| // 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 (IP v4) |
| // or 16-byte (IP v6) arrays as input. Unless otherwise |
| // specified, functions in this package always return |
| // IP addresses in 16-byte form using the canonical |
| // embedding. |
| // |
| // 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 |
| |
| // 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) |
| for i := 0; i < 10; i++ { |
| p[i] = 0 |
| } |
| p[10] = 0xff |
| p[11] = 0xff |
| p[12] = a |
| p[13] = b |
| p[14] = c |
| p[15] = d |
| return p |
| } |
| |
| // IPv4Mask returns the IP mask (in 16-byte form) of the |
| // IPv4 mask a.b.c.d. |
| func IPv4Mask(a, b, c, d byte) IPMask { |
| p := make(IPMask, IPv6len) |
| for i := 0; i < 12; i++ { |
| p[i] = 0xff |
| } |
| p[12] = a |
| p[13] = b |
| p[14] = c |
| p[15] = d |
| return p |
| } |
| |
| // 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 ( |
| IPzero = make(IP, IPv6len) // all zeros |
| ) |
| |
| // 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 |
| } |
| |
| // Mask returns the result of masking the IP address ip with mask. |
| func (ip IP) Mask(mask IPMask) IP { |
| 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 |
| } |
| |
| // Convert i to decimal string. |
| func itod(i uint) string { |
| if i == 0 { |
| return "0" |
| } |
| |
| // Assemble decimal in reverse order. |
| var b [32]byte |
| bp := len(b) |
| for ; i > 0; i /= 10 { |
| bp-- |
| b[bp] = byte(i%10) + '0' |
| } |
| |
| return string(b[bp:]) |
| } |
| |
| // Convert i to hexadecimal string. |
| func itox(i uint) string { |
| if i == 0 { |
| return "0" |
| } |
| |
| // Assemble hexadecimal in reverse order. |
| var b [32]byte |
| bp := len(b) |
| for ; i > 0; i /= 16 { |
| bp-- |
| b[bp] = "0123456789abcdef"[byte(i%16)] |
| } |
| |
| return string(b[bp:]) |
| } |
| |
| // 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) == 4 { |
| 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 < 16; i += 2 { |
| j := i |
| for j < 16 && 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 < 16; i += 2 { |
| if i == e0 { |
| s += "::" |
| i = e1 |
| if i >= 16 { |
| break |
| } |
| } else if i > 0 { |
| s += ":" |
| } |
| s += itox((uint(p[i]) << 8) | uint(p[i+1])) |
| } |
| return s |
| } |
| |
| // 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 |
| } |
| |
| // String returns the string representation of mask. |
| // If the mask is in the canonical form--ones followed by zeros--the |
| // string representation is just the decimal number of ones. |
| // If the mask is in a non-canonical form, it is formatted |
| // as an IP address. |
| func (mask IPMask) String() string { |
| switch len(mask) { |
| case 4: |
| n := simpleMaskLength(mask) |
| if n >= 0 { |
| return itod(uint(n + (IPv6len-IPv4len)*8)) |
| } |
| case 16: |
| n := simpleMaskLength(mask) |
| if n >= 12*8 { |
| return itod(uint(n - 12*8)) |
| } |
| } |
| return IP(mask).String() |
| } |
| |
| // 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, 16) |
| 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 |
| L: |
| 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 += 4 |
| 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 |
| } |
| |
| // 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 { |
| p := parseIPv4(s) |
| if p != nil { |
| return p |
| } |
| return parseIPv6(s) |
| } |