source: vendor/3.5.0/source3/nmbd/asyncdns.c

Last change on this file was 414, checked in by Herwig Bauernfeind, 15 years ago

Samba 3.5.0: Initial import
File size: 9.3 KB
Line 
1/*
2 Unix SMB/CIFS implementation.
3 a async DNS handler
4 Copyright (C) Andrew Tridgell 1997-1998
5
6 This program is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3 of the License, or
9 (at your option) any later version.
10
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
18 */
19
20#include "includes.h"
21
22/***************************************************************************
23 Add a DNS result to the name cache.
24****************************************************************************/
25
26static struct name_record *add_dns_result(struct nmb_name *question, struct in_addr addr)
27{
28 int name_type = question->name_type;
29 unstring qname;
30
31 pull_ascii_nstring(qname, sizeof(qname), question->name);
32
33 if (!addr.s_addr) {
34 /* add the fail to WINS cache of names. give it 1 hour in the cache */
35 DEBUG(3,("add_dns_result: Negative DNS answer for %s\n", qname));
36 add_name_to_subnet( wins_server_subnet, qname, name_type,
37 NB_ACTIVE, 60*60, DNSFAIL_NAME, 1, &addr );
38 return NULL;
39 }
40
41 /* add it to our WINS cache of names. give it 2 hours in the cache */
42 DEBUG(3,("add_dns_result: DNS gave answer for %s of %s\n", qname, inet_ntoa(addr)));
43
44 add_name_to_subnet( wins_server_subnet, qname, name_type,
45 NB_ACTIVE, 2*60*60, DNS_NAME, 1, &addr);
46
47 return find_name_on_subnet(wins_server_subnet, question, FIND_ANY_NAME);
48}
49
50#ifndef SYNC_DNS
51
52static int fd_in = -1, fd_out = -1;
53static pid_t child_pid = -1;
54static int in_dns;
55
56/* this is the structure that is passed between the parent and child */
57struct query_record {
58 struct nmb_name name;
59 struct in_addr result;
60};
61
62/* a queue of pending requests waiting to be sent to the DNS child */
63static struct packet_struct *dns_queue;
64
65/* the packet currently being processed by the dns child */
66static struct packet_struct *dns_current;
67
68
69/***************************************************************************
70 return the fd used to gather async dns replies. This is added to the select
71 loop
72 ****************************************************************************/
73
74int asyncdns_fd(void)
75{
76 return fd_in;
77}
78
79/***************************************************************************
80 handle DNS queries arriving from the parent
81 ****************************************************************************/
82static void asyncdns_process(void)
83{
84 struct query_record r;
85 unstring qname;
86
87 DEBUGLEVEL = -1;
88
89 while (1) {
90 NTSTATUS status;
91
92 status = read_data(fd_in, (char *)&r, sizeof(r));
93
94 if (!NT_STATUS_IS_OK(status)) {
95 break;
96 }
97
98 pull_ascii_nstring( qname, sizeof(qname), r.name.name);
99 r.result.s_addr = interpret_addr(qname);
100
101 if (write_data(fd_out, (char *)&r, sizeof(r)) != sizeof(r))
102 break;
103 }
104
105 _exit(0);
106}
107
108/**************************************************************************** **
109 catch a sigterm (in the child process - the parent has a different handler
110 see nmbd.c for details).
111 We need a separate term handler here so we don't release any
112 names that our parent is going to release, or overwrite a
113 WINS db that our parent is going to write.
114 **************************************************************************** */
115
116static void sig_term(int sig)
117{
118 _exit(0);
119}
120
121/***************************************************************************
122 Called by the parent process when it receives a SIGTERM - also kills the
123 child so we don't get child async dns processes lying around, causing trouble.
