Dear Maintainer,

I submitted a patch to fix the PythonCallBack function.

Bug reproduction:

When installing python3-pcapy in the environment of python3.12 and using the loop function of the pcapy module, the following error message will be reported.

$ sudo python3 test.py
Traceback (most recent call last):
File "/home/txf/workdir/test.py", line 8, in <module>
     cap.loop(0, packet_handler)
TypeError: packet_handler() missing 2 required positional arguments: 'header' and 'data'

Cause analysis:
The len pointer in the PythonCallBack function is of type (Py_stsize_t *), pointing to (&header ->caplen). The caplen variable is of 4-byte type (unsigned int), while  Py_Ssize_t is of 8-byte type. The above code will cause the * len variable to read 8 bytes of memory, resulting in a logical error in the code.

The final result is
arglist=Py_SuildValue ("Oy #", hdr, packtdata, * len);
Execution error.

My repair suggestion is to change the (* len) variable type in the PythonCallBack function to (unsigned int *).
Here are my test scripts and patch fixes.

I am using Linux, 6.11.0-24-generic and libc6 2.39.

The patch has been tested on Debian bookworm and works correctly.

Thank you for considering this contribution.

Best regards,
Xiaofeng Tang



tangxiaofeng@kylinos.cn