Add BMCA support for IEEE 802.1AS-2011

According to IEEE 802.1AS-2011, the BMCA used in gPTP is the same
as that used in IEEE 1588 with the following exceptions:

(1) Announce messages received on a slave port that were not sent
by the receiving time-aware system are used immediately,
i.e., there is no foreign-master qualification.

(2) A port that the BMCA determines should be a master port enters
the master state immediately, i.e., there is no pre-master state.

(3) The uncalibrated state is not needed and, therefore, not used.

(4) All time-aware systems are required to participate in best master
selection (even if it is not grandmaster capable).

This patch is to support (1) by using a specific FOREIGN_MASTER_THRESHOLD
case. (Treat FOREIGN_MASTER_THRESHOLD as 1.)
To support (2) and (3), reuse ptp_fsm and drop pre-master/uncalibrated
states. The (4) item is supported since IEEE 802.1AS reuses OC/BC.

Signed-off-by: Erik Hons <erik.hons@ni.com>
Signed-off-by: Rodney Greenstreet <rodney.greenstreet@ni.com>
Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>

fsm.c

@@ -335,3 +335,16 @@ enum port_state ptp_slave_fsm(enum port_state state, enum fsm_event event,
 
 	return next;
 }
+
+enum port_state ieee8021as_fsm(enum port_state state, enum fsm_event event,
+			       int mdiff)
+{
+	enum port_state next = ptp_fsm(state, event, mdiff);
+
+	if (next == PS_UNCALIBRATED)
+		return PS_SLAVE;
+	if (next == PS_PRE_MASTER)
+		return PS_MASTER;
+
+	return next;
+}

fsm.h

@@ -79,4 +79,14 @@ enum port_state ptp_fsm(enum port_state state, enum fsm_event event, int mdiff);
 enum port_state ptp_slave_fsm(enum port_state state, enum fsm_event event,
 			      int mdiff);
 
+/**
+ * Run the state machine for a ieee8021as port.
+ * @param state  The current state of the port.
+ * @param event  The event to be processed.
+ * @param mdiff  Whether a new master has been selected.
+ * @return       The new state for the port.
+ */
+enum port_state ieee8021as_fsm(enum port_state state, enum fsm_event event,
+			       int mdiff);
+
 #endif

port.c

@@ -278,12 +278,16 @@ void fc_clear(struct foreign_clock *fc)
 
 static void fc_prune(struct foreign_clock *fc)
 {
+	int threshold = FOREIGN_MASTER_THRESHOLD;
 	struct timespec now;
 	struct ptp_message *m;
 
 	clock_gettime(CLOCK_MONOTONIC, &now);
 
-	while (fc->n_messages > FOREIGN_MASTER_THRESHOLD) {
+	if (port_is_ieee8021as(fc->port))
+		threshold = 1;
+
+	while (fc->n_messages > threshold) {
 		m = TAILQ_LAST(&fc->messages, messages);
 		TAILQ_REMOVE(&fc->messages, m, list);
 		fc->n_messages--;
@@ -339,6 +343,7 @@ void ts_add(tmv_t *ts, Integer64 correction)
  */
 static int add_foreign_master(struct port *p, struct ptp_message *m)
 {
+	int threshold = FOREIGN_MASTER_THRESHOLD;
 	struct foreign_clock *fc;
 	struct ptp_message *tmp;
 	int broke_threshold = 0, diff = 0;
@@ -362,15 +367,20 @@ static int add_foreign_master(struct port *p, struct ptp_message *m)
 		LIST_INSERT_HEAD(&p->foreign_masters, fc, list);
 		fc->port = p;
 		fc->dataset.sender = m->header.sourcePortIdentity;
-		/* We do not count this first message, see 9.5.3(b) */
-		return 0;
+		/* For 1588, we do not count this first message, see 9.5.3(b) */
+		if (!port_is_ieee8021as(fc->port))
+			return 0;
 	}
 
 	/*
 	 * If this message breaks the threshold, that is an important change.
 	 */
 	fc_prune(fc);
-	if (FOREIGN_MASTER_THRESHOLD - 1 == fc->n_messages) {
+
+	if (port_is_ieee8021as(fc->port))
+		threshold = 1;
+
+	if (threshold - 1 == fc->n_messages) {
 		broke_threshold = 1;
 	}
 
@@ -2445,6 +2455,7 @@ void port_close(struct port *p)
 struct foreign_clock *port_compute_best(struct port *p)
 {
 	int (*dscmp)(struct dataset *a, struct dataset *b);
+	int threshold = FOREIGN_MASTER_THRESHOLD;
 	struct foreign_clock *fc;
 	struct ptp_message *tmp;
 
@@ -2463,7 +2474,10 @@ struct foreign_clock *port_compute_best(struct port *p)
 
 		fc_prune(fc);
 
-		if (fc->n_messages < FOREIGN_MASTER_THRESHOLD)
+		if (port_is_ieee8021as(fc->port))
+			threshold = 1;
+
+		if (fc->n_messages < threshold)
 			continue;
 
 		if (!p->best)
@@ -3104,19 +3118,6 @@ struct port *port_open(const char *phc_device,
 	p->master_only = config_get_int(cfg, interface_name(interface), "masterOnly");
 	p->bmca = config_get_int(cfg, interface_name(interface), "BMCA");
 
-	if (p->bmca == BMCA_NOOP && transport != TRANS_UDS) {
-		if (p->master_only) {
-			p->state_machine = designated_master_fsm;
-		} else if (clock_slave_only(clock)) {
-			p->state_machine = designated_slave_fsm;
-		} else {
-			pr_err("Please enable at least one of masterOnly or slaveOnly when BMCA == noop.\n");
-			goto err_port;
-		}
-	} else {
-		p->state_machine = clock_slave_only(clock) ? ptp_slave_fsm : ptp_fsm;
-	}
-
 	if (transport == TRANS_UDS) {
 		; /* UDS cannot have a PHC. */
 	} else if (!interface_tsinfo_valid(interface)) {
@@ -3169,6 +3170,26 @@ struct port *port_open(const char *phc_device,
 	p->versionNumber = PTP_VERSION;
 	p->slave_event_monitor = clock_slave_monitor(clock);
 
+	if (config_get_int(cfg, p->name, "asCapable") == AS_CAPABLE_TRUE) {
+		p->asCapable = ALWAYS_CAPABLE;
+	} else {
+		p->asCapable = NOT_CAPABLE;
+	}
+
+	if (p->bmca == BMCA_NOOP && transport != TRANS_UDS) {
+		if (p->master_only) {
+			p->state_machine = designated_master_fsm;
+		} else if (clock_slave_only(clock)) {
+			p->state_machine = designated_slave_fsm;
+		} else {
+			pr_err("Please enable at least one of masterOnly or slaveOnly when BMCA == noop.\n");
+			goto err_transport;
+		}
+	} else {
+		p->state_machine = clock_slave_only(clock) ? ptp_slave_fsm :
+				   port_is_ieee8021as(p) ? ieee8021as_fsm : ptp_fsm;
+	}
+
 	if (number && unicast_client_initialize(p)) {
 		goto err_transport;
 	}