gethost.c revision 193149
1135446Strhodes/* 2193149Sdougb * Copyright (C) 2004, 2005, 2007 Internet Systems Consortium, Inc. ("ISC") 3135446Strhodes * Copyright (C) 2000, 2001 Internet Software Consortium. 4135446Strhodes * 5193149Sdougb * Permission to use, copy, modify, and/or distribute this software for any 6135446Strhodes * purpose with or without fee is hereby granted, provided that the above 7135446Strhodes * copyright notice and this permission notice appear in all copies. 8135446Strhodes * 9135446Strhodes * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH 10135446Strhodes * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY 11135446Strhodes * AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, 12135446Strhodes * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM 13135446Strhodes * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE 14135446Strhodes * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR 15135446Strhodes * PERFORMANCE OF THIS SOFTWARE. 16135446Strhodes */ 17135446Strhodes 18193149Sdougb/* $Id: gethost.c,v 1.34 2007/06/19 23:47:22 tbox Exp $ */ 19135446Strhodes 20170222Sdougb/*! \file */ 21170222Sdougb 22170222Sdougb/** 23170222Sdougb * These functions provide hostname-to-address and address-to-hostname 24170222Sdougb * lookups by means of the lightweight resolver. They are similar to the 25170222Sdougb * standard gethostent(3) functions provided by most operating systems. 26170222Sdougb * They use a struct hostent which is usually defined in <namedb.h>. 27170222Sdougb * 28170222Sdougb * \code 29170222Sdougb * struct hostent { 30170222Sdougb * char *h_name; // official name of host 31170222Sdougb * char **h_aliases; // alias list 32170222Sdougb * int h_addrtype; // host address type 33170222Sdougb * int h_length; // length of address 34170222Sdougb * char **h_addr_list; // list of addresses from name server 35170222Sdougb * }; 36170222Sdougb * #define h_addr h_addr_list[0] // address, for backward compatibility 37170222Sdougb * \endcode 38170222Sdougb * 39170222Sdougb * The members of this structure are: 40170222Sdougb * 41170222Sdougb * \li h_name: 42170222Sdougb * The official (canonical) name of the host. 43170222Sdougb * 44170222Sdougb * \li h_aliases: 45170222Sdougb * A NULL-terminated array of alternate names (nicknames) for the 46170222Sdougb * host. 47170222Sdougb * 48170222Sdougb * \li h_addrtype: 49170222Sdougb * The type of address being returned -- PF_INET or PF_INET6. 50170222Sdougb * 51170222Sdougb * \li h_length: 52170222Sdougb * The length of the address in bytes. 53170222Sdougb * 54170222Sdougb * \li h_addr_list: 55170222Sdougb * A NULL terminated array of network addresses for the host. Host 56170222Sdougb * addresses are returned in network byte order. 57170222Sdougb * 58170222Sdougb * For backward compatibility with very old software, h_addr is the first 59170222Sdougb * address in h_addr_list. 60170222Sdougb * 61170222Sdougb * lwres_gethostent(), lwres_sethostent(), lwres_endhostent(), 62170222Sdougb * lwres_gethostent_r(), lwres_sethostent_r() and lwres_endhostent_r() 63170222Sdougb * provide iteration over the known host entries on systems that provide 64170222Sdougb * such functionality through facilities like /etc/hosts or NIS. The 65170222Sdougb * lightweight resolver does not currently implement these functions; it 66170222Sdougb * only provides them as stub functions that always return failure. 67170222Sdougb * 68170222Sdougb * lwres_gethostbyname() and lwres_gethostbyname2() look up the hostname 69170222Sdougb * name. lwres_gethostbyname() always looks for an IPv4 address while 70170222Sdougb * lwres_gethostbyname2() looks for an address of protocol family af: 71170222Sdougb * either PF_INET or PF_INET6 -- IPv4 or IPV6 addresses respectively. 72170222Sdougb * Successful calls of the functions return a struct hostent for the name 73170222Sdougb * that was looked up. NULL is returned if the lookups by 74170222Sdougb * lwres_gethostbyname() or lwres_gethostbyname2() fail. 75170222Sdougb * 76170222Sdougb * Reverse lookups of addresses are performed by lwres_gethostbyaddr(). 