package udhcpc import ( "encoding/json" "fmt" "log" "net" "reflect" "strconv" "strings" "time" ) type Lease struct { // from https://udhcp.busybox.net/README.udhcpc IPAddress net.IP `env:"ip" json:"ip"` // The obtained IP Netmask net.IP `env:"subnet" json:"netmask"` // The assigned subnet mask Broadcast net.IP `env:"broadcast" json:"broadcast"` // The broadcast address for this network TTL int `env:"ipttl" json:"ttl,omitempty"` // The TTL to use for this network MTU int `env:"mtu" json:"mtu,omitempty"` // The MTU to use for this network HostName string `env:"hostname" json:"hostname,omitempty"` // The assigned hostname Domain string `env:"domain" json:"domain,omitempty"` // The domain name of the network BootPNextServer net.IP `env:"siaddr" json:"bootp_next_server,omitempty"` // The bootp next server option BootPServerName string `env:"sname" json:"bootp_server_name,omitempty"` // The bootp server name option BootPFile string `env:"boot_file" json:"bootp_file,omitempty"` // The bootp boot file option Timezone string `env:"timezone" json:"timezone,omitempty"` // Offset in seconds from UTC Routers []net.IP `env:"router" json:"routers,omitempty"` // A list of routers DNS []net.IP `env:"dns" json:"dns_servers,omitempty"` // A list of DNS servers NTPServers []net.IP `env:"ntpsrv" json:"ntp_servers,omitempty"` // A list of NTP servers LPRServers []net.IP `env:"lprsvr" json:"lpr_servers,omitempty"` // A list of LPR servers TimeServers []net.IP `env:"timesvr" json:"_time_servers,omitempty"` // A list of time servers (obsolete) IEN116NameServers []net.IP `env:"namesvr" json:"_name_servers,omitempty"` // A list of IEN 116 name servers (obsolete) LogServers []net.IP `env:"logsvr" json:"_log_servers,omitempty"` // A list of MIT-LCS UDP log servers (obsolete) CookieServers []net.IP `env:"cookiesvr" json:"_cookie_servers,omitempty"` // A list of RFC 865 cookie servers (obsolete) WINSServers []net.IP `env:"wins" json:"_wins_servers,omitempty"` // A list of WINS servers SwapServer net.IP `env:"swapsvr" json:"_swap_server,omitempty"` // The IP address of the client's swap server BootSize int `env:"bootsize" json:"bootsize,omitempty"` // The length in 512 octect blocks of the bootfile RootPath string `env:"rootpath" json:"root_path,omitempty"` // The path name of the client's root disk LeaseTime time.Duration `env:"lease" json:"lease,omitempty"` // The lease time, in seconds DHCPType string `env:"dhcptype" json:"dhcp_type,omitempty"` // DHCP message type (safely ignored) ServerID string `env:"serverid" json:"server_id,omitempty"` // The IP of the server Message string `env:"message" json:"reason,omitempty"` // Reason for a DHCPNAK TFTPServerName string `env:"tftp" json:"tftp,omitempty"` // The TFTP server name BootFileName string `env:"bootfile" json:"bootfile,omitempty"` // The boot file name isEmpty map[string]bool } func (l *Lease) setIsEmpty(m map[string]bool) { l.isEmpty = m } func (l *Lease) IsEmpty(key string) bool { return l.isEmpty[key] } func (l *Lease) ToJSON() string { json, err := json.Marshal(l) if err != nil { return "" } return string(json) } func UnmarshalDHCPCLease(lease *Lease, str string) error { // parse the lease file as a map data := make(map[string]string) for _, line := range strings.Split(str, "\n") { line = strings.TrimSpace(line) // skip empty lines and comments if line == "" || strings.HasPrefix(line, "#") { continue } parts := strings.SplitN(line, "=", 2) if len(parts) != 2 { log.Printf("invalid line: %s", line) continue } key := strings.TrimSpace(parts[0]) value := strings.TrimSpace(parts[1]) data[key] = value } // now iterate over the lease struct and set the values leaseType := reflect.TypeOf(lease).Elem() leaseValue := reflect.ValueOf(lease).Elem() valuesParsed := make(map[string]bool) for i := 0; i < leaseType.NumField(); i++ { field := leaseValue.Field(i) // get the env tag key := leaseType.Field(i).Tag.Get("env") if key == "" { continue } valuesParsed[key] = false // get the value from the data map value, ok := data[key] if !ok || value == "" { continue } switch field.Interface().(type) { case string: field.SetString(value) case int: val, err := strconv.Atoi(value) if err != nil { continue } field.SetInt(int64(val)) case time.Duration: val, err := time.ParseDuration(value + "s") if err != nil { continue } field.Set(reflect.ValueOf(val)) case net.IP: ip := net.ParseIP(value) if ip == nil { continue } field.Set(reflect.ValueOf(ip)) case []net.IP: val := make([]net.IP, 0) for _, ipStr := range strings.Fields(value) { ip := net.ParseIP(ipStr) if ip == nil { continue } val = append(val, ip) } field.Set(reflect.ValueOf(val)) default: return fmt.Errorf("unsupported field `%s` type: %s", key, field.Type().String()) } valuesParsed[key] = true } lease.setIsEmpty(valuesParsed) return nil }