554 lines
11 KiB
Go
554 lines
11 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// IP address manipulations
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//
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// IPv4 addresses are 4 bytes; IPv6 addresses are 16 bytes.
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// An IPv4 address can be converted to an IPv6 address by
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// adding a canonical prefix (10 zeros, 2 0xFFs).
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// This library accepts either size of byte array but always
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// returns 16-byte addresses.
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package net
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import "os"
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// IP address lengths (bytes).
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const (
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IPv4len = 4
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IPv6len = 16
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)
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// An IP is a single IP address, an array of bytes.
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// Functions in this package accept either 4-byte (IP v4)
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// or 16-byte (IP v6) arrays as input. Unless otherwise
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// specified, functions in this package always return
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// IP addresses in 16-byte form using the canonical
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// embedding.
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//
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// Note that in this documentation, referring to an
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// IP address as an IPv4 address or an IPv6 address
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// is a semantic property of the address, not just the
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// length of the byte array: a 16-byte array can still
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// be an IPv4 address.
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type IP []byte
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// An IP mask is an IP address.
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type IPMask []byte
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// IPv4 returns the IP address (in 16-byte form) of the
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// IPv4 address a.b.c.d.
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func IPv4(a, b, c, d byte) IP {
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p := make(IP, IPv6len)
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copy(p, v4InV6Prefix)
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p[12] = a
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p[13] = b
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p[14] = c
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p[15] = d
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return p
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}
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var v4InV6Prefix = []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff}
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// IPv4Mask returns the IP mask (in 16-byte form) of the
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// IPv4 mask a.b.c.d.
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func IPv4Mask(a, b, c, d byte) IPMask {
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p := make(IPMask, IPv6len)
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for i := 0; i < 12; i++ {
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p[i] = 0xff
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}
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p[12] = a
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p[13] = b
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p[14] = c
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p[15] = d
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return p
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}
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// Well-known IPv4 addresses
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var (
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IPv4bcast = IPv4(255, 255, 255, 255) // broadcast
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IPv4allsys = IPv4(224, 0, 0, 1) // all systems
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IPv4allrouter = IPv4(224, 0, 0, 2) // all routers
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IPv4zero = IPv4(0, 0, 0, 0) // all zeros
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)
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// Well-known IPv6 addresses
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var (
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IPzero = make(IP, IPv6len) // all zeros
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IPv6loopback = IP([]byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1})
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)
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// Is p all zeros?
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func isZeros(p IP) bool {
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for i := 0; i < len(p); i++ {
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if p[i] != 0 {
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return false
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}
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}
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return true
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}
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// To4 converts the IPv4 address ip to a 4-byte representation.
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// If ip is not an IPv4 address, To4 returns nil.
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func (ip IP) To4() IP {
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if len(ip) == IPv4len {
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return ip
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}
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if len(ip) == IPv6len &&
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isZeros(ip[0:10]) &&
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ip[10] == 0xff &&
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ip[11] == 0xff {
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return ip[12:16]
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}
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return nil
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}
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// To16 converts the IP address ip to a 16-byte representation.
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// If ip is not an IP address (it is the wrong length), To16 returns nil.
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func (ip IP) To16() IP {
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if len(ip) == IPv4len {
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return IPv4(ip[0], ip[1], ip[2], ip[3])
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}
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if len(ip) == IPv6len {
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return ip
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}
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return nil
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}
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// Default route masks for IPv4.
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var (
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classAMask = IPv4Mask(0xff, 0, 0, 0)
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classBMask = IPv4Mask(0xff, 0xff, 0, 0)
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classCMask = IPv4Mask(0xff, 0xff, 0xff, 0)
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)
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// DefaultMask returns the default IP mask for the IP address ip.
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// Only IPv4 addresses have default masks; DefaultMask returns
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// nil if ip is not a valid IPv4 address.
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func (ip IP) DefaultMask() IPMask {
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if ip = ip.To4(); ip == nil {
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return nil
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}
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switch true {
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case ip[0] < 0x80:
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return classAMask
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case ip[0] < 0xC0:
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return classBMask
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default:
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return classCMask
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}
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return nil // not reached
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}
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func allFF(b []byte) bool {
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for _, c := range b {
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if c != 0xff {
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return false
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}
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}
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return true
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}
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// Mask returns the result of masking the IP address ip with mask.
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func (ip IP) Mask(mask IPMask) IP {
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n := len(ip)
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if len(mask) == 16 && len(ip) == 4 && allFF(mask[:12]) {
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mask = mask[12:]
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}
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if len(mask) == 4 && len(ip) == 16 && bytesEqual(ip[:12], v4InV6Prefix) {
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ip = ip[12:]
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}
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if n != len(mask) {
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return nil
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}
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out := make(IP, n)
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for i := 0; i < n; i++ {
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out[i] = ip[i] & mask[i]
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}
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return out
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}
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// Convert i to decimal string.
