netip.go

     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  	"internal/bytealg"
    18  	"internal/byteorder"
    19  	"internal/itoa"
    20  	"math"
    21  	"strconv"
    22  	"unique"
    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  	// Details about the address, wrapped up together and canonicalized.
    57  	z unique.Handle[addrDetail]
    58  }
    59  
    60  // addrDetail represents the details of an Addr, like address family and IPv6 zone.
    61  type addrDetail struct {
    62  	isV6   bool   // IPv4 is false, IPv6 is true.
    63  	zoneV6 string // != "" only if IsV6 is true.
    64  }
    65  
    66  // z0, z4, and z6noz are sentinel Addr.z values.
    67  // See the Addr type's field docs.
    68  var (
    69  	z0    unique.Handle[addrDetail]
    70  	z4    = unique.Make(addrDetail{})
    71  	z6noz = unique.Make(addrDetail{isV6: true})
    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  			byteorder.BeUint64(addr[:8]),
   106  			byteorder.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  func parseIPv4Fields(in string, off, end int, fields []uint8) error {
   156  	var val, pos int
   157  	var digLen int // number of digits in current octet
   158  	s := in[off:end]
   159  	for i := 0; i < len(s); i++ {
   160  		if s[i] >= '0' && s[i] <= '9' {
   161  			if digLen == 1 && val == 0 {
   162  				return parseAddrError{in: in, msg: "IPv4 field has octet with leading zero"}
   163  			}
   164  			val = val*10 + int(s[i]) - '0'
   165  			digLen++
   166  			if val > 255 {
   167  				return parseAddrError{in: in, msg: "IPv4 field has value >255"}
   168  			}
   169  		} else if s[i] == '.' {
   170  			// .1.2.3
   171  			// 1.2.3.
   172  			// 1..2.3
   173  			if i == 0 || i == len(s)-1 || s[i-1] == '.' {
   174  				return parseAddrError{in: in, msg: "IPv4 field must have at least one digit", at: s[i:]}
   175  			}
   176  			// 1.2.3.4.5
   177  			if pos == 3 {
   178  				return parseAddrError{in: in, msg: "IPv4 address too long"}
   179  			}
   180  			fields[pos] = uint8(val)
   181  			pos++
   182  			val = 0
   183  			digLen = 0
   184  		} else {
   185  			return parseAddrError{in: in, msg: "unexpected character", at: s[i:]}
   186  		}
   187  	}
   188  	if pos < 3 {
   189  		return parseAddrError{in: in, msg: "IPv4 address too short"}
   190  	}
   191  	fields[3] = uint8(val)
   192  	return nil
   193  }
   194  
   195  // parseIPv4 parses s as an IPv4 address (in form "192.168.0.1").
   196  func parseIPv4(s string) (ip Addr, err error) {
   197  	var fields [4]uint8
   198  	err = parseIPv4Fields(s, 0, len(s), fields[:])
   199  	if err != nil {
   200  		return Addr{}, err
   201  	}
   202  	return AddrFrom4(fields), nil
   203  }
   204  
   205  // parseIPv6 parses s as an IPv6 address (in form "2001:db8::68").
   206  func parseIPv6(in string) (Addr, error) {
   207  	s := in
   208  
   209  	// Split off the zone right from the start. Yes it's a second scan
   210  	// of the string, but trying to handle it inline makes a bunch of
   211  	// other inner loop conditionals more expensive, and it ends up
   212  	// being slower.
   213  	zone := ""
   214  	i := bytealg.IndexByteString(s, '%')
   215  	if i != -1 {
   216  		s, zone = s[:i], s[i+1:]
   217  		if zone == "" {
   218  			// Not allowed to have an empty zone if explicitly specified.
   219  			return Addr{}, parseAddrError{in: in, msg: "zone must be a non-empty string"}
   220  		}
   221  	}
   222  
   223  	var ip [16]byte
   224  	ellipsis := -1 // position of ellipsis in ip
   225  
   226  	// Might have leading ellipsis
   227  	if len(s) >= 2 && s[0] == ':' && s[1] == ':' {
   228  		ellipsis = 0
   229  		s = s[2:]
   230  		// Might be only ellipsis
   231  		if len(s) == 0 {
   232  			return IPv6Unspecified().WithZone(zone), nil
   233  		}
   234  	}
   235  
   236  	// Loop, parsing hex numbers followed by colon.
   237  	i = 0
   238  	for i < 16 {
   239  		// Hex number. Similar to parseIPv4, inlining the hex number
   240  		// parsing yields a significant performance increase.
   241  		off := 0
   242  		acc := uint32(0)
   243  		for ; off < len(s); off++ {
   244  			c := s[off]
   245  			if c >= '0' && c <= '9' {
   246  				acc = (acc << 4) + uint32(c-'0')
   247  			} else if c >= 'a' && c <= 'f' {
   248  				acc = (acc << 4) + uint32(c-'a'+10)
   249  			} else if c >= 'A' && c <= 'F' {
   250  				acc = (acc << 4) + uint32(c-'A'+10)
   251  			} else {
   252  				break
   253  			}
   254  			if off > 3 {
   255  				//more than 4 digits in group, fail.
   256  				return Addr{}, parseAddrError{in: in, msg: "each group must have 4 or less digits", at: s}
   257  			}
   258  			if acc > math.MaxUint16 {
   259  				// Overflow, fail.
   260  				return Addr{}, parseAddrError{in: in, msg: "IPv6 field has value >=2^16", at: s}
   261  			}
   262  		}
   263  		if off == 0 {
   264  			// No digits found, fail.
   265  			return Addr{}, parseAddrError{in: in, msg: "each colon-separated field must have at least one digit", at: s}
   266  		}
   267  
   268  		// If followed by dot, might be in trailing IPv4.
   269  		if off < len(s) && s[off] == '.' {
   270  			if ellipsis < 0 && i != 12 {
   271  				// Not the right place.
   272  				return Addr{}, parseAddrError{in: in, msg: "embedded IPv4 address must replace the final 2 fields of the address", at: s}
   273  			}
   274  			if i+4 > 16 {
   275  				// Not enough room.
   276  				return Addr{}, parseAddrError{in: in, msg: "too many hex fields to fit an embedded IPv4 at the end of the address", at: s}
   277  			}
   278  
   279  			end := len(in)
   280  			if len(zone) > 0 {
   281  				end -= len(zone) + 1
   282  			}
   283  			err := parseIPv4Fields(in, end-len(s), end, ip[i:i+4])
   284  			if err != nil {
   285  				return Addr{}, err
   286  			}
   287  			s = ""
   288  			i += 4
   289  			break
   290  		}
   291  
   292  		// Save this 16-bit chunk.
   293  		ip[i] = byte(acc >> 8)
   294  		ip[i+1] = byte(acc)
   295  		i += 2
   296  
   297  		// Stop at end of string.
   298  		s = s[off:]
   299  		if len(s) == 0 {
   300  			break
   301  		}
   302  
   303  		// Otherwise must be followed by colon and more.
   304  		if s[0] != ':' {
   305  			return Addr{}, parseAddrError{in: in, msg: "unexpected character, want colon", at: s}
   306  		} else if len(s) == 1 {
   307  			return Addr{}, parseAddrError{in: in, msg: "colon must be followed by more characters", at: s}
   308  		}
   309  		s = s[1:]
   310  
   311  		// Look for ellipsis.
   312  		if s[0] == ':' {
   313  			if ellipsis >= 0 { // already have one
   314  				return Addr{}, parseAddrError{in: in, msg: "multiple :: in address", at: s}
   315  			}
   316  			ellipsis = i
   317  			s = s[1:]
   318  			if len(s) == 0 { // can be at end
   319  				break
   320  			}
   321  		}
   322  	}
   323  
   324  	// Must have used entire string.
