Source file src/pkg/net/ip.go

     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.
     4	
     5	// IP address manipulations
     6	//
     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.
    12	
    13	package net
    14	
    15	// IP address lengths (bytes).
    16	const (
    17		IPv4len = 4
    18		IPv6len = 16
    19	)
    20	
    21	// An IP is a single IP address, a slice of bytes.
    22	// Functions in this package accept either 4-byte (IPv4)
    23	// or 16-byte (IPv6) slices as input.
    24	//
    25	// Note that in this documentation, referring to an
    26	// IP address as an IPv4 address or an IPv6 address
    27	// is a semantic property of the address, not just the
    28	// length of the byte slice: a 16-byte slice can still
    29	// be an IPv4 address.
    30	type IP []byte
    31	
    32	// An IP mask is an IP address.
    33	type IPMask []byte
    34	
    35	// An IPNet represents an IP network.
    36	type IPNet struct {
    37		IP   IP     // network number
    38		Mask IPMask // network mask
    39	}
    40	
    41	// IPv4 returns the IP address (in 16-byte form) of the
    42	// IPv4 address a.b.c.d.
    43	func IPv4(a, b, c, d byte) IP {
    44		p := make(IP, IPv6len)
    45		copy(p, v4InV6Prefix)
    46		p[12] = a
    47		p[13] = b
    48		p[14] = c
    49		p[15] = d
    50		return p
    51	}
    52	
    53	var v4InV6Prefix = []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff}
    54	
    55	// IPv4Mask returns the IP mask (in 4-byte form) of the
    56	// IPv4 mask a.b.c.d.
    57	func IPv4Mask(a, b, c, d byte) IPMask {
    58		p := make(IPMask, IPv4len)
    59		p[0] = a
    60		p[1] = b
    61		p[2] = c
    62		p[3] = d
    63		return p
    64	}
    65	
    66	// CIDRMask returns an IPMask consisting of `ones' 1 bits
    67	// followed by 0s up to a total length of `bits' bits.
    68	// For a mask of this form, CIDRMask is the inverse of IPMask.Size.
    69	func CIDRMask(ones, bits int) IPMask {
    70		if bits != 8*IPv4len && bits != 8*IPv6len {
    71			return nil
    72		}
    73		if ones < 0 || ones > bits {
    74			return nil
    75		}
    76		l := bits / 8
    77		m := make(IPMask, l)
    78		n := uint(ones)
    79		for i := 0; i < l; i++ {
    80			if n >= 8 {
    81				m[i] = 0xff
    82				n -= 8
    83				continue
    84			}
    85			m[i] = ^byte(0xff >> n)
    86			n = 0
    87		}
    88		return m
    89	}
    90	
    91	// Well-known IPv4 addresses
    92	var (
    93		IPv4bcast     = IPv4(255, 255, 255, 255) // broadcast
    94		IPv4allsys    = IPv4(224, 0, 0, 1)       // all systems
    95		IPv4allrouter = IPv4(224, 0, 0, 2)       // all routers
    96		IPv4zero      = IPv4(0, 0, 0, 0)         // all zeros
    97	)
    98	
    99	// Well-known IPv6 addresses
   100	var (
   101		IPv6zero                   = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
   102		IPv6unspecified            = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
   103		IPv6loopback               = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1}
   104		IPv6interfacelocalallnodes = IP{0xff, 0x01, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x01}
   105		IPv6linklocalallnodes      = IP{0xff, 0x02, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x01}
   106		IPv6linklocalallrouters    = IP{0xff, 0x02, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x02}
   107	)
   108	
   109	// IsUnspecified returns true if ip is an unspecified address.
   110	func (ip IP) IsUnspecified() bool {
   111		if ip.Equal(IPv4zero) || ip.Equal(IPv6unspecified) {
   112			return true
   113		}
   114		return false
   115	}
   116	
   117	// IsLoopback returns true if ip is a loopback address.
   118	func (ip IP) IsLoopback() bool {
   119		if ip4 := ip.To4(); ip4 != nil && ip4[0] == 127 {
   120			return true
   121		}
   122		return ip.Equal(IPv6loopback)
   123	}
   124	
   125	// IsMulticast returns true if ip is a multicast address.
