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Source file src/net/netip/netip.go

Documentation: net/netip

     1  // Copyright 2020 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Package netip defines an IP address type that's a small value type.
     6  // Building on that [Addr] type, the package also defines [AddrPort] (an
     7  // IP address and a port) and [Prefix] (an IP address and a bit length
     8  // prefix).
     9  //
    10  // Compared to the [net.IP] type, [Addr] type takes less memory, is immutable,
    11  // and is comparable (supports == and being a map key).
    12  package netip
    13  
    14  import (
    15  	"cmp"
    16  	"errors"
    17  	"math"
    18  	"strconv"
    19  
    20  	"internal/bytealg"
    21  	"internal/intern"
    22  	"internal/itoa"
    23  )
    24  
    25  // Sizes: (64-bit)
    26  //   net.IP:     24 byte slice header + {4, 16} = 28 to 40 bytes
    27  //   net.IPAddr: 40 byte slice header + {4, 16} = 44 to 56 bytes + zone length
    28  //   netip.Addr: 24 bytes (zone is per-name singleton, shared across all users)
    29  
    30  // Addr represents an IPv4 or IPv6 address (with or without a scoped
    31  // addressing zone), similar to [net.IP] or [net.IPAddr].
    32  //
    33  // Unlike [net.IP] or [net.IPAddr], Addr is a comparable value
    34  // type (it supports == and can be a map key) and is immutable.
    35  //
    36  // The zero Addr is not a valid IP address.
    37  // Addr{} is distinct from both 0.0.0.0 and ::.
    38  type Addr struct {
    39  	// addr is the hi and lo bits of an IPv6 address. If z==z4,
    40  	// hi and lo contain the IPv4-mapped IPv6 address.
    41  	//
    42  	// hi and lo are constructed by interpreting a 16-byte IPv6
    43  	// address as a big-endian 128-bit number. The most significant
    44  	// bits of that number go into hi, the rest into lo.
    45  	//
    46  	// For example, 0011:2233:4455:6677:8899:aabb:ccdd:eeff is stored as:
    47  	//  addr.hi = 0x0011223344556677
    48  	//  addr.lo = 0x8899aabbccddeeff
    49  	//
    50  	// We store IPs like this, rather than as [16]byte, because it
    51  	// turns most operations on IPs into arithmetic and bit-twiddling
    52  	// operations on 64-bit registers, which is much faster than
    53  	// bytewise processing.
    54  	addr uint128
    55  
    56  	// z is a combination of the address family and the IPv6 zone.
    57  	//
    58  	// nil means invalid IP address (for a zero Addr).
    59  	// z4 means an IPv4 address.
    60  	// z6noz means an IPv6 address without a zone.
    61  	//
    62  	// Otherwise it's the interned zone name string.
    63  	z *intern.Value
    64  }
    65  
    66  // z0, z4, and z6noz are sentinel Addr.z values.
    67  // See the Addr type's field docs.
    68  var (
    69  	z0    = (*intern.Value)(nil)
    70  	z4    = new(intern.Value)
    71  	z6noz = new(intern.Value)
    72  )
    73  
    74  // IPv6LinkLocalAllNodes returns the IPv6 link-local all nodes multicast
    75  // address ff02::1.
    76  func IPv6LinkLocalAllNodes() Addr { return AddrFrom16([16]byte{0: 0xff, 1: 0x02, 15: 0x01}) }
    77  
    78  // IPv6LinkLocalAllRouters returns the IPv6 link-local all routers multicast
    79  // address ff02::2.
    80  func IPv6LinkLocalAllRouters() Addr { return AddrFrom16([16]byte{0: 0xff, 1: 0x02, 15: 0x02}) }
    81  
    82  // IPv6Loopback returns the IPv6 loopback address ::1.
    83  func IPv6Loopback() Addr { return AddrFrom16([16]byte{15: 0x01}) }
    84  
    85  // IPv6Unspecified returns the IPv6 unspecified address "::".
    86  func IPv6Unspecified() Addr { return Addr{z: z6noz} }
    87  
    88  // IPv4Unspecified returns the IPv4 unspecified address "0.0.0.0".
    89  func IPv4Unspecified() Addr { return AddrFrom4([4]byte{}) }
    90  
    91  // AddrFrom4 returns the address of the IPv4 address given by the bytes in addr.
    92  func AddrFrom4(addr [4]byte) Addr {
    93  	return Addr{
    94  		addr: uint128{0, 0xffff00000000 | uint64(addr[0])<<24 | uint64(addr[1])<<16 | uint64(addr[2])<<8 | uint64(addr[3])},
    95  		z:    z4,
    96  	}
    97  }
    98  
    99  // AddrFrom16 returns the IPv6 address given by the bytes in addr.
   100  // An IPv4-mapped IPv6 address is left as an IPv6 address.
   101  // (Use Unmap to convert them if needed.)
   102  func AddrFrom16(addr [16]byte) Addr {
   103  	return Addr{
   104  		addr: uint128{
   105  			beUint64(addr[:8]),
   106  			beUint64(addr[8:]),
   107  		},
   108  		z: z6noz,
   109  	}
   110  }
   111  
   112  // ParseAddr parses s as an IP address, returning the result. The string
   113  // s can be in dotted decimal ("192.0.2.1"), IPv6 ("2001:db8::68"),
   114  // or IPv6 with a scoped addressing zone ("fe80::1cc0:3e8c:119f:c2e1%ens18").
   115  func ParseAddr(s string) (Addr, error) {
   116  	for i := 0; i < len(s); i++ {
   117  		switch s[i] {
   118  		case '.':
   119  			return parseIPv4(s)
   120  		case ':':
   121  			return parseIPv6(s)
   122  		case '%':
   123  			// Assume that this was trying to be an IPv6 address with
   124  			// a zone specifier, but the address is missing.
   125  			return Addr{}, parseAddrError{in: s, msg: "missing IPv6 address"}
   126  		}
   127  	}
   128  	return Addr{}, parseAddrError{in: s, msg: "unable to parse IP"}
   129  }
   130  
   131  // MustParseAddr calls [ParseAddr](s) and panics on error.
   132  // It is intended for use in tests with hard-coded strings.
   133  func MustParseAddr(s string) Addr {
   134  	ip, err := ParseAddr(s)
   135  	if err != nil {
   136  		panic(err)
   137  	}
   138  	return ip
   139  }
   140  
   141  type parseAddrError struct {
   142  	in  string // the string given to ParseAddr
   143  	msg string // an explanation of the parse failure
   144  	at  string // optionally, the unparsed portion of in at which the error occurred.
   145  }
   146  
   147  func (err parseAddrError) Error() string {
   148  	q := strconv.Quote
   149  	if err.at != "" {
   150  		return "ParseAddr(" + q(err.in) + "): " + err.msg + " (at " + q(err.at) + ")"
   151  	}
   152  	return "ParseAddr(" + q(err.in) + "): " + err.msg
   153  }
   154  
   155  // parseIPv4 parses s as an IPv4 address (in form "192.168.0.1").
   156  func parseIPv4(s string) (ip Addr, err error) {
   157  	var fields [4]uint8
   158  	var val, pos int
   159  	var digLen int // number of digits in current octet
   160  	for i := 0; i < len(s); i++ {
   161  		if s[i] >= '0' && s[i] <= '9' {
   162  			if digLen == 1 && val == 0 {
   163  				return Addr{}, parseAddrError{in: s, msg: "IPv4 field has octet with leading zero"}
   164  			}
   165  			val = val*10 + int(s[i]) - '0'
   166  			digLen++
   167  			if val > 255 {
   168  				return Addr{}, parseAddrError{in: s, msg: "IPv4 field has value >255"}
   169  			}
   170  		} else if s[i] == '.' {
   171  			// .1.2.3
   172  			// 1.2.3.
