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If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner] 6 .TH GETIPNODEBYNAME 3SOCKET "Sep 10, 2013" 7 .SH NAME 8 getipnodebyname, getipnodebyaddr, freehostent \- get IP node entry 9 .SH SYNOPSIS 10 .LP 11 .nf 12 \fBcc\fR [ \fIflag\fR... ] \fIfile\fR... \fB-lsocket\fR \fB -lnsl \fR [ \fIlibrary\fR... ] 13 #include <sys/socket.h> 14 #include <netdb.h> 15 16 \fBstruct hostent *\fR\fBgetipnodebyname\fR(\fBconst char *\fR\fIname\fR, \fBint\fR \fIaf\fR, 17 \fBint\fR \fIflags\fR, \fBint *\fR\fIerror_num\fR); 18 .fi 19 20 .LP 21 .nf 22 \fBstruct hostent *\fR\fBgetipnodebyaddr\fR(\fBconst void *\fR\fIsrc\fR, \fBsize_t\fR \fIlen\fR, 23 \fBint\fR \fIaf\fR, \fBint *\fR\fIerror_num\fR); 24 .fi 25 26 .LP 27 .nf 28 \fBvoid\fR \fBfreehostent\fR(\fBstruct hostent *\fR\fIptr\fR); 29 .fi 30 31 .SH PARAMETERS 32 .sp 33 .ne 2 34 .na 35 \fB\fIaf\fR\fR 36 .ad 37 .RS 13n 38 Address family 39 .RE 40 41 .sp 42 .ne 2 43 .na 44 \fB\fIflags\fR\fR 45 .ad 46 .RS 13n 47 Various flags 48 .RE 49 50 .sp 51 .ne 2 52 .na 53 \fB\fIname\fR\fR 54 .ad 55 .RS 13n 56 Name of host 57 .RE 58 59 .sp 60 .ne 2 61 .na 62 \fB\fIerror_num\fR\fR 63 .ad 64 .RS 13n 65 Error storage 66 .RE 67 68 .sp 69 .ne 2 70 .na 71 \fB\fIsrc\fR\fR 72 .ad 73 .RS 13n 74 Address for lookup 75 .RE 76 77 .sp 78 .ne 2 79 .na 80 \fB\fIlen\fR\fR 81 .ad 82 .RS 13n 83 Length of address 84 .RE 85 86 .sp 87 .ne 2 88 .na 89 \fB\fIptr\fR\fR 90 .ad 91 .RS 13n 92 Pointer to \fBhostent\fR structure 93 .RE 94 95 .SH DESCRIPTION 96 .sp 97 .LP 98 The \fBgetipnodebyname()\fR function searches the \fBipnodes\fR database from 99 the beginning. The function finds the first \fBh_name\fR member that matches 100 the hostname specified by \fIname\fR. The function takes an \fIaf\fR argument 101 that specifies the address family. The address family can be \fBAF_INET\fR for 102 IPv4 addresses or \fBAF_INET6\fR for IPv6 addresses. The \fIflags\fR argument 103 determines what results are returned based on the value of \fIflags\fR. If the 104 \fIflags\fR argument is set to \fB0\fR (zero), the default operation of the 105 function is specified as follows: 106 .RS +4 107 .TP 108 .ie t \(bu 109 .el o 110 If the \fIaf\fR argument is \fBAF_INET\fR, a query is made for an IPv4 address. 111 If successful, IPv4 addresses are returned and the \fBh_length\fR member of the 112 \fBhostent\fR structure is 4. Otherwise, the function returns a \fINULL\fR 113 pointer. 114 .RE 115 .RS +4 116 .TP 117 .ie t \(bu 118 .el o 119 If the \fIaf\fR argument is \fBAF_INET6\fR, a query is made for an IPv6 120 address. If successful, IPv6 addresses are returned and the \fBh_length\fR 121 member of the \fBhostent\fR structure is 16. Otherwise, the function returns a 122 \fINULL\fR pointer. 123 .RE 124 .sp 125 .LP 126 The \fIflags\fR argument changes the default actions of the function. Set the 127 \fIflags\fR argument with a logical \fBOR\fR operation on any of combination of 128 the following values: 129 .RS +4 130 .TP 131 .ie t \(bu 132 .el o 133 \fBAI_V4MAPPED\fR 134 .RE 135 .RS +4 136 .TP 137 .ie t \(bu 138 .el o 139 \fBAI_ALL\fR 140 .RE 141 .RS +4 142 .TP 143 .ie t \(bu 144 .el o 145 \fBAI_ADDRCONFIG\fR 146 .RE 147 .sp 148 .LP 149 The special flags value, \fBAI_DEFAULT\fR, should handle most applications. 