2 * Copyright (C) 2004, 2005, 2007 Internet Systems Consortium, Inc. ("ISC")
3 * Copyright (C) 2000, 2001 Internet Software Consortium.
5 * Permission to use, copy, modify, and/or distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
9 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
10 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
11 * AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
12 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
13 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
14 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
15 * PERFORMANCE OF THIS SOFTWARE.
18 /* $Id: gethost.c,v 1.34 2007/06/19 23:47:22 tbox Exp $ */
23 * These functions provide hostname-to-address and address-to-hostname
24 * lookups by means of the lightweight resolver. They are similar to the
25 * standard gethostent(3) functions provided by most operating systems.
26 * They use a struct hostent which is usually defined in <namedb.h>.
30 * char *h_name; // official name of host
31 * char **h_aliases; // alias list
32 * int h_addrtype; // host address type
33 * int h_length; // length of address
34 * char **h_addr_list; // list of addresses from name server
36 * #define h_addr h_addr_list[0] // address, for backward compatibility
39 * The members of this structure are:
42 * The official (canonical) name of the host.
45 * A NULL-terminated array of alternate names (nicknames) for the
49 * The type of address being returned -- PF_INET or PF_INET6.
52 * The length of the address in bytes.
55 * A NULL terminated array of network addresses for the host. Host
56 * addresses are returned in network byte order.
58 * For backward compatibility with very old software, h_addr is the first
59 * address in h_addr_list.
61 * lwres_gethostent(), lwres_sethostent(), lwres_endhostent(),
62 * lwres_gethostent_r(), lwres_sethostent_r() and lwres_endhostent_r()
63 * provide iteration over the known host entries on systems that provide
64 * such functionality through facilities like /etc/hosts or NIS. The
65 * lightweight resolver does not currently implement these functions; it
66 * only provides them as stub functions that always return failure.
68 * lwres_gethostbyname() and lwres_gethostbyname2() look up the hostname
69 * name. lwres_gethostbyname() always looks for an IPv4 address while
70 * lwres_gethostbyname2() looks for an address of protocol family af:
71 * either PF_INET or PF_INET6 -- IPv4 or IPV6 addresses respectively.
72 * Successful calls of the functions return a struct hostent for the name
73 * that was looked up. NULL is returned if the lookups by
74 * lwres_gethostbyname() or lwres_gethostbyname2() fail.
76 * Reverse lookups of addresses are performed by lwres_gethostbyaddr().
77 * addr is an address of length len bytes and protocol family type --
78 * PF_INET or PF_INET6. lwres_gethostbyname_r() is a thread-safe function
79 * for forward lookups. If an error occurs, an error code is returned in
80 * *error. resbuf is a pointer to a struct hostent which is initialised
81 * by a successful call to lwres_gethostbyname_r() . buf is a buffer of
82 * length len bytes which is used to store the h_name, h_aliases, and
83 * h_addr_list elements of the struct hostent returned in resbuf.
84 * Successful calls to lwres_gethostbyname_r() return resbuf, which is a
85 * pointer to the struct hostent it created.
87 * lwres_gethostbyaddr_r() is a thread-safe function that performs a
88 * reverse lookup of address addr which is len bytes long and is of
89 * protocol family type -- PF_INET or PF_INET6. If an error occurs, the
90 * error code is returned in *error. The other function parameters are
91 * identical to those in lwres_gethostbyname_r(). resbuf is a pointer to
92 * a struct hostent which is initialised by a successful call to
93 * lwres_gethostbyaddr_r(). buf is a buffer of length len bytes which is
94 * used to store the h_name, h_aliases, and h_addr_list elements of the
95 * struct hostent returned in resbuf. Successful calls to
96 * lwres_gethostbyaddr_r() return resbuf, which is a pointer to the
97 * struct hostent it created.
99 * \section gethost_return Return Values
101 * The functions lwres_gethostbyname(), lwres_gethostbyname2(),
102 * lwres_gethostbyaddr(), and lwres_gethostent() return NULL to indicate
103 * an error. In this case the global variable lwres_h_errno will contain
104 * one of the following error codes defined in \link netdb.h <lwres/netdb.h>:\endlink
106 * \li #HOST_NOT_FOUND:
107 * The host or address was not found.
110 * A recoverable error occurred, e.g., a timeout. Retrying the
111 * lookup may succeed.
114 * A non-recoverable error occurred.
117 * The name exists, but has no address information associated with
118 * it (or vice versa in the case of a reverse lookup). The code
119 * NO_ADDRESS is accepted as a synonym for NO_DATA for backwards
122 * lwres_hstrerror() translates these error codes to suitable error
125 * lwres_gethostent() and lwres_gethostent_r() always return NULL.
127 * Successful calls to lwres_gethostbyname_r() and
128 * lwres_gethostbyaddr_r() return resbuf, a pointer to the struct hostent
129 * that was initialised by these functions. They return NULL if the
130 * lookups fail or if buf was too small to hold the list of addresses and
131 * names referenced by the h_name, h_aliases, and h_addr_list elements of
132 * the struct hostent. If buf was too small, both lwres_gethostbyname_r()
133 * and lwres_gethostbyaddr_r() set the global variable errno to ERANGE.