   126	func (ip IP) IsMulticast() bool {
   127		if ip4 := ip.To4(); ip4 != nil && ip4[0]&0xf0 == 0xe0 {
   128			return true
   129		}
   130		return ip[0] == 0xff
   131	}
   132	
   133	// IsInterfaceLinkLocalMulticast returns true if 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
   137	}
   138	
   139	// IsLinkLocalMulticast returns true if ip is a link-local
   140	// multicast address.
   141	func (ip IP) IsLinkLocalMulticast() bool {
   142		if ip4 := ip.To4(); ip4 != nil && ip4[0] == 224 && ip4[1] == 0 && ip4[2] == 0 {
   143			return true
   144		}
   145		return ip[0] == 0xff && ip[1]&0x0f == 0x02
   146	}
   147	
   148	// IsLinkLocalUnicast returns true if ip is a link-local
   149	// unicast address.
   150	func (ip IP) IsLinkLocalUnicast() bool {
   151		if ip4 := ip.To4(); ip4 != nil && ip4[0] == 169 && ip4[1] == 254 {
   152			return true
   153		}
   154		return ip[0] == 0xfe && ip[1]&0xc0 == 0x80
   155	}
   156	
   157	// IsGlobalUnicast returns true if ip is a global unicast
   158	// address.
   159	func (ip IP) IsGlobalUnicast() bool {
   160		return !ip.IsUnspecified() &&
   161			!ip.IsLoopback() &&
   162			!ip.IsMulticast() &&
   163			!ip.IsLinkLocalUnicast()
   164	}
   165	
   166	// Is p all zeros?
   167	func isZeros(p IP) bool {
   168		for i := 0; i < len(p); i++ {
   169			if p[i] != 0 {
   170				return false
   171			}
   172		}
   173		return true
   174	}
   175	
   176	// To4 converts the IPv4 address ip to a 4-byte representation.
   177	// If ip is not an IPv4 address, To4 returns nil.
   178	func (ip IP) To4() IP {
   179		if len(ip) == IPv4len {
   180			return ip
   181		}
   182		if len(ip) == IPv6len &&
   183			isZeros(ip[0:10]) &&
   184			ip[10] == 0xff &&
   185			ip[11] == 0xff {
   186			return ip[12:16]
   187		}
   188		return nil
   189	}
   190	
   191	// To16 converts the IP address ip to a 16-byte representation.
   192	// If ip is not an IP address (it is the wrong length), To16 returns nil.
   193	func (ip IP) To16() IP {
   194		if len(ip) == IPv4len {
   195			return IPv4(ip[0], ip[1], ip[2], ip[3])
   196		}
   197		if len(ip) == IPv6len {
   198			return ip
   199		}
   200		return nil
   201	}
   202	
   203	// Default route masks for IPv4.
   204	var (
   205		classAMask = IPv4Mask(0xff, 0, 0, 0)
   206		classBMask = IPv4Mask(0xff, 0xff, 0, 0)
   207		classCMask = IPv4Mask(0xff, 0xff, 0xff, 0)
   208	)
   209	
   210	// DefaultMask returns the default IP mask for the IP address ip.
   211	// Only IPv4 addresses have default masks; DefaultMask returns
   212	// nil if ip is not a valid IPv4 address.
   213	func (ip IP) DefaultMask() IPMask {
   214		if ip = ip.To4(); ip == nil {
   215			return nil
   216		}
   217		switch true {
   218		case ip[0] < 0x80:
   219			return classAMask
   220		case ip[0] < 0xC0:
   221			return classBMask
   222		default:
   223			return classCMask
   224		}
   225	}
   226	
   227	func allFF(b []byte) bool {
   228		for _, c := range b {
   229			if c != 0xff {
   230				return false
   231			}
   232		}
   233		return true
   234	}
   235	
   236	// Mask returns the result of masking the IP address ip with mask.
   237	func (ip IP) Mask(mask IPMask) IP {
   238		if len(mask) == IPv6len && len(ip) == IPv4len && allFF(mask[:12]) {
   239			mask = mask[12:]
   240		}
   241		if len(mask) == IPv4len && len(ip) == IPv6len && bytesEqual(ip[:12], v4InV6Prefix) {
   242			ip = ip[12:]
   243		}
   244		n := len(ip)
   245		if n != len(mask) {
   246			return nil
   247		}
   248		out := make(IP, n)
   249		for i := 0; i < n; i++ {
   250			out[i] = ip[i] & mask[i]
   251		}
   252		return out
   253	}
   254	
   255	// String returns the string form of the IP address ip.
