feat: node UUID

cmd/hvpn-node/hvpn-node.go

@@ -44,15 +44,19 @@ func main() {
     } else if uid == 0 {
         slog.Warn("Running as root! avoid running as root by setting CAP_NET_ADMIN")
     }
+    uuid, err := hvpnnode3.InitNodeUUID()
+    if err != nil {
+        slog.Error(err.Error())
+        os.Exit(-1)
+    }
+    slog.Info("Node UUID: " + uuid.String())
 
     app := createCliApp()
-    err := app.Run(os.Args)
+    err = app.Run(os.Args)
     if err != nil {
         slog.Error(err.Error())
         os.Exit(1)
     }
-
-
 }
 
 func run(ctx *cli.Context) {

node.go

@@ -0,0 +1,64 @@
+package hvpnnode3
+
+import (
+	"errors"
+	"fmt"
+	"log/slog"
+	"os"
+
+	"github.com/google/uuid"
+)
+
+const UUID_PATH = "/etc/hvpn/uuid"
+const CONFIG_PATH = "/etc/hvpn"
+const UUIDV4_LEN = 16
+
+// Gets or creates a UUID for this node
+func InitNodeUUID() (*uuid.UUID, error) {
+
+    // TODO: check and write to os.UserHomeDir() to avoid root
+    _, err := os.Stat(UUID_PATH)
+    if err != nil {
+        if errors.Is(err, os.ErrNotExist) {
+            slog.Info(UUID_PATH + " does not exist. Creating...")
+            return createNodeUUID()
+        }
+    }
+
+    f, err := os.Open(UUID_PATH)
+    if err != nil {
+        return nil, err
+    }
+    buffer := make([]byte, UUIDV4_LEN)
+    n, err := f.Read(buffer)
+    if err != nil {
+        return nil, err
+    }
+    slog.Debug("UUID: Read " + fmt.Sprint(n) + "bytes" )
+
+    uuid, err := uuid.FromBytes(buffer)
+    return &uuid, err
+}
+
+func createNodeUUID() (*uuid.UUID, error) {
+    err := os.MkdirAll(CONFIG_PATH, 0600)
+    if err != nil {
+        return nil, err
+    }
+
+    mode := os.O_RDWR | os.O_CREATE | os.O_EXCL
+    f, err := os.OpenFile(UUID_PATH, mode, 0600)
+    if err != nil {
+        return nil, err
+    }
+    uuid, err := uuid.NewRandom()
+    if err != nil {
+        return nil, err
+    }
+    n, err := f.Write(uuid[:])
+    if err != nil {
+        return nil, err
+    }
+    slog.Debug("UUID: Wrote " + fmt.Sprint(n) + "bytes")
+    return &uuid, nil  
+}