   173  			// 1..2.3
   174  			if i == 0 || i == len(s)-1 || s[i-1] == '.' {
   175  				return Addr{}, parseAddrError{in: s, msg: "IPv4 field must have at least one digit", at: s[i:]}
   176  			}
   177  			// 1.2.3.4.5
   178  			if pos == 3 {
   179  				return Addr{}, parseAddrError{in: s, msg: "IPv4 address too long"}
   180  			}
   181  			fields[pos] = uint8(val)
   182  			pos++
   183  			val = 0
   184  			digLen = 0
   185  		} else {
   186  			return Addr{}, parseAddrError{in: s, msg: "unexpected character", at: s[i:]}
   187  		}
   188  	}
   189  	if pos < 3 {
   190  		return Addr{}, parseAddrError{in: s, msg: "IPv4 address too short"}
   191  	}
   192  	fields[3] = uint8(val)
   193  	return AddrFrom4(fields), nil
   194  }
   195  
   196  // parseIPv6 parses s as an IPv6 address (in form "2001:db8::68").
   197  func parseIPv6(in string) (Addr, error) {
   198  	s := in
   199  
   200  	// Split off the zone right from the start. Yes it's a second scan
   201  	// of the string, but trying to handle it inline makes a bunch of
   202  	// other inner loop conditionals more expensive, and it ends up
   203  	// being slower.
   204  	zone := ""
   205  	i := bytealg.IndexByteString(s, '%')
   206  	if i != -1 {
   207  		s, zone = s[:i], s[i+1:]
   208  		if zone == "" {
   209  			// Not allowed to have an empty zone if explicitly specified.
   210  			return Addr{}, parseAddrError{in: in, msg: "zone must be a non-empty string"}
   211  		}
   212  	}
   213  
   214  	var ip [16]byte
   215  	ellipsis := -1 // position of ellipsis in ip
   216  
   217  	// Might have leading ellipsis
   218  	if len(s) >= 2 && s[0] == ':' && s[1] == ':' {
   219  		ellipsis = 0
   220  		s = s[2:]
   221  		// Might be only ellipsis
   222  		if len(s) == 0 {
   223  			return IPv6Unspecified().WithZone(zone), nil
   224  		}
   225  	}
   226  
   227  	// Loop, parsing hex numbers followed by colon.
   228  	i = 0
   229  	for i < 16 {
   230  		// Hex number. Similar to parseIPv4, inlining the hex number
   231  		// parsing yields a significant performance increase.
   232  		off := 0
   233  		acc := uint32(0)
   234  		for ; off < len(s); off++ {
   235  			c := s[off]
   236  			if c >= '0' && c <= '9' {
   237  				acc = (acc << 4) + uint32(c-'0')
   238  			} else if c >= 'a' && c <= 'f' {
   239  				acc = (acc << 4) + uint32(c-'a'+10)
   240  			} else if c >= 'A' && c <= 'F' {
   241  				acc = (acc << 4) + uint32(c-'A'+10)
   242  			} else {
   243  				break
   244  			}
   245  			if acc > math.MaxUint16 {
   246  				// Overflow, fail.
   247  				return Addr{}, parseAddrError{in: in, msg: "IPv6 field has value >=2^16", at: s}
   248  			}
   249  		}
   250  		if off == 0 {
   251  			// No digits found, fail.
   252  			return Addr{}, parseAddrError{in: in, msg: "each colon-separated field must have at least one digit", at: s}
   253  		}
   254  
   255  		// If followed by dot, might be in trailing IPv4.
   256  		if off < len(s) && s[off] == '.' {
   257  			if ellipsis < 0 && i != 12 {
   258  				// Not the right place.
   259  				return Addr{}, parseAddrError{in: in, msg: "embedded IPv4 address must replace the final 2 fields of the address", at: s}
   260  			}
   261  			if i+4 > 16 {
   262  				// Not enough room.
   263  				return Addr{}, parseAddrError{in: in, msg: "too many hex fields to fit an embedded IPv4 at the end of the address", at: s}
   264  			}
   265  			// TODO: could make this a bit faster by having a helper
   266  			// that parses to a [4]byte, and have both parseIPv4 and
   267  			// parseIPv6 use it.
   268  			ip4, err := parseIPv4(s)
   269  			if err != nil {
   270  				return Addr{}, parseAddrError{in: in, msg: err.Error(), at: s}
   271  			}
   272  			ip[i] = ip4.v4(0)
   273  			ip[i+1] = ip4.v4(1)
   274  			ip[i+2] = ip4.v4(2)
   275  			ip[i+3] = ip4.v4(3)
   276  			s = ""
   277  			i += 4
   278  			break
   279  		}
   280  
   281  		// Save this 16-bit chunk.
   282  		ip[i] = byte(acc >> 8)
   283  		ip[i+1] = byte(acc)
   284  		i += 2
   285  
   286  		// Stop at end of string.
   287  		s = s[off:]
   288  		if len(s) == 0 {
   289  			break
   290  		}
   291  
   292  		// Otherwise must be followed by colon and more.
   293  		if s[0] != ':' {
   294  			return Addr{}, parseAddrError{in: in, msg: "unexpected character, want colon", at: s}
   295  		} else if len(s) == 1 {
   296  			return Addr{}, parseAddrError{in: in, msg: "colon must be followed by more characters", at: s}
   297  		}
   298  		s = s[1:]
   299  
   300  		// Look for ellipsis.
   301  		if s[0] == ':' {
   302  			if ellipsis >= 0 { // already have one
   303  				return Addr{}, parseAddrError{in: in, msg: "multiple :: in address", at: s}
   304  			}
   305  			ellipsis = i
   306  			s = s[1:]
   307  			if len(s) == 0 { // can be at end
   308  				break
   309  			}
   310  		}
   311  	}
   312  
   313  	// Must have used entire string.
   314  	if len(s) != 0 {
   315  		return Addr{}, parseAddrError{in: in, msg: "trailing garbage after address", at: s}
   316  	}
   317  
   318  	// If didn't parse enough, expand ellipsis.
   319  	if i < 16 {
   320  		if ellipsis < 0 {
   321  			return Addr{}, parseAddrError{in: in, msg: "address string too short"}
   322  		}
   323  		n := 16 - i
   324  		for j := i - 1; j >= ellipsis; j-- {
   325  			ip[j+n] = ip[j]
   326  		}
   327  		for j := ellipsis + n - 1; j >= ellipsis; j-- {
   328  			ip[j] = 0
   329  		}
   330  	} else if ellipsis >= 0 {
   331  		// Ellipsis must represent at least one 0 group.
   332  		return Addr{}, parseAddrError{in: in, msg: "the :: must expand to at least one field of zeros"}
   333  	}
   334  	return AddrFrom16(ip).WithZone(zone), nil
   335  }
   336  
   337  // AddrFromSlice parses the 4- or 16-byte byte slice as an IPv4 or IPv6 address.
   338  // Note that a [net.IP] can be passed directly as the []byte argument.
   339  // If slice's length is not 4 or 16, AddrFromSlice returns [Addr]{}, false.
   340  func AddrFromSlice(slice []byte) (ip Addr, ok bool) {
   341  	switch len(slice) {
   342  	case 4:
   343  		return AddrFrom4([4]byte(slice)), true
   344  	case 16:
   345  		return AddrFrom16([16]byte(slice)), true
   346  	}
   347  	return Addr{}, false
   348  }
   349  
   350  // v4 returns the i'th byte of ip. If ip is not an IPv4, v4 returns
   351  // unspecified garbage.
   352  func (ip Addr) v4(i uint8) uint8 {
   353  	return uint8(ip.addr.lo >> ((3 - i) * 8))
   354  }
   355  
   356  // v6 returns the i'th byte of ip. If ip is an IPv4 address, this
   357  // accesses the IPv4-mapped IPv6 address form of the IP.
   358  func (ip Addr) v6(i uint8) uint8 {
   359  	return uint8(*(ip.addr.halves()[(i/8)%2]) >> ((7 - i%8) * 8))
   360  }
   361  
   362  // v6u16 returns the i'th 16-bit word of ip. If ip is an IPv4 address,
   363  // this accesses the IPv4-mapped IPv6 address form of the IP.
   364  func (ip Addr) v6u16(i uint8) uint16 {
   365  	return uint16(*(ip.addr.halves()[(i/4)%2]) >> ((3 - i%4) * 16))
   366  }
   367  
   368  // isZero reports whether ip is the zero value of the IP type.
