github.com/m10x/go/src@v0.0.0-20220112094212-ba61592315da/net/ip.go (about) 1 // Copyright 2009 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 // IP address manipulations 6 // 7 // IPv4 addresses are 4 bytes; IPv6 addresses are 16 bytes. 8 // An IPv4 address can be converted to an IPv6 address by 9 // adding a canonical prefix (10 zeros, 2 0xFFs). 10 // This library accepts either size of byte slice but always 11 // returns 16-byte addresses. 12 13 package net 14 15 import ( 16 "internal/bytealg" 17 "internal/itoa" 18 ) 19 20 // IP address lengths (bytes). 21 const ( 22 IPv4len = 4 23 IPv6len = 16 24 ) 25 26 // An IP is a single IP address, a slice of bytes. 27 // Functions in this package accept either 4-byte (IPv4) 28 // or 16-byte (IPv6) slices as input. 29 // 30 // Note that in this documentation, referring to an 31 // IP address as an IPv4 address or an IPv6 address 32 // is a semantic property of the address, not just the 33 // length of the byte slice: a 16-byte slice can still 34 // be an IPv4 address. 35 type IP []byte 36 37 // An IPMask is a bitmask that can be used to manipulate 38 // IP addresses for IP addressing and routing. 39 // 40 // See type IPNet and func ParseCIDR for details. 41 type IPMask []byte 42 43 // An IPNet represents an IP network. 44 type IPNet struct { 45 IP IP // network number 46 Mask IPMask // network mask 47 } 48 49 // IPv4 returns the IP address (in 16-byte form) of the 50 // IPv4 address a.b.c.d. 51 func IPv4(a, b, c, d byte) IP { 52 p := make(IP, IPv6len) 53 copy(p, v4InV6Prefix) 54 p[12] = a 55 p[13] = b 56 p[14] = c 57 p[15] = d 58 return p 59 } 60 61 var v4InV6Prefix = []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff} 62 63 // IPv4Mask returns the IP mask (in 4-byte form) of the 64 // IPv4 mask a.b.c.d. 65 func IPv4Mask(a, b, c, d byte) IPMask { 66 p := make(IPMask, IPv4len) 67 p[0] = a 68 p[1] = b 69 p[2] = c 70 p[3] = d 71 return p 72 } 73 74 // CIDRMask returns an IPMask consisting of 'ones' 1 bits 75 // followed by 0s up to a total length of 'bits' bits. 76 // For a mask of this form, CIDRMask is the inverse of IPMask.Size. 77 func CIDRMask(ones, bits int) IPMask { 78 if bits != 8*IPv4len && bits != 8*IPv6len { 79 return nil 80 } 81 if ones < 0 || ones > bits { 82 return nil 83 } 84 l := bits / 8 85 m := make(IPMask, l) 86 n := uint(ones) 87 for i := 0; i < l; i++ { 88 if n >= 8 { 89 m[i] = 0xff 90 n -= 8 91 continue 92 } 93 m[i] = ^byte(0xff >> n) 94 n = 0 95 } 96 return m 97 } 98 99 // Well-known IPv4 addresses 100 var ( 101 IPv4bcast = IPv4(255, 255, 255, 255) // limited broadcast 102 IPv4allsys = IPv4(224, 0, 0, 1) // all systems 103 IPv4allrouter = IPv4(224, 0, 0, 2) // all routers 104 IPv4zero = IPv4(0, 0, 0, 0) // all zeros 105 ) 106 107 // Well-known IPv6 addresses 108 var ( 109 IPv6zero = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0} 110 IPv6unspecified = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0} 111 IPv6loopback = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1} 112 IPv6interfacelocalallnodes = IP{0xff, 0x01, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x01} 113 IPv6linklocalallnodes = IP{0xff, 0x02, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x01} 114 IPv6linklocalallrouters = IP{0xff, 0x02, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x02} 115 ) 116 117 // IsUnspecified reports whether ip is an unspecified address, either 118 // the IPv4 address "0.0.0.0" or the IPv6 address "::". 