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

Assisted-by: GLM 5.3 Flash

internal/rpc/gss_extra_test.go

@@ -0,0 +1,39 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: MIT
+
+package rpc
+
+import (
+	"testing"
+)
+
+// The RPCSEC_GSS_INIT result round trips: handle, statuses, window and
+// the reply token.
+func TestGSSInitResRoundTrip(t *testing.T) {
+	res := AppendGSSInitRes(nil, []byte("handle-2"), 0, 1, 32, []byte("ap-rep"))
+	handle, major, minor, window, token, err := DecodeGSSInitRes(res)
+	if err != nil || string(handle) != "handle-2" || major != 0 || minor != 1 ||
+		window != 32 || string(token) != "ap-rep" {
+		t.Fatalf("res %q %d %d %d %q %v", handle, major, minor, window, token, err)
+	}
+	// The empty refusal answers an empty handle and no token.
+	res = AppendGSSInitRes(nil, nil, 16<<16, 1, 0, nil)
+	if handle, major, _, _, token, err := DecodeGSSInitRes(res); err != nil ||
+		len(handle) != 0 || major != 16<<16 || len(token) != 0 {
+		t.Fatalf("refusal %q %d %q %v", handle, major, token, err)
+	}
+	// The error text of the credential sentinel is stable.
+	if ErrGSSCred.Error() == "" {
+		t.Fatal("empty error text")
+	}
+	// A truncated init result is refused word by word.
+	for n := 0; n < len(res); n++ {
+		if _, _, _, _, _, err := DecodeGSSInitRes(res[:n]); err == nil {
+			t.Fatalf("a %d byte prefix decoded cleanly", n)
+		}
+	}
+	// The NULL procedure constant the control exchange rides on.
+	if ProcedureNull != 0 {
+		t.Fatalf("null procedure %d", ProcedureNull)
+	}
+}