77170222Sdougb * addr is an address of length len bytes and protocol family type -- 78170222Sdougb * PF_INET or PF_INET6. lwres_gethostbyname_r() is a thread-safe function 79170222Sdougb * for forward lookups. If an error occurs, an error code is returned in 80170222Sdougb * *error. resbuf is a pointer to a struct hostent which is initialised 81170222Sdougb * by a successful call to lwres_gethostbyname_r() . buf is a buffer of 82170222Sdougb * length len bytes which is used to store the h_name, h_aliases, and 83170222Sdougb * h_addr_list elements of the struct hostent returned in resbuf. 84170222Sdougb * Successful calls to lwres_gethostbyname_r() return resbuf, which is a 85170222Sdougb * pointer to the struct hostent it created. 86170222Sdougb * 87170222Sdougb * lwres_gethostbyaddr_r() is a thread-safe function that performs a 88170222Sdougb * reverse lookup of address addr which is len bytes long and is of 89170222Sdougb * protocol family type -- PF_INET or PF_INET6. If an error occurs, the 90170222Sdougb * error code is returned in *error. The other function parameters are 91170222Sdougb * identical to those in lwres_gethostbyname_r(). resbuf is a pointer to 92170222Sdougb * a struct hostent which is initialised by a successful call to 93170222Sdougb * lwres_gethostbyaddr_r(). buf is a buffer of length len bytes which is 94170222Sdougb * used to store the h_name, h_aliases, and h_addr_list elements of the 95170222Sdougb * struct hostent returned in resbuf. Successful calls to 96170222Sdougb * lwres_gethostbyaddr_r() return resbuf, which is a pointer to the 97170222Sdougb * struct hostent it created. 98170222Sdougb * 99170222Sdougb * \section gethost_return Return Values 100170222Sdougb * 101170222Sdougb * The functions lwres_gethostbyname(), lwres_gethostbyname2(), 102170222Sdougb * lwres_gethostbyaddr(), and lwres_gethostent() return NULL to indicate 103170222Sdougb * an error. In this case the global variable lwres_h_errno will contain 104170222Sdougb * one of the following error codes defined in \link netdb.h <lwres/netdb.h>:\endlink 105170222Sdougb * 106170222Sdougb * \li #HOST_NOT_FOUND: 107170222Sdougb * The host or address was not found. 108170222Sdougb * 109170222Sdougb * \li #TRY_AGAIN: 110170222Sdougb * A recoverable error occurred, e.g., a timeout. Retrying the 111170222Sdougb * lookup may succeed. 112170222Sdougb * 113170222Sdougb * \li #NO_RECOVERY: 114170222Sdougb * A non-recoverable error occurred. 115170222Sdougb * 116170222Sdougb * \li #NO_DATA: 117170222Sdougb * The name exists, but has no address information associated with 118170222Sdougb * it (or vice versa in the case of a reverse lookup). The code 119170222Sdougb * NO_ADDRESS is accepted as a synonym for NO_DATA for backwards 120170222Sdougb * compatibility. 121170222Sdougb * 122170222Sdougb * lwres_hstrerror() translates these error codes to suitable error 123170222Sdougb * messages. 124170222Sdougb * 125170222Sdougb * lwres_gethostent() and lwres_gethostent_r() always return NULL. 126170222Sdougb * 127170222Sdougb * Successful calls to lwres_gethostbyname_r() and 128170222Sdougb * lwres_gethostbyaddr_r() return resbuf, a pointer to the struct hostent 129170222Sdougb * that was initialised by these functions. They return NULL if the 130170222Sdougb * lookups fail or if buf was too small to hold the list of addresses and 131170222Sdougb * names referenced by the h_name, h_aliases, and h_addr_list elements of 132170222Sdougb * the struct hostent. If buf was too small, both lwres_gethostbyname_r() 133170222Sdougb * and lwres_gethostbyaddr_r() set the global variable errno to ERANGE. 134170222Sdougb * 135170222Sdougb * \section gethost_see See Also 136170222Sdougb * 137170222Sdougb * gethostent(), \link getipnode.c getipnode\endlink, lwres_hstrerror() 138170222Sdougb * 139170222Sdougb * \section gethost_bugs Bugs 140170222Sdougb * 141170222Sdougb * lwres_gethostbyname(), lwres_gethostbyname2(), lwres_gethostbyaddr() 142170222Sdougb * and lwres_endhostent() are not thread safe; they return pointers to 143170222Sdougb * static data and provide error codes through a global variable. 