Work around Java emulators + WSL connectivity issues.

firebase · yuchenshi · Nov 5, 2020 · Nov 4, 2020 · Nov 4, 2020 · 7b33dc82b0b1fe12d9bb492c6cef469d366941cb
commit 7b33dc82b0b1fe12d9bb492c6cef469d366941cb
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -0,0 +1 @@
+- Work around Java emulators + WSL connectivity issues.
diff --git a/src/emulator/controller.ts b/src/emulator/controller.ts
@@ -41,10 +41,20 @@ import { FLAG_EXPORT_ON_EXIT_NAME } from "./commandUtils";
 import { fileExistsSync } from "../fsutils";
 
 async function getAndCheckAddress(emulator: Emulators, options: any): Promise<Address> {
- const host = Constants.normalizeHost(
+ let host = Constants.normalizeHost(
  options.config.get(Constants.getHostKey(emulator), Constants.getDefaultHost(emulator))
  );
 
+ if (host === "localhost" && utils.isRunningInWSL()) {
+ // HACK(https://github.com/firebase/firebase-tools-ui/issues/332): Use IPv4
+ // 127.0.0.1 instead of localhost. This, combined with the hack in
+ // downloadableEmulators.ts, forces the emulator to listen on IPv4 ONLY.
+ // The CLI (including the hub) will also consistently report 127.0.0.1,
+ // causing clients to connect via IPv4 only (which mitigates the problem of
+ // some clients resolving localhost to IPv6 and get connection refused).
+ host = "127.0.0.1";
+ }
+
  const portVal = options.config.get(Constants.getPortKey(emulator), undefined);
  let port;
  let findAvailablePort = false;

diff --git a/src/emulator/downloadableEmulators.ts b/src/emulator/downloadableEmulators.ts
@@ -168,6 +168,20 @@ function _getCommand(
 
  const cmdLineArgs = baseCmd.args.slice();
 
+ if (
+ baseCmd.binary === "java" &&
+ utils.isRunningInWSL() &&
+ (!args.host || !args.host.includes(":"))
+ ) {
+ // HACK(https://github.com/firebase/firebase-tools-ui/issues/332): Force
+ // Java to use IPv4 sockets in WSL (unless IPv6 address explicitly used).
+ // Otherwise, Java will open a tcp6 socket (even if IPv4 address is used),
+ // which handles both 4/6 on Linux but NOT IPv4 from the host to WSL.
+ // This is a hack because it breaks all IPv6 connections as a side effect.
+ // See: https://docs.oracle.com/javase/8/docs/api/java/net/doc-files/net-properties.html
+ cmdLineArgs.unshift("-Djava.net.preferIPv4Stack=true"); // first argument
+ }
+
  const logger = EmulatorLogger.forEmulator(emulator);
  Object.keys(args).forEach((key) => {
  if (!baseCmd.optionalArgs.includes(key)) {

diff --git a/src/utils.ts b/src/utils.ts
@@ -478,3 +478,11 @@ export function datetimeString(d: Date): string {
 export function isCloudEnvironment() {
  return !!process.env.CODESPACES;
 }
+
+/**
+ * Indicates whether or not this process is likely to be running in WSL.
+ * @return true if we're likely in WSL, false otherwise
+ */
+export function isRunningInWSL(): boolean {
+ return !!process.env.WSL_DISTRO_NAME;
+}