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

Assisted-by: GLM 5.3 Flash

cmd/nfsd/notify_test.go

@@ -0,0 +1,66 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: MIT
+
+package main
+
+import (
+	"net"
+	"path/filepath"
+	"testing"
+	"time"
+)
+
+// TestNotifyReadyWithoutSocket covers the quiet path: no NOTIFY_SOCKET,
+// no notification, no error. This is every run outside a Type=notify
+// unit.
+func TestNotifyReadyWithoutSocket(t *testing.T) {
+	t.Setenv("NOTIFY_SOCKET", "")
+	if err := notifyReady(); err != nil {
+		t.Fatalf("notify without a socket: %v", err)
+	}
+}
+
+// expectReady reads one datagram and reports whether it is READY=1.
+func expectReady(t *testing.T, ln *net.UnixConn) {
+	t.Helper()
+	buf := make([]byte, 64)
+	ln.SetReadDeadline(time.Now().Add(2 * time.Second))
+	n, _, err := ln.ReadFrom(buf)
+	if err != nil {
+		t.Fatalf("read: %v", err)
+	}
+	if string(buf[:n]) != "READY=1" {
+		t.Fatalf("message %q, want READY=1", buf[:n])
+	}
+}
+
+// TestNotifyReadyDelivers covers the pathname socket form.
+func TestNotifyReadyDelivers(t *testing.T) {
+	sock := filepath.Join(t.TempDir(), "notify.sock")
+	ln, err := net.ListenUnixgram("unixgram", &net.UnixAddr{Name: sock, Net: "unixgram"})
+	if err != nil {
+		t.Fatalf("listen: %v", err)
+	}
+	defer ln.Close()
+	t.Setenv("NOTIFY_SOCKET", sock)
+	if err := notifyReady(); err != nil {
+		t.Fatalf("notify: %v", err)
+	}
+	expectReady(t, ln)
+}
+
+// TestNotifyReadyAbstract covers the abstract namespace form, the one
+// systemd hands over on Linux.
+func TestNotifyReadyAbstract(t *testing.T) {
+	addr := "@" + filepath.Base(t.TempDir()) + "-notify"
+	ln, err := net.ListenUnixgram("unixgram", &net.UnixAddr{Name: addr, Net: "unixgram"})
+	if err != nil {
+		t.Skipf("abstract unix sockets are unavailable: %v", err)
+	}
+	defer ln.Close()
+	t.Setenv("NOTIFY_SOCKET", addr)
+	if err := notifyReady(); err != nil {
+		t.Fatalf("notify: %v", err)
+	}
+	expectReady(t, ln)
+}