Does anything whatsoever support the RPL protocol? I have only ever seen that used and/or implemented in various 6loWPAN attempts, most noticeable of these being Contiki. I might be wrong but I am not sure it even applies to standard IPv4/6 at all.
You might want to look at "6lbr" which implement a "bridge" on Linux bridging between IPv6 and 6loWPAN (based in part on Contoki), but without the actual radio to communicate with 6loWPAN devices. It is a bit of a mess, but I did at some point manage to get it up and running on Linux (OpenWrt actually) using the Atmel Zigbit USB stick.
Edison has openSSL which may provide the level of encryption for the Ripple protocol. There is no library or source code for the Ripple protocol on Yocto.
I am not sure what is the connection between OpenSSL and RPL.