src/pkg/net/ip.go - go - Git at Google

 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 // IP address manipulations
 //
 // IPv4 addresses are 4 bytes; IPv6 addresses are 16 bytes.
 // An IPv4 address can be converted to an IPv6 address by
 // adding a canonical prefix (10 zeros, 2 0xFFs).
 // This library accepts either size of byte array but always
 // returns 16-byte addresses.

 package net

 // IP address lengths (bytes).
 const (
 	IPv4len = 4
 	IPv6len = 16
 )

 // An IP is a single IP address, an array of bytes.
 // Functions in this package accept either 4-byte (IP v4)
 // or 16-byte (IP v6) arrays as input.  Unless otherwise
 // specified, functions in this package always return
 // IP addresses in 16-byte form using the canonical
 // embedding.
 //
 // Note that in this documentation, referring to an
 // IP address as an IPv4 address or an IPv6 address
 // is a semantic property of the address, not just the
 // length of the byte array: a 16-byte array can still
 // be an IPv4 address.
 type IP []byte

 // An IP mask is an IP address.
 type IPMask []byte

 // IPv4 returns the IP address (in 16-byte form) of the
 // IPv4 address a.b.c.d.
 func IPv4(a, b, c, d byte) IP {
 	p := make(IP, IPv6len)
 	for i := 0; i < 10; i++ {
 		p[i] = 0
 	}
 	p[10] = 0xff
 	p[11] = 0xff
 	p[12] = a
 	p[13] = b
 	p[14] = c
 	p[15] = d
 	return p
 }

 // Well-known IPv4 addresses
 var (
 	IPv4bcast     = IPv4(255, 255, 255, 255) // broadcast
 	IPv4allsys    = IPv4(224, 0, 0, 1)       // all systems
 	IPv4allrouter = IPv4(224, 0, 0, 2)       // all routers
 	IPv4zero      = IPv4(0, 0, 0, 0)         // all zeros
 )

 // Well-known IPv6 addresses
 var (
 	IPzero = make(IP, IPv6len) // all zeros
 )

 // Is p all zeros?
 func isZeros(p IP) bool {
 	for i := 0; i < len(p); i++ {
 		if p[i] != 0 {
 			return false
 		}
 	}
 	return true
 }

 // To4 converts the IPv4 address ip to a 4-byte representation.
 // If ip is not an IPv4 address, To4 returns nil.
 func (ip IP) To4() IP {
 	if len(ip) == IPv4len {
 		return ip
 	}
 	if len(ip) == IPv6len &&
 		isZeros(ip[0:10]) &&
 		ip[10] == 0xff &&
 		ip[11] == 0xff {
 		return ip[12:16]
 	}
 	return nil
 }

 // To16 converts the IP address ip to a 16-byte representation.
 // If ip is not an IP address (it is the wrong length), To16 returns nil.
 func (ip IP) To16() IP {
 	if len(ip) == IPv4len {
 		return IPv4(ip[0], ip[1], ip[2], ip[3])
 	}
 	if len(ip) == IPv6len {
 		return ip
 	}
 	return nil
 }

 // Default route masks for IPv4.
 var (
 	classAMask = IPMask(IPv4(0xff, 0, 0, 0))
 	classBMask = IPMask(IPv4(0xff, 0xff, 0, 0))
 	classCMask = IPMask(IPv4(0xff, 0xff, 0xff, 0))
 )

 // DefaultMask returns the default IP mask for the IP address ip.
 // Only IPv4 addresses have default masks; DefaultMask returns
 // nil if ip is not a valid IPv4 address.
 func (ip IP) DefaultMask() IPMask {
 	if ip = ip.To4(); ip == nil {
 		return nil
 	}
 	switch true {
 	case ip[0] < 0x80:
 		return classAMask
 	case ip[0] < 0xC0:
 		return classBMask
 	default:
 		return classCMask
 	}
 	return nil // not reached
 }

 // Mask returns the result of masking the IP address ip with mask.
 func (ip IP) Mask(mask IPMask) IP {
 	n := len(ip)
 	if n != len(mask) {
 		return nil
 	}
 	out := make(IP, n)
 	for i := 0; i < n; i++ {
 		out[i] = ip[i] & mask[i]
 	}
 	return out
 }

 // Convert i to decimal string.
 func itod(i uint) string {
 	if i == 0 {
 		return "0"
 	}

