blob: 3e0e85e168a72f0d84c61747e55410eabc420012 [file] [log] [blame]
// 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 slice but always
// returns 16-byte addresses.
package net
import (
"internal/bytealg"
"internal/itoa"
"internal/stringslite"
"net/netip"
)
// IP address lengths (bytes).
const (
IPv4len = 4
IPv6len = 16
)
// An IP is a single IP address, a slice of bytes.
// Functions in this package accept either 4-byte (IPv4)
// or 16-byte (IPv6) slices as input.
//
// 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 slice: a 16-byte slice can still
// be an IPv4 address.
type IP []byte
// An IPMask is a bitmask that can be used to manipulate
// IP addresses for IP addressing and routing.
//
// See type [IPNet] and func [ParseCIDR] for details.
type IPMask []byte
// An IPNet represents an IP network.
type IPNet struct {
IP IP // network number
Mask IPMask // network mask
}
// 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)
copy(p, v4InV6Prefix)
p[12] = a
p[13] = b
p[14] = c
p[15] = d
return p
}
var v4InV6Prefix = []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff}
// IPv4Mask returns the IP mask (in 4-byte form) of the
// IPv4 mask a.b.c.d.
func IPv4Mask(a, b, c, d byte) IPMask {
p := make(IPMask, IPv4len)
p[0] = a
p[1] = b
p[2] = c
p[3] = d
return p
}
// CIDRMask returns an [IPMask] consisting of 'ones' 1 bits
// followed by 0s up to a total length of 'bits' bits.
// For a mask of this form, CIDRMask is the inverse of [IPMask.Size].
func CIDRMask(ones, bits int) IPMask {
if bits != 8*IPv4len && bits != 8*IPv6len {
return nil
}
if ones < 0 || ones > bits {
return nil
}
l := bits / 8
m := make(IPMask, l)
n := uint(ones)
for i := 0; i < l; i++ {
if n >= 8 {
m[i] = 0xff
n -= 8
continue
}
m[i] = ^byte(0xff >> n)
n = 0
}
return m
}
// Well-known IPv4 addresses
var (
IPv4bcast = IPv4(255, 255, 255, 255) // limited 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 (
IPv6zero = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
IPv6unspecified = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
IPv6loopback = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1}
IPv6interfacelocalallnodes = IP{0xff, 0x01, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x01}
IPv6linklocalallnodes = IP{0xff, 0x02, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x01}
IPv6linklocalallrouters = IP{0xff, 0x02, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x02}
)
// IsUnspecified reports whether ip is an unspecified address, either
// the IPv4 address "0.0.0.0" or the IPv6 address "::".
func (ip IP) IsUnspecified() bool {
return ip.Equal(IPv4zero) || ip.Equal(IPv6unspecified)
}
// IsLoopback reports whether ip is a loopback address.
func (ip IP) IsLoopback() bool {
if ip4 := ip.To4(); ip4 != nil {
return ip4[0] == 127
}
return ip.Equal(IPv6loopback)
}
// IsPrivate reports whether ip is a private address, according to
// RFC 1918 (IPv4 addresses) and RFC 4193 (IPv6 addresses).
func (ip IP) IsPrivate() bool {
if ip4 := ip.To4(); ip4 != nil {
// Following RFC 1918, Section 3. Private Address Space which says:
// The Internet Assigned Numbers Authority (IANA) has reserved the
// following three blocks of the IP address space for private internets:
// 10.0.0.0 - 10.255.255.255 (10/8 prefix)
// 172.16.0.0 - 172.31.255.255 (172.16/12 prefix)
// 192.168.0.0 - 192.168.255.255 (192.168/16 prefix)
return ip4[0] == 10 ||
(ip4[0] == 172 && ip4[1]&0xf0 == 16) ||
(ip4[0] == 192 && ip4[1] == 168)
}
// Following RFC 4193, Section 8. IANA Considerations which says:
// The IANA has assigned the FC00::/7 prefix to "Unique Local Unicast".
return len(ip) == IPv6len && ip[0]&0xfe == 0xfc
}
// IsMulticast reports whether ip is a multicast address.
func (ip IP) IsMulticast() bool {
if ip4 := ip.To4(); ip4 != nil {
return ip4[0]&0xf0 == 0xe0
}
return len(ip) == IPv6len && ip[0] == 0xff
}
// IsInterfaceLocalMulticast reports whether ip is
// an interface-local multicast address.
func (ip IP) IsInterfaceLocalMulticast() bool {
return len(ip) == IPv6len && ip[0] == 0xff && ip[1]&0x0f == 0x01
}
// IsLinkLocalMulticast reports whether ip is a link-local
// multicast address.
