feat: pasv_url option to send to client

This has passive connections to listen on the same hostname as the server.
But allows this to be customized via the `pasv_url` option.

Hostnames are no longer resolved if given `0.0.0.0`, except when being given to the client via `PASV`

README.md

@@ -69,11 +69,16 @@ Supported protocols:
 - `ftp` Plain FTP
 - `ftps` Implicit FTP over TLS
 
-_Note:_ The hostname must be the external IP address to accept external connections. Setting the hostname to `0.0.0.0` will automatically set the external IP.
+_Note:_ The hostname must be the external IP address to accept external connections. `0.0.0.0` will listen on any available hosts for server and passive connections.
 __Default:__ `"ftp://127.0.0.1:21"`
 
 #### options
 
+##### `pasv_url`
+The hostname to provide a client when attempting a passive connection (`PASV`). This defaults to the provided `url`.
+_Note:_ If set to `0.0.0.0`, this will automatically resolve to the external IP of the box.
+__Default:__ `"127.0.0.1"`
+
 ##### `pasv_range`
 A starting port (eg `8000`) or a range (eg `"8000-9000"`) to accept passive connections.
 This range is then queried for an available port to use when required.

src/commands/registration/pasv.js

@@ -6,7 +6,7 @@ module.exports = {
     this.connector = new PassiveConnector(this);
     return this.connector.setupServer()
     .then(server => {
-      const address = this.server.url.hostname;
+      const address = this.server.options.pasv_url;
       const {port} = server.address();
       const host = address.replace(/\./g, ',');
       const portByte1 = port / 256 | 0;

src/index.js

@@ -17,6 +17,7 @@ class FtpServer extends EventEmitter {
       log: buyan.createLogger({name: 'ftp-srv'}),
       anonymous: false,
       pasv_range: 22,
+      pasv_url: null,
       file_format: 'ls',
       blacklist: [],
       whitelist: [],
@@ -62,9 +63,10 @@ class FtpServer extends EventEmitter {
   }
 
   listen() {
-    return resolveHost(this.url.hostname)
-    .then(hostname => {
-      this.url.hostname = hostname;
+    return resolveHost(this.options.pasv_url || this.url.hostname)
+    .then(pasvUrl => {
+      this.options.pasv_url = pasvUrl;
+
       return new Promise((resolve, reject) => {
         this.server.once('error', reject);
         this.server.listen(this.url.port, this.url.hostname, err => {

test/connector/passive.spec.js

@@ -16,7 +16,7 @@ describe('Connector - Passive //', function () {
     encoding: 'utf8',
     log: bunyan.createLogger({name: 'passive-test'}),
     commandSocket: {},
-    server: {options: {}}
+    server: {options: {}, url: {}}
   };
   let sandbox;