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NTP服务器【Network Time Protocol#xff08;NTP#xff09;】是用来使计算机时间同步化的一种协议。
应用场景说明 为了确保封闭局域网内多个服务器的时间同步#xff0c;我们计划部署一个网络时间同步服务器#xff08;NTP服务器#xff09;。这一角色将…NTP服务介绍
NTP服务器【Network Time ProtocolNTP】是用来使计算机时间同步化的一种协议。
应用场景说明 为了确保封闭局域网内多个服务器的时间同步我们计划部署一个网络时间同步服务器NTP服务器。这一角色将由一台个人笔记本电脑承担该笔记本将连接到局域网中并以其当前时间为基准。我们将利用这台笔记本电脑作为NTP服务器对局域网内的多个运行CentOS 8的服务器进行时间校准以保证系统时间的一致性和准确性。
NTP协议
NTP通信协议的传输层协议是UDPNTP通信协议的应用层协议是NTP
NTP报文说明
NTP的报文是48字节
第1个字节可以理解为简易的报文头这8个bit包含Leap Indicator、NTP Version、Mode a LI 占用2个bit b VN 占用3个bit笔者编写的服务器设置为版本v4.0 c Mode 占用3个bitntp server时为4ntp client时为3第2个字节为 Peer Clock Stratum第3个字节为 Peer Polling Interval第4个字节为 Peer Clock Precision第5 - 8字节为 Root Delay第9 - 12字节为 Root Dispersion第13- 16字节为 Reference Identifier第17 - 24字节为 Reference Timestamp 参考时间戳第25 - 32字节为 Originate Timestamp 起始时间戳第33 - 40字节为 Receive Timestamp 接收时间戳第 41 - 48字节 Transmit Timestamp 传输时间戳
根据NTP报文编码实现Go语言的结构体
type NtpPacket struct {/*LI: 2bit 00 Leap Indicator(0)VN: 3bit 100 NTP Version(4)Mode: 3bit 100 Mode: server(4), client(3)*/Header uint8 // 报文头: 包含LI、VN、ModeStratum uint8 // Peer Clock Stratum: primary reference (1)Poll uint8 // Peer Polling Interval: invalid (0)Precision uint8 // Peer Clock Precision: 0.000000 secondsRootDelay uint32 // Root DelayRootDisp uint32 // Root DispersionRefID uint32 // Reference IdentifierRefTS uint64 // Reference Timestamp 参考时间戳OrigTS uint64 // Originate Timestamp 起始时间戳RecvTS uint64 // Receive Timestamp 接收时间戳TransTS uint64 // Transmit Timestamp 传输时间戳
}NTP服务器的源码
ntpsrv.go
package mainimport (hldlog NTPServer/log4goencoding/binaryfmtlognetsynctime
)const (STANDARD_PACKET_SIZE 48 // 标准NTP的报文大小
)type NTPServer struct {srvAddress stringconn *net.UDPConnwait sync.WaitGroupntpPack NtpPacket // NTP协议报文requestCount uint64 // 请求计数
}type NtpPacket struct {/*LI: 2bit 00 Leap Indicator(0)VN: 3bit 100 NTP Version(4)Mode: 3bit 100 Mode: server(4), client(3)*/Header uint8 // 报文头: 包含LI、VN、ModeStratum uint8 // Peer Clock Stratum: primary reference (1)Poll uint8 // Peer Polling Interval: invalid (0)Precision uint8 // Peer Clock Precision: 0.000000 secondsRootDelay uint32 // Root DelayRootDisp uint32 // Root DispersionRefID uint32 // Reference IdentifierRefTS uint64 // Reference Timestamp 参考时间戳OrigTS uint64 // Originate Timestamp 起始时间戳RecvTS uint64 // Receive Timestamp 接收时间戳TransTS uint64 // Transmit Timestamp 传输时间戳
}func (srv *NTPServer) NewNtpPacket() *NtpPacket {// 初始化Header字段header : uint8(0)header | (0 6) // LI: 2bit 00header | (4 3) // VN: 3bit 100header | (4 0) // Mode: 3bit 100// 创建新的NtpPacket实例packet : NtpPacket{Header: header,Stratum: 0x01,Poll: 0x00,Precision: 0x00,RootDelay: 0,RootDisp: 0,RefID: 0,RefTS: 0,OrigTS: 0,RecvTS: 0,TransTS: 0,}return packet
