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1 | /* -*-c-*- |
2 | * |
e2a18bd0 |
3 | * $Id: bres.c,v 1.3 2000/06/17 10:38:35 mdw Exp $ |
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4 | * |
5 | * Background reverse name resolution |
6 | * |
7 | * (c) 1999 Straylight/Edgeware |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
11 | * |
12 | * This file is part of the mLib utilities library. |
13 | * |
14 | * mLib is free software; you can redistribute it and/or modify |
15 | * it under the terms of the GNU Library General Public License as |
16 | * published by the Free Software Foundation; either version 2 of the |
17 | * License, or (at your option) any later version. |
18 | * |
19 | * mLib 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 Library General Public License for more details. |
23 | * |
24 | * You should have received a copy of the GNU Library General Public |
25 | * License along with mLib; if not, write to the Free |
26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
27 | * MA 02111-1307, USA. |
28 | */ |
29 | |
30 | /*----- Revision history --------------------------------------------------* |
31 | * |
32 | * $Log: bres.c,v $ |
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33 | * Revision 1.3 2000/06/17 10:38:35 mdw |
34 | * Track changes to selbuf interface. |
35 | * |
6c3a7cf7 |
36 | * Revision 1.2 1999/10/30 11:28:39 mdw |
37 | * Fix include error, pointed out by Chris Rutter. |
38 | * |
a759efa6 |
39 | * Revision 1.1 1999/10/04 21:40:42 mdw |
40 | * Added background resolver from `fw'. |
41 | * |
42 | */ |
43 | |
44 | /*----- Header files ------------------------------------------------------*/ |
45 | |
46 | #include <errno.h> |
47 | #include <signal.h> |
48 | #include <stdio.h> |
49 | #include <stdlib.h> |
50 | #include <string.h> |
51 | |
52 | #include <sys/types.h> |
53 | #include <sys/time.h> |
54 | #include <unistd.h> |
55 | #include <sys/wait.h> |
56 | |
57 | #include <sys/socket.h> |
58 | #include <netinet/in.h> |
59 | #include <arpa/inet.h> |
60 | #include <netdb.h> |
61 | |
6c3a7cf7 |
62 | #include "alloc.h" |
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63 | #include "bres.h" |
6c3a7cf7 |
64 | #include "report.h" |
65 | #include "sel.h" |
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66 | |
67 | /*----- Magic numbers -----------------------------------------------------*/ |
68 | |
69 | #define BRES_MAX 15 /* Maximum number of resolvers */ |
70 | #define BRES_IDLE 60 /* Lifetime of an idle resolver */ |
71 | |
72 | /*----- Static variables --------------------------------------------------*/ |
73 | |
74 | #ifndef BRES_STANDALONE |
75 | |
76 | static bres_server servers[BRES_MAX]; /* Statically allocated servers */ |
77 | |
78 | #define FREE ((bres_server *)&freelist) |
79 | static struct { bres_server *next, *prev; } freelist = { FREE, FREE }; |
80 | |
81 | #define QUEUE ((bres_client *)&queue) |
82 | static struct { bres_client *next, *prev; } queue = { QUEUE, QUEUE }; |
83 | |
84 | static sel_state *sel; |
85 | |
86 | static const char *server = 0; |
87 | |
88 | #endif |
89 | |
90 | /*----- Background resolver protocol --------------------------------------*/ |
91 | |
92 | /* --- Requests and responses --- * |
93 | * |
94 | * There are two types of requests: name and addr, corresponding to the |
95 | * standard @gethostbyname@ and @gethostbyaddr@ calls. There are two types |
96 | * of responses too: a positive response consists of an encoded equivalent of |
97 | * a @struct hostent@ structure containing the requested information; a |