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func itod(i uint) string {
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if i == 0 {
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return "0"
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}
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// Assemble decimal in reverse order.
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var b [32]byte
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bp := len(b)
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for ; i > 0; i /= 10 {
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bp--
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b[bp] = byte(i%10) + '0'
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}
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return string(b[bp:])
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}
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// Convert i to hexadecimal string.
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func itox(i uint) string {
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if i == 0 {
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return "0"
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}
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// Assemble hexadecimal in reverse order.
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var b [32]byte
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bp := len(b)
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for ; i > 0; i /= 16 {
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bp--
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b[bp] = "0123456789abcdef"[byte(i%16)]
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}
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return string(b[bp:])
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}
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// String returns the string form of the IP address ip.
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// If the address is an IPv4 address, the string representation
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// is dotted decimal ("74.125.19.99"). Otherwise the representation
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// is IPv6 ("2001:4860:0:2001::68").
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func (ip IP) String() string {
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p := ip
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if len(ip) == 0 {
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return ""
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}
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// If IPv4, use dotted notation.
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if p4 := p.To4(); len(p4) == 4 {
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return itod(uint(p4[0])) + "." +
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itod(uint(p4[1])) + "." +
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itod(uint(p4[2])) + "." +
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itod(uint(p4[3]))
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}
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if len(p) != IPv6len {
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return "?"
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}
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// Find longest run of zeros.
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e0 := -1
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e1 := -1
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for i := 0; i < 16; i += 2 {
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j := i
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for j < 16 && p[j] == 0 && p[j+1] == 0 {
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j += 2
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}
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if j > i && j-i > e1-e0 {
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e0 = i
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e1 = j
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}
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}
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// The symbol "::" MUST NOT be used to shorten just one 16 bit 0 field.
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if e1-e0 <= 2 {
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e0 = -1
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e1 = -1
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}
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// Print with possible :: in place of run of zeros
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var s string
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for i := 0; i < 16; i += 2 {
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if i == e0 {
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s += "::"
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i = e1
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if i >= 16 {
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break
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}
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} else if i > 0 {
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s += ":"
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}
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s += itox((uint(p[i]) << 8) | uint(p[i+1]))
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}
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return s
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}
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// Equal returns true if ip and x are the same IP address.
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// An IPv4 address and that same address in IPv6 form are
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// considered to be equal.
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func (ip IP) Equal(x IP) bool {
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if len(ip) == len(x) {
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return bytesEqual(ip, x)
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}
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if len(ip) == 4 && len(x) == 16 {
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return bytesEqual(x[0:12], v4InV6Prefix) && bytesEqual(ip, x[12:])
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}
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if len(ip) == 16 && len(x) == 4 {
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return bytesEqual(ip[0:12], v4InV6Prefix) && bytesEqual(ip[12:], x)
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}
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return false
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}
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func bytesEqual(x, y []byte) bool {
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if len(x) != len(y) {
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return false
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}
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for i, b := range x {
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if y[i] != b {
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return false
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}
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}
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return true
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}
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// If mask is a sequence of 1 bits followed by 0 bits,
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// return the number of 1 bits.
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func simpleMaskLength(mask IPMask) int {
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var n int
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for i, v := range mask {
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if v == 0xff {
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n += 8
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continue
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}
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// found non-ff byte
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// count 1 bits
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for v&0x80 != 0 {
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n++
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v <<= 1
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}
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// rest must be 0 bits
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if v != 0 {
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return -1
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}
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for i++; i < len(mask); i++ {
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if mask[i] != 0 {
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return -1
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}
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}
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break
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}
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return n
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}
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// String returns the string representation of mask.
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// If the mask is in the canonical form--ones followed by zeros--the
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// string representation is just the decimal number of ones.
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// If the mask is in a non-canonical form, it is formatted
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// as an IP address.
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func (mask IPMask) String() string {
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switch len(mask) {
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case 4:
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n := simpleMaskLength(mask)
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if n >= 0 {
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return itod(uint(n + (IPv6len-IPv4len)*8))
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}
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case 16:
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n := simpleMaskLength(mask)
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if n >= 12*8 {
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return itod(uint(n - 12*8))
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}
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}
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return IP(mask).String()
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}
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// Parse IPv4 address (d.d.d.d).
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func parseIPv4(s string) IP {
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var p [IPv4len]byte
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i := 0
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for j := 0; j < IPv4len; j++ {
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if i >= len(s) {
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// Missing octets.
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return nil
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}
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if j > 0 {
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if s[i] != '.' {
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return nil
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}
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i++
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}
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var (
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n int
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ok bool
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)
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n, i, ok = dtoi(s, i)
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if !ok || n > 0xFF {
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return nil
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}
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p[j] = byte(n)
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}
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if i != len(s) {
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return nil
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}
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return IPv4(p[0], p[1], p[2], p[3])
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}
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// Parse IPv6 address. Many forms.
