rkt: Don't require port_map with host networking

Also don't try to return a DriverNetwork with host networking. None will
ever exist as that's the point of host networking: rkt won't create a
network namespace.

CHANGELOG.md

@@ -45,6 +45,7 @@ BUG FIXES:
  * client: Fix allocation accounting in GC and trigger GCs on allocation
    updates [GH-3445]
  * driver/rkt: Remove pods on shutdown [GH-3562]
+ * driver/rkt: Don't require port maps when using host networking [GH-3615]
  * template: Fix issue where multiple environment variable templates would be
    parsed incorrectly when contents of one have changed after the initial
    rendering [GH-3529]

client/driver/rkt.go

@@ -529,6 +529,9 @@ func (d *RktDriver) Start(ctx *ExecContext, task *structs.Task) (*StartResponse,
 		if len(driverConfig.PortMap) > 0 {
 			return nil, fmt.Errorf("Trying to map ports but no network interface is available")
 		}
+	} else if network == "host" {
+		// Port mapping is skipped when host networking is used.
+		d.logger.Println("[DEBUG] driver.rkt: Ignoring port_map when using --net=host")
 	} else {
 		// TODO add support for more than one network
 		network := task.Resources.Networks[0]
@@ -657,15 +660,19 @@ func (d *RktDriver) Start(ctx *ExecContext, task *structs.Task) (*StartResponse,
 	}
 	go h.run()
 
-	d.logger.Printf("[DEBUG] driver.rkt: retrieving network information for pod %q (UUID %s) for task %q", img, uuid, d.taskName)
-	driverNetwork, err := rktGetDriverNetwork(uuid, driverConfig.PortMap)
-	if err != nil && !pluginClient.Exited() {
-		d.logger.Printf("[WARN] driver.rkt: network status retrieval for pod %q (UUID %s) for task %q failed. Last error: %v", img, uuid, d.taskName, err)
+	// Only return a driver network if *not* using host networking
+	var driverNetwork *cstructs.DriverNetwork
+	if network != "host" {
+		d.logger.Printf("[DEBUG] driver.rkt: retrieving network information for pod %q (UUID %s) for task %q", img, uuid, d.taskName)
+		driverNetwork, err = rktGetDriverNetwork(uuid, driverConfig.PortMap)
+		if err != nil && !pluginClient.Exited() {
+			d.logger.Printf("[WARN] driver.rkt: network status retrieval for pod %q (UUID %s) for task %q failed. Last error: %v", img, uuid, d.taskName, err)
 
-		// If a portmap was given, this turns into a fatal error
-		if len(driverConfig.PortMap) != 0 {
-			pluginClient.Kill()
-			return nil, fmt.Errorf("Trying to map ports but driver could not determine network information")
+			// If a portmap was given, this turns into a fatal error
+			if len(driverConfig.PortMap) != 0 {
+				pluginClient.Kill()
+				return nil, fmt.Errorf("Trying to map ports but driver could not determine network information")
+			}
 		}
 	}
 

client/driver/rkt_test.go

@@ -519,6 +519,72 @@ func TestRktDriver_PortsMapping(t *testing.T) {
 	}
 }
 
+// TestRktDriver_PortsMapping_Host asserts that port_map isn't required when
+// host networking is used.
+func TestRktDriver_PortsMapping_Host(t *testing.T) {
+	if !testutil.IsTravis() {
+		t.Parallel()
+	}
+	if os.Getenv("NOMAD_TEST_RKT") == "" {
+		t.Skip("skipping rkt tests")
+	}
+
+	ctestutils.RktCompatible(t)
+	task := &structs.Task{
+		Name:   "etcd",
+		Driver: "rkt",
+		Config: map[string]interface{}{
+			"image": "docker://redis:latest",
+			"net":   []string{"host"},
+		},
+		LogConfig: &structs.LogConfig{
+			MaxFiles:      10,
+			MaxFileSizeMB: 10,
+		},
+		Resources: &structs.Resources{
+			MemoryMB: 256,
+			CPU:      512,
+			Networks: []*structs.NetworkResource{
+				{
+					IP:            "127.0.0.1",
+					ReservedPorts: []structs.Port{{Label: "main", Value: 8080}},
+				},
+			},
+		},
+	}
+
+	ctx := testDriverContexts(t, task)
+	defer ctx.AllocDir.Destroy()
+	d := NewRktDriver(ctx.DriverCtx)
+
+	if _, err := d.Prestart(ctx.ExecCtx, task); err != nil {
+		t.Fatalf("error in prestart: %v", err)
+	}
+	resp, err := d.Start(ctx.ExecCtx, task)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	if resp.Network != nil {
+		t.Fatalf("No network should be returned with --net=host but found: %#v", resp.Network)
+	}
+
+	failCh := make(chan error, 1)
+	go func() {
+		time.Sleep(1 * time.Second)
+		if err := resp.Handle.Kill(); err != nil {
+			failCh <- err
+		}
+	}()
+
+	select {
+	case err := <-failCh:
+		t.Fatalf("failed to kill handle: %v", err)
+	case <-resp.Handle.WaitCh():
+	case <-time.After(time.Duration(testutil.TestMultiplier()*15) * time.Second):
+		t.Fatalf("timeout")
+	}
+}
+
 func TestRktDriver_HandlerExec(t *testing.T) {
 	if !testutil.IsTravis() {
 		t.Parallel()