Comments (3)
ralphlange
commented on June 3, 2024
The segfault happens as part of updating internal structures in a callback function supplied by my code to the SDK, when the SDK signals the completion of a read request.
Somehow the array of the values provided to the callback seems to have invalid data (or the array is only partial?) so that assigning the status code that I get as an argument in the callback to a local variable segfaults.
That could match a situation, where a read request (possibly the read request done on all items after the connection comes up) times out. The session gets the callback that the connection status changed to WatchdogTimeout and then the read completion callback (of the read that timed out) is called with missing or zero values.
Since I have not seen this WatchdogTimeout status and don’t know how to produce it, I have not tested that situation.
(Adding tests using mock versions of the SDK classes is on my list, but that’s not trivial and not done yet.)
That part of the code has changed for 0.6 and will again for 0.7, so I am not really inclined to further investigate… of course, invalid values in the read completion callback could still create some havoc. I will add simple consistency checks in 0.7 – I was always assuming data coming up from the SDK to be sane, but that might not be the case, after all.
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ralphlange
commented on June 3, 2024
Console log:
efe358d.mpsid-i.4087 > OPC UA session MPSoS:Ctrl-IOC-01:Mag: connection status changed from Connected to ConnectionErrorApiReconnect
OPC UA session MPSoS:Ctrl-IOC-01:Mag: connection status changed from ConnectionErrorApiReconnect to NewSessionCreated
OPC UA session MPSoS:Ctrl-IOC-01:Mag: connection status changed from NewSessionCreated to Connected
OPC UA session MPSoS:Ctrl-IOC-01:Mag: (readBatchOfNodes) beginRead service ok (transaction id 3; retrieving 309 nodes)
Session MPSoS:Ctrl-IOC-01:Mag: (readComplete) getting data for read service (transaction id 3; data for 309 items)
Session MPSoS:Ctrl-IOC-01:Mag: (requestWrite) beginWrite service ok (transaction id 4; writing 1 nodes)
Session MPSoS:Ctrl-IOC-01:Mag: (writeComplete) getting results for write service (transaction id 4; results for 1 items)
OPC UA session MPSoS:Ctrl-IOC-01:VAC: connection status changed from Connected to ConnectionWarningWatchdogTimeout
OPC UA session MPSoS:Ctrl-IOC-01:VAC: connection status changed from ConnectionWarningWatchdogTimeout to Connected
OPC UA session MPSoS:Ctrl-IOC-01:VAC: (readBatchOfNodes) beginRead service ok (transaction id 3; retrieving 357 nodes)
Session MPSoS:Ctrl-IOC-01:VAC: (readComplete) getting data for read service (transaction id 3; data for 357 items)
OPC UA session MPSoS:Ctrl-IOC-01:Mag: connection status changed from Connected to ConnectionWarningWatchdogTimeout
OPC UA session MPSoS:Ctrl-IOC-01:Mag: connection status changed from ConnectionWarningWatchdogTimeout to Connected
OPC UA session MPSoS:Ctrl-IOC-01:Mag: (readBatchOfNodes) beginRead service ok (transaction id 5; retrieving 309 nodes)
Session MPSoS:Ctrl-IOC-01:Mag: (readComplete) getting data for read service (transaction id 5; data for 309 items)
OPC UA session MPSoS:Ctrl-IOC-01:Mag: connection status changed from Connected to ConnectionWarningWatchdogTimeout
OPC UA session MPSoS:Ctrl-IOC-01:Mag: connection status changed from ConnectionWarningWatchdogTimeout to Connected
OPC UA session MPSoS:Ctrl-IOC-01:Mag: (readBatchOfNodes) beginRead service ok (transaction id 6; retrieving 309 nodes)
Session MPSoS:Ctrl-IOC-01:Mag: (readComplete) getting data for read service (transaction id 6; data for 0 items)
OPC UA session MPSoS:Ctrl-IOC-01:Mag: connection status changed from Connected to ConnectionWarningWatchdogTimeout
/home/iocuser/epics/base-7.0.3/require/3.1.1/bin/iocsh.bash: line 145: 4102 Segmentation fault (core dumped) ${__CHRT__}${EPICS_BASE}/bin/${EPICS_HOST_ARCH}/softIoc${__PVA__} -D ${EPICS_BASE}/dbd/softIoc${__PVA__}.dbd "${IOC_STARTUP}" 2>&1
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ralphlange
commented on June 3, 2024
Two issues:
Extraneous initial read() operation
The transition WatchdogTimeout to Connected triggers the initial read() of all items. That is wrong, as the server never went away.
Segfault on empty read() reply
A service request that gets an empty answer because of a server side issue
OPC UA session MPSoS:Ctrl-IOC-01:Mag: (readBatchOfNodes) beginRead service ok (transaction id 6; retrieving 309 nodes)
Session MPSoS:Ctrl-IOC-01:Mag: (readComplete) getting data for read service (transaction id 6; data for 0 items)
OPC UA session MPSoS:Ctrl-IOC-01:Mag: connection status changed from Connected to ConnectionWarningWatchdogTimeout
/home/iocuser/epics/base-7.0.3/require/3.1.1/bin/iocsh.bash: line 145: 4102 Segmentation fault (core dumped)
causes the client to segfault. That's a bug, which needs to be fixed by checking consistency between request and reply.
from opcua.
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