Resume the client socket when it is unpiped

.travis.yml

@@ -1,5 +1,3 @@
-sudo: false
-
 language: node_js
 
 node_js:
@@ -8,6 +6,8 @@ node_js:
   - "6"
   - "7"
   - "8"
+  - "10"
+  - "12"
 
 install:
   - PATH="`npm bin`:`npm bin -g`:$PATH"

proxy.js

@@ -339,9 +339,7 @@ function onconnect (req, socket, head) {
     res.removeListener('finish', onfinish);
 
     res.writeHead(200, 'Connection established');
-
-    // HACK: force a flush of the HTTP header
-    res._send('');
+    res.flushHeaders();
 
     // relinquish control of the `socket` from the ServerResponse instance
     res.detachSocket(socket);
@@ -351,6 +349,7 @@ function onconnect (req, socket, head) {
     res = null;
 
     socket.pipe(target);
+    target.once('unpipe', resume);
     target.pipe(socket);
   }
 
@@ -416,6 +415,17 @@ function onconnect (req, socket, head) {
   });
 }
 
+/**
+ * Resumes a socket.
+ *
+ * @param {(net.Socket|tls.Socket)} socket The socket to resume
+ * @api private
+ */
+
+function resume (socket) {
+  socket.resume();
+}
+
 /**
  * Checks `Proxy-Authorization` request headers. Same logic applied to CONNECT
  * requests as well as regular HTTP requests.

test/test.js

@@ -108,6 +108,48 @@ describe('proxy', function () {
     });
   });
 
+  it('should resume the client socket when it is unpiped', function (done) {
+    server.once('request', function (req, res) {
+      res.end();
+    });
+
+    var gotData = false;
+    var host = '127.0.0.1:' + serverPort;
+    var socket = net.connect({ port: proxyPort });
+
+    socket.on('connect', function () {
+      socket.write(
+        'CONNECT ' + host + ' HTTP/1.1\r\n' +
+        'Host: ' + host + '\r\n' +
+        '\r\n'
+      );
+    });
+
+    socket.on('close', function () {
+      assert(gotData);
+      done();
+    });
+
+    socket.setEncoding('utf8');
+    socket.once('data', function (data) {
+      assert(0 == data.indexOf('HTTP/1.1 200 Connection established\r\n'));
+
+      socket.write(
+        'POST / HTTP/1.1\r\n' +
+        'Host: ' + host + '\r\n' +
+        'Connection: close\r\n' +
+        'Transfer-Encoding: chunked\r\n' +
+        '\r\n'
+      );
+
+      socket.once('data', function (data) {
+        assert(0 == data.indexOf('HTTP/1.1 200 OK\r\n'));
+        gotData = true;
+        socket.write('10\r\n{ "foo": "bar",\r\n');
+      });
+    });
+  });
+
 
   describe('authentication', function () {
     function clearAuth () {