6lowpan: IPv6 encapsulation question

Hi,

We are going to work on the implementation of 6lowpan: the encapsulation
for IPv6 packets for IEEE 802.15.4 networks. RFC 4944 and several
following drafts from 6lowpan WG define several types of IPv6/UDP
headers compression, special fragmentation, ND, etc.

The question is: what is the most clean way to implement 6lowpan and to
hook it into the Linux kernel.

We've identified the following possible ways:

* Implement it just as a special net_device, accepting only IPv6 trafic,
  and splitting/merging it on the top of our IEEE 802.15.4 net_devices

* Implement transmission/fragmentation by hooking into neighbouring output
  routines

* Implement transmission/fragmentation by hooking into dst->output
  routines

* Just hook into IPv6 stack by checking for ARPHRD_IEEE802154 devices

* ???

-- 
With best wishes
Dmitry