libgo: update to Go 1.11

[official-gcc.git] / libgo / go / net / ip.go

// 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 net

import _ "unsafe" // for go:linkname

// IP address lengths (bytes).
const (
        IPv4len = 4
        IPv6len = 16
)

// An IP is a single IP address, a slice of bytes.
// Functions in this package accept either 4-byte (IPv4)
// or 16-byte (IPv6) slices 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 slice: a 16-byte slice 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) // limited 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 reports whether ip is an unspecified address, either
// the IPv4 address "0.0.0.0" or the IPv6 address "::".
func (ip IP) IsUnspecified() bool {
        return ip.Equal(IPv4zero) || ip.Equal(IPv6unspecified)
}

// IsLoopback reports whether ip is a loopback address.
func (ip IP) IsLoopback() bool {
        if ip4 := ip.To4(); ip4 != nil {
                return ip4[0] == 127
        }
        return ip.Equal(IPv6loopback)
}

// IsMulticast reports whether ip is a multicast address.
func (ip IP) IsMulticast() bool {
        if ip4 := ip.To4(); ip4 != nil {
                return ip4[0]&0xf0 == 0xe0
        }
        return len(ip) == IPv6len && ip[0] == 0xff
}

// IsInterfaceLocalMulticast reports whether ip is
// an interface-local multicast address.
func (ip IP) IsInterfaceLocalMulticast() bool {
        return len(ip) == IPv6len && ip[0] == 0xff && ip[1]&0x0f == 0x01
}

// IsLinkLocalMulticast reports whether ip is a link-local
// multicast address.
func (ip IP) IsLinkLocalMulticast() bool {
        if ip4 := ip.To4(); ip4 != nil {
                return ip4[0] == 224 && ip4[1] == 0 && ip4[2] == 0
        }
        return len(ip) == IPv6len && ip[0] == 0xff && ip[1]&0x0f == 0x02
}

// IsLinkLocalUnicast reports whether ip is a link-local
// unicast address.
func (ip IP) IsLinkLocalUnicast() bool {
        if ip4 := ip.To4(); ip4 != nil {
                return ip4[0] == 169 && ip4[1] == 254
        }
        return len(ip) == IPv6len && ip[0] == 0xfe && ip[1]&0xc0 == 0x80
}

// IsGlobalUnicast reports whether ip is a global unicast
// address.
//
// The identification of global unicast addresses uses address type
// identification as defined in RFC 1122, RFC 4632 and RFC 4291 with
// the exception of IPv4 directed broadcast addresses.
// It returns true even if ip is in IPv4 private address space or
// local IPv6 unicast address space.
func (ip IP) IsGlobalUnicast() bool {
        return (len(ip) == IPv4len || len(ip) == IPv6len) &&
                !ip.Equal(IPv4bcast) &&
                !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
        }
}

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
}

// ubtoa encodes the string form of the integer v to dst[start:] and
// returns the number of bytes written to dst. The caller must ensure
// that dst has sufficient length.
func ubtoa(dst []byte, start int, v byte) int {
        if v < 10 {
                dst[start] = v + '0'
                return 1
        } else if v < 100 {
                dst[start+1] = v%10 + '0'
                dst[start] = v/10 + '0'
                return 2
        }

        dst[start+2] = v%10 + '0'
        dst[start+1] = (v/10)%10 + '0'
        dst[start] = v/100 + '0'
        return 3
}

// String returns the string form of the IP address ip.
// It returns one of 4 forms:
//   - "<nil>", if ip has length 0
//   - dotted decimal ("192.0.2.1"), if ip is an IPv4 or IP4-mapped IPv6 address
//   - IPv6 ("2001:db8::1"), if ip is a valid IPv6 address
//   - the hexadecimal form of ip, without punctuation, if no other cases apply
func (ip IP) String() string {
        p := ip

        if len(ip) == 0 {
                return "<nil>"
        }

        // If IPv4, use dotted notation.
        if p4 := p.To4(); len(p4) == IPv4len {
                const maxIPv4StringLen = len("255.255.255.255")
                b := make([]byte, maxIPv4StringLen)

                n := ubtoa(b, 0, p4[0])
                b[n] = '.'
                n++

                n += ubtoa(b, n, p4[1])
                b[n] = '.'
                n++

                n += ubtoa(b, n, p4[2])
                b[n] = '.'
                n++

                n += ubtoa(b, n, p4[3])
                return string(b[:n])
        }
        if len(p) != IPv6len {
                return "?" + hexString(ip)
        }

