http: set .code='ECONNRESET' on socket hang up errors

Fixes #1672.

lib/http2.js

@@ -1146,7 +1146,9 @@ ClientRequest.prototype.onSocket = function(socket) {
         // This socket error fired before we started to
         // receive a response. The error needs to
         // fire on the request.
-        req.emit('error', new Error('socket hang up'));
+        var error = new Error('socket hang up');
+        error.code = 'ECONNRESET';
+        req.emit('error', error);
       }
     }
     socket.on('close', closeListener);

test/simple/test-http-conn-reset.js

@@ -0,0 +1,56 @@
+// Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+var common = require('../common');
+var assert = require('assert');
+var http = require('http');
+var net = require('net');
+
+var caughtError = false;
+
+var options = {
+  host: '127.0.0.1',
+  port: common.PORT
+};
+
+// start a tcp server that closes incoming connections immediately
+var server = net.createServer(function(client) {
+  client.destroy();
+  server.close();
+});
+server.listen(options.port, options.host, onListen);
+
+// do a GET request, expect it to fail
+function onListen() {
+  var req = http.request(options, function(res) {
+    assert.ok(false, 'this should never run');
+  });
+  req.on('error', function(err) {
+    assert.equal(err.message, 'socket hang up');
+    assert.equal(err.code, 'ECONNRESET');
+    caughtError = true;
+  });
+  req.end();
+}
+
+process.on('exit', function() {
+  assert.equal(caughtError, true);
+});