150 Porting simple applications to use IPv6 replaces the call 151 .sp 152 .in +2 153 .nf 154 hptr = gethostbyname(name); 155 .fi 156 .in -2 157 158 .sp 159 .LP 160 with 161 .sp 162 .in +2 163 .nf 164 hptr = getipnodebyname(name, AF_INET6, AI_DEFAULT, &error_num); 165 .fi 166 .in -2 167 168 .sp 169 .LP 170 The \fIflags\fR value \fB0\fR (zero) implies a strict interpretation of the 171 \fIaf\fR argument: 172 .RS +4 173 .TP 174 .ie t \(bu 175 .el o 176 If \fIflags\fR is \fB0\fR and \fIaf\fR is \fBAF_INET\fR, the caller wants only 177 IPv4 addresses. A query is made for \fBA\fR records. If successful, IPv4 178 addresses are returned and the \fBh_length\fR member of the \fBhostent\fR 179 structure is 4. Otherwise, the function returns a \fINULL\fR pointer. 180 .RE 181 .RS +4 182 .TP 183 .ie t \(bu 184 .el o 185 If \fIflags\fR is \fB0\fR and \fIaf\fR is \fBAF_INET6\fR, the caller wants only 186 IPv6 addresses. A query is made for \fBAAAA\fR records. If successful, IPv6 187 addresses are returned and the \fBh_length\fR member of the \fBhostent\fR 188 structure is 16. Otherwise, the function returns a \fINULL\fR pointer. 189 .RE 190 .sp 191 .LP 192 Logically \fBOR\fR other constants into the \fIflags\fR argument to modify the 193 behavior of the \fBgetipnodebyname()\fR function. 194 .RS +4 195 .TP 196 .ie t \(bu 197 .el o 198 If the \fBAI_V4MAPPED\fR flag is specified with \fIaf\fR set to \fBAF_INET6\fR, 199 the caller can accept IPv4-mapped IPv6 addresses. If no \fBAAAA\fR records are 200 found, a query is made for \fBA\fR records. Any \fBA\fR records found are 201 returned as IPv4-mapped IPv6 addresses and the \fBh_length\fR is 16. The 202 \fBAI_V4MAPPED\fR flag is ignored unless \fIaf\fR equals \fBAF_INET6\fR. 203 .RE 204 .RS +4 205 .TP 206 .ie t \(bu 207 .el o 208 The \fBAI_ALL\fR flag is used in conjunction with the \fBAI_V4MAPPED\fR flag, 209 exclusively with the IPv6 address family. When \fBAI_ALL\fR is logically 210 \fBOR\fRed with \fBAI_V4MAPPED\fR flag, the caller wants all addresses: IPv6 211 and IPv4-mapped IPv6 addresses. A query is first made for \fBAAAA\fR records 212 and, if successful, IPv6 addresses are returned. Another query is then made for 213 \fBA\fR records. Any \fBA\fR records found are returned as IPv4-mapped IPv6 214 addresses and the \fBh_length\fR is 16. Only when both queries fail does the 215 function return a \fINULL\fR pointer. The \fBAI_ALL\fR flag is ignored unless 216 \fIaf\fR is set to \fBAF_INET6\fR. 217 .RE 218 .RS +4 219 .TP 220 .ie t \(bu 221 .el o 222 The \fBAI_ADDRCONFIG\fR flag specifies that a query for \fBAAAA\fR records 223 should occur only when the node is configured with at least one IPv6 source 224 address. A query for \fBA\fR records should occur only when the node is 225 configured with at least one IPv4 source address. For example, if a node is 226 configured with no IPv6 source addresses, \fIaf\fR equals \fBAF_INET6\fR, and 227 the node name queried has both \fBAAAA\fR and \fBA\fR records, then: 228 .RS +4 229 .TP 230 .ie t \(bu 231 .el o 232 A \fINULL\fR pointer is returned when only the \fBAI_ADDRCONFIG\fR value is 233 specified. 