Add preserve_host_header argument to aws_lb

.changelog/26056.txt

@@ -0,0 +1,7 @@
+```release-note:enhancement
+resource/aws_lb: Add `preserve_host_header` argument
+```
+
+```release-note:enhancement
+data-source/aws_lb: Add `preserve_host_header` attribute
+```

internal/service/elbv2/load_balancer.go

@@ -206,6 +206,13 @@ func ResourceLoadBalancer() *schema.Resource {
 				DiffSuppressFunc: suppressIfLBType("network"),
 			},
 
+			"preserve_host_header": {
+				Type:             schema.TypeBool,
+				Optional:         true,
+				Default:          false,
+				DiffSuppressFunc: suppressIfLBTypeNot(elbv2.LoadBalancerTypeEnumApplication),
+			},
+
 			"enable_cross_zone_load_balancing": {
 				Type:             schema.TypeBool,
 				Optional:         true,
@@ -502,6 +509,13 @@ func resourceLoadBalancerUpdate(d *schema.ResourceData, meta interface{}) error
 			})
 		}
 
+		if d.HasChange("preserve_host_header") || d.IsNewResource() {
+			attributes = append(attributes, &elbv2.LoadBalancerAttribute{
+				Key:   aws.String("routing.http.preserve_host_header.enabled"),
+				Value: aws.String(strconv.FormatBool(d.Get("preserve_host_header").(bool))),
+			})
+		}
+
 		if d.HasChange("desync_mitigation_mode") || d.IsNewResource() {
 			attributes = append(attributes, &elbv2.LoadBalancerAttribute{
 				Key:   aws.String("routing.http.desync_mitigation_mode"),
@@ -885,6 +899,10 @@ func flattenResource(d *schema.ResourceData, meta interface{}, lb *elbv2.LoadBal
 			dropInvalidHeaderFieldsEnabled := aws.StringValue(attr.Value) == "true"
 			log.Printf("[DEBUG] Setting LB Invalid Header Fields Enabled: %t", dropInvalidHeaderFieldsEnabled)
 			d.Set("drop_invalid_header_fields", dropInvalidHeaderFieldsEnabled)
+		case "routing.http.preserve_host_header.enabled":
+			preserveHostHeaderEnabled := aws.StringValue(attr.Value) == "true"
+			log.Printf("[DEBUG] Setting LB Preserve Host Header Enabled: %t", preserveHostHeaderEnabled)
+			d.Set("preserve_host_header", preserveHostHeaderEnabled)
 		case "deletion_protection.enabled":
 			protectionEnabled := aws.StringValue(attr.Value) == "true"
 			log.Printf("[DEBUG] Setting LB Deletion Protection Enabled: %t", protectionEnabled)

internal/service/elbv2/load_balancer_data_source.go

@@ -134,6 +134,11 @@ func DataSourceLoadBalancer() *schema.Resource {
 				Computed: true,
 			},
 
+			"preserve_host_header": {
+				Type:     schema.TypeBool,
+				Computed: true,
+			},
+
 			"vpc_id": {
 				Type:     schema.TypeString,
 				Computed: true,
@@ -282,6 +287,9 @@ func dataSourceLoadBalancerRead(d *schema.ResourceData, meta interface{}) error
 		case "routing.http.drop_invalid_header_fields.enabled":
 			dropInvalidHeaderFieldsEnabled := aws.StringValue(attr.Value) == "true"
 			d.Set("drop_invalid_header_fields", dropInvalidHeaderFieldsEnabled)
+		case "routing.http.preserve_host_header.enabled":
+			preserveHostHeaderEnabled := aws.StringValue(attr.Value) == "true"
+			d.Set("preserve_host_header", preserveHostHeaderEnabled)
 		case "deletion_protection.enabled":
 			protectionEnabled := aws.StringValue(attr.Value) == "true"
 			d.Set("enable_deletion_protection", protectionEnabled)

