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Introduction

The FreeRADIUS web site is at https://freeradius.org/, and most information referenced in this document can be found there.

This document is primarily for non-developers of the FreeRADIUS server. If you are able to patch the code to work correctly, then we invite you to join the development list to discuss it. If you’re the type who know little about how to code, then this is the place for you!

You found a bug

Where the server terminates ungracefully due to a bus error, segmentation violation, or other memory error, you should create a new issue in the issue tracker https://bugs.freeradius.org/, including information from the debugging sections below.

For any other issues, you should first discuss them on the FreeRADIUS users list, to see if anyone can reproduce them. Often there’s a simple explanation of why the server behaves as it does, and it’s not necessarily a bug in the code, so browse the lists’ archives of the last two months, and if you don’t see messages about it, ask!

If the behavior is correct but confusing, we think that’s a bug too, and you should file a bug against our documentation.

For more information about the users list, the lists’ archives and the faq, please visit https://www.freeradius.org/list/users.html Please make sure to READ and RESPECT the house-rules. You will get much better response and much faster if you do!

Core dumps

If the server (or one of the accompanying programs) core dumps, then you should rebuild the server as follows:

$ ./configure --enable-developer
$ make
$ make install

and then run the program again. You may have to to enable core dumps, via:

$ ulimit -c unlimited

When it core dumps, do:

$ gdb /path/to/executable /path/to/core/file

Enable logging in gdb via the following commands:

(gdb) set logging file gdb-radiusd.log
(gdb) set logging on

and follow the instructions in the proceeding section.

You can also enable the panic_action given in raddb/radiusd.conf. See the comments in that file for more details about automatically collecting gdb debugging information when the server crashes.

Debugging a live server

If you can’t get a core dump, or the problem doesn’t result in a core dump, you may have to run the server under gdb. To do this, ensure that you have symbols in the binaries (i.e. a 'non-stripped' binary) by re-building the server as described in the previous section. Then, run the server under gdb as follows:

$ gdb radiusd

Enable logging in gdb via the following commands:

(gdb) set logging file gdb-radiusd.log
(gdb) set logging on

Tell gdb to pass any necessary command-line arguments to the server:

(gdb) set args ...

Where the ``…'' are the command-line arguments you normally pass to radiusd. For debugging, you probably want to do:

(gdb) set args -fxx

Then, do:

(gdb) run

When something interesting happens, you can hit CTRL-C in the window, and you should be back at the gdb prompt:

(gdb)

And follow the instructions in the next section.

Obtaining useful information

Once you have a core dump loaded into gdb, or FreeRADIUS running under gdb, you may use the commands below to get useful information about the state of the server.

If the server was built with threads, you can do:

(gdb) info threads

Which will give you information about the threads. If the server isn’t threaded, that command-line will print a message saying so.

Then, do:

(gdb) thread apply all bt full

If the server isn’t threaded, the thread apply section isn’t necessary

The output should be printed to the screen, and also sent to the gdb-radiusd.log file.

You should then submit the information from the log file, along with any server output, the output of radiusd -xv, and information about your operating system to:

https://bugs.freeradius.org/

Submitting it to the bug database ensures that the bug report won’t get forgotten, and that it will be dealt with in due course.

You should provide the issue number in any mail sent to the user’s list.

Valgrind

On Linux systems, valgrind is a useful tool that can catch certain classes of bugs. To use it, run the server via:

$ valgrind --tool=memcheck --leak-check=full radiusd -Xm

It will print out certain kinds of errors to the screen. There may be a number of errors related to OpenSSL, dlopen(), or libtldl. We cannot do anything about those problems. However, any errors that are inside of the FreeRADIUS source should be brought to our attention.

Running with screen

If the bug is a crash of the server, and it takes a long time for the crash to happen, perform the following steps:

  • Log in as root.

  • Open a screen session: $ screen bash.

  • Make sure FreeRADIUS is not running.

  • Make sure you have all the debug symbols about, or a debugable version of the server installed (one built with --enable-developer as above).

  • Configure screen to log to a file by pressing Ctrl+a, then h.

  • Type gdb /path/to/radiusd (or /path/to/freeradius on Debian).

  • At the (gdb) prompt, type run -X.

  • Detach from screen with Ctrl+a, d.

  • When you notice FreeRADIUS has died, reconnect to your screen session $ screen -D -r.

  • At the (gdb) prompt type where or for lots of info try thread apply all bt full.

  • Tell screen to stop logging, Ctrl+a, h.

  • Logout from screen.

FreeRADIUS Project, copyright 2019