/ip.go
Go | 440 lines | 311 code | 40 blank | 89 comment | 107 complexity | 73c0e3e131135809618a9ea37225c3a5 MD5 | raw file
Possible License(s): GPL-2.0
- // 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 main
- // 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
- }
- // IPv4Mask returns the IP mask (in 16-byte form) of the
- // IPv4 mask a.b.c.d.
- func IPv4Mask(a, b, c, d byte) IPMask {
- p := make(IPMask, IPv6len)
- for i := 0; i < 12; i++ {
- p[i] = 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 = IPv4Mask(0xff, 0, 0, 0)
- classBMask = IPv4Mask(0xff, 0xff, 0, 0)
- classCMask = IPv4Mask(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 n int
- for i, v := range mask {
- if v == 0xff {
- n += 8
- continue
- }
- // found non-ff byte
- // count 1 bits
- for v&0x80 != 0 {
- n++
- v <<= 1
- }
- // rest must be 0 bits
- if v != 0 {
- return -1
- }
- for i++; i < len(mask); i++ {
- if mask[i] != 0 {
- return -1
- }
- }
- break
- }
- 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 >= 12*8 {
- return itod(uint(n - 12*8))
- }
- }
- 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)
- }