http2: add altsvc support

Add support for sending and receiving ALTSVC frames.

PR-URL: #17917
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

doc/api/errors.md

@@ -821,6 +821,16 @@ that.
 
 Occurs with multiple attempts to shutdown an HTTP/2 session.
 
+<a id="ERR_HTTP2_ALTSVC_INVALID_ORIGIN"></a>
+### ERR_HTTP2_ALTSVC_INVALID_ORIGIN
+
+HTTP/2 ALTSVC frames require a valid origin.
+
+<a id="ERR_HTTP2_ALTSVC_LENGTH"></a>
+### ERR_HTTP2_ALTSVC_LENGTH
+
+HTTP/2 ALTSVC frames are limited to a maximum of 16,382 payload bytes.
+
 <a id="ERR_HTTP2_CONNECT_AUTHORITY"></a>
 ### ERR_HTTP2_CONNECT_AUTHORITY
 

doc/api/http2.md

@@ -558,11 +558,103 @@ added: REPLACEME
 Calls [`unref()`][`net.Socket.prototype.unref`] on this `Http2Session`
 instance's underlying [`net.Socket`].
 
+### Class: ServerHttp2Session
+<!-- YAML
+added: v8.4.0
+-->
+
+#### serverhttp2session.altsvc(alt, originOrStream)
+<!-- YAML
+added: REPLACEME
+-->
+
+* `alt` {string} A description of the alternative service configuration as
+  defined by [RFC 7838][].
+* `originOrStream` {number|string|URL|Object} Either a URL string specifying
+  the origin (or an Object with an `origin` property) or the numeric identifier
+  of an active `Http2Stream` as given by the `http2stream.id` property.
+
+Submits an `ALTSVC` frame (as defined by [RFC 7838][]) to the connected client.
+
+```js
+const http2 = require('http2');
+
+const server = http2.createServer();
+server.on('session', (session) => {
+  // Set altsvc for origin https://example.org:80
+  session.altsvc('h2=":8000"', 'https://example.org:80');
+});
+
+server.on('stream', (stream) => {
+  // Set altsvc for a specific stream
+  stream.session.altsvc('h2=":8000"', stream.id);
+});
+```
+
+Sending an `ALTSVC` frame with a specific stream ID indicates that the alternate
+service is associated with the origin of the given `Http2Stream`.
+
+The `alt` and origin string *must* contain only ASCII bytes and are
+strictly interpreted as a sequence of ASCII bytes. The special value `'clear'`
+may be passed to clear any previously set alternative service for a given
+domain.
+
+When a string is passed for the `originOrStream` argument, it will be parsed as
+a URL and the origin will be derived. For insetance, the origin for the
+HTTP URL `'https://example.org/foo/bar'` is the ASCII string
+`'https://example.org'`. An error will be thrown if either the given string
+cannot be parsed as a URL or if a valid origin cannot be derived.
+
+A `URL` object, or any object with an `origin` property, may be passed as
+`originOrStream`, in which case the value of the `origin` property will be
+used. The value of the `origin` property *must* be a properly serialized
+ASCII origin.
+
+#### Specifying alternative services
+
+The format of the `alt` parameter is strictly defined by [RFC 7838][] as an
+ASCII string containing a comma-delimited list of "alternative" protocols
+associated with a specific host and port.
+
+For example, the value `'h2="example.org:81"'` indicates that the HTTP/2
+protocol is available on the host `'example.org'` on TCP/IP port 81. The
+host and port *must* be contained within the quote (`"`) characters.
+
+Multiple alternatives may be specified, for instance: `'h2="example.org:81",
+h2=":82"'`
+
+The protocol identifier (`'h2'` in the examples) may be any valid
+[ALPN Protocol ID][].
+
+The syntax of these values is not validated by the Node.js implementation and
+are passed through as provided by the user or received from the peer.
+
 ### Class: ClientHttp2Session
 <!-- YAML
 added: v8.4.0
 -->
 
+#### Event: 'altsvc'
+<!-- YAML
+added: REPLACEME
+-->
+
+The `'altsvc'` event is emitted whenever an `ALTSVC` frame is received by
+the client. The event is emitted with the `ALTSVC` value, origin, and stream
+ID, if any. If no `origin` is provided in the `ALTSVC` frame, `origin` will
+be an empty string.
+
+```js
+const http2 = require('http2');
+const client = http2.connect('https://example.org');
+
+client.on('altsvc', (alt, origin, stream) => {
+  console.log(alt);
+  console.log(origin);
+  console.log(stream);
+});
+```
+
 #### clienthttp2session.request(headers[, options])
 <!-- YAML
 added: v8.4.0
@@ -2850,6 +2942,7 @@ following additional properties:
 
