r/virtual_machine: Correct present NIC device calculation

This corrects an issue with the way NIC devices were checked to see if
the slots they are supposed to occupy on the PCI bus were already used
or not. An offset that was used to populate the current device range was
not being used when the devices were actually checked, creating invalid
results and out of range errors.

Fixes #279.

vsphere/internal/virtualdevice/virtual_machine_network_interface_subresource.go

@@ -870,7 +870,8 @@ func (r *NetworkInterfaceSubresource) assignEthernetCard(l object.VirtualDeviceL
 
 	// Now that we know which units are used, we can pick one
 	newUnit := int32(r.Index) + pciDeviceOffset
-	if units[newUnit] {
+	log.Printf("[TRACE] newUnit: %d", newUnit)
+	if units[newUnit-pciDeviceOffset] {
 		return fmt.Errorf("device unit at %d is currently in use on the PCI bus", newUnit)
 	}
 

vsphere/resource_vsphere_virtual_machine_test.go

@@ -280,6 +280,26 @@ func TestAccResourceVSphereVirtualMachine(t *testing.T) {
 				},
 			},
 		},
+		{
+			"maximum number of nics",
+			resource.TestCase{
+				PreCheck: func() {
+					testAccPreCheck(tp)
+					testAccResourceVSphereVirtualMachinePreCheck(tp)
+				},
+				Providers:    testAccProviders,
+				CheckDestroy: testAccResourceVSphereVirtualMachineCheckExists(false),
+				Steps: []resource.TestStep{
+					{
+						Config: testAccResourceVSphereVirtualMachineConfigMaxNIC(),
+						Check: resource.ComposeTestCheckFunc(
+							testAccResourceVSphereVirtualMachineCheckExists(true),
+							testAccResourceVSphereVirtualMachineCheckNICCount(10),
+						),
+					},
+				},
+			},
+		},
 		{
 			"upgrade cpu and ram",
 			resource.TestCase{
@@ -1808,6 +1828,28 @@ func testAccResourceVSphereVirtualMachineCheckVmdkDatastore(name, expected strin
 	}
 }
 
+// testAccResourceVSphereVirtualMachineCheckNICCount checks the number of NICs
+// on the virtual machine.
+func testAccResourceVSphereVirtualMachineCheckNICCount(expected int) resource.TestCheckFunc {
+	return func(s *terraform.State) error {
+		props, err := testGetVirtualMachineProperties(s, "vm")
+		if err != nil {
+			return err
+		}
+
+		var actual int
+		for _, dev := range props.Config.Hardware.Device {
+			if _, ok := dev.(types.BaseVirtualEthernetCard); ok {
+				actual++
+			}
+		}
+		if expected != actual {
+			return fmt.Errorf("expected %d number of NICs, got %d", expected, actual)
+		}
+		return nil
+	}
+}
+
 func testAccResourceVSphereVirtualMachineConfigBasic() string {
 	return fmt.Sprintf(`
 variable "datacenter" {
@@ -2391,6 +2433,105 @@ resource "vsphere_virtual_machine" "vm" {
 	)
 }
 
+func testAccResourceVSphereVirtualMachineConfigMaxNIC() string {
+	return fmt.Sprintf(`
+variable "datacenter" {
+  default = "%s"
+}
+
+variable "resource_pool" {
+  default = "%s"
+}
+
+variable "network_label" {
+  default = "%s"
+}
+
+variable "datastore" {
+  default = "%s"
+}
+
+data "vsphere_datacenter" "dc" {
+  name = "${var.datacenter}"
+}
+
+data "vsphere_datastore" "datastore" {
+  name          = "${var.datastore}"
+  datacenter_id = "${data.vsphere_datacenter.dc.id}"
+}
+
+data "vsphere_resource_pool" "pool" {
+  name          = "${var.resource_pool}"
+  datacenter_id = "${data.vsphere_datacenter.dc.id}"
+}
+
+data "vsphere_network" "network" {
+  name          = "${var.network_label}"
+  datacenter_id = "${data.vsphere_datacenter.dc.id}"
+}
+
+resource "vsphere_virtual_machine" "vm" {
+  name             = "terraform-test"
+  resource_pool_id = "${data.vsphere_resource_pool.pool.id}"
+  datastore_id     = "${data.vsphere_datastore.datastore.id}"
+
+  num_cpus = 2
+  memory   = 2048
+  guest_id = "other3xLinux64Guest"
+
+  network_interface {
+    network_id = "${data.vsphere_network.network.id}"
+  }
+
+  network_interface {
+    network_id = "${data.vsphere_network.network.id}"
+  }
+
+  network_interface {
+    network_id = "${data.vsphere_network.network.id}"
+  }
+
+  network_interface {
+    network_id = "${data.vsphere_network.network.id}"
+  }
+
+  network_interface {
+    network_id = "${data.vsphere_network.network.id}"
+  }
+
+  network_interface {
+    network_id = "${data.vsphere_network.network.id}"
+  }
+
+  network_interface {
+    network_id = "${data.vsphere_network.network.id}"
+  }
+
+  network_interface {
+    network_id = "${data.vsphere_network.network.id}"
+  }
+
+  network_interface {
+    network_id = "${data.vsphere_network.network.id}"
+  }
+
+  network_interface {
+    network_id = "${data.vsphere_network.network.id}"
+  }
+
+  disk {
+    name = "terraform-test.vmdk"
+    size = 20
+  }
+}
+`,
+		os.Getenv("VSPHERE_DATACENTER"),
+		os.Getenv("VSPHERE_RESOURCE_POOL"),
+		os.Getenv("VSPHERE_NETWORK_LABEL_PXE"),
+		os.Getenv("VSPHERE_DATASTORE"),
+	)
+}
+
 func testAccResourceVSphereVirtualMachineConfigBasicAnnotation() string {
 	return fmt.Sprintf(`
 variable "datacenter" {
@@ -3295,6 +3436,7 @@ resource "vsphere_virtual_machine" "vm" {
 		os.Getenv("VSPHERE_USE_LINKED_CLONE"),
 	)
 }
+
 func testAccResourceVSphereVirtualMachineConfigCloneTimeZone(zone string) string {
 	return fmt.Sprintf(`
 variable "datacenter" {