Refuse recursive requests

Co-authored-by: Michael <michael.matur@gmail.com>

pkg/middlewares/denyrouterrecursion/deny_router_recursion_test.go

@@ -0,0 +1,38 @@
+package denyrouterrecursion
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestServeHTTP(t *testing.T) {
+	req, err := http.NewRequest(http.MethodGet, "", nil)
+	require.NoError(t, err)
+
+	_, err = New("", http.HandlerFunc(func(_ http.ResponseWriter, _ *http.Request) {}))
+	require.Error(t, err)
+
+	next := 0
+	m, err := New("myRouter", http.HandlerFunc(func(_ http.ResponseWriter, _ *http.Request) {
+		next++
+	}))
+	require.NoError(t, err)
+
+	recorder := httptest.NewRecorder()
+	m.ServeHTTP(recorder, req)
+
+	assert.Equal(t, http.StatusOK, recorder.Code)
+	assert.Equal(t, "995d26092d19a224", m.routerNameHash)
+	assert.Equal(t, m.routerNameHash, req.Header.Get(xTraefikRouter))
+	assert.Equal(t, 1, next)
+
+	recorder = httptest.NewRecorder()
+	m.ServeHTTP(recorder, req)
+
+	assert.Equal(t, 1, next)
+	assert.Equal(t, http.StatusBadRequest, recorder.Code)
+}