   256	// If the address is an IPv4 address, the string representation
   257	// is dotted decimal ("74.125.19.99").  Otherwise the representation
   258	// is IPv6 ("2001:4860:0:2001::68").
   259	func (ip IP) String() string {
   260		p := ip
   261	
   262		if len(ip) == 0 {
   263			return "<nil>"
   264		}
   265	
   266		// If IPv4, use dotted notation.
   267		if p4 := p.To4(); len(p4) == IPv4len {
   268			return itod(uint(p4[0])) + "." +
   269				itod(uint(p4[1])) + "." +
   270				itod(uint(p4[2])) + "." +
   271				itod(uint(p4[3]))
   272		}
   273		if len(p) != IPv6len {
   274			return "?"
   275		}
   276	
   277		// Find longest run of zeros.
   278		e0 := -1
   279		e1 := -1
   280		for i := 0; i < IPv6len; i += 2 {
   281			j := i
   282			for j < IPv6len && p[j] == 0 && p[j+1] == 0 {
   283				j += 2
   284			}
   285			if j > i && j-i > e1-e0 {
   286				e0 = i
   287				e1 = j
   288			}
   289		}
   290		// The symbol "::" MUST NOT be used to shorten just one 16 bit 0 field.
   291		if e1-e0 <= 2 {
   292			e0 = -1
   293			e1 = -1
   294		}
   295	
   296		// Print with possible :: in place of run of zeros
   297		var s string
   298		for i := 0; i < IPv6len; i += 2 {
   299			if i == e0 {
   300				s += "::"
   301				i = e1
   302				if i >= IPv6len {
   303					break
   304				}
   305			} else if i > 0 {
   306				s += ":"
   307			}
   308			s += itox((uint(p[i])<<8)|uint(p[i+1]), 1)
   309		}
   310		return s
   311	}
   312	
   313	// Equal returns true if ip and x are the same IP address.
   314	// An IPv4 address and that same address in IPv6 form are
   315	// considered to be equal.
   316	func (ip IP) Equal(x IP) bool {
   317		if len(ip) == len(x) {
   318			return bytesEqual(ip, x)
   319		}
   320		if len(ip) == IPv4len && len(x) == IPv6len {
   321			return bytesEqual(x[0:12], v4InV6Prefix) && bytesEqual(ip, x[12:])
   322		}
   323		if len(ip) == IPv6len && len(x) == IPv4len {
   324			return bytesEqual(ip[0:12], v4InV6Prefix) && bytesEqual(ip[12:], x)
   325		}
   326		return false
   327	}
   328	
   329	func bytesEqual(x, y []byte) bool {
   330		if len(x) != len(y) {
   331			return false
   332		}
   333		for i, b := range x {
   334			if y[i] != b {
   335				return false
   336			}
   337		}
   338		return true
   339	}
   340	
   341	// If mask is a sequence of 1 bits followed by 0 bits,
   342	// return the number of 1 bits.
   343	func simpleMaskLength(mask IPMask) int {
   344		var n int
   345		for i, v := range mask {
   346			if v == 0xff {
   347				n += 8
   348				continue
   349			}
   350			// found non-ff byte
   351			// count 1 bits
   352			for v&0x80 != 0 {
   353				n++
   354				v <<= 1
   355			}
   356			// rest must be 0 bits
   357			if v != 0 {
   358				return -1
   359			}
   360			for i++; i < len(mask); i++ {
   361				if mask[i] != 0 {
   362					return -1
   363				}
   364			}
   365			break
   366		}
   367		return n
   368	}
   369	
   370	// Size returns the number of leading ones and total bits in the mask.
   371	// If the mask is not in the canonical form--ones followed by zeros--then
   372	// Size returns 0, 0.
   373	func (m IPMask) Size() (ones, bits int) {
   374		ones, bits = simpleMaskLength(m), len(m)*8
   375		if ones == -1 {
   376			return 0, 0
   377		}
   378		return
   379	}
   380	
   381	// String returns the hexadecimal form of m, with no punctuation.
