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4 bytes value bug in LM5
#1
Hi,
I use ETS5. I'm connected to KNX via LM.
Everytime I try to read a 4 bytes value which is filtered out I get "Connection lost" followed by "red circle" in the connection statusbar in ETS Diagnostics tab.
Both of my LMs (first has actual firmware, second uses the most recent RC) are affected by this issue. If I uncheck IP>TP filter then everything is OK.
Unfortunately I can't say if the problem is in LM or in ETS because I don't have any other way how to connect to KNX.

Printscreens attached.


Attached Files Image(s)
       
LM5Lp, firmware: 2018.08.22, FlashSYS v2, ARMv7 Processor rev 5 (v7l), kernel 4.4.151





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#2
I suppose you are connected via tunnelling, you should uncheck "apply filter to tunneling" in KNX settings.
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#3
If I uncheck "apply filter to tunneling" then it doesn't crash the connection. But I want this filter on.
Why only 4 bytes values are affected? And why just sending of a read packet disconnects whole ETS?
LM5Lp, firmware: 2018.08.22, FlashSYS v2, ARMv7 Processor rev 5 (v7l), kernel 4.4.151





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#4
Probably because packet is dropped and no ACK is sent. Why do you need to filter tunnelling?
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#5
I filter tunnelling just because I don't need it. I'm used to switch off everything I don't really need and is touching somehow networking. I see it as a potential security issue.
LM5Lp, firmware: 2018.08.22, FlashSYS v2, ARMv7 Processor rev 5 (v7l), kernel 4.4.151





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#6
(09.06.2017, 12:10)Thomas Wrote: I filter tunnelling just because I don't need it. I'm used to switch off everything I don't really need and is touching somehow networking. I see it as a potential security issue.

If you are worry about security then use encryption key and Enable only secure connection.  Filter meant to be used only to limit amount of telegrams going from one network to another.
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#7
I understand I can solve the actual problem by disabling the filter. But really, don't you see it as a bug which is now minor for me but can be serious in some circumstances? Why only 4 bytes objects are affected by this issue? Why 1 bit object with the same filtering setting is not a problem? It looks like a buffer overflow somewhere.
LM5Lp, firmware: 2018.08.22, FlashSYS v2, ARMv7 Processor rev 5 (v7l), kernel 4.4.151





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#8
Read telegram is the same for all data types, I'll check it next week just to be sure.
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#9
Yes, telegram is dropped and no ACK is sent. This is why ETS tells that connection is lost. I see no point in fixing this as filter does not provide a lot of security for tunnelling.
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