1 // Copyright 2009 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
5 // IP address manipulations
7 // IPv4 addresses are 4 bytes; IPv6 addresses are 16 bytes.
8 // An IPv4 address can be converted to an IPv6 address by
9 // adding a canonical prefix (10 zeros, 2 0xFFs).
10 // This library accepts either size of byte slice but always
11 // returns 16-byte addresses.
15 import "internal/bytealg"
17 // IP address lengths (bytes).
23 // An IP is a single IP address, a slice of bytes.
24 // Functions in this package accept either 4-byte (IPv4)
25 // or 16-byte (IPv6) slices as input.
27 // Note that in this documentation, referring to an
28 // IP address as an IPv4 address or an IPv6 address
29 // is a semantic property of the address, not just the
30 // length of the byte slice: a 16-byte slice can still
31 // be an IPv4 address.
34 // An IP mask is an IP address.
37 // An IPNet represents an IP network.
39 IP IP // network number
40 Mask IPMask // network mask
43 // IPv4 returns the IP address (in 16-byte form) of the
44 // IPv4 address a.b.c.d.
45 func IPv4(a, b, c, d byte) IP {
46 p := make(IP, IPv6len)
55 var v4InV6Prefix = []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff}
57 // IPv4Mask returns the IP mask (in 4-byte form) of the
59 func IPv4Mask(a, b, c, d byte) IPMask {
60 p := make(IPMask, IPv4len)
68 // CIDRMask returns an IPMask consisting of `ones' 1 bits
69 // followed by 0s up to a total length of `bits' bits.
70 // For a mask of this form, CIDRMask is the inverse of IPMask.Size.
71 func CIDRMask(ones, bits int) IPMask {
72 if bits != 8*IPv4len && bits != 8*IPv6len {
75 if ones < 0 || ones > bits {
81 for i := 0; i < l; i++ {
87 m[i] = ^byte(0xff >> n)
93 // Well-known IPv4 addresses
95 IPv4bcast = IPv4(255, 255, 255, 255) // limited broadcast
96 IPv4allsys = IPv4(224, 0, 0, 1) // all systems
97 IPv4allrouter = IPv4(224, 0, 0, 2) // all routers
98 IPv4zero = IPv4(0, 0, 0, 0) // all zeros
101 // Well-known IPv6 addresses
103 IPv6zero = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
104 IPv6unspecified = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
105 IPv6loopback = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1}
106 IPv6interfacelocalallnodes = IP{0xff, 0x01, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x01}
107 IPv6linklocalallnodes = IP{0xff, 0x02, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x01}
108 IPv6linklocalallrouters = IP{0xff, 0x02, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x02}
111 // IsUnspecified reports whether ip is an unspecified address, either
112 // the IPv4 address "0.0.0.0" or the IPv6 address "::".
113 func (ip IP) IsUnspecified() bool {
114 return ip.Equal(IPv4zero) || ip.Equal(IPv6unspecified)
117 // IsLoopback reports whether ip is a loopback address.
118 func (ip IP) IsLoopback() bool {
119 if ip4 := ip.To4(); ip4 != nil {
122 return ip.Equal(IPv6loopback)
125 // IsMulticast reports whether ip is a multicast address.
126 func (ip IP) IsMulticast() bool {
127 if ip4 := ip.To4(); ip4 != nil {
128 return ip4[0]&0xf0 == 0xe0
130 return len(ip) == IPv6len && ip[0] == 0xff
133 // IsInterfaceLocalMulticast reports whether ip is
134 // an interface-local multicast address.
135 func (ip IP) IsInterfaceLocalMulticast() bool {
136 return len(ip) == IPv6len && ip[0] == 0xff && ip[1]&0x0f == 0x01
139 // IsLinkLocalMulticast reports whether ip is a link-local
140 // multicast address.
