Documentation > Miscellaneous > Logging


If Jool has something to say, it will do so in the kernel logs (just like any other kernel component). Typical ways to find this include

Thankfully, Linux is generally silent after booting, so Jool’s latest messages should be found at the very bottom.

Jool uses four levels in the severity spectrum (see dmesg --help):

  1. err: “Your configuration cannot be applied, user”. This only happens during module insertion/removal and as a response of userspace application requests. These messages are also sent over to the userspace application so it can print them in stderr.
  2. warn: “Are you sure this configuration is sane? I’m going to keep doing this, but it doesn’t look like it’s going places”. Only happens during packet translations.
  3. info: “The kernel module was inserted”, “the kernel module was removed”. Also --logging-bib and --logging-session’s exploits.
  4. debug: “And now I’m doing this”. “I couldn’t translate this packet because X, and I think it’s normal”.

Debug messages are normally compiled out of Jool’s binaries because they are lots and can slow things down. If you are testing or troubleshooting however, they can be of help.

If you want Jool to print debug messages, go back to the kernel module’s compilation step and include the -DDEBUG flag. After reinstalling and remodprobing normally, you should see a lot of mumbling as a result of network traffic translation, which should give you ideas as to what might be wrong:

$ # Recompile and reinstall Jool with the flag enabled.
$ cd Jool/mod
$ make JOOL_FLAGS=-DDEBUG       # <==== This is the key!
$ sudo make install
$ sudo depmod
$ # Disable the old Jool, add the new one.
$ # Please note that this is a rough example; you need to adjust these commands
$ # depending on your original configuration.
$ sudo modprobe -r jool_siit
$ sudo modprobe jool_siit pool6=...
$ # Read the logs.
$ dmesg | tail -5
[ 3465.639622] ===============================================
[ 3465.639655] Catching IPv4 packet:>
[ 3465.639724] Translating the Packet.
[ 3465.639756] Address lacks an EAMT entry and there's no pool6 prefix.
[ 3465.639806] Returning the packet to the kernel.

These messages quickly add up. If your computer is storing them, make sure you revert the binaries when you’re done so they stop flooding your disk.

If dmesg is not printing the messages, try tweaking its --console-level. Have a look at man dmesg for details.