Extended aws_vpn_gateway use case. (terraform-aws-modules#67)

* Extended aws_vpn_gateway use case

* Fixed warning from outputs on vgw_id

Author: robh007

main.tf

@@ -62,8 +62,7 @@ resource "aws_internet_gateway" "this" {
 resource "aws_route_table" "public" {
   count = "${var.create_vpc && length(var.public_subnets) > 0 ? 1 : 0}"
 
-  vpc_id           = "${aws_vpc.this.id}"
-  propagating_vgws = ["${var.public_propagating_vgws}"]
+  vpc_id = "${aws_vpc.this.id}"
 
   tags = "${merge(var.tags, var.public_route_table_tags, map("Name", format("%s-public", var.name)))}"
 }
@@ -83,8 +82,7 @@ resource "aws_route" "public_internet_gateway" {
 resource "aws_route_table" "private" {
   count = "${var.create_vpc && local.max_subnet_length > 0 ? local.max_subnet_length : 0}"
 
-  vpc_id           = "${aws_vpc.this.id}"
-  propagating_vgws = ["${var.private_propagating_vgws}"]
+  vpc_id = "${aws_vpc.this.id}"
 
   tags = "${merge(var.tags, var.private_route_table_tags, map("Name", format("%s-private-%s", var.name, element(var.azs, count.index))))}"
 
@@ -340,6 +338,27 @@ resource "aws_vpn_gateway" "this" {
   tags = "${merge(var.tags, map("Name", format("%s", var.name)))}"
 }
 
+resource "aws_vpn_gateway_attachment" "this" {
+  count = "${var.vpn_gateway_id != "" ? 1 : 0}"
+
+  vpc_id         = "${aws_vpc.this.id}"
+  vpn_gateway_id = "${var.vpn_gateway_id}"
+}
+
+resource "aws_vpn_gateway_route_propagation" "public" {
+  count = "${var.create_vpc && var.propagate_public_route_tables_vgw && (var.enable_vpn_gateway  || var.vpn_gateway_id != "") ? 1 : 0}"
+
+  route_table_id = "${element(aws_route_table.public.*.id, count.index)}"
+  vpn_gateway_id = "${element(concat(aws_vpn_gateway.this.*.id, aws_vpn_gateway_attachment.this.*.vpn_gateway_id), count.index)}"
+}
+
+resource "aws_vpn_gateway_route_propagation" "private" {
+  count = "${var.create_vpc && var.propagate_private_route_tables_vgw && (var.enable_vpn_gateway || var.vpn_gateway_id != "") ? length(var.private_subnets) : 0}"
+
+  route_table_id = "${element(aws_route_table.private.*.id, count.index)}"
+  vpn_gateway_id = "${element(concat(aws_vpn_gateway.this.*.id, aws_vpn_gateway_attachment.this.*.vpn_gateway_id), count.index)}"
+}
+
 ###########
 # Defaults
 ###########

outputs.tf

@@ -181,7 +181,7 @@ output "vpc_endpoint_dynamodb_id" {
 # VPN Gateway
 output "vgw_id" {
   description = "The ID of the VPN Gateway"
-  value       = "${element(concat(aws_vpn_gateway.this.*.id, list("")), 0)}"
+  value       = "${element(concat(aws_vpn_gateway.this.*.id, aws_vpn_gateway_attachment.this.*.vpn_gateway_id, list("")), 0)}"
 }
 
 output "vpc_endpoint_dynamodb_pl_id" {

variables.tf

@@ -107,14 +107,19 @@ variable "enable_vpn_gateway" {
   default     = false
 }
 
-variable "private_propagating_vgws" {
-  description = "A list of VGWs the private route table should propagate"
-  default     = []
+variable "vpn_gateway_id" {
+  description = "ID of VPN Gateway to attach to the VPC"
+  default     = ""
 }
 
-variable "public_propagating_vgws" {
-  description = "A list of VGWs the public route table should propagate"
-  default     = []
+variable "propagate_private_route_tables_vgw" {
+  description = "Should be true if you want route table propagation"
+  default     = false
+}
+
+variable "propagate_public_route_tables_vgw" {
+  description = "Should be true if you want route table propagation"
+  default     = false
 }
 
 variable "tags" {