   369  // The zero value is not a valid IP address of any type.
   370  //
   371  // Note that "0.0.0.0" and "::" are not the zero value. Use IsUnspecified to
   372  // check for these values instead.
   373  func (ip Addr) isZero() bool {
   374  	// Faster than comparing ip == Addr{}, but effectively equivalent,
   375  	// as there's no way to make an IP with a nil z from this package.
   376  	return ip.z == z0
   377  }
   378  
   379  // IsValid reports whether the [Addr] is an initialized address (not the zero Addr).
   380  //
   381  // Note that "0.0.0.0" and "::" are both valid values.
   382  func (ip Addr) IsValid() bool { return ip.z != z0 }
   383  
   384  // BitLen returns the number of bits in the IP address:
   385  // 128 for IPv6, 32 for IPv4, and 0 for the zero [Addr].
   386  //
   387  // Note that IPv4-mapped IPv6 addresses are considered IPv6 addresses
   388  // and therefore have bit length 128.
   389  func (ip Addr) BitLen() int {
   390  	switch ip.z {
   391  	case z0:
   392  		return 0
   393  	case z4:
   394  		return 32
   395  	}
   396  	return 128
   397  }
   398  
   399  // Zone returns ip's IPv6 scoped addressing zone, if any.
   400  func (ip Addr) Zone() string {
   401  	if ip.z == nil {
   402  		return ""
   403  	}
   404  	zone, _ := ip.z.Get().(string)
   405  	return zone
   406  }
   407  
   408  // Compare returns an integer comparing two IPs.
   409  // The result will be 0 if ip == ip2, -1 if ip < ip2, and +1 if ip > ip2.
   410  // The definition of "less than" is the same as the [Addr.Less] method.
   411  func (ip Addr) Compare(ip2 Addr) int {
   412  	f1, f2 := ip.BitLen(), ip2.BitLen()
   413  	if f1 < f2 {
   414  		return -1
   415  	}
   416  	if f1 > f2 {
   417  		return 1
   418  	}
   419  	hi1, hi2 := ip.addr.hi, ip2.addr.hi
   420  	if hi1 < hi2 {
   421  		return -1
   422  	}
   423  	if hi1 > hi2 {
   424  		return 1
   425  	}
   426  	lo1, lo2 := ip.addr.lo, ip2.addr.lo
   427  	if lo1 < lo2 {
   428  		return -1
   429  	}
   430  	if lo1 > lo2 {
   431  		return 1
   432  	}
   433  	if ip.Is6() {
   434  		za, zb := ip.Zone(), ip2.Zone()
   435  		if za < zb {
   436  			return -1
   437  		}
   438  		if za > zb {
   439  			return 1
   440  		}
   441  	}
   442  	return 0
   443  }
   444  
   445  // Less reports whether ip sorts before ip2.
   446  // IP addresses sort first by length, then their address.
   447  // IPv6 addresses with zones sort just after the same address without a zone.
   448  func (ip Addr) Less(ip2 Addr) bool { return ip.Compare(ip2) == -1 }
   449  
   450  // Is4 reports whether ip is an IPv4 address.
   451  //
   452  // It returns false for IPv4-mapped IPv6 addresses. See [Addr.Unmap].
   453  func (ip Addr) Is4() bool {
   454  	return ip.z == z4
   455  }
   456  
   457  // Is4In6 reports whether ip is an IPv4-mapped IPv6 address.
   458  func (ip Addr) Is4In6() bool {
   459  	return ip.Is6() && ip.addr.hi == 0 && ip.addr.lo>>32 == 0xffff
   460  }
   461  
   462  // Is6 reports whether ip is an IPv6 address, including IPv4-mapped
   463  // IPv6 addresses.
   464  func (ip Addr) Is6() bool {
   465  	return ip.z != z0 && ip.z != z4
   466  }
   467  
   468  // Unmap returns ip with any IPv4-mapped IPv6 address prefix removed.
   469  //
   470  // That is, if ip is an IPv6 address wrapping an IPv4 address, it
   471  // returns the wrapped IPv4 address. Otherwise it returns ip unmodified.
   472  func (ip Addr) Unmap() Addr {
   473  	if ip.Is4In6() {
   474  		ip.z = z4
   475  	}
   476  	return ip
   477  }
   478  
   479  // WithZone returns an IP that's the same as ip but with the provided
   480  // zone. If zone is empty, the zone is removed. If ip is an IPv4
   481  // address, WithZone is a no-op and returns ip unchanged.
   482  func (ip Addr) WithZone(zone string) Addr {
   483  	if !ip.Is6() {
   484  		return ip
   485  	}
   486  	if zone == "" {
   487  		ip.z = z6noz
   488  		return ip
   489  	}
   490  	ip.z = intern.GetByString(zone)
   491  	return ip
   492  }
   493  
   494  // withoutZone unconditionally strips the zone from ip.
   495  // It's similar to WithZone, but small enough to be inlinable.
   496  func (ip Addr) withoutZone() Addr {
   497  	if !ip.Is6() {
   498  		return ip
   499  	}
   500  	ip.z = z6noz
   501  	return ip
   502  }
   503  
   504  // hasZone reports whether ip has an IPv6 zone.
   505  func (ip Addr) hasZone() bool {
   506  	return ip.z != z0 && ip.z != z4 && ip.z != z6noz
   507  }
   508  
   509  // IsLinkLocalUnicast reports whether ip is a link-local unicast address.
   510  func (ip Addr) IsLinkLocalUnicast() bool {
   511  	// Dynamic Configuration of IPv4 Link-Local Addresses
   512  	// https://datatracker.ietf.org/doc/html/rfc3927#section-2.1
   513  	if ip.Is4() {
   514  		return ip.v4(0) == 169 && ip.v4(1) == 254
   515  	}
   516  	// IP Version 6 Addressing Architecture (2.4 Address Type Identification)
   517  	// https://datatracker.ietf.org/doc/html/rfc4291#section-2.4
   518  	if ip.Is6() {
   519  		return ip.v6u16(0)&0xffc0 == 0xfe80
   520  	}
   521  	return false // zero value
   522  }
   523  
   524  // IsLoopback reports whether ip is a loopback address.
   525  func (ip Addr) IsLoopback() bool {
   526  	// Requirements for Internet Hosts -- Communication Layers (3.2.1.3 Addressing)
   527  	// https://datatracker.ietf.org/doc/html/rfc1122#section-3.2.1.3
   528  	if ip.Is4() {
   529  		return ip.v4(0) == 127
   530  	}
   531  	// IP Version 6 Addressing Architecture (2.4 Address Type Identification)
   532  	// https://datatracker.ietf.org/doc/html/rfc4291#section-2.4
   533  	if ip.Is6() {
   534  		return ip.addr.hi == 0 && ip.addr.lo == 1
   535  	}
   536  	return false // zero value
   537  }
   538  
   539  // IsMulticast reports whether ip is a multicast address.
   540  func (ip Addr) IsMulticast() bool {
   541  	// Host Extensions for IP Multicasting (4. HOST GROUP ADDRESSES)
   542  	// https://datatracker.ietf.org/doc/html/rfc1112#section-4
   543  	if ip.Is4() {
   544  		return ip.v4(0)&0xf0 == 0xe0
   545  	}
   546  	// IP Version 6 Addressing Architecture (2.4 Address Type Identification)
   547  	// https://datatracker.ietf.org/doc/html/rfc4291#section-2.4
   548  	if ip.Is6() {
   549  		return ip.addr.hi>>(64-8) == 0xff // ip.v6(0) == 0xff
   550  	}
   551  	return false // zero value
   552  }
   553  
   554  // IsInterfaceLocalMulticast reports whether ip is an IPv6 interface-local
   555  // multicast address.
   556  func (ip Addr) IsInterfaceLocalMulticast() bool {
   557  	// IPv6 Addressing Architecture (2.7.1. Pre-Defined Multicast Addresses)
   558  	// https://datatracker.ietf.org/doc/html/rfc4291#section-2.7.1
   559  	if ip.Is6() {
   560  		return ip.v6u16(0)&0xff0f == 0xff01
   561  	}
   562  	return false // zero value
   563  }
   564  
   565  // IsLinkLocalMulticast reports whether ip is a link-local multicast address.
