Introduce the maxStepsRemoved attribute

Add attribute maxStepsRemoved which is included in IEEE1588-2017 (v2.1)
It is an optional attribute which can decide if an Announce message is
considered in the operation of the BMCA or not.

Signed-off-by: Anders Selhammer <anders.selhammer@est.tech>

clock.c

@@ -106,6 +106,7 @@ struct clock {
 	int utc_offset;
 	int time_flags;  /* grand master role */
 	int time_source; /* grand master role */
+	UInteger8 max_steps_removed;
 	enum servo_state servo_state;
 	enum timestamp_type timestamping;
 	tmv_t master_offset;
@@ -930,6 +931,7 @@ struct clock *clock_create(enum clock_type type, struct config *config,
 	}
 	c->default_dataset.localPriority =
 		config_get_int(config, NULL, "G.8275.defaultDS.localPriority");
+	c->max_steps_removed = config_get_int(config, NULL,"maxStepsRemoved");
 
 	/* Harmonize the twoStepFlag with the time_stamping option. */
 	if (config_harmonize_onestep(config)) {
@@ -1564,6 +1566,11 @@ int clock_slave_only(struct clock *c)
 	return c->dds.flags & DDS_SLAVE_ONLY;
 }
 
+UInteger8 clock_max_steps_removed(struct clock *c)
+{
+	return c->max_steps_removed;
+}
+
 UInteger16 clock_steps_removed(struct clock *c)
 {
 	return c->cur.stepsRemoved;

clock.h

@@ -260,6 +260,13 @@ int clock_poll(struct clock *c);
  */
 int clock_slave_only(struct clock *c);
 
+/**
+ * Obtain the max steps removed field from a clock's default data set.
+ * @param c  The clock instance.
+ * @return   The value of the clock's max steps removed field.
+ */
+UInteger8 clock_max_steps_removed(struct clock *c);
+
 /**
  * Obtain the steps removed field from a clock's current data set.
  * @param c  The clock instance.

config.c

@@ -235,6 +235,7 @@ struct config_item config_tab[] = {
 	PORT_ITEM_INT("logSyncInterval", 0, INT8_MIN, INT8_MAX),
 	GLOB_ITEM_INT("logging_level", LOG_INFO, PRINT_LEVEL_MIN, PRINT_LEVEL_MAX),
 	PORT_ITEM_INT("masterOnly", 0, 0, 1),
+	GLOB_ITEM_INT("maxStepsRemoved", 255, 2, UINT8_MAX),
 	GLOB_ITEM_STR("message_tag", NULL),
 	GLOB_ITEM_STR("manufacturerIdentity", "00:00:00"),
 	GLOB_ITEM_INT("max_frequency", 900000000, 0, INT_MAX),

configs/G.8275.1.cfg

@@ -7,5 +7,6 @@
 [global]
 dataset_comparison		G.8275.x
 G.8275.defaultDS.localPriority	128
+maxStepsRemoved			255
 masterOnly			0
 G.8275.portDS.localPriority	128

configs/G.8275.2.cfg

@@ -7,6 +7,7 @@
 [global]
 dataset_comparison		G.8275.x
 G.8275.defaultDS.localPriority	128
+maxStepsRemoved			255
 masterOnly			0
 G.8275.portDS.localPriority	128
 hybrid_e2e			1

configs/default.cfg

@@ -17,6 +17,7 @@ dscp_event		0
 dscp_general		0
 dataset_comparison	ieee1588
 G.8275.defaultDS.localPriority	128
+maxStepsRemoved		255
 #
 # Port Data Set
 #

port.c

@@ -1711,10 +1711,7 @@ int process_announce(struct port *p, struct ptp_message *m)
 {
 	int result = 0;
 
-	/* Do not qualify announce messages with stepsRemoved >= 255, see
+	if (m->announce.stepsRemoved >= clock_max_steps_removed(p->clock)) {
-	 * IEEE1588-2008 section 9.3.2.5 (d)
-	 */
-	if (m->announce.stepsRemoved >= 255) {
 		return result;
 	}
 

ptp4l.8

@@ -414,6 +414,13 @@ timing network without loops) only when using the default values of
 G.8275.defaultDS.localPriority and G.8275.portDS.localPriority.
 Careful network engineering is needed when using non-default values.
 .TP
+.B maxStepsRemoved
+When using this option, if the value of stepsRemoved of an Announce
+message is greater than or equal to the value of maxStepsRemoved the
+Announce message is not considered in the operation of the BMCA.
+The default value is 255.
+.TP
+
 .B domainNumber
 The domain attribute of the local clock.
 The default is 0.