http2: add initial support for originSet

Add new properties to `Http2Session` to identify alpnProtocol,
and indicator about whether the session is TLS or not, and
initial support for origin set (preparinng for `ORIGIN` frame
support and the client-side `Pool` implementation.

The `originSet` is the set of origins for which an `Http2Session`
may be considered authoritative. Per the `ORIGIN` frame spec,
the originSet is only valid on TLS connections, so this is only
exposed when using a `TLSSocket`.

doc/api/http2.md

@@ -283,6 +283,18 @@ session.setTimeout(2000);
 session.on('timeout', () => { /** .. **/ });
 ```
 
+#### http2session.alpnProtocol
+<!-- YAML
+added: REPLACEME
+-->
+
+* Value: {string|undefined}
+
+Value will be `undefined` if the `Http2Session` is not yet connected to a
+socket, `h2c` if the `Http2Session` is not connected to a `TLSSocket`, or
+will return the value of the connected `TLSSocket`'s own `alpnProtocol`
+property.
+
 #### http2session.close([callback])
 <!-- YAML
 added: REPLACEME
@@ -340,6 +352,18 @@ added: v8.4.0
 Will be `true` if this `Http2Session` instance has been destroyed and must no
 longer be used, otherwise `false`.
 
+#### http2session.encrypted
+<!-- YAML
+added: REPLACEME
+-->
+
+* Value: {boolean|undefined}
+
+Value is `undefined` if the `Http2Session` session socket has not yet been
+connected, `true` if the `Http2Session` is connected with a `TLSSocket`,
+and `false` if the `Http2Session` is connected to any other kind of socket
+or stream.
+
 #### http2session.goaway([code, [lastStreamID, [opaqueData]]])
 <!-- YAML
 added: REPLACEME
@@ -363,6 +387,17 @@ added: v8.4.0
 A prototype-less object describing the current local settings of this
 `Http2Session`. The local settings are local to *this* `Http2Session` instance.
 
+#### http2session.originSet
+<!-- YAML
+added: REPLACEME
+-->
+
+* Value: {string[]|undefined}
+
+If the `Http2Session` is connected to a `TLSSocket`, the `originSet` property
+will return an Array of origins for which the `Http2Session` may be
+considered authoritative.
+
 #### http2session.pendingSettingsAck
 <!-- YAML
 added: v8.4.0

lib/internal/http2/core.js

@@ -70,7 +70,9 @@ const TLSServer = tls.Server;
 
 const kInspect = require('internal/util').customInspectSymbol;
 
+const kAlpnProtocol = Symbol('alpnProtocol');
 const kAuthority = Symbol('authority');
+const kEncrypted = Symbol('encrypted');
 const kHandle = Symbol('handle');
 const kID = Symbol('id');
 const kInit = Symbol('init');
@@ -731,6 +733,17 @@ function setupHandle(socket, type, options) {
 
   this[kHandle] = handle;
 
+  if (socket.encrypted) {
+    this[kAlpnProtocol] = socket.alpnProtocol;
+    this[kEncrypted] = true;
+  } else {
+    // 'h2c' is the protocol identifier for HTTP/2 over plain-text. We use
+    // it here to identify any session that is not explicitly using an
+    // encrypted socket.
+    this[kAlpnProtocol] = 'h2c';
+    this[kEncrypted] = false;
+  }
+
   const settings = typeof options.settings === 'object' ?
     options.settings : {};
 
@@ -805,9 +818,12 @@ class Http2Session extends EventEmitter {
       streams: new Map(),
       pendingStreams: new Set(),
       pendingAck: 0,
-      writeQueueSize: 0
+      writeQueueSize: 0,
+      originSet: undefined
     };
 
+    this[kEncrypted] = undefined;
+    this[kAlpnProtocol] = undefined;
     this[kType] = type;
     this[kProxySocket] = null;
     this[kSocket] = socket;
@@ -833,6 +849,46 @@ class Http2Session extends EventEmitter {
     debug(`Http2Session ${sessionName(type)}: created`);
   }
 
+  // Returns undefined if the socket is not yet connected, true if the
