		if (dscmp(clock_ds, port_best) > 0) {
+			return PS_GRAND_MASTER; /*M1*/
+		} else {
+			return PS_PASSIVE; /*P1*/
+		}
+	}
+
+	if (dscmp(clock_ds, clock_best) > 0) {
+		return PS_GRAND_MASTER; /*M2*/
+	}
+
+	if (clock_best_port(c) == r) {
+		return PS_SLAVE; /*S1*/
+	}
+
+	if (dscmp(clock_best, port_best) > 0) {
+		return PS_PASSIVE; /*P2*/
+	} else {
+		return PS_MASTER; /*M3*/
+	}
+}

bmc.h

@@ -0,0 +1,45 @@
+/**
+ * @file bmc.h
+ * @brief Best master clock algorithm
+ * @note Copyright (C) 2011 Richard Cochran <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+#ifndef HAVE_BMC_H
+#define HAVE_BMC_H
+
+#include "clock.h"
+#include "port.h"
+#include "fsm.h"
+
+/**
+ * BMC state decision algorithm.
+ * @param c  The local clock.
+ * @param r  The port in question.
+ * @return   A @ref port_state value as the recommended state.
+ */
+enum port_state bmc_state_decision(struct clock *c, struct port *r);
+
+/**
+ * Compare two data sets.
+ * @param a A dataset to compare.
+ * @param b A dataset to compare.
+ * @return An integer less than, equal to, or greater than zero
+ *         if the dataset @a a is found, respectively, to be
+ *         less than, to match, or be greater than @a b.
+ */
+int dscmp(struct dataset *a, struct dataset *b);
+
+#endif

clock.h

@@ -0,0 +1,57 @@
+/**
+ * @file clock.h
+ * @note Copyright (C) 2011 Richard Cochran <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+#ifndef HAVE_CLOCK_H
+#define HAVE_CLOCK_H
+
+#include "ds.h"
+
+/** Opaque type. */
+struct clock;
+
+/**
+ * Obtains a reference to the best foreign master of a clock.
+ * @param c  The clock instance.
+ * @return   A pointer to the data set of the foreign master,
+ *           or NULL if none has been yet discovered.
+ */
+struct dataset *clock_best_foreign(struct clock *c);
+
+/**
+ * Obtains a reference to the port with the best foreign master.
+ * @param c  The clock instance.
+ * @return   A pointer to the port with the best foreign master,
+ *           or NULL if none has been yet discovered.
+ */
+struct port *clock_best_port(struct clock *c);
+
+/**
+ * Obtain the clockClass attribute from a clock.
+ * @param c  The clock instance.
+ * @return   The value of the clock's class.
+ */
+UInteger8 clock_class(struct clock *c);
+
+/**
+ * Obtains a clock's default data set.
+ * @param c  The clock instance.
+ * @return   A pointer to the data set of the clock.
+ */
+struct dataset *clock_default_ds(struct clock *c);
+
+#endif

makefile

@@ -24,7 +24,7 @@ CFLAGS	= -Wall $(INC) $(DEBUG)
 LDFLAGS	=
 LDLIBS	= -lm -lrt
 PRG	= linuxptp
-OBJ	= fsm.o phc.o print.o
+OBJ	= bmc.o fsm.o phc.o print.o
 
 SRC	= $(OBJ:.o=.c)
 DEPEND	= $(OBJ:.o=.d)

port.h

@@ -0,0 +1,41 @@
+/**
+ * @file port.h
+ * @note Copyright (C) 2011 Richard Cochran <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+#ifndef HAVE_PORT_H
+#define HAVE_PORT_H
+
+/** Opaque type. */
+struct port;
+
+/**
+ * Returns the dataset from a port's best foreign clock record, if any
+ * has yet been discovered.
+ *
+ * @param port  A port instance.
+ * @return      A pointer to a dataset, or NULL.
+ */
+struct dataset *port_best_foreign(struct port *port);
+
+/**
+ * Returns a port's current state.
+ * @param port  A port instance.
+ * @return      One of the @ref port_state values.
+ */
+enum port_state port_state(struct port *port);
+
+#endif