   382	func (m IPMask) String() string {
   383		s := ""
   384		for _, b := range m {
   385			s += itox(uint(b), 2)
   386		}
   387		if len(s) == 0 {
   388			return "<nil>"
   389		}
   390		return s
   391	}
   392	
   393	func networkNumberAndMask(n *IPNet) (ip IP, m IPMask) {
   394		if ip = n.IP.To4(); ip == nil {
   395			ip = n.IP
   396			if len(ip) != IPv6len {
   397				return nil, nil
   398			}
   399		}
   400		m = n.Mask
   401		switch len(m) {
   402		case IPv4len:
   403			if len(ip) != IPv4len {
   404				return nil, nil
   405			}
   406		case IPv6len:
   407			if len(ip) == IPv4len {
   408				m = m[12:]
   409			}
   410		default:
   411			return nil, nil
   412		}
   413		return
   414	}
   415	
   416	// Contains reports whether the network includes ip.
   417	func (n *IPNet) Contains(ip IP) bool {
   418		nn, m := networkNumberAndMask(n)
   419		if x := ip.To4(); x != nil {
   420			ip = x
   421		}
   422		l := len(ip)
   423		if l != len(nn) {
   424			return false
   425		}
   426		for i := 0; i < l; i++ {
   427			if nn[i]&m[i] != ip[i]&m[i] {
   428				return false
   429			}
   430		}
   431		return true
   432	}
   433	
   434	// Network returns the address's network name, "ip+net".
   435	func (n *IPNet) Network() string { return "ip+net" }
   436	
   437	// String returns the CIDR notation of n like "192.168.100.1/24"
   438	// or "2001:DB8::/48" as defined in RFC 4632 and RFC 4291.
   439	// If the mask is not in the canonical form, it returns the
   440	// string which consists of an IP address, followed by a slash
   441	// character and a mask expressed as hexadecimal form with no
   442	// punctuation like "192.168.100.1/c000ff00".
   443	func (n *IPNet) String() string {
   444		nn, m := networkNumberAndMask(n)
   445		if nn == nil || m == nil {
   446			return "<nil>"
   447		}
   448		l := simpleMaskLength(m)
   449		if l == -1 {
   450			return nn.String() + "/" + m.String()
   451		}
   452		return nn.String() + "/" + itod(uint(l))
   453	}
   454	
   455	// Parse IPv4 address (d.d.d.d).
   456	func parseIPv4(s string) IP {
   457		var p [IPv4len]byte
   458		i := 0
   459		for j := 0; j < IPv4len; j++ {
   460			if i >= len(s) {
   461				// Missing octets.
   462				return nil
   463			}
   464			if j > 0 {
   465				if s[i] != '.' {
   466					return nil
   467				}
   468				i++
   469			}
   470			var (
   471				n  int
   472				ok bool
   473			)
   474			n, i, ok = dtoi(s, i)
   475			if !ok || n > 0xFF {
   476				return nil
   477			}
   478			p[j] = byte(n)
   479		}
   480		if i != len(s) {
   481			return nil
   482		}
   483		return IPv4(p[0], p[1], p[2], p[3])
   484	}
   485	
   486	// parseIPv6 parses s as a literal IPv6 address described in RFC 4291
   487	// and RFC 5952.  It can also parse a literal scoped IPv6 address with
   488	// zone identifier which is described in RFC 4007 when zoneAllowed is
   489	// true.
   490	func parseIPv6(s string, zoneAllowed bool) (ip IP, zone string) {
   491		ip = make(IP, IPv6len)
   492		ellipsis := -1 // position of ellipsis in p
   493		i := 0         // index in string s
   494	
   495		if zoneAllowed {
   496			s, zone = splitHostZone(s)
   497		}
   498	
   499		// Might have leading ellipsis
   500		if len(s) >= 2 && s[0] == ':' && s[1] == ':' {
   501			ellipsis = 0
   502			i = 2
   503			// Might be only ellipsis
   504			if i == len(s) {
   505				return ip, zone
   506			}
   507		}
   508	
   509		// Loop, parsing hex numbers followed by colon.
   510		j := 0
   511		for j < IPv6len {
   512			// Hex number.
   513			n, i1, ok := xtoi(s, i)
   514			if !ok || n > 0xFFFF {
   515				return nil, zone
   516			}
   517	
   518			// If followed by dot, might be in trailing IPv4.
