e82f7154 |
1 | /* -*-c-*- |
2 | * |
3 | * $Id: bres.c,v 1.1 1999/07/01 08:56:23 mdw Exp $ |
4 | * |
5 | * Background reverse name resolution |
6 | * |
7 | * (c) 1999 Mark Wooding |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
11 | * |
12 | * This file is part of the `fw' port forwarder. |
13 | * |
14 | * `fw' is free software; you can redistribute it and/or modify |
15 | * it under the terms of the GNU General Public License as published by |
16 | * the Free Software Foundation; either version 2 of the License, or |
17 | * (at your option) any later version. |
18 | * |
19 | * `fw' is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
22 | * GNU General Public License for more details. |
23 | * |
24 | * You should have received a copy of the GNU General Public License |
25 | * along with `fw'; if not, write to the Free Software Foundation, |
26 | * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
27 | */ |
28 | |
29 | /*----- Revision history --------------------------------------------------* |
30 | * |
31 | * $Log: bres.c,v $ |
32 | * Revision 1.1 1999/07/01 08:56:23 mdw |
33 | * Initial revision |
34 | * |
35 | */ |
36 | |
37 | /*----- Header files ------------------------------------------------------*/ |
38 | |
39 | #include <errno.h> |
40 | #include <signal.h> |
41 | #include <stdio.h> |
42 | #include <stdlib.h> |
43 | #include <string.h> |
44 | |
45 | #include <sys/types.h> |
46 | #include <sys/time.h> |
47 | #include <unistd.h> |
48 | #include <sys/wait.h> |
49 | |
50 | #include <sys/socket.h> |
51 | #include <netinet/in.h> |
52 | #include <arpa/inet.h> |
53 | #include <netdb.h> |
54 | |
55 | #include <mLib/report.h> |
56 | #include <mLib/sel.h> |
57 | #include <mLib/selbuf.h> |
58 | |
59 | #include "bres.h" |
60 | |
61 | /*----- Magic numbers -----------------------------------------------------*/ |
62 | |
63 | #define BRES_MAX 5 /* Maximum number of resolvers */ |
64 | #define BRES_IDLE 60 /* Lifetime of an idle resolver */ |
65 | |
66 | /*----- Static variables --------------------------------------------------*/ |
67 | |
68 | static bres_server servers[BRES_MAX]; /* Statically allocated servers */ |
69 | |
70 | #define FREE ((bres_server *)&freelist) |
71 | static struct { bres_server *next, *prev; } freelist = { FREE, FREE }; |
72 | |
73 | #define QUEUE ((bres_client *)&queue) |
74 | static struct { bres_client *next, *prev; } queue = { QUEUE, QUEUE }; |
75 | |
76 | static sel_state *sel; |
77 | |
78 | /*----- Main code ---------------------------------------------------------*/ |
79 | |
80 | /* --- @zap@ --- * |
81 | * |
82 | * Arguments: @bres_server *rs@ = pointer to server block |
83 | * |
84 | * Returns: --- |
85 | * |
86 | * Use: Kills a server process, reaps the losing child and makes |
87 | * things generally clean again. |
88 | */ |
89 | |
90 | static void zap(bres_server *rs) |
91 | { |
92 | /* --- Close the pipes, kill the child, and reap it --- */ |
93 | |
94 | if (rs->kid != -1) { |
95 | selbuf_disable(&rs->b); |
96 | close(rs->fd); |
97 | close(rs->b.reader.fd); |
98 | kill(rs->kid, SIGTERM); |
99 | waitpid(rs->kid, 0, 0); |
100 | rs->kid = -1; |
101 | } |
102 | |
103 | /* --- Move the server to the back of the list --- */ |
104 | |
105 | rs->next->prev = rs->prev; |
106 | rs->prev->next = rs->next; |
107 | rs->next = FREE; |
108 | rs->prev = FREE->prev; |
109 | FREE->prev->next = rs; |
110 | FREE->prev = rs; |
111 | } |
112 | |
113 | /* --- @bres_abort@ --- * |
114 | * |
115 | * Arguments: @bres_client *rc@ = pointer to client block |
116 | * |
117 | * Returns: --- |
118 | * |
119 | * Use: Removes a queued job. |
120 | */ |
121 | |
122 | void bres_abort(bres_client *rc) |
123 | { |
124 | if (rc->rs) { |
125 | zap(rc->rs); |
126 | rc->rs = 0; |
127 | } else { |
128 | rc->next->prev = rc->prev; |
129 | rc->prev->next = rc->next; |
130 | } |
131 | } |
132 | |
133 | /* --- @child@ --- * |
