fix RRD implementation on network troughput

backend/internal/system/service.go

@@ -24,11 +24,64 @@ type Service struct {
 	rrdService *RRDService
 }
 
+// detectPrimaryInterface detects the primary network interface (first non-loopback with IP)
+func detectPrimaryInterface(ctx context.Context) string {
+	// Try to get default route interface
+	cmd := exec.CommandContext(ctx, "ip", "route", "show", "default")
+	output, err := cmd.Output()
+	if err == nil {
+		lines := strings.Split(string(output), "\n")
+		for _, line := range lines {
+			if strings.Contains(line, "dev ") {
+				parts := strings.Fields(line)
+				for i, part := range parts {
+					if part == "dev" && i+1 < len(parts) {
+						iface := parts[i+1]
+						if iface != "lo" {
+							return iface
+						}
+					}
+				}
+			}
+		}
+	}
+
+	// Fallback: get first non-loopback interface with IP
+	cmd = exec.CommandContext(ctx, "ip", "-4", "addr", "show")
+	output, err = cmd.Output()
+	if err == nil {
+		lines := strings.Split(string(output), "\n")
+		for _, line := range lines {
+			line = strings.TrimSpace(line)
+			// Look for interface name line (e.g., "2: ens18: <BROADCAST...")
+			if len(line) > 0 && line[0] >= '0' && line[0] <= '9' && strings.Contains(line, ":") {
+				parts := strings.Fields(line)
+				if len(parts) >= 2 {
+					iface := strings.TrimSuffix(parts[1], ":")
+					if iface != "" && iface != "lo" {
+						// Check if this interface has an IP (next lines will have "inet")
+						// For simplicity, return first non-loopback interface
+						return iface
+					}
+				}
+			}
+		}
+	}
+
+	// Final fallback
+	return "eth0"
+}
+
 // NewService creates a new system service
 func NewService(log *logger.Logger) *Service {
-	// Initialize RRD service for network monitoring (default to eth0, can be configured)
+	// Initialize RRD service for network monitoring
 	rrdDir := "/var/lib/calypso/rrd"
-	interfaceName := "eth0" // Default interface, can be made configurable
+
+	// Auto-detect primary interface
+	ctx := context.Background()
+	interfaceName := detectPrimaryInterface(ctx)
+	log.Info("Detected primary network interface", "interface", interfaceName)
+
 	rrdService := NewRRDService(log, rrdDir, interfaceName)
 
 	return &Service{