98 | * negative response consists of an @h_errno@ value explaining the problem. |
99 | */ |
100 | |
101 | #define BRES_BYNAME 0 /* Request: resolve given name */ |
102 | #define BRES_BYADDR 1 /* Request: resolve given address */ |
103 | |
104 | #define BRES_HOSTENT 0 /* Response: resolved ok */ |
105 | #define BRES_ERROR 1 /* Response: resolution failed */ |
106 | |
107 | /* --- Encodings --- * |
108 | * |
109 | * A string is encoded as a @size_t@ length followed by the actual data. The |
110 | * null terminator is not transmitted. |
111 | * |
112 | * Addresses for resolution are transmitted as raw @struct in_addr@ |
113 | * structures. |
114 | * |
115 | * A @hostent@ structure is transmitted as a header containing fixed-size |
116 | * information, followed by the official name, an array of aliases, and an |
117 | * array of addresses. The number of items in the arrays is specified in the |
118 | * header. |
119 | * |
120 | * The implementation assumes that a complete request or reply is always |
121 | * sent. Undesirable blocking will occur if this is not the case. Both ends |
122 | * are assumed to trust each other. A protocol failure results in the child |
123 | * in question being terminated. |
124 | */ |
125 | |
126 | typedef struct hostskel { |
127 | size_t nalias; |
128 | int addrtype; |
129 | size_t addrsz; |
130 | size_t naddr; |
131 | } hostskel; |
132 | |
133 | /* --- @doread@, @dowrite@ --- * |
134 | * |
135 | * Arguments: @int fd@ = file descriptor |
136 | * @void *buf@ = buffer for data |
137 | * @size_t sz@ = size of data |
138 | * |
139 | * Returns: Zero if successful, nonzero otherwise. |
140 | * |
141 | * Use: Reads or writes a chunk of data. @EINTR@ errors are retried; |
142 | * incomplete reads and writes are continued from where they |
143 | * left off. End-of-file is considered an I/O error. |
144 | */ |
145 | |
146 | static int doread(int fd, void *buf, size_t sz) |
147 | { |
148 | char *p = buf; |
149 | while (sz) { |
150 | int r = read(fd, p, sz); |
151 | if (r < 0) { |
152 | if (errno == EINTR) |
153 | continue; |
154 | return (-1); |
155 | } else if (r == 0) { |
156 | errno = EIO; |
157 | return (-1); |
158 | } |
159 | sz -= r; |
160 | p += r; |
161 | } |
162 | return (0); |
163 | } |
164 | |
165 | static int dowrite(int fd, const void *buf, size_t sz) |
166 | { |
167 | const char *p = buf; |
168 | while (sz) { |
169 | int r = write(fd, p, sz); |
170 | if (r < 0) { |
171 | if (errno == EINTR) |
172 | continue; |
173 | return (-1); |
174 | } else if (r == 0) { |
175 | errno = EIO; |
176 | return (-1); |
177 | } |
178 | sz -= r; |
179 | p += r; |
180 | } |
181 | return (0); |
182 | } |
183 | |
184 | /* --- @getstring@ --- * |
185 | * |
186 | * Arguments: @int fd@ = file descriptor to read |
187 | * |
188 | * Returns: String in heap-allocated block, or a null pointer. |
189 | * |
190 | * Use: Decodes a string. |
191 | */ |
192 | |
193 | static char *getstring(int fd) |
194 | { |
195 | size_t sz; |
196 | char *p; |
197 | |
198 | if (doread(fd, &sz, sizeof(sz)) || (p = malloc(sz + 1)) == 0) |
199 | return (0); |
200 | if (doread(fd, p, sz)) { |
201 | free(p); |
202 | return (0); |
203 | } |
204 | p[sz] = 0; |
205 | return (p); |
206 | } |
207 | |
208 | /* --- @putstring@ --- * |
209 | * |
210 | * Arguments: @int fd@ = file descriptor to write on |
211 | * @const char *p@ = pointer to string to write |
212 | * |
213 | * Returns: Zero if successful. |
214 | * |
215 | * Use: Encodes a string. |
216 | */ |
217 | |
218 | static int putstring(int fd, const char *p) |
219 | { |
220 | size_t sz = strlen(p); |