internal/service/elbv2/load_balancer_data_source_test.go

@@ -145,6 +145,7 @@ func TestAccELBV2LoadBalancerDataSource_backwardsCompatibility(t *testing.T) {
 					resource.TestCheckResourceAttrPair(dataSourceName1, "ip_address_type", resourceName, "ip_address_type"),
 					resource.TestCheckResourceAttrPair(dataSourceName1, "subnet_mapping.#", resourceName, "subnet_mapping.#"),
 					resource.TestCheckResourceAttrPair(dataSourceName1, "drop_invalid_header_fields", resourceName, "drop_invalid_header_fields"),
+					resource.TestCheckResourceAttrPair(dataSourceName1, "preserve_host_header", resourceName, "preserve_host_header"),
 					resource.TestCheckResourceAttrPair(dataSourceName1, "enable_http2", resourceName, "enable_http2"),
 					resource.TestCheckResourceAttrPair(dataSourceName1, "enable_waf_fail_open", resourceName, "enable_waf_fail_open"),
 					resource.TestCheckResourceAttrPair(dataSourceName1, "access_logs.#", resourceName, "access_logs.#"),
@@ -164,6 +165,7 @@ func TestAccELBV2LoadBalancerDataSource_backwardsCompatibility(t *testing.T) {
 					resource.TestCheckResourceAttrPair(dataSourceName2, "ip_address_type", resourceName, "ip_address_type"),
 					resource.TestCheckResourceAttrPair(dataSourceName2, "subnet_mapping.#", resourceName, "subnet_mapping.#"),
 					resource.TestCheckResourceAttrPair(dataSourceName2, "drop_invalid_header_fields", resourceName, "drop_invalid_header_fields"),
+					resource.TestCheckResourceAttrPair(dataSourceName2, "preserve_host_header", resourceName, "preserve_host_header"),
 					resource.TestCheckResourceAttrPair(dataSourceName2, "enable_http2", resourceName, "enable_http2"),
 					resource.TestCheckResourceAttrPair(dataSourceName2, "enable_waf_fail_open", resourceName, "enable_waf_fail_open"),
 					resource.TestCheckResourceAttrPair(dataSourceName2, "access_logs.#", resourceName, "access_logs.#"),
@@ -183,6 +185,7 @@ func TestAccELBV2LoadBalancerDataSource_backwardsCompatibility(t *testing.T) {
 					resource.TestCheckResourceAttrPair(dataSourceName3, "ip_address_type", resourceName, "ip_address_type"),
 					resource.TestCheckResourceAttrPair(dataSourceName3, "subnet_mapping.#", resourceName, "subnet_mapping.#"),
 					resource.TestCheckResourceAttrPair(dataSourceName3, "drop_invalid_header_fields", resourceName, "drop_invalid_header_fields"),
+					resource.TestCheckResourceAttrPair(dataSourceName3, "preserve_host_header", resourceName, "preserve_host_header"),
 					resource.TestCheckResourceAttrPair(dataSourceName3, "enable_http2", resourceName, "enable_http2"),
 					resource.TestCheckResourceAttrPair(dataSourceName3, "enable_waf_fail_open", resourceName, "enable_waf_fail_open"),
 					resource.TestCheckResourceAttrPair(dataSourceName3, "access_logs.#", resourceName, "access_logs.#"),

internal/service/elbv2/load_balancer_test.go

@@ -620,6 +620,50 @@ func TestAccELBV2LoadBalancer_ApplicationLoadBalancer_updateDropInvalidHeaderFie
 	})
 }
 
+func TestAccELBV2LoadBalancer_ApplicationLoadBalancer_updatePreserveHostHeader(t *testing.T) {
+	var pre, mid, post elbv2.LoadBalancer
+	rName := sdkacctest.RandomWithPrefix(acctest.ResourcePrefix)
+
+	if testing.Short() {
+		t.Skip("skipping long-running test in short mode")
+	}
+
+	resource.ParallelTest(t, resource.TestCase{
+		PreCheck:                 func() { acctest.PreCheck(t) },
+		ErrorCheck:               acctest.ErrorCheck(t, elbv2.EndpointsID),
+		ProtoV5ProviderFactories: acctest.ProtoV5ProviderFactories,
+		CheckDestroy:             testAccCheckLoadBalancerDestroy,
+		Steps: []resource.TestStep{
+			{
+				Config: testAccLoadBalancerConfig_enablePreserveHostHeader(rName, false),
+				Check: resource.ComposeAggregateTestCheckFunc(
+					testAccCheckLoadBalancerExists("aws_lb.lb_test", &pre),
+					testAccCheckLoadBalancerAttribute("aws_lb.lb_test", "routing.http.preserve_host_header.enabled", "false"),
+					resource.TestCheckResourceAttr("aws_lb.lb_test", "preserve_host_header", "false"),
+				),
+			},
+			{
+				Config: testAccLoadBalancerConfig_enablePreserveHostHeader(rName, true),
+				Check: resource.ComposeAggregateTestCheckFunc(
+					testAccCheckLoadBalancerExists("aws_lb.lb_test", &mid),
+					testAccCheckLoadBalancerAttribute("aws_lb.lb_test", "routing.http.preserve_host_header.enabled", "true"),
+					resource.TestCheckResourceAttr("aws_lb.lb_test", "preserve_host_header", "true"),
+					testAccChecklbARNs(&pre, &mid),
+				),
+			},
+			{
+				Config: testAccLoadBalancerConfig_enablePreserveHostHeader(rName, false),
+				Check: resource.ComposeAggregateTestCheckFunc(
+					testAccCheckLoadBalancerExists("aws_lb.lb_test", &post),
+					testAccCheckLoadBalancerAttribute("aws_lb.lb_test", "routing.http.preserve_host_header.enabled", "false"),
+					resource.TestCheckResourceAttr("aws_lb.lb_test", "preserve_host_header", "false"),
+					testAccChecklbARNs(&mid, &post),
+				),
+			},
+		},
+	})
+}
+
 func TestAccELBV2LoadBalancer_ApplicationLoadBalancer_updateDeletionProtection(t *testing.T) {
 	var pre, mid, post elbv2.LoadBalancer
 	rName := sdkacctest.RandomWithPrefix(acctest.ResourcePrefix)
@@ -1903,6 +1947,75 @@ resource "aws_security_group" "alb_test" {
 `, rName, dropInvalid))
 }
 