   566  func (ip Addr) IsLinkLocalMulticast() bool {
   567  	// IPv4 Multicast Guidelines (4. Local Network Control Block (224.0.0/24))
   568  	// https://datatracker.ietf.org/doc/html/rfc5771#section-4
   569  	if ip.Is4() {
   570  		return ip.v4(0) == 224 && ip.v4(1) == 0 && ip.v4(2) == 0
   571  	}
   572  	// IPv6 Addressing Architecture (2.7.1. Pre-Defined Multicast Addresses)
   573  	// https://datatracker.ietf.org/doc/html/rfc4291#section-2.7.1
   574  	if ip.Is6() {
   575  		return ip.v6u16(0)&0xff0f == 0xff02
   576  	}
   577  	return false // zero value
   578  }
   579  
   580  // IsGlobalUnicast reports whether ip is a global unicast address.
   581  //
   582  // It returns true for IPv6 addresses which fall outside of the current
   583  // IANA-allocated 2000::/3 global unicast space, with the exception of the
   584  // link-local address space. It also returns true even if ip is in the IPv4
   585  // private address space or IPv6 unique local address space.
   586  // It returns false for the zero [Addr].
   587  //
   588  // For reference, see RFC 1122, RFC 4291, and RFC 4632.
   589  func (ip Addr) IsGlobalUnicast() bool {
   590  	if ip.z == z0 {
   591  		// Invalid or zero-value.
   592  		return false
   593  	}
   594  
   595  	// Match package net's IsGlobalUnicast logic. Notably private IPv4 addresses
   596  	// and ULA IPv6 addresses are still considered "global unicast".
   597  	if ip.Is4() && (ip == IPv4Unspecified() || ip == AddrFrom4([4]byte{255, 255, 255, 255})) {
   598  		return false
   599  	}
   600  
   601  	return ip != IPv6Unspecified() &&
   602  		!ip.IsLoopback() &&
   603  		!ip.IsMulticast() &&
   604  		!ip.IsLinkLocalUnicast()
   605  }
   606  
   607  // IsPrivate reports whether ip is a private address, according to RFC 1918
   608  // (IPv4 addresses) and RFC 4193 (IPv6 addresses). That is, it reports whether
   609  // ip is in 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, or fc00::/7. This is the
   610  // same as [net.IP.IsPrivate].
   611  func (ip Addr) IsPrivate() bool {
   612  	// Match the stdlib's IsPrivate logic.
   613  	if ip.Is4() {
   614  		// RFC 1918 allocates 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 as
   615  		// private IPv4 address subnets.
   616  		return ip.v4(0) == 10 ||
   617  			(ip.v4(0) == 172 && ip.v4(1)&0xf0 == 16) ||
   618  			(ip.v4(0) == 192 && ip.v4(1) == 168)
   619  	}
   620  
   621  	if ip.Is6() {
   622  		// RFC 4193 allocates fc00::/7 as the unique local unicast IPv6 address
   623  		// subnet.
   624  		return ip.v6(0)&0xfe == 0xfc
   625  	}
   626  
   627  	return false // zero value
   628  }
   629  
   630  // IsUnspecified reports whether ip is an unspecified address, either the IPv4
   631  // address "0.0.0.0" or the IPv6 address "::".
   632  //
   633  // Note that the zero [Addr] is not an unspecified address.
   634  func (ip Addr) IsUnspecified() bool {
   635  	return ip == IPv4Unspecified() || ip == IPv6Unspecified()
   636  }
   637  
   638  // Prefix keeps only the top b bits of IP, producing a Prefix
   639  // of the specified length.
   640  // If ip is a zero [Addr], Prefix always returns a zero Prefix and a nil error.
   641  // Otherwise, if bits is less than zero or greater than ip.BitLen(),
   642  // Prefix returns an error.
   643  func (ip Addr) Prefix(b int) (Prefix, error) {
   644  	if b < 0 {
   645  		return Prefix{}, errors.New("negative Prefix bits")
   646  	}
   647  	effectiveBits := b
   648  	switch ip.z {
   649  	case z0:
   650  		return Prefix{}, nil
   651  	case z4:
   652  		if b > 32 {
   653  			return Prefix{}, errors.New("prefix length " + itoa.Itoa(b) + " too large for IPv4")
   654  		}
   655  		effectiveBits += 96
   656  	default:
   657  		if b > 128 {
   658  			return Prefix{}, errors.New("prefix length " + itoa.Itoa(b) + " too large for IPv6")
   659  		}
   660  	}
   661  	ip.addr = ip.addr.and(mask6(effectiveBits))
   662  	return PrefixFrom(ip, b), nil
   663  }
   664  
   665  // As16 returns the IP address in its 16-byte representation.
   666  // IPv4 addresses are returned as IPv4-mapped IPv6 addresses.
   667  // IPv6 addresses with zones are returned without their zone (use the
   668  // [Addr.Zone] method to get it).
   669  // The ip zero value returns all zeroes.
   670  func (ip Addr) As16() (a16 [16]byte) {
   671  	bePutUint64(a16[:8], ip.addr.hi)
   672  	bePutUint64(a16[8:], ip.addr.lo)
   673  	return a16
   674  }
   675  
   676  // As4 returns an IPv4 or IPv4-in-IPv6 address in its 4-byte representation.
   677  // If ip is the zero [Addr] or an IPv6 address, As4 panics.
   678  // Note that 0.0.0.0 is not the zero Addr.
   679  func (ip Addr) As4() (a4 [4]byte) {
   680  	if ip.z == z4 || ip.Is4In6() {
   681  		bePutUint32(a4[:], uint32(ip.addr.lo))
   682  		return a4
   683  	}
   684  	if ip.z == z0 {
   685  		panic("As4 called on IP zero value")
   686  	}
   687  	panic("As4 called on IPv6 address")
   688  }
   689  
   690  // AsSlice returns an IPv4 or IPv6 address in its respective 4-byte or 16-byte representation.
   691  func (ip Addr) AsSlice() []byte {
   692  	switch ip.z {
   693  	case z0:
   694  		return nil
   695  	case z4:
   696  		var ret [4]byte
   697  		bePutUint32(ret[:], uint32(ip.addr.lo))
   698  		return ret[:]
   699  	default:
   700  		var ret [16]byte
   701  		bePutUint64(ret[:8], ip.addr.hi)
   702  		bePutUint64(ret[8:], ip.addr.lo)
   703  		return ret[:]
   704  	}
   705  }
   706  
   707  // Next returns the address following ip.
   708  // If there is none, it returns the zero [Addr].
   709  func (ip Addr) Next() Addr {
   710  	ip.addr = ip.addr.addOne()
   711  	if ip.Is4() {
   712  		if uint32(ip.addr.lo) == 0 {
   713  			// Overflowed.
   714  			return Addr{}
   715  		}
   716  	} else {
   717  		if ip.addr.isZero() {
   718  			// Overflowed
   719  			return Addr{}
   720  		}
   721  	}
   722  	return ip
   723  }
   724  
   725  // Prev returns the IP before ip.
   726  // If there is none, it returns the IP zero value.
   727  func (ip Addr) Prev() Addr {
   728  	if ip.Is4() {
   729  		if uint32(ip.addr.lo) == 0 {
   730  			return Addr{}
   731  		}
   732  	} else if ip.addr.isZero() {
   733  		return Addr{}
   734  	}
   735  	ip.addr = ip.addr.subOne()
   736  	return ip
   737  }
   738  
   739  // String returns the string form of the IP address ip.
   740  // It returns one of 5 forms:
   741  //
   742  //   - "invalid IP", if ip is the zero [Addr]
   743  //   - IPv4 dotted decimal ("192.0.2.1")
   744  //   - IPv6 ("2001:db8::1")
   745  //   - "::ffff:1.2.3.4" (if [Addr.Is4In6])
   746  //   - IPv6 with zone ("fe80:db8::1%eth0")
   747  //
   748  // Note that unlike package net's IP.String method,
   749  // IPv4-mapped IPv6 addresses format with a "::ffff:"
   750  // prefix before the dotted quad.