   519			if i1 < len(s) && s[i1] == '.' {
   520				if ellipsis < 0 && j != IPv6len-IPv4len {
   521					// Not the right place.
   522					return nil, zone
   523				}
   524				if j+IPv4len > IPv6len {
   525					// Not enough room.
   526					return nil, zone
   527				}
   528				ip4 := parseIPv4(s[i:])
   529				if ip4 == nil {
   530					return nil, zone
   531				}
   532				ip[j] = ip4[12]
   533				ip[j+1] = ip4[13]
   534				ip[j+2] = ip4[14]
   535				ip[j+3] = ip4[15]
   536				i = len(s)
   537				j += IPv4len
   538				break
   539			}
   540	
   541			// Save this 16-bit chunk.
   542			ip[j] = byte(n >> 8)
   543			ip[j+1] = byte(n)
   544			j += 2
   545	
   546			// Stop at end of string.
   547			i = i1
   548			if i == len(s) {
   549				break
   550			}
   551	
   552			// Otherwise must be followed by colon and more.
   553			if s[i] != ':' || i+1 == len(s) {
   554				return nil, zone
   555			}
   556			i++
   557	
   558			// Look for ellipsis.
   559			if s[i] == ':' {
   560				if ellipsis >= 0 { // already have one
   561					return nil, zone
   562				}
   563				ellipsis = j
   564				if i++; i == len(s) { // can be at end
   565					break
   566				}
   567			}
   568		}
   569	
   570		// Must have used entire string.
   571		if i != len(s) {
   572			return nil, zone
   573		}
   574	
   575		// If didn't parse enough, expand ellipsis.
   576		if j < IPv6len {
   577			if ellipsis < 0 {
   578				return nil, zone
   579			}
   580			n := IPv6len - j
   581			for k := j - 1; k >= ellipsis; k-- {
   582				ip[k+n] = ip[k]
   583			}
   584			for k := ellipsis + n - 1; k >= ellipsis; k-- {
   585				ip[k] = 0
   586			}
   587		}
   588		return ip, zone
   589	}
   590	
   591	// A ParseError represents a malformed text string and the type of string that was expected.
   592	type ParseError struct {
   593		Type string
   594		Text string
   595	}
   596	
   597	func (e *ParseError) Error() string {
   598		return "invalid " + e.Type + ": " + e.Text
   599	}
   600	
   601	// ParseIP parses s as an IP address, returning the result.
   602	// The string s can be in dotted decimal ("74.125.19.99")
   603	// or IPv6 ("2001:4860:0:2001::68") form.
   604	// If s is not a valid textual representation of an IP address,
   605	// ParseIP returns nil.
   606	func ParseIP(s string) IP {
   607		if ip := parseIPv4(s); ip != nil {
   608			return ip
   609		}
   610		ip, _ := parseIPv6(s, false)
   611		return ip
   612	}
   613	
   614	// ParseCIDR parses s as a CIDR notation IP address and mask,
   615	// like "192.168.100.1/24" or "2001:DB8::/48", as defined in
   616	// RFC 4632 and RFC 4291.
   617	//
   618	// It returns the IP address and the network implied by the IP
   619	// and mask.  For example, ParseCIDR("192.168.100.1/16") returns
   620	// the IP address 192.168.100.1 and the network 192.168.0.0/16.
   621	func ParseCIDR(s string) (IP, *IPNet, error) {
   622		i := byteIndex(s, '/')
   623		if i < 0 {
   624			return nil, nil, &ParseError{"CIDR address", s}
   625		}
   626		addr, mask := s[:i], s[i+1:]
   627		iplen := IPv4len
   628		ip := parseIPv4(addr)
   629		if ip == nil {
   630			iplen = IPv6len
   631			ip, _ = parseIPv6(addr, false)
   632		}
   633		n, i, ok := dtoi(mask, 0)
   634		if ip == nil || !ok || i != len(mask) || n < 0 || n > 8*iplen {
   635			return nil, nil, &ParseError{"CIDR address", s}
   636		}
   637		m := CIDRMask(n, 8*iplen)
   638		return ip, &IPNet{IP: ip.Mask(m), Mask: m}, nil
   639	}

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