In any software project, defects are inevitable and requires debugging to root cause it, and this eventually leads to a fix. The key lies in understanding the issue, analyzing it, and choosing the right approach to resolve it. Debugging issues may seem overwhelming at first, but with a clear understanding of the problem and the right tools, the process becomes more manageable.
This article explores the debugging sequence for common issues encountered while working with the Linux WiFi stack.
Common Issues
While developing code or testing a particular feature, various issues may arise, such as:
Device Not Detected
Driver Not Loaded
Process Not Running
Crashes & Kernel Panics
Performance Bottlenecks
Compatibility Issues
Each of these requires different approaches of analysis and debugging.
Lessons from the Field: Debugging WiFi Issues
While working with the Openwrt target based on ath12k driver, which supports Qualcomm Wi-Fi 7 (IEEE 802.11be) devices, several challenges were encountered. Here are some key issues and how they were tackled:
Crashes and Kernel Panics : Misconfigurations, firmware incompatibilities, or unhandled exceptions led to unexpected crashes.
Packet Drops and Performance Issues : Unstable firmware, hardware limitations caused connectivity problems.
Hostapd and Wpa_supplicant Failures : Misconfigured network parameters and hidden driver bugs resulted in failures.
Now, let’s visualize how these issues manifest across different layers of the WiFi stack.
Debugging Essentials: Tracing, Crashes, Network Insights
Linux provides a variety of powerful tools to track down and resolve issues efficiently. Some essential debugging tools which were involved in our analysis:
Print Statements and Logs: The simplest yet most effective debugging method. Inserting printk (for kernel debugging) or printf statements (for user-space debugging) helps to track the program flow and identify issues.
GDB (GNU Debugger): A powerful tool for inspecting and controlling program execution, setting breakpoints, and analyzing crashes.
Tcpdump: A command-line tool for capturing and analyzing network packets, essential for diagnosing network-related issues.
Wireshark: A graphical tool for deep packet inspection, useful for troubleshooting network communications and protocol-level issues.
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Debugging through Hostapd and Wpa_supplicant Logs
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In Openwrt, by default hostapd or wpa_supplicant runs in less verbose mode, while debugging we may need a detailed log. To get the logs, we may need to start the hostapd or wpad in higher verbose mode. We would also like to run the hostapd in foreground to lively watch the logs in console.
Debugging user-space applications is just the first step. In the upcoming article, we’ll venture into the depths of kernel debugging and unraveling techniques to diagnose and resolve kernel-level issues with precision. For the exciting deep dive on the article, visit this https://zilogic.com/blog/tutorial-linux-wifi-debugging.html
Stay tuned for more updates.
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