Add support for host aliases when using MagicDNS?

[VolatileDream]

Feature request

Expose a way to map multiple hostnames to an existing device, assuming they all belong to the same namespace. I'm only asking for the ability to map hostnames that would be inside the tailnet, to other names that are inside the tailnet.

This is effectively DNS CNAME records, but I would like to configure them in Headscale. I would consider it more usable if I didn't have to rely on another DNS resolver providing the CNAME resolution for things inside my tailnet.

For example:

webhost-1.machines.<tailnet> -> server.machines.<tailnet>
webhost-2.machines.<tailnet> -> server.machines.<tailnet>
webhost-3.machines.<tailnet> -> server.machines.<tailnet>

But I would not want to support:

google.com.             -> server.machines.<tailnet>
test.machines.<tailnet> -> duckduckgo.com.

I'm not asking cross namespace support (eg: some.machine.<tailnet> -> other.namespace.<tailnet>) but I can see uses for it, so others may chime in to request it.

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Tailscale is building support for tailcfg.DNSConfig.ExtraRecords: a way to pass around extra DNS records for use with MagicDNS. It appears that it currently supports A and AAAA records, but based on filed issues, it may grow to support CNAME (in some limited capacity).

I would like to request that once possible CNAME records are added to the Headscale configuration. But perhaps in the meantime, this could be implemented via A and AAAA records?

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I currently have a system with multiple web services configured using a reverse proxy to route traffic. I'd like to expose it as a single tailscale node, rather than splitting each service out and creating more tailscale nodes, and mapping multiple hostnames keeps the reverse proxy functioning.

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Collection of related Tailscale issues:

• Add AAAA records to MagicDNS tailscale/tailscale#1152
• FR: Support custom records in MagicDNS tailscale/tailscale#1543
• FR: DNS aliases for machine names tailscale/tailscale#4457
• Unable to follow CNAME to magic dns record tailscale/tailscale#5033

[madjam002]

I have a patch that allows setting DNS extra_records in the headscale config that I've been using since December, it works pretty well for my use case.

madjam002@b9f05fc

You can then add to your headscale config.yaml

dns_config:
  extra_records:
    - { name: "xxx.yyy.zzz", type: "A", value: "100.x.x.x" }

I haven't opened a PR with this because I think there's a better way of doing it for more complex setups. E.g a lambda function could be passed in config that takes the Tailscale node as an argument and could then return a specialised set of extra_records depending on the node that it's being sent to.

[VolatileDream]

Thanks! That would work perfectly for what I have in mind.

I haven't opened a PR with this because I think there's a better way of doing it for more complex setups.

That makes sense. I hadn't thought of more complicated cases. I was trying to restrict my request to something that wouldn't be controversial to implement, and probably not have behaviour interesting enough to have security implications.

[juanfont]

This is now merged.