141 func (ip IP) IsLinkLocalMulticast() bool {
142 if ip4 := ip.To4(); ip4 != nil {
143 return ip4[0] == 224 && ip4[1] == 0 && ip4[2] == 0
145 return len(ip) == IPv6len && ip[0] == 0xff && ip[1]&0x0f == 0x02
148 // IsLinkLocalUnicast reports whether ip is a link-local
150 func (ip IP) IsLinkLocalUnicast() bool {
151 if ip4 := ip.To4(); ip4 != nil {
152 return ip4[0] == 169 && ip4[1] == 254
154 return len(ip) == IPv6len && ip[0] == 0xfe && ip[1]&0xc0 == 0x80
157 // IsGlobalUnicast reports whether ip is a global unicast
160 // The identification of global unicast addresses uses address type
161 // identification as defined in RFC 1122, RFC 4632 and RFC 4291 with
162 // the exception of IPv4 directed broadcast addresses.
163 // It returns true even if ip is in IPv4 private address space or
164 // local IPv6 unicast address space.
165 func (ip IP) IsGlobalUnicast() bool {
166 return (len(ip) == IPv4len || len(ip) == IPv6len) &&
167 !ip.Equal(IPv4bcast) &&
168 !ip.IsUnspecified() &&
171 !ip.IsLinkLocalUnicast()
175 func isZeros(p IP) bool {
176 for i := 0; i < len(p); i++ {
184 // To4 converts the IPv4 address ip to a 4-byte representation.
185 // If ip is not an IPv4 address, To4 returns nil.
186 func (ip IP) To4() IP {
187 if len(ip) == IPv4len {
190 if len(ip) == IPv6len &&
199 // To16 converts the IP address ip to a 16-byte representation.
200 // If ip is not an IP address (it is the wrong length), To16 returns nil.
201 func (ip IP) To16() IP {
202 if len(ip) == IPv4len {
203 return IPv4(ip[0], ip[1], ip[2], ip[3])
205 if len(ip) == IPv6len {
211 // Default route masks for IPv4.
213 classAMask = IPv4Mask(0xff, 0, 0, 0)
214 classBMask = IPv4Mask(0xff, 0xff, 0, 0)
215 classCMask = IPv4Mask(0xff, 0xff, 0xff, 0)
218 // DefaultMask returns the default IP mask for the IP address ip.
219 // Only IPv4 addresses have default masks; DefaultMask returns
220 // nil if ip is not a valid IPv4 address.
221 func (ip IP) DefaultMask() IPMask {
222 if ip = ip.To4(); ip == nil {
235 func allFF(b []byte) bool {
236 for _, c := range b {
244 // Mask returns the result of masking the IP address ip with mask.
245 func (ip IP) Mask(mask IPMask) IP {
246 if len(mask) == IPv6len && len(ip) == IPv4len && allFF(mask[:12]) {
249 if len(mask) == IPv4len && len(ip) == IPv6len && bytealg.Equal(ip[:12], v4InV6Prefix) {
257 for i := 0; i < n; i++ {
258 out[i] = ip[i] & mask[i]
263 // ubtoa encodes the string form of the integer v to dst[start:] and
264 // returns the number of bytes written to dst. The caller must ensure
265 // that dst has sufficient length.
266 func ubtoa(dst []byte, start int, v byte) int {
271 dst[start+1] = v%10 + '0'
272 dst[start] = v/10 + '0'
276 dst[start+2] = v%10 + '0'
277 dst[start+1] = (v/10)%10 + '0'
278 dst[start] = v/100 + '0'
282 // String returns the string form of the IP address ip.
283 // It returns one of 4 forms:
284 // - "<nil>", if ip has length 0
285 // - dotted decimal ("192.0.2.1"), if ip is an IPv4 or IP4-mapped IPv6 address
286 // - IPv6 ("2001:db8::1"), if ip is a valid IPv6 address
287 // - the hexadecimal form of ip, without punctuation, if no other cases apply
288 func (ip IP) String() string {
295 // If IPv4, use dotted notation.
296 if p4 := p.To4(); len(p4) == IPv4len {
297 const maxIPv4StringLen = len("255.255.255.255")
298 b := make([]byte, maxIPv4StringLen)
300 n := ubtoa(b, 0, p4[0])
304 n += ubtoa(b, n, p4[1])
308 n += ubtoa(b, n, p4[2])
312 n += ubtoa(b, n, p4[3])
315 if len(p) != IPv6len {
316 return "?" + hexString(ip)
319 // Find longest run of zeros.