}func (pack *NtpPacket) SetTimestamp(timestamp time.Time, field string) {ntpTime : ToNTPTime(timestamp)switch field {case RefTS:pack.RefTS ntpTimecase OrigTS:pack.OrigTS ntpTimecase RecvTS:pack.RecvTS ntpTimecase TransTS:pack.TransTS ntpTime}
}// toNTPTime 将Unix时间转换为NTP时间
func ToNTPTime(t time.Time) uint64 {seconds : uint32(t.Unix()) 2208988800 // NTP时间从1900年开始计算fraction : uint32(float64(t.Nanosecond()) * (1 32) / 1e9)return uint64(seconds)32 | uint64(fraction)
}func NewNTPServer(srvAddr string) *NTPServer {return NTPServer{srvAddress: srvAddr}
}// 启动NTP服务器
func (srv *NTPServer) Start() error {addr, err : net.ResolveUDPAddr(udp, srv.srvAddress)if err ! nil {return err}hldlog.Info(fmt.Sprintf(%s:%d, addr.IP.String(), addr.Port))conn, err : net.ListenUDP(udp, addr)if err ! nil {return err}srv.wait.Add(1)srv.conn conngo RecvMsg(srv)return nil
}// 关闭NTP服务器
func (srv *NTPServer) Stop() {srv.conn.Close()srv.wait.Wait()
}// 接收数据
func RecvMsg(srv *NTPServer) {defer srv.wait.Done()buffer : make([]byte, 2*1024)for {n, remoteAddr, err : srv.conn.ReadFromUDP(buffer[0:])if err ! nil {fmt.Println(ReadFromUDP error:, err)return}hldlog.Info(fmt.Sprintf([Recv] %d bytes from %s, n, remoteAddr.String()))if n ! STANDARD_PACKET_SIZE {continue}// 接收到NTP客户端消息的时间recvMsgTime : time.Now().UTC()recvHexString : BytesToHex(buffer[:n])hldlog.Info(fmt.Sprintf([Recv] %s, recvHexString))udpPacket, err : ParseUDPPacket(buffer[:n])if err ! nil {log.Printf(Error parsing UDP packet: %v, err)continue}ntpPack : srv.NewNtpPacket()ntpPack.SetTimestamp(time.Now().UTC(), RefTS)ntpPack.OrigTS udpPacket.TransTSntpPack.SetTimestamp(recvMsgTime, RecvTS)ntpPack.SetTimestamp(time.Now().UTC(), TransTS)sendPacket : ntpPack.Serialize()sendLen, err : srv.conn.WriteToUDP(sendPacket, remoteAddr)if err ! nil {log.Println(err.Error())continue}if sendLen 0 {hldlog.Info(fmt.Sprintf([Send] %s, BytesToHex(sendPacket)))}srv.requestCount}
}func (pack *NtpPacket) Serialize() []byte {packet : make([]byte, 48)// binary.BigEndian.PutUint32(packet[0:4], pack.Header)packet[0] pack.Headerpacket[1] pack.Stratumpacket[2] pack.Pollpacket[3] pack.Precisionbinary.BigEndian.PutUint32(packet[4:8], pack.RootDelay)binary.BigEndian.PutUint32(packet[8:12], pack.RootDisp)binary.BigEndian.PutUint32(packet[12:16], pack.RefID)binary.BigEndian.PutUint64(packet[16:24], pack.RefTS)binary.BigEndian.PutUint64(packet[24:32], pack.OrigTS)binary.BigEndian.PutUint64(packet[32:40], pack.RecvTS)binary.BigEndian.PutUint64(packet[40:48], pack.TransTS)return packet
}// BytesToHex 将字节数组转换为16进制字符串
func BytesToHex(data []byte) string {hexString : make([]byte, 3*len(data)-1)for i, b : range data {high : 0123456789ABCDEF[(b 4)]low : 0123456789ABCDEF[(b 0x0F)]hexString[i*3] highhexString[i*31] lowif i len(data)-1 {hexString[i*32] // 每个16进制数据之间加空格}}return string(hexString)
