feat: full NFSv4.2 server and client in pure Go

Assisted-by: GLM 5.3 Flash

internal/xdr/fuzz_test.go

@@ -0,0 +1,67 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: MIT
+
+package xdr
+
+import (
+	"testing"
+)
+
+// FuzzDecoder feeds arbitrary bytes through every read of the decoder:
+// no input may panic, hang or index out of range, and every failure
+// arrives as an error.
+func FuzzDecoder(f *testing.F) {
+	f.Add([]byte{0, 0, 0, 1})
+	f.Add([]byte{0xff, 0xff, 0xff, 0xff})
+	f.Add([]byte{0, 0, 0, 2, 'a', 'b', 0})
+	f.Add([]byte{0, 0, 0, 5, 'h', 'e', 'l', 'l', 'o'})
+	f.Add([]byte{0x7f})
+	f.Add(make([]byte, 64))
+	f.Fuzz(func(t *testing.T, data []byte) {
+		d := NewDecoder(data)
+		_, _ = d.Uint32()
+		_, _ = d.Int64()
+		_, _ = d.Uint64()
+		_, _ = d.Bool()
+		_, _ = d.String()
+		_, _ = d.VarOpaque()
+		_, _ = d.FixedOpaque(4)
+		_, _ = d.Raw(3)
+		_ = d.Remaining()
+
+		// The writers must accept the decoded values back and the
+		// re-decode must agree or fail cleanly.
+		d2 := NewDecoder(data)
+		if s, err := d2.String(); err == nil {
+			again, aerr := NewDecoder(AppendString(nil, s)).String()
+			if aerr != nil || again != s {
+				t.Fatalf("string round trip: %q %v %q", s, aerr, again)
+			}
+		}
+		if o, err := d2.VarOpaque(); err == nil {
+			again, aerr := NewDecoder(AppendVarOpaque(nil, o)).VarOpaque()
+			if aerr != nil || string(again) != string(o) {
+				t.Fatal("opaque round trip")
+			}
+		}
+	})
+}
+
+// FuzzPadding checks the pad arithmetic against the property that an
+// encoded value always decodes back to itself, whatever the length.
+func FuzzPadding(f *testing.F) {
+	f.Add([]byte{})
+	f.Add([]byte("a"))
+	f.Add([]byte("abc"))
+	f.Add([]byte("abcd"))
+	f.Fuzz(func(t *testing.T, data []byte) {
+		enc := AppendVarOpaque(nil, data)
+		got, err := NewDecoder(enc).VarOpaque()
+		if err != nil {
+			t.Fatalf("decode of a value this package encoded: %v", err)
+		}
+		if string(got) != string(data) {
+			t.Fatalf("round trip: %q became %q", data, got)
+		}
+	})
+}