221 | if (dowrite(fd, &sz, sizeof(sz)) || dowrite(fd, p, sz)) |
222 | return (-1); |
223 | return (0); |
224 | } |
225 | |
226 | /* --- @gethost@ --- * |
227 | * |
228 | * Arguments: @int fd@ = file descriptor to read |
229 | * |
230 | * Returns: Pointer to heap-allocated @struct hostent@, or null. |
231 | * |
232 | * Use: Decodes a host structure. The resulting structure is all in |
233 | * one big heap block. |
234 | */ |
235 | |
236 | #ifndef BRES_STANDALONE |
237 | |
238 | static struct hostent *gethost(int fd) |
239 | { |
240 | hostskel hsk; |
241 | struct hostent *h; |
242 | char *name; |
243 | char **alias = 0; |
244 | |
245 | /* --- Read the skeleton structure --- */ |
246 | |
247 | if (doread(fd, &hsk, sizeof(hsk))) |
248 | goto tidy_0; |
249 | |
250 | /* --- Read the hostname and alias strings --- * |
251 | * |
252 | * Count the length of the strings as we go. |
253 | */ |
254 | |
255 | { |
256 | size_t sz = |
257 | sizeof(struct hostent) + |
258 | hsk.naddr * hsk.addrsz + |
259 | (hsk.naddr + hsk.nalias + 2) * sizeof(char *); |
260 | |
261 | /* --- Read the primary host name --- */ |
262 | |
263 | if ((name = getstring(fd)) == 0) |
264 | goto tidy_0; |
265 | sz += strlen(name) + 1; |
266 | |
267 | /* --- Read in the alias names --- */ |
268 | |
269 | if (hsk.nalias) { |
270 | int i; |
271 | if ((alias = malloc(hsk.nalias * sizeof(char *))) == 0) |
272 | goto tidy_1; |
273 | for (i = 0; i < hsk.nalias; i++) |
274 | alias[i] = 0; |
275 | for (i = 0; i < hsk.nalias; i++) { |
276 | if ((alias[i] = getstring(fd)) == 0) |
277 | goto tidy_2; |
278 | sz += strlen(alias[i]) + 1; |
279 | } |
280 | } |
281 | |
282 | /* --- Allocate the output structure --- */ |
283 | |
284 | if ((h = malloc(sz)) == 0) |
285 | goto tidy_2; |
286 | } |
287 | |
288 | /* --- Fill in the base structure --- */ |
289 | |
290 | h->h_addrtype = hsk.addrtype; |
291 | h->h_length = hsk.addrsz; |
292 | |
293 | /* --- Start putting everything else in --- */ |
294 | |
295 | { |
296 | char **p = (char **)(h + 1); |
297 | char *a = (char *)(p + hsk.nalias + hsk.naddr + 2); |
298 | int i; |
299 | |
300 | /* --- Start with the address table --- */ |
301 | |
302 | h->h_addr_list = p; |
303 | if (doread(fd, a, hsk.naddr * hsk.addrsz)) |
304 | goto tidy_2; |
305 | for (i = 0; i < hsk.naddr; i++) { |
306 | struct in_addr in; |
307 | *p++ = a; |
308 | memcpy(&in, a, sizeof(in)); |
309 | } |
310 | *p++ = 0; |
311 | |
312 | /* --- Finally copy the strings over --- */ |
313 | |
314 | #define PUT(_p) do { \ |
315 | size_t _len = strlen(_p) + 1; \ |
316 | memcpy(a, (_p), _len); \ |
317 | a += _len; \ |
318 | } while (0) |
319 | |
320 | h->h_name = a; |
321 | PUT(name); |
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322 | xfree(name); |
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323 | h->h_aliases = p; |
324 | for (i = 0; i < hsk.nalias; i++) { |
325 | *p++ = a; |
326 | PUT(alias[i]); |
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327 | xfree(alias[i]); |
a759efa6 |
328 | } |
329 | *p++ = 0; |
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330 | xfree(alias); |
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331 | |
332 | #undef PUT |
333 | } |
334 | |
335 | return (h); |
336 | |
337 | /* --- Tidy up after various types of failure --- */ |
338 | |
339 | tidy_2: |
340 | { |
341 | int i; |
342 | for (i = 0; i < hsk.nalias && alias[i]; i++) |
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343 | xfree(alias[i]); |
344 | xfree(alias); |
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345 | } |
346 | tidy_1: |
