/* * Copyright (C) 2004, 2005, 2007 Internet Systems Consortium, Inc. ("ISC") * Copyright (C) 2000, 2001 Internet Software Consortium. * * Permission to use, copy, modify, and/or distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY * AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR * PERFORMANCE OF THIS SOFTWARE. */ /* $Id: gethost.c,v 1.34 2007/06/19 23:47:22 tbox Exp $ */ /*! \file */ /** * These functions provide hostname-to-address and address-to-hostname * lookups by means of the lightweight resolver. They are similar to the * standard gethostent(3) functions provided by most operating systems. * They use a struct hostent which is usually defined in <namedb.h>. * * \code * struct hostent { * char *h_name; // official name of host * char **h_aliases; // alias list * int h_addrtype; // host address type * int h_length; // length of address * char **h_addr_list; // list of addresses from name server * }; * #define h_addr h_addr_list[0] // address, for backward compatibility * \endcode * * The members of this structure are: * * \li h_name: * The official (canonical) name of the host. * * \li h_aliases: * A NULL-terminated array of alternate names (nicknames) for the * host. * * \li h_addrtype: * The type of address being returned -- PF_INET or PF_INET6. * * \li h_length: * The length of the address in bytes. * * \li h_addr_list: * A NULL terminated array of network addresses for the host. Host * addresses are returned in network byte order. * * For backward compatibility with very old software, h_addr is the first * address in h_addr_list. * * lwres_gethostent(), lwres_sethostent(), lwres_endhostent(), * lwres_gethostent_r(), lwres_sethostent_r() and lwres_endhostent_r() * provide iteration over the known host entries on systems that provide * such functionality through facilities like /etc/hosts or NIS. The * lightweight resolver does not currently implement these functions; it * only provides them as stub functions that always return failure. * * lwres_gethostbyname() and lwres_gethostbyname2() look up the hostname * name. lwres_gethostbyname() always looks for an IPv4 address while * lwres_gethostbyname2() looks for an address of protocol family af: * either PF_INET or PF_INET6 -- IPv4 or IPV6 addresses respectively. * Successful calls of the functions return a struct hostent for the name * that was looked up. NULL is returned if the lookups by * lwres_gethostbyname() or lwres_gethostbyname2() fail. * * Reverse lookups of addresses are performed by lwres_gethostbyaddr(). * addr is an address of length len bytes and protocol family type -- * PF_INET or PF_INET6. lwres_gethostbyname_r() is a thread-safe function * for forward lookups. If an error occurs, an error code is returned in * *error. resbuf is a pointer to a struct hostent which is initialised * by a successful call to lwres_gethostbyname_r() . buf is a buffer of * length len bytes which is used to store the h_name, h_aliases, and * h_addr_list elements of the struct hostent returned in resbuf. * Successful calls to lwres_gethostbyname_r() return resbuf, which is a * pointer to the struct hostent it created. * * lwres_gethostbyaddr_r() is a thread-safe function that performs a * reverse lookup of address addr which is len bytes long and is of * protocol family type -- PF_INET or PF_INET6. If an error occurs, the * error code is returned in *error. The other function parameters are * identical to those in lwres_gethostbyname_r(). resbuf is a pointer to * a struct hostent which is initialised by a successful call to * lwres_gethostbyaddr_r(). buf is a buffer of length len bytes which is * used to store the h_name, h_aliases, and h_addr_list elements of the * struct hostent returned in resbuf. Successful calls to * lwres_gethostbyaddr_r() return resbuf, which is a pointer to the * struct hostent it created. * * \section gethost_return Return Values * * The functions lwres_gethostbyname(), lwres_gethostbyname2(), * lwres_gethostbyaddr(), and lwres_gethostent() return NULL to indicate * an error. In this case the global variable lwres_h_errno will contain * one of the following error codes defined in \link netdb.h <lwres/netdb.h>:\endlink * * \li #HOST_NOT_FOUND: * The host or address was not found. * * \li #TRY_AGAIN: * A recoverable error occurred, e.g., a timeout. Retrying the * lookup may succeed. * * \li #NO_RECOVERY: * A non-recoverable error occurred. * * \li #NO_DATA: * The name exists, but has no address information associated with * it (or vice versa in the case of a reverse lookup). The code * NO_ADDRESS is accepted as a synonym for NO_DATA for backwards * compatibility. * * lwres_hstrerror() translates these error codes to suitable error * messages. * * lwres_gethostent() and lwres_gethostent_r() always return NULL. * * Successful calls to lwres_gethostbyname_r() and * lwres_gethostbyaddr_r() return resbuf, a pointer to the struct