322 for i := 0; i < IPv6len; i += 2 {
324 for j < IPv6len && p[j] == 0 && p[j+1] == 0 {
327 if j > i && j-i > e1-e0 {
333 // The symbol "::" MUST NOT be used to shorten just one 16 bit 0 field.
339 const maxLen = len("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff")
340 b := make([]byte, 0, maxLen)
342 // Print with possible :: in place of run of zeros
343 for i := 0; i < IPv6len; i += 2 {
345 b = append(b, ':', ':')
353 b = appendHex(b, (uint32(p[i])<<8)|uint32(p[i+1]))
358 func hexString(b []byte) string {
359 s := make([]byte, len(b)*2)
360 for i, tn := range b {
361 s[i*2], s[i*2+1] = hexDigit[tn>>4], hexDigit[tn&0xf]
366 // ipEmptyString is like ip.String except that it returns
367 // an empty string when ip is unset.
368 func ipEmptyString(ip IP) string {
375 // MarshalText implements the encoding.TextMarshaler interface.
376 // The encoding is the same as returned by String, with one exception:
377 // When len(ip) is zero, it returns an empty slice.
378 func (ip IP) MarshalText() ([]byte, error) {
380 return []byte(""), nil
382 if len(ip) != IPv4len && len(ip) != IPv6len {
383 return nil, &AddrError{Err: "invalid IP address", Addr: hexString(ip)}
385 return []byte(ip.String()), nil
388 // UnmarshalText implements the encoding.TextUnmarshaler interface.
389 // The IP address is expected in a form accepted by ParseIP.
390 func (ip *IP) UnmarshalText(text []byte) error {
398 return &ParseError{Type: "IP address", Text: s}
404 // Equal reports whether ip and x are the same IP address.
405 // An IPv4 address and that same address in IPv6 form are
406 // considered to be equal.
407 func (ip IP) Equal(x IP) bool {
408 if len(ip) == len(x) {
409 return bytealg.Equal(ip, x)
411 if len(ip) == IPv4len && len(x) == IPv6len {
412 return bytealg.Equal(x[0:12], v4InV6Prefix) && bytealg.Equal(ip, x[12:])
414 if len(ip) == IPv6len && len(x) == IPv4len {
415 return bytealg.Equal(ip[0:12], v4InV6Prefix) && bytealg.Equal(ip[12:], x)
420 func (ip IP) matchAddrFamily(x IP) bool {
421 return ip.To4() != nil && x.To4() != nil || ip.To16() != nil && ip.To4() == nil && x.To16() != nil && x.To4() == nil
424 // If mask is a sequence of 1 bits followed by 0 bits,
425 // return the number of 1 bits.
426 func simpleMaskLength(mask IPMask) int {
428 for i, v := range mask {
439 // rest must be 0 bits
443 for i++; i < len(mask); i++ {
453 // Size returns the number of leading ones and total bits in the mask.
454 // If the mask is not in the canonical form--ones followed by zeros--then
455 // Size returns 0, 0.
456 func (m IPMask) Size() (ones, bits int) {
457 ones, bits = simpleMaskLength(m), len(m)*8
464 // String returns the hexadecimal form of m, with no punctuation.
465 func (m IPMask) String() string {
472 func networkNumberAndMask(n *IPNet) (ip IP, m IPMask) {
473 if ip = n.IP.To4(); ip == nil {
475 if len(ip) != IPv6len {
482 if len(ip) != IPv4len {
486 if len(ip) == IPv4len {
495 // Contains reports whether the network includes ip.
496 func (n *IPNet) Contains(ip IP) bool {
497 nn, m := networkNumberAndMask(n)
498 if x := ip.To4(); x != nil {
505 for i := 0; i < l; i++ {
506 if nn[i]&m[i] != ip[i]&m[i] {
513 // Network returns the address's network name, "ip+net".
514 func (n *IPNet) Network() string { return "ip+net" }
516 // String returns the CIDR notation of n like "192.0.2.0/24"
517 // or "2001:db8::/48" as defined in RFC 4632 and RFC 4291.