   751  func (ip Addr) String() string {
   752  	switch ip.z {
   753  	case z0:
   754  		return "invalid IP"
   755  	case z4:
   756  		return ip.string4()
   757  	default:
   758  		if ip.Is4In6() {
   759  			if z := ip.Zone(); z != "" {
   760  				return "::ffff:" + ip.Unmap().string4() + "%" + z
   761  			} else {
   762  				return "::ffff:" + ip.Unmap().string4()
   763  			}
   764  		}
   765  		return ip.string6()
   766  	}
   767  }
   768  
   769  // AppendTo appends a text encoding of ip,
   770  // as generated by [Addr.MarshalText],
   771  // to b and returns the extended buffer.
   772  func (ip Addr) AppendTo(b []byte) []byte {
   773  	switch ip.z {
   774  	case z0:
   775  		return b
   776  	case z4:
   777  		return ip.appendTo4(b)
   778  	default:
   779  		if ip.Is4In6() {
   780  			b = append(b, "::ffff:"...)
   781  			b = ip.Unmap().appendTo4(b)
   782  			if z := ip.Zone(); z != "" {
   783  				b = append(b, '%')
   784  				b = append(b, z...)
   785  			}
   786  			return b
   787  		}
   788  		return ip.appendTo6(b)
   789  	}
   790  }
   791  
   792  // digits is a string of the hex digits from 0 to f. It's used in
   793  // appendDecimal and appendHex to format IP addresses.
   794  const digits = "0123456789abcdef"
   795  
   796  // appendDecimal appends the decimal string representation of x to b.
   797  func appendDecimal(b []byte, x uint8) []byte {
   798  	// Using this function rather than strconv.AppendUint makes IPv4
   799  	// string building 2x faster.
   800  
   801  	if x >= 100 {
   802  		b = append(b, digits[x/100])
   803  	}
   804  	if x >= 10 {
   805  		b = append(b, digits[x/10%10])
   806  	}
   807  	return append(b, digits[x%10])
   808  }
   809  
   810  // appendHex appends the hex string representation of x to b.
   811  func appendHex(b []byte, x uint16) []byte {
   812  	// Using this function rather than strconv.AppendUint makes IPv6
   813  	// string building 2x faster.
   814  
   815  	if x >= 0x1000 {
   816  		b = append(b, digits[x>>12])
   817  	}
   818  	if x >= 0x100 {
   819  		b = append(b, digits[x>>8&0xf])
   820  	}
   821  	if x >= 0x10 {
   822  		b = append(b, digits[x>>4&0xf])
   823  	}
   824  	return append(b, digits[x&0xf])
   825  }
   826  
   827  // appendHexPad appends the fully padded hex string representation of x to b.
   828  func appendHexPad(b []byte, x uint16) []byte {
   829  	return append(b, digits[x>>12], digits[x>>8&0xf], digits[x>>4&0xf], digits[x&0xf])
   830  }
   831  
   832  func (ip Addr) string4() string {
   833  	const max = len("255.255.255.255")
   834  	ret := make([]byte, 0, max)
   835  	ret = ip.appendTo4(ret)
   836  	return string(ret)
   837  }
   838  
   839  func (ip Addr) appendTo4(ret []byte) []byte {
   840  	ret = appendDecimal(ret, ip.v4(0))
   841  	ret = append(ret, '.')
   842  	ret = appendDecimal(ret, ip.v4(1))
   843  	ret = append(ret, '.')
   844  	ret = appendDecimal(ret, ip.v4(2))
   845  	ret = append(ret, '.')
   846  	ret = appendDecimal(ret, ip.v4(3))
   847  	return ret
   848  }
   849  
   850  // string6 formats ip in IPv6 textual representation. It follows the
   851  // guidelines in section 4 of RFC 5952
   852  // (https://tools.ietf.org/html/rfc5952#section-4): no unnecessary
   853  // zeros, use :: to elide the longest run of zeros, and don't use ::
   854  // to compact a single zero field.
   855  func (ip Addr) string6() string {
   856  	// Use a zone with a "plausibly long" name, so that most zone-ful
   857  	// IP addresses won't require additional allocation.
   858  	//
   859  	// The compiler does a cool optimization here, where ret ends up
   860  	// stack-allocated and so the only allocation this function does
   861  	// is to construct the returned string. As such, it's okay to be a
   862  	// bit greedy here, size-wise.
   863  	const max = len("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff%enp5s0")
   864  	ret := make([]byte, 0, max)
   865  	ret = ip.appendTo6(ret)
   866  	return string(ret)
   867  }
   868  
   869  func (ip Addr) appendTo6(ret []byte) []byte {
   870  	zeroStart, zeroEnd := uint8(255), uint8(255)
   871  	for i := uint8(0); i < 8; i++ {
   872  		j := i
   873  		for j < 8 && ip.v6u16(j) == 0 {
   874  			j++
   875  		}
   876  		if l := j - i; l >= 2 && l > zeroEnd-zeroStart {
   877  			zeroStart, zeroEnd = i, j
   878  		}
   879  	}
   880  
   881  	for i := uint8(0); i < 8; i++ {
   882  		if i == zeroStart {
   883  			ret = append(ret, ':', ':')
   884  			i = zeroEnd
   885  			if i >= 8 {
   886  				break
   887  			}
   888  		} else if i > 0 {
   889  			ret = append(ret, ':')
   890  		}
   891  
   892  		ret = appendHex(ret, ip.v6u16(i))
   893  	}
   894  
   895  	if ip.z != z6noz {
   896  		ret = append(ret, '%')
   897  		ret = append(ret, ip.Zone()...)
   898  	}
   899  	return ret
   900  }
   901  
   902  // StringExpanded is like [Addr.String] but IPv6 addresses are expanded with leading
   903  // zeroes and no "::" compression. For example, "2001:db8::1" becomes
   904  // "2001:0db8:0000:0000:0000:0000:0000:0001".
   905  func (ip Addr) StringExpanded() string {
   906  	switch ip.z {
   907  	case z0, z4:
   908  		return ip.String()
   909  	}
   910  
   911  	const size = len("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff")
   912  	ret := make([]byte, 0, size)
   913  	for i := uint8(0); i < 8; i++ {
   914  		if i > 0 {
   915  			ret = append(ret, ':')
   916  		}
   917  
   918  		ret = appendHexPad(ret, ip.v6u16(i))
   919  	}
   920  
   921  	if ip.z != z6noz {
   922  		// The addition of a zone will cause a second allocation, but when there
   923  		// is no zone the ret slice will be stack allocated.
   924  		ret = append(ret, '%')
   925  		ret = append(ret, ip.Zone()...)
   926  	}
   927  	return string(ret)
   928  }
   929  
   930  // MarshalText implements the [encoding.TextMarshaler] interface,
   931  // The encoding is the same as returned by [Addr.String], with one exception:
   932  // If ip is the zero [Addr], the encoding is the empty string.
   933  func (ip Addr) MarshalText() ([]byte, error) {
   934  	switch ip.z {
   935  	case z0:
   936  		return []byte(""), nil
   937  	case z4:
   938  		max := len("255.255.255.255")
   939  		b := make([]byte, 0, max)
   940  		return ip.appendTo4(b), nil
   941  	default:
   942  		max := len("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff%enp5s0")
   943  		b := make([]byte, 0, max)
   944  		if ip.Is4In6() {
   945  			b = append(b, "::ffff:"...)
   946  			b = ip.Unmap().appendTo4(b)
   947  			if z := ip.Zone(); z != "" {
   948  				b = append(b, '%')
   949  				b = append(b, z...)
   950  			}
   951  			return b, nil
   952  		}
   953  		return ip.appendTo6(b), nil
   954  	}
   955  
   956  }
   957  
   958  // UnmarshalText implements the encoding.TextUnmarshaler interface.
   959  // The IP address is expected in a form accepted by [ParseAddr].
   960  //
   961  // If text is empty, UnmarshalText sets *ip to the zero [Addr] and
   962  // returns no error.