        // 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
                        i = j
                }
        }
        // The symbol "::" MUST NOT be used to shorten just one 16 bit 0 field.
        if e1-e0 <= 2 {
                e0 = -1
                e1 = -1
        }

        const maxLen = len("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff")
        b := make([]byte, 0, maxLen)

        // Print with possible :: in place of run of zeros
        for i := 0; i < IPv6len; i += 2 {
                if i == e0 {
                        b = append(b, ':', ':')
                        i = e1
                        if i >= IPv6len {
                                break
                        }
                } else if i > 0 {
                        b = append(b, ':')
                }
                b = appendHex(b, (uint32(p[i])<<8)|uint32(p[i+1]))
        }
        return string(b)
}

func hexString(b []byte) string {
        s := make([]byte, len(b)*2)
        for i, tn := range b {
                s[i*2], s[i*2+1] = hexDigit[tn>>4], hexDigit[tn&0xf]
        }
        return string(s)
}

// ipEmptyString is like ip.String except that it returns
// an empty string when ip is unset.
func ipEmptyString(ip IP) string {
        if len(ip) == 0 {
                return ""
        }
        return ip.String()
}

// MarshalText implements the encoding.TextMarshaler interface.
// The encoding is the same as returned by String, with one exception:
// When len(ip) is zero, it returns an empty slice.
func (ip IP) MarshalText() ([]byte, error) {
        if len(ip) == 0 {
                return []byte(""), nil
        }
        if len(ip) != IPv4len && len(ip) != IPv6len {
                return nil, &AddrError{Err: "invalid IP address", Addr: hexString(ip)}
        }
        return []byte(ip.String()), nil
}

// UnmarshalText implements the encoding.TextUnmarshaler interface.
// The IP address is expected in a form accepted by ParseIP.
func (ip *IP) UnmarshalText(text []byte) error {
        if len(text) == 0 {
                *ip = nil
                return nil
        }
        s := string(text)
        x := ParseIP(s)
        if x == nil {
                return &ParseError{Type: "IP address", Text: s}
        }
        *ip = x
        return nil
}

// Equal reports whether 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
}

// bytes.Equal is implemented in runtime/asm_$goarch.s
//go:linkname bytesEqual bytes.Equal
func bytesEqual(x, y []byte) bool

func (ip IP) matchAddrFamily(x IP) bool {
        return ip.To4() != nil && x.To4() != nil || ip.To16() != nil && ip.To4() == nil && x.To16() != nil && x.To4() == nil
}

// 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 {
        if len(m) == 0 {
                return "<nil>"
        }
        return hexString(m)
}

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
}

// Network returns the address's network name, "ip+net".
func (n *IPNet) Network() string { return "ip+net" }

// String returns the CIDR notation of n like "192.0.2.1/24"
// 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 "198.51.100.1/c000ff00".
func (n *IPNet) String() string {
        nn, m := networkNumberAndMask(n)
        if nn == nil || m == nil {
                return "<nil>"
        }
        l := simpleMaskLength(m)
        if l == -1 {
                return nn.String() + "/" + m.String()
        }
        return nn.String() + "/" + uitoa(uint(l))
}

// 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
                }
                s = s[c:]
                p[i] = byte(n)
        }
        if len(s) != 0 {
                return nil
        }
        return IPv4(p[0], p[1], p[2], p[3])
}

// parseIPv6Zone parses s as a literal IPv6 address and its associated zone
// identifier which is described in RFC 4007.
func parseIPv6Zone(s string) (IP, string) {
        s, zone := splitHostZone(s)
        return parseIPv6(s), zone
}

// parseIPv6Zone 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 dotted decimal ("192.0.2.1")
// or IPv6 ("2001:db8::68") 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
}

// parseIPZone parses s as an IP address, return it and its associated zone
// identifier (IPv6 only).
func parseIPZone(s string) (IP, string) {
        for i := 0; i < len(s); i++ {
                switch s[i] {
                case '.':
                        return parseIPv4(s), ""
                case ':':
                        return parseIPv6Zone(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 := byteIndex(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
}