http: add rawPacket in err of clientError event

The `rawPacket` is the current buffer that just parsed. Adding this
buffer to the error object of `clientError` event is to make it possible
that developers can log the broken packet.

doc/api/http.md

@@ -765,6 +765,11 @@ object, so any HTTP response sent, including response headers and payload,
 *must* be written directly to the `socket` object. Care must be taken to
 ensure the response is a properly formatted HTTP response message.
 
+> `err` is an instance of `Error` with two extra columns:
+>
+> + `bytesParsed`: the bytes count of request packet that Node.js may parse correctly;
+> + `rawPacket`: the raw packet of current request.
+
 ### Event: 'close'
 <!-- YAML
 added: v0.1.4

lib/_http_server.js

@@ -476,6 +476,7 @@ function onParserExecuteCommon(server, socket, parser, state, ret, d) {
   resetSocketTimeout(server, socket, state);
 
   if (ret instanceof Error) {
+    ret.rawPacket = d || parser.getCurrentBuffer();
     debug('parse error', ret);
     socketOnError.call(socket, ret);
   } else if (parser.incoming && parser.incoming.upgrade) {

test/parallel/test-http-server-client-error.js

@@ -10,6 +10,12 @@ const server = http.createServer(common.mustCall(function(req, res) {
 }));
 
 server.on('clientError', common.mustCall(function(err, socket) {
+  assert.strictEqual(err instanceof Error, true);
+  assert.strictEqual(err.code, 'HPE_INVALID_METHOD');
+  assert.strictEqual(err.bytesParsed, 1);
+  assert.strictEqual(err.message, 'Parse Error');
+  assert.strictEqual(err.rawPacket.toString(), 'Oopsie-doopsie\r\n');
+
   socket.end('HTTP/1.1 400 Bad Request\r\n\r\n');
 
   server.close();