144170222Sdougb * Thread-safe versions for name and address lookup are provided by 145170222Sdougb * lwres_gethostbyname_r(), and lwres_gethostbyaddr_r() respectively. 146170222Sdougb * 147170222Sdougb * The resolver daemon does not currently support any non-DNS name 148170222Sdougb * services such as /etc/hosts or NIS, consequently the above functions 149170222Sdougb * don't, either. 150170222Sdougb */ 151170222Sdougb 152135446Strhodes#include <config.h> 153135446Strhodes 154135446Strhodes#include <errno.h> 155135446Strhodes#include <string.h> 156135446Strhodes 157135446Strhodes#include <lwres/net.h> 158135446Strhodes#include <lwres/netdb.h> 159135446Strhodes 160135446Strhodes#include "assert_p.h" 161135446Strhodes 162135446Strhodes#define LWRES_ALIGNBYTES (sizeof(char *) - 1) 163135446Strhodes#define LWRES_ALIGN(p) \ 164135446Strhodes (((unsigned long)(p) + LWRES_ALIGNBYTES) &~ LWRES_ALIGNBYTES) 165135446Strhodes 166135446Strhodesstatic struct hostent *he = NULL; 167135446Strhodesstatic int copytobuf(struct hostent *, struct hostent *, char *, int); 168135446Strhodes 169170222Sdougb/*% Always looks for an IPv4 address. */ 170135446Strhodesstruct hostent * 171135446Strhodeslwres_gethostbyname(const char *name) { 172135446Strhodes 173135446Strhodes if (he != NULL) 174135446Strhodes lwres_freehostent(he); 175135446Strhodes 176135446Strhodes he = lwres_getipnodebyname(name, AF_INET, 0, &lwres_h_errno); 177135446Strhodes return (he); 178135446Strhodes} 179135446Strhodes 180170222Sdougb/*% Looks for either an IPv4 or IPv6 address. */ 181135446Strhodesstruct hostent * 182135446Strhodeslwres_gethostbyname2(const char *name, int af) { 183135446Strhodes if (he != NULL) 184135446Strhodes lwres_freehostent(he); 185135446Strhodes 186135446Strhodes he = lwres_getipnodebyname(name, af, 0, &lwres_h_errno); 187135446Strhodes return (he); 188135446Strhodes} 189135446Strhodes 190170222Sdougb/*% Reverse lookup of addresses. */ 191135446Strhodesstruct hostent * 192135446Strhodeslwres_gethostbyaddr(const char *addr, int len, int type) { 193135446Strhodes 194135446Strhodes if (he != NULL) 195135446Strhodes lwres_freehostent(he); 196135446Strhodes 197135446Strhodes he = lwres_getipnodebyaddr(addr, len, type, &lwres_h_errno); 198135446Strhodes return (he); 199135446Strhodes} 200135446Strhodes 201170222Sdougb/*% Stub function. Always returns failure. */ 202135446Strhodesstruct hostent * 203135446Strhodeslwres_gethostent(void) { 204135446Strhodes if (he != NULL) 205135446Strhodes lwres_freehostent(he); 206135446Strhodes 207135446Strhodes return (NULL); 208135446Strhodes} 209135446Strhodes 210170222Sdougb/*% Stub function. Always returns failure. */ 211135446Strhodesvoid 212135446Strhodeslwres_sethostent(int stayopen) { 213135446Strhodes /* 214135446Strhodes * Empty. 215135446Strhodes */ 216135446Strhodes UNUSED(stayopen); 217135446Strhodes} 218135446Strhodes 219170222Sdougb/*% Stub function. Always returns failure. */ 220135446Strhodesvoid 221135446Strhodeslwres_endhostent(void) { 222135446Strhodes /* 223135446Strhodes * Empty. 224135446Strhodes */ 225135446Strhodes} 226135446Strhodes 227170222Sdougb/*% Thread-safe function for forward lookups. */ 228135446Strhodesstruct hostent * 229135446Strhodeslwres_gethostbyname_r(const char *name, struct hostent *resbuf, 230135446Strhodes char *buf, int buflen, int *error) 231135446Strhodes{ 232135446Strhodes struct hostent *he; 233135446Strhodes int res; 234135446Strhodes 235135446Strhodes he = lwres_getipnodebyname(name, AF_INET, 0, error); 236135446Strhodes if (he == NULL) 237135446Strhodes return (NULL); 238135446Strhodes res = copytobuf(he, resbuf, buf, buflen); 239135446Strhodes lwres_freehostent(he); 240135446Strhodes if (res != 0) { 241135446Strhodes errno = ERANGE; 242135446Strhodes return (NULL); 243135446Strhodes } 244135446Strhodes return (resbuf); 245135446Strhodes} 246135446Strhodes 247170222Sdougb/*% Thread-safe reverse lookup. */ 248135446Strhodesstruct hostent * 