added login and permission fix

internal/client/use.go

@@ -272,6 +272,7 @@ func (um *UseManager) tunnelReadLoop(tunnel *useTunnel) {
 		}
 
 		if err := um.client.SendTunnelData(tunnel.id, buf[:n]); err != nil {
+			log.Printf("[use] tunnel send error: %v", err)
 			return
 		}
 	}
@@ -326,11 +327,17 @@ func (um *UseManager) handleTunnelData(tunnelID string, data []byte) {
 	um.mu.RUnlock()
 
 	if !exists {
+		log.Printf("[use] tunnel data for unknown tunnel %s (%d bytes)", tunnelID[:8], len(data))
 		return
 	}
 
 	// Write to the tunnel socket (relay -> VHCI)
-	tunnel.conn.Write(data)
+	n, err := tunnel.conn.Write(data)
+	if err != nil {
+		log.Printf("[use] tunnel write error: %v", err)
+	} else if n != len(data) {
+		log.Printf("[use] tunnel short write: %d/%d", n, len(data))
+	}
 }
 
 func (um *UseManager) handleClientLeft(msg *protocol.ClientLeft) {