package udhcpc
import (
"bufio"
"encoding/json"
"fmt"
"net"
"os"
"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
Uptime time.Duration `env:"uptime" json:"uptime,omitempty"` // The uptime of the device when the lease was obtained, in seconds
LeaseExpiry *time.Time `json:"lease_expiry,omitempty"` // The expiry time of the lease
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 (l *Lease) SetLeaseExpiry() (time.Time, error) {
if l.Uptime == 0 || l.LeaseTime == 0 {
return time.Time{}, fmt.Errorf("uptime or lease time isn't set")
}
// get the uptime of the device
file, err := os.Open("/proc/uptime")
if err != nil {
return time.Time{}, fmt.Errorf("failed to open uptime file: %w", err)
}
defer file.Close()
var uptime time.Duration
scanner := bufio.NewScanner(file)
for scanner.Scan() {
text := scanner.Text()
parts := strings.Split(text, " ")
uptime, err = time.ParseDuration(parts[0] + "s")
if err != nil {
return time.Time{}, fmt.Errorf("failed to parse uptime: %w", err)
}
}
relativeLeaseRemaining := (l.Uptime + l.LeaseTime) - uptime
leaseExpiry := time.Now().Add(relativeLeaseRemaining)
l.LeaseExpiry = &leaseExpiry
return leaseExpiry, nil
}
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 {
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
}