234 .RE 235 .RS +4 236 .TP 237 .ie t \(bu 238 .el o 239 The \fBA\fR records are returned as IPv4-mapped IPv6 addresses when the 240 \fBAI_ADDRCONFIG\fR and \fBAI_V4MAPPED\fR values are specified. 241 .RE 242 .RE 243 .sp 244 .LP 245 The special flags value, \fBAI_DEFAULT\fR, is defined as 246 .sp 247 .in +2 248 .nf 249 #define AI_DEFAULT (AI_V4MAPPED | AI_ADDRCONFIG) 250 .fi 251 .in -2 252 253 .sp 254 .LP 255 The \fBgetipnodebyname()\fR function allows the \fIname\fR argument to be a 256 node name or a literal address string: a dotted-decimal IPv4 address or an IPv6 257 hex address. Applications do not have to call \fBinet_pton\fR(3SOCKET) to 258 handle literal address strings. 259 .sp 260 .LP 261 Four scenarios arise based on the type of literal address string and the value 262 of the \fIaf\fR argument. The two simple cases occur when \fIname\fR is a 263 dotted-decimal IPv4 address and \fIaf\fR equals \fBAF_INET\fR and when 264 \fIname\fR is an IPv6 hex address and \fIaf\fR equals \fBAF_INET6\fR. The 265 members of the returned \fBhostent\fR structure are: 266 .sp 267 .ne 2 268 .na 269 \fB\fBh_name\fR\fR 270 .ad 271 .RS 15n 272 Pointer to a copy of the name argument 273 .RE 274 275 .sp 276 .ne 2 277 .na 278 \fB\fBh_aliases\fR\fR 279 .ad 280 .RS 15n 281 \fINULL\fR pointer. 282 .RE 283 284 .sp 285 .ne 2 286 .na 287 \fB\fBh_addrtype\fR\fR 288 .ad 289 .RS 15n 290 Copy of the \fIaf\fR argument. 291 .RE 292 293 .sp 294 .ne 2 295 .na 296 \fB\fBh_length\fR\fR 297 .ad 298 .RS 15n 299 4 for \fBAF_INET\fR or 16 for \fBAF_INET6\fR. 300 .RE 301 302 .sp 303 .ne 2 304 .na 305 \fB\fBh_addr_list\fR\fR 306 .ad 307 .RS 15n 308 Array of pointers to 4-byte or 16-byte binary addresses. The array is 309 terminated by a \fINULL\fR pointer. 310 .RE 311 312 .SH RETURN VALUES 313 .sp 314 .LP 315 Upon successful completion, \fBgetipnodebyname()\fR and \fBgetipnodebyaddr()\fR 316 return a \fBhostent\fR structure. Otherwise they return \fINULL\fR. 317 .sp 318 .LP 319 The \fBhostent\fR structure does not change from the existing definition when 320 used with \fBgethostbyname\fR(3NSL). For example, host entries are represented 321 by the \fBstruct hostent\fR structure defined in <\fBnetdb.h\fR>: 322 .sp 323 .in +2 324 .nf 325 struct hostent { 326 char *h_name; /* canonical name of host */ 327 char **h_aliases; /* alias list */ 328 int h_addrtype; /* host address type */ 329 int h_length; /* length of address */ 330 char **h_addr_list; /* list of addresses */ 331 }; 332 .fi 333 .in -2 334 335 .sp 336 .LP 337 An error occurs when \fIname\fR is an IPv6 hex address and \fIaf\fR equals 338 \fBAF_INET\fR. The return value of the function is a \fINULL\fR pointer and 339 \fBerror_num\fR equals \fBHOST_NOT_FOUND\fR. 340 .sp 341 .LP 342 The \fBgetipnodebyaddr()\fR function has the same arguments as the existing 343 \fBgethostbyaddr\fR(3NSL) function, but adds an error number. As with 344 \fBgetipnodebyname()\fR, \fBgetipnodebyaddr()\fR is thread-safe. The 345 \fBerror_num\fR value is returned to the caller with the appropriate error code 346 to support thread-safe error code returns. The following error conditions can 347 be returned for \fBerror_num\fR: 348 .sp 349 .ne 2 350 .na 351 \fB\fBHOST_NOT_FOUND\fR\fR 352 .ad 353 .RS 18n 354 Host is unknown. 