quic: allow multiple independent .connect() calls

Explicitly allow calling `.connect()` multiple times to generate
separate client sessions on the same socket. This requires making
`kMaybeBind` call its callback even if the socket is already bound.

PR-URL: nodejs#176
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/quic.md

@@ -688,7 +688,9 @@ added: REPLACEME
     be `'udp4'`, indicating UDP over IPv4, or `'udp6'`, indicating UDP over
     IPv6. Defaults to `'udp4'`.
 
-Create a new `QuicClientSession`.
+Create a new `QuicClientSession`. This function can be called multiple times
+to create sessions associated with different endpoints on the same
+client endpoint.
 
 ### quicsocket.destroy([error])
 <!-- YAML

lib/internal/quic/core.js

@@ -741,15 +741,18 @@ class QuicSocket extends EventEmitter {
   }
 
   // Bind the UDP socket on demand, only if it hasn't already been bound.
-  // Function is a non-op if the socket is already bound
+  // Function is a non-op if the socket is already bound or in the process of
+  // being bound, and will call the callback once the socket is ready.
   [kMaybeBind](callback = () => {}) {
+    if (this.#state !== kSocketUnbound) {
+      if (this.bound)
+        return process.nextTick(callback);
+      else
+        return this.on('ready', callback);
+    }
     // This socket will be in a pending state until it is bound. Once bound,
     // the this[kReady]() method will be called, switching the state to
-    // kSocketBound and notifying the associated sessions
-    // TODO(@jasnell): If the socket is already bound, the callback should
-    // be invoked with an error.
-    if (this.#state !== kSocketUnbound)
-      return;
+    // kSocketBound and notifying the associated sessions.
     this.#state = kSocketPending;
     this.#lookup(this.#address, afterLookup.bind(this, callback));
   }
@@ -930,18 +933,12 @@ class QuicSocket extends EventEmitter {
     if (typeof callback === 'function')
       session.on('ready', callback);
 
-    const afterBind =
-        connectAfterBind.bind(
-          this,
-          session,
-          this.#lookup,
-          address,
-          getSocketType(type));
-    if (this.#state === kSocketBound) {
-      afterBind();
-    } else {
-      this[kMaybeBind](afterBind);
-    }
+    this[kMaybeBind](connectAfterBind.bind(
+        this,
+        session,
+        this.#lookup,
+        address,
+        getSocketType(type)));
 
     return session;
   }

test/parallel/test-quic-client-connect-multiple-sequential.js

@@ -52,6 +52,7 @@ const { once } = require('events');
     }
   });
 
+  let done = 0;
   for (const server of servers) {
     const req = client.connect({
       address: 'localhost',
@@ -60,7 +61,7 @@ const { once } = require('events');
 
     const [ stream ] = await once(req, 'stream');
     stream.resume();
-    await once(stream, 'end');
+    await(stream, 'end');
 
     server.close();
     req.close();