[gentoo-hardened] Documenting disabling IPV6 off

[Ed W]

Hi folks

Can we get some volunteers to write-up some ipv6 notes for the 
gentoo/hardened docs

My quick notes would look as follows:

- What is ipv6, notes that it's basically a completely separate protocol 
and might be unexpectedly enabled. Also discussion on link local vs 
external ip addresses (quite a significant change from ipv4)

- Conditions to use it, eg enabling use flags AND noting that the 
"listen" syntax is often different in the app of your choice, eg listen 
[::} vs  listen *

- Pointers on enabling external access to your machine (note I'm seeing 
new providers turn on ipv6 every week, this is a fairly rapidly changing 
situation now).  ie enabling ipv6 tunnels, dhcpv6, autoconfig, etc

- How to disable ipv6.  Sub notes:

a) iptables6 default drop (iptables -P)
b) iptables6 reject
     # ip6tables -A INPUT -j DROP
     # ip6tables -A OUTPUT -j DROP
     # ip6tables -A FORWARD -j DROP
c) sysctl
d) blacklist kernel module or build kernel without support
e) kernel command line option (useful when not modular kernel)
     "ipv6.disable=1"
f) Build specific apps without support (seems pointless though?)
g) Ensure specific apps only listen on ipv4 using config. Check using 
"netstat -l"


Anyone care to kick that around for a bit, maybe pour some sauce on it?

Ed