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347 | xfree(name); |
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348 | tidy_0: |
349 | return (0); |
350 | } |
351 | |
352 | #endif |
353 | |
354 | /* --- @puthost@ --- * |
355 | * |
356 | * Arguments: @int fd@ = file descriptor |
357 | * @struct hostent *h@ = pointer to host structure |
358 | * |
359 | * Returns: Zero if successful. |
360 | * |
361 | * Use: Encodes a host structure. |
362 | */ |
363 | |
364 | static int puthost(int fd, struct hostent *h) |
365 | { |
366 | hostskel hsk; |
367 | int i; |
368 | |
369 | /* --- Fill in and send the skeleton structure --- */ |
370 | |
371 | for (i = 0; h->h_aliases[i]; i++) |
372 | ; |
373 | hsk.nalias = i; |
374 | for (i = 0; h->h_addr_list[i]; i++) |
375 | ; |
376 | hsk.naddr = i; |
377 | hsk.addrtype = h->h_addrtype; |
378 | hsk.addrsz = h->h_length; |
379 | if (dowrite(fd, &hsk, sizeof(hsk))) |
380 | return (-1); |
381 | |
382 | /* --- Send the name and alias strings --- */ |
383 | |
384 | if (putstring(fd, h->h_name)) |
385 | return (-1); |
386 | for (i = 0; h->h_aliases[i]; i++) { |
387 | if (putstring(fd, h->h_aliases[i])) |
388 | return (-1); |
389 | } |
390 | |
391 | /* --- Send the address data --- */ |
392 | |
393 | for (i = 0; h->h_addr_list[i]; i++) { |
394 | if (dowrite(fd, h->h_addr_list[i], hsk.addrsz)) |
395 | return (-1); |
396 | } |
397 | |
398 | /* --- OK, done --- */ |
399 | |
400 | return (0); |
401 | } |
402 | |
403 | /*----- Resolver server ---------------------------------------------------*/ |
404 | |
405 | /* --- @child@ --- * |
406 | * |
407 | * Arguments: @int rfd@ = output file descriptor for resolved hostnames |
408 | * @int cfd@ = input file descriptor for raw addresses |
409 | * |
410 | * Returns: Never. |
411 | * |
412 | * Use: Asynchronous name resolving process. |
413 | */ |
414 | |
415 | static void child(int rfd, int cfd) |
416 | { |
417 | /* --- Close other file descriptors --- */ |
418 | |
419 | { |
420 | int i; |
421 | int maxfd = sysconf(_SC_OPEN_MAX); |
422 | |
423 | if (maxfd < 0) |
424 | maxfd = 256; /* Fingers crossed... */ |
425 | for (i = 0; i < maxfd; i++) { |
426 | if (i != rfd && i != cfd && i != 1) |
427 | close(i); |
428 | } |
429 | } |
430 | |
431 | /* --- Main request/response loop --- */ |
432 | |
433 | for (;;) { |
434 | int req, resp; |
435 | struct hostent *h; |
436 | |
437 | /* --- Read the request --- */ |
438 | |
439 | if (doread(cfd, &req, sizeof(req))) |
440 | goto lose; |
441 | |
442 | /* --- Process it into a host structure --- */ |
443 | |
444 | switch (req) { |
445 | |
446 | /* --- Normal forward lookup --- */ |
447 | |
448 | case BRES_BYNAME: { |
449 | char *name = getstring(cfd); |
450 | if (!name) |
451 | goto lose; |
452 | h = gethostbyname(name); |
453 | free(name); |
454 | } break; |
455 | |
456 | /* --- Forward lookup --- */ |
457 | |
458 | case BRES_BYADDR: { |
459 | struct in_addr addr; |
460 | char *p; |
461 | if (doread(cfd, &addr, sizeof(addr))) |
462 | goto lose; |
463 | if ((h = gethostbyaddr((char *)&addr, sizeof(addr), AF_INET)) == 0) |
464 | goto fail; |
465 | |
466 | /* --- Do a forward lookup to confirm --- */ |
467 | |
468 | { |
469 | size_t sz = strlen(h->h_name) + 1; |
470 | if ((p = malloc(sz)) == 0) |
471 | goto fail; |
472 | memcpy(p, h->h_name, sz); |
473 | } |
474 | |
475 | h = gethostbyname(p); |
476 | free(p); |
477 | if (!h) |
478 | goto fail; |
479 | p = 0; |
480 | if (h) { |
481 | char **pp; |
482 | for (pp = h->h_addr_list; *pp; pp++) { |
483 | struct in_addr a; |
484 | memcpy(&a, *pp, sizeof(a)); |
485 | if (a.s_addr == addr.s_addr) { |
