1/* Copyright (C) 2004-2021 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by Ulrich Drepper <drepper@redhat.com>, 2004.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <assert.h>
20#include <errno.h>
21#include <netdb.h>
22#include <stdlib.h>
23#include <string.h>
24#include <unistd.h>
25#include <not-cancel.h>
26
27#include "nscd-client.h"
28#include "nscd_proto.h"
29
30
31/* Define in nscd_gethst_r.c. */
32extern int __nss_not_use_nscd_hosts;
33
34
35/* We use the mapping from nscd_gethst. */
36libc_locked_map_ptr (extern, __hst_map_handle) attribute_hidden;
37
38/* Defined in nscd_gethst_r.c. */
39extern int __nss_have_localdomain attribute_hidden;
40
41
42int
43__nscd_getai (const char *key, struct nscd_ai_result **result, int *h_errnop)
44{
45 if (__glibc_unlikely (__nss_have_localdomain >= 0))
46 {
47 if (__nss_have_localdomain == 0)
48 __nss_have_localdomain = getenv ("LOCALDOMAIN") != NULL ? 1 : -1;
49 if (__nss_have_localdomain > 0)
50 {
51 __nss_not_use_nscd_hosts = 1;
52 return -1;
53 }
54 }
55
56 size_t keylen = strlen (key) + 1;
57 int gc_cycle;
58 int nretries = 0;
59
60 /* If the mapping is available, try to search there instead of
61 communicating with the nscd. */
62 struct mapped_database *mapped;
63 mapped = __nscd_get_map_ref (GETFDHST, "hosts", &__hst_map_handle,
64 &gc_cycle);
65
66 retry:;
67 struct nscd_ai_result *resultbuf = NULL;
68 const char *recend = (const char *) ~UINTMAX_C (0);
69 char *respdata = NULL;
70 int retval = -1;
71 int sock = -1;
72 ai_response_header ai_resp;
73
74 if (mapped != NO_MAPPING)
75 {
76 struct datahead *found = __nscd_cache_search (GETAI, key, keylen,
77 mapped, sizeof ai_resp);
78 if (found != NULL)
79 {
80 respdata = (char *) (&found->data[0].aidata + 1);
81 ai_resp = found->data[0].aidata;
82 recend = (const char *) found->data + found->recsize;
83 /* Now check if we can trust ai_resp fields. If GC is
84 in progress, it can contain anything. */
85 if (mapped->head->gc_cycle != gc_cycle)
86 {
87 retval = -2;
88 goto out;
89 }
90 }
91 }
92
93 /* If we do not have the cache mapped, try to get the data over the
94 socket. */
95 if (respdata == NULL)
96 {
97 sock = __nscd_open_socket (key, keylen, GETAI, &ai_resp,
98 sizeof (ai_resp));
99 if (sock == -1)
100 {
101 /* nscd not running or wrong version. */
102 __nss_not_use_nscd_hosts = 1;
103 goto out;
104 }
105 }
106
107 if (ai_resp.found == 1)
108 {
109 size_t datalen = ai_resp.naddrs + ai_resp.addrslen + ai_resp.canonlen;
110
111 /* This check really only affects the case where the data
112 comes from the mapped cache. */
113 if (respdata + datalen > recend)
114 {
115 assert (sock == -1);
116 goto out;
117 }
118
119 /* Create result. */
120 resultbuf = (struct nscd_ai_result *) malloc (sizeof (*resultbuf)
121 + datalen);
122 if (resultbuf == NULL)
123 {
124 *h_errnop = NETDB_INTERNAL;
125 goto out_close;
126 }
127
128 /* Set up the data structure, including pointers. */
129 resultbuf->naddrs = ai_resp.naddrs;
130 resultbuf->addrs = (char *) (resultbuf + 1);
131 resultbuf->family = (uint8_t *) (resultbuf->addrs + ai_resp.addrslen);
132 if (ai_resp.canonlen != 0)
133 resultbuf->canon = (char *) (resultbuf->family + resultbuf->naddrs);
134 else
135 resultbuf->canon = NULL;
136
137 if (respdata == NULL)
138 {
139 /* Read the data from the socket. */
140 if ((size_t) __readall (sock, resultbuf + 1, datalen) == datalen)
141 {
142 retval = 0;
143 *result = resultbuf;
144 }
145 else
146 {
147 free (resultbuf);
148 *h_errnop = NETDB_INTERNAL;
149 }
150 }
151 else
152 {
153 /* Copy the data in the block. */
154 memcpy (resultbuf + 1, respdata, datalen);
155
156 /* Try to detect corrupt databases. */
157 if (resultbuf->canon != NULL
158 && resultbuf->canon[ai_resp.canonlen - 1] != '\0')
159 /* We cannot use the database. */
160 {
161 if (mapped->head->gc_cycle != gc_cycle)
162 retval = -2;
163 else
164 free (resultbuf);
165 goto out_close;
166 }
167
168 retval = 0;
169 *result = resultbuf;
170 }
171 }
172 else
173 {
174 if (__glibc_unlikely (ai_resp.found == -1))
175 {
176 /* The daemon does not cache this database. */
177 __nss_not_use_nscd_hosts = 1;
178 goto out_close;
179 }
180
181 /* Store the error number. */
182 *h_errnop = ai_resp.error;
183
184 /* Set errno to 0 to indicate no error, just no found record. */
185 __set_errno (0);
186 /* Even though we have not found anything, the result is zero. */
187 retval = 0;
188 }
189
190 out_close:
191 if (sock != -1)
192 __close_nocancel_nostatus (sock);
193 out:
194 if (__nscd_drop_map_ref (mapped, &gc_cycle) != 0)
195 {
196 /* When we come here this means there has been a GC cycle while we
197 were looking for the data. This means the data might have been
198 inconsistent. Retry if possible. */
199 if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
200 {
201 /* nscd is just running gc now. Disable using the mapping. */
202 if (atomic_decrement_val (&mapped->counter) == 0)
203 __nscd_unmap (mapped);
204 mapped = NO_MAPPING;
205 }
206
207 if (retval != -1)
208 {
209 *result = NULL;
210 free (resultbuf);
211 goto retry;
212 }
213 }
214
215 return retval;
216}
217