http2: add server handshake utility

doc/api/http2.md

@@ -2875,6 +2875,19 @@ added: v8.4.0
 Returns a [HTTP/2 Settings Object][] containing the deserialized settings from
 the given `Buffer` as generated by `http2.getPackedSettings()`.
 
+### `http2.performServerHandshake(socket[, options])`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+* `socket` {stream.Duplex}
+* `options` {Object}
+  * ...: Any [`http2.createServer()`][] option can be provided.
+* Returns: {ServerHttp2Session}
+
+Create an HTTP/2 server session from an existing socket.
+
 ### `http2.sensitiveHeaders`
 
 <!-- YAML

lib/http2.js

@@ -8,6 +8,7 @@ const {
   getDefaultSettings,
   getPackedSettings,
   getUnpackedSettings,
+  performServerHandshake,
   sensitiveHeaders,
   Http2ServerRequest,
   Http2ServerResponse,
@@ -21,6 +22,7 @@ module.exports = {
   getDefaultSettings,
   getPackedSettings,
   getUnpackedSettings,
+  performServerHandshake,
   sensitiveHeaders,
   Http2ServerRequest,
   Http2ServerResponse,

lib/internal/http2/core.js

@@ -1208,12 +1208,6 @@ class Http2Session extends EventEmitter {
   constructor(type, options, socket) {
     super();
 
-    if (!socket._handle || !socket._handle.isStreamBase) {
-      socket = new JSStreamSocket(socket);
-    }
-    socket.on('error', socketOnError);
-    socket.on('close', socketOnClose);
-
     // No validation is performed on the input parameters because this
     // constructor is not exported directly for users.
 
@@ -1225,6 +1219,12 @@ class Http2Session extends EventEmitter {
 
     socket[kSession] = this;
 
+    if (!socket._handle || !socket._handle.isStreamBase) {
+      socket = new JSStreamSocket(socket);
+    }
+    socket.on('error', socketOnError);
+    socket.on('close', socketOnClose);
+
     this[kState] = {
       destroyCode: NGHTTP2_NO_ERROR,
       flags: SESSION_FLAGS_PENDING,
@@ -1624,7 +1624,7 @@ class ServerHttp2Session extends Http2Session {
     // not be an issue in practice. Additionally, the 'priority' event on
     // server instances (or any other object) is fully undocumented.
     this[kNativeFields][kSessionPriorityListenerCount] =
-      server.listenerCount('priority');
+      server ? server.listenerCount('priority') : 0;
   }
 
   get server() {
@@ -3397,6 +3397,11 @@ function getUnpackedSettings(buf, options = kEmptyObject) {
   return settings;
 }
 
+function performServerHandshake(socket, options = {}) {
+  options = initializeOptions(options);
+  return new ServerHttp2Session(options, socket, undefined);
+}
+
 binding.setCallbackFunctions(
   onSessionInternalError,
   onPriority,
@@ -3420,6 +3425,7 @@ module.exports = {
   getDefaultSettings,
   getPackedSettings,
   getUnpackedSettings,
+  performServerHandshake,
   sensitiveHeaders: kSensitiveHeaders,
   Http2Session,
   Http2Stream,

lib/internal/js_stream_socket.js

@@ -17,6 +17,7 @@ let debug = require('internal/util/debuglog').debuglog(
 );
 const { owner_symbol } = require('internal/async_hooks').symbols;
 const { ERR_STREAM_WRAP } = require('internal/errors').codes;
+const { kSession } = require('internal/stream_base_commons');
 
 const kCurrentWriteRequest = Symbol('kCurrentWriteRequest');
 const kCurrentShutdownRequest = Symbol('kCurrentShutdownRequest');
@@ -263,6 +264,14 @@ class JSStreamSocket extends Socket {
       cb();
     });
   }
+
+  get [kSession]() {
+    return this.stream[kSession];
+  }
+
+  set [kSession](session) {
+    this.stream[kSession] = session;
+  }
 }
 
 module.exports = JSStreamSocket;

test/parallel/test-http2-perform-server-handshake.js

@@ -0,0 +1,48 @@
+'use strict';
+
+const common = require('../common');
+
+if (!common.hasCrypto)
+  common.skip('missing crypto');
+
+const assert = require('assert');
+const http2 = require('http2');
+const stream = require('stream');
+const makeDuplexPair = require('../common/duplexpair');
+
+// Basic test
+{
+  const { clientSide, serverSide } = makeDuplexPair();
+
+  const client = http2.connect('http://example.com', {
+    createConnection: () => clientSide,
+  });
+
+  const session = http2.performServerHandshake(serverSide);
+
+  session.on('stream', common.mustCall((stream, headers) => {
+    assert.strictEqual(headers[':path'], '/test');
+    stream.respond({
+      ':status': 200,
+    });
+    stream.end('hi!');
+  }));
+
+  const req = client.request({ ':path': '/test' });
+  req.on('response', common.mustCall());
+  req.end();
+}
+
+// Double bind should fail
+{
+  const socket = new stream.Duplex({
+    read() {},
+    write() {},
+  });
+
+  http2.performServerHandshake(socket);
+
+  assert.throws(() => {
+    http2.performServerHandshake(socket);
+  }, { code: 'ERR_HTTP2_SOCKET_BOUND' });
+}