dnsleapsecs

README

Leap-seconds via DNS

http://phk.freebsd.dk/time/20151122/

Documentation

Overview

Package dnsleapsecs provides functionality for quering leap-seconds via DNS using an IPv4 encoding.

See for more information: http://phk.freebsd.dk/time/20151122/ For reference and manual checks search for "IERS Bulletin C" (leap second announcements).

Index

• Variables
• type Error
  • func (e *Error) Error() string
  • func (e *Error) Unwrap() error
• type Resolver
• type Result
  • func Decode(ip string) (Result, error)
  • func Fetch(ctx context.Context) (string, Result, error)
  • func Lookup(ctx context.Context, r Resolver) (string, Result, error)
  • func LookupHost(ctx context.Context, r Resolver, host string) (string, Result, error)

Variables

var TestVectors = []struct {
	IP     string
	Result Result
	Err    *Error
}{
	{"240.3.9.77", Result{1971, 12, 9, +1}, nil},
	{"240.15.10.108", Result{1972, 6, 10, +1}, nil},
	{"242.18.28.160", Result{1993, 12, 28, 0}, nil},
	{"255.76.200.237", Result{2135, 1, 72, -1}, nil},
	{"127.240.133.76", Result{0, 0, 0, 0}, &Error{Code: -1}},
	{"255.209.76.40", Result{0, 0, 0, 0}, &Error{Code: -2}},
	{"241.179.152.73", Result{0, 0, 0, 0}, &Error{Code: -3}},
}

TestVectors is test data to validate the decode logic.

Types

type Error

type Error struct {
	Code int
	Err  error
}

Error is the error type returned.

func (*Error) Error

func (e *Error) Error() string

func (*Error) Unwrap

func (e *Error) Unwrap() error

type Resolver

type Resolver interface {
	LookupHost(ctx context.Context, host string) (addrs []string, err error)
}

Resolver resolves DNS host records.

type Result

type Result struct {
	// Announced horizon.
	Year, Month int

	// DTAI is what to subtract from TAI to get UTC until that month ends.
	DTAI int // dTAI

	// Delta is what needs to be applied to DTAI at the end of that month.
	Delta int
}

Result contains leap-second information.

func Decode

func Decode(ip string) (Result, error)

Decode decodes leap-second information in a numeric IPv4 string ("253.253.100.11").

year and month is the announced horizon. dtai is what you subtract from TAI to get UTC until that month ends. delta is what you do to dtai at the end of that month.

func Fetch

func Fetch(ctx context.Context) (string, Result, error)

Fetch fetches and decodes leap-second information, using net.DefaultResolver and "leapsecond.utcd.org". Additionally the raw IPv4 address is returned as well.

In the unlikely case there is more than a single result, first successfully parsed address is used.

func Lookup

func Lookup(ctx context.Context, r Resolver) (string, Result, error)

Lookup fetches and parses the leap-second information, using the "leapsecond.utcd.org" host record. Additionally the raw IPv4 address is returned as well.

In the unlikely case there is more than a single result, first successfully parsed address is used.

func LookupHost

func LookupHost(ctx context.Context, r Resolver, host string) (string, Result, error)

LookupHost fetches and parses the leap-second information. Additionally the raw IPv4 address is returned as well.

In the unlikely case there is more than a single result, first successfully parsed address is used.