119 func (ip IP) IsUnspecified() bool { 120 return ip.Equal(IPv4zero) || ip.Equal(IPv6unspecified) 121 } 122 123 // IsLoopback reports whether ip is a loopback address. 124 func (ip IP) IsLoopback() bool { 125 if ip4 := ip.To4(); ip4 != nil { 126 return ip4[0] == 127 127 } 128 return ip.Equal(IPv6loopback) 129 } 130 131 // IsPrivate reports whether ip is a private address, according to 132 // RFC 1918 (IPv4 addresses) and RFC 4193 (IPv6 addresses). 133 func (ip IP) IsPrivate() bool { 134 if ip4 := ip.To4(); ip4 != nil { 135 // Following RFC 1918, Section 3. Private Address Space which says: 136 // The Internet Assigned Numbers Authority (IANA) has reserved the 137 // following three blocks of the IP address space for private internets: 138 // 10.0.0.0 - 10.255.255.255 (10/8 prefix) 139 // 172.16.0.0 - 172.31.255.255 (172.16/12 prefix) 140 // 192.168.0.0 - 192.168.255.255 (192.168/16 prefix) 141 return ip4[0] == 10 || 142 (ip4[0] == 172 && ip4[1]&0xf0 == 16) || 143 (ip4[0] == 192 && ip4[1] == 168) 144 } 145 // Following RFC 4193, Section 8. IANA Considerations which says: 146 // The IANA has assigned the FC00::/7 prefix to "Unique Local Unicast". 147 return len(ip) == IPv6len && ip[0]&0xfe == 0xfc 148 } 149 150 // IsMulticast reports whether ip is a multicast address. 151 func (ip IP) IsMulticast() bool { 152 if ip4 := ip.To4(); ip4 != nil { 153 return ip4[0]&0xf0 == 0xe0 154 } 155 return len(ip) == IPv6len && ip[0] == 0xff 156 } 157 158 // IsInterfaceLocalMulticast reports whether ip is 159 // an interface-local multicast address. 160 func (ip IP) IsInterfaceLocalMulticast() bool { 161 return len(ip) == IPv6len && ip[0] == 0xff && ip[1]&0x0f == 0x01 162 } 163 164 // IsLinkLocalMulticast reports whether ip is a link-local 165 // multicast address. 166 func (ip IP) IsLinkLocalMulticast() bool { 167 if ip4 := ip.To4(); ip4 != nil { 168 return ip4[0] == 224 && ip4[1] == 0 && ip4[2] == 0 169 } 170 return len(ip) == IPv6len && ip[0] == 0xff && ip[1]&0x0f == 0x02 171 } 172 173 // IsLinkLocalUnicast reports whether ip is a link-local 174 // unicast address. 175 func (ip IP) IsLinkLocalUnicast() bool { 176 if ip4 := ip.To4(); ip4 != nil { 177 return ip4[0] == 169 && ip4[1] == 254 178 } 179 return len(ip) == IPv6len && ip[0] == 0xfe && ip[1]&0xc0 == 0x80 180 } 181 182 // IsGlobalUnicast reports whether ip is a global unicast 183 // address. 184 // 185 // The identification of global unicast addresses uses address type 186 // identification as defined in RFC 1122, RFC 4632 and RFC 4291 with 187 // the exception of IPv4 directed broadcast addresses. 188 // It returns true even if ip is in IPv4 private address space or 189 // local IPv6 unicast address space. 190 func (ip IP) IsGlobalUnicast() bool { 191 return (len(ip) == IPv4len || len(ip) == IPv6len) && 192 !ip.Equal(IPv4bcast) && 193 !ip.IsUnspecified() && 194 !ip.IsLoopback() && 195 !ip.IsMulticast() && 196 !ip.IsLinkLocalUnicast() 197 } 198 199 // Is p all zeros? 200 func isZeros(p IP) bool { 201 for i := 0; i < len(p); i++ { 202 if p[i] != 0 { 203 return false 204 } 205 } 206 return true 207 } 208 209 // To4 converts the IPv4 address ip to a 4-byte representation. 