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# Tailscale

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- WireGuard

Tailscale builds on top of WireGuard and provides OAuth2 (SSO), OpenID, and SAML authentication for peers to build a mesh network. It is crossplatform, has ACL settings and internal DNS.

## Installation

Install tailscale and reboot your system.

It is also possible to run tailscale as a Docker container. This way, one can run multiple exit nodes on a single machine, each with its own tailnet.

### Third-party clients

- KTailctl — GUI to monitor and manage Tailscale.

  https://github.com/f-koehler/KTailctl || ktailctlAUR

- trayscale — An unofficial GUI wrapper for the Tailscale CLI client.

  https://github.com/DeedleFake/trayscale || trayscaleAUR

- tailscaledesktop — Unnofficial Tailscale desktop application.

  https://gitlab.com/tailscaledesktop/application || tailscaledesktopAUR

- tailscale-systray-git — Linux port of tailscale system tray menu.

  https://github.com/mattn/tailscale-systray || tailscale-systray-gitAUR

## Usage

To use tailscale, enable/start `tailscaled.service` and run the server as follows:

    # tailscale up

You can authenticate a headless machine by specifying the auth key:

    # tailscale up --authkey=tskey-KEY

Note By default tailscale will send logs to their servers for central storage. You may want to opt out with one of the following steps:

- Edit `/etc/default/tailscaled` to include `TS_NO_LOGS_NO_SUPPORT=true`
- Edit `/etc/default/tailscaled` and add `--no-logs-no-support` to `FLAGS`

If you opt out of centralized logging, Tailscale may not be able to provide technical support.

## Advanced usage

### Using a custom Control Server

Using a custom control server like headscale is possible.

To login run

    # tailscale up --login-server https://example.com

On headless systems a non-interactive login using a token is possible.

    # tailscale up --login-server https://example.com --authkey your_auth_key

You may create user and auth-key using following commands after starting `headscale.service`:

    # headscale users create USER -e email@example.com
    # headscale users list
    # headscale preauthkeys create -u <ID> --reusable

#### Share nodes between users

Create file with policy:

    {
     "tagOwners": {
       "tag:shared": ["user1@"]
     },
     "groups": {
       "group:all": ["user1@", "user2@", "user3@"]
     },
     "acls": [
       {
         "action": "accept",
         "src": ["group:all"],
         "dst": ["tag:shared:*"]
       }
     ]
    }

Point this file in config.yaml:

    policy:
     mode: file
     path: "/etc/headscale/policy.json"

Advertise tag:

     tailscale up --advertise-tags=tag:shared --login-server=https://headscale.localdomain/

#### Integration with nextcloud or another OIDC provider

Install nextcloud-app-oidcAUR and create client key, use https://headscale.localdomain/oidc/callback as redirection uri.

Add following snippet into config.yaml:

    oidc:
     issuer: "https://cloud.example.com"
     client_id: "<client-id>"
     client_secret: "<client-secret>"
     scope: ["openid", "profile", "email"]
     user_map:
       name: "preferred_username"
       email: "email"

### Running as a Docker container

Follow this guide for a general idea of how to run tailscale as a docker container.

#### As an exit node

In order to be able to use a tailscale instance running as a docker container as an exit node, we need to use a smaller MTU for the container's network. This is due to an MTU-related issue.

If you do not have one already, create a custom network:

    # docker network create --opt com.docket.network.driver.mtu=1280 my_custom_network

Then, use that network for the container instance:

    # docker run --detach --name=my_tailscale_container --network=my_custom_network --volume /var/lib/tailscale-exitnode-1:/var/lib/tailscale --env TS_STATE_DIR=/var/lib/tailscale --env TS_USERSPACE=1 --env TS_AUTHKEY=tskey-auth-XXX --env TS_EXTRA_ARGS='--advertise-exit-node' tailscale/tailscale

Note that:

- By default, docker will create a network of type `bridge`, so no need to specify it here.
- Use an auth key to authenticate the node. Authenticating with the regular SSO method usually takes too long, and the process may time out before initial authentication is successful.
- Define `TS_USERSPACE=1` so that the container does not need elevated permissions (`CAP_NET_ADMIN` and `CAP_NET_RAW`).
- Bind mount an unused directory on the host (`/var/lib/tailscale-exitnode-1`) to `/var/lib/tailscale` inside the container, and also define `TS_STATE_DIR=/var/lib/tailscale`, so that tailscale will use a persistent state file. Without these, the exit node will use volatile memory to keep state, and thus get a new ID and tailnet IP address every time the container is restarted.

## Tips and tricks

### Using with NetworkManager

If you use NetworkManager, you may notice connection issues with other devices within your tailnet. This is due to a management conflict that is happening between NetworkManager and tailscaled.

To clear this up, we need NetworkManager to unmanage the tailscale network devices (e.g. `tailscale0`).

To do so, simply create a config like `/etc/NetworkManager/conf.d/99-tailscale.conf` with the contents of:

    [keyfile]
    unmanaged-devices=interface-name:tailscale0

Then restart `NetworkManager.service` and `tailscaled.service`.

You may also need to cycle tailscale:

    # tailscale down
    # tailscale up

After this, you should be able to `ping` other devices on your tailnet.

### Magic DNS

Tailscale expects system with working systemd-resolved to set up DNS server and search suffixes from tailnet configuration, otherwise it tries to overwrite `/etc/resolv.conf`.

### Security Hardening

Tailscale can be made to run in its own user and with just the capabilities it needs to operate. See the official knowledge base article for detail.

## Troubleshooting

### Tailscale crash on launch

After starting `tailscaled.service`, it may crash and get stuck on a restart loop. This may be due to the absence of the tun kernel module. To verify that this is indeed the case, view the logs of `tailscaled.service` via systemd

    # systemctl status tailscaled.service

Or, run the binary as root in your terminal

    # /usr/sbin/tailscaled

The following, or similar error may appear in systemctl status or by running the binary:

    ...is CONFIG_TUN enabled in your kernel? modprobe tun failed with: modprobe: FATAL: Module tun not found in directory /lib/modules/5.17.4-arch1-1 kernel/drivers/net/tun.ko found on disk, but not for current kernel; are you in middle of a system update and haven't rebooted? found: /lib/modules/5.17.8-arch1-1/kernel/drivers/net/tun.ko.zst wgengine.NewUserspaceEngine(tun "tailscale0") error: tstun.New("tailscale0"): no such device

If so, simply reboot your system and observe if `tailscaled.service` is active instead of loaded with systemctl status.

## See also

- https://tailscale.com/
- https://github.com/juanfont/headscale

Categories:

- Virtual Private Network
- Secure Shell

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