Detect Azure when DHCP domain is set to reddog.microsoft.com

Signed-off-by: Jason Barnett <jason.w.barnett@gmail.com>

lib/ohai/plugins/azure.rb

@@ -34,7 +34,7 @@
       azure Mash.new
       azure_metadata_from_hints.each { |k, v| azure[k] = v }
       azure["metadata"] = parse_metadata
-    elsif has_waagent? || has_dhcp_option_245?
+    elsif has_waagent? || has_dhcp_option_245? || has_reddog_dhcp_domain?
       logger.trace("Plugin Azure: No hints present, but system appears to be on Azure.")
       azure Mash.new
       azure["metadata"] = parse_metadata
@@ -67,6 +67,26 @@ def has_dhcp_option_245?
     has_245
   end
 
+  def has_reddog_dhcp_domain?
+    tcp_ip_dhcp_domain == "reddog.microsoft.com"
+  end
+
+  def tcp_ip_dhcp_domain
+    return unless RUBY_PLATFORM.match?(/mswin|mingw32|windows/)
+
+    require "win32/registry" unless defined?(Win32::Registry)
+
+    begin
+      key = Win32::Registry::HKEY_LOCAL_MACHINE.open("SYSTEM\\CurrentControlSet\\Services\\Tcpip\\Parameters")
+      dhcp_domain = key["DhcpDomain"]
+      Ohai::Log.trace("Plugin Azure: DhcpDomain registry value is #{dhcp_domain}")
+    rescue Win32::Registry::Error
+      Ohai::Log.trace("Plugin Azure: DhcpDomain registry value cannot be found")
+    end
+
+    dhcp_domain
+  end
+
   # create the basic structure we'll store our data in
   def initialize_metadata_mash_compute
     metadata = Mash.new

spec/unit/plugins/azure_spec.rb

@@ -72,6 +72,49 @@
     end
   end
 
+  context "when on windows", :windows_only do
+    let(:plugin) do
+      get_plugin("azure").tap do |plugin|
+        plugin[:platform_family] = "windows"
+      end
+    end
+
+    let(:tcpip_reg_key) { "SYSTEM\\CurrentControlSet\\Services\\Tcpip\\Parameters" }
+    let(:win_reg_double) { instance_double("Win32::Registry") }
+
+    before do
+      allow(Win32::Registery::HKEY_LOCAL_MACHINE)
+        .to receive(:open)
+        .with(tcpip_reg_key)
+        .and_return(win_reg_double)
+      allow(win_reg_double).to receive(:[]).with("DhcpDomain").and_return("domain.com")
+    end
+
+    context "without azure hint file or agent" do
+      before do
+        allow(plugin).to receive(:hint?).with("azure").and_return(false)
+        allow(plugin).to receive(:has_waagent?).and_return(false)
+        allow(plugin).to receive(:has_dhcp_option_245?).and_return(false)
+      end
+
+      context "DHCP option 15 is set to reddog.microsoft.com" do
+        before do
+          allow(win_reg_double).to receive(:[]).with("DhcpDomain").and_return("reddog.microsoft.com")
+        end
+
+        it_behaves_like "azure"
+      end
+
+      context "DHCP option 15 is not set to reddog.microsoft.com" do
+        before do
+          allow(win_reg_double).to receive(:[]).with("DhcpDomain").and_return("domain.com")
+        end
+
+        it_behaves_like "!azure"
+      end
+    end
+  end
+
   describe "with azure hint file" do
     before do
       allow(plugin).to receive(:hint?).with("azure").and_return(hint)