[Bug Report] Runtime errors in vanet.py (AttributeError & UnboundLocalError) - Mininet-WiFi

[22029106 Nguyễn Trương Dũng]

Dear Ramon Fontes,

First of all, thank you for your excellent work on Mininet-WiFi. It is a fantastic tool for our research.

I am writing to report two issues I encountered while using the vanet.py module in the latest master branch (Commit: 070ea2d, dated Jan 9, 2026).

Here are the details of the bugs and the temporary fixes I applied locally:

1. AttributeError: 'OVSAP' object has no attribute 'lastpos'

Location: mn_wifi/vanet.py, inside display_grid method. The Issue: When initializing the grid with Access Points (OVSAP), the code attempts to call bs.set_pos_wmediumd(bs.position). However, in the current version, the AP object does not seem to have the lastpos attribute initialized at this stage, causing a crash.

Traceback:
File ".../mn_wifi/vanet.py", line 151, in display_grid
    bs.set_pos_wmediumd(bs.position)
File ".../mn_wifi/node.py", line 211, in set_pos_wmediumd
    if self.lastpos != pos:
AttributeError: 'OVSAP' object has no attribute 'lastpos'

2. UnboundLocalError: local variable 'x_min' referenced before assignment

Location: mn_wifi/vanet.py, inside display_cars method. The Issue: The variables x_min, x_max, y_min, y_max are initialized inside a for loop iterating over self.roads. However, they are later used in self.carProp calls. If the loop logic flow varies, these variables remain uninitialized when carProp is called.

Traceback:

File ".../mn_wifi/vanet.py", line 223, in display_cars
    car.prop = self.carProp(point, ang, x_min, x_max, y_min, y_max)
UnboundLocalError: local variable 'x_min' referenced before assignment

I hope this feedback helps improve the stability of the VANET module. Looking forward to the next update.

Best regards,

Nguyen Truong Dung