 	// Assemble decimal in reverse order.
 	var b [32]byte
 	bp := len(b)
 	for ; i > 0; i /= 10 {
 		bp--
 		b[bp] = byte(i%10) + '0'
 	}

 	return string(b[bp:])
 }

 // Convert i to hexadecimal string.
 func itox(i uint) string {
 	if i == 0 {
 		return "0"
 	}

 	// Assemble hexadecimal in reverse order.
 	var b [32]byte
 	bp := len(b)
 	for ; i > 0; i /= 16 {
 		bp--
 		b[bp] = "0123456789abcdef"[byte(i%16)]
 	}

 	return string(b[bp:])
 }

 // String returns the string form of the IP address ip.
 // If the address is an IPv4 address, the string representation
 // is dotted decimal ("74.125.19.99").  Otherwise the representation
 // is IPv6 ("2001:4860:0:2001::68").
 func (ip IP) String() string {
 	p := ip

 	if len(ip) == 0 {
 		return ""
 	}

 	// If IPv4, use dotted notation.
 	if p4 := p.To4(); len(p4) == 4 {
 		return itod(uint(p4[0])) + "." +
 			itod(uint(p4[1])) + "." +
 			itod(uint(p4[2])) + "." +
 			itod(uint(p4[3]))
 	}
 	if len(p) != IPv6len {
 		return "?"
 	}

 	// Find longest run of zeros.
 	e0 := -1
 	e1 := -1
 	for i := 0; i < 16; i += 2 {
 		j := i
 		for j < 16 && p[j] == 0 && p[j+1] == 0 {
 			j += 2
 		}
 		if j > i && j-i > e1-e0 {
 			e0 = i
 			e1 = j
 		}
 	}

 	// Print with possible :: in place of run of zeros
 	var s string
 	for i := 0; i < 16; i += 2 {
 		if i == e0 {
 			s += "::"
 			i = e1
 			if i >= 16 {
 				break
 			}
 		} else if i > 0 {
 			s += ":"
 		}
 		s += itox((uint(p[i]) << 8) | uint(p[i+1]))
 	}
 	return s
 }

 // If mask is a sequence of 1 bits followed by 0 bits,
 // return the number of 1 bits.
 func simpleMaskLength(mask IPMask) int {
 	var i int
 	for i = 0; i < len(mask); i++ {
 		if mask[i] != 0xFF {
 			break
 		}
 	}
 	n := 8 * i
 	v := mask[i]
 	for v&0x80 != 0 {
 		n++
 		v <<= 1
 	}
 	if v != 0 {
 		return -1
 	}
 	for i++; i < len(mask); i++ {
 		if mask[i] != 0 {
 			return -1
 		}
 	}
 	return n
 }

 // String returns the string representation of mask.
 // If the mask is in the canonical form--ones followed by zeros--the
 // string representation is just the decimal number of ones.
 // If the mask is in a non-canonical form, it is formatted
 // as an IP address.
 func (mask IPMask) String() string {
 	switch len(mask) {
 	case 4:
 		n := simpleMaskLength(mask)
 		if n >= 0 {
 			return itod(uint(n + (IPv6len-IPv4len)*8))
 		}
 	case 16:
 		n := simpleMaskLength(mask)
 		if n >= 0 {
 			return itod(uint(n))
 		}
 	}
 	return IP(mask).String()
 }

 // Parse IPv4 address (d.d.d.d).
 func parseIPv4(s string) IP {
 	var p [IPv4len]byte
 	i := 0
 	for j := 0; j < IPv4len; j++ {
 		if i >= len(s) {
 			// Missing octets.
 			return nil
 		}
 		if j > 0 {
 			if s[i] != '.' {
 				return nil
 			}
 			i++
 		}
 		var (
 			n  int
 			ok bool
 		)
 		n, i, ok = dtoi(s, i)
 		if !ok || n > 0xFF {
 			return nil
 		}
 		p[j] = byte(n)
 	}
 	if i != len(s) {
 		return nil
 	}
 	return IPv4(p[0], p[1], p[2], p[3])
 }

 // Parse IPv6 address.  Many forms.
 // The basic form is a sequence of eight colon-separated
 // 16-bit hex numbers separated by colons,
 // as in 0123:4567:89ab:cdef:0123:4567:89ab:cdef.
 // Two exceptions:
 //	* A run of zeros can be replaced with "::".
 //	* The last 32 bits can be in IPv4 form.
 // Thus, ::ffff:1.2.3.4 is the IPv4 address 1.2.3.4.
 func parseIPv6(s string) IP {
 	p := make(IP, 16)
 	ellipsis := -1 // position of ellipsis in p
 	i := 0         // index in string s

