ntp

package
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 Go to latest Published: Apr 15, 2026 License: BSD-3-Clause Imports: 5 Imported by: 0

Documentation

Overview

package ntp implements the NTP protocol as described in RFC 5905.

Index

Constants

View Source 
const (
	SizeHeader = 48
	ClientPort = 1023 // Typical Client port number.
	ServerPort = 123  // NTP server port number
	Version4   = 4    // Current NTP Version Number
	MinPoll    = 4    // Minimum poll exponent (16s)
	MaxPoll    = 17   // Maximum poll exponent (~36h)
	MaxDisp    = 16   // Maximum dispersion (16s)
	MaxDist    = 1    // Distance threshold (1s)
	MaxStratum = 16   // Maximum stratum
	MinDispDiv = 200  // Minimum dispersion divisor 1/(200) == 0.005
)

NTP Global Parameters.

Variables

This section is empty.

Functions

func BaseTime 

func BaseTime() time.Time

BaseTime returnsS the time that corresponds to the NTP base time. The zero value for Timestamp and Date types corresponds to this time.

func CalculateSystemPrecision 

func CalculateSystemPrecision(nowNano func() int64, iters []int64) int8

CalculateSystemPrecision calculates the NTP system precision for a time source. If the time source is nil the default static call to time.Now->[time.Time.UnixNano] is used.

Types

type Client 

type Client struct {
	// contains filtered or unexported fields
}

func (*Client) ConnectionID 

func (c *Client) ConnectionID() *uint64

func (*Client) Demux 

func (c *Client) Demux(carrierData []byte, frameOffset int) error

func (*Client) Encapsulate 

func (c *Client) Encapsulate(carrierData []byte, offsetToIP, offsetToFrame int) (int, error)

func (*Client) IsDone 

func (c *Client) IsDone() bool

func (*Client) LocalPort 

func (c *Client) LocalPort() uint16

func (*Client) Now 

func (c *Client) Now() time.Time

Now returns the current time as corrected by NTP protocol.

func (*Client) Offset 

func (c *Client) Offset() time.Duration

Offset is a helper method to determine the difference between the Client's clock and the server's clock. Use Client.Now to calculate the server's time.

func (*Client) OffsetUnsynced 

func (c *Client) OffsetUnsynced() time.Duration

OffsetUnsynced returns the absolute time offset difference between client and server clock as calculated by the clock synchonization algorithm. It is unsynchonized- the result of OffsetUnsynced will not change with time.

func (*Client) Protocol 

func (c *Client) Protocol() uint64

func (*Client) Reset 

func (c *Client) Reset(sysprec int8, now func() time.Time)

func (*Client) RoundTripDelay 

func (c *Client) RoundTripDelay() time.Duration

func (*Client) ServerStratum 

func (c *Client) ServerStratum() Stratum

ServerStratum returns the stratum of the server client synchronized with.

type Date 

type Date struct {
	// contains filtered or unexported fields
}

The 128-bit date format is used where sufficient storage and word size are available. It includes a 64-bit signed seconds field spanning 584 billion years and a 64-bit fraction field resolving .05 attosecond (i.e., 0.5e-18).

func (Date) Time 

func (d Date) Time() (time.Time, error)

type Frame 

type Frame struct {
	// contains filtered or unexported fields
}

Frame encapsulates the raw data of an NTP packet and provides methods for manipulating, validating and retrieving fields and payload data. See RFC5905.

func NewFrame 

func NewFrame(buf []byte) (Frame, error)

func (Frame) ClearHeader 

func (frm Frame) ClearHeader()

ClearHeader zeros out the header contents.

func (Frame) Flags 

func (frm Frame) Flags() (mode Mode, version uint8, lp LeapIndicator)

func (Frame) OriginTime 

func (frm Frame) OriginTime() Timestamp

OriginTime is time at the client when the request departed for the server, in NTP timestamp format.

func (Frame) Poll 

func (frm Frame) Poll() int8

Poll is 8-bit signed integer representing the maximum interval between successive messages, in log2 seconds. Suggested default limits for minimum and maximum poll intervals are 6 and 10, respectively.

func (Frame) Precision 

func (frm Frame) Precision() int8

Precision is 8-bit signed integer representing the precision of the system clock, in log2 seconds. For instance, a value of -18 corresponds to a precision of about one microsecond. The precision can be determined when the service first starts up as the minimum time of several iterations to read the system clock.

func (Frame) ReceiveTime 

func (frm Frame) ReceiveTime() Timestamp

ReceiveTime time at the server when the request arrived from the client, in NTP timestamp format.

func (Frame) ReferenceID 

func (frm Frame) ReferenceID() *[4]byte

32-bit code identifying the particular server or reference clock. The interpretation depends on the value in the stratum field. For packet stratum 0 (unspecified or invalid), this is a four-character ASCII [RFC1345] string, called the "kiss code", used for debugging and monitoring purposes. For stratum 1 (reference clock), this is a four-octet, left-justified, zero-padded ASCII string assigned to the reference clock. The authoritative list of Reference Identifiers is maintained by IANA; however, any string beginning with the ASCII character "X" is reserved for unregistered experimentation and development.

