add support for private ipv4 addresses in subnet mapping of ELB V2

aws/resource_aws_lb.go

@@ -109,6 +109,11 @@ func resourceAwsLb() *schema.Resource {
 							Optional: true,
 							ForceNew: true,
 						},
+						"private_ipv4_address": {
+							Type:     schema.TypeString,
+							Optional: true,
+							ForceNew: true,
+						},
 					},
 				},
 				Set: func(v interface{}) int {
@@ -118,6 +123,9 @@ func resourceAwsLb() *schema.Resource {
 					if m["allocation_id"] != "" {
 						buf.WriteString(fmt.Sprintf("%s-", m["allocation_id"].(string)))
 					}
+					if m["private_ipv4_address"] != "" {
+						buf.WriteString(fmt.Sprintf("%s-", m["private_ipv4_address"].(string)))
+					}
 					return hashcode.String(buf.String())
 				},
 			},
@@ -255,6 +263,10 @@ func resourceAwsLbCreate(d *schema.ResourceData, meta interface{}) error {
 			if subnetMap["allocation_id"].(string) != "" {
 				elbOpts.SubnetMappings[i].AllocationId = aws.String(subnetMap["allocation_id"].(string))
 			}
+
+			if subnetMap["private_ipv4_address"].(string) != "" {
+				elbOpts.SubnetMappings[i].PrivateIPv4Address = aws.String(subnetMap["private_ipv4_address"].(string))
+			}
 		}
 	}
 
@@ -658,6 +670,7 @@ func flattenSubnetMappingsFromAvailabilityZones(availabilityZones []*elbv2.Avail
 
 		for _, loadBalancerAddress := range availabilityZone.LoadBalancerAddresses {
 			m["allocation_id"] = aws.StringValue(loadBalancerAddress.AllocationId)
+			m["private_ipv4_address"] = aws.StringValue(loadBalancerAddress.PrivateIPv4Address)
 		}
 
 		l = append(l, m)

website/docs/r/lb.html.markdown

@@ -74,6 +74,25 @@ resource "aws_lb" "example" {
 }
 ```
 
+### Specifying private IP addresses for an internal-facing load balancer
+
+```hcl
+resource "aws_lb" "example" {
+  name               = "example"
+  load_balancer_type = "network"
+
+  subnet_mapping {
+    subnet_id     = "${aws_subnet.example1.id}"
+    private_ivp4_address = "10.0.1.15"
+  }
+
+  subnet_mapping {
+    subnet_id     = "${aws_subnet.example2.id}"
+    private_ivp4_address = "10.0.2.15"
+  }
+}
+```
+
 ## Argument Reference
 
 ~> **NOTE:** Please note that internal LBs can only use `ipv4` as the ip_address_type. You can only change to `dualstack` ip_address_type if the selected subnets are IPv6 enabled.
@@ -113,6 +132,7 @@ Subnet Mapping (`subnet_mapping`) blocks support the following:
 
 * `subnet_id` - (Required) The id of the subnet of which to attach to the load balancer. You can specify only one subnet per Availability Zone.
 * `allocation_id` - (Optional) The allocation ID of the Elastic IP address.
+* `private_ipv4_address` - (Optional) A private ipv4 address within the subnet to assign to the internal-facing load balancer.
 
 ## Attributes Reference