doc,test: mention Duplex support for TLS

Document and test the existing support for generic Duplex streams
in the TLS module.

PR-URL: nodejs#17599
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

doc/api/tls.md

@@ -455,7 +455,10 @@ changes:
     description: ALPN options are supported now.
 -->
 
-* `socket` {net.Socket} An instance of [`net.Socket`][]
+* `socket` {net.Socket|stream.Duplex}
+  On the server side, any `Duplex` stream. On the client side, any
+  instance of [`net.Socket`][] (for generic `Duplex` stream support
+  on the client side, [`tls.connect()`][] must be used).
 * `options` {Object}
   * `isServer`: The SSL/TLS protocol is asymmetrical, TLSSockets must know if
     they are to behave as a server or a client. If `true` the TLS socket will be
@@ -815,10 +818,12 @@ changes:
   * `port` {number} Port the client should connect to.
   * `path` {string} Creates unix socket connection to path. If this option is
     specified, `host` and `port` are ignored.
-  * `socket` {net.Socket} Establish secure connection on a given socket rather
-    than creating a new socket. If this option is specified, `path`, `host` and
-    `port` are ignored.  Usually, a socket is already connected when passed to
-    `tls.connect()`, but it can be connected later. Note that
+  * `socket` {stream.Duplex} Establish secure connection on a given socket
+    rather than creating a new socket. Typically, this is an instance of
+    [`net.Socket`][], but any `Duplex` stream is allowed.
+    If this option is specified, `path`, `host` and `port` are ignored,
+    except for certificate validation.  Usually, a socket is already connected
+    when passed to `tls.connect()`, but it can be connected later. Note that
     connection/disconnection/destruction of `socket` is the user's
     responsibility, calling `tls.connect()` will not cause `net.connect()` to be
     called.

test/parallel/test-tls-generic-stream.js

@@ -0,0 +1,38 @@
+'use strict';
+const common = require('../common');
+if (!common.hasCrypto)
+  common.skip('missing crypto');
+
+const fixtures = require('../common/fixtures');
+const makeDuplexPair = require('../common/duplexpair');
+const assert = require('assert');
+const { TLSSocket, connect } = require('tls');
+
+const key = fixtures.readKey('agent1-key.pem');
+const cert = fixtures.readKey('agent1-cert.pem');
+const ca = fixtures.readKey('ca1-cert.pem');
+
+const { clientSide, serverSide } = makeDuplexPair();
+
+const clientTLS = connect({
+  socket: clientSide,
+  ca,
+  host: 'agent1'  // Hostname from certificate
+});
+const serverTLS = new TLSSocket(serverSide, {
+  isServer: true,
+  key,
+  cert,
+  ca
+});
+
+assert.strictEqual(clientTLS.connecting, false);
+assert.strictEqual(serverTLS.connecting, false);
+
+clientTLS.on('secureConnect', common.mustCall(() => {
+  clientTLS.write('foobar', common.mustCall(() => {
+    assert.strictEqual(serverTLS.read().toString(), 'foobar');
+    assert.strictEqual(clientTLS._handle.writeQueueSize, 0);
+  }));
+  assert.ok(clientTLS._handle.writeQueueSize > 0);
+}));

tools/doc/type-parser.js

@@ -49,6 +49,7 @@ const typeMap = {
   'Stream': 'stream.html#stream_stream',
   'stream.Readable': 'stream.html#stream_class_stream_readable',
   'stream.Writable': 'stream.html#stream_class_stream_writable',
+  'stream.Duplex': 'stream.html#stream_class_stream_duplex',
 
   'tls.TLSSocket': 'tls.html#tls_class_tls_tlssocket',