210 // If ip is not an IPv4 address, To4 returns nil. 211 func (ip IP) To4() IP { 212 if len(ip) == IPv4len { 213 return ip 214 } 215 if len(ip) == IPv6len && 216 isZeros(ip[0:10]) && 217 ip[10] == 0xff && 218 ip[11] == 0xff { 219 return ip[12:16] 220 } 221 return nil 222 } 223 224 // To16 converts the IP address ip to a 16-byte representation. 225 // If ip is not an IP address (it is the wrong length), To16 returns nil. 226 func (ip IP) To16() IP { 227 if len(ip) == IPv4len { 228 return IPv4(ip[0], ip[1], ip[2], ip[3]) 229 } 230 if len(ip) == IPv6len { 231 return ip 232 } 233 return nil 234 } 235 236 // Default route masks for IPv4. 237 var ( 238 classAMask = IPv4Mask(0xff, 0, 0, 0) 239 classBMask = IPv4Mask(0xff, 0xff, 0, 0) 240 classCMask = IPv4Mask(0xff, 0xff, 0xff, 0) 241 ) 242 243 // DefaultMask returns the default IP mask for the IP address ip. 244 // Only IPv4 addresses have default masks; DefaultMask returns 245 // nil if ip is not a valid IPv4 address. 246 func (ip IP) DefaultMask() IPMask { 247 if ip = ip.To4(); ip == nil { 248 return nil 249 } 250 switch { 251 case ip[0] < 0x80: 252 return classAMask 253 case ip[0] < 0xC0: 254 return classBMask 255 default: 256 return classCMask 257 } 258 } 259 260 func allFF(b []byte) bool { 261 for _, c := range b { 262 if c != 0xff { 263 return false 264 } 265 } 266 return true 267 } 268 269 // Mask returns the result of masking the IP address ip with mask. 270 func (ip IP) Mask(mask IPMask) IP { 271 if len(mask) == IPv6len && len(ip) == IPv4len && allFF(mask[:12]) { 272 mask = mask[12:] 273 } 274 if len(mask) == IPv4len && len(ip) == IPv6len && bytealg.Equal(ip[:12], v4InV6Prefix) { 275 ip = ip[12:] 276 } 277 n := len(ip) 278 if n != len(mask) { 279 return nil 280 } 281 out := make(IP, n) 282 for i := 0; i < n; i++ { 283 out[i] = ip[i] & mask[i] 284 } 285 return out 286 } 287 288 // ubtoa encodes the string form of the integer v to dst[start:] and 289 // returns the number of bytes written to dst. The caller must ensure 290 // that dst has sufficient length. 291 func ubtoa(dst []byte, start int, v byte) int { 292 if v < 10 { 293 dst[start] = v + '0' 294 return 1 295 } else if v < 100 { 296 dst[start+1] = v%10 + '0' 297 dst[start] = v/10 + '0' 298 return 2 299 } 300 301 dst[start+2] = v%10 + '0' 302 dst[start+1] = (v/10)%10 + '0' 303 dst[start] = v/100 + '0' 304 return 3 305 } 306 307 // String returns the string form of the IP address ip. 308 // It returns one of 4 forms: 309 // - "<nil>", if ip has length 0 310 // - dotted decimal ("192.0.2.1"), if ip is an IPv4 or IP4-mapped IPv6 address 311 // - IPv6 conforming to RFC 5952 ("2001:db8::1"), if ip is a valid IPv6 address 312 // - the hexadecimal form of ip, without punctuation, if no other cases apply 313 func (ip IP) String() string { 314 p := ip 315 316 if len(ip) == 0 { 317 return "<nil>" 318 } 319 320 // If IPv4, use dotted notation. 321 if p4 := p.To4(); len(p4) == IPv4len { 322 const maxIPv4StringLen = len("255.255.255.255") 323 b := make([]byte, maxIPv4StringLen) 324 325 n := ubtoa(b, 0, p4[0]) 326 b[n] = '.' 327 n++ 328 329 n += ubtoa(b, n, p4[1]) 330 b[n] = '.' 331 n++ 332 333 n += ubtoa(b, n, p4[2]) 334 b[n] = '.' 335 n++ 336 337 n += ubtoa(b, n, p4[3]) 338 return string(b[:n]) 339 } 340 if len(p) != IPv6len { 341 return "?" + hexString(ip) 342 } 343 344 // Find longest run of zeros. 