   963  func (ip *Addr) UnmarshalText(text []byte) error {
   964  	if len(text) == 0 {
   965  		*ip = Addr{}
   966  		return nil
   967  	}
   968  	var err error
   969  	*ip, err = ParseAddr(string(text))
   970  	return err
   971  }
   972  
   973  func (ip Addr) marshalBinaryWithTrailingBytes(trailingBytes int) []byte {
   974  	var b []byte
   975  	switch ip.z {
   976  	case z0:
   977  		b = make([]byte, trailingBytes)
   978  	case z4:
   979  		b = make([]byte, 4+trailingBytes)
   980  		bePutUint32(b, uint32(ip.addr.lo))
   981  	default:
   982  		z := ip.Zone()
   983  		b = make([]byte, 16+len(z)+trailingBytes)
   984  		bePutUint64(b[:8], ip.addr.hi)
   985  		bePutUint64(b[8:], ip.addr.lo)
   986  		copy(b[16:], z)
   987  	}
   988  	return b
   989  }
   990  
   991  // MarshalBinary implements the [encoding.BinaryMarshaler] interface.
   992  // It returns a zero-length slice for the zero [Addr],
   993  // the 4-byte form for an IPv4 address,
   994  // and the 16-byte form with zone appended for an IPv6 address.
   995  func (ip Addr) MarshalBinary() ([]byte, error) {
   996  	return ip.marshalBinaryWithTrailingBytes(0), nil
   997  }
   998  
   999  // UnmarshalBinary implements the [encoding.BinaryUnmarshaler] interface.
  1000  // It expects data in the form generated by MarshalBinary.
  1001  func (ip *Addr) UnmarshalBinary(b []byte) error {
  1002  	n := len(b)
  1003  	switch {
  1004  	case n == 0:
  1005  		*ip = Addr{}
  1006  		return nil
  1007  	case n == 4:
  1008  		*ip = AddrFrom4([4]byte(b))
  1009  		return nil
  1010  	case n == 16:
  1011  		*ip = AddrFrom16([16]byte(b))
  1012  		return nil
  1013  	case n > 16:
  1014  		*ip = AddrFrom16([16]byte(b[:16])).WithZone(string(b[16:]))
  1015  		return nil
  1016  	}
  1017  	return errors.New("unexpected slice size")
  1018  }
  1019  
  1020  // AddrPort is an IP and a port number.
  1021  type AddrPort struct {
  1022  	ip   Addr
  1023  	port uint16
  1024  }
  1025  
  1026  // AddrPortFrom returns an [AddrPort] with the provided IP and port.
  1027  // It does not allocate.
  1028  func AddrPortFrom(ip Addr, port uint16) AddrPort { return AddrPort{ip: ip, port: port} }
  1029  
  1030  // Addr returns p's IP address.
  1031  func (p AddrPort) Addr() Addr { return p.ip }
  1032  
  1033  // Port returns p's port.
  1034  func (p AddrPort) Port() uint16 { return p.port }
  1035  
  1036  // splitAddrPort splits s into an IP address string and a port
  1037  // string. It splits strings shaped like "foo:bar" or "[foo]:bar",
  1038  // without further validating the substrings. v6 indicates whether the
  1039  // ip string should parse as an IPv6 address or an IPv4 address, in
  1040  // order for s to be a valid ip:port string.
  1041  func splitAddrPort(s string) (ip, port string, v6 bool, err error) {
  1042  	i := bytealg.LastIndexByteString(s, ':')
  1043  	if i == -1 {
  1044  		return "", "", false, errors.New("not an ip:port")
  1045  	}
  1046  
  1047  	ip, port = s[:i], s[i+1:]
  1048  	if len(ip) == 0 {
  1049  		return "", "", false, errors.New("no IP")
  1050  	}
  1051  	if len(port) == 0 {
  1052  		return "", "", false, errors.New("no port")
  1053  	}
  1054  	if ip[0] == '[' {
  1055  		if len(ip) < 2 || ip[len(ip)-1] != ']' {
  1056  			return "", "", false, errors.New("missing ]")
  1057  		}
  1058  		ip = ip[1 : len(ip)-1]
  1059  		v6 = true
  1060  	}
  1061  
  1062  	return ip, port, v6, nil
  1063  }
  1064  
  1065  // ParseAddrPort parses s as an [AddrPort].
  1066  //
  1067  // It doesn't do any name resolution: both the address and the port
  1068  // must be numeric.
  1069  func ParseAddrPort(s string) (AddrPort, error) {
  1070  	var ipp AddrPort
  1071  	ip, port, v6, err := splitAddrPort(s)
  1072  	if err != nil {
  1073  		return ipp, err
  1074  	}
  1075  	port16, err := strconv.ParseUint(port, 10, 16)
  1076  	if err != nil {
  1077  		return ipp, errors.New("invalid port " + strconv.Quote(port) + " parsing " + strconv.Quote(s))
  1078  	}
  1079  	ipp.port = uint16(port16)
  1080  	ipp.ip, err = ParseAddr(ip)
  1081  	if err != nil {
  1082  		return AddrPort{}, err
  1083  	}
  1084  	if v6 && ipp.ip.Is4() {
  1085  		return AddrPort{}, errors.New("invalid ip:port " + strconv.Quote(s) + ", square brackets can only be used with IPv6 addresses")
  1086  	} else if !v6 && ipp.ip.Is6() {
  1087  		return AddrPort{}, errors.New("invalid ip:port " + strconv.Quote(s) + ", IPv6 addresses must be surrounded by square brackets")
  1088  	}
  1089  	return ipp, nil
  1090  }
  1091  
  1092  // MustParseAddrPort calls [ParseAddrPort](s) and panics on error.
  1093  // It is intended for use in tests with hard-coded strings.
  1094  func MustParseAddrPort(s string) AddrPort {
  1095  	ip, err := ParseAddrPort(s)
  1096  	if err != nil {
  1097  		panic(err)
  1098  	}
  1099  	return ip
  1100  }
  1101  
  1102  // IsValid reports whether p.Addr() is valid.
  1103  // All ports are valid, including zero.
  1104  func (p AddrPort) IsValid() bool { return p.ip.IsValid() }
  1105  
  1106  // Compare returns an integer comparing two AddrPorts.
  1107  // The result will be 0 if p == p2, -1 if p < p2, and +1 if p > p2.
  1108  // AddrPorts sort first by IP address, then port.
  1109  func (p AddrPort) Compare(p2 AddrPort) int {
  1110  	if c := p.Addr().Compare(p2.Addr()); c != 0 {
  1111  		return c
  1112  	}
  1113  	return cmp.Compare(p.Port(), p2.Port())
  1114  }
  1115  
  1116  func (p AddrPort) String() string {
  1117  	switch p.ip.z {
  1118  	case z0:
  1119  		return "invalid AddrPort"
  1120  	case z4:
  1121  		const max = len("255.255.255.255:65535")
  1122  		buf := make([]byte, 0, max)
  1123  		buf = p.ip.appendTo4(buf)
  1124  		buf = append(buf, ':')
  1125  		buf = strconv.AppendUint(buf, uint64(p.port), 10)
  1126  		return string(buf)
  1127  	default:
  1128  		// TODO: this could be more efficient allocation-wise:
  1129  		return "[" + p.ip.String() + "]:" + itoa.Uitoa(uint(p.port))
  1130  	}
  1131  }
  1132  
  1133  // AppendTo appends a text encoding of p,
  1134  // as generated by [AddrPort.MarshalText],
  1135  // to b and returns the extended buffer.
  1136  func (p AddrPort) AppendTo(b []byte) []byte {
  1137  	switch p.ip.z {
  1138  	case z0:
  1139  		return b
  1140  	case z4:
  1141  		b = p.ip.appendTo4(b)
  1142  	default:
  1143  		if p.ip.Is4In6() {
  1144  			b = append(b, "[::ffff:"...)
  1145  			b = p.ip.Unmap().appendTo4(b)
  1146  			if z := p.ip.Zone(); z != "" {
  1147  				b = append(b, '%')
  1148  				b = append(b, z...)