249135446Strhodeslwres_gethostbyaddr_r(const char *addr, int len, int type, 250135446Strhodes struct hostent *resbuf, char *buf, int buflen, 251135446Strhodes int *error) 252135446Strhodes{ 253135446Strhodes struct hostent *he; 254135446Strhodes int res; 255135446Strhodes 256135446Strhodes he = lwres_getipnodebyaddr(addr, len, type, error); 257135446Strhodes if (he == NULL) 258135446Strhodes return (NULL); 259135446Strhodes res = copytobuf(he, resbuf, buf, buflen); 260135446Strhodes lwres_freehostent(he); 261135446Strhodes if (res != 0) { 262135446Strhodes errno = ERANGE; 263135446Strhodes return (NULL); 264135446Strhodes } 265135446Strhodes return (resbuf); 266135446Strhodes} 267135446Strhodes 268170222Sdougb/*% Stub function. Always returns failure. */ 269135446Strhodesstruct hostent * 270135446Strhodeslwres_gethostent_r(struct hostent *resbuf, char *buf, int buflen, int *error) { 271135446Strhodes UNUSED(resbuf); 272135446Strhodes UNUSED(buf); 273135446Strhodes UNUSED(buflen); 274135446Strhodes *error = 0; 275135446Strhodes return (NULL); 276135446Strhodes} 277135446Strhodes 278170222Sdougb/*% Stub function. Always returns failure. */ 279135446Strhodesvoid 280135446Strhodeslwres_sethostent_r(int stayopen) { 281135446Strhodes /* 282135446Strhodes * Empty. 283135446Strhodes */ 284135446Strhodes UNUSED(stayopen); 285135446Strhodes} 286135446Strhodes 287170222Sdougb/*% Stub function. Always returns failure. */ 288135446Strhodesvoid 289135446Strhodeslwres_endhostent_r(void) { 290135446Strhodes /* 291135446Strhodes * Empty. 292135446Strhodes */ 293135446Strhodes} 294135446Strhodes 295135446Strhodesstatic int 296135446Strhodescopytobuf(struct hostent *he, struct hostent *hptr, char *buf, int buflen) { 297135446Strhodes char *cp; 298135446Strhodes char **ptr; 299135446Strhodes int i, n; 300135446Strhodes int nptr, len; 301135446Strhodes 302135446Strhodes /* 303135446Strhodes * Find out the amount of space required to store the answer. 304135446Strhodes */ 305135446Strhodes nptr = 2; /* NULL ptrs */ 306135446Strhodes len = (char *)LWRES_ALIGN(buf) - buf; 307135446Strhodes for (i = 0; he->h_addr_list[i]; i++, nptr++) { 308135446Strhodes len += he->h_length; 309135446Strhodes } 310135446Strhodes for (i = 0; he->h_aliases[i]; i++, nptr++) { 311135446Strhodes len += strlen(he->h_aliases[i]) + 1; 312135446Strhodes } 313135446Strhodes len += strlen(he->h_name) + 1; 314135446Strhodes len += nptr * sizeof(char*); 315135446Strhodes 316135446Strhodes if (len > buflen) { 317135446Strhodes return (-1); 318135446Strhodes } 319135446Strhodes 320135446Strhodes /* 321135446Strhodes * Copy address size and type. 322135446Strhodes */ 323135446Strhodes hptr->h_addrtype = he->h_addrtype; 324135446Strhodes n = hptr->h_length = he->h_length; 325135446Strhodes 326135446Strhodes ptr = (char **)LWRES_ALIGN(buf); 327135446Strhodes cp = (char *)LWRES_ALIGN(buf) + nptr * sizeof(char *); 328135446Strhodes 329135446Strhodes /* 330135446Strhodes * Copy address list. 331135446Strhodes */ 332135446Strhodes hptr->h_addr_list = ptr; 333135446Strhodes for (i = 0; he->h_addr_list[i]; i++, ptr++) { 334135446Strhodes memcpy(cp, he->h_addr_list[i], n); 335135446Strhodes hptr->h_addr_list[i] = cp; 336135446Strhodes cp += n; 337135446Strhodes } 338135446Strhodes hptr->h_addr_list[i] = NULL; 339135446Strhodes ptr++; 340135446Strhodes 341135446Strhodes /* 342135446Strhodes * Copy official name. 343135446Strhodes */ 344135446Strhodes n = strlen(he->h_name) + 1; 345135446Strhodes strcpy(cp, he->h_name); 346135446Strhodes hptr->h_name = cp; 347135446Strhodes cp += n; 348135446Strhodes 349135446Strhodes /* 350135446Strhodes * Copy aliases. 351135446Strhodes */ 352135446Strhodes hptr->h_aliases = ptr; 353135446Strhodes for (i = 0; he->h_aliases[i]; i++) { 354135446Strhodes n = strlen(he->h_aliases[i]) + 1; 355135446Strhodes strcpy(cp, he->h_aliases[i]); 356135446Strhodes hptr->h_aliases[i] = cp; 357135446Strhodes cp += n; 358135446Strhodes } 359135446Strhodes hptr->h_aliases[i] = NULL; 360135446Strhodes 361135446Strhodes return (0); 362135446Strhodes} 363