func (Frame) ReferenceTime 

func (frm Frame) ReferenceTime() Timestamp

ReferenceTime is when the system clock was last set or corrected, in NTP timestamp format.

func (Frame) RootDelay 

func (frm Frame) RootDelay() Short

Total round-trip delay to the reference clock, in NTP short format.

func (Frame) RootDispersion 

func (frm Frame) RootDispersion() Short

Total dispersion to the reference clock, in NTP short format.

func (Frame) SetFlags 

func (frm Frame) SetFlags(mode Mode, version uint8, lp LeapIndicator)

func (Frame) SetOriginTime 

func (frm Frame) SetOriginTime(ot Timestamp)

func (Frame) SetPoll 

func (frm Frame) SetPoll(Poll int8)

func (Frame) SetPrecision 

func (frm Frame) SetPrecision(Precision int8)

func (Frame) SetReceiveTime 

func (frm Frame) SetReceiveTime(rt Timestamp)

func (Frame) SetReferenceTime 

func (frm Frame) SetReferenceTime(rt Timestamp)

func (Frame) SetRootDelay 

func (frm Frame) SetRootDelay(rd Short)

func (Frame) SetRootDispersion 

func (frm Frame) SetRootDispersion(rd Short)

func (Frame) SetStratum 

func (frm Frame) SetStratum(stratum Stratum)

func (Frame) SetTransmitTime 

func (frm Frame) SetTransmitTime(rt Timestamp)

func (Frame) Stratum 

func (frm Frame) Stratum() Stratum

func (Frame) TransmitTime 

func (frm Frame) TransmitTime() Timestamp

TransmitTime at the server when the response left for the client, in NTP timestamp format.

type LeapIndicator 

type LeapIndicator uint8

LeapIndicator represents the leap second indicator. It indicates whether there is no warning, an extra second (61 seconds in the last minute), or a missing second (59 seconds in the last minute). 

const (
	LeapNoWarning    LeapIndicator = iota // no warning
	LeapLastMinute61                      // last minute 61
	LeapLastMinute59                      // last minute 59
)

type Mode 

type Mode uint8

Mode represents the mode of the NTP message. It can be undefined, symmetric active, symmetric passive, client, server, broadcast, NTP control message, or private use. 

const (
	ModeSymmetricActive   Mode // symmetric active
	ModeSymmetricPassive       // symmetric passive
	ModeClient                 // client
	ModeServer                 // server
	ModeBroadcast              // broadcast
	ModeNTPControlMessage      // control message
	ModePrivateUse             // private use
)

type Short 

type Short uint32

func (Short) Fractions 

func (t Short) Fractions() uint16

func (Short) Seconds 

func (t Short) Seconds() uint16

type Stratum 

type Stratum uint8

Stratum represents the stratum level of the NTP server. 

const (
	// If the Stratum field is 0, which implies unspecified or invalid, the
	// Reference Identifier field can be used to convey messages useful for
	// status reporting and access control.  These are called Kiss-o'-Death
	// (KoD) packets and the ASCII messages they convey are called kiss codes.
	StratumUnspecified Stratum = 0  // unspecified
	StratumPrimary     Stratum = 1  // primary
	StratumUnsync      Stratum = 16 // unsynchronized
)

func (Stratum) IsSecondary 

func (s Stratum) IsSecondary() bool

func (Stratum) String 

func (s Stratum) String() string

String returns a human readable representation of the Stratum.

type Timestamp 

type Timestamp struct {
	// contains filtered or unexported fields
}

Timestamp format is used in packet headers and other places with limited word size. It includes a 32-bit unsigned seconds field spanning 136 years and a 32-bit fraction field resolving 232 picoseconds. The 32-bit short format is used in delay and dispersion header fields where the full resolution and range of the other formats are not justified. It includes a 16-bit unsigned seconds field and a 16-bit fraction field.

func TimestampFromTime 

func TimestampFromTime(t time.Time) (Timestamp, error)

func TimestampFromUint64 

func TimestampFromUint64(ts uint64) Timestamp

func (Timestamp) Add 

func (t Timestamp) Add(d time.Duration) Timestamp

func (Timestamp) Fractions 

func (t Timestamp) Fractions() uint32

func (Timestamp) IsZero 

func (t Timestamp) IsZero() bool

IsZero reports whether t represents the zero time instant.

func (Timestamp) Put 

func (t Timestamp) Put(b []byte)

func (Timestamp) Seconds 

func (t Timestamp) Seconds() uint32

func (Timestamp) Sub 

func (t Timestamp) Sub(v Timestamp) time.Duration

func (Timestamp) Time 

func (t Timestamp) Time() time.Time

Source Files

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