+func testAccLoadBalancerConfig_enablePreserveHostHeader(rName string, enablePreserveHostHeader bool) string {
+	return acctest.ConfigCompose(acctest.ConfigAvailableAZsNoOptIn(), fmt.Sprintf(`
+resource "aws_lb" "lb_test" {
+  name            = %[1]q
+  internal        = true
+  security_groups = [aws_security_group.alb_test.id]
+  subnets         = aws_subnet.alb_test[*].id
+
+  idle_timeout               = 30
+  enable_deletion_protection = false
+
+  preserve_host_header = %[2]t
+
+  tags = {
+    Name = %[1]q
+  }
+}
+
+variable "subnets" {
+  default = ["10.0.1.0/24", "10.0.2.0/24"]
+  type    = list(string)
+}
+
+resource "aws_vpc" "alb_test" {
+  cidr_block = "10.0.0.0/16"
+
+  tags = {
+    Name = %[1]q
+  }
+}
+
+resource "aws_subnet" "alb_test" {
+  count                   = 2
+  vpc_id                  = aws_vpc.alb_test.id
+  cidr_block              = element(var.subnets, count.index)
+  map_public_ip_on_launch = true
+  availability_zone       = element(data.aws_availability_zones.available.names, count.index)
+
+  tags = {
+    Name = "tf-acc-lb-basic-${count.index}"
+  }
+}
+
+resource "aws_security_group" "alb_test" {
+  name        = "allow_all_alb_test"
+  description = "Used for ALB Testing"
+  vpc_id      = aws_vpc.alb_test.id
+
+  ingress {
+    from_port   = 0
+    to_port     = 0
+    protocol    = "-1"
+    cidr_blocks = ["0.0.0.0/0"]
+  }
+
+  egress {
+    from_port   = 0
+    to_port     = 0
+    protocol    = "-1"
+    cidr_blocks = ["0.0.0.0/0"]
+  }
+
+  tags = {
+    Name = %[1]q
+  }
+}
+`, rName, enablePreserveHostHeader))
+}
+
 func testAccLoadBalancerConfig_enableDeletionProtection(rName string, deletionProtection bool) string {
 	return acctest.ConfigCompose(acctest.ConfigAvailableAZsNoOptIn(), fmt.Sprintf(`
 resource "aws_lb" "lb_test" {

website/docs/r/lb.html.markdown

@@ -109,6 +109,7 @@ Terraform will autogenerate a name beginning with `tf-lb`.
 * `load_balancer_type` - (Optional) The type of load balancer to create. Possible values are `application`, `gateway`, or `network`. The default value is `application`.
 * `security_groups` - (Optional) A list of security group IDs to assign to the LB. Only valid for Load Balancers of type `application`.
 * `drop_invalid_header_fields` - (Optional) Indicates whether HTTP headers with header fields that are not valid are removed by the load balancer (true) or routed to targets (false). The default is false. Elastic Load Balancing requires that message header names contain only alphanumeric characters and hyphens. Only valid for Load Balancers of type `application`.
+* `preserve_host_header` - (Optional) Indicates whether the Application Load Balancer should preserve the Host header in the HTTP request and send it to the target without any change. Defaults to `false`.
 * `access_logs` - (Optional) An Access Logs block. Access Logs documented below.
 * `subnets` - (Optional) A list of subnet IDs to attach to the LB. Subnets
 cannot be updated for Load Balancers of type `network`. Changing this value