   325  	if len(s) != 0 {
   326  		return Addr{}, parseAddrError{in: in, msg: "trailing garbage after address", at: s}
   327  	}
   328  
   329  	// If didn't parse enough, expand ellipsis.
   330  	if i < 16 {
   331  		if ellipsis < 0 {
   332  			return Addr{}, parseAddrError{in: in, msg: "address string too short"}
   333  		}
   334  		n := 16 - i
   335  		for j := i - 1; j >= ellipsis; j-- {
   336  			ip[j+n] = ip[j]
   337  		}
   338  		clear(ip[ellipsis : ellipsis+n])
   339  	} else if ellipsis >= 0 {
   340  		// Ellipsis must represent at least one 0 group.
   341  		return Addr{}, parseAddrError{in: in, msg: "the :: must expand to at least one field of zeros"}
   342  	}
   343  	return AddrFrom16(ip).WithZone(zone), nil
   344  }
   345  
   346  // AddrFromSlice parses the 4- or 16-byte byte slice as an IPv4 or IPv6 address.
   347  // Note that a [net.IP] can be passed directly as the []byte argument.
   348  // If slice's length is not 4 or 16, AddrFromSlice returns [Addr]{}, false.
   349  func AddrFromSlice(slice []byte) (ip Addr, ok bool) {
   350  	switch len(slice) {
   351  	case 4:
   352  		return AddrFrom4([4]byte(slice)), true
   353  	case 16:
   354  		return AddrFrom16([16]byte(slice)), true
   355  	}
   356  	return Addr{}, false
   357  }
   358  
   359  // v4 returns the i'th byte of ip. If ip is not an IPv4, v4 returns
   360  // unspecified garbage.
   361  func (ip Addr) v4(i uint8) uint8 {
   362  	return uint8(ip.addr.lo >> ((3 - i) * 8))
   363  }
   364  
   365  // v6 returns the i'th byte of ip. If ip is an IPv4 address, this
   366  // accesses the IPv4-mapped IPv6 address form of the IP.
   367  func (ip Addr) v6(i uint8) uint8 {
   368  	return uint8(*(ip.addr.halves()[(i/8)%2]) >> ((7 - i%8) * 8))
   369  }
   370  
   371  // v6u16 returns the i'th 16-bit word of ip. If ip is an IPv4 address,
   372  // this accesses the IPv4-mapped IPv6 address form of the IP.
   373  func (ip Addr) v6u16(i uint8) uint16 {
   374  	return uint16(*(ip.addr.halves()[(i/4)%2]) >> ((3 - i%4) * 16))
   375  }
   376  
   377  // isZero reports whether ip is the zero value of the IP type.
   378  // The zero value is not a valid IP address of any type.
   379  //
   380  // Note that "0.0.0.0" and "::" are not the zero value. Use IsUnspecified to
   381  // check for these values instead.
   382  func (ip Addr) isZero() bool {
   383  	// Faster than comparing ip == Addr{}, but effectively equivalent,
   384  	// as there's no way to make an IP with a nil z from this package.
   385  	return ip.z == z0
   386  }
   387  
   388  // IsValid reports whether the [Addr] is an initialized address (not the zero Addr).
   389  //
   390  // Note that "0.0.0.0" and "::" are both valid values.
   391  func (ip Addr) IsValid() bool { return ip.z != z0 }
   392  
   393  // BitLen returns the number of bits in the IP address:
   394  // 128 for IPv6, 32 for IPv4, and 0 for the zero [Addr].
   395  //
   396  // Note that IPv4-mapped IPv6 addresses are considered IPv6 addresses
   397  // and therefore have bit length 128.
   398  func (ip Addr) BitLen() int {
   399  	switch ip.z {
   400  	case z0:
   401  		return 0
   402  	case z4:
   403  		return 32
   404  	}
   405  	return 128
   406  }
   407  
   408  // Zone returns ip's IPv6 scoped addressing zone, if any.
   409  func (ip Addr) Zone() string {
   410  	if ip.z == z0 {
   411  		return ""
   412  	}
   413  	return ip.z.Value().zoneV6
   414  }
   415  
   416  // Compare returns an integer comparing two IPs.
   417  // The result will be 0 if ip == ip2, -1 if ip < ip2, and +1 if ip > ip2.
   418  // The definition of "less than" is the same as the [Addr.Less] method.
   419  func (ip Addr) Compare(ip2 Addr) int {
   420  	f1, f2 := ip.BitLen(), ip2.BitLen()
   421  	if f1 < f2 {
   422  		return -1
   423  	}
   424  	if f1 > f2 {
   425  		return 1
   426  	}
   427  	hi1, hi2 := ip.addr.hi, ip2.addr.hi
   428  	if hi1 < hi2 {
   429  		return -1
   430  	}
   431  	if hi1 > hi2 {
   432  		return 1
   433  	}
   434  	lo1, lo2 := ip.addr.lo, ip2.addr.lo
   435  	if lo1 < lo2 {
   436  		return -1
   437  	}
   438  	if lo1 > lo2 {
   439  		return 1
   440  	}
   441  	if ip.Is6() {
   442  		za, zb := ip.Zone(), ip2.Zone()
   443  		if za < zb {
   444  			return -1
   445  		}
   446  		if za > zb {
   447  			return 1
   448  		}
   449  	}
   450  	return 0
   451  }
   452  
   453  // Less reports whether ip sorts before ip2.
   454  // IP addresses sort first by length, then their address.
   455  // IPv6 addresses with zones sort just after the same address without a zone.
   456  func (ip Addr) Less(ip2 Addr) bool { return ip.Compare(ip2) == -1 }
   457  
   458  // Is4 reports whether ip is an IPv4 address.
   459  //
   460  // It returns false for IPv4-mapped IPv6 addresses. See [Addr.Unmap].
   461  func (ip Addr) Is4() bool {
   462  	return ip.z == z4
   463  }
   464  
   465  // Is4In6 reports whether ip is an "IPv4-mapped IPv6 address"
   466  // as defined by RFC 4291.
   467  // That is, it reports whether ip is in ::ffff:0:0/96.
   468  func (ip Addr) Is4In6() bool {
   469  	return ip.Is6() && ip.addr.hi == 0 && ip.addr.lo>>32 == 0xffff
   470  }
   471  
   472  // Is6 reports whether ip is an IPv6 address, including IPv4-mapped
   473  // IPv6 addresses.
   474  func (ip Addr) Is6() bool {
   475  	return ip.z != z0 && ip.z != z4
   476  }
   477  
   478  // Unmap returns ip with any IPv4-mapped IPv6 address prefix removed.
   479  //
   480  // That is, if ip is an IPv6 address wrapping an IPv4 address, it
   481  // returns the wrapped IPv4 address. Otherwise it returns ip unmodified.
   482  func (ip Addr) Unmap() Addr {
   483  	if ip.Is4In6() {
   484  		ip.z = z4
   485  	}
   486  	return ip
   487  }
   488  
   489  // WithZone returns an IP that's the same as ip but with the provided
   490  // zone. If zone is empty, the zone is removed. If ip is an IPv4
   491  // address, WithZone is a no-op and returns ip unchanged.
   492  func (ip Addr) WithZone(zone string) Addr {
   493  	if !ip.Is6() {
   494  		return ip
   495  	}
   496  	if zone == "" {
   497  		ip.z = z6noz
   498  		return ip
   499  	}
   500  	ip.z = unique.Make(addrDetail{isV6: true, zoneV6: zone})
   501  	return ip
   502  }
   503  
   504  // withoutZone unconditionally strips the zone from ip.
   505  // It's similar to WithZone, but small enough to be inlinable.
   506  func (ip Addr) withoutZone() Addr {
   507  	if !ip.Is6() {
   508  		return ip
   509  	}
   510  	ip.z = z6noz
   511  	return ip
   512  }
   513  
   514  // hasZone reports whether ip has an IPv6 zone.
