id,summary,reporter,owner,description,type,status,component,version,resolution,keywords,cc,guest,host
15074,AAAA lookups to natdnshostresolver break NAT networking,fons,,"In my OSX 10.11.1 host I create a Linux guest with --natdnshostresolver1 on. Then, on the Linux guest, AAAA DNS lookups to "".local"" domains which don't exist make NAT networking inoperable.

Doring each lookup, all other connections to/from NAT interface are unresponsive between 5 to 10 seconds. No traffic goes through, not even ICMP (see https://github.com/weaveworks/scope/issues/769#issuecomment-174545662 )

I can easily reproducible with vagrant ...


{{{
vagrant up
vagrant ssh
host -t AAAA scope.weave.local # Causes the nat interface to be unresponsive
}}}

... with the following Vagrantfile


{{{
Vagrant.configure(""2"") do |config|
  config.vm.box = ""ubuntu/ubuntu-15.04-amd64""
  config.vm.box_url = ""https://cloud-images.ubuntu.com/vagrant/vivid/current/vivid-server-cloudimg-amd64-vagrant-disk1.box""
  config.vm.provider :virtualbox do |vb|
    vb.customize [""modifyvm"", :id, ""--natdnshostresolver1"", ""on""]
  end
end
}}}

The bug in the NAT resolver may have to do with the OSX's DNS resolver timing out when looking up AAAA records in the .local domain. For instance:


{{{
$ host www.google.com # fine
www.google.com has address 216.58.213.164
www.google.com has IPv6 address 2a00:1450:4009:811::2004
$ host -t AAAA www.google.com # fine
www.google.com has IPv6 address 2a00:1450:4009:811::2004
$ host something.local # not found, but fails as expected
Host something.local not found: 3(NXDOMAIN)
$ host -t AAAA something.local # causes a timeout!
;; connection timed out; no servers could be reached
}}}

This would justify 10 second hangs in the lookups themselves but it shouldn't impact other connections to/from the NAT interface.

More information: https://github.com/weaveworks/scope/issues/769#issuecomment-174521191",defect,closed,network/NAT,VirtualBox 5.0.14,fixed,,,Linux,Mac OS X