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package getter
import (
"encoding/binary"
"errors"
"log"
"net"
"time"
)
const (
InfoColor = "\033[1;34m%s\033[0m"
NoticeColor = "\033[1;36m%s\033[0m"
WarningColor = "\033[1;33m%s\033[0m"
ErrorColor = "\033[1;31m%s\033[0m"
DebugColor = "\033[0;36m%s\033[0m"
)
const (
LI_NO_WARNING = 0
LI_ALARM_CONDITION = 3
VN_FIRST = 1
VN_LAST = 4
MODE_CLIENT = 3
FROM_1900_TO_1970 = 2208988800
)
func Serve(req []byte, addr net.Addr) ([]byte, error) {
if validFormat(req) {
res := generate(req, addr)
return res, nil
}
return []byte{}, errors.New("invalid format.")
}
func validFormat(req []byte) bool {
var l = req[0] >> 6
var v = (req[0] << 2) >> 5
var m = (req[0] << 5) >> 5
if (l == LI_NO_WARNING) || (l == LI_ALARM_CONDITION) {
if (v >= VN_FIRST) && (v <= VN_LAST) {
if m == MODE_CLIENT {
return true
}
}
}
return false
}
func unix2ntp(u int64) int64 {
return u + FROM_1900_TO_1970
}
func ntp2unix(n int64) int64 {
return n - FROM_1900_TO_1970
}
func int2bytes(i int64) []byte {
var b = make([]byte, 4)
h1 := i >> 24
h2 := (i >> 16) - (h1 << 8)
h3 := (i >> 8) - (h1 << 16) - (h2 << 8)
h4 := byte(i)
b[0] = byte(h1)
b[1] = byte(h2)
b[2] = byte(h3)
b[3] = byte(h4)
return b
}
func NTPPickup(upntp []string, ClientIP net.Addr) time.Time {
for _, addr := range upntp {
log.Println("\033[1;34mrequest\033[0m ---> asking for time from", ClientIP)
log.Println("\033[1;36maccess\033[0m ----> trying to ntp server:", addr)
custom, err := ntpaccessclient(addr)
if err == nil {
log.Println("\033[1;32msuccess\033[0m ---> time received from:", addr)
log.Println("\033[1;32mresponse\033[0m --> answering to the client", ClientIP)
return custom
}
log.Printf("\033[1;31merror\033[0m -----> ntp address: %v (%v)\n", addr, err)
}
log.Println("\033[1;31merror\033[0m -----> can not get anything from ntp servers!")
log.Println("\033[1;33mwarining\033[0m --> passing system time to client (might be wrong!)")
return time.Now()
}
var ArgNTP []string
func generate(req []byte, addr net.Addr) []byte {
custom := NTPPickup(ArgNTP, addr)
var second = unix2ntp(custom.Unix())
var fraction = unix2ntp(int64(custom.Nanosecond()))
var res = make([]byte, 48)
var vn = req[0] & 0x38
res[0] = vn + 4
res[1] = 1
res[2] = req[2]
res[3] = 0xEC
res[12] = 0x4E
res[13] = 0x49
res[14] = 0x43
res[15] = 0x54
copy(res[16:20], int2bytes(second)[0:])
copy(res[24:32], req[40:48])
copy(res[32:36], int2bytes(second)[0:])
copy(res[36:40], int2bytes(fraction)[0:])
copy(res[40:48], res[32:40])
return res
}
type mode byte
const (
reserved mode = 0 + iota
symmetricActive
symmetricPassive
client
server
broadcast
controlMessage
reservedPrivate
)
type ntpTime struct {
Seconds uint32
Fraction uint32
}
func (t ntpTime) UTC() time.Time {
nsec := uint64(t.Seconds)*1e9 + (uint64(t.Fraction) * 1e9 >> 32)
return time.Date(1900, 1, 1, 0, 0, 0, 0, time.UTC).Add(time.Duration(nsec))
}
type msg struct {
LiVnMode byte
Stratum byte
Poll byte
Precision byte
RootDelay uint32
RootDispersion uint32
ReferenceId uint32
ReferenceTime ntpTime
OriginTime ntpTime
ReceiveTime ntpTime
TransmitTime ntpTime
}
func (m *msg) SetVersion(v byte) {
m.LiVnMode = (m.LiVnMode & 0xc7) | v<<3
}
func (m *msg) SetMode(md mode) {
m.LiVnMode = (m.LiVnMode & 0xf8) | byte(md)
}
func ntpaccessclient(host string) (time.Time, error) {
raddr, err := net.ResolveUDPAddr("udp", host)
if err != nil {
return time.Now(), err
}
con, err := net.DialUDP("udp", nil, raddr)
if err != nil {
return time.Now(), err
}
defer con.Close()
con.SetDeadline(time.Now().Add(5 * time.Second))
m := new(msg)
m.SetMode(client)
m.SetVersion(4)
err = binary.Write(con, binary.BigEndian, m)
if err != nil {
return time.Now(), err
}
err = binary.Read(con, binary.BigEndian, m)
if err != nil {
return time.Now(), err
}
t := m.ReceiveTime.UTC().Local()
return t, nil
}
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