   515  func (ip Addr) hasZone() bool {
   516  	return ip.z != z0 && ip.z != z4 && ip.z != z6noz
   517  }
   518  
   519  // IsLinkLocalUnicast reports whether ip is a link-local unicast address.
   520  func (ip Addr) IsLinkLocalUnicast() bool {
   521  	if ip.Is4In6() {
   522  		ip = ip.Unmap()
   523  	}
   524  
   525  	// Dynamic Configuration of IPv4 Link-Local Addresses
   526  	// https://datatracker.ietf.org/doc/html/rfc3927#section-2.1
   527  	if ip.Is4() {
   528  		return ip.v4(0) == 169 && ip.v4(1) == 254
   529  	}
   530  	// IP Version 6 Addressing Architecture (2.4 Address Type Identification)
   531  	// https://datatracker.ietf.org/doc/html/rfc4291#section-2.4
   532  	if ip.Is6() {
   533  		return ip.v6u16(0)&0xffc0 == 0xfe80
   534  	}
   535  	return false // zero value
   536  }
   537  
   538  // IsLoopback reports whether ip is a loopback address.
   539  func (ip Addr) IsLoopback() bool {
   540  	if ip.Is4In6() {
   541  		ip = ip.Unmap()
   542  	}
   543  
   544  	// Requirements for Internet Hosts -- Communication Layers (3.2.1.3 Addressing)
   545  	// https://datatracker.ietf.org/doc/html/rfc1122#section-3.2.1.3
   546  	if ip.Is4() {
   547  		return ip.v4(0) == 127
   548  	}
   549  	// IP Version 6 Addressing Architecture (2.4 Address Type Identification)
   550  	// https://datatracker.ietf.org/doc/html/rfc4291#section-2.4
   551  	if ip.Is6() {
   552  		return ip.addr.hi == 0 && ip.addr.lo == 1
   553  	}
   554  	return false // zero value
   555  }
   556  
   557  // IsMulticast reports whether ip is a multicast address.
   558  func (ip Addr) IsMulticast() bool {
   559  	if ip.Is4In6() {
   560  		ip = ip.Unmap()
   561  	}
   562  
   563  	// Host Extensions for IP Multicasting (4. HOST GROUP ADDRESSES)
   564  	// https://datatracker.ietf.org/doc/html/rfc1112#section-4
   565  	if ip.Is4() {
   566  		return ip.v4(0)&0xf0 == 0xe0
   567  	}
   568  	// IP Version 6 Addressing Architecture (2.4 Address Type Identification)
   569  	// https://datatracker.ietf.org/doc/html/rfc4291#section-2.4
   570  	if ip.Is6() {
   571  		return ip.addr.hi>>(64-8) == 0xff // ip.v6(0) == 0xff
   572  	}
   573  	return false // zero value
   574  }
   575  
   576  // IsInterfaceLocalMulticast reports whether ip is an IPv6 interface-local
   577  // multicast address.
   578  func (ip Addr) IsInterfaceLocalMulticast() bool {
   579  	// IPv6 Addressing Architecture (2.7.1. Pre-Defined Multicast Addresses)
   580  	// https://datatracker.ietf.org/doc/html/rfc4291#section-2.7.1
   581  	if ip.Is6() && !ip.Is4In6() {
   582  		return ip.v6u16(0)&0xff0f == 0xff01
   583  	}
   584  	return false // zero value
   585  }
   586  
   587  // IsLinkLocalMulticast reports whether ip is a link-local multicast address.
   588  func (ip Addr) IsLinkLocalMulticast() bool {
   589  	if ip.Is4In6() {
   590  		ip = ip.Unmap()
   591  	}
   592  
   593  	// IPv4 Multicast Guidelines (4. Local Network Control Block (224.0.0/24))
   594  	// https://datatracker.ietf.org/doc/html/rfc5771#section-4
   595  	if ip.Is4() {
   596  		return ip.v4(0) == 224 && ip.v4(1) == 0 && ip.v4(2) == 0
   597  	}
   598  	// IPv6 Addressing Architecture (2.7.1. Pre-Defined Multicast Addresses)
   599  	// https://datatracker.ietf.org/doc/html/rfc4291#section-2.7.1
   600  	if ip.Is6() {
   601  		return ip.v6u16(0)&0xff0f == 0xff02
   602  	}
   603  	return false // zero value
   604  }
   605  
   606  // IsGlobalUnicast reports whether ip is a global unicast address.
   607  //
   608  // It returns true for IPv6 addresses which fall outside of the current
   609  // IANA-allocated 2000::/3 global unicast space, with the exception of the
   610  // link-local address space. It also returns true even if ip is in the IPv4
   611  // private address space or IPv6 unique local address space.
   612  // It returns false for the zero [Addr].
   613  //
   614  // For reference, see RFC 1122, RFC 4291, and RFC 4632.
   615  func (ip Addr) IsGlobalUnicast() bool {
   616  	if ip.z == z0 {
   617  		// Invalid or zero-value.
   618  		return false
   619  	}
   620  
   621  	if ip.Is4In6() {
   622  		ip = ip.Unmap()
   623  	}
   624  
   625  	// Match package net's IsGlobalUnicast logic. Notably private IPv4 addresses
   626  	// and ULA IPv6 addresses are still considered "global unicast".
   627  	if ip.Is4() && (ip == IPv4Unspecified() || ip == AddrFrom4([4]byte{255, 255, 255, 255})) {
   628  		return false
   629  	}
   630  
   631  	return ip != IPv6Unspecified() &&
   632  		!ip.IsLoopback() &&
   633  		!ip.IsMulticast() &&
   634  		!ip.IsLinkLocalUnicast()
   635  }
   636  
   637  // IsPrivate reports whether ip is a private address, according to RFC 1918
   638  // (IPv4 addresses) and RFC 4193 (IPv6 addresses). That is, it reports whether
   639  // ip is in 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, or fc00::/7. This is the
   640  // same as [net.IP.IsPrivate].
   641  func (ip Addr) IsPrivate() bool {
   642  	if ip.Is4In6() {
   643  		ip = ip.Unmap()
   644  	}
   645  
   646  	// Match the stdlib's IsPrivate logic.
   647  	if ip.Is4() {
   648  		// RFC 1918 allocates 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 as
   649  		// private IPv4 address subnets.
   650  		return ip.v4(0) == 10 ||
   651  			(ip.v4(0) == 172 && ip.v4(1)&0xf0 == 16) ||
   652  			(ip.v4(0) == 192 && ip.v4(1) == 168)
   653  	}
   654  
   655  	if ip.Is6() {
   656  		// RFC 4193 allocates fc00::/7 as the unique local unicast IPv6 address
   657  		// subnet.
   658  		return ip.v6(0)&0xfe == 0xfc
   659  	}
   660  
   661  	return false // zero value
   662  }
   663  
   664  // IsUnspecified reports whether ip is an unspecified address, either the IPv4
   665  // address "0.0.0.0" or the IPv6 address "::".
   666  //
   667  // Note that the zero [Addr] is not an unspecified address.
   668  func (ip Addr) IsUnspecified() bool {
   669  	return ip == IPv4Unspecified() || ip == IPv6Unspecified()
   670  }
   671  
   672  // Prefix keeps only the top b bits of IP, producing a Prefix
   673  // of the specified length.
   674  // If ip is a zero [Addr], Prefix always returns a zero Prefix and a nil error.
   675  // Otherwise, if bits is less than zero or greater than ip.BitLen(),
   676  // Prefix returns an error.