 	// Might have leading ellipsis
 	if len(s) >= 2 && s[0] == ':' && s[1] == ':' {
 		ellipsis = 0
 		i = 2
 		// Might be only ellipsis
 		if i == len(s) {
 			return p
 		}
 	}

 	// Loop, parsing hex numbers followed by colon.
 	j := 0
 L: for j < IPv6len {
 		// Hex number.
 		n, i1, ok := xtoi(s, i)
 		if !ok || n > 0xFFFF {
 			return nil
 		}

 		// If followed by dot, might be in trailing IPv4.
 		if i1 < len(s) && s[i1] == '.' {
 			if ellipsis < 0 && j != IPv6len-IPv4len {
 				// Not the right place.
 				return nil
 			}
 			if j+IPv4len > IPv6len {
 				// Not enough room.
 				return nil
 			}
 			p4 := parseIPv4(s[i:])
 			if p4 == nil {
 				return nil
 			}
 			p[j] = p4[12]
 			p[j+1] = p4[13]
 			p[j+2] = p4[14]
 			p[j+3] = p4[15]
 			i = len(s)
 			j += 4
 			break
 		}

 		// Save this 16-bit chunk.
 		p[j] = byte(n >> 8)
 		p[j+1] = byte(n)
 		j += 2

 		// Stop at end of string.
 		i = i1
 		if i == len(s) {
 			break
 		}

 		// Otherwise must be followed by colon and more.
 		if s[i] != ':' && i+1 == len(s) {
 			return nil
 		}
 		i++

 		// Look for ellipsis.
 		if s[i] == ':' {
 			if ellipsis >= 0 { // already have one
 				return nil
 			}
 			ellipsis = j
 			if i++; i == len(s) { // can be at end
 				break
 			}
 		}
 	}

 	// Must have used entire string.
 	if i != len(s) {
 		return nil
 	}

 	// If didn't parse enough, expand ellipsis.
 	if j < IPv6len {
 		if ellipsis < 0 {
 			return nil
 		}
 		n := IPv6len - j
 		for k := j - 1; k >= ellipsis; k-- {
 			p[k+n] = p[k]
 		}
 		for k := ellipsis + n - 1; k >= ellipsis; k-- {
 			p[k] = 0
 		}
 	}
 	return p
 }

 // ParseIP parses s as an IP address, returning the result.
 // The string s can be in dotted decimal ("74.125.19.99")
 // or IPv6 ("2001:4860:0:2001::68") form.
 // If s is not a valid textual representation of an IP address,
 // ParseIP returns nil.
 func ParseIP(s string) IP {
 	p := parseIPv4(s)
 	if p != nil {
 		return p
 	}
 	return parseIPv6(s)
 }
	// Copyright 2009 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	// IP address manipulations
	//
	// IPv4 addresses are 4 bytes; IPv6 addresses are 16 bytes.
	// An IPv4 address can be converted to an IPv6 address by
	// adding a canonical prefix (10 zeros, 2 0xFFs).
	// This library accepts either size of byte array but always
	// returns 16-byte addresses.

	package net

	// IP address lengths (bytes).
	const (
	IPv4len = 4
	IPv6len = 16
	)

	// An IP is a single IP address, an array of bytes.
	// Functions in this package accept either 4-byte (IP v4)
	// or 16-byte (IP v6) arrays as input. Unless otherwise
	// specified, functions in this package always return
	// IP addresses in 16-byte form using the canonical
	// embedding.
	//
	// Note that in this documentation, referring to an
	// IP address as an IPv4 address or an IPv6 address
	// is a semantic property of the address, not just the
	// length of the byte array: a 16-byte array can still
	// be an IPv4 address.
	type IP []byte

	// An IP mask is an IP address.
	type IPMask []byte

	// IPv4 returns the IP address (in 16-byte form) of the
	// IPv4 address a.b.c.d.
	func IPv4(a, b, c, d byte) IP {
	p := make(IP, IPv6len)
	for i := 0; i < 10; i++ {
	p[i] = 0
	}
	p[10] = 0xff
	p[11] = 0xff
	p[12] = a
	p[13] = b
	p[14] = c
	p[15] = d
	return p
	}

	// Well-known IPv4 addresses
	var (
	IPv4bcast = IPv4(255, 255, 255, 255) // broadcast
	IPv4allsys = IPv4(224, 0, 0, 1) // all systems
	IPv4allrouter = IPv4(224, 0, 0, 2) // all routers
	IPv4zero = IPv4(0, 0, 0, 0) // all zeros
	)

	// Well-known IPv6 addresses
	var (
	IPzero = make(IP, IPv6len) // all zeros
	)

