port: Drop received 802.1AS packets with invalid transportSpecific va…

…lues

According to IEEE Std 1588-2019 Table 2 and IEEE Std 802.1AS-2020
Sections 11.2.17.1 and 13.3.1.2.16, the permitted transportSpecific
(or majorSdoId) values for 802.1AS are 0x1 for a gPTP domain and 0x2
for CMLDS. Any message received with values other than these is not
from an IEEE802.1AS-2020 PTP Instance and should be dropped.

This fix ensures that incoming 802.1AS packets with an invalid transportSpecific
value, such as 0x3, are dropped. This is particularly necessary when
ignore_transport_specific=1 is set to allow Pdelay measurements between
CMLDS-enabled (TS_CMLDS value=0x2) and non-CMLDS systems (TS_IEEE_8021AS value=0x1).

v2: Fixed indentation.
v3: Added pr_err and fixed trailing whitespace.
v4: Changed pr_err to pr_debug

Signed-off-by: Chwee-Lin Choong <chwee.lin.choong@intel.com>
Signed-off-by: Andrew Zaborowski <andrew.zaborowski@intel.com>

msg.h

@@ -39,6 +39,7 @@
 
 /* Values for the transportSpecific field */
 #define TS_IEEE_8021AS (1<<4)
+#define TS_CMLDS       (2<<4)
 
 /* Values for the messageType field */
 #define SYNC                  0x0

port.c

@@ -796,6 +796,15 @@ static int port_ignore(struct port *p, struct ptp_message *m)
 	if (path_trace_ignore(p, m)) {
 		return 1;
 	}
+	if (port_is_ieee8021as(p)) {
+		if (msg_transport_specific(m) != TS_IEEE_8021AS &&
+		    msg_transport_specific(m) != TS_CMLDS) {
+			pr_debug("%s: received %s with invalid transport specific value %d "
+				"for IEEE8021as", p->log_name, msg_type_string(msg_type(m)),
+				msg_transport_specific(m)>>4);
+			return 1;
+		}
+	}
 	if (p->match_transport_specific &&
 	    msg_transport_specific(m) != p->transportSpecific) {
 		return 1;