local variable 'seq_no' referenced before assignment

SkypLabs / pyhdlcontroller

Python HDLC controller

https://pyhdlcontroller.skyplabs.net/en/stable/

MIT License

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local variable 'seq_no' referenced before assignment #1

Closed dpolz closed 7 years ago

dpolz commented 7 years ago

In hdlcontroller.py line 260 seq_no is not defined. Must be defined before try-statement in line 229. Maybe seq_no=0

SkypLabs commented 7 years ago

Indeed, there is a problem here. However, the sequence number to send back as NACK must be the same as the one received in the frame which is processed. Defining it before the try-statement won't solve this issue.

After having re-read the code of python4yahdlc, I realised that I hadn't taken into account this case. The function get_data throws an FCSError exception without giving the sequence number to send back as NACK. Consequently, I have to update python4yahdlc first.

Thank you for having noticed that !

SkypLabs commented 7 years ago

I just added a test to bring this problem to light.

Actually, when a frame with an FCS error is received, two behaviours are possible :

Send an NACK, which implies to read the sequence number from the corrupted frame. To do so, as said above, I need to update python4yahdlc first to be able to fix this issue.
Send nothing and let the sender of the corrupted frame send it back after its timeout.

After having fixed this issue, I will add an option to choose between these two behaviours.