Please tell me, how can i write a module of my own in c.

Also, tell me how can i compile it and use with freeradius(also say the config file changes)

Take a look at: src/modules/rlm_example doc/module_interface To get your module to be compiled with radiusd, either add it to src/modules/stable and then do a configure in the root level, or add it to MODULES in Make.inc For config file changes, take a look at the module configurations in radiusd.conf and how the modules are used. You should be able to work it out from there. Hope that helps, Mike