using "ping6 -f %tapX" from two threads on linux to riot at the same time, I can reliably crash native:

kernel_init(): This is RIOT! (Version: 2014.12-1938-g910a-booze)
kernel_init(): jumping into first task...
UART0 thread started.
uart0_init() [OK]
RIOT network stack example application
All up, running the shell now
> /home/kaspar/src/riot.8/examples/ng_networking/bin/native/ng_networking.elf: lpm_set(): select(): Resource temporarily unavailable
[kaspar@booze ng_networking (master)]$

Weird thing is that it's crashing in lpm_set() with "Resource temporarily unavailable", which points to EAGAIN in errno, which should have been handled before. Looks like a race.

@LudwigOrtmann, does native share errno between all threads, like "normal" RIOT?