345 e0 := -1 346 e1 := -1 347 for i := 0; i < IPv6len; i += 2 { 348 j := i 349 for j < IPv6len && p[j] == 0 && p[j+1] == 0 { 350 j += 2 351 } 352 if j > i && j-i > e1-e0 { 353 e0 = i 354 e1 = j 355 i = j 356 } 357 } 358 // The symbol "::" MUST NOT be used to shorten just one 16 bit 0 field. 359 if e1-e0 <= 2 { 360 e0 = -1 361 e1 = -1 362 } 363 364 const maxLen = len("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff") 365 b := make([]byte, 0, maxLen) 366 367 // Print with possible :: in place of run of zeros 368 for i := 0; i < IPv6len; i += 2 { 369 if i == e0 { 370 b = append(b, ':', ':') 371 i = e1 372 if i >= IPv6len { 373 break 374 } 375 } else if i > 0 { 376 b = append(b, ':') 377 } 378 b = appendHex(b, (uint32(p[i])<<8)|uint32(p[i+1])) 379 } 380 return string(b) 381 } 382 383 func hexString(b []byte) string { 384 s := make([]byte, len(b)*2) 385 for i, tn := range b { 386 s[i*2], s[i*2+1] = hexDigit[tn>>4], hexDigit[tn&0xf] 387 } 388 return string(s) 389 } 390 391 // ipEmptyString is like ip.String except that it returns 392 // an empty string when ip is unset. 393 func ipEmptyString(ip IP) string { 394 if len(ip) == 0 { 395 return "" 396 } 397 return ip.String() 398 } 399 400 // MarshalText implements the encoding.TextMarshaler interface. 401 // The encoding is the same as returned by String, with one exception: 402 // When len(ip) is zero, it returns an empty slice. 403 func (ip IP) MarshalText() ([]byte, error) { 404 if len(ip) == 0 { 405 return []byte(""), nil 406 } 407 if len(ip) != IPv4len && len(ip) != IPv6len { 408 return nil, &AddrError{Err: "invalid IP address", Addr: hexString(ip)} 409 } 410 return []byte(ip.String()), nil 411 } 412 413 // UnmarshalText implements the encoding.TextUnmarshaler interface. 414 // The IP address is expected in a form accepted by ParseIP. 415 func (ip *IP) UnmarshalText(text []byte) error { 416 if len(text) == 0 { 417 *ip = nil 418 return nil 419 } 420 s := string(text) 421 x := ParseIP(s) 422 if x == nil { 423 return &ParseError{Type: "IP address", Text: s} 424 } 425 *ip = x 426 return nil 427 } 428 429 // Equal reports whether ip and x are the same IP address. 430 // An IPv4 address and that same address in IPv6 form are 431 // considered to be equal. 432 func (ip IP) Equal(x IP) bool { 433 if len(ip) == len(x) { 434 return bytealg.Equal(ip, x) 435 } 436 if len(ip) == IPv4len && len(x) == IPv6len { 437 return bytealg.Equal(x[0:12], v4InV6Prefix) && bytealg.Equal(ip, x[12:]) 438 } 439 if len(ip) == IPv6len && len(x) == IPv4len { 440 return bytealg.Equal(ip[0:12], v4InV6Prefix) && bytealg.Equal(ip[12:], x) 441 } 442 return false 443 } 444 445 func (ip IP) matchAddrFamily(x IP) bool { 446 return ip.To4() != nil && x.To4() != nil || ip.To16() != nil && ip.To4() == nil && x.To16() != nil && x.To4() == nil 447 } 448 449 // If mask is a sequence of 1 bits followed by 0 bits, 450 // return the number of 1 bits. 451 func simpleMaskLength(mask IPMask) int { 452 var n int 453 for i, v := range mask { 454 if v == 0xff { 455 n += 8 456 continue 457 } 458 // found non-ff byte 459 // count 1 bits 460 for v&0x80 != 0 { 461 n++ 462 v <<= 1 463 } 464 // rest must be 0 bits 465 if v != 0 { 466 return -1 467 } 468 for i++; i < len(mask); i++ { 469 if mask[i] != 0 { 470 return -1 471 } 472 } 473 break 474 } 475 return n 476 } 477 478 // Size returns the number of leading ones and total bits in the mask. 479 // If the mask is not in the canonical form--ones followed by zeros--then 480 // Size returns 0, 0. 