486 | p = h->h_name; |
487 | break; |
488 | } |
489 | } |
490 | } |
491 | if (!p) { |
492 | h = 0; |
493 | h_errno = NO_RECOVERY; |
494 | } |
495 | fail:; |
496 | } break; |
497 | |
498 | /* --- Unknown request -- may have lost sync --- */ |
499 | |
500 | default: |
501 | goto lose; |
502 | } |
503 | |
504 | /* --- Transmit the response --- */ |
505 | |
506 | if (h) { |
507 | resp = BRES_HOSTENT; |
508 | if (dowrite(rfd, &resp, sizeof(resp)) || puthost(rfd, h)) |
509 | goto lose; |
510 | } else { |
511 | resp = BRES_ERROR; |
512 | if (dowrite(rfd, &resp, sizeof(resp)) || |
513 | dowrite(rfd, &h_errno, sizeof(h_errno))) |
514 | goto lose; |
515 | } |
516 | } |
517 | |
518 | lose: |
519 | _exit(1); |
520 | } |
521 | |
522 | /* --- @main@ --- * |
523 | * |
524 | * Arguments: @int argc@ = number of command line arguments |
525 | * @char *argv[]@ = array of arguments |
526 | * |
527 | * Returns: Runs until killed or an error occurs. |
528 | * |
529 | * Use: A name resolver server process for mLib programs which need |
530 | * this sort of thing. |
531 | */ |
532 | |
533 | #ifdef BRES_STANDALONE |
534 | |
535 | int main(int argc, char *argv[]) |
536 | { |
537 | if (isatty(STDIN_FILENO)) { |
538 | char *p = strrchr(argv[0], '/'); |
539 | if (p) |
540 | p++; |
541 | else |
542 | p = argv[0]; |
543 | fprintf(stderr, |
544 | "%s: don't run this program unless you know what you're doing.\n", |
545 | p); |
546 | exit(1); |
547 | } |
548 | child(STDOUT_FILENO, STDIN_FILENO); |
549 | return (1); |
550 | } |
551 | |
552 | #endif |
553 | |
554 | /*----- Main code ---------------------------------------------------------*/ |
555 | |
556 | #ifndef BRES_STANDALONE |
557 | |
558 | /* --- @zap@ --- * |
559 | * |
560 | * Arguments: @bres_server *rs@ = pointer to server block |
561 | * |
562 | * Returns: --- |
563 | * |
564 | * Use: Kills a server process, reaps the losing child and makes |
565 | * things generally clean again. |
566 | */ |
567 | |
568 | static void zap(bres_server *rs) |
569 | { |
570 | /* --- Close the pipes, kill the child, and reap it --- */ |
571 | |
572 | if (rs->kid != -1) { |
573 | close(rs->fd); |
574 | close(rs->f.fd); |
575 | kill(rs->kid, SIGTERM); |
576 | waitpid(rs->kid, 0, 0); |
577 | rs->kid = -1; |
578 | } |
579 | |
580 | /* --- Move the server to the back of the list --- */ |
581 | |
582 | rs->next->prev = rs->prev; |
583 | rs->prev->next = rs->next; |
584 | rs->next = FREE; |
585 | rs->prev = FREE->prev; |
586 | FREE->prev->next = rs; |
587 | FREE->prev = rs; |
588 | } |
589 | |
590 | /* --- @bres_abort@ --- * |
591 | * |
592 | * Arguments: @bres_client *rc@ = pointer to client block |
593 | * |
594 | * Returns: --- |
595 | * |
596 | * Use: Removes a queued job. |
597 | */ |
598 | |
599 | void bres_abort(bres_client *rc) |
600 | { |
601 | if (rc->q == BRES_BYNAME) |
e2a18bd0 |
602 | xfree(rc->u.name); |
a759efa6 |
603 | if (rc->rs) { |
604 | sel_rmfile(&rc->rs->f); |
605 | zap(rc->rs); |
606 | rc->rs = 0; |
607 | } else { |
608 | rc->next->prev = rc->prev; |
609 | rc->prev->next = rc->next; |
610 | } |
611 | } |
612 | |
613 | /* --- @idle@ --- * |
614 | * |
615 | * Arguments: @struct timeval *tv@ = pointer to the current time |
616 | * @void *vp@ = pointer to a server block |
617 | * |
618 | * Returns: --- |
619 | * |
620 | * Use: Kills off a child which has been idle for too long. |
621 | */ |
622 | |
623 | static void idle(struct timeval *tv, void *vp) |
624 | { |
625 | bres_server *rs = vp; |
626 | zap(rs); |
627 | } |
628 | |
629 | /* --- @answer@ --- * |
630 | * |
631 | * Arguments: @int fd@ = file descriptor which is ready |
