Add Terraform support for L3_DEFAULT (all protocol) L4 ILB

.changelog/8445.txt

@@ -0,0 +1,4 @@
+```release-note: enhancement
+compute: added protocol type: UNSPECIFIED in `google_compute_backend_service` as per [release note](https://cloud.google.com/load-balancing/docs/release-notes#July_24_2023)
+
+```

google/resource_compute_backend_service_test.go

@@ -983,6 +983,63 @@ resource "google_compute_http_health_check" "default" {
 `, serviceName, timeout, igName, itName, checkName)
 }
 
+func testAccComputeBackendService_withUnspecifiedProtocol(
+	serviceName, igName, itName, checkName string, timeout int64) string {
+	return fmt.Sprintf(`
+data "google_compute_image" "my_image" {
+  family  = "debian-11"
+  project = "debian-cloud"
+}
+
+resource "google_compute_backend_service" "lipsum" {
+  name        = "%s"
+  description = "Hello World 1234"
+  port_name   = "http"
+  protocol    = "UNSPECIFIED"
+  timeout_sec = %v
+
+  backend {
+    group = google_compute_instance_group_manager.foobar.instance_group
+  }
+
+  health_checks = [google_compute_http_health_check.default.self_link]
+}
+
+resource "google_compute_instance_group_manager" "foobar" {
+  name = "%s"
+  version {
+    instance_template = google_compute_instance_template.foobar.self_link
+    name              = "primary"
+  }
+  base_instance_name = "tf-test-foobar"
+  zone               = "us-central1-f"
+  target_size        = 1
+}
+
+resource "google_compute_instance_template" "foobar" {
+  name         = "%s"
+  machine_type = "e2-medium"
+
+  network_interface {
+    network = "default"
+  }
+
+  disk {
+    source_image = data.google_compute_image.my_image.self_link
+    auto_delete  = true
+    boot         = true
+  }
+}
+
+resource "google_compute_http_health_check" "default" {
+  name               = "%s"
+  request_path       = "/"
+  check_interval_sec = 1
+  timeout_sec        = 1
+}
+`, serviceName, timeout, igName, itName, checkName)
+}
+
 func testAccComputeBackendService_withBackendAndMaxUtilization(
 	serviceName, igName, itName, checkName string, timeout int64) string {
 	return fmt.Sprintf(`

google/services/compute/resource_compute_backend_service.go

@@ -1012,10 +1012,12 @@ scheme is EXTERNAL.`,
 				Type:         schema.TypeString,
 				Computed:     true,
 				Optional:     true,
-				ValidateFunc: verify.ValidateEnum([]string{"HTTP", "HTTPS", "HTTP2", "TCP", "SSL", "GRPC", ""}),
+				ValidateFunc: verify.ValidateEnum([]string{"HTTP", "HTTPS", "HTTP2", "TCP", "SSL", "GRPC", "UNSPECIFIED", ""}),
 				Description: `The protocol this BackendService uses to communicate with backends.
 The default is HTTP. **NOTE**: HTTP2 is only valid for beta HTTP/2 load balancer
-types and may result in errors if used with the GA API. Possible values: ["HTTP", "HTTPS", "HTTP2", "TCP", "SSL", "GRPC"]`,
+types and may result in errors if used with the GA API. **NOTE**: With protocol “UNSPECIFIED”,
+the backend service can be used by Layer 4 Internal Load Balancing or Network Load Balancing
+with TCP/UDP/L3_DEFAULT Forwarding Rule protocol. Possible values: ["HTTP", "HTTPS", "HTTP2", "TCP", "SSL", "GRPC", "UNSPECIFIED"]`,
 			},
 			"security_policy": {
 				Type:             schema.TypeString,

website/docs/r/compute_backend_service.html.markdown

@@ -515,8 +515,10 @@ The following arguments are supported:
   (Optional)
   The protocol this BackendService uses to communicate with backends.
   The default is HTTP. **NOTE**: HTTP2 is only valid for beta HTTP/2 load balancer
-  types and may result in errors if used with the GA API.
-  Possible values are: `HTTP`, `HTTPS`, `HTTP2`, `TCP`, `SSL`, `GRPC`.
+  types and may result in errors if used with the GA API. **NOTE**: With protocol “UNSPECIFIED”,
+  the backend service can be used by Layer 4 Internal Load Balancing or Network Load Balancing
+  with TCP/UDP/L3_DEFAULT Forwarding Rule protocol.
+  Possible values are: `HTTP`, `HTTPS`, `HTTP2`, `TCP`, `SSL`, `GRPC`, `UNSPECIFIED`.
 
 * `security_policy` -
   (Optional)