[Linuxptp-devel] [PATCH 3/3] port: Signal sync/follow-up mismatch events loudly

[Vladimir O. <ol...@gm...>]

Ptp4l is too silent when receiving, for whatever reason, out of order
messages. If the reordering is persistent (which is either a broken
network, or a broken kernel), the behavior looks like a complete
synchronization stall, since the application is designed to never
attempt to recover from such a condition.

At least save some people some debugging hours and be loud when the
application reaches this code path.

Signed-off-by: Vladimir Oltean <ol...@gm...>
---
 port.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/port.c b/port.c
index 58fbe669af14..58559531f7e7 100644
--- a/port.c
+++ b/port.c
@@ -1191,6 +1191,23 @@ static void port_synchronize(struct port *p,
 	}
 }
 
+static void port_syfufsm_print_mismatch(struct port *p, enum syfu_event event,
+					struct ptp_message *m)
+{
+	int expected_msgtype;
+
+	if (event == SYNC_MISMATCH)
+		expected_msgtype = FOLLOW_UP;
+	else
+		expected_msgtype = SYNC;
+
+	pr_err("port %hu: have %s %d, expecting %s but got %s %d, dropping",
+	       portnum(p), msg_type_string(msg_type(p->last_syncfup)),
+	       p->last_syncfup->header.sequenceId,
+	       msg_type_string(expected_msgtype),
+	       msg_type_string(msg_type(m)), m->header.sequenceId);
+}
+
 /*
  * Handle out of order packets. The network stack might
  * provide the follow up _before_ the sync message. After all,
@@ -1225,6 +1242,7 @@ static void port_syfufsm(struct port *p, enum syfu_event event,
 	case SF_HAVE_SYNC:
 		switch (event) {
 		case SYNC_MISMATCH:
+			port_syfufsm_print_mismatch(p, event, m);
 			msg_put(p->last_syncfup);
 			msg_get(m);
 			p->last_syncfup = m;
@@ -1232,6 +1250,7 @@ static void port_syfufsm(struct port *p, enum syfu_event event,
 		case SYNC_MATCH:
 			break;
 		case FUP_MISMATCH:
+			port_syfufsm_print_mismatch(p, event, m);
 			msg_put(p->last_syncfup);
 			msg_get(m);
 			p->last_syncfup = m;
@@ -1252,6 +1271,7 @@ static void port_syfufsm(struct port *p, enum syfu_event event,
 	case SF_HAVE_FUP:
 		switch (event) {
 		case SYNC_MISMATCH:
+			port_syfufsm_print_mismatch(p, event, m);
 			msg_put(p->last_syncfup);
 			msg_get(m);
 			p->last_syncfup = m;
@@ -1267,6 +1287,7 @@ static void port_syfufsm(struct port *p, enum syfu_event event,
 			p->syfu = SF_EMPTY;
 			break;
 		case FUP_MISMATCH:
+			port_syfufsm_print_mismatch(p, event, m);
 			msg_put(p->last_syncfup);
 			msg_get(m);
 			p->last_syncfup = m;
-- 
2.17.1