  1149  			}
  1150  		} else {
  1151  			b = append(b, '[')
  1152  			b = p.ip.appendTo6(b)
  1153  		}
  1154  		b = append(b, ']')
  1155  	}
  1156  	b = append(b, ':')
  1157  	b = strconv.AppendUint(b, uint64(p.port), 10)
  1158  	return b
  1159  }
  1160  
  1161  // MarshalText implements the [encoding.TextMarshaler] interface. The
  1162  // encoding is the same as returned by [AddrPort.String], with one exception: if
  1163  // p.Addr() is the zero [Addr], the encoding is the empty string.
  1164  func (p AddrPort) MarshalText() ([]byte, error) {
  1165  	var max int
  1166  	switch p.ip.z {
  1167  	case z0:
  1168  	case z4:
  1169  		max = len("255.255.255.255:65535")
  1170  	default:
  1171  		max = len("[ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff%enp5s0]:65535")
  1172  	}
  1173  	b := make([]byte, 0, max)
  1174  	b = p.AppendTo(b)
  1175  	return b, nil
  1176  }
  1177  
  1178  // UnmarshalText implements the encoding.TextUnmarshaler
  1179  // interface. The [AddrPort] is expected in a form
  1180  // generated by [AddrPort.MarshalText] or accepted by [ParseAddrPort].
  1181  func (p *AddrPort) UnmarshalText(text []byte) error {
  1182  	if len(text) == 0 {
  1183  		*p = AddrPort{}
  1184  		return nil
  1185  	}
  1186  	var err error
  1187  	*p, err = ParseAddrPort(string(text))
  1188  	return err
  1189  }
  1190  
  1191  // MarshalBinary implements the [encoding.BinaryMarshaler] interface.
  1192  // It returns [Addr.MarshalBinary] with an additional two bytes appended
  1193  // containing the port in little-endian.
  1194  func (p AddrPort) MarshalBinary() ([]byte, error) {
  1195  	b := p.Addr().marshalBinaryWithTrailingBytes(2)
  1196  	lePutUint16(b[len(b)-2:], p.Port())
  1197  	return b, nil
  1198  }
  1199  
  1200  // UnmarshalBinary implements the [encoding.BinaryUnmarshaler] interface.
  1201  // It expects data in the form generated by [AddrPort.MarshalBinary].
  1202  func (p *AddrPort) UnmarshalBinary(b []byte) error {
  1203  	if len(b) < 2 {
  1204  		return errors.New("unexpected slice size")
  1205  	}
  1206  	var addr Addr
  1207  	err := addr.UnmarshalBinary(b[:len(b)-2])
  1208  	if err != nil {
  1209  		return err
  1210  	}
  1211  	*p = AddrPortFrom(addr, leUint16(b[len(b)-2:]))
  1212  	return nil
  1213  }
  1214  
  1215  // Prefix is an IP address prefix (CIDR) representing an IP network.
  1216  //
  1217  // The first [Prefix.Bits]() of [Addr]() are specified. The remaining bits match any address.
  1218  // The range of Bits() is [0,32] for IPv4 or [0,128] for IPv6.
  1219  type Prefix struct {
  1220  	ip Addr
  1221  
  1222  	// bitsPlusOne stores the prefix bit length plus one.
  1223  	// A Prefix is valid if and only if bitsPlusOne is non-zero.
  1224  	bitsPlusOne uint8
  1225  }
  1226  
  1227  // PrefixFrom returns a [Prefix] with the provided IP address and bit
  1228  // prefix length.
  1229  //
  1230  // It does not allocate. Unlike [Addr.Prefix], [PrefixFrom] does not mask
  1231  // off the host bits of ip.
  1232  //
  1233  // If bits is less than zero or greater than ip.BitLen, [Prefix.Bits]
  1234  // will return an invalid value -1.
  1235  func PrefixFrom(ip Addr, bits int) Prefix {
  1236  	var bitsPlusOne uint8
  1237  	if !ip.isZero() && bits >= 0 && bits <= ip.BitLen() {
  1238  		bitsPlusOne = uint8(bits) + 1
  1239  	}
  1240  	return Prefix{
  1241  		ip:          ip.withoutZone(),
  1242  		bitsPlusOne: bitsPlusOne,
  1243  	}
  1244  }
  1245  
  1246  // Addr returns p's IP address.
  1247  func (p Prefix) Addr() Addr { return p.ip }
  1248  
  1249  // Bits returns p's prefix length.
  1250  //
  1251  // It reports -1 if invalid.
  1252  func (p Prefix) Bits() int { return int(p.bitsPlusOne) - 1 }
  1253  
  1254  // IsValid reports whether p.Bits() has a valid range for p.Addr().
  1255  // If p.Addr() is the zero [Addr], IsValid returns false.
  1256  // Note that if p is the zero [Prefix], then p.IsValid() == false.
  1257  func (p Prefix) IsValid() bool { return p.bitsPlusOne > 0 }
  1258  
  1259  func (p Prefix) isZero() bool { return p == Prefix{} }
  1260  
  1261  // IsSingleIP reports whether p contains exactly one IP.
  1262  func (p Prefix) IsSingleIP() bool { return p.IsValid() && p.Bits() == p.ip.BitLen() }
  1263  
  1264  // compare returns an integer comparing two prefixes.
  1265  // The result will be 0 if p == p2, -1 if p < p2, and +1 if p > p2.
  1266  // Prefixes sort first by validity (invalid before valid), then
  1267  // address family (IPv4 before IPv6), then prefix length, then
  1268  // address.
  1269  //
  1270  // Unexported for Go 1.22 because we may want to compare by p.Addr first.
  1271  // See post-acceptance discussion on go.dev/issue/61642.
  1272  func (p Prefix) compare(p2 Prefix) int {
  1273  	if c := cmp.Compare(p.Addr().BitLen(), p2.Addr().BitLen()); c != 0 {
  1274  		return c
  1275  	}
  1276  	if c := cmp.Compare(p.Bits(), p2.Bits()); c != 0 {
  1277  		return c
  1278  	}
  1279  	return p.Addr().Compare(p2.Addr())
  1280  }
  1281  
  1282  // ParsePrefix parses s as an IP address prefix.
  1283  // The string can be in the form "192.168.1.0/24" or "2001:db8::/32",
  1284  // the CIDR notation defined in RFC 4632 and RFC 4291.
  1285  // IPv6 zones are not permitted in prefixes, and an error will be returned if a
  1286  // zone is present.
  1287  //
  1288  // Note that masked address bits are not zeroed. Use Masked for that.
  1289  func ParsePrefix(s string) (Prefix, error) {
  1290  	i := bytealg.LastIndexByteString(s, '/')
  1291  	if i < 0 {
  1292  		return Prefix{}, errors.New("netip.ParsePrefix(" + strconv.Quote(s) + "): no '/'")
  1293  	}
  1294  	ip, err := ParseAddr(s[:i])
  1295  	if err != nil {
  1296  		return Prefix{}, errors.New("netip.ParsePrefix(" + strconv.Quote(s) + "): " + err.Error())
  1297  	}
  1298  	// IPv6 zones are not allowed: https://go.dev/issue/51899
  1299  	if ip.Is6() && ip.z != z6noz {
  1300  		return Prefix{}, errors.New("netip.ParsePrefix(" + strconv.Quote(s) + "): IPv6 zones cannot be present in a prefix")
  1301  	}
  1302  
  1303  	bitsStr := s[i+1:]
  1304  
  1305  	// strconv.Atoi accepts a leading sign and leading zeroes, but we don't want that.
  1306  	if len(bitsStr) > 1 && (bitsStr[0] < '1' || bitsStr[0] > '9') {
  1307  		return Prefix{}, errors.New("netip.ParsePrefix(" + strconv.Quote(s) + "): bad bits after slash: " + strconv.Quote(bitsStr))
  1308  	}
  1309  
  1310  	bits, err := strconv.Atoi(bitsStr)
  1311  	if err != nil {
  1312  		return Prefix{}, errors.New("netip.ParsePrefix(" + strconv.Quote(s) + "): bad bits after slash: " + strconv.Quote(bitsStr))
  1313  	}
  1314  	maxBits := 32
  1315  	if ip.Is6() {
  1316  		maxBits = 128
  1317  	}
  1318  	if bits < 0 || bits > maxBits {
  1319  		return Prefix{}, errors.New("netip.ParsePrefix(" + strconv.Quote(s) + "): prefix length out of range")
  1320  	}
  1321  	return PrefixFrom(ip, bits), nil
  1322  }
  1323  
  1324  // MustParsePrefix calls [ParsePrefix](s) and panics on error.