481 func (m IPMask) Size() (ones, bits int) { 482 ones, bits = simpleMaskLength(m), len(m)*8 483 if ones == -1 { 484 return 0, 0 485 } 486 return 487 } 488 489 // String returns the hexadecimal form of m, with no punctuation. 490 func (m IPMask) String() string { 491 if len(m) == 0 { 492 return "<nil>" 493 } 494 return hexString(m) 495 } 496 497 func networkNumberAndMask(n *IPNet) (ip IP, m IPMask) { 498 if ip = n.IP.To4(); ip == nil { 499 ip = n.IP 500 if len(ip) != IPv6len { 501 return nil, nil 502 } 503 } 504 m = n.Mask 505 switch len(m) { 506 case IPv4len: 507 if len(ip) != IPv4len { 508 return nil, nil 509 } 510 case IPv6len: 511 if len(ip) == IPv4len { 512 m = m[12:] 513 } 514 default: 515 return nil, nil 516 } 517 return 518 } 519 520 // Contains reports whether the network includes ip. 521 func (n *IPNet) Contains(ip IP) bool { 522 nn, m := networkNumberAndMask(n) 523 if x := ip.To4(); x != nil { 524 ip = x 525 } 526 l := len(ip) 527 if l != len(nn) { 528 return false 529 } 530 for i := 0; i < l; i++ { 531 if nn[i]&m[i] != ip[i]&m[i] { 532 return false 533 } 534 } 535 return true 536 } 537 538 // Network returns the address's network name, "ip+net". 539 func (n *IPNet) Network() string { return "ip+net" } 540 541 // String returns the CIDR notation of n like "192.0.2.0/24" 542 // or "2001:db8::/48" as defined in RFC 4632 and RFC 4291. 543 // If the mask is not in the canonical form, it returns the 544 // string which consists of an IP address, followed by a slash 545 // character and a mask expressed as hexadecimal form with no 546 // punctuation like "198.51.100.0/c000ff00". 547 func (n *IPNet) String() string { 548 if n == nil { 549 return "<nil>" 550 } 551 nn, m := networkNumberAndMask(n) 552 if nn == nil || m == nil { 553 return "<nil>" 554 } 555 l := simpleMaskLength(m) 556 if l == -1 { 557 return nn.String() + "/" + m.String() 558 } 559 return nn.String() + "/" + itoa.Uitoa(uint(l)) 560 } 561 562 // Parse IPv4 address (d.d.d.d). 563 func parseIPv4(s string) IP { 564 var p [IPv4len]byte 565 for i := 0; i < IPv4len; i++ { 566 if len(s) == 0 { 567 // Missing octets. 568 return nil 569 } 570 if i > 0 { 571 if s[0] != '.' { 572 return nil 573 } 574 s = s[1:] 575 } 576 n, c, ok := dtoi(s) 577 if !ok || n > 0xFF { 578 return nil 579 } 580 if c > 1 && s[0] == '0' { 581 // Reject non-zero components with leading zeroes. 582 return nil 583 } 584 s = s[c:] 585 p[i] = byte(n) 586 } 587 if len(s) != 0 { 588 return nil 589 } 590 return IPv4(p[0], p[1], p[2], p[3]) 591 } 592 593 // parseIPv6Zone parses s as a literal IPv6 address and its associated zone 594 // identifier which is described in RFC 4007. 595 func parseIPv6Zone(s string) (IP, string) { 596 s, zone := splitHostZone(s) 597 return parseIPv6(s), zone 598 } 599 600 // parseIPv6 parses s as a literal IPv6 address described in RFC 4291 601 // and RFC 5952. 602 func parseIPv6(s string) (ip IP) { 603 ip = make(IP, IPv6len) 604 ellipsis := -1 // position of ellipsis in ip 605 606 // Might have leading ellipsis 607 if len(s) >= 2 && s[0] == ':' && s[1] == ':' { 608 ellipsis = 0 609 s = s[2:] 610 // Might be only ellipsis 611 if len(s) == 0 { 612 return ip 613 } 614 } 615 616 // Loop, parsing hex numbers followed by colon. 617 i := 0 618 for i < IPv6len { 619 // Hex number. 