134 | * |
135 | * Arguments: @int rfd@ = output file descriptor for resolved hostnames |
136 | * @int cfd@ = input file descriptor for raw addresses |
137 | * |
138 | * Returns: Never. |
139 | * |
140 | * Use: Asynchronous name resolving process. |
141 | */ |
142 | |
143 | static void child(int rfd, int cfd) |
144 | { |
145 | struct in_addr addr; |
146 | FILE *fp = fdopen(rfd, "w"); |
147 | |
148 | { |
149 | int i; |
150 | int maxfd = sysconf(_SC_OPEN_MAX); |
151 | |
152 | for (i = 0; i < maxfd; i++) { |
153 | if (i != rfd && i != cfd) |
154 | close(i); |
155 | } |
156 | } |
157 | |
158 | for (;;) { |
159 | int r = read(cfd, &addr, sizeof(addr)); |
160 | struct hostent *h; |
161 | char *p; |
162 | |
163 | if (r <= 0) |
164 | break; |
165 | else if (r != sizeof(addr)) |
166 | continue; |
167 | |
168 | h = gethostbyaddr((char *)&addr, sizeof(addr), AF_INET); |
169 | if (h) |
170 | p = h->h_name; |
171 | else |
172 | p = inet_ntoa(addr); |
173 | fprintf(fp, "%s\n", p); |
174 | fflush(fp); |
175 | } |
176 | _exit(0); |
177 | } |
178 | |
179 | /* --- @idle@ --- * |
180 | * |
181 | * Arguments: @struct timeval *tv@ = pointer to the current time |
182 | * @void *vp@ = pointer to a server block |
183 | * |
184 | * Returns: --- |
185 | * |
186 | * Use: Kills off a child which has been idle for too long. |
187 | */ |
188 | |
189 | static void idle(struct timeval *tv, void *vp) |
190 | { |
191 | bres_server *rs = vp; |
192 | zap(rs); |
193 | } |
194 | |
195 | /* --- @answer@ --- * |
196 | * |
197 | * Arguments: @char *p@ = pointer to string read |
198 | * @void *vp@ = pointer to server block |
199 | * |
200 | * Returns: --- |
201 | * |
202 | * Use: Retrieves an answer from a name resolver process. |
203 | */ |
204 | |
205 | static void attach(bres_client */*rc*/); |
206 | |
207 | static void answer(char *p, void *vp) |
208 | { |
209 | bres_server *rs = vp; |
210 | bres_client *rc = rs->rc; |
211 | |
212 | /* --- Report the result to my client --- */ |
213 | |
214 | if (rc) |
215 | rc->func(p, rc->p); |
216 | if (!p) |
217 | zap(rs); |
218 | if (!rc) |
219 | return; |
220 | |
221 | /* --- Wrap up the various structures --- */ |
222 | |
223 | rs->rc = 0; |
224 | rc->rs = 0; |
225 | rs->next = FREE->next; |
226 | rs->prev = FREE; |
227 | FREE->next->prev = rs; |
228 | FREE->next = rs; |
229 | |
230 | /* --- Tie a timer onto the server block --- */ |
231 | |
232 | { |
233 | struct timeval tv; |
234 | |
235 | gettimeofday(&tv, 0); |
236 | tv.tv_sec += BRES_IDLE; |
237 | sel_addtimer(sel, &rs->t, &tv, idle, rs); |
238 | } |
239 | |
240 | /* --- If there are any clients waiting, attach one --- */ |
241 | |
242 | if (QUEUE->next != QUEUE) { |
243 | rc = QUEUE->next; |
244 | QUEUE->next = rc->next; |
245 | rc->next->prev = QUEUE; |
246 | attach(rc); |
247 | } |
248 | } |
249 | |
250 | /* --- @start@ --- * |
251 | * |
252 | * Arguments: @bres_server *rs@ = pointer to a server block |
253 | * |
254 | * Returns: Zero if OK, nonzero if something failed. |
255 | * |
256 | * Use: Starts up a child resolver process. |
257 | */ |
258 | |
259 | static int start(bres_server *rs) |
260 | { |
261 | int rfd[2], cfd[2]; |
262 | pid_t kid; |
263 | |
264 | /* --- Make the pipes --- */ |
265 | |
266 | if (pipe(rfd)) |
267 | goto fail_0; |
268 | if (pipe(cfd)) |
269 | goto fail_1; |
270 | |
271 | /* --- Start up the child process --- */ |
272 | |
273 | if ((kid = fork()) < 0) |
274 | goto fail_2; |
275 | if (kid == 0) { |
276 | close(cfd[1]); |
277 | close(rfd[0]); |
278 | child(rfd[1], cfd[0]); |
279 | _exit(1); |
280 | } |
281 | |
282 | /* --- Fix up everything in the server block --- */ |
283 | |
284 | close(cfd[0]); |
285 | close(rfd[1]); |
286 | rs->fd = cfd[1]; |
287 | selbuf_init(&rs->b, sel, rfd[0], answer, rs); |
288 | rs->kid = kid; |
289 | return (0); |
290 | |
291 | /* --- Fix up after errors --- */ |
292 | |
293 | fail_2: |
