[riot-devel] RIOT+ULAs: no router entry

smlng s at mlng.net
Fri Apr 22 12:19:36 CEST 2016


Hi everyone,

I'm testing COAP between RIOT on Phytec pba-d-01-kw2x and Linux on RasPi+Openlabs using ULA IP addresses. 

On the Pi I run a 'radvd' to advertise a ULA prefix to RIOT, which works:
 - RIOT sends RS after boot
 - the Pi answers with RA containing ULA prefix
 - RIOT configures ULA IP on 6lo iface

COAP (or communication in general) via ULA IP works, as long as RIOT has the Pi in its routers cache. However, sometimes RIOT _forgets_ or does not set a routers entry for the Pi at all. In that case communication is not possible via ULAs, using link-local IPs works all the time. The issue seems be with the RS+RA processing. I found that sometimes RIOT does not create a routers entry on reception of a RA - though it does configure the ULA prefix correctly. 

I just had the case that RIOT configures the ULA _and_ sets a routers entry, hence communication was working. At least for about 15min, but then RIOT send another RS, Pi answers with RA, RIOT still has ULA IP configured -- BUT the routers entry for the Pi is gone and communication fails. Again: using link-local IPs still works.

Btw. even when communication via ULAs is working, RIOT never creates a ncache entry for ULA IP of the Pi but it did create an ncache entry for link-local IP of the Pi. I thought the latter is not required/allowed in 6lo but for ULAs it should create an entry?

Has somebody else observed this behavior or any hints how to resolve this?

Thanks, best
  Sebastian



More information about the devel mailing list