Full IPv6 / dual-stack support

[TruzThePleasureMan]

IPv6 adoption is accelerating and many hosting customers expect it

Current state (tested on Ubuntu 24.04, OpenPanel 1.7.52):

Component IPv6 support Notes
Caddy (ports 80/443) Yes Listens on * (dual-stack)
OpenPanel UI (2083) Yes Listens on 0.0.0.0 and [::]
OpenAdmin (2087) No Only 0.0.0.0
Docker bridge networking No EnableIPv6: false in daemon.json
Mail (Postfix/Dovecot) No POSTFIX_INET_PROTOCOLS=ipv4, DOVECOT_INET_PROTOCOLS=ipv4
FTP (vsftpd container) Unknown Likely IPv4-only
BIND9 DNS Unknown May support both, untested

Proposed implementation:

• Enable EnableIPv6: true and configure fixed-cidr-v6 in Docker daemon config
• Add IPv6 listening to OpenAdmin (gunicorn bind address)
• Default mail server env vars to all instead of ipv4 for inet protocols
• Add AAAA record support to the DNS zone template for new domains
• Allow per-user IPv6 address assignment (e.g., a /128 from a delegated /48)
• Update Sentinel Firewall rules to handle ip6tables alongside iptables

Benefit: Hosting providers can offer dual-stack hosting, which is increasingly expected by customers. IPv4 exhaustion makes this a competitive differentiator.

[stefanpejcic]

I don’t have access to two IPv6 servers to test this. If you have one available or some time, could you share the login via Discord, or try configuring it yourself and let me know the steps you used? I'll do my best to automate the process from there.

as you mentioned, we should:

• Enable EnableIPv6: true and configure fixed-cidr-v6 in Docker daemon config
• Add IPv6 listening to OpenAdmin (gunicorn bind address)
• Default mail server env vars to all instead of ipv4 for inet protocols
• Add AAAA record support to the DNS zone template for new domains (this already exists, if you have ipv6 only server, template zone_template_ipv6.txt should be used)
• Allow per-user IPv6 address assignment (e.g., a /128 from a delegated /48)
• Update Sentinel Firewall rules to handle ip6tables alongside iptables

and then:

• Add IPv6 listening to OpenPanel (gunicorn bind address)
• Edit OpenPanel UI to use ipv6 only
• Edit OpenAdmin UI to use ipv6 only
• Edit opencli commands to use ipv6 only