   677  func (ip Addr) Prefix(b int) (Prefix, error) {
   678  	if b < 0 {
   679  		return Prefix{}, errors.New("negative Prefix bits")
   680  	}
   681  	effectiveBits := b
   682  	switch ip.z {
   683  	case z0:
   684  		return Prefix{}, nil
   685  	case z4:
   686  		if b > 32 {
   687  			return Prefix{}, errors.New("prefix length " + itoa.Itoa(b) + " too large for IPv4")
   688  		}
   689  		effectiveBits += 96
   690  	default:
   691  		if b > 128 {
   692  			return Prefix{}, errors.New("prefix length " + itoa.Itoa(b) + " too large for IPv6")
   693  		}
   694  	}
   695  	ip.addr = ip.addr.and(mask6(effectiveBits))
   696  	return PrefixFrom(ip, b), nil
   697  }
   698  
   699  // As16 returns the IP address in its 16-byte representation.
   700  // IPv4 addresses are returned as IPv4-mapped IPv6 addresses.
   701  // IPv6 addresses with zones are returned without their zone (use the
   702  // [Addr.Zone] method to get it).
   703  // The ip zero value returns all zeroes.
   704  func (ip Addr) As16() (a16 [16]byte) {
   705  	byteorder.BePutUint64(a16[:8], ip.addr.hi)
   706  	byteorder.BePutUint64(a16[8:], ip.addr.lo)
   707  	return a16
   708  }
   709  
   710  // As4 returns an IPv4 or IPv4-in-IPv6 address in its 4-byte representation.
   711  // If ip is the zero [Addr] or an IPv6 address, As4 panics.
   712  // Note that 0.0.0.0 is not the zero Addr.
   713  func (ip Addr) As4() (a4 [4]byte) {
   714  	if ip.z == z4 || ip.Is4In6() {
   715  		byteorder.BePutUint32(a4[:], uint32(ip.addr.lo))
   716  		return a4
   717  	}
   718  	if ip.z == z0 {
   719  		panic("As4 called on IP zero value")
   720  	}
   721  	panic("As4 called on IPv6 address")
   722  }
   723  
   724  // AsSlice returns an IPv4 or IPv6 address in its respective 4-byte or 16-byte representation.
   725  func (ip Addr) AsSlice() []byte {
   726  	switch ip.z {
   727  	case z0:
   728  		return nil
   729  	case z4:
   730  		var ret [4]byte
   731  		byteorder.BePutUint32(ret[:], uint32(ip.addr.lo))
   732  		return ret[:]
   733  	default:
   734  		var ret [16]byte
   735  		byteorder.BePutUint64(ret[:8], ip.addr.hi)
   736  		byteorder.BePutUint64(ret[8:], ip.addr.lo)
   737  		return ret[:]
   738  	}
   739  }
   740  
   741  // Next returns the address following ip.
   742  // If there is none, it returns the zero [Addr].
   743  func (ip Addr) Next() Addr {
   744  	ip.addr = ip.addr.addOne()
   745  	if ip.Is4() {
   746  		if uint32(ip.addr.lo) == 0 {
   747  			// Overflowed.
   748  			return Addr{}
   749  		}
   750  	} else {
   751  		if ip.addr.isZero() {
   752  			// Overflowed
   753  			return Addr{}
   754  		}
   755  	}
   756  	return ip
   757  }
   758  
   759  // Prev returns the IP before ip.
   760  // If there is none, it returns the IP zero value.
   761  func (ip Addr) Prev() Addr {
   762  	if ip.Is4() {
   763  		if uint32(ip.addr.lo) == 0 {
   764  			return Addr{}
   765  		}
   766  	} else if ip.addr.isZero() {
   767  		return Addr{}
   768  	}
   769  	ip.addr = ip.addr.subOne()
   770  	return ip
   771  }
   772  
   773  // String returns the string form of the IP address ip.
   774  // It returns one of 5 forms:
   775  //
   776  //   - "invalid IP", if ip is the zero [Addr]
   777  //   - IPv4 dotted decimal ("192.0.2.1")
   778  //   - IPv6 ("2001:db8::1")
   779  //   - "::ffff:1.2.3.4" (if [Addr.Is4In6])
   780  //   - IPv6 with zone ("fe80:db8::1%eth0")
   781  //
   782  // Note that unlike package net's IP.String method,
   783  // IPv4-mapped IPv6 addresses format with a "::ffff:"
   784  // prefix before the dotted quad.
   785  func (ip Addr) String() string {
   786  	switch ip.z {
   787  	case z0:
   788  		return "invalid IP"
   789  	case z4:
   790  		return ip.string4()
   791  	default:
   792  		if ip.Is4In6() {
   793  			return ip.string4In6()
   794  		}
   795  		return ip.string6()
   796  	}
   797  }
   798  
   799  // AppendTo appends a text encoding of ip,
   800  // as generated by [Addr.MarshalText],
   801  // to b and returns the extended buffer.
   802  func (ip Addr) AppendTo(b []byte) []byte {
   803  	switch ip.z {
   804  	case z0:
   805  		return b
   806  	case z4:
   807  		return ip.appendTo4(b)
   808  	default:
   809  		if ip.Is4In6() {
   810  			return ip.appendTo4In6(b)
   811  		}
   812  		return ip.appendTo6(b)
   813  	}
   814  }
   815  
   816  // digits is a string of the hex digits from 0 to f. It's used in
   817  // appendDecimal and appendHex to format IP addresses.
   818  const digits = "0123456789abcdef"
   819  
   820  // appendDecimal appends the decimal string representation of x to b.
   821  func appendDecimal(b []byte, x uint8) []byte {
   822  	// Using this function rather than strconv.AppendUint makes IPv4
   823  	// string building 2x faster.
   824  
   825  	if x >= 100 {
   826  		b = append(b, digits[x/100])
   827  	}
   828  	if x >= 10 {
   829  		b = append(b, digits[x/10%10])
   830  	}
   831  	return append(b, digits[x%10])
   832  }
   833  
   834  // appendHex appends the hex string representation of x to b.
   835  func appendHex(b []byte, x uint16) []byte {
   836  	// Using this function rather than strconv.AppendUint makes IPv6
   837  	// string building 2x faster.
   838  
   839  	if x >= 0x1000 {
   840  		b = append(b, digits[x>>12])
   841  	}
   842  	if x >= 0x100 {
   843  		b = append(b, digits[x>>8&0xf])
   844  	}
   845  	if x >= 0x10 {
   846  		b = append(b, digits[x>>4&0xf])
   847  	}
   848  	return append(b, digits[x&0xf])
   849  }
   850  
   851  // appendHexPad appends the fully padded hex string representation of x to b.
   852  func appendHexPad(b []byte, x uint16) []byte {
   853  	return append(b, digits[x>>12], digits[x>>8&0xf], digits[x>>4&0xf], digits[x&0xf])
   854  }
   855  
   856  func (ip Addr) string4() string {
   857  	const max = len("255.255.255.255")
   858  	ret := make([]byte, 0, max)
   859  	ret = ip.appendTo4(ret)
   860  	return string(ret)
   861  }
   862  
   863  func (ip Addr) appendTo4(ret []byte) []byte {
   864  	ret = appendDecimal(ret, ip.v4(0))
   865  	ret = append(ret, '.')
   866  	ret = appendDecimal(ret, ip.v4(1))
   867  	ret = append(ret, '.')
   868  	ret = appendDecimal(ret, ip.v4(2))
   869  	ret = append(ret, '.')
   870  	ret = appendDecimal(ret, ip.v4(3))
   871  	return ret
   872  }
   873  
   874  func (ip Addr) string4In6() string {
   875  	const max = len("::ffff:255.255.255.255%enp5s0")
   876  	ret := make([]byte, 0, max)
   877  	ret = ip.appendTo4In6(ret)
   878  	return string(ret)
   879  }
   880  
   881  func (ip Addr) appendTo4In6(ret []byte) []byte {
   882  	ret = append(ret, "::ffff:"...)
   883  	ret = ip.Unmap().appendTo4(ret)
   884  	if ip.z != z6noz {
   885  		ret = append(ret, '%')
   886  		ret = append(ret, ip.Zone()...)