518 // If the mask is not in the canonical form, it returns the
519 // string which consists of an IP address, followed by a slash
520 // character and a mask expressed as hexadecimal form with no
521 // punctuation like "198.51.100.0/c000ff00".
522 func (n *IPNet) String() string {
523 nn, m := networkNumberAndMask(n)
524 if nn == nil || m == nil {
527 l := simpleMaskLength(m)
529 return nn.String() + "/" + m.String()
531 return nn.String() + "/" + uitoa(uint(l))
534 // Parse IPv4 address (d.d.d.d).
535 func parseIPv4(s string) IP {
537 for i := 0; i < IPv4len; i++ {
558 return IPv4(p[0], p[1], p[2], p[3])
561 // parseIPv6Zone parses s as a literal IPv6 address and its associated zone
562 // identifier which is described in RFC 4007.
563 func parseIPv6Zone(s string) (IP, string) {
564 s, zone := splitHostZone(s)
565 return parseIPv6(s), zone
568 // parseIPv6 parses s as a literal IPv6 address described in RFC 4291
570 func parseIPv6(s string) (ip IP) {
571 ip = make(IP, IPv6len)
572 ellipsis := -1 // position of ellipsis in ip
574 // Might have leading ellipsis
575 if len(s) >= 2 && s[0] == ':' && s[1] == ':' {
578 // Might be only ellipsis
584 // Loop, parsing hex numbers followed by colon.
589 if !ok || n > 0xFFFF {
593 // If followed by dot, might be in trailing IPv4.
594 if c < len(s) && s[c] == '.' {
595 if ellipsis < 0 && i != IPv6len-IPv4len {
596 // Not the right place.
599 if i+IPv4len > IPv6len {
616 // Save this 16-bit chunk.
621 // Stop at end of string.
627 // Otherwise must be followed by colon and more.
628 if s[0] != ':' || len(s) == 1 {
633 // Look for ellipsis.
635 if ellipsis >= 0 { // already have one
640 if len(s) == 0 { // can be at end
646 // Must have used entire string.
651 // If didn't parse enough, expand ellipsis.
657 for j := i - 1; j >= ellipsis; j-- {
660 for j := ellipsis + n - 1; j >= ellipsis; j-- {
663 } else if ellipsis >= 0 {
664 // Ellipsis must represent at least one 0 group.
670 // ParseIP parses s as an IP address, returning the result.
671 // The string s can be in dotted decimal ("192.0.2.1")
672 // or IPv6 ("2001:db8::68") form.
673 // If s is not a valid textual representation of an IP address,
674 // ParseIP returns nil.
675 func ParseIP(s string) IP {
676 for i := 0; i < len(s); i++ {
687 // parseIPZone parses s as an IP address, return it and its associated zone
688 // identifier (IPv6 only).
689 func parseIPZone(s string) (IP, string) {
690 for i := 0; i < len(s); i++ {
693 return parseIPv4(s), ""
695 return parseIPv6Zone(s)
701 // ParseCIDR parses s as a CIDR notation IP address and prefix length,
702 // like "192.0.2.0/24" or "2001:db8::/32", as defined in
703 // RFC 4632 and RFC 4291.
705 // It returns the IP address and the network implied by the IP and
707 // For example, ParseCIDR("192.0.2.1/24") returns the IP address
708 // 192.0.2.1 and the network 192.0.2.0/24.
709 func ParseCIDR(s string) (IP, *IPNet, error) {
710 i := bytealg.IndexByteString(s, '/')
712 return nil, nil, &ParseError{Type: "CIDR address", Text: s}
714 addr, mask := s[:i], s[i+1:]
716 ip := parseIPv4(addr)
721 n, i, ok := dtoi(mask)
722 if ip == nil || !ok || i != len(mask) || n < 0 || n > 8*iplen {
723 return nil, nil, &ParseError{Type: "CIDR address", Text: s}
725 m := CIDRMask(n, 8*iplen)
726 return ip, &IPNet{IP: ip.Mask(m), Mask: m}, nil