DELETE tun interfaces

A quick note on killing a bug in a previous recipe and deleting protocol 41 tunnel interfaces in linux.

datun is an interface used as one of the edges in a 6in4 tunnel set with
ip tunnel add datun mode sit remote local ttl 64 
ip link set datun up

seen as
# ifconfig datun
datun Link encap:IPv6-in-IPv4 

and taken down with
# ip link set datun down
at the 6in4 tunnels to the IPv6 Internet how-to, even in places we needed to delete the tunnel instead of putting it down, causing all kinds of errors and confusion.

To delete a tunnel interface.
ip tunnel del datun

Instead of "restarting" the 6in4 tunnel it may be better to destroy it and set it again.
# ip tunnel del datun
# /etc/network/if-up.d/

delete tun interface