   887  	}
   888  	return ret
   889  }
   890  
   891  // string6 formats ip in IPv6 textual representation. It follows the
   892  // guidelines in section 4 of RFC 5952
   893  // (https://tools.ietf.org/html/rfc5952#section-4): no unnecessary
   894  // zeros, use :: to elide the longest run of zeros, and don't use ::
   895  // to compact a single zero field.
   896  func (ip Addr) string6() string {
   897  	// Use a zone with a "plausibly long" name, so that most zone-ful
   898  	// IP addresses won't require additional allocation.
   899  	//
   900  	// The compiler does a cool optimization here, where ret ends up
   901  	// stack-allocated and so the only allocation this function does
   902  	// is to construct the returned string. As such, it's okay to be a
   903  	// bit greedy here, size-wise.
   904  	const max = len("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff%enp5s0")
   905  	ret := make([]byte, 0, max)
   906  	ret = ip.appendTo6(ret)
   907  	return string(ret)
   908  }
   909  
   910  func (ip Addr) appendTo6(ret []byte) []byte {
   911  	zeroStart, zeroEnd := uint8(255), uint8(255)
   912  	for i := uint8(0); i < 8; i++ {
   913  		j := i
   914  		for j < 8 && ip.v6u16(j) == 0 {
   915  			j++
   916  		}
   917  		if l := j - i; l >= 2 && l > zeroEnd-zeroStart {
   918  			zeroStart, zeroEnd = i, j
   919  		}
   920  	}
   921  
   922  	for i := uint8(0); i < 8; i++ {
   923  		if i == zeroStart {
   924  			ret = append(ret, ':', ':')
   925  			i = zeroEnd
   926  			if i >= 8 {
   927  				break
   928  			}
   929  		} else if i > 0 {
   930  			ret = append(ret, ':')
   931  		}
   932  
   933  		ret = appendHex(ret, ip.v6u16(i))
   934  	}
   935  
   936  	if ip.z != z6noz {
   937  		ret = append(ret, '%')
   938  		ret = append(ret, ip.Zone()...)
   939  	}
   940  	return ret
   941  }
   942  
   943  // StringExpanded is like [Addr.String] but IPv6 addresses are expanded with leading
   944  // zeroes and no "::" compression. For example, "2001:db8::1" becomes
   945  // "2001:0db8:0000:0000:0000:0000:0000:0001".
   946  func (ip Addr) StringExpanded() string {
   947  	switch ip.z {
   948  	case z0, z4:
   949  		return ip.String()
   950  	}
   951  
   952  	const size = len("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff")
   953  	ret := make([]byte, 0, size)
   954  	for i := uint8(0); i < 8; i++ {
   955  		if i > 0 {
   956  			ret = append(ret, ':')
   957  		}
   958  
   959  		ret = appendHexPad(ret, ip.v6u16(i))
   960  	}
   961  
   962  	if ip.z != z6noz {
   963  		// The addition of a zone will cause a second allocation, but when there
   964  		// is no zone the ret slice will be stack allocated.
   965  		ret = append(ret, '%')
   966  		ret = append(ret, ip.Zone()...)
   967  	}
   968  	return string(ret)
   969  }
   970  
   971  // AppendText implements the [encoding.TextAppender] interface,
   972  // It is the same as [Addr.AppendTo].
   973  func (ip Addr) AppendText(b []byte) ([]byte, error) {
   974  	return ip.AppendTo(b), nil
   975  }
   976  
   977  // MarshalText implements the [encoding.TextMarshaler] interface,
   978  // The encoding is the same as returned by [Addr.String], with one exception:
   979  // If ip is the zero [Addr], the encoding is the empty string.
   980  func (ip Addr) MarshalText() ([]byte, error) {
   981  	buf := []byte{}
   982  	switch ip.z {
   983  	case z0:
   984  	case z4:
   985  		const maxCap = len("255.255.255.255")
   986  		buf = make([]byte, 0, maxCap)
   987  	default:
   988  		if ip.Is4In6() {
   989  			const maxCap = len("::ffff:255.255.255.255%enp5s0")
   990  			buf = make([]byte, 0, maxCap)
   991  			break
   992  		}
   993  		const maxCap = len("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff%enp5s0")
   994  		buf = make([]byte, 0, maxCap)
   995  	}
   996  	return ip.AppendText(buf)
   997  }
   998  
   999  // UnmarshalText implements the encoding.TextUnmarshaler interface.
  1000  // The IP address is expected in a form accepted by [ParseAddr].
  1001  //
  1002  // If text is empty, UnmarshalText sets *ip to the zero [Addr] and
  1003  // returns no error.
  1004  func (ip *Addr) UnmarshalText(text []byte) error {
  1005  	if len(text) == 0 {
  1006  		*ip = Addr{}
  1007  		return nil
  1008  	}
  1009  	var err error
  1010  	*ip, err = ParseAddr(string(text))
  1011  	return err
  1012  }
  1013  
  1014  // AppendBinary implements the [encoding.BinaryAppender] interface.
  1015  func (ip Addr) AppendBinary(b []byte) ([]byte, error) {
  1016  	switch ip.z {
  1017  	case z0:
  1018  	case z4:
  1019  		b = byteorder.BeAppendUint32(b, uint32(ip.addr.lo))
  1020  	default:
  1021  		b = byteorder.BeAppendUint64(b, ip.addr.hi)
  1022  		b = byteorder.BeAppendUint64(b, ip.addr.lo)
  1023  		b = append(b, ip.Zone()...)
  1024  	}
  1025  	return b, nil
  1026  }
  1027  
  1028  func (ip Addr) marshalBinarySize() int {
  1029  	switch ip.z {
  1030  	case z0:
  1031  		return 0
  1032  	case z4:
  1033  		return 4
  1034  	default:
  1035  		return 16 + len(ip.Zone())
  1036  	}
  1037  }
  1038  
  1039  // MarshalBinary implements the [encoding.BinaryMarshaler] interface.
  1040  // It returns a zero-length slice for the zero [Addr],
  1041  // the 4-byte form for an IPv4 address,
  1042  // and the 16-byte form with zone appended for an IPv6 address.
  1043  func (ip Addr) MarshalBinary() ([]byte, error) {
  1044  	return ip.AppendBinary(make([]byte, 0, ip.marshalBinarySize()))
  1045  }
  1046  
  1047  // UnmarshalBinary implements the [encoding.BinaryUnmarshaler] interface.
  1048  // It expects data in the form generated by MarshalBinary.
  1049  func (ip *Addr) UnmarshalBinary(b []byte) error {
  1050  	n := len(b)
  1051  	switch {
  1052  	case n == 0:
  1053  		*ip = Addr{}
  1054  		return nil
  1055  	case n == 4:
  1056  		*ip = AddrFrom4([4]byte(b))
  1057  		return nil
  1058  	case n == 16:
  1059  		*ip = AddrFrom16([16]byte(b))
  1060  		return nil
  1061  	case n > 16:
  1062  		*ip = AddrFrom16([16]byte(b[:16])).WithZone(string(b[16:]))
  1063  		return nil
  1064  	}
  1065  	return errors.New("unexpected slice size")
  1066  }
  1067  
  1068  // AddrPort is an IP and a port number.
  1069  type AddrPort struct {
  1070  	ip   Addr
  1071  	port uint16
  1072  }
  1073  
  1074  // AddrPortFrom returns an [AddrPort] with the provided IP and port.
  1075  // It does not allocate.
  1076  func AddrPortFrom(ip Addr, port uint16) AddrPort { return AddrPort{ip: ip, port: port} }
  1077  
  1078  // Addr returns p's IP address.
  1079  func (p AddrPort) Addr() Addr { return p.ip }
  1080  
  1081  // Port returns p's port.
