manual lookup

index.ts

@@ -3,6 +3,8 @@ import { Server, createConnection } from 'net';
 import { hashAddress } from './src/hash-address';
 import { createLogger } from 'bunyan';
 import { Socket } from 'net';
+import Address from 'ipaddr.js';
+import dns from 'dns';
 
 declare module 'net' {
   interface Server {
@@ -24,20 +26,34 @@ const log = createLogger({ name: 'switcher' });
 const server: Server = createProxyServer({
   auth: true,
   createProxyConnection: async (info) => {
-    let socket: Socket;
+    const src: Address.IPv4 | Address.IPv6 = info.socket[targetIpSym];
     log.info(
-      `Connecting to ${info.dstHost}:${info.dstPort} with ${info.socket[targetIpSym]}`,
+      `Connecting to ${info.dstHost}:${info.dstPort} with ${src?.toString()}`,
     );
-    try {
-      socket = createConnection({
-        host: info.dstHost,
-        port: info.dstPort,
-        localAddress: info.socket[targetIpSym] || undefined,
-      });
-    } catch (e) {
-      log.warn(
-        `Failed to connect to ${info.dstHost}:${info.dstPort}, retrying direct connection: ${e}`,
-      );
+    let socket: Socket;
+    if (src) {
+      try {
+        const lookup = await dns.promises.lookup(
+          info.dstHost,
+          src.kind() === 'ipv4' ? 4 : 6,
+        );
+        socket = createConnection({
+          host: lookup.address,
+          port: info.dstPort,
+          localAddress: src.toString(),
+        });
+      } catch (e) {
+        log.warn(
+          `Remote ${
+            info.dstHost
+          } does not support ${src.kind()}, fallback to direct connect.`,
+        );
+        socket = createConnection({
+          host: info.dstHost,
+          port: info.dstPort,
+        });
+      }
+    } else {
       socket = createConnection({
         host: info.dstHost,
         port: info.dstPort,
@@ -56,8 +72,9 @@ server.on('proxy-auth', (socket, username, password, callback) => {
     return;
   }
   const token = `${username}:${password}`;
-  socket[targetIpSym] = hashAddress(process.env.CIDR, token).toString();
-  log.info(`Mapped ${token} to ${socket[targetIpSym]}`);
+  const address = hashAddress(process.env.CIDR, token);
+  socket[targetIpSym] = address;
+  log.info(`Mapped ${token} to ${address.toString()}`);
   callback(true);
 });