IPv6.sh for stateful config from router advertisements

#!/bin/bash
#IPv6.sh - RA allocation version

# IFACE is our public facing ethernet interface.
EXT=eth0
FORWARD=0
IPV6SUFFIX=:0f04:de5:1925:80

# Needs router discovery v6
if [ ! $(which rdisc6) ]; then apt install ndisc6; done

# Do not accept router advertisements.
# We will request them manually.
sysctl -w net.ipv6.conf.all.disable_ipv6=1
sysctl -w net.ipv6.conf.all.disable_ipv6=0
sysctl -w net.ipv6.conf.all.accept_ra=0
sysctl -w net.ipv6.conf.default.accept_ra=0
sysctl -w net.ipv6.conf.$EXT.accept_ra=0
# Wait for IPv6 to be ready.
sleep 2

# Get router information
rdisc6 -1 $EXT > /tmp/ipv6info
IPV6PREFIX=`cat /tmp/ipv6info | grep Prefix | cut -d':' -f2- | cut -d' ' -f2 | cut -d':' -f1-4`
IPV6ROUTER=`cat /tmp/ipv6info | grep from | cut -d' ' -f3`

echo "IPv6 prefix detected: $IPV6PREFIX"
ip -6 addr replace ${IPV6PREFIX}${IPV6SUFFIX} dev $EXT home
echo "IPV6 address added to external interface $EXT: ${IPV6PREFIX}${IPV6SUFFIX}"
echo -n $IPV6PREFIX > /etc/ipv6-network

# And make the default route semi-permanent
echo "IPv6 gateway set: $IPV6ROUTER"
ip -6 route replace default via $IPV6ROUTER dev $EXT