Tailscale

This guide walks you through configuring Tailscale networking for use inside Coder workspaces. With Tailscale networking, you can access services running inside Coder and services running on your tailnet (Tailscale private network).

Creating the image

As part of this tutorial, you'll create an image with the following that you'll use to create new Coder workspaces. The container image will include:

The Tailscale daemon (tailscaled)
A transparent proxy tool (proxychains4)
Environment variables to control proxy behavior for outbound connections
A SOCKS5 proxy included in tailscaled to facilitate connections to the tailnet, listening on localhost:1080
An HTTP proxy included in tailscaled to facilitate connections to the tailnet, listening on localhost:3128

Limitations

This guide describes how to install Tailscale in a Ubuntu base image using the package manager and running it in userspace networking mode. As such:

The image (which you will create as part of this tutorial) requires container-based virtual machine workspaces, so that systemd can start the Tailscale daemon (tailscaled)
Users will require sudo access to configure the Tailscale tunnel
Inbound connections from other devices on the tailnet to your workspace will appear to originate from localhost
Outbound connections to other devices on the tailnet will require support for HTTP proxies; otherwise, you'll need to use a wrapper such as proxychains4
The example in this article applies to Ubuntu 20.04 LTS (Focal Fossa), so you may need to adapt it for compatibility with your preferred base image

Tailscale does not require root access to operate in userspace networking mode, and the requirement to use container-based virtual machine workspaces applies only to the instructions in this guide. Contact our support team if you are interested in using Tailscale in your Coder workspace without root access.

Step 1: Create the Dockerfile

In Coder, developer workspaces are defined by a Dockerfile that contains the apps, tools, and dependencies that you need to work on the project.

See our custom image docs and Docker’s guide to writing Dockerfiles for more information.

To simplify creating and maintaining the image, we recommend structuring your source code so that files added or modified in the image match the hierarchy of the target files, in a subdirectory called files:

.
├── Dockerfile
└── files
    ├── etc
    │   ├── apt
    │   │   ├── preferences.d
    │   │   │   └── tailscale
    │   │   └── sources.list.d
    │   │       └── tailscale.list
    │   └── systemd
    │       └── system
    │           └── tailscaled.service.d
    │               └── tailscale.conf
    └── usr
        └── share
            └── keyrings
                └── tailscale.gpg

While it is possible to configure everything directly in a single Dockerfile, we recommend using a folder hierarchy, since this makes it easier to create a reproducible image and examine the change history for individual files.

Create the folder hierarchy:

mkdir --parents \
    files/etc/apt/preferences.d \
    files/etc/apt/sources.list.d \
    files/etc/systemd/system/tailscaled.service.d \
    files/usr/share/keyrings

Then, create the following files (we'll walk you through the contents of each in the following steps):

touch files/etc/apt/preferences.d/tailscale \
    files/etc/apt/sources.list.d/tailscale.list \
    files/etc/systemd/system/tailscaled.service.d/tailscale.conf

Step 1a: Add image repository

Add the Tailscale package repository to tailscale.list in the local path files/etc/apt/sources.list.d. This will appear in /etc/apt/sources.list.d in the resulting image, with the following contents:

deb [signed-by=/usr/share/keyrings/tailscale.gpg] https://pkgs.tailscale.com/stable/ubuntu focal main

This configures apt and apt-get to install packages from the Tailscale repository and verify package signatures with the specified public key.

Step 1b: (Optional) Configure package pinning

For improved security, you can configure apt to deny package installation from a given repository by default and allow specific packages by name. To do this, create files/etc/apt/preferences.d/tailscale with the following contents:

# Ignore all packages from this repository by default
Package: *
Pin: origin pkgs.tailscale.com
Pin-Priority: 1

Package: tailscale
Pin: origin pkgs.tailscale.com
Pin-Priority: 500

Step 1c: Add the signing key for Tailscale package repository

Retrieve the signing key from Tailscale, and store the binary (dearmored) key file in files/usr/share/keyrings/tailscale.gpg:

curl --silent --show-error --location "https://pkgs.tailscale.com/stable/ubuntu/focal.gpg" | \
    gpg --dearmor --yes --output=files/usr/share/keyrings/tailscale.gpg

Step 1d: Override default `tailscaled` service settings

By default, tailscaled will store its internal state in a state file located at /var/lib/tailscale/tailscaled.state (this is is ephemeral in Coder). We will need to modify the service settings to:

Store the state file in the persistent home volume (/home/coder)
Enable userspace networking
Enable the SOCKS5 proxy (optional)
Enable the HTTP proxy (optional)

If you do not require outbound connections from the workspace to other services running in the tailnet, you may skip the steps where you configure the proxies.

Override the ExecStart setting for the tailscaled service by saving the following to files/etc/systemd/system/tailscaled.service.d/tailscale.conf:

[Service]
ExecStart=
ExecStart=-/usr/sbin/tailscaled --state=/home/coder/.config/tailscaled.state --socket=/var/run/tailscale/tailscaled.sock --port $PORT --tun=userspace-networking --socks5-server=localhost:1080 --outbound-http-proxy-listen=localhost:3128 $FLAGS

Step 1e: Create the Dockerfile

Create a Dockerfile, build it, and push to an external repository, such as Docker Hub:

FROM codercom/enterprise-base:ubuntu

USER root

# Copy configuration files to appropriate locations
COPY files /

ARG DEBIAN_FRONTEND="noninteractive"

RUN apt-get update && \
    apt-get install --no-install-recommends --yes --quiet \
      netcat-openbsd \
      proxychains4 \
      python3 && \
    apt-get install --no-install-recommends --yes --quiet \
      tailscale && \
    # Delete package cache to avoid consuming space in layer
    apt-get clean && \
    rm -rf /var/lib/apt/lists/*

USER coder

ENV ALL_PROXY=socks5://localhost:1080
ENV http_proxy=http://localhost:3128

Step 2: Authenticate to Tailscale

Create a workspace using the container image. Initially, tailscaled should be running, but it will indicate that it requires authentication:

systemctl status tailscaled

Authenticate using sudo tailscale up, then verify that other network devices are visible:

tailscale status

You may also use a pre-authentication key with tailscale up --authkey to avoid needing to sign in via a web browser.

tailscale should maintain connectivity across workspace rebuilds, since we chose to store the state file in a persistent volume.

Step 3: (Optional) Test Tailscale services

By creating two workspaces from the same image, both authenticated to Tailscale, we can verify connectivity works as expected. In one workspace, run the Python web server:

python3 -m http.server 3000

In another workspace, verify that tailscaled is listening for connections on the configured proxy ports:

ss -nltp

Check that the http_proxy environment variable is set to the address of the local tailscaled proxy:

env | grep -i proxy

Run curl (which respects the http_proxy command) to connect to the webserver running in the other workspace. Since we proxy the connection through the local tailscaled instance, we can use the internal hostname:

curl http://jawnsy-tailscale-1:3000

For applications that do not respect the http_proxy or ALL_PROXY environment variables, consider using a tool like proxychains4 to intercept the socket system calls and transparently route traffic through the proxy.