hostent * that was initialised by these functions. They return NULL if the * lookups fail or if buf was too small to hold the list of addresses and * names referenced by the h_name, h_aliases, and h_addr_list elements of * the struct hostent. If buf was too small, both lwres_gethostbyname_r() * and lwres_gethostbyaddr_r() set the global variable errno to ERANGE. * * \section gethost_see See Also * * gethostent(), \link getipnode.c getipnode\endlink, lwres_hstrerror() * * \section gethost_bugs Bugs * * lwres_gethostbyname(), lwres_gethostbyname2(), lwres_gethostbyaddr() * and lwres_endhostent() are not thread safe; they return pointers to * static data and provide error codes through a global variable. * Thread-safe versions for name and address lookup are provided by * lwres_gethostbyname_r(), and lwres_gethostbyaddr_r() respectively. * * The resolver daemon does not currently support any non-DNS name * services such as /etc/hosts or NIS, consequently the above functions * don't, either. */ #include <config.h> #include <errno.h> #include <string.h> #include <lwres/net.h> #include <lwres/netdb.h> #include "assert_p.h" #define LWRES_ALIGNBYTES (sizeof(char *) - 1) #define LWRES_ALIGN(p) \ (((unsigned long)(p) + LWRES_ALIGNBYTES) &~ LWRES_ALIGNBYTES) static struct hostent *he = NULL; static int copytobuf(struct hostent *, struct hostent *, char *, int); /*% Always looks for an IPv4 address. */ struct hostent * lwres_gethostbyname(const char *name) { if (he != NULL) lwres_freehostent(he); he = lwres_getipnodebyname(name, AF_INET, 0, &lwres_h_errno); return (he); } /*% Looks for either an IPv4 or IPv6 address. */ struct hostent * lwres_gethostbyname2(const char *name, int af) { if (he != NULL) lwres_freehostent(he); he = lwres_getipnodebyname(name, af, 0, &lwres_h_errno); return (he); } /*% Reverse lookup of addresses. */ struct hostent * lwres_gethostbyaddr(const char *addr, int len, int type) { if (he != NULL) lwres_freehostent(he); he = lwres_getipnodebyaddr(addr, len, type, &lwres_h_errno); return (he); } /*% Stub function. Always returns failure. */ struct hostent * lwres_gethostent(void) { if (he != NULL) lwres_freehostent(he); return (NULL); } /*% Stub function. Always returns failure. */ void lwres_sethostent(int stayopen) { /* * Empty. */ UNUSED(stayopen); } /*% Stub function. Always returns failure. */ void lwres_endhostent(void) { /* * Empty. */ } /*% Thread-safe function for forward lookups. */ struct hostent * lwres_gethostbyname_r(const char *name, struct hostent *resbuf, char *buf, int buflen, int *error) { struct hostent *he; int res; he = lwres_getipnodebyname(name, AF_INET, 0, error); if (he == NULL) return (NULL); res = copytobuf(he, resbuf, buf, buflen); lwres_freehostent(he); if (res != 0) { errno = ERANGE; return (NULL); } return (resbuf); } /*% Thread-safe reverse lookup. */ struct hostent * lwres_gethostbyaddr_r(const char *addr, int len, int type, struct hostent *resbuf, char *buf, int buflen, int *error) { struct hostent *he; int res; he = lwres_getipnodebyaddr(addr, len, type, error); if (he == NULL) return (NULL); res = copytobuf(he, resbuf, buf, buflen); lwres_freehostent(he); if (res != 0) { errno = ERANGE; return (NULL); } return (resbuf); } /*% Stub function. Always returns failure. */ struct hostent * lwres_gethostent_r(struct hostent *resbuf, char *buf, int buflen, int *error) { UNUSED(resbuf); UNUSED(buf); UNUSED(buflen); *error = 0; return (NULL); } /*% Stub function. Always returns failure. */ void lwres_sethostent_r(int stayopen) { /* * Empty. */ UNUSED(stayopen); } /*% Stub function. Always returns failure. */ void lwres_endhostent_r(void) { /* * Empty. */ } static int copytobuf(struct hostent *he, struct hostent *hptr, char *buf, int buflen) { char *cp; char **ptr; int i, n; int nptr, len; /* * Find out the amount of space required to store the answer. */ nptr = 2; /* NULL ptrs */ len = (char *)LWRES_ALIGN(buf) - buf; for (i = 0; he->h_addr_list[i]; i++, nptr++) { len += he->h_length; } for (i = 0; he->h_aliases[i]; i++, nptr++) { len += strlen(he->h_aliases[i]) + 1; } len += strlen(he->h_name) + 1; len += nptr * sizeof(char*); if (len > buflen) { return (-1); } /* * Copy address size and type. */ hptr->h_addrtype = he->h_addrtype; n = hptr->h_length = he->h_length; ptr = (char **)LWRES_ALIGN(buf); cp = (char *)LWRES_ALIGN(buf) + nptr * sizeof(char *); /* * Copy address list. */ hptr->h_addr_list = ptr; for (i = 0; he->h_addr_list[i]; i++, ptr++) { memcpy(cp, he->h_addr_list[i], n); hptr->h_addr_list[i] = cp; cp += n; } hptr->h_addr_list[i] = NULL; ptr++; /* * Copy official name. */ n = strlen(he->h_name) + 1; strcpy(cp, he->h_name); hptr->h_name = cp; cp += n; /* * Copy aliases. */ hptr->h_aliases = ptr; for (i = 0; he->h_aliases[i]; i++) { n = strlen(he->h_aliases[i]) + 1; strcpy(cp, he->h_aliases[i]); hptr->h_aliases[i] = cp; cp += n; } hptr->h_aliases[i] = NULL; return (0); }