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// The basic form is a sequence of eight colon-separated
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// 16-bit hex numbers separated by colons,
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// as in 0123:4567:89ab:cdef:0123:4567:89ab:cdef.
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// Two exceptions:
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// * A run of zeros can be replaced with "::".
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// * The last 32 bits can be in IPv4 form.
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// Thus, ::ffff:1.2.3.4 is the IPv4 address 1.2.3.4.
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func parseIPv6(s string) IP {
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p := make(IP, 16)
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ellipsis := -1 // position of ellipsis in p
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i := 0 // index in string s
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// Might have leading ellipsis
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if len(s) >= 2 && s[0] == ':' && s[1] == ':' {
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ellipsis = 0
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i = 2
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// Might be only ellipsis
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if i == len(s) {
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return p
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}
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}
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// Loop, parsing hex numbers followed by colon.
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j := 0
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for j < IPv6len {
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// Hex number.
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n, i1, ok := xtoi(s, i)
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if !ok || n > 0xFFFF {
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return nil
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}
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// If followed by dot, might be in trailing IPv4.
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if i1 < len(s) && s[i1] == '.' {
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if ellipsis < 0 && j != IPv6len-IPv4len {
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// Not the right place.
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return nil
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}
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if j+IPv4len > IPv6len {
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// Not enough room.
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return nil
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}
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p4 := parseIPv4(s[i:])
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if p4 == nil {
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return nil
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}
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p[j] = p4[12]
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p[j+1] = p4[13]
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p[j+2] = p4[14]
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p[j+3] = p4[15]
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i = len(s)
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j += 4
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break
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}
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// Save this 16-bit chunk.
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p[j] = byte(n >> 8)
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p[j+1] = byte(n)
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j += 2
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// Stop at end of string.
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i = i1
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if i == len(s) {
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break
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}
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// Otherwise must be followed by colon and more.
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if s[i] != ':' || i+1 == len(s) {
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return nil
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}
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i++
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// Look for ellipsis.
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if s[i] == ':' {
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if ellipsis >= 0 { // already have one
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return nil
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}
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ellipsis = j
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if i++; i == len(s) { // can be at end
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break
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}
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}
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}
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// Must have used entire string.
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if i != len(s) {
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return nil
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}
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// If didn't parse enough, expand ellipsis.
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if j < IPv6len {
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if ellipsis < 0 {
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return nil
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}
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n := IPv6len - j
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for k := j - 1; k >= ellipsis; k-- {
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p[k+n] = p[k]
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}
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for k := ellipsis + n - 1; k >= ellipsis; k-- {
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p[k] = 0
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}
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}
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return p
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}
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// A ParseError represents a malformed text string and the type of string that was expected.
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type ParseError struct {
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Type string
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Text string
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}
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func (e *ParseError) String() string {
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return "invalid " + e.Type + ": " + e.Text
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}
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func parseIP(s string) IP {
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if p := parseIPv4(s); p != nil {
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return p
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}
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if p := parseIPv6(s); p != nil {
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return p
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}
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return nil
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}
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// ParseIP parses s as an IP address, returning the result.
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// The string s can be in dotted decimal ("74.125.19.99")
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// or IPv6 ("2001:4860:0:2001::68") form.
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// If s is not a valid textual representation of an IP address,
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// ParseIP returns nil.
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func ParseIP(s string) IP {
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if p := parseIPv4(s); p != nil {
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return p
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}
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return parseIPv6(s)
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}
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// ParseCIDR parses s as a CIDR notation IP address and mask,
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// like "192.168.100.1/24", "2001:DB8::/48", as defined in
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// RFC 4632 and RFC 4291.
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func ParseCIDR(s string) (ip IP, mask IPMask, err os.Error) {
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i := byteIndex(s, '/')
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if i < 0 {
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return nil, nil, &ParseError{"CIDR address", s}
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}
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ipstr, maskstr := s[:i], s[i+1:]
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iplen := 4
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ip = parseIPv4(ipstr)
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if ip == nil {
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iplen = 16
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ip = parseIPv6(ipstr)
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}
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nn, i, ok := dtoi(maskstr, 0)
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if ip == nil || !ok || i != len(maskstr) || nn < 0 || nn > 8*iplen {
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return nil, nil, &ParseError{"CIDR address", s}
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}
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n := uint(nn)
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if iplen == 4 {
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v4mask := ^uint32(0xffffffff >> n)
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mask = IPv4Mask(byte(v4mask>>24), byte(v4mask>>16), byte(v4mask>>8), byte(v4mask))
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} else {
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mask = make(IPMask, 16)
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for i := 0; i < 16; i++ {
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if n >= 8 {
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mask[i] = 0xff
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n -= 8
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continue
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}
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mask[i] = ^byte(0xff >> n)
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n = 0
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}
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}
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// address must not have any bits not in mask
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for i := range ip {
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if ip[i]&^mask[i] != 0 {
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return nil, nil, &ParseError{"CIDR address", s}
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}
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}
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return ip, mask, nil
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}
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