Add support for net.IP

loader/goroot.go

@@ -208,6 +208,7 @@ func pathsToOverride(needsSyscallPackage bool) map[string]bool {
 		"internal/reflectlite/": false,
 		"internal/task/":        false,
 		"machine/":              false,
+		"net/":                  true,
 		"os/":                   true,
 		"reflect/":              false,
 		"runtime/":              false,

src/net/ip.go

@@ -0,0 +1,732 @@
+// The following is copied from Go 1.16 official implementation.
+
+// 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 "internal/bytealg"
+
+// 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 IPMask is a bitmask that can be used to manipulate
+// IP addresses for IP addressing and routing.
+//
+// See type IPNet and func ParseCIDR for details.
+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 {
+	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 && bytealg.Equal(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 bytealg.Equal(ip, x)
+	}
+	if len(ip) == IPv4len && len(x) == IPv6len {
+		return bytealg.Equal(x[0:12], v4InV6Prefix) && bytealg.Equal(ip, x[12:])
+	}
+	if len(ip) == IPv6len && len(x) == IPv4len {
+		return bytealg.Equal(ip[0:12], v4InV6Prefix) && bytealg.Equal(ip[12:], x)
+	}
+	return false
+}
+
+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 "192.0.2.0/24"
+// 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 "198.51.100.0/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
+}
+
+// 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
+}
+
+// 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 := bytealg.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
+}

src/net/ipsock.go

@@ -0,0 +1,98 @@
+// The following is copied from Go 1.16 official implementation.
+
+// 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.
+
+package net
+
+import "internal/bytealg"
+
+// SplitHostPort splits a network address of the form "host:port",
+// "host%zone:port", "[host]:port" or "[host%zone]:port" into host or
+// host%zone and port.
+//
+// A literal IPv6 address in hostport must be enclosed in square
+// brackets, as in "[::1]:80", "[::1%lo0]:80".
+//
+// See func Dial for a description of the hostport parameter, and host
+// and port results.
+func SplitHostPort(hostport string) (host, port string, err error) {
+	const (
+		missingPort   = "missing port in address"
+		tooManyColons = "too many colons in address"
+	)
+	addrErr := func(addr, why string) (host, port string, err error) {
+		return "", "", &AddrError{Err: why, Addr: addr}
+	}
+	j, k := 0, 0
+
+	// The port starts after the last colon.
+	i := last(hostport, ':')
+	if i < 0 {
+		return addrErr(hostport, missingPort)
+	}
+
+	if hostport[0] == '[' {
+		// Expect the first ']' just before the last ':'.
+		end := bytealg.IndexByteString(hostport, ']')
+		if end < 0 {
+			return addrErr(hostport, "missing ']' in address")
+		}
+		switch end + 1 {
+		case len(hostport):
+			// There can't be a ':' behind the ']' now.
+			return addrErr(hostport, missingPort)
+		case i:
+			// The expected result.
+		default:
+			// Either ']' isn't followed by a colon, or it is
+			// followed by a colon that is not the last one.
+			if hostport[end+1] == ':' {
+				return addrErr(hostport, tooManyColons)
+			}
+			return addrErr(hostport, missingPort)
+		}
+		host = hostport[1:end]
+		j, k = 1, end+1 // there can't be a '[' resp. ']' before these positions
+	} else {
+		host = hostport[:i]
+		if bytealg.IndexByteString(host, ':') >= 0 {
+			return addrErr(hostport, tooManyColons)
+		}
+	}
+	if bytealg.IndexByteString(hostport[j:], '[') >= 0 {
+		return addrErr(hostport, "unexpected '[' in address")
+	}
+	if bytealg.IndexByteString(hostport[k:], ']') >= 0 {
+		return addrErr(hostport, "unexpected ']' in address")
+	}
+
+	port = hostport[i+1:]
+	return host, port, nil
+}
+
+func splitHostZone(s string) (host, zone string) {
+	// The IPv6 scoped addressing zone identifier starts after the
+	// last percent sign.
+	if i := last(s, '%'); i > 0 {
+		host, zone = s[:i], s[i+1:]
+	} else {
+		host = s
+	}
+	return
+}
+
+// JoinHostPort combines host and port into a network address of the
+// form "host:port". If host contains a colon, as found in literal
+// IPv6 addresses, then JoinHostPort returns "[host]:port".
+//
+// See func Dial for a description of the host and port parameters.
+func JoinHostPort(host, port string) string {
+	// We assume that host is a literal IPv6 address if host has
+	// colons.
+	if bytealg.IndexByteString(host, ':') >= 0 {
+		return "[" + host + "]:" + port
+	}
+	return host + ":" + port
+}

