I found out that the batman-exp daemon goes crazy when its internal life-time
variable overflows. This will happen after 49 days, 17 hours, 2 minutes, and
48 seconds (which corresponds to 2^32 milliseconds). Unfortunately, its
behavior afterwards can be anything between hanging around and doing nothing
and an endless loop of sending packets. The problem is fixed with revision
If you are running batman-exp I strongly suggest to update.