Support IPv6 NAT

[pvizeli]

Need: home-assistant/supervisor#3780

[agners]

I tested the dev build (available from https://os-builds.home-assistant.io/9.0.dev2022081102051/), but it seems to still cause Docker not to start successfully. Maybe something is missing in the kernel configuration?

[agners]

Aug 12 15:25:40 homeassistant audit[424]: SYSCALL arch=c000003e syscall=55 success=yes exit=0 a0=4 a1=29 a2=40 a3=7fffc4eac5d0 items=0 ppid=370 pid=424 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm="ip6tables" exe="/usr/sbin/xtables-legacy-multi" subj==unconfined key=(null)
Aug 12 15:25:41 homeassistant dockerd[370]: failed to start daemon: Error initializing network controller: error obtaining controller instance: failed to create NAT chain DOCKER: iptables failed: ip6tables --wait -t nat -N DOCKER: ip6tables v1.8.7 (legacy): can't initialize ip6tables table `nat': Table does not exist (do you need to insmod?)
Aug 12 15:25:41 homeassistant dockerd[370]: Perhaps ip6tables or your kernel needs to be upgraded.

[agners]

Adding CONFIG_IP6_NF_NAT=y does the trick.