	// Is p all zeros?
	func isZeros(p IP) bool {
	for i := 0; i < len(p); i++ {
	if p[i] != 0 {
	return false
	}
	}
	return true
	}

	// To4 converts the IPv4 address ip to a 4-byte representation.
	// If ip is not an IPv4 address, To4 returns nil.
	func (ip IP) To4() IP {
	if len(ip) == IPv4len {
	return ip
	}
	if len(ip) == IPv6len &&
	isZeros(ip[0:10]) &&
	ip[10] == 0xff &&
	ip[11] == 0xff {
	return ip[12:16]
	}
	return nil
	}

	// To16 converts the IP address ip to a 16-byte representation.
	// If ip is not an IP address (it is the wrong length), To16 returns nil.
	func (ip IP) To16() IP {
	if len(ip) == IPv4len {
	return IPv4(ip[0], ip[1], ip[2], ip[3])
	}
	if len(ip) == IPv6len {
	return ip
	}
	return nil
	}

	// Default route masks for IPv4.
	var (
	classAMask = IPMask(IPv4(0xff, 0, 0, 0))
	classBMask = IPMask(IPv4(0xff, 0xff, 0, 0))
	classCMask = IPMask(IPv4(0xff, 0xff, 0xff, 0))
	)

	// DefaultMask returns the default IP mask for the IP address ip.
	// Only IPv4 addresses have default masks; DefaultMask returns
	// nil if ip is not a valid IPv4 address.
	func (ip IP) DefaultMask() IPMask {
	if ip = ip.To4(); ip == nil {
	return nil
	}
	switch true {
	case ip[0] < 0x80:
	return classAMask
	case ip[0] < 0xC0:
	return classBMask
	default:
	return classCMask
	}
	return nil // not reached
	}

	// Mask returns the result of masking the IP address ip with mask.
	func (ip IP) Mask(mask IPMask) IP {
	n := len(ip)
	if n != len(mask) {
	return nil
	}
	out := make(IP, n)
	for i := 0; i < n; i++ {
	out[i] = ip[i] & mask[i]
	}
	return out
	}

	// Convert i to decimal string.
	func itod(i uint) string {
	if i == 0 {
	return "0"
	}

	// Assemble decimal in reverse order.
	var b [32]byte
	bp := len(b)
	for ; i > 0; i /= 10 {
	bp--
	b[bp] = byte(i%10) + '0'
	}

	return string(b[bp:])
	}

	// Convert i to hexadecimal string.
	func itox(i uint) string {
	if i == 0 {
	return "0"
	}

	// Assemble hexadecimal in reverse order.
	var b [32]byte
	bp := len(b)
	for ; i > 0; i /= 16 {
	bp--
	b[bp] = "0123456789abcdef"[byte(i%16)]
	}

	return string(b[bp:])
	}

	// String returns the string form of the IP address ip.
	// If the address is an IPv4 address, the string representation
	// is dotted decimal ("74.125.19.99"). Otherwise the representation
	// is IPv6 ("2001:4860:0:2001::68").
	func (ip IP) String() string {
	p := ip

	if len(ip) == 0 {
	return ""
	}

	// If IPv4, use dotted notation.
	if p4 := p.To4(); len(p4) == 4 {
	return itod(uint(p4[0])) + "." +
	itod(uint(p4[1])) + "." +
	itod(uint(p4[2])) + "." +
	itod(uint(p4[3]))
	}
	if len(p) != IPv6len {
	return "?"
	}

	// Find longest run of zeros.
	e0 := -1
	e1 := -1
	for i := 0; i < 16; i += 2 {
	j := i
	for j < 16 && p[j] == 0 && p[j+1] == 0 {
	j += 2
	}
	if j > i && j-i > e1-e0 {
	e0 = i
	e1 = j
	}
	}

	// Print with possible :: in place of run of zeros
	var s string
	for i := 0; i < 16; i += 2 {
	if i == e0 {
	s += "::"
	i = e1
	if i >= 16 {
	break
	}
	} else if i > 0 {
	s += ":"
	}
	s += itox((uint(p[i]) << 8) \| uint(p[i+1]))
	}
	return s
	}

	// If mask is a sequence of 1 bits followed by 0 bits,
	// return the number of 1 bits.
	func simpleMaskLength(mask IPMask) int {
	var i int
	for i = 0; i < len(mask); i++ {
	if mask[i] != 0xFF {
	break
	}
	}
	n := 8 * i
	v := mask[i]
	for v&0x80 != 0 {
	n++
	v <<= 1
	}
	if v != 0 {
	return -1
	}
	for i++; i < len(mask); i++ {
	if mask[i] != 0 {
	return -1
	}
	}
	return n
	}

