Central Regulatory Domain Agent
CRDA acts as the udev helper for communication between the kernel and userspace for regulatory compliance. It relies on nl80211 for communication.
You can get the latest CRDA code from:
You can get CRDA releases here
The diagram below illustrates the current design of CRDA and its kernel interaction.
Usage design in Linux
Letting the kernel call CRDA
We use userspace events (uevents) to let he kernel speak to userspace. Below is an example udev rule you can place into your distribution's udev rules directory (usually /etc/udev/rules.d/). Note that most distributions have udev configured with inotify on the udev rules directory, so there is no need to restart udev after adding the new rule.
# Example file, should be put in /etc/udev/rules.d/regulatory.rules KERNEL=="regulatory*", ACTION=="change", SUBSYSTEM=="platform", RUN+="/sbin/crda"
Debugging kernel to CRDA communication
To debug communication between the kernel and udev you can monitor udev events:
udevadm monitor --environment kernel
CRDA is licensed under the ISC license in hopes other operating systems can benefit from a community project to enhance regulatory considerations.