TRX: Check if Transceiver indicates an out of range clock

If frame number is out of range (>= 2715648), the scheduler's process
would end up in an infinite loop. This is because the loop would schedule
bursts until the indicated frame number is reached, which would not be
possible.

The openbts, calypso-bts and osmo-trx might send out out of range clock
indications every 3.5 hour.

1 files changed, 15 insertions, 7 deletions

diff --git a/src/osmo-bts-trx/trx_if.c b/src/osmo-bts-trx/trx_if.c
index bc80150b..8993de64 100644
--- a/src/osmo-bts-trx/trx_if.c
+++ b/src/osmo-bts-trx/trx_if.c
@@ -123,21 +123,29 @@ static int trx_clk_read_cb(struct osmo_fd *ofd, unsigned int what)
 {
 	char buf[1500];
 	int len;
+	uint32_t fn;
 
 	len = recv(ofd->fd, buf, sizeof(buf) - 1, 0);
 	if (len <= 0)
 		return len;
 	buf[len] = '\0';
 
-	if (!strncmp(buf, "IND CLOCK ", 10)) {
-		uint32_t fn;
-
-		sscanf(buf, "IND CLOCK %u", &fn);
-		LOGP(DTRX, LOGL_INFO, "Clock indication: fn=%u\n", fn);
-		trx_sched_clock(fn);
-	} else
+	if (!!strncmp(buf, "IND CLOCK ", 10)) {
 		LOGP(DTRX, LOGL_NOTICE, "Unknown message on clock port: %s\n",
 			buf);
+		return 0;
+	}
+
+	sscanf(buf, "IND CLOCK %u", &fn);
+	LOGP(DTRX, LOGL_INFO, "Clock indication: fn=%u\n", fn);
+
+	if (fn >= 2715648) {
+		fn %= 2715648;
+		LOGP(DTRX, LOGL_ERROR, "Indicated clock's FN is not wrapping "
+			"correctly, correcting to fn=%u\n", fn);
+	}
+
+	trx_sched_clock(fn);
 
 	return 0;
 }