	// String returns the string representation of mask.
	// If the mask is in the canonical form--ones followed by zeros--the
	// string representation is just the decimal number of ones.
	// If the mask is in a non-canonical form, it is formatted
	// as an IP address.
	func (mask IPMask) String() string {
	switch len(mask) {
	case 4:
	n := simpleMaskLength(mask)
	if n >= 0 {
	return itod(uint(n + (IPv6len-IPv4len)*8))
	}
	case 16:
	n := simpleMaskLength(mask)
	if n >= 0 {
	return itod(uint(n))
	}
	}
	return IP(mask).String()
	}

	// Parse IPv4 address (d.d.d.d).
	func parseIPv4(s string) IP {
	var p [IPv4len]byte
	i := 0
	for j := 0; j < IPv4len; j++ {
	if i >= len(s) {
	// Missing octets.
	return nil
	}
	if j > 0 {
	if s[i] != '.' {
	return nil
	}
	i++
	}
	var (
	n int
	ok bool
	)
	n, i, ok = dtoi(s, i)
	if !ok \|\| n > 0xFF {
	return nil
	}
	p[j] = byte(n)
	}
	if i != len(s) {
	return nil
	}
	return IPv4(p[0], p[1], p[2], p[3])
	}

	// Parse IPv6 address. Many forms.
	// The basic form is a sequence of eight colon-separated
	// 16-bit hex numbers separated by colons,
	// as in 0123:4567:89ab:cdef:0123:4567:89ab:cdef.
	// Two exceptions:
	// * A run of zeros can be replaced with "::".
	// * The last 32 bits can be in IPv4 form.
	// Thus, ::ffff:1.2.3.4 is the IPv4 address 1.2.3.4.
	func parseIPv6(s string) IP {
	p := make(IP, 16)
	ellipsis := -1 // position of ellipsis in p
	i := 0 // index in string s

	// Might have leading ellipsis
	if len(s) >= 2 && s[0] == ':' && s[1] == ':' {
	ellipsis = 0
	i = 2
	// Might be only ellipsis
	if i == len(s) {
	return p
	}
	}

	// Loop, parsing hex numbers followed by colon.
	j := 0
	L: for j < IPv6len {
	// Hex number.
	n, i1, ok := xtoi(s, i)
	if !ok \|\| n > 0xFFFF {
	return nil
	}

	// If followed by dot, might be in trailing IPv4.
	if i1 < len(s) && s[i1] == '.' {
	if ellipsis < 0 && j != IPv6len-IPv4len {
	// Not the right place.
	return nil
	}
	if j+IPv4len > IPv6len {
	// Not enough room.
	return nil
	}
	p4 := parseIPv4(s[i:])
	if p4 == nil {
	return nil
	}
	p[j] = p4[12]
	p[j+1] = p4[13]
	p[j+2] = p4[14]
	p[j+3] = p4[15]
	i = len(s)
	j += 4
	break
	}

	// Save this 16-bit chunk.
	p[j] = byte(n >> 8)
	p[j+1] = byte(n)
	j += 2

	// Stop at end of string.
	i = i1
	if i == len(s) {
	break
	}

	// Otherwise must be followed by colon and more.
	if s[i] != ':' && i+1 == len(s) {
	return nil
	}
	i++

	// Look for ellipsis.
	if s[i] == ':' {
	if ellipsis >= 0 { // already have one
	return nil
	}
	ellipsis = j
	if i++; i == len(s) { // can be at end
	break
	}
	}
	}

	// Must have used entire string.
	if i != len(s) {
	return nil
	}

	// If didn't parse enough, expand ellipsis.
	if j < IPv6len {
	if ellipsis < 0 {
	return nil
	}
	n := IPv6len - j
	for k := j - 1; k >= ellipsis; k-- {
	p[k+n] = p[k]
	}
	for k := ellipsis + n - 1; k >= ellipsis; k-- {
	p[k] = 0
	}
	}
	return p
	}

	// ParseIP parses s as an IP address, returning the result.
	// The string s can be in dotted decimal ("74.125.19.99")
	// or IPv6 ("2001:4860:0:2001::68") form.
	// If s is not a valid textual representation of an IP address,
	// ParseIP returns nil.
	func ParseIP(s string) IP {
	p := parseIPv4(s)
	if p != nil {
	return p
	}
	return parseIPv6(s)
	}