fix: read the container IP from NetworkSettings.Networks

lib/kitchen/docker/helpers/container_helper.rb

@@ -12,6 +12,7 @@
 # limitations under the License.
 
 require "erb" unless defined?(Erb)
+require "ipaddr" unless defined?(IPAddr)
 require "json" unless defined?(JSON)
 require "shellwords" unless defined?(Shellwords)
 require "tempfile" unless defined?(Tempfile)
@@ -253,15 +254,47 @@ def run_container(state, transport_port = nil)
           parse_container_id(output)
         end
 
+        # The container's address on the Docker network.
+        #
+        # Read from +NetworkSettings.Networks+ rather than the top-level
+        # +NetworkSettings.IPAddress+. That field was only ever populated for
+        # the default bridge, and Docker 29 removed it altogether -- asking for
+        # it there fails the whole `docker inspect` with "map has no entry for
+        # key \"IPAddress\"", which took +use_internal_docker_network+ with it.
+        # +Networks+ has been present since Docker 1.9, so reading it works on
+        # both.
+        #
+        # A container attached to several networks has an address on each; the
+        # first is used, which is the only one for the single-network case this
+        # option is for.
+        #
         # @param state [Hash] instance state naming the container
         # @return [String] the container's address on the Docker network
         # @raise [Kitchen::ActionFailed] if it cannot be determined
         def container_ip_address(state)
-          cmd = "inspect --format '{{ .NetworkSettings.IPAddress }}'"
+          cmd = "inspect --format '{{range .NetworkSettings.Networks}}{{.IPAddress}} {{end}}'"
           cmd << " #{state[:container_id]}"
-          docker_command(cmd).strip
-        rescue
-          raise ActionFailed, "Error getting internal IP of Docker container"
+          output = docker_command(cmd, suppress_output: !logger.debug?)
+
+          # Picked by parsing rather than by taking the first word, so that a
+          # warning docker writes to stderr is not returned as an address.
+          address = output.split(/\s+/).find { |token| ip_address?(token) }
+          raise ActionFailed, "Docker reports no IP address for the container" if address.nil?
+
+          address
+        rescue => e
+          raise ActionFailed, "Error getting internal IP of Docker container. #{e}"
+        end
+
+        # @param token [String] a candidate address
+        # @return [Boolean] whether it parses as an IPv4 or IPv6 address
+        def ip_address?(token)
+          return false if token.nil? || token.empty?
+
+          IPAddr.new(token)
+          true
+        rescue IPAddr::Error
+          false
         end
 
         # Stops and removes the container.

spec/container_helper_spec.rb

@@ -270,6 +270,58 @@ def helper_answering(inspect_ok:, running: "false")
     end
   end
 
+  describe "#container_ip_address" do
+    def helper_inspecting(output)
+      h = helper
+      @asked = nil
+      allow(h).to receive(:docker_command) { |cmd, _opts = {}| @asked = cmd; output }
+      h
+    end
+
+    let(:state) { { container_id: "abc123abc123" } }
+
+    it "returns the address docker reports" do
+      expect(helper_inspecting("172.17.0.7 \n").container_ip_address(state)).to eq "172.17.0.7"
+    end
+
+    it "reads Networks rather than the removed top-level IPAddress" do
+      # Docker 29 dropped NetworkSettings.IPAddress. Asking for it does not
+      # return empty -- it fails the whole inspect with a template error, which
+      # took use_internal_docker_network down with it.
+      helper_inspecting("172.17.0.7\n").container_ip_address(state)
+      expect(@asked).to include(".NetworkSettings.Networks")
+      expect(@asked).not_to include(".NetworkSettings.IPAddress")
+    end
+
+    it "takes the first address when the container is on several networks" do
+      expect(helper_inspecting("172.17.0.7 172.19.0.2 \n").container_ip_address(state))
+        .to eq "172.17.0.7"
+    end
+
+    it "handles an IPv6 address" do
+      expect(helper_inspecting("2001:db8::2 \n").container_ip_address(state)).to eq "2001:db8::2"
+    end
+
+    it "ignores a warning docker wrote to stderr" do
+      expect(helper_inspecting("WARNING: something happened\n172.17.0.7 \n").container_ip_address(state))
+        .to eq "172.17.0.7"
+    end
+
+    it "fails loudly when docker reports no address" do
+      # Returning "" here would be recorded as the instance hostname, and the
+      # connection would fail somewhere far from the cause.
+      expect { helper_inspecting(" \n").container_ip_address(state) }
+        .to raise_error(Kitchen::ActionFailed, /no IP address/)
+    end
+
+    it "fails loudly when the inspect itself fails" do
+      h = helper
+      allow(h).to receive(:docker_command).and_raise(Kitchen::ShellOut::ShellCommandFailed, "boom")
+      expect { h.container_ip_address(state) }
+        .to raise_error(Kitchen::ActionFailed, /Error getting internal IP/)
+    end
+  end
+
   describe "#remove_container" do
     it "stops the container before removing it" do
       # `docker rm` refuses to remove a running container, so the order matters.