 
 [ALPN negotiation]: #http2_alpn_negotiation
+[ALPN Protocol ID]: https://www.iana.org/assignments/tls-extensiontype-values/tls-extensiontype-values.xhtml#alpn-protocol-ids
 [Compatibility API]: #http2_compatibility_api
 [HTTP/1]: http.html
 [HTTP/2]: https://tools.ietf.org/html/rfc7540
@@ -2858,6 +2951,7 @@ following additional properties:
 [Http2Session and Sockets]: #http2_http2session_and_sockets
 [Performance Observer]: perf_hooks.html
 [Readable Stream]: stream.html#stream_class_stream_readable
+[RFC 7838]: https://tools.ietf.org/html/rfc7838
 [Settings Object]: #http2_settings_object
 [Using options.selectPadding]: #http2_using_options_selectpadding
 [Writable Stream]: stream.html#stream_writable_streams

lib/internal/errors.js

@@ -304,6 +304,10 @@ E('ERR_FS_INVALID_SYMLINK_TYPE',
   'Symlink type must be one of "dir", "file", or "junction". Received "%s"');
 E('ERR_HTTP2_ALREADY_SHUTDOWN',
   'Http2Session is already shutdown or destroyed');
+E('ERR_HTTP2_ALTSVC_INVALID_ORIGIN',
+  'HTTP/2 ALTSVC frames require a valid origin');
+E('ERR_HTTP2_ALTSVC_LENGTH',
+  'HTTP/2 ALTSVC frames are limited to 16382 bytes');
 E('ERR_HTTP2_CONNECT_AUTHORITY',
   ':authority header is required for CONNECT requests');
 E('ERR_HTTP2_CONNECT_PATH',

lib/internal/http2/core.js

@@ -32,6 +32,9 @@ const kMaxFrameSize = (2 ** 24) - 1;
 const kMaxInt = (2 ** 32) - 1;
 const kMaxStreams = (2 ** 31) - 1;
 
+// eslint-disable-next-line no-control-regex
+const kQuotedString = /^[\x09\x20-\x5b\x5d-\x7e\x80-\xff]*$/;
+
 const {
   assertIsObject,
   assertValidPseudoHeaderResponse,
@@ -364,6 +367,16 @@ function onFrameError(id, type, code) {
   process.nextTick(emit, emitter, 'frameError', type, code, id);
 }
 
+function onAltSvc(stream, origin, alt) {
+  const session = this[kOwner];
+  if (session.destroyed)
+    return;
+  debug(`Http2Session ${sessionName(session[kType])}: altsvc received: ` +
+        `stream: ${stream}, origin: ${origin}, alt: ${alt}`);
+  session[kUpdateTimer]();
+  process.nextTick(emit, session, 'altsvc', alt, origin, stream);
+}
+
 // Receiving a GOAWAY frame from the connected peer is a signal that no
 // new streams should be created. If the code === NGHTTP2_NO_ERROR, we
 // are going to send our close, but allow existing frames to close
@@ -706,6 +719,7 @@ function setupHandle(socket, type, options) {
   handle.onheaders = onSessionHeaders;
   handle.onframeerror = onFrameError;
   handle.ongoawaydata = onGoawayData;
+  handle.onaltsvc = onAltSvc;
 
