From 86c81ff0d59e79d2d33f176f69a7c2d1dcd91e02 Mon Sep 17 00:00:00 2001
From: MrBBot <bcoll@cloudflare.com>
Date: Tue, 5 Dec 2023 08:17:28 +0000
Subject: [PATCH] fix: listen on IPv4 loopback only by default on Windows
 (#4547)

---
 .changeset/quick-pens-develop.md                      | 7 +++++++
 packages/wrangler/src/__tests__/configuration.test.ts | 2 +-
 packages/wrangler/src/__tests__/dev.test.tsx          | 4 ++--
 packages/wrangler/src/config/validation.ts            | 9 ++++++++-
 packages/wrangler/src/pages/dev.ts                    | 9 ++++++++-
 5 files changed, 26 insertions(+), 5 deletions(-)
 create mode 100644 .changeset/quick-pens-develop.md

diff --git a/.changeset/quick-pens-develop.md b/.changeset/quick-pens-develop.md
new file mode 100644
index 000000000000..8c762c019888
--- /dev/null
+++ b/.changeset/quick-pens-develop.md
@@ -0,0 +1,7 @@
+---
+"wrangler": minor
+---
+
+fix: listen on IPv4 loopback only by default on Windows
+
+Due to a [known issue](https://github.com/cloudflare/workerd/issues/1408), `workerd` will only listen on the IPv4 loopback address `127.0.0.1` when it's asked to listen on `localhost`. On Node.js > 17, `localhost` will resolve to the IPv6 loopback address, meaning requests to `workerd` would fail. This change switches to using the IPv4 loopback address throughout Wrangler on Windows, while [workerd#1408](https://github.com/cloudflare/workerd/issues/1408) gets fixed.
diff --git a/packages/wrangler/src/__tests__/configuration.test.ts b/packages/wrangler/src/__tests__/configuration.test.ts
index 01d4f23b53fd..acccd1a54a3a 100644
--- a/packages/wrangler/src/__tests__/configuration.test.ts
+++ b/packages/wrangler/src/__tests__/configuration.test.ts
@@ -30,7 +30,7 @@ describe("normalizeAndValidateConfig()", () => {
 			constellation: [],
 			hyperdrive: [],
 			dev: {
-				ip: "localhost",
+				ip: process.platform === "win32" ? "127.0.0.1" : "localhost",
 				local_protocol: "http",
 				port: undefined, // the default of 8787 is set at runtime
 				upstream_protocol: "https",
diff --git a/packages/wrangler/src/__tests__/dev.test.tsx b/packages/wrangler/src/__tests__/dev.test.tsx
index b5a4b9c2b7a2..0ddf62596e96 100644
--- a/packages/wrangler/src/__tests__/dev.test.tsx
+++ b/packages/wrangler/src/__tests__/dev.test.tsx
@@ -840,7 +840,7 @@ describe("wrangler dev", () => {
 			fs.writeFileSync("index.js", `export default {};`);
 			await runWrangler("dev");
 			expect((Dev as jest.Mock).mock.calls[0][0].initialIp).toEqual(
-				"localhost"
+				process.platform === "win32" ? "127.0.0.1" : "localhost"
 			);
 			expect(std.out).toMatchInlineSnapshot(`""`);
 			expect(std.warn).toMatchInlineSnapshot(`""`);
@@ -1060,7 +1060,7 @@ describe("wrangler dev", () => {
 			fs.writeFileSync("index.js", `export default {};`);
 			await runWrangler("dev");
 			expect((Dev as jest.Mock).mock.calls[0][0].initialIp).toEqual(
-				"localhost"
+				process.platform === "win32" ? "127.0.0.1" : "localhost"
 			);
 			expect(std.out).toMatchInlineSnapshot(`
 			        "Your worker has access to the following bindings:
diff --git a/packages/wrangler/src/config/validation.ts b/packages/wrangler/src/config/validation.ts
index bcf7631bcabc..588fd424527a 100644
--- a/packages/wrangler/src/config/validation.ts
+++ b/packages/wrangler/src/config/validation.ts
@@ -390,7 +390,14 @@ function normalizeAndValidateDev(
 	rawDev: RawDevConfig
 ): DevConfig {
 	const {
-		ip = "localhost",
+		// On Windows, when specifying `localhost` as the socket hostname, `workerd`
+		// will only listen on the IPv4 loopback `127.0.0.1`, not the IPv6 `::1`:
+		// https://github.com/cloudflare/workerd/issues/1408
+		// On Node 17+, `fetch()` will only try to fetch the IPv6 address.
+		// For now, on Windows, we default to listening on IPv4 only and using
+		// `127.0.0.1` when sending control requests to `workerd` (e.g. with the
+		// `ProxyController`).
+		ip = process.platform === "win32" ? "127.0.0.1" : "localhost",
 		port,
 		inspector_port,
 		local_protocol = "http",
diff --git a/packages/wrangler/src/pages/dev.ts b/packages/wrangler/src/pages/dev.ts
index 9edcf8da1009..2ab0182d2edb 100644
--- a/packages/wrangler/src/pages/dev.ts
+++ b/packages/wrangler/src/pages/dev.ts
@@ -99,7 +99,14 @@ export function Options(yargs: CommonYargsArgv) {
 			},
 			ip: {
 				type: "string",
-				default: "localhost",
+				// On Windows, when specifying `localhost` as the socket hostname,
+				// `workerd` will only listen on the IPv4 loopback `127.0.0.1`, not the
+				// IPv6 `::1`: https://github.com/cloudflare/workerd/issues/1408
+				// On Node 17+, `fetch()` will only try to fetch the IPv6 address.
+				// For now, on Windows, we default to listening on IPv4 only and using
+				// `127.0.0.1` when sending control requests to `workerd` (e.g. with the
+				// `ProxyController`).
+				default: process.platform === "win32" ? "127.0.0.1" : "localhost",
 				description: "The IP address to listen on",
 			},
 			port: {