IPv6 Stable Private Addresses RFC 7217

[Roy Marples <roy%marples.name@localhost>]

Hi List

The next dhcpcd release will have support for IPv6 Stable Private 
Addresses, RFC 7217.
http://wiki.netbsd.org/projects/project/ipv6-stable-privacy-addresses/
http://tools.ietf.org/html/rfc7217

In summary, this is designed as a replacement interface identifier for 
the normal hardware derived one when using SLAAC.
By storing a persistent secret key and combing this with stable network 
information such as prefix, ssid (if available), hardware address and a 
dad_counter we can then take an interface identifier from a hash of the 
above information combined.

The most basic goal is that the host is no longer track-able across 
different networks based on their global address, but the address 
remains stable on each network.

My question is this: should this be enabled by default as privacy is a 
good thing, or should the normal hardware based address be kept?

Thanks

Roy