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Diffstat (limited to 'src/pkg/net/ip.go')
-rw-r--r-- | src/pkg/net/ip.go | 614 |
1 files changed, 614 insertions, 0 deletions
diff --git a/src/pkg/net/ip.go b/src/pkg/net/ip.go new file mode 100644 index 000000000..b0e2c4205 --- /dev/null +++ b/src/pkg/net/ip.go @@ -0,0 +1,614 @@ +// 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 + +import "os" + +// 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) + 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 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 ( + 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 { + n := len(ip) + if len(mask) == 16 && len(ip) == 4 && allFF(mask[:12]) { + mask = mask[12:] + } + if len(mask) == 4 && len(ip) == 16 && bytesEqual(ip[:12], v4InV6Prefix) { + ip = ip[12:] + } + 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 +} + +// 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) == 4 && len(x) == 16 { + return bytesEqual(x[0:12], v4InV6Prefix) && bytesEqual(ip, x[12:]) + } + if len(ip) == 16 && len(x) == 4 { + 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 +} + +// 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 + 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 +} + +// 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) String() 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", "2001:DB8::/48", as defined in +// RFC 4632 and RFC 4291. +func ParseCIDR(s string) (ip IP, mask IPMask, err os.Error) { + i := byteIndex(s, '/') + if i < 0 { + return nil, nil, &ParseError{"CIDR address", s} + } + ipstr, maskstr := s[:i], s[i+1:] + iplen := 4 + ip = parseIPv4(ipstr) + if ip == nil { + iplen = 16 + ip = parseIPv6(ipstr) + } + nn, i, ok := dtoi(maskstr, 0) + if ip == nil || !ok || i != len(maskstr) || nn < 0 || nn > 8*iplen { + return nil, nil, &ParseError{"CIDR address", s} + } + n := uint(nn) + if iplen == 4 { + v4mask := ^uint32(0xffffffff >> n) + mask = IPv4Mask(byte(v4mask>>24), byte(v4mask>>16), byte(v4mask>>8), byte(v4mask)) + } else { + mask = make(IPMask, 16) + for i := 0; i < 16; i++ { + if n >= 8 { + mask[i] = 0xff + n -= 8 + continue + } + mask[i] = ^byte(0xff >> n) + n = 0 + + } + } + // address must not have any bits not in mask + for i := range ip { + if ip[i]&^mask[i] != 0 { + return nil, nil, &ParseError{"CIDR address", s} + } + } + return ip, mask, nil +} |