  1082  func (p AddrPort) Port() uint16 { return p.port }
  1083  
  1084  // splitAddrPort splits s into an IP address string and a port
  1085  // string. It splits strings shaped like "foo:bar" or "[foo]:bar",
  1086  // without further validating the substrings. v6 indicates whether the
  1087  // ip string should parse as an IPv6 address or an IPv4 address, in
  1088  // order for s to be a valid ip:port string.
  1089  func splitAddrPort(s string) (ip, port string, v6 bool, err error) {
  1090  	i := bytealg.LastIndexByteString(s, ':')
  1091  	if i == -1 {
  1092  		return "", "", false, errors.New("not an ip:port")
  1093  	}
  1094  
  1095  	ip, port = s[:i], s[i+1:]
  1096  	if len(ip) == 0 {
  1097  		return "", "", false, errors.New("no IP")
  1098  	}
  1099  	if len(port) == 0 {
  1100  		return "", "", false, errors.New("no port")
  1101  	}
  1102  	if ip[0] == '[' {
  1103  		if len(ip) < 2 || ip[len(ip)-1] != ']' {
  1104  			return "", "", false, errors.New("missing ]")
  1105  		}
  1106  		ip = ip[1 : len(ip)-1]
  1107  		v6 = true
  1108  	}
  1109  
  1110  	return ip, port, v6, nil
  1111  }
  1112  
  1113  // ParseAddrPort parses s as an [AddrPort].
  1114  //
  1115  // It doesn't do any name resolution: both the address and the port
  1116  // must be numeric.
  1117  func ParseAddrPort(s string) (AddrPort, error) {
  1118  	var ipp AddrPort
  1119  	ip, port, v6, err := splitAddrPort(s)
  1120  	if err != nil {
  1121  		return ipp, err
  1122  	}
  1123  	port16, err := strconv.ParseUint(port, 10, 16)
  1124  	if err != nil {
  1125  		return ipp, errors.New("invalid port " + strconv.Quote(port) + " parsing " + strconv.Quote(s))
  1126  	}
  1127  	ipp.port = uint16(port16)
  1128  	ipp.ip, err = ParseAddr(ip)
  1129  	if err != nil {
  1130  		return AddrPort{}, err
  1131  	}
  1132  	if v6 && ipp.ip.Is4() {
  1133  		return AddrPort{}, errors.New("invalid ip:port " + strconv.Quote(s) + ", square brackets can only be used with IPv6 addresses")
  1134  	} else if !v6 && ipp.ip.Is6() {
  1135  		return AddrPort{}, errors.New("invalid ip:port " + strconv.Quote(s) + ", IPv6 addresses must be surrounded by square brackets")
  1136  	}
  1137  	return ipp, nil
  1138  }
  1139  
  1140  // MustParseAddrPort calls [ParseAddrPort](s) and panics on error.
  1141  // It is intended for use in tests with hard-coded strings.
  1142  func MustParseAddrPort(s string) AddrPort {
  1143  	ip, err := ParseAddrPort(s)
  1144  	if err != nil {
  1145  		panic(err)
  1146  	}
  1147  	return ip
  1148  }
  1149  
  1150  // IsValid reports whether p.Addr() is valid.
  1151  // All ports are valid, including zero.
  1152  func (p AddrPort) IsValid() bool { return p.ip.IsValid() }
  1153  
  1154  // Compare returns an integer comparing two AddrPorts.
  1155  // The result will be 0 if p == p2, -1 if p < p2, and +1 if p > p2.
  1156  // AddrPorts sort first by IP address, then port.
  1157  func (p AddrPort) Compare(p2 AddrPort) int {
  1158  	if c := p.Addr().Compare(p2.Addr()); c != 0 {
  1159  		return c
  1160  	}
  1161  	return cmp.Compare(p.Port(), p2.Port())
  1162  }
  1163  
  1164  func (p AddrPort) String() string {
  1165  	var b []byte
  1166  	switch p.ip.z {
  1167  	case z0:
  1168  		return "invalid AddrPort"
  1169  	case z4:
  1170  		const max = len("255.255.255.255:65535")
  1171  		b = make([]byte, 0, max)
  1172  		b = p.ip.appendTo4(b)
  1173  	default:
  1174  		if p.ip.Is4In6() {
  1175  			const max = len("[::ffff:255.255.255.255%enp5s0]:65535")
  1176  			b = make([]byte, 0, max)
  1177  			b = append(b, '[')
  1178  			b = p.ip.appendTo4In6(b)
  1179  		} else {
  1180  			const max = len("[ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff%enp5s0]:65535")
  1181  			b = make([]byte, 0, max)
  1182  			b = append(b, '[')
  1183  			b = p.ip.appendTo6(b)
  1184  		}
  1185  		b = append(b, ']')
  1186  	}
  1187  	b = append(b, ':')
  1188  	b = strconv.AppendUint(b, uint64(p.port), 10)
  1189  	return string(b)
  1190  }
  1191  
  1192  // AppendTo appends a text encoding of p,
  1193  // as generated by [AddrPort.MarshalText],
  1194  // to b and returns the extended buffer.
  1195  func (p AddrPort) AppendTo(b []byte) []byte {
  1196  	switch p.ip.z {
  1197  	case z0:
  1198  		return b
  1199  	case z4:
  1200  		b = p.ip.appendTo4(b)
  1201  	default:
  1202  		b = append(b, '[')
  1203  		if p.ip.Is4In6() {
  1204  			b = p.ip.appendTo4In6(b)
  1205  		} else {
  1206  			b = p.ip.appendTo6(b)
  1207  		}
  1208  		b = append(b, ']')
  1209  	}
  1210  	b = append(b, ':')
  1211  	b = strconv.AppendUint(b, uint64(p.port), 10)
  1212  	return b
  1213  }
  1214  
  1215  // AppendText implements the [encoding.TextAppender] interface. The
  1216  // encoding is the same as returned by [AddrPort.AppendTo].
  1217  func (p AddrPort) AppendText(b []byte) ([]byte, error) {
  1218  	return p.AppendTo(b), nil
  1219  }
  1220  
  1221  // MarshalText implements the [encoding.TextMarshaler] interface. The
  1222  // encoding is the same as returned by [AddrPort.String], with one exception: if
  1223  // p.Addr() is the zero [Addr], the encoding is the empty string.
  1224  func (p AddrPort) MarshalText() ([]byte, error) {
  1225  	buf := []byte{}
  1226  	switch p.ip.z {
  1227  	case z0:
  1228  	case z4:
  1229  		const maxCap = len("255.255.255.255:65535")
  1230  		buf = make([]byte, 0, maxCap)
  1231  	default:
  1232  		const maxCap = len("[ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff%enp5s0]:65535")
  1233  		buf = make([]byte, 0, maxCap)
  1234  	}
  1235  	return p.AppendText(buf)
  1236  }
  1237  
  1238  // UnmarshalText implements the encoding.TextUnmarshaler
  1239  // interface. The [AddrPort] is expected in a form
  1240  // generated by [AddrPort.MarshalText] or accepted by [ParseAddrPort].
  1241  func (p *AddrPort) UnmarshalText(text []byte) error {
  1242  	if len(text) == 0 {
  1243  		*p = AddrPort{}
  1244  		return nil
  1245  	}
  1246  	var err error
  1247  	*p, err = ParseAddrPort(string(text))
  1248  	return err
  1249  }
  1250  
  1251  // AppendBinary implements the [encoding.BinaryAppendler] interface.
  1252  // It returns [Addr.AppendBinary] with an additional two bytes appended
  1253  // containing the port in little-endian.
  1254  func (p AddrPort) AppendBinary(b []byte) ([]byte, error) {
  1255  	b, err := p.Addr().AppendBinary(b)
  1256  	if err != nil {
  1257  		return nil, err
  1258  	}
  1259  	return byteorder.LeAppendUint16(b, p.Port()), nil
  1260  }
  1261  
  1262  // MarshalBinary implements the [encoding.BinaryMarshaler] interface.
