simplify generation of stateless reset tokens (#4858)

stateless_reset_test.go

@@ -0,0 +1,42 @@
+package quic
+
+import (
+	"crypto/rand"
+	"testing"
+
+	"github.com/quic-go/quic-go/internal/protocol"
+	"github.com/stretchr/testify/require"
+)
+
+func TestStatelessResetter(t *testing.T) {
+	t.Run("no key", func(t *testing.T) {
+		r1 := newStatelessResetter(nil)
+		r2 := newStatelessResetter(nil)
+		for i := 0; i < 100; i++ {
+			b := make([]byte, 15)
+			rand.Read(b)
+			connID := protocol.ParseConnectionID(b)
+			t1 := r1.GetStatelessResetToken(connID)
+			t2 := r2.GetStatelessResetToken(connID)
+			require.NotZero(t, t1)
+			require.NotZero(t, t2)
+			require.NotEqual(t, t1, t2)
+		}
+	})
+
+	t.Run("with key", func(t *testing.T) {
+		var key StatelessResetKey
+		rand.Read(key[:])
+		m := newStatelessResetter(&key)
+		b := make([]byte, 8)
+		rand.Read(b)
+		connID := protocol.ParseConnectionID(b)
+		token := m.GetStatelessResetToken(connID)
+		require.NotZero(t, token)
+		require.Equal(t, token, m.GetStatelessResetToken(connID))
+		// generate a new connection ID
+		rand.Read(b)
+		connID2 := protocol.ParseConnectionID(b)
+		require.NotEqual(t, token, m.GetStatelessResetToken(connID2))
+	})
+}