IPv6: IPv6-in-IPv6 tunnel

modulename: ip6_tunnel.ko

configname: CONFIG_IPV6_TUNNEL

Linux Kernel Configuration
└─>Networking
└─>Networking options
└─>IPv6: IPv6-in-IPv6 tunnel
In linux kernel since version 2.6.12  
Support for IPv6-in-IPv6 tunnels described in RFC 2473.

If unsure, say N.

source code:
net/ipv6/ip6_tunnel.c