// 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 net // 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 (IPv4) // or 16-byte (IPv6) arrays 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 array: a 16-byte array can still // be an IPv4 address. type IP []byte // An IP mask is an IP address. 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) // 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 returns true if ip is an unspecified address. func (ip IP) IsUnspecified() bool { if ip.Equal(IPv4zero) || ip.Equal(IPv6unspecified) { return true } return false } // IsLoopback returns true if ip is a loopback address. func (ip IP) IsLoopback() bool { if ip4 := ip.To4(); ip4 != nil && ip4[0] == 127 { return true } return ip.Equal(IPv6loopback) } // IsMulticast returns true if ip is a multicast address. func (ip IP) IsMulticast() bool { if ip4 := ip.To4(); ip4 != nil && ip4[0]&0xf0 == 0xe0 { return true } return ip[0] == 0xff } // IsInterfaceLinkLocalMulticast returns true if ip is // an interface-local multicast address. func (ip IP) IsInterfaceLocalMulticast() bool { return len(ip) == IPv6len && ip[0] == 0xff && ip[1]&0x0f == 0x01 } // IsLinkLocalMulticast returns true if ip is a link-local // multicast address. func (ip IP) IsLinkLocalMulticast() bool { if ip4 := ip.To4(); ip4 != nil && ip4[0] == 224 && ip4[1] == 0 && ip4[2] == 0 { return true } return ip[0] == 0xff && ip[1]&0x0f == 0x02 } // IsLinkLocalUnicast returns true if ip is a link-local // unicast address. func (ip IP) IsLinkLocalUnicast() bool { if ip4 := ip.To4(); ip4 != nil && ip4[0] == 169 && ip4[1] == 254 { return true } return ip[0] == 0xfe && ip[1]&0xc0 == 0x80 } // IsGlobalUnicast returns true if ip is a global unicast // address. func (ip IP) IsGlobalUnicast() bool { return !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 true { case ip[0] < 0x80: return classAMask case ip[0] < 0xC0: return classBMask default: return classCMask } return nil // not reached } 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 && bytesEqual(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. // 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) == IPv4len { 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 < IPv6len; i += 2 { j := i for j < IPv6len && p[j] == 0 && p[j+1] == 0 { j += 2 } if j > i && j-i > e1-e0 { e0 = i e1 = j } } // The symbol "::" MUST NOT be used to shorten just one 16 bit 0 field. if e1-e0 <= 2 { e0 = -1 e1 = -1 } // Print with possible :: in place of run of zeros var s string for i := 0; i < IPv6len; i += 2 { if i == e0 { s += "::" i = e1 if i >= IPv6len { break } } else if i > 0 { s += ":" } s += itox((uint(p[i])<<8)|uint(p[i+1]), 1) } return s } // Equal returns true if 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 bytesEqual(ip, x) } if len(ip) == IPv4len && len(x) == IPv6len { return bytesEqual(x[0:12], v4InV6Prefix) && bytesEqual(ip, x[12:]) } if len(ip) == IPv6len && len(x) == IPv4len { return bytesEqual(ip[0:12], v4InV6Prefix) && bytesEqual(ip[12:], x) } return false } func bytesEqual(x, y []byte) bool { if len(x) != len(y) { return false } for i, b := range x { if y[i] != b { return false } } return true } // 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 { s := "" for _, b := range m { s += itox(uint(b), 2) } if len(s) == 0 { return "" } return s } 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 } // String returns the CIDR notation of n like "192.168.100.1/24" // 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 "192.168.100.1/c000ff00". func (n *IPNet) String() string { nn, m := networkNumberAndMask(n) if nn == nil || m == nil { return "" } l := simpleMaskLength(m) if l == -1 { return nn.String() + "/" + m.String() } return nn.String() + "/" + itod(uint(l)) } // 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, IPv6len) 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 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 += IPv4len 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 } // A ParseError represents a malformed text string and the type of string that was expected. type ParseError struct { Type string Text string } func (e *ParseError) Error() string { return "invalid " + e.Type + ": " + e.Text } func parseIP(s string) IP { if p := parseIPv4(s); p != nil { return p } if p := parseIPv6(s); p != nil { return p } return nil } // 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 { if p := parseIPv4(s); p != nil { return p } return parseIPv6(s) } // ParseCIDR parses s as a CIDR notation IP address and mask, // like "192.168.100.1/24" or "2001:DB8::/48", as defined in // RFC 4632 and RFC 4291. // // It returns the IP address and the network implied by the IP // and mask. For example, ParseCIDR("192.168.100.1/16") returns // the IP address 192.168.100.1 and the network 192.168.0.0/16. func ParseCIDR(s string) (IP, *IPNet, error) { i := byteIndex(s, '/') if i < 0 { return nil, nil, &ParseError{"CIDR address", s} } ipstr, maskstr := s[:i], s[i+1:] iplen := IPv4len ip := parseIPv4(ipstr) if ip == nil { iplen = IPv6len ip = parseIPv6(ipstr) } n, i, ok := dtoi(maskstr, 0) if ip == nil || !ok || i != len(maskstr) || n < 0 || n > 8*iplen { return nil, nil, &ParseError{"CIDR address", s} } m := CIDRMask(n, 8*iplen) return ip, &IPNet{ip.Mask(m), m}, nil }