Configurable max request header size

integration/simple_test.go

@@ -1511,3 +1511,63 @@ func (s *SimpleSuite) TestDenyFragment() {
 	require.NoError(s.T(), err)
 	assert.Equal(s.T(), http.StatusBadRequest, resp.StatusCode)
 }
+
+func (s *SimpleSuite) TestMaxHeaderBytes() {
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	})
+
+	listener, err := net.Listen("tcp", "127.0.0.1:9000")
+	require.NoError(s.T(), err)
+
+	ts := &httptest.Server{
+		Listener: listener,
+		Config: &http.Server{
+			Handler:        handler,
+			MaxHeaderBytes: 1.25 * 1024 * 1024, // 1.25 MB
+		},
+	}
+	ts.Start()
+	defer ts.Close()
+
+	// The test server and traefik config file both specify a max request header size of 1.25 MB.
+	file := s.adaptFile("fixtures/simple_max_header_size.toml", struct {
+		TestServer string
+	}{ts.URL})
+
+	s.traefikCmd(withConfigFile(file))
+
+	testCases := []struct {
+		name           string
+		headerSize     int
+		expectedStatus int
+	}{
+		{
+			name:           "1.25MB header",
+			headerSize:     int(1.25 * 1024 * 1024),
+			expectedStatus: http.StatusOK,
+		},
+		{
+			name:           "1.5MB header",
+			headerSize:     int(1.5 * 1024 * 1024),
+			expectedStatus: http.StatusRequestHeaderFieldsTooLarge,
+		},
+		{
+			name:           "500KB header",
+			headerSize:     int(500 * 1024),
+			expectedStatus: http.StatusOK,
+		},
+	}
+
+	for _, test := range testCases {
+		s.Run(test.name, func() {
+			req, err := http.NewRequest(http.MethodGet, "http://127.0.0.1:8000", nil)
+			require.NoError(s.T(), err)
+
+			req.Header.Set("X-Large-Header", strings.Repeat("A", test.headerSize))
+
+			err = try.Request(req, 2*time.Second, try.StatusCodeIs(test.expectedStatus))
+			require.NoError(s.T(), err)
+		})
+	}
+}