355 .RE 356 357 .sp 358 .ne 2 359 .na 360 \fB\fBNO_DATA\fR\fR 361 .ad 362 .RS 18n 363 No address is available for the \fIname\fR specified in the server request. 364 This error is not a soft error. Another type of \fIname\fR server request might 365 be successful. 366 .RE 367 368 .sp 369 .ne 2 370 .na 371 \fB\fBNO_RECOVERY\fR\fR 372 .ad 373 .RS 18n 374 An unexpected server failure occurred, which is a non-recoverable error. 375 .RE 376 377 .sp 378 .ne 2 379 .na 380 \fB\fBTRY_AGAIN\fR\fR 381 .ad 382 .RS 18n 383 This error is a soft error that indicates that the local server did not receive 384 a response from an authoritative server. A retry at some later time might be 385 successful. 386 .RE 387 388 .sp 389 .LP 390 One possible source of confusion is the handling of IPv4-mapped IPv6 addresses 391 and IPv4-compatible IPv6 addresses, but the following logic should apply: 392 .RS +4 393 .TP 394 1. 395 If \fIaf\fR is \fBAF_INET6\fR, and if \fIlen\fR equals 16, and if the IPv6 396 address is an IPv4-mapped IPv6 address or an IPv4-compatible IPv6 address, then 397 skip over the first 12 bytes of the IPv6 address, set \fIaf\fR to 398 \fBAF_INET\fR, and set \fIlen\fR to 4. 399 .RE 400 .RS +4 401 .TP 402 2. 403 If \fIaf\fR is \fBAF_INET\fR, lookup the \fIname\fR for the given IPv4 404 address. 405 .RE 406 .RS +4 407 .TP 408 3. 409 If \fIaf\fR is \fBAF_INET6\fR, lookup the \fIname\fR for the given IPv6 410 address. 411 .RE 412 .RS +4 413 .TP 414 4. 415 If the function is returning success, then the single address that is 416 returned in the \fBhostent\fR structure is a copy of the first argument to the 417 function with the same address family that was passed as an argument to this 418 function. 419 .RE 420 .sp 421 .LP 422 All four steps listed are performed in order. 423 .sp 424 .LP 425 This structure, and the information pointed to by this structure, are 426 dynamically allocated by \fBgetipnodebyname()\fR and \fBgetipnodebyaddr()\fR. 427 The \fBfreehostent()\fR function frees this memory. 428 .SH EXAMPLES 429 .LP 430 \fBExample 1 \fRGetting the Canonical Name, Aliases, and Internet IP Addresses 431 for a Given Hostname 432 .sp 433 .LP 434 The following is a sample program that retrieves the canonical name, aliases, 435 and all Internet IP addresses, both version 6 and version 4, for a given 436 hostname. 437 438 .sp 439 .in +2 440 .nf 441 #include <stdio.h> 442 #include <string.h> 443 #include <sys/types.h> 444 #include <sys/socket.h> 445 #include <netinet/in.h> 446 #include <arpa/inet.h> 447 #include <netdb.h> 448 449 main(int argc, const char **argv) 450 { 451 char abuf[INET6_ADDRSTRLEN]; 452 int error_num; 453 struct hostent *hp; 454 char **p; 455 456 if (argc != 2) { 457 (void) printf("usage: %s hostname\en", argv[0]); 458 exit (1); 459 } 460 461 /* argv[1] can be a pointer to a