620 n, c, ok := xtoi(s) 621 if !ok || n > 0xFFFF { 622 return nil 623 } 624 625 // If followed by dot, might be in trailing IPv4. 626 if c < len(s) && s[c] == '.' { 627 if ellipsis < 0 && i != IPv6len-IPv4len { 628 // Not the right place. 629 return nil 630 } 631 if i+IPv4len > IPv6len { 632 // Not enough room. 633 return nil 634 } 635 ip4 := parseIPv4(s) 636 if ip4 == nil { 637 return nil 638 } 639 ip[i] = ip4[12] 640 ip[i+1] = ip4[13] 641 ip[i+2] = ip4[14] 642 ip[i+3] = ip4[15] 643 s = "" 644 i += IPv4len 645 break 646 } 647 648 // Save this 16-bit chunk. 649 ip[i] = byte(n >> 8) 650 ip[i+1] = byte(n) 651 i += 2 652 653 // Stop at end of string. 654 s = s[c:] 655 if len(s) == 0 { 656 break 657 } 658 659 // Otherwise must be followed by colon and more. 660 if s[0] != ':' || len(s) == 1 { 661 return nil 662 } 663 s = s[1:] 664 665 // Look for ellipsis. 666 if s[0] == ':' { 667 if ellipsis >= 0 { // already have one 668 return nil 669 } 670 ellipsis = i 671 s = s[1:] 672 if len(s) == 0 { // can be at end 673 break 674 } 675 } 676 } 677 678 // Must have used entire string. 679 if len(s) != 0 { 680 return nil 681 } 682 683 // If didn't parse enough, expand ellipsis. 684 if i < IPv6len { 685 if ellipsis < 0 { 686 return nil 687 } 688 n := IPv6len - i 689 for j := i - 1; j >= ellipsis; j-- { 690 ip[j+n] = ip[j] 691 } 692 for j := ellipsis + n - 1; j >= ellipsis; j-- { 693 ip[j] = 0 694 } 695 } else if ellipsis >= 0 { 696 // Ellipsis must represent at least one 0 group. 697 return nil 698 } 699 return ip 700 } 701 702 // ParseIP parses s as an IP address, returning the result. 703 // The string s can be in IPv4 dotted decimal ("192.0.2.1"), IPv6 704 // ("2001:db8::68"), or IPv4-mapped IPv6 ("::ffff:192.0.2.1") form. 705 // If s is not a valid textual representation of an IP address, 706 // ParseIP returns nil. 707 func ParseIP(s string) IP { 708 for i := 0; i < len(s); i++ { 709 switch s[i] { 710 case '.': 711 return parseIPv4(s) 712 case ':': 713 return parseIPv6(s) 714 } 715 } 716 return nil 717 } 718 719 // parseIPZone parses s as an IP address, return it and its associated zone 720 // identifier (IPv6 only). 721 func parseIPZone(s string) (IP, string) { 722 for i := 0; i < len(s); i++ { 723 switch s[i] { 724 case '.': 725 return parseIPv4(s), "" 726 case ':': 727 return parseIPv6Zone(s) 728 } 729 } 730 return nil, "" 731 } 732 733 // ParseCIDR parses s as a CIDR notation IP address and prefix length, 734 // like "192.0.2.0/24" or "2001:db8::/32", as defined in 735 // RFC 4632 and RFC 4291. 736 // 737 // It returns the IP address and the network implied by the IP and 738 // prefix length. 739 // For example, ParseCIDR("192.0.2.1/24") returns the IP address 740 // 192.0.2.1 and the network 192.0.2.0/24. 741 func ParseCIDR(s string) (IP, *IPNet, error) { 742 i := bytealg.IndexByteString(s, '/') 743 if i < 0 { 744 return nil, nil, &ParseError{Type: "CIDR address", Text: s} 745 } 746 addr, mask := s[:i], s[i+1:] 747 iplen := IPv4len 748 ip := parseIPv4(addr) 749 if ip == nil { 750 iplen = IPv6len 751 ip = parseIPv6(addr) 752 } 753 n, i, ok := dtoi(mask) 754 if ip == nil || !ok || i != len(mask) || n < 0 || n > 8*iplen { 755 return nil, nil, &ParseError{Type: "CIDR address", Text: s} 756 } 757 m := CIDRMask(n, 8*iplen) 758 return ip, &IPNet{IP: ip.Mask(m), Mask: m}, nil 759 }