compression format for ipv6 in low power networks (6lowpan)

Hi all,

could anybody please give me an advice.

Currently I have 802.15.4 network stack prototype in Linux 
(https://sourceforge.net/projects/linux-zigbee/),
and I want to add IPv6 support. So it needs to add IPv6 header 
encapsulation/decapsulation above 802.15.4 layer.

What's the best way to do it in Linux (something like ipv6-ipv6 
tunnel...)? Where this code must be stored, in 'ipv6' folder or in 
'mac802154'?

Thank you,
Alexander