  1325  // It is intended for use in tests with hard-coded strings.
  1326  func MustParsePrefix(s string) Prefix {
  1327  	ip, err := ParsePrefix(s)
  1328  	if err != nil {
  1329  		panic(err)
  1330  	}
  1331  	return ip
  1332  }
  1333  
  1334  // Masked returns p in its canonical form, with all but the high
  1335  // p.Bits() bits of p.Addr() masked off.
  1336  //
  1337  // If p is zero or otherwise invalid, Masked returns the zero [Prefix].
  1338  func (p Prefix) Masked() Prefix {
  1339  	m, _ := p.ip.Prefix(p.Bits())
  1340  	return m
  1341  }
  1342  
  1343  // Contains reports whether the network p includes ip.
  1344  //
  1345  // An IPv4 address will not match an IPv6 prefix.
  1346  // An IPv4-mapped IPv6 address will not match an IPv4 prefix.
  1347  // A zero-value IP will not match any prefix.
  1348  // If ip has an IPv6 zone, Contains returns false,
  1349  // because Prefixes strip zones.
  1350  func (p Prefix) Contains(ip Addr) bool {
  1351  	if !p.IsValid() || ip.hasZone() {
  1352  		return false
  1353  	}
  1354  	if f1, f2 := p.ip.BitLen(), ip.BitLen(); f1 == 0 || f2 == 0 || f1 != f2 {
  1355  		return false
  1356  	}
  1357  	if ip.Is4() {
  1358  		// xor the IP addresses together; mismatched bits are now ones.
  1359  		// Shift away the number of bits we don't care about.
  1360  		// Shifts in Go are more efficient if the compiler can prove
  1361  		// that the shift amount is smaller than the width of the shifted type (64 here).
  1362  		// We know that p.bits is in the range 0..32 because p is Valid;
  1363  		// the compiler doesn't know that, so mask with 63 to help it.
  1364  		// Now truncate to 32 bits, because this is IPv4.
  1365  		// If all the bits we care about are equal, the result will be zero.
  1366  		return uint32((ip.addr.lo^p.ip.addr.lo)>>((32-p.Bits())&63)) == 0
  1367  	} else {
  1368  		// xor the IP addresses together.
  1369  		// Mask away the bits we don't care about.
  1370  		// If all the bits we care about are equal, the result will be zero.
  1371  		return ip.addr.xor(p.ip.addr).and(mask6(p.Bits())).isZero()
  1372  	}
  1373  }
  1374  
  1375  // Overlaps reports whether p and o contain any IP addresses in common.
  1376  //
  1377  // If p and o are of different address families or either have a zero
  1378  // IP, it reports false. Like the Contains method, a prefix with an
  1379  // IPv4-mapped IPv6 address is still treated as an IPv6 mask.
  1380  func (p Prefix) Overlaps(o Prefix) bool {
  1381  	if !p.IsValid() || !o.IsValid() {
  1382  		return false
  1383  	}
  1384  	if p == o {
  1385  		return true
  1386  	}
  1387  	if p.ip.Is4() != o.ip.Is4() {
  1388  		return false
  1389  	}
  1390  	var minBits int
  1391  	if pb, ob := p.Bits(), o.Bits(); pb < ob {
  1392  		minBits = pb
  1393  	} else {
  1394  		minBits = ob
  1395  	}
  1396  	if minBits == 0 {
  1397  		return true
  1398  	}
  1399  	// One of these Prefix calls might look redundant, but we don't require
  1400  	// that p and o values are normalized (via Prefix.Masked) first,
  1401  	// so the Prefix call on the one that's already minBits serves to zero
  1402  	// out any remaining bits in IP.
  1403  	var err error
  1404  	if p, err = p.ip.Prefix(minBits); err != nil {
  1405  		return false
  1406  	}
  1407  	if o, err = o.ip.Prefix(minBits); err != nil {
  1408  		return false
  1409  	}
  1410  	return p.ip == o.ip
  1411  }
  1412  
  1413  // AppendTo appends a text encoding of p,
  1414  // as generated by [Prefix.MarshalText],
  1415  // to b and returns the extended buffer.
  1416  func (p Prefix) AppendTo(b []byte) []byte {
  1417  	if p.isZero() {
  1418  		return b
  1419  	}
  1420  	if !p.IsValid() {
  1421  		return append(b, "invalid Prefix"...)
  1422  	}
  1423  
  1424  	// p.ip is non-nil, because p is valid.
  1425  	if p.ip.z == z4 {
  1426  		b = p.ip.appendTo4(b)
  1427  	} else {
  1428  		if p.ip.Is4In6() {
  1429  			b = append(b, "::ffff:"...)
  1430  			b = p.ip.Unmap().appendTo4(b)
  1431  		} else {
  1432  			b = p.ip.appendTo6(b)
  1433  		}
  1434  	}
  1435  
  1436  	b = append(b, '/')
  1437  	b = appendDecimal(b, uint8(p.Bits()))
  1438  	return b
  1439  }
  1440  
  1441  // MarshalText implements the [encoding.TextMarshaler] interface,
  1442  // The encoding is the same as returned by [Prefix.String], with one exception:
  1443  // If p is the zero value, the encoding is the empty string.
  1444  func (p Prefix) MarshalText() ([]byte, error) {
  1445  	var max int
  1446  	switch p.ip.z {
  1447  	case z0:
  1448  	case z4:
  1449  		max = len("255.255.255.255/32")
  1450  	default:
  1451  		max = len("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff%enp5s0/128")
  1452  	}
  1453  	b := make([]byte, 0, max)
  1454  	b = p.AppendTo(b)
  1455  	return b, nil
  1456  }
  1457  
  1458  // UnmarshalText implements the encoding.TextUnmarshaler interface.
  1459  // The IP address is expected in a form accepted by [ParsePrefix]
  1460  // or generated by [Prefix.MarshalText].
  1461  func (p *Prefix) UnmarshalText(text []byte) error {
  1462  	if len(text) == 0 {
  1463  		*p = Prefix{}
  1464  		return nil
  1465  	}
  1466  	var err error
  1467  	*p, err = ParsePrefix(string(text))
  1468  	return err
  1469  }
  1470  
  1471  // MarshalBinary implements the [encoding.BinaryMarshaler] interface.
  1472  // It returns [Addr.MarshalBinary] with an additional byte appended
  1473  // containing the prefix bits.
  1474  func (p Prefix) MarshalBinary() ([]byte, error) {
  1475  	b := p.Addr().withoutZone().marshalBinaryWithTrailingBytes(1)
  1476  	b[len(b)-1] = uint8(p.Bits())
  1477  	return b, nil
  1478  }
  1479  
  1480  // UnmarshalBinary implements the [encoding.BinaryUnmarshaler] interface.
  1481  // It expects data in the form generated by [Prefix.MarshalBinary].
  1482  func (p *Prefix) UnmarshalBinary(b []byte) error {
  1483  	if len(b) < 1 {
  1484  		return errors.New("unexpected slice size")
  1485  	}
  1486  	var addr Addr
  1487  	err := addr.UnmarshalBinary(b[:len(b)-1])
  1488  	if err != nil {
  1489  		return err
  1490  	}
  1491  	*p = PrefixFrom(addr, int(b[len(b)-1]))
  1492  	return nil
  1493  }
  1494  
  1495  // String returns the CIDR notation of p: "<ip>/<bits>".
  1496  func (p Prefix) String() string {
  1497  	if !p.IsValid() {
  1498  		return "invalid Prefix"
  1499  	}
  1500  	return p.ip.String() + "/" + itoa.Itoa(p.Bits())
  1501  }
  1502  

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