hostname or literal IP address */ 462 hp = getipnodebyname(argv[1], AF_INET6, AI_ALL | AI_ADDRCONFIG | 463 AI_V4MAPPED, &error_num); 464 if (hp == NULL) { 465 if (error_num == TRY_AGAIN) { 466 printf("%s: unknown host or invalid literal address " 467 "(try again later)\en", argv[1]); 468 } else { 469 printf("%s: unknown host or invalid literal address\en", 470 argv[1]); 471 } 472 exit (1); 473 } 474 for (p = hp->h_addr_list; *p != 0; p++) { 475 struct in6_addr in6; 476 char **q; 477 478 bcopy(*p, (caddr_t)&in6, hp->h_length); 479 (void) printf("%s\t%s", inet_ntop(AF_INET6, (void *)&in6, 480 abuf, sizeof(abuf)), hp->h_name); 481 for (q = hp->h_aliases; *q != 0; q++) 482 (void) printf(" %s", *q); 483 (void) putchar('\en'); 484 } 485 freehostent(hp); 486 exit (0); 487 } 488 .fi 489 .in -2 490 491 .SH ATTRIBUTES 492 .sp 493 .LP 494 See \fBattributes\fR(5) for descriptions of the following attributes: 495 .sp 496 497 .sp 498 .TS 499 box; 500 c | c 501 l | l . 502 ATTRIBUTE TYPE ATTRIBUTE VALUE 503 _ 504 Interface Stability Committed 505 _ 506 MT-Level Safe 507 .TE 508 509 .SH SEE ALSO 510 .sp 511 .LP 512 \fBgetaddrinfo\fR(3SOCKET), \fBgethostbyname\fR(3NSL), \fBhtonl\fR(3SOCKET), 513 \fBinet\fR(3SOCKET), \fBnetdb.h\fR(3HEAD), \fBhosts\fR(4), 514 \fBnsswitch.conf\fR(4), \fBattributes\fR(5) 515 .SH NOTES 516 .sp 517 .LP 518 No enumeration functions are provided for IPv6. Existing enumeration functions 519 such as \fBsethostent\fR(3NSL) do not work in combination with the 520 \fBgetipnodebyname()\fR and \fBgetipnodebyaddr()\fR functions. 521 .sp 522 .LP 523 All the functions that return a \fBstruct hostent\fR must always return the 524 canonical in the \fBh_name\fR field. This name, by definition, is the 525 well-known and official hostname shared between all aliases and all addresses. 526 The underlying source that satisfies the request determines the mapping of the 527 input name or address into the set of names and addresses in \fBhostent\fR. 528 Different sources might make such as determination in different ways. If more 529 than one alias and more than one address in \fBhostent\fR exist, no pairing is 530 implied between the alias and address. 531 .sp 532 .LP 533 The current implementations of these functions return or accept only addresses 534 for the Internet address family (type \fBAF_INET\fR) or the Internet address 535 family Version 6 (type \fBAF_INET6\fR). 536 .sp 537 .LP 538 IPv4-mapped addresses are not recommended. The \fBgetaddrinfo\fR(3SOCKET) 539 function is preferred over \fBgetipnodebyaddr()\fR because it allows 540 applications to lookup IPv4 and IPv6 addresses without relying on IPv4-mapped 541 addresses. 542 .sp 543 .LP 544 The form for an address of type \fBAF_INET\fR is a \fBstruct in_addr\fR defined 545 in <\fBnetinet/in.h\fR>. The form for an address of type \fBAF_INET6\fR is a 546 \fBstruct in6_addr\fR, also defined in <\fBnetinet/in.h\fR>. The functions 547 described in \fBinet_ntop\fR(3SOCKET) and \fBinet_pton\fR(3SOCKET) that are 548 illustrated in the EXAMPLES section are helpful in constructing and 549 manipulating addresses in either of these forms.