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// 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 slice but always
// returns 16-byte addresses.
package ipaddr
import (
stdnet "net"
)
//
// Lean on the standard net lib as much as possible.
//
type IP = stdnet.IP
type IPNet = stdnet.IPNet
type ParseError = stdnet.ParseError
const IPv4len = stdnet.IPv4len
const IPv6len = stdnet.IPv6len
var CIDRMask = stdnet.CIDRMask
var IPv4 = stdnet.IPv4
// Parse IPv4 address (d.d.d.d).
func parseIPv4(s string) IP {
var p [IPv4len]byte
for i := 0; i < IPv4len; i++ {
if len(s) == 0 {
// Missing octets.
return nil
}
if i > 0 {
if s[0] != '.' {
return nil
}
s = s[1:]
}
n, c, ok := dtoi(s)
if !ok || n > 0xFF {
return nil
}
//
// NOTE: This correct check was added for go-1.17, but is a
// backwards-incompatible change for Terraform users, who might have
// already written modules with leading zeroes.
//
//if c > 1 && s[0] == '0' {
// // Reject non-zero components with leading zeroes.
// return nil
//}
s = s[c:]
p[i] = byte(n)
}
if len(s) != 0 {
return nil
}
return IPv4(p[0], p[1], p[2], p[3])
}
// parseIPv6 parses s as a literal IPv6 address described in RFC 4291
// and RFC 5952.
func parseIPv6(s string) (ip IP) {
ip = make(IP, IPv6len)
ellipsis := -1 // position of ellipsis in ip
// Might have leading ellipsis
if len(s) >= 2 && s[0] == ':' && s[1] == ':' {
ellipsis = 0
s = s[2:]
// Might be only ellipsis
if len(s) == 0 {
return ip
}
}
// Loop, parsing hex numbers followed by colon.
i := 0
for i < IPv6len {
// Hex number.
n, c, ok := xtoi(s)
if !ok || n > 0xFFFF {
return nil
}
// If followed by dot, might be in trailing IPv4.
if c < len(s) && s[c] == '.' {
if ellipsis < 0 && i != IPv6len-IPv4len {
// Not the right place.
return nil
}
if i+IPv4len > IPv6len {
// Not enough room.
return nil
}
ip4 := parseIPv4(s)
if ip4 == nil {
return nil
}
ip[i] = ip4[12]
ip[i+1] = ip4[13]
ip[i+2] = ip4[14]
ip[i+3] = ip4[15]
s = ""
i += IPv4len
break
}
// Save this 16-bit chunk.
ip[i] = byte(n >> 8)
ip[i+1] = byte(n)
i += 2
// Stop at end of string.
s = s[c:]
if len(s) == 0 {
break
}
// Otherwise must be followed by colon and more.
if s[0] != ':' || len(s) == 1 {
return nil
}
s = s[1:]
// Look for ellipsis.
if s[0] == ':' {
if ellipsis >= 0 { // already have one
return nil
}
ellipsis = i
s = s[1:]
if len(s) == 0 { // can be at end
break
}
}
}
// Must have used entire string.
if len(s) != 0 {
return nil
}
// If didn't parse enough, expand ellipsis.
if i < IPv6len {
if ellipsis < 0 {
return nil
}
n := IPv6len - i
for j := i - 1; j >= ellipsis; j-- {
ip[j+n] = ip[j]
}
for j := ellipsis + n - 1; j >= ellipsis; j-- {
ip[j] = 0
}
} else if ellipsis >= 0 {
// Ellipsis must represent at least one 0 group.
return nil
}
return ip
}
// ParseIP parses s as an IP address, returning the result.
// The string s can be in IPv4 dotted decimal ("192.0.2.1"), IPv6
// ("2001:db8::68"), or IPv4-mapped IPv6 ("::ffff:192.0.2.1") form.
// If s is not a valid textual representation of an IP address,
// ParseIP returns nil.
func ParseIP(s string) IP {
for i := 0; i < len(s); i++ {
switch s[i] {
case '.':
return parseIPv4(s)
case ':':
return parseIPv6(s)
}
}
return nil
}
// ParseCIDR parses s as a CIDR notation IP address and prefix length,
// like "192.0.2.0/24" or "2001:db8::/32", as defined in
// RFC 4632 and RFC 4291.
//
// It returns the IP address and the network implied by the IP and
// prefix length.
// For example, ParseCIDR("192.0.2.1/24") returns the IP address
// 192.0.2.1 and the network 192.0.2.0/24.
func ParseCIDR(s string) (IP, *IPNet, error) {
i := indexByteString(s, '/')
if i < 0 {
return nil, nil, &ParseError{Type: "CIDR address", Text: s}
}
addr, mask := s[:i], s[i+1:]
iplen := IPv4len
ip := parseIPv4(addr)
if ip == nil {
iplen = IPv6len
ip = parseIPv6(addr)
}
n, i, ok := dtoi(mask)
if ip == nil || !ok || i != len(mask) || n < 0 || n > 8*iplen {
return nil, nil, &ParseError{Type: "CIDR address", Text: s}
}
m := CIDRMask(n, 8*iplen)
return ip, &IPNet{IP: ip.Mask(m), Mask: m}, nil
}
// This is copied from go/src/internal/bytealg, which includes versions
// optimized for various platforms. Those optimizations are elided here so we
// don't have to maintain them.
func indexByteString(s string, c byte) int {
for i := 0; i < len(s); i++ {
if s[i] == c {
return i
}
}
return -1
}