  1263  // It returns [Addr.MarshalBinary] with an additional two bytes appended
  1264  // containing the port in little-endian.
  1265  func (p AddrPort) MarshalBinary() ([]byte, error) {
  1266  	return p.AppendBinary(make([]byte, 0, p.Addr().marshalBinarySize()+2))
  1267  }
  1268  
  1269  // UnmarshalBinary implements the [encoding.BinaryUnmarshaler] interface.
  1270  // It expects data in the form generated by [AddrPort.MarshalBinary].
  1271  func (p *AddrPort) UnmarshalBinary(b []byte) error {
  1272  	if len(b) < 2 {
  1273  		return errors.New("unexpected slice size")
  1274  	}
  1275  	var addr Addr
  1276  	err := addr.UnmarshalBinary(b[:len(b)-2])
  1277  	if err != nil {
  1278  		return err
  1279  	}
  1280  	*p = AddrPortFrom(addr, byteorder.LeUint16(b[len(b)-2:]))
  1281  	return nil
  1282  }
  1283  
  1284  // Prefix is an IP address prefix (CIDR) representing an IP network.
  1285  //
  1286  // The first [Prefix.Bits]() of [Addr]() are specified. The remaining bits match any address.
  1287  // The range of Bits() is [0,32] for IPv4 or [0,128] for IPv6.
  1288  type Prefix struct {
  1289  	ip Addr
  1290  
  1291  	// bitsPlusOne stores the prefix bit length plus one.
  1292  	// A Prefix is valid if and only if bitsPlusOne is non-zero.
  1293  	bitsPlusOne uint8
  1294  }
  1295  
  1296  // PrefixFrom returns a [Prefix] with the provided IP address and bit
  1297  // prefix length.
  1298  //
  1299  // It does not allocate. Unlike [Addr.Prefix], [PrefixFrom] does not mask
  1300  // off the host bits of ip.
  1301  //
  1302  // If bits is less than zero or greater than ip.BitLen, [Prefix.Bits]
  1303  // will return an invalid value -1.
  1304  func PrefixFrom(ip Addr, bits int) Prefix {
  1305  	var bitsPlusOne uint8
  1306  	if !ip.isZero() && bits >= 0 && bits <= ip.BitLen() {
  1307  		bitsPlusOne = uint8(bits) + 1
  1308  	}
  1309  	return Prefix{
  1310  		ip:          ip.withoutZone(),
  1311  		bitsPlusOne: bitsPlusOne,
  1312  	}
  1313  }
  1314  
  1315  // Addr returns p's IP address.
  1316  func (p Prefix) Addr() Addr { return p.ip }
  1317  
  1318  // Bits returns p's prefix length.
  1319  //
  1320  // It reports -1 if invalid.
  1321  func (p Prefix) Bits() int { return int(p.bitsPlusOne) - 1 }
  1322  
  1323  // IsValid reports whether p.Bits() has a valid range for p.Addr().
  1324  // If p.Addr() is the zero [Addr], IsValid returns false.
  1325  // Note that if p is the zero [Prefix], then p.IsValid() == false.
  1326  func (p Prefix) IsValid() bool { return p.bitsPlusOne > 0 }
  1327  
  1328  func (p Prefix) isZero() bool { return p == Prefix{} }
  1329  
  1330  // IsSingleIP reports whether p contains exactly one IP.
  1331  func (p Prefix) IsSingleIP() bool { return p.IsValid() && p.Bits() == p.ip.BitLen() }
  1332  
  1333  // compare returns an integer comparing two prefixes.
  1334  // The result will be 0 if p == p2, -1 if p < p2, and +1 if p > p2.
  1335  // Prefixes sort first by validity (invalid before valid), then
  1336  // address family (IPv4 before IPv6), then prefix length, then
  1337  // address.
  1338  //
  1339  // Unexported for Go 1.22 because we may want to compare by p.Addr first.
  1340  // See post-acceptance discussion on go.dev/issue/61642.
  1341  func (p Prefix) compare(p2 Prefix) int {
  1342  	if c := cmp.Compare(p.Addr().BitLen(), p2.Addr().BitLen()); c != 0 {
  1343  		return c
  1344  	}
  1345  	if c := cmp.Compare(p.Bits(), p2.Bits()); c != 0 {
  1346  		return c
  1347  	}
  1348  	return p.Addr().Compare(p2.Addr())
  1349  }
  1350  
  1351  type parsePrefixError struct {
  1352  	in  string // the string given to ParsePrefix
  1353  	msg string // an explanation of the parse failure
  1354  }
  1355  
  1356  func (err parsePrefixError) Error() string {
  1357  	return "netip.ParsePrefix(" + strconv.Quote(err.in) + "): " + err.msg
  1358  }
  1359  
  1360  // ParsePrefix parses s as an IP address prefix.
  1361  // The string can be in the form "192.168.1.0/24" or "2001:db8::/32",
  1362  // the CIDR notation defined in RFC 4632 and RFC 4291.
  1363  // IPv6 zones are not permitted in prefixes, and an error will be returned if a
  1364  // zone is present.
  1365  //
  1366  // Note that masked address bits are not zeroed. Use Masked for that.
  1367  func ParsePrefix(s string) (Prefix, error) {
  1368  	i := bytealg.LastIndexByteString(s, '/')
  1369  	if i < 0 {
  1370  		return Prefix{}, parsePrefixError{in: s, msg: "no '/'"}
  1371  	}
  1372  	ip, err := ParseAddr(s[:i])
  1373  	if err != nil {
  1374  		return Prefix{}, parsePrefixError{in: s, msg: err.Error()}
  1375  	}
  1376  	// IPv6 zones are not allowed: https://go.dev/issue/51899
  1377  	if ip.Is6() && ip.z != z6noz {
  1378  		return Prefix{}, parsePrefixError{in: s, msg: "IPv6 zones cannot be present in a prefix"}
  1379  	}
  1380  
  1381  	bitsStr := s[i+1:]
  1382  
  1383  	// strconv.Atoi accepts a leading sign and leading zeroes, but we don't want that.
  1384  	if len(bitsStr) > 1 && (bitsStr[0] < '1' || bitsStr[0] > '9') {
  1385  		return Prefix{}, parsePrefixError{in: s, msg: "bad bits after slash: " + strconv.Quote(bitsStr)}
  1386  	}
  1387  
  1388  	bits, err := strconv.Atoi(bitsStr)
  1389  	if err != nil {
  1390  		return Prefix{}, parsePrefixError{in: s, msg: "bad bits after slash: " + strconv.Quote(bitsStr)}
  1391  	}
  1392  	maxBits := 32
  1393  	if ip.Is6() {
  1394  		maxBits = 128
  1395  	}
  1396  	if bits < 0 || bits > maxBits {
  1397  		return Prefix{}, parsePrefixError{in: s, msg: "prefix length out of range"}
  1398  	}
  1399  	return PrefixFrom(ip, bits), nil
  1400  }
  1401  
  1402  // MustParsePrefix calls [ParsePrefix](s) and panics on error.
  1403  // It is intended for use in tests with hard-coded strings.
  1404  func MustParsePrefix(s string) Prefix {
  1405  	ip, err := ParsePrefix(s)
  1406  	if err != nil {
  1407  		panic(err)
  1408  	}
  1409  	return ip
  1410  }
  1411  
  1412  // Masked returns p in its canonical form, with all but the high
  1413  // p.Bits() bits of p.Addr() masked off.
  1414  //
  1415  // If p is zero or otherwise invalid, Masked returns the zero [Prefix].
  1416  func (p Prefix) Masked() Prefix {
  1417  	m, _ := p.ip.Prefix(p.Bits())
  1418  	return m
  1419  }
  1420  
  1421  // Contains reports whether the network p includes ip.