src/net/mac.go

@@ -0,0 +1,9 @@
+// The following is copied from Go 1.16 official implementation.
+
+// Copyright 2011 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.
+
+package net
+
+const hexDigit = "0123456789abcdef"

src/net/net.go

@@ -0,0 +1,38 @@
+// The following is copied from Go 1.16 official implementation.
+
+// 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.
+
+package net
+
+// A ParseError is the error type of literal network address parsers.
+type ParseError struct {
+	// Type is the type of string that was expected, such as
+	// "IP address", "CIDR address".
+	Type string
+
+	// Text is the malformed text string.
+	Text string
+}
+
+func (e *ParseError) Error() string { return "invalid " + e.Type + ": " + e.Text }
+
+type AddrError struct {
+	Err  string
+	Addr string
+}
+
+func (e *AddrError) Error() string {
+	if e == nil {
+		return "<nil>"
+	}
+	s := e.Err
+	if e.Addr != "" {
+		s = "address " + e.Addr + ": " + s
+	}
+	return s
+}
+
+func (e *AddrError) Timeout() bool   { return false }
+func (e *AddrError) Temporary() bool { return false }

src/net/parse.go

@@ -0,0 +1,96 @@
+// The following is copied from Go 1.16 official implementation.
+
+// 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.
+
+package net
+
+// Bigger than we need, not too big to worry about overflow
+const big = 0xFFFFFF
+
+// Decimal to integer.
+// Returns number, characters consumed, success.
+func dtoi(s string) (n int, i int, ok bool) {
+	n = 0
+	for i = 0; i < len(s) && '0' <= s[i] && s[i] <= '9'; i++ {
+		n = n*10 + int(s[i]-'0')
+		if n >= big {
+			return big, i, false
+		}
+	}
+	if i == 0 {
+		return 0, 0, false
+	}
+	return n, i, true
+}
+
+// Hexadecimal to integer.
+// Returns number, characters consumed, success.
+func xtoi(s string) (n int, i int, ok bool) {
+	n = 0
+	for i = 0; i < len(s); i++ {
+		if '0' <= s[i] && s[i] <= '9' {
+			n *= 16
+			n += int(s[i] - '0')
+		} else if 'a' <= s[i] && s[i] <= 'f' {
+			n *= 16
+			n += int(s[i]-'a') + 10
+		} else if 'A' <= s[i] && s[i] <= 'F' {
+			n *= 16
+			n += int(s[i]-'A') + 10
+		} else {
+			break
+		}
+		if n >= big {
+			return 0, i, false
+		}
+	}
+	if i == 0 {
+		return 0, i, false
+	}
+	return n, i, true
+}
+
+// Convert unsigned integer to decimal string.
+func uitoa(val uint) string {
+	if val == 0 { // avoid string allocation
+		return "0"
+	}
+	var buf [20]byte // big enough for 64bit value base 10
+	i := len(buf) - 1
+	for val >= 10 {
+		q := val / 10
+		buf[i] = byte('0' + val - q*10)
+		i--
+		val = q
+	}
+	// val < 10
+	buf[i] = byte('0' + val)
+	return string(buf[i:])
+}
+
+// Convert i to a hexadecimal string. Leading zeros are not printed.
+func appendHex(dst []byte, i uint32) []byte {
+	if i == 0 {
+		return append(dst, '0')
+	}
+	for j := 7; j >= 0; j-- {
+		v := i >> uint(j*4)
+		if v > 0 {
+			dst = append(dst, hexDigit[v&0xf])
+		}
+	}
+	return dst
+}
+
+// Index of rightmost occurrence of b in s.
+func last(s string, b byte) int {
+	i := len(s)
+	for i--; i >= 0; i-- {
+		if s[i] == b {
+			break
+		}
+	}
+	return i
+}