Julius Plenz wrote:

whenever a user successfully logs in, I want to send a custom accounting packet with derived information to a server. Is there a way to do that from the config directly?

No.

I have searched for some time now but couldn't find anything like that... Right now I'm using a script that uses the "Authen::Radius" Perl module, but I want to get rid of this solution.

That works. I'd keep it for now.

If there's no built-in mechanism, my plan would be to write a module that uses libfreeradius.so's library functions (and already initialized dictionaries etc.) to create a queue, send a packet etc. -- are there any problems with this approach?

Threading. Event handling, timers, etc.

Functions like fr_packet_list_create(), rad_send(), fr_packet_list_recv() etc. are all reentrant, aren't they?

No. The fr_packet_list* functions aren't thread-safe. One of the things we're looking at is making the core a little more generic. Right now, the server can receive an Access-Request, and originate a CoA packet. It can't originate an Accounting-Request packet. Fixing that requires a series of careful changes. But it's a fair amount of work, and likely won't be in 3.0.x. For now, I'd suggest keeping the Perl solution. It's fine until you get 10K+ packets/s. Alan DeKok.