No default route in Ubuntu box after restart

[carlosefr]

Vagrant version

Vagrant 1.8.6

Host operating system

MacOS X 10.11.6 (El Capitan)

Guest operating system

Ubuntu 16.04 x64 (Xenial)

Vagrantfile

https://github.com/Probely/CTF-Challenges/blob/32b69713cad8c36f8dfdc2f3c3f62eb7b39ecb03/Vagrantfile

The Vagrant file is long, but the relevant bit is the presence of a private network (more details below).

Expected behavior

After being created, the VM can reach the internet just fine. After restarting it this should still be the case.

Actual behavior

The VM cannot reach the internet anymore after being restarted.

Steps to reproduce

1. vagrant up
2. vagrant halt
3. vagrant up

Comment

The VM has two network interfaces, ensp0s3 (NAT) and ensp0s8 (private network). I've observed that after restarting the VM, the interfaces remain the same and so does the output of ifconfig.

What doesn't stay the same is the contents of /etc/network/interfaces. After initialization it contains this relevant bit:

#VAGRANT-BEGIN
# The contents below are automatically generated by Vagrant. Do not modify.
auto enp0s8
iface enp0s8 inet dhcp
    post-up route del default dev $IFACE || true
#VAGRANT-END

This removes the default route from the private network interface, which is OK. But after restarting the VM, it changes to this:

#VAGRANT-BEGIN
# The contents below are automatically generated by Vagrant. Do not modify.
auto enp0s3
iface enp0s3 inet dhcp
    post-up route del default dev $IFACE || true
#VAGRANT-END

It now removes the default route from the NAT interface, which breaks things.

I haven't figured out why this happens considering the interfaces themselves didn't change between boots.

[carlosefr]

I think I understand what's happening here...

The provisioning script called from the Vagrantfile installs Docker, which creates a docker0 interface. Vagrant is sorting the interfaces and removing the default route from the second one, which happens to be the wrong one. The debug output seems to indicate exactly this:

DEBUG network_interfaces: Unsorted list: ["enp0s3", "enp0s8", "docker0"]
DEBUG network_interfaces: Sorted list: ["docker0", "enp0s3", "enp0s8"]

[chrisroberts]

Hi! This has been addressed in #7866 and will be fixed in the next release. Thanks!

[carlosefr]

Ok, I patched my 1.8.6 and the fix seems to work.

[ghost]

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