Ubuntu 22.04 with docker-ce in IPv6 only environment

docker-ipv6-install.sh

# Assumptions:
#   - Ubuntu 22.04
#   - Docker CE
#   - IPv6 only environment
#   - Using netplan for IPv6 addressing
#   - IPv6 /64 assigned to host
#   - UFW in use (and DNS to be allowed) - otherwise skip the ufw config

# (The above is the Hetzner default)

apt -y update && apt -y upgrade && apt -y dist-upgrade

sudo apt-get install ca-certificates curl gnupg lsb-release

sudo mkdir -p /etc/apt/keyrings && curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg

echo \
  "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu \
  $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

apt -y update && apt -y install docker-ce

sed 's/dhcp4: true/dhcp4: false/g' -i /etc/netplan/50-cloud-init.yaml && chmod 700 /etc/netplan/50-cloud-init.yaml && netplan apply

ipv6prefix=$(ip addr |grep inet6|grep -v fe80|grep -v ::1/128|xargs|cut -d " " -f 2|cut -d "/" -f 1|cut -d ':' -f -5)
ipv6dns=$(resolvectl status|grep Current|cut -d ":" -f 2-|grep '[a-f0-9]:[a-f0-9]'|xargs)

mkdir -p /etc/docker
echo -e '{\n  "ipv6": true,\n  "fixed-cidr-v6": "'$ipv6prefix'1000::/68",\n  "dns": ["'$ipv6dns'"],\n  "userland-proxy": false\n}' > /etc/docker/daemon.json

# No NATv6 needed, we're routing
# ip6tables -t nat -A POSTROUTING -s "$ipv6prefix"1000::/68 ! -o docker0 -j MASQUERADE && apt install -y iptables-persistent

sed 's/^COMMIT$/# COMMIT/g' -i /etc/ufw/before6.rules
echo '' >> /etc/ufw/before6.rules
echo '# Allow DNS traffic from containers to DNS server' >> /etc/ufw/before6.rules
echo '-A ufw6-before-forward -s '$ipv6prefix'1000::/68 -d '$ipv6dns' -p udp --dport 53 -j ACCEPT' >> /etc/ufw/before6.rules
echo '-A ufw6-before-forward -s '$ipv6prefix'1000::/68 -d '$ipv6dns' -p tcp --dport 53 -j ACCEPT' >> /etc/ufw/before6.rules
echo '' >> /etc/ufw/before6.rules
echo '# Allow DNS traffic from DNS server to containers (optional)' >> /etc/ufw/before6.rules
echo '-A ufw6-before-forward -s '$ipv6dns' -d '$ipv6prefix'1000::/68 -p udp --sport 53 -j ACCEPT' >> /etc/ufw/before6.rules
echo '-A ufw6-before-forward -s '$ipv6dns' -d '$ipv6prefix'1000::/68 -p tcp --sport 53 -j ACCEPT' >> /etc/ufw/before6.rules
echo '' >> /etc/ufw/before6.rules
echo 'COMMIT' >> /etc/ufw/before6.rules

ufw reload

echo 'net.ipv6.conf.default.forwarding=1' >> /etc/sysctl.conf && sysctl -p /etc/sysctl.conf
echo 'net.ipv6.conf.eth0.proxy_ndp=1' >> /etc/sysctl.conf && sysctl -p /etc/sysctl.conf
echo 'net.ipv6.conf.all.forwarding=1' >> /etc/sysctl.conf && sysctl -p /etc/sysctl.conf