135 * \section gethost_see See Also
137 * gethostent(), \link getipnode.c getipnode\endlink, lwres_hstrerror()
139 * \section gethost_bugs Bugs
141 * lwres_gethostbyname(), lwres_gethostbyname2(), lwres_gethostbyaddr()
142 * and lwres_endhostent() are not thread safe; they return pointers to
143 * static data and provide error codes through a global variable.
144 * Thread-safe versions for name and address lookup are provided by
145 * lwres_gethostbyname_r(), and lwres_gethostbyaddr_r() respectively.
147 * The resolver daemon does not currently support any non-DNS name
148 * services such as /etc/hosts or NIS, consequently the above functions
157 #include <lwres/net.h>
158 #include <lwres/netdb.h>
160 #include "assert_p.h"
162 #define LWRES_ALIGNBYTES (sizeof(char *) - 1)
163 #define LWRES_ALIGN(p) \
164 (((unsigned long)(p) + LWRES_ALIGNBYTES) &~ LWRES_ALIGNBYTES)
166 static struct hostent
*he
= NULL
;
167 static int copytobuf(struct hostent
*, struct hostent
*, char *, int);
169 /*% Always looks for an IPv4 address. */
171 lwres_gethostbyname(const char *name
) {
174 lwres_freehostent(he
);
176 he
= lwres_getipnodebyname(name
, AF_INET
, 0, &lwres_h_errno
);
180 /*% Looks for either an IPv4 or IPv6 address. */
182 lwres_gethostbyname2(const char *name
, int af
) {
184 lwres_freehostent(he
);
186 he
= lwres_getipnodebyname(name
, af
, 0, &lwres_h_errno
);
190 /*% Reverse lookup of addresses. */
192 lwres_gethostbyaddr(const char *addr
, int len
, int type
) {
195 lwres_freehostent(he
);
197 he
= lwres_getipnodebyaddr(addr
, len
, type
, &lwres_h_errno
);
201 /*% Stub function. Always returns failure. */
203 lwres_gethostent(void) {
205 lwres_freehostent(he
);
210 /*% Stub function. Always returns failure. */
212 lwres_sethostent(int stayopen
) {
219 /*% Stub function. Always returns failure. */
221 lwres_endhostent(void) {
227 /*% Thread-safe function for forward lookups. */
229 lwres_gethostbyname_r(const char *name
, struct hostent
*resbuf
,
230 char *buf
, int buflen
, int *error
)
235 he
= lwres_getipnodebyname(name
, AF_INET
, 0, error
);
238 res
= copytobuf(he
, resbuf
, buf
, buflen
);
239 lwres_freehostent(he
);
247 /*% Thread-safe reverse lookup. */
249 lwres_gethostbyaddr_r(const char *addr
, int len
, int type
,
250 struct hostent
*resbuf
, char *buf
, int buflen
,
256 he
= lwres_getipnodebyaddr(addr
, len
, type
, error
);
259 res
= copytobuf(he
, resbuf
, buf
, buflen
);
260 lwres_freehostent(he
);
268 /*% Stub function. Always returns failure. */
270 lwres_gethostent_r(struct hostent
*resbuf
, char *buf
, int buflen
, int *error
) {
278 /*% Stub function. Always returns failure. */
280 lwres_sethostent_r(int stayopen
) {
287 /*% Stub function. Always returns failure. */
289 lwres_endhostent_r(void) {
296 copytobuf(struct hostent
*he
, struct hostent
*hptr
, char *buf
, int buflen
) {
303 * Find out the amount of space required to store the answer.
305 nptr
= 2; /* NULL ptrs */
306 len
= (char *)LWRES_ALIGN(buf
) - buf
;
307 for (i
= 0; he
->h_addr_list
[i
]; i
++, nptr
++) {
310 for (i
= 0; he
->h_aliases
[i
]; i
++, nptr
++) {
311 len
+= strlen(he
->h_aliases
[i
]) + 1;
313 len
+= strlen(he
->h_name
) + 1;
314 len
+= nptr
* sizeof(char*);
321 * Copy address size and type.
323 hptr
->h_addrtype
= he
->h_addrtype
;
324 n
= hptr
->h_length
= he
->h_length
;
326 ptr
= (char **)LWRES_ALIGN(buf
);
327 cp
= (char *)LWRES_ALIGN(buf
) + nptr
* sizeof(char *);
332 hptr
->h_addr_list
= ptr
;
333 for (i
= 0; he
->h_addr_list
[i
]; i
++, ptr
++) {
334 memcpy(cp
, he
->h_addr_list
[i
], n
);
335 hptr
->h_addr_list
[i
] = cp
;
338 hptr
->h_addr_list
[i
] = NULL
;
342 * Copy official name.
344 n
= strlen(he
->h_name
) + 1;
345 strcpy(cp
, he
->h_name
);
352 hptr
->h_aliases
= ptr
;
353 for (i
= 0; he
->h_aliases
[i
]; i
++) {
354 n
= strlen(he
->h_aliases
[i
]) + 1;
355 strcpy(cp
, he
->h_aliases
[i
]);
356 hptr
->h_aliases
[i
] = cp
;
359 hptr
->h_aliases
[i
] = NULL
;