WireGuard VPN networking for unprivileged network namespaces

wireguard4netns is directly inspired by the awesome work of the authors of slirp4netns. Instead of providing generic user-mode networking for unprivileged network namespaces through libslirp, wireguard4netns brings network access to the containers through wireguard-go, a userspace WireGuard VPN tunnel implementation.

Motivation

We were building a framework for developing Edge-Native applications (the Sinfonia project) and for this we split applications into two primary components, a frontend that runs on the user's device and a backend consisting of one or more services are deployed on a nearby Kubernetes cluster (cloudlet). We leverage WireGuard tunnels between the two to avoid having to expose deployed services to the world, the frontend's network environment is as if it was part of the same deployment inside the same Kubernetes cluster and namespace as the backend. This hides most of the unnecessary network details from the application's frontend and provides other advantages such as privacy and network mobility.

The main disadvantage was that root privileges are needed to create, configure and attach the in-kernel WireGuard interface to a network namespace. This required either sudo access by the user, or an administrator installed setuid root binary helper. However slirp4netns showed the path to an alternative approach, create a tuntap interface inside the unprivileged network namespace and pass the control socket back to the default namespace where (in our case) a userspace WireGuard implementation is started. All frontend traffic is then sent through the tunnel to a VPN endpoint on the nearby cloudlet which passes it along to the deployed namespace of the application's backend.

Building from source

The only executable that is needed is patch. The build will try to download a copy of golang and use that to build a custom wireguard-go binary.

Make sure you have an initialized and updated wireguard-go git-submodule.

    git clone ... wireguard4netns
    cd wireguard4netns/
    git submodule update --init
    poetry build

The wireguard-go binary is then placed at src/wireguard4netns/wireguard-go. As long as that binary is present in that location, the build will avoid rebuilding the wireguard-go code.

We use a custom built version of wireguard-go because starting with an existing tunnel socket fd is really just an artifact of how the unmodified wireguard-go process sets up the tuntap device and uapi socket in the foreground and then daemonizes itself, passing along the already open file descriptors. With our approach the tuntap device ends up being created in a different network namespace and wireguard-go was unable to query or set the MTU.

Our modifications simply change the code to not fail when MTU operations are not working and is in wireguard-go.patch.

We also needed to make sure the UAPI socket is placed in a user-writable location instead of /var/run/wireguard. This socketDirectory path is customized through a custom linker flag that we set in build.py at the time we build the binary.

Licenses

wireguard4netns is MIT licensed

Copyright (c) 2022-2023 Carnegie Mellon University
SPDX-License-Identifier: MIT

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
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of the Software, and to permit persons to whom the Software is furnished to do
so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

wireguard-go is MIT licensed

Copyright (C) 2017-2022 WireGuard LLC. All Rights Reserved.
License: MIT

see wireguard-go/LICENSE and wireguard-go/README.md

"WireGuard" is a registered trademark of Jason A. Donenfeld.