Description

Since upgrading to Garden-runC 1.9.4 we've observed that a few test frameworks now fail (notably, Selenium) on our BOSH deployed Concourse instances. They fail with the following error:

Errno::EAFNOSUPPORT:
       Address family not supported by protocol - socket(2) for "::1" port 9515

It looks like it's finding the IPv6 loopback entry and trying to use it, even though it's not supported by the kernel. We've submitted a patch to have Selenium swallow this error, but it seems more correct to not put an unsupported address in /etc/hosts in the first place; today it's Selenium, who knows what else may be confused.

Steps to reproduce

• Guardian release version: 1.9.4
• Linux kernel version: 4.4.0
• Concourse version: 3.5.1 release candidate (we haven't shipped a version with 1.9.4 yet)
• Go version: 1.9

Here's our steps:

1. BOSH-deployed Concourse or just Garden

2. Run the following in a container (this is what Selenium does, distilled):

   require "socket"
   
   Socket.getaddrinfo('localhost', 8080).map { |e| e[3] }.each do |i|
     TCPServer.new(i, 0).tap { |s| p [i, s] }.close
   end

3. No errors should be raised.

The tl;dr is that Socket.getaddrinfo('localhost', 8080) is what returns the ::1 address, which it then tries to listen on.

/cc @topherbullock