124 ****************************************************************************/
125
126void kill_async_dns_child(void)
127{
128 if (child_pid > 0) {
129 kill(child_pid, SIGTERM);
130 child_pid = -1;
131 }
132}
133
134/***************************************************************************
135 create a child process to handle DNS lookups
136 ****************************************************************************/
137void start_async_dns(void)
138{
139 int fd1[2], fd2[2];
140
141 CatchChild();
142
143 if (pipe(fd1) || pipe(fd2)) {
144 DEBUG(0,("can't create asyncdns pipes\n"));
145 return;
146 }
147
148 child_pid = sys_fork();
149
150 if (child_pid) {
151 fd_in = fd1[0];
152 fd_out = fd2[1];
153 close(fd1[1]);
154 close(fd2[0]);
155 DEBUG(0,("started asyncdns process %d\n", (int)child_pid));
156 return;
157 }
158
159 fd_in = fd2[0];
160 fd_out = fd1[1];
161
162 CatchSignal(SIGUSR2, SIG_IGN);
163 CatchSignal(SIGUSR1, SIG_IGN);
164 CatchSignal(SIGHUP, SIG_IGN);
165 CatchSignal(SIGTERM, SIGNAL_CAST sig_term );
166
167 if (!NT_STATUS_IS_OK(reinit_after_fork(nmbd_messaging_context(),
168 nmbd_event_context(), true))) {
169 DEBUG(0,("reinit_after_fork() failed\n"));
170 smb_panic("reinit_after_fork() failed");
171 }
172
173 asyncdns_process();
174}
175
176
177/***************************************************************************
178check if a particular name is already being queried
179 ****************************************************************************/
180static bool query_current(struct query_record *r)
181{
182 return dns_current &&
183 nmb_name_equal(&r->name,
184 &dns_current->packet.nmb.question.question_name);
185}
186
187
188/***************************************************************************
189 write a query to the child process
190 ****************************************************************************/
191static bool write_child(struct packet_struct *p)
192{
193 struct query_record r;
194
195 r.name = p->packet.nmb.question.question_name;
196
197 return write_data(fd_out, (char *)&r, sizeof(r)) == sizeof(r);
198}
199
200/***************************************************************************
201 check the DNS queue
202 ****************************************************************************/
203void run_dns_queue(void)
204{
205 struct query_record r;
206 struct packet_struct *p, *p2;
207 struct name_record *namerec;
208 NTSTATUS status;
209
210 if (fd_in == -1)
211 return;
212
213 if (!process_exists_by_pid(child_pid)) {
214 close(fd_in);
215 close(fd_out);
216 start_async_dns();
217 }
218
219 status = read_data(fd_in, (char *)&r, sizeof(r));
220
221 if (!NT_STATUS_IS_OK(status)) {
222 DEBUG(0, ("read from child failed: %s\n", nt_errstr(status)));
223 fd_in = -1;
224 return;
225 }
226
227 namerec = add_dns_result(&r.name, r.result);
228
229 if (dns_current) {
230 if (query_current(&r)) {
231 DEBUG(3,("DNS calling send_wins_name_query_response\n"));
232 in_dns = 1;
233 if(namerec == NULL)
234 send_wins_name_query_response(NAM_ERR, dns_current, NULL);
235 else
236 send_wins_name_query_response(0,dns_current,namerec);
237 in_dns = 0;
238 }
239
240 dns_current->locked = False;
241 free_packet(dns_current);
242 dns_current = NULL;
243 }
244
245 /* loop over the whole dns queue looking for entries that
246 match the result we just got */
247 for (p = dns_queue; p;) {
248 struct nmb_packet *nmb = &p->packet.nmb;
249 struct nmb_name *question = &nmb->question.question_name;
250
251 if (nmb_name_equal(question, &r.name)) {
252 DEBUG(3,("DNS calling send_wins_name_query_response\n"));
253 in_dns = 1;
254 if(namerec == NULL)
255 send_wins_name_query_response(NAM_ERR, p, NULL);
256 else
257 send_wins_name_query_response(0,p,namerec);
258 in_dns = 0;
259 p->locked = False;
260
261 if (p->prev)
262 p->prev->next = p->next;
263 else
264 dns_queue = p->next;
265 if (p->next)
266 p->next->prev = p->prev;
267 p2 = p->next;
268 free_packet(p);
269 p = p2;
270 } else {
271 p = p->next;
272 }
273 }
274
275 if (dns_queue) {
276 dns_current = dns_queue;
277 dns_queue = dns_queue->next;
278 if (dns_queue)
279 dns_queue->prev = NULL;
280 dns_current->next = NULL;
281
282 if (!write_child(dns_current)) {
283 DEBUG(3,("failed to send DNS query to child!\n"));
284 return;
285 }
286 }
287}
288
289/***************************************************************************
290queue a DNS query
291 ****************************************************************************/
292
293bool queue_dns_query(struct packet_struct *p,struct nmb_name *question)
294{
295 if (in_dns || fd_in == -1)
296 return False;
297
298 if (!dns_current) {
299 if (!write_child(p)) {
300 DEBUG(3,("failed to send DNS query to child!\n"));
301 return False;
302 }
303 dns_current = p;
304 p->locked = True;
305 } else {
306 p->locked = True;
307 p->next = dns_queue;
308 p->prev = NULL;
309 if (p->next)
310 p->next->prev = p;
311 dns_queue = p;
312 }
313
314 DEBUG(3,("added DNS query for %s\n", nmb_namestr(question)));
315 return True;
316}
317
318#else
319
320
321/***************************************************************************
322 we use this when we can't do async DNS lookups
323 ****************************************************************************/
324
325bool queue_dns_query(struct packet_struct *p,struct nmb_name *question)
326{
327 struct name_record *namerec = NULL;
328 struct in_addr dns_ip;
329 unstring qname;
330
331 pull_ascii_nstring(qname, sizeof(qname), question->name);
332
333 DEBUG(3,("DNS search for %s - ", nmb_namestr(question)));
334
335 dns_ip.s_addr = interpret_addr(qname);
336
337 namerec = add_dns_result(question, dns_ip);
338 if(namerec == NULL) {
339 send_wins_name_query_response(NAM_ERR, p, NULL);
340 } else {
341 send_wins_name_query_response(0, p, namerec);
342 }
343 return False;
344}
345
346/***************************************************************************
347 With sync dns there is no child to kill on SIGTERM.
348 ****************************************************************************/
349
350void kill_async_dns_child(void)
351{
352 return;
353}
354#endif
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