  1422  //
  1423  // An IPv4 address will not match an IPv6 prefix.
  1424  // An IPv4-mapped IPv6 address will not match an IPv4 prefix.
  1425  // A zero-value IP will not match any prefix.
  1426  // If ip has an IPv6 zone, Contains returns false,
  1427  // because Prefixes strip zones.
  1428  func (p Prefix) Contains(ip Addr) bool {
  1429  	if !p.IsValid() || ip.hasZone() {
  1430  		return false
  1431  	}
  1432  	if f1, f2 := p.ip.BitLen(), ip.BitLen(); f1 == 0 || f2 == 0 || f1 != f2 {
  1433  		return false
  1434  	}
  1435  	if ip.Is4() {
  1436  		// xor the IP addresses together; mismatched bits are now ones.
  1437  		// Shift away the number of bits we don't care about.
  1438  		// Shifts in Go are more efficient if the compiler can prove
  1439  		// that the shift amount is smaller than the width of the shifted type (64 here).
  1440  		// We know that p.bits is in the range 0..32 because p is Valid;
  1441  		// the compiler doesn't know that, so mask with 63 to help it.
  1442  		// Now truncate to 32 bits, because this is IPv4.
  1443  		// If all the bits we care about are equal, the result will be zero.
  1444  		return uint32((ip.addr.lo^p.ip.addr.lo)>>((32-p.Bits())&63)) == 0
  1445  	} else {
  1446  		// xor the IP addresses together.
  1447  		// Mask away the bits we don't care about.
  1448  		// If all the bits we care about are equal, the result will be zero.
  1449  		return ip.addr.xor(p.ip.addr).and(mask6(p.Bits())).isZero()
  1450  	}
  1451  }
  1452  
  1453  // Overlaps reports whether p and o contain any IP addresses in common.
  1454  //
  1455  // If p and o are of different address families or either have a zero
  1456  // IP, it reports false. Like the Contains method, a prefix with an
  1457  // IPv4-mapped IPv6 address is still treated as an IPv6 mask.
  1458  func (p Prefix) Overlaps(o Prefix) bool {
  1459  	if !p.IsValid() || !o.IsValid() {
  1460  		return false
  1461  	}
  1462  	if p == o {
  1463  		return true
  1464  	}
  1465  	if p.ip.Is4() != o.ip.Is4() {
  1466  		return false
  1467  	}
  1468  	var minBits int
  1469  	if pb, ob := p.Bits(), o.Bits(); pb < ob {
  1470  		minBits = pb
  1471  	} else {
  1472  		minBits = ob
  1473  	}
  1474  	if minBits == 0 {
  1475  		return true
  1476  	}
  1477  	// One of these Prefix calls might look redundant, but we don't require
  1478  	// that p and o values are normalized (via Prefix.Masked) first,
  1479  	// so the Prefix call on the one that's already minBits serves to zero
  1480  	// out any remaining bits in IP.
  1481  	var err error
  1482  	if p, err = p.ip.Prefix(minBits); err != nil {
  1483  		return false
  1484  	}
  1485  	if o, err = o.ip.Prefix(minBits); err != nil {
  1486  		return false
  1487  	}
  1488  	return p.ip == o.ip
  1489  }
  1490  
  1491  // AppendTo appends a text encoding of p,
  1492  // as generated by [Prefix.MarshalText],
  1493  // to b and returns the extended buffer.
  1494  func (p Prefix) AppendTo(b []byte) []byte {
  1495  	if p.isZero() {
  1496  		return b
  1497  	}
  1498  	if !p.IsValid() {
  1499  		return append(b, "invalid Prefix"...)
  1500  	}
  1501  
  1502  	// p.ip is non-nil, because p is valid.
  1503  	if p.ip.z == z4 {
  1504  		b = p.ip.appendTo4(b)
  1505  	} else {
  1506  		if p.ip.Is4In6() {
  1507  			b = append(b, "::ffff:"...)
  1508  			b = p.ip.Unmap().appendTo4(b)
  1509  		} else {
  1510  			b = p.ip.appendTo6(b)
  1511  		}
  1512  	}
  1513  
  1514  	b = append(b, '/')
  1515  	b = appendDecimal(b, uint8(p.Bits()))
  1516  	return b
  1517  }
  1518  
  1519  // AppendText implements the [encoding.TextAppender] interface.
  1520  // It is the same as [Prefix.AppendTo].
  1521  func (p Prefix) AppendText(b []byte) ([]byte, error) {
  1522  	return p.AppendTo(b), nil
  1523  }
  1524  
  1525  // MarshalText implements the [encoding.TextMarshaler] interface,
  1526  // The encoding is the same as returned by [Prefix.String], with one exception:
  1527  // If p is the zero value, the encoding is the empty string.
  1528  func (p Prefix) MarshalText() ([]byte, error) {
  1529  	buf := []byte{}
  1530  	switch p.ip.z {
  1531  	case z0:
  1532  	case z4:
  1533  		const maxCap = len("255.255.255.255/32")
  1534  		buf = make([]byte, 0, maxCap)
  1535  	default:
  1536  		const maxCap = len("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff%enp5s0/128")
  1537  		buf = make([]byte, 0, maxCap)
  1538  	}
  1539  	return p.AppendText(buf)
  1540  }
  1541  
  1542  // UnmarshalText implements the encoding.TextUnmarshaler interface.
  1543  // The IP address is expected in a form accepted by [ParsePrefix]
  1544  // or generated by [Prefix.MarshalText].
  1545  func (p *Prefix) UnmarshalText(text []byte) error {
  1546  	if len(text) == 0 {
  1547  		*p = Prefix{}
  1548  		return nil
  1549  	}
  1550  	var err error
  1551  	*p, err = ParsePrefix(string(text))
  1552  	return err
  1553  }
  1554  
  1555  // AppendBinary implements the [encoding.AppendMarshaler] interface.
  1556  // It returns [Addr.AppendBinary] with an additional byte appended
  1557  // containing the prefix bits.
  1558  func (p Prefix) AppendBinary(b []byte) ([]byte, error) {
  1559  	b, err := p.Addr().withoutZone().AppendBinary(b)
  1560  	if err != nil {
  1561  		return nil, err
  1562  	}
  1563  	return append(b, uint8(p.Bits())), nil
  1564  }
  1565  
  1566  // MarshalBinary implements the [encoding.BinaryMarshaler] interface.
  1567  // It returns [Addr.MarshalBinary] with an additional byte appended
  1568  // containing the prefix bits.
  1569  func (p Prefix) MarshalBinary() ([]byte, error) {
  1570  	// without the zone the max length is 16, plus an additional byte is 17
  1571  	return p.AppendBinary(make([]byte, 0, p.Addr().withoutZone().marshalBinarySize()+1))
  1572  }
  1573  
  1574  // UnmarshalBinary implements the [encoding.BinaryUnmarshaler] interface.
  1575  // It expects data in the form generated by [Prefix.MarshalBinary].
  1576  func (p *Prefix) UnmarshalBinary(b []byte) error {
  1577  	if len(b) < 1 {
  1578  		return errors.New("unexpected slice size")
  1579  	}
  1580  	var addr Addr
  1581  	err := addr.UnmarshalBinary(b[:len(b)-1])
  1582  	if err != nil {
  1583  		return err
  1584  	}
  1585  	*p = PrefixFrom(addr, int(b[len(b)-1]))
  1586  	return nil
  1587  }
  1588  
  1589  // String returns the CIDR notation of p: "<ip>/<bits>".
  1590  func (p Prefix) String() string {
  1591  	if !p.IsValid() {
  1592  		return "invalid Prefix"
  1593  	}
  1594  	return p.ip.String() + "/" + itoa.Itoa(p.Bits())
  1595  }
  1596
View as plain text