package config import ( _ "embed" "encoding/json" "fmt" "net" "os" "path/filepath" "strings" "git.cryptic.systems/volker.raschek/dyndns-client/pkg/types" log "github.com/sirupsen/logrus" ) //go:embed config.json var defaultConfig string // GetDefaultConfiguration returns a default configuration func GetDefaultConfiguration() (*types.Config, error) { cnf := new(types.Config) jsonDecoder := json.NewDecoder(strings.NewReader(defaultConfig)) err := jsonDecoder.Decode(cnf) if err != nil { return nil, fmt.Errorf("failed to decode default config: %w", err) } defaultInterface, err := getDefaultInterfaceByIP() if err != nil { return nil, err } cnf.Ifaces = []string{defaultInterface.Name} return cnf, nil } // Read config from a file func Read(cnfFile string) (*types.Config, error) { // Load burned in configuration if config not available if _, err := os.Stat(cnfFile); os.IsNotExist(err) { if err := os.MkdirAll(filepath.Dir(cnfFile), 0755); err != nil { return nil, fmt.Errorf("failed to create directory: %w", err) } cnf, err := GetDefaultConfiguration() if err != nil { return nil, err } err = cnf.Validate() if err != nil { return nil, err } log.Infof("use embedded configuration") return cnf, nil } f, err := os.Open(cnfFile) if err != nil { return nil, fmt.Errorf("failed to open file: %w", err) } defer f.Close() cnf := new(types.Config) jsonDecoder := json.NewDecoder(f) err = jsonDecoder.Decode(cnf) if err != nil { return nil, fmt.Errorf("failed to decode json: %w", err) } for _, iface := range cnf.Ifaces { if _, err := net.InterfaceByName(iface); err != nil { return nil, fmt.Errorf("unknown interface: %v", iface) } } err = cnf.Validate() if err != nil { return nil, err } log.Infof("use configuration from file %v", cnfFile) return cnf, nil } // Write config into a file func Write(cnf *types.Config, cnfFile string) error { if _, err := os.Stat(filepath.Dir(cnfFile)); os.IsNotExist(err) { err := os.MkdirAll(filepath.Dir(cnfFile), 0755) if err != nil { return err } } f, err := os.Create(cnfFile) if err != nil { return fmt.Errorf("failed to create file %v: %v", cnfFile, err) } defer f.Close() jsonEncoder := json.NewEncoder(f) jsonEncoder.SetIndent("", " ") err = jsonEncoder.Encode(cnf) if err != nil { return fmt.Errorf("failed to encode json: %w", err) } return nil } func getDefaultInterfaceByIP() (*net.Interface, error) { ifaces, err := net.Interfaces() if err != nil { return nil, fmt.Errorf("failed to fet network interfaces from kernel: %w", err) } defaultIP := getOutboundIP() for _, iface := range ifaces { addrs, err := iface.Addrs() if err != nil { return nil, fmt.Errorf("failed to list ip addresses for interface %v: %w", iface.Name, err) } for _, addr := range addrs { addrIP := strings.Split(addr.String(), "/")[0] if addrIP == defaultIP.String() { return &iface, nil } } } return nil, fmt.Errorf("no interface found fo ip address %v", defaultIP) } func getOutboundIP() net.IP { conn, err := net.Dial("udp", "8.8.8.8:80") if err != nil { log.Fatal(err) } defer conn.Close() localAddr := conn.LocalAddr().(*net.UDPAddr) return localAddr.IP }