   if (typeof options.selectPadding === 'function')
     handle.ongetpadding = onSelectPadding(options.selectPadding);
@@ -1154,6 +1168,54 @@ class ServerHttp2Session extends Http2Session {
   get server() {
     return this[kServer];
   }
+
+  // Submits an altsvc frame to be sent to the client. `stream` is a
+  // numeric Stream ID. origin is a URL string that will be used to get
+  // the origin. alt is a string containing the altsvc details. No fancy
+  // API is provided for that.
+  altsvc(alt, originOrStream) {
+    if (this.destroyed)
+      throw new errors.Error('ERR_HTTP2_INVALID_SESSION');
+
+    let stream = 0;
+    let origin;
+
+    if (typeof originOrStream === 'string') {
+      origin = (new URL(originOrStream)).origin;
+      if (origin === 'null')
+        throw new errors.TypeError('ERR_HTTP2_ALTSVC_INVALID_ORIGIN');
+    } else if (typeof originOrStream === 'number') {
+      if (originOrStream >>> 0 !== originOrStream || originOrStream === 0)
+        throw new errors.RangeError('ERR_OUT_OF_RANGE', 'originOrStream');
+      stream = originOrStream;
+    } else if (originOrStream !== undefined) {
+      // Allow origin to be passed a URL or object with origin property
+      if (originOrStream !== null && typeof originOrStream === 'object')
+        origin = originOrStream.origin;
+      // Note: if originOrStream is an object with an origin property other
+      // than a URL, then it is possible that origin will be malformed.
+      // We do not verify that here. Users who go that route need to
+      // ensure they are doing the right thing or the payload data will
+      // be invalid.
+      if (typeof origin !== 'string') {
+        throw new errors.TypeError('ERR_INVALID_ARG_TYPE', 'originOrStream',
+                                   ['string', 'number', 'URL', 'object']);
+      } else if (origin === 'null' || origin.length === 0) {
+        throw new errors.TypeError('ERR_HTTP2_ALTSVC_INVALID_ORIGIN');
+      }
+    }
+
+    if (typeof alt !== 'string')
+      throw new errors.TypeError('ERR_INVALID_ARG_TYPE', 'alt', 'string');
+    if (!kQuotedString.test(alt))
+      throw new errors.TypeError('ERR_INVALID_CHAR', 'alt');
+
+    // Max length permitted for ALTSVC
+    if ((alt.length + (origin !== undefined ? origin.length : 0)) > 16382)
+      throw new errors.TypeError('ERR_HTTP2_ALTSVC_LENGTH');
+
+    this[kHandle].altsvc(stream, origin || '', alt);
+  }
 }
 
 // ClientHttp2Session instances have to wait for the socket to connect after

src/env.h

@@ -179,6 +179,7 @@ class ModuleWrap;
   V(netmask_string, "netmask")                                                \
   V(nsname_string, "nsname")                                                  \
   V(ocsp_request_string, "OCSPRequest")                                       \
+  V(onaltsvc_string, "onaltsvc")                                              \
   V(onchange_string, "onchange")                                              \
   V(onclienthello_string, "onclienthello")                                    \
   V(oncomplete_string, "oncomplete")                                          \

src/node_http2.cc

@@ -103,6 +103,11 @@ Http2Options::Http2Options(Environment* env) {
   // are required to buffer.
   nghttp2_option_set_no_auto_window_update(options_, 1);
 
+  // Enable built in support for ALTSVC frames. Once we add support for
+  // other non-built in extension frames, this will need to be handled
+  // a bit differently. For now, let's let nghttp2 take care of it.
+  nghttp2_option_set_builtin_recv_extension_type(options_, NGHTTP2_ALTSVC);
+
   AliasedBuffer<uint32_t, v8::Uint32Array>& buffer =
       env->http2_state()->options_buffer;
   uint32_t flags = buffer[IDX_OPTIONS_FLAGS];
@@ -847,6 +852,10 @@ inline int Http2Session::OnFrameReceive(nghttp2_session* handle,
       break;
     case NGHTTP2_PING:
       session->HandlePingFrame(frame);
+      break;
+    case NGHTTP2_ALTSVC:
+      session->HandleAltSvcFrame(frame);
+      break;
     default:
       break;
   }
@@ -1185,6 +1194,34 @@ inline void Http2Session::HandleGoawayFrame(const nghttp2_frame* frame) {
   MakeCallback(env()->ongoawaydata_string(), arraysize(argv), argv);
 }
 
+// Called by OnFrameReceived when a complete ALTSVC frame has been received.
+inline void Http2Session::HandleAltSvcFrame(const nghttp2_frame* frame) {
+  Isolate* isolate = env()->isolate();
+  HandleScope scope(isolate);
+  Local<Context> context = env()->context();
+  Context::Scope context_scope(context);
+
+  int32_t id = GetFrameID(frame);
+
+  nghttp2_extension ext = frame->ext;
+  nghttp2_ext_altsvc* altsvc = static_cast<nghttp2_ext_altsvc*>(ext.payload);
+  DEBUG_HTTP2SESSION(this, "handling altsvc frame");
+
+  Local<Value> argv[3] = {
+    Integer::New(isolate, id),
+    String::NewFromOneByte(isolate,
+                           altsvc->origin,
+                           v8::NewStringType::kNormal,
+                           altsvc->origin_len).ToLocalChecked(),
+    String::NewFromOneByte(isolate,
+                           altsvc->field_value,
+                           v8::NewStringType::kNormal,
+                           altsvc->field_value_len).ToLocalChecked(),
+  };
+
+  MakeCallback(env()->onaltsvc_string(), arraysize(argv), argv);
+}
+
 // Called by OnFrameReceived when a complete PING frame has been received.
 inline void Http2Session::HandlePingFrame(const nghttp2_frame* frame) {
   bool ack = frame->hd.flags & NGHTTP2_FLAG_ACK;
@@ -2494,6 +2531,44 @@ void Http2Stream::RefreshState(const FunctionCallbackInfo<Value>& args) {
   }
 }
 
