Possible filtered monitored item status change problem

[jojastahl]

Description

I probably discovered a problem with status change detection of monitored items, if a deadband filter is applied.

Background Information / Reproduction Steps

While I was looking for a problem where my monitored items of a subscription kept the initial Status UA_STATUSCODE_BADWAITINGFORINITIALDATA, I looked at the detectValueChangeWithFilter function in ua_subscription_datachange.c. I couldn't verify with a running test, whether my code analysis is correct, but maybe the code owner can quickly confirm or reject this issue:

I think that in case of a monitored item with deadband filter type UA_DEADBANDTYPE_ABSOLUTE, a status change of the data value will not be reported, if the value remains stable. Evidence: in case of UA_DEADBANDTYPE_PERCENT a call to updateNeededForStatusCode is used to check for this, but in case of UA_DEADBANDTYPE_ABSOLUTE this call is missing. See

open62541/src/server/ua_subscription_datachange.c

Lines 195 to 197 in a9a9e2a

	if(!updateNeededForFilteredValue(&value->value, &mon->lastValue,
	mon->filter.dataChangeFilter.deadbandValue))
	return UA_STATUSCODE_GOOD;

compared to

open62541/src/server/ua_subscription_datachange.c

Lines 209 to 213 in a9a9e2a

	if(!updateNeededForFilteredPercentValue(&value->value, &mon->lastValue,
	mon->filter.dataChangeFilter.deadbandValue, euRange)) {
	if(!updateNeededForStatusCode(value, mon)) //when same value, but different status code is written
	return UA_STATUSCODE_GOOD;
	}

.

The second observation targets the updateNeededForStatusCode function at

open62541/src/server/ua_subscription_datachange.c

Lines 175 to 182 in a9a9e2a

	static UA_Boolean
	updateNeededForStatusCode(const UA_DataValue *value, const UA_MonitoredItem *mon) {
	if (UA_Variant_isScalar(&value->value)) {
	if(value->status != mon->lastStatus)
	return true;
	}
	return false;
	}

. Is it correct, that a status change is only detected for scalar values? The updateNeededForFilteredValue and updateNeededForFilteredPercentValue are handling arrays aswell, so this one should probably do so, too?

Checklist

Please provide the following information:

• open62541 Version (release number or git tag): master
• Other OPC UA SDKs used (client or server):
• Operating system:
• Logs (with UA_LOGLEVEL set as low as necessary) attached
• Wireshark network dump attached
• Self-contained code example attached
• Critical issue