294 | close(cfd[0]); |
295 | close(cfd[1]); |
296 | fail_1: |
297 | close(rfd[0]); |
298 | close(rfd[1]); |
299 | fail_0: |
300 | return (-1); |
301 | } |
302 | |
303 | /* --- @attach@ --- * |
304 | * |
305 | * Arguments: @bres_client *rc@ = pointer to a client block |
306 | * |
307 | * Returns: --- |
308 | * |
309 | * Use: Attaches a client to a spare server (which is assumed to |
310 | * exist). |
311 | */ |
312 | |
313 | static void attach(bres_client *rc) |
314 | { |
315 | bres_server *rs; |
316 | int lose = 0; |
317 | |
318 | /* --- Fix up the server ready for the job --- * |
319 | * |
320 | * If the server has a process, remove its timer. Otherwise, fork off a |
321 | * new resolver process. This is also where I go if I find that the child |
322 | * resolver process has lost while I wasn't looking. Only one attempt at |
323 | * forking is performed. |
324 | */ |
325 | |
326 | again: |
327 | rs = FREE->next; |
328 | if (rs->kid != -1) |
329 | sel_rmtimer(&rs->t); |
330 | else { |
331 | if (lose || start(rs)) |
332 | goto lost; |
333 | lose = 1; |
334 | } |
335 | |
336 | /* --- Submit the job to the resolver --- */ |
337 | |
338 | { |
339 | struct sigaction sa, osa; |
340 | int e; |
341 | |
342 | /* --- Ignore @SIGPIPE@ for now --- * |
343 | * |
344 | * This way I can trap @EPIPE@ and reap a losing child, if there was one. |
345 | */ |
346 | |
347 | sa.sa_handler = SIG_IGN; |
348 | sa.sa_flags = 0; |
349 | sigemptyset(&sa.sa_mask); |
350 | sigaction(SIGPIPE, &sa, &osa); |
351 | |
352 | /* --- Write the new job to the child --- */ |
353 | |
354 | e = 0; |
355 | if (write(rs->fd, &rc->addr, sizeof(rc->addr)) < 0) |
356 | e = errno; |
357 | sigaction(SIGPIPE, &osa, 0); |
358 | |
359 | /* --- Sort out various errors --- */ |
360 | |
361 | if (e == EPIPE) { |
362 | zap(rs); |
363 | goto again; |
364 | } else if (e) |
365 | goto lost; |
366 | } |
367 | |
368 | /* --- Fiddle with lists so that everything's OK --- */ |
369 | |
370 | rs->next->prev = FREE; |
371 | FREE->next = rs->next; |
372 | rs->next = rs->prev = rs; |
373 | rs->rc = rc; |
374 | rc->rs = rs; |
375 | return; |
376 | |
377 | lost: |
378 | rc->func(0, rc->p); |
379 | } |
380 | |
381 | /* --- @bres_resolve@ --- * |
382 | * |
383 | * Arguments: @bres_client *rc@ = pointer to client block |
384 | * @struct in_addr addr@ = address to resolve |
385 | * @void (*func)(const char *host, void *p)@ = handler function |
386 | * @void *p@ = argument for handler function |
387 | * |
388 | * Returns: --- |
389 | * |
390 | * Use: Adds a resolver job to the queue. The job will be processed |
391 | * when there's a spare resolver process to deal with it. |
392 | */ |
393 | |
394 | void bres_resolve(bres_client *rc, struct in_addr addr, |
395 | void (*func)(const char */*host*/, void */*p*/), void *p) |
396 | { |
397 | /* --- Fill in the structure --- */ |
398 | |
399 | rc->addr = addr; |
400 | rc->func = func; |
401 | rc->p = p; |
402 | rc->rs = 0; |
403 | |
404 | /* --- If there's a free server, plug it in --- */ |
405 | |
406 | if (FREE->next == FREE) { |
407 | rc->next = QUEUE; |
408 | rc->prev = QUEUE->prev; |
409 | QUEUE->prev->next = rc; |
410 | QUEUE->prev = rc; |
411 | } else |
412 | attach(rc); |
413 | } |
414 | |
415 | /* --- @bres_init@ --- * |
416 | * |
417 | * Arguments: @sel_state *s@ = pointer to select multiplexor |
418 | * |
419 | * Returns: --- |
420 | * |
421 | * Use: Initializes the background resolver for use. |
422 | */ |
423 | |
424 | void bres_init(sel_state *s) |
425 | { |
426 | int i; |
427 | |
428 | sel = s; |
429 | for (i = 0; i < BRES_MAX; i++) { |
430 | servers[i].next = FREE; |
431 | servers[i].prev = FREE->prev; |
432 | servers[i].kid = -1; |
433 | servers[i].rc = 0; |
434 | FREE->prev->next = &servers[i]; |
435 | FREE->prev = &servers[i]; |
436 | } |
437 | } |
438 | |
439 | /*----- That's all, folks -------------------------------------------------*/ |