}func ParseUDPPacket(buf []byte) (*NtpPacket, error) {if len(buf) STANDARD_PACKET_SIZE { // 最小有效长度为48字节return nil, fmt.Errorf(Invalid UDP packet length: %d, len(buf))}packet : NtpPacket{// Header: binary.BigEndian.Uint32(buf[0:4]),Header: buf[0],Stratum: buf[1],Poll: buf[2],Precision: buf[3],RootDelay: binary.BigEndian.Uint32(buf[4:8]),RootDisp: binary.BigEndian.Uint32(buf[8:12]),RefID: binary.BigEndian.Uint32(buf[12:16]),RefTS: binary.BigEndian.Uint64(buf[16:24]),OrigTS: binary.BigEndian.Uint64(buf[24:32]),RecvTS: binary.BigEndian.Uint64(buf[32:40]),TransTS: binary.BigEndian.Uint64(buf[40:48]),}return packet, nil
}main.go
package mainimport (hldlog NTPServer/log4gofmtgopkg.in/ini.v1time
)type NetAddr struct {IP stringPort string
}var LocalHost NetAddr{IP: 0.0.0.0, Port: 60123}func loadConfig() (NetAddr, error) {// 读取INI配置文件iniConf, err : ini.Load(./config/config.ini)if err ! nil {hldlog.Error(fmt.Sprintf(Fail to read INI file: %v, err))return LocalHost, nil}iniSection : iniConf.Section(LocalHost)return NetAddr{IP: iniSection.Key(ip).String(),Port: iniSection.Key(port).String(),}, nil
}// 初始化log4go日志库
func init() {hldlog.LoadConfiguration(./config/log.xml, xml)
}func main() {hldlog.Info(NTP SERVER Start(48 Bytes))LocalHost, err : loadConfig()if err ! nil {hldlog.Error(fmt.Sprintf(Failed to load configuration: %v, err))}ntpSrv : NewNTPServer(fmt.Sprintf(%s:%s, LocalHost.IP, LocalHost.Port))ntpSrv.Start()for {time.Sleep(60 * time.Second)}
}代码细节说明 NTP服务器在回复NTP客户端的消息中其中OrigTS uint64Originate Timestamp 起始时间戳必须是NTP客户端发送来的TransTS uint64Transmit Timestamp 传输时间戳。
验证GoNTPSrv
上述实现的NTP服务已经过Go语言中开源的NTP Client库 https://github.com/beevik/ntp 验证。 UDP数据包
# 客户端发送的数据
23 00 00 20 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 39 1C 79 9E 83 D3 D5 82# 服务器返回的数据
24 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 EA D9 CF EE AD 4D DC 2B 39 1C 79 9E 83 D3 D5 82 EA D9 CF EE AD 4D DC 2B EA D9 CF EE AD 4D DC 2BNTP Client的简单源码
package mainimport (hldlog NTPCli/log4gofmtlogosos/exectimegithub.com/beevik/ntpgopkg.in/ini.v1
)type NetAddr struct {IP stringPort int
}var RemoteAddr NetAddr{IP: 0.0.0.0, Port: 60123}func init() {hldlog.LoadConfiguration(./config/log.xml, xml)
}func main() {hldlog.Info(NTP CLIENT Start)currTime : time.Now()formattedTime : currTime.Format(2006-01-02 15:04:05.000)hldlog.Info(formattedTime)// 读取INI配置文件iniConf, err : ini.Load(./config/config.ini)if err ! nil {log.Fatalf(Fail to read INI file: %v, err)}remoteSection : iniConf.Section(NTP_SERVER)RemoteAddr.IP remoteSection.Key(ip).String()RemoteAddr.Port, _ remoteSection.Key(port).Int()hldlog.Info(fmt.Sprintf(ntp://%s:%d, RemoteAddr.IP, RemoteAddr.Port))// edu.ntp.org.cn// resp, err : ntp.Time(edu.ntp.org.cn)resp, err : ntp.Time(fmt.Sprintf(%s:%d, RemoteAddr.IP, RemoteAddr.Port))if err ! nil {hldlog.Error(fmt.Sprintf(%v, err))os.Exit(-1)}hldlog.Info(resp.String())localTime : resp.Local()hldlog.Info(localTime.Format(2006-01-02 15:04:05.000))// setTime(localTime)for {time.Sleep(60 * time.Second)}
}
