Funnel

Expose a machine's service to the internet with tailscale funnel through an ingress node you run, with the attribute, certificates and DNS it needs.

Funnel exposes a service on a machine to the internet, the way Tailscale Funnel does: tailscale funnel 3000 on the machine, and https://laptop.ts.example.com answers from anywhere. The machine terminates TLS with its own certificate; what sits in between is an ingress, a node that takes public TLS connections and hands the bytes to the machine over the tailnet. On Tailscale that is Tailscale’s fleet of ingress servers; here it is a node you run, inside the server or on any machine with a public address.

How it works

The client does not talk to the control server to serve a connection. The ingress reads the server name from the TLS client hello, finds the machine with that MagicDNS name among its peers, and opens the machine’s peer API with the same request Tailscale’s ingress sends. The machine checks three things before it takes the connection: the ingress holds the ingress peer capability (the policy grants it), the machine itself holds the funnel node attribute (the policy grants it too), and its own serve config allows Funnel for that host and port (tailscale funnel set it). Then it terminates TLS and serves as it would on the tailnet.

The ingress sees encrypted bytes only. A machine that has not turned Funnel on refuses every connection, whatever the ingress sends.

Setting it up

Funnel needs three things.

HTTPS certificates. The machine needs a certificate for its MagicDNS name, so certificate assistance must be on with a base domain that is a public zone. That also stamps the https node attribute, which tailscale funnel checks first.

The funnel node attribute, granted by the policy file to the machines that may use Funnel, as on Tailscale:

{
  "nodeAttrs": [{ "target": ["tag:web", "alice@example.com"], "attr": ["funnel"] }]
}

The server adds the ports Funnel may use (443, 8443 and 10000 unless the config says otherwise), and a grant that lets the ingress nodes reach those machines with the ingress capability. Nothing else in the policy needs to mention the ingress.

An ingress node with a public address. The simplest is the one inside the server:

funnel:
  enabled: true
  # The public addresses to accept TLS on; one per Funnel port.
  listen_addrs: [":443", ":8443", ":10000"]
  # The ingress node's keys.
  state_dir: /var/lib/slopscale/ingress
  # The ports Funnel may be turned on for.
  ports: [443, 8443, 10000]

It joins the tailnet as slopscale-ingress with the tag tag:slopscale-ingress, approved and shown among the machines. If the server itself listens on port 443, give the ingress another address or put it on another machine; the server refuses to start with an address another of its listeners already uses.

An ingress on another machine, such as a small VPS in front of a server behind NAT, runs with the same binary and a tagged pre-auth key:

$ slopscale preauthkeys create --tags tag:slopscale-ingress --preauthorized
$ slopscale ingress --control-url https://control.example.com \
    --auth-key tskey-auth-… --state-dir /var/lib/slopscale-ingress

Several ingress nodes may run at once; public DNS decides which one a client reaches.

Public DNS. The machines’ MagicDNS names must resolve, on the public internet, to the ingress. A wildcard record under the base domain does it once:

*.ts.example.com.  A  203.0.113.7

The names carry no tailnet addresses; they only point clients at the ingress, which delivers by server name.

Using it

On a machine the policy grants Funnel to:

$ tailscale funnel 3000
Available on the internet:

https://laptop.ts.example.com/
|-- proxy http://127.0.0.1:3000

tailscale funnel fails with its own message when the attribute is missing, when HTTPS is off, or when no ingress node has joined the tailnet. The machine reports Funnel in its Hostinfo, so the console marks it with a funnel icon on the machines list and the machine page says Funnel: On. The Server page shows how many ingress nodes have joined and whether the embedded one is running.

What is different from Tailscale

The ingress is yours: it is the machine the public reaches, and it needs a public address and the Funnel ports open.
Only MagicDNS names are delivered. A name of your own on a Funnel port (a client’s bring your own domain) is not found by the ingress.
Funnel-based tls-alpn-01 certificate renewal works through the ingress like any other connection; first issuance still uses DNS-01 through certificate assistance.