+void Http2Session::AltSvc(int32_t id,
+                          uint8_t* origin,
+                          size_t origin_len,
+                          uint8_t* value,
+                          size_t value_len) {
+  Http2Scope h2scope(this);
+  CHECK_EQ(nghttp2_submit_altsvc(session_, NGHTTP2_FLAG_NONE, id,
+                                 origin, origin_len, value, value_len), 0);
+}
+
+// Submits an AltSvc frame to the sent to the connected peer.
+void Http2Session::AltSvc(const FunctionCallbackInfo<Value>& args) {
+  Environment* env = Environment::GetCurrent(args);
+  Http2Session* session;
+  ASSIGN_OR_RETURN_UNWRAP(&session, args.Holder());
+
+  int32_t id = args[0]->Int32Value(env->context()).ToChecked();
+
+  // origin and value are both required to be ASCII, handle them as such.
+  Local<String> origin_str = args[1]->ToString(env->context()).ToLocalChecked();
+  Local<String> value_str = args[2]->ToString(env->context()).ToLocalChecked();
+
+  size_t origin_len = origin_str->Length();
+  size_t value_len = value_str->Length();
+
+  CHECK_LE(origin_len + value_len, 16382);  // Max permitted for ALTSVC
+  // Verify that origin len != 0 if stream id == 0, or
+  // that origin len == 0 if stream id != 0
+  CHECK((origin_len != 0 && id == 0) || (origin_len == 0 && id != 0));
+
+  MaybeStackBuffer<uint8_t> origin(origin_len);
+  MaybeStackBuffer<uint8_t> value(value_len);
+  origin_str->WriteOneByte(*origin);
+  value_str->WriteOneByte(*value);
+
+  session->AltSvc(id, *origin, origin_len, *value, value_len);
+}
+
 // Submits a PING frame to be sent to the connected peer.
 void Http2Session::Ping(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
@@ -2711,6 +2786,7 @@ void Initialize(Local<Object> target,
   session->SetClassName(http2SessionClassName);
   session->InstanceTemplate()->SetInternalFieldCount(1);
   AsyncWrap::AddWrapMethods(env, session);
+  env->SetProtoMethod(session, "altsvc", Http2Session::AltSvc);
   env->SetProtoMethod(session, "ping", Http2Session::Ping);
   env->SetProtoMethod(session, "consume", Http2Session::Consume);
   env->SetProtoMethod(session, "destroy", Http2Session::Destroy);

src/node_http2.h

@@ -800,6 +800,11 @@ class Http2Session : public AsyncWrap {
   void Consume(Local<External> external);
   void Unconsume();
   void Goaway(uint32_t code, int32_t lastStreamID, uint8_t* data, size_t len);
+  void AltSvc(int32_t id,
+              uint8_t* origin,
+              size_t origin_len,
+              uint8_t* value,
+              size_t value_len);
 
   bool Ping(v8::Local<v8::Function> function);
 
@@ -879,6 +884,7 @@ class Http2Session : public AsyncWrap {
   static void UpdateChunksSent(const FunctionCallbackInfo<Value>& args);
   static void RefreshState(const FunctionCallbackInfo<Value>& args);
   static void Ping(const FunctionCallbackInfo<Value>& args);
+  static void AltSvc(const FunctionCallbackInfo<Value>& args);
 
   template <get_setting fn>
   static void RefreshSettings(const FunctionCallbackInfo<Value>& args);
@@ -923,6 +929,7 @@ class Http2Session : public AsyncWrap {
   inline void HandlePriorityFrame(const nghttp2_frame* frame);
   inline void HandleSettingsFrame(const nghttp2_frame* frame);
   inline void HandlePingFrame(const nghttp2_frame* frame);
+  inline void HandleAltSvcFrame(const nghttp2_frame* frame);
 
   // nghttp2 callbacks
   static inline int OnBeginHeadersCallback(