func (ip IP) IsLinkLocalMulticast() bool {
if ip4 := ip.To4(); ip4 != nil {
return ip4[0] == 224 && ip4[1] == 0 && ip4[2] == 0
}
return len(ip) == IPv6len && ip[0] == 0xff && ip[1]&0x0f == 0x02
}
// IsLinkLocalUnicast reports whether ip is a link-local
// unicast address.
func (ip IP) IsLinkLocalUnicast() bool {
if ip4 := ip.To4(); ip4 != nil {
return ip4[0] == 169 && ip4[1] == 254
}
return len(ip) == IPv6len && ip[0] == 0xfe && ip[1]&0xc0 == 0x80
}
// IsGlobalUnicast reports whether ip is a global unicast
// address.
//
// The identification of global unicast addresses uses address type
// identification as defined in RFC 1122, RFC 4632 and RFC 4291 with
// the exception of IPv4 directed broadcast addresses.
// It returns true even if ip is in IPv4 private address space or
// local IPv6 unicast address space.
func (ip IP) IsGlobalUnicast() bool {
return (len(ip) == IPv4len || len(ip) == IPv6len) &&
!ip.Equal(IPv4bcast) &&
!ip.IsUnspecified() &&
!ip.IsLoopback() &&
!ip.IsMulticast() &&
!ip.IsLinkLocalUnicast()
}
// 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 {
case ip[0] < 0x80:
return classAMask
case ip[0] < 0xC0:
return classBMask
default:
return classCMask
}
}
func allFF(b []byte) bool {
for _, c := range b {
if c != 0xff {
return false
}
}
return true
}
// Mask returns the result of masking the IP address ip with mask.
func (ip IP) Mask(mask IPMask) IP {
if len(mask) == IPv6len && len(ip) == IPv4len && allFF(mask[:12]) {
mask = mask[12:]
}
if len(mask) == IPv4len && len(ip) == IPv6len && bytealg.Equal(ip[:12], v4InV6Prefix) {
ip = ip[12:]
}
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
}
// String returns the string form of the IP address ip.
// It returns one of 4 forms:
// - "<nil>", if ip has length 0
// - dotted decimal ("192.0.2.1"), if ip is an IPv4 or IP4-mapped IPv6 address
// - IPv6 conforming to RFC 5952 ("2001:db8::1"), if ip is a valid IPv6 address
// - the hexadecimal form of ip, without punctuation, if no other cases apply
func (ip IP) String() string {
if len(ip) == 0 {
return "<nil>"
}
if len(ip) != IPv4len && len(ip) != IPv6len {
return "?" + hexString(ip)
}
// If IPv4, use dotted notation.
if p4 := ip.To4(); len(p4) == IPv4len {
return netip.AddrFrom4([4]byte(p4)).String()
}
return netip.AddrFrom16([16]byte(ip)).String()
}
func hexString(b []byte) string {
s := make([]byte, len(b)*2)
for i, tn := range b {
s[i*2], s[i*2+1] = hexDigit[tn>>4], hexDigit[tn&0xf]
}
return string(s)
}
// ipEmptyString is like ip.String except that it returns
// an empty string when ip is unset.
func ipEmptyString(ip IP) string {
if len(ip) == 0 {
return ""
}
return ip.String()
}
// MarshalText implements the [encoding.TextMarshaler] interface.
// The encoding is the same as returned by [IP.String], with one exception:
// When len(ip) is zero, it returns an empty slice.
func (ip IP) MarshalText() ([]byte, error) {
if len(ip) == 0 {
return []byte(""), nil
}
if len(ip) != IPv4len && len(ip) != IPv6len {
return nil, &AddrError{Err: "invalid IP address", Addr: hexString(ip)}
}
return []byte(ip.String()), nil
}
// UnmarshalText implements the [encoding.TextUnmarshaler] interface.
// The IP address is expected in a form accepted by [ParseIP].
func (ip *IP) UnmarshalText(text []byte) error {
if len(text) == 0 {
*ip = nil
return nil
}
s := string(text)
x := ParseIP(s)
if x == nil {
return &ParseError{Type: "IP address", Text: s}
}
*ip = x
return nil
}
// Equal reports whether ip and x are the same IP address.