+  // socket is a TLSSocket, and false if it is not.
+  get encrypted() {
+    return this[kEncrypted];
+  }
+
+  // Returns undefined if the socket is not yet connected, `h2` if the
+  // socket is a TLSSocket and the alpnProtocol is `h2`, or `h2c` if the
+  // socket is not a TLSSocket.
+  get alpnProtocol() {
+    return this[kAlpnProtocol];
+  }
+
+  // TODO(jasnell): originSet is being added in preparation for ORIGIN frame
+  // support. At the current time, the ORIGIN frame specification is awaiting
+  // publication as an RFC and is awaiting implementation in nghttp2. Once
+  // added, an ORIGIN frame will add to the origins included in the origin
+  // set. 421 responses will remove origins from the set.
+  get originSet() {
+    if (!this.encrypted || this.destroyed)
+      return undefined;
+
+    let originSet = this[kState].originSet;
+    if (originSet === undefined) {
+      const socket = this[kSocket];
+      this[kState].originSet = originSet = new Set();
+      if (socket.servername != null) {
+        let originString = `https://${socket.servername}`;
+        if (socket.remotePort != null)
+          originString += `:${socket.remotePort}`;
+        // We have to ensure that it is a properly serialized
+        // ASCII origin string. The socket.servername might not
+        // be properly ASCII encoded.
+        originSet.add((new URL(originString)).origin);
+      }
+    }
+
+    return Array.from(originSet);
+  }
+
   // True if the Http2Session is still waiting for the socket to connect
   get connecting() {
     return (this[kState].flags & SESSION_FLAGS_READY) === 0;

test/parallel/test-http2-create-client-secure-session.js

@@ -19,6 +19,14 @@ function loadKey(keyname) {
 
 function onStream(stream, headers) {
   const socket = stream.session[kSocket];
+
+  assert(stream.session.encrypted);
+  assert(stream.session.alpnProtocol, 'h2');
+  const originSet = stream.session.originSet;
+  assert(Array.isArray(originSet));
+  assert.strictEqual(originSet[0],
+                     `https://${socket.servername}:${socket.remotePort}`);
+
   assert(headers[':authority'].startsWith(socket.servername));
   stream.respond({ 'content-type': 'application/json' });
   stream.end(JSON.stringify({
@@ -39,6 +47,17 @@ function verifySecureSession(key, cert, ca, opts) {
     assert.strictEqual(client.socket.listenerCount('secureConnect'), 1);
     const req = client.request();
 
+    client.on('connect', common.mustCall(() => {
+      assert(client.encrypted);
+      assert.strictEqual(client.alpnProtocol, 'h2');
+      const originSet = client.originSet;
+      assert(Array.isArray(originSet));
+      assert.strictEqual(originSet.length, 1);
+      assert.strictEqual(
+        originSet[0],
+        `https://${opts.servername || 'localhost'}:${server.address().port}`);
+    }));
+
     req.on('response', common.mustCall((headers) => {
       assert.strictEqual(headers[':status'], 200);
       assert.strictEqual(headers['content-type'], 'application/json');

test/parallel/test-http2-create-client-session.js

@@ -34,10 +34,16 @@ server.listen(0);
 server.on('listening', common.mustCall(() => {
 
   const client = h2.connect(`http://localhost:${server.address().port}`);
-  client.setMaxListeners(100);
+  client.setMaxListeners(101);
 
   client.on('goaway', console.log);
 
+  client.on('connect', common.mustCall(() => {
+    assert(!client.encrypted);
+    assert(!client.originSet);
+    assert.strictEqual(client.alpnProtocol, 'h2c');
+  }));
+
   const countdown = new Countdown(count, () => {
     client.close();
     server.close();