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docker-tuntap-osx

docker-tuntap-osx is a tuntap support shim installer for Docker for Mac.

The Problem

Current on Docker for Mac has no support for network routing into the Host Virtual Machine that is created using hyperkit. The reason for this is due to the fact that the network interface options used to create the instance does not create a bridge interface between the Physical Machine and the Host Virtual Machine. To make matters worse, the arguments used to create the Host Virtual Machine is hardcoded into the Docker for Mac binary with no means to configure it.

How it works

This installer (docker_tap_install.sh) will move the original hyperkit binary (hyperkit.original) inside the Docker for Mac application and instead places our shim (./sbin/docker.hyperkit.tuntap.sh) in its stead. This shim will then inject the additional arguments required to attach a TunTap interface into the Host Virtual Machine, essentially creating a bridge interface between the guest and the host (this is essentially what hvint0 is on Docker for Windows).

From there the up script (docker_tap_up.sh) is used to bring the network interface up on both the Physical Machine and the Host Virtual Machine. Unlike the install script, which only needs to be run once, this up script must be run for every restart of the Host Virtual Machine.

Once done the IP address 10.0.75.2 can be used as a network routing gateway to reach any containers within the Host Virtual Machine:

route add -net <IP RANGE> -netmask <IP MASK> 10.0.75.2

Note: Although as of docker-for-mac version 17.12.0 you do not need the following, for prior versions you will need to setup IP Forwarding in the iptables defintion on the Host Virtual Machine:
(This is not done by the helpers as this is not a OSX or tuntap specific issue. You would need to do the same for Docker for Windows, as such it should be handled outside the scope of this project.)

docker run --rm --privileged --pid=host debian nsenter -t 1 -m -u -n -i iptables -A FORWARD -i eth1 -j ACCEPT

Note: Although not required for docker-for-mac versions greater than 17.12.0, the above command can be replaced with the following if ever needed and is tested to be working on docker-for-windwos as an alternative. This is in case docker-for-mac changes something in future and this command ends up being a necessity once again.

docker run --rm --privileged --pid=host docker4w/nsenter-dockerd /bin/sh -c 'iptables -A FORWARD -i eth1 -j ACCEPT'

Dependencies

Docker for Mac

TunTap

brew cask install tuntap

How to install it

To install it, run the shim installer script. This will automatically check if the currently installed shim is the correct version and make a backup if necessary:

./sbin/docker_tap_install.sh

After this you will need to bring up the network interfaces every time the docker Host Virtual Machine is restarted:

./sbin/docker_tap_up.sh

How to remove it

The uninstall script will simply revert the installer. Restoring the original and removing the shim:

./sbin/docker_tap_uninstall.sh

Projects using docker-tuntap-osx

License

MIT

References & Credits

  • A big thanks to michaelhenkel and strayerror on the Docker forums for the inspiration and help to make this package
  • The original thread on the Docker Forums

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