// An IPv4 address and that same address in IPv6 form are
// considered to be equal.
func (ip IP) Equal(x IP) bool {
if len(ip) == len(x) {
return bytealg.Equal(ip, x)
}
if len(ip) == IPv4len && len(x) == IPv6len {
return bytealg.Equal(x[0:12], v4InV6Prefix) && bytealg.Equal(ip, x[12:])
}
if len(ip) == IPv6len && len(x) == IPv4len {
return bytealg.Equal(ip[0:12], v4InV6Prefix) && bytealg.Equal(ip[12:], x)
}
return false
}
func (ip IP) matchAddrFamily(x IP) bool {
return ip.To4() != nil && x.To4() != nil || ip.To16() != nil && ip.To4() == nil && x.To16() != nil && x.To4() == nil
}
// 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
}
// Size returns the number of leading ones and total bits in the mask.
// If the mask is not in the canonical form--ones followed by zeros--then
// Size returns 0, 0.
func (m IPMask) Size() (ones, bits int) {
ones, bits = simpleMaskLength(m), len(m)*8
if ones == -1 {
return 0, 0
}
return
}
// String returns the hexadecimal form of m, with no punctuation.
func (m IPMask) String() string {
if len(m) == 0 {
return "<nil>"
}
return hexString(m)
}
func networkNumberAndMask(n *IPNet) (ip IP, m IPMask) {
if ip = n.IP.To4(); ip == nil {
ip = n.IP
if len(ip) != IPv6len {
return nil, nil
}
}
m = n.Mask
switch len(m) {
case IPv4len:
if len(ip) != IPv4len {
return nil, nil
}
case IPv6len:
if len(ip) == IPv4len {
m = m[12:]
}
default:
return nil, nil
}
return
}
// Contains reports whether the network includes ip.
func (n *IPNet) Contains(ip IP) bool {
nn, m := networkNumberAndMask(n)
if x := ip.To4(); x != nil {
ip = x
}
l := len(ip)
if l != len(nn) {
return false
}
for i := 0; i < l; i++ {
if nn[i]&m[i] != ip[i]&m[i] {
return false
}
}
return true
}
// Network returns the address's network name, "ip+net".
func (n *IPNet) Network() string { return "ip+net" }
// String returns the CIDR notation of n like "192.0.2.0/24"
// or "2001:db8::/48" as defined in RFC 4632 and RFC 4291.
// If the mask is not in the canonical form, it returns the
// string which consists of an IP address, followed by a slash
// character and a mask expressed as hexadecimal form with no
// punctuation like "198.51.100.0/c000ff00".
func (n *IPNet) String() string {
if n == nil {
return "<nil>"
}
nn, m := networkNumberAndMask(n)
if nn == nil || m == nil {
return "<nil>"
}
l := simpleMaskLength(m)
if l == -1 {
return nn.String() + "/" + m.String()
}
return nn.String() + "/" + itoa.Uitoa(uint(l))
}
// ParseIP parses s as an IP address, returning the result.
// The string s can be in IPv4 dotted decimal ("192.0.2.1"), IPv6
// ("2001:db8::68"), or IPv4-mapped IPv6 ("::ffff:192.0.2.1") form.
// If s is not a valid textual representation of an IP address,
// ParseIP returns nil. The returned address is always 16 bytes,
// IPv4 addresses are returned in IPv4-mapped IPv6 form.
func ParseIP(s string) IP {
if addr, valid := parseIP(s); valid {
return IP(addr[:])
}
return nil
}
func parseIP(s string) ([16]byte, bool) {
ip, err := netip.ParseAddr(s)
if err != nil || ip.Zone() != "" {
return [16]byte{}, false
}
return ip.As16(), true
}
// ParseCIDR parses s as a CIDR notation IP address and prefix length,
// like "192.0.2.0/24" or "2001:db8::/32", as defined in
// RFC 4632 and RFC 4291.
//
// It returns the IP address and the network implied by the IP and
// prefix length.
// For example, ParseCIDR("192.0.2.1/24") returns the IP address
// 192.0.2.1 and the network 192.0.2.0/24.
func ParseCIDR(s string) (IP, *IPNet, error) {
addr, mask, found := stringslite.Cut(s, "/")
if !found {
return nil, nil, &ParseError{Type: "CIDR address", Text: s}
}
ipAddr, err := netip.ParseAddr(addr)
if err != nil || ipAddr.Zone() != "" {
return nil, nil, &ParseError{Type: "CIDR address", Text: s}
}
n, i, ok := dtoi(mask)
if !ok || i != len(mask) || n < 0 || n > ipAddr.BitLen() {
return nil, nil, &ParseError{Type: "CIDR address", Text: s}
}
m := CIDRMask(n, ipAddr.BitLen())
addr16 := ipAddr.As16()
return IP(addr16[:]), &IPNet{IP: IP(addr16[:]).Mask(m), Mask: m}, nil
}
func copyIP(x IP) IP {
y := make(IP, len(x))
copy(y, x)
return y
}