632 | * @unsigned mode@ = what it's doing now |
633 | * @void *vp@ = pointer to server block |
634 | * |
635 | * Returns: --- |
636 | * |
637 | * Use: Retrieves an answer from a name resolver process. |
638 | */ |
639 | |
640 | static void attach(bres_client */*rc*/); |
641 | |
642 | static void answer(int fd, unsigned mode, void *vp) |
643 | { |
644 | bres_server *rs = vp; |
645 | bres_client *rc = rs->rc; |
646 | struct hostent *h = 0; |
647 | int resp; |
648 | int fail = 1; |
649 | |
650 | /* --- Report the result to my client --- */ |
651 | |
652 | sel_rmfile(&rs->f); |
653 | h_errno = -1; |
654 | if (doread(fd, &resp, sizeof(resp)) == 0) { |
655 | switch (resp) { |
656 | case BRES_ERROR: |
657 | doread(fd, &h_errno, sizeof(h_errno)); |
658 | fail = 0; |
659 | break; |
660 | case BRES_HOSTENT: |
661 | h = gethost(fd); |
662 | fail = 0; |
663 | break; |
664 | } |
665 | } |
666 | if (rc) { |
667 | rc->func(h, rc->p); |
668 | if (rc->q == BRES_BYNAME) |
e2a18bd0 |
669 | xfree(rc->u.name); |
a759efa6 |
670 | } |
671 | if (h) |
e2a18bd0 |
672 | xfree(h); |
a759efa6 |
673 | if (fail) |
674 | zap(rs); |
675 | if (!rc) |
676 | return; |
677 | |
678 | /* --- Wrap up the various structures --- */ |
679 | |
680 | rs->rc = 0; |
681 | rc->rs = 0; |
682 | rs->next = FREE->next; |
683 | rs->prev = FREE; |
684 | FREE->next->prev = rs; |
685 | FREE->next = rs; |
686 | |
687 | /* --- Tie a timer onto the server block --- */ |
688 | |
689 | { |
690 | struct timeval tv; |
691 | |
692 | gettimeofday(&tv, 0); |
693 | tv.tv_sec += BRES_IDLE; |
694 | sel_addtimer(sel, &rs->t, &tv, idle, rs); |
695 | } |
696 | |
697 | /* --- If there are any clients waiting, attach one --- */ |
698 | |
699 | if (QUEUE->next != QUEUE) { |
700 | rc = QUEUE->next; |
701 | QUEUE->next = rc->next; |
702 | rc->next->prev = QUEUE; |
703 | attach(rc); |
704 | } |
705 | } |
706 | |
707 | /* --- @start@ --- * |
708 | * |
709 | * Arguments: @bres_server *rs@ = pointer to a server block |
710 | * |
711 | * Returns: Zero if OK, nonzero if something failed. |
712 | * |
713 | * Use: Starts up a child resolver process. |
714 | */ |
715 | |
716 | static int start(bres_server *rs) |
717 | { |
718 | int rfd[2], cfd[2]; |
719 | pid_t kid; |
720 | |
721 | /* --- Make the pipes --- */ |
722 | |
723 | if (pipe(rfd)) |
724 | goto fail_0; |
725 | if (pipe(cfd)) |
726 | goto fail_1; |
727 | |
728 | /* --- Start up the child process --- */ |
729 | |
730 | if ((kid = fork()) < 0) |
731 | goto fail_2; |
732 | if (kid == 0) { |
733 | close(cfd[1]); |
734 | close(rfd[0]); |
735 | |
736 | if (server) { |
737 | dup2(cfd[0], STDIN_FILENO); |
738 | dup2(rfd[1], STDOUT_FILENO); |
739 | close(cfd[0]); |
740 | close(rfd[1]); |
741 | execlp(server, server, (char *)0); |
742 | child(STDOUT_FILENO, STDIN_FILENO); |
743 | } else |
744 | child(rfd[1], cfd[0]); |
745 | _exit(1); |
746 | } |
747 | |
748 | /* --- Fix up everything in the server block --- */ |
749 | |
750 | close(cfd[0]); |
751 | close(rfd[1]); |
752 | rs->fd = cfd[1]; |
753 | sel_initfile(sel, &rs->f, rfd[0], SEL_READ, answer, rs); |
754 | rs->kid = kid; |
755 | return (0); |
756 | |
757 | /* --- Fix up after errors --- */ |
758 | |
759 | fail_2: |
760 | close(cfd[0]); |
761 | close(cfd[1]); |
762 | fail_1: |
763 | close(rfd[0]); |
764 | close(rfd[1]); |
765 | fail_0: |
766 | return (-1); |
767 | } |
768 | |
769 | /* --- @attach@ --- * |
770 | * |
771 | * Arguments: @bres_client *rc@ = pointer to a client block |
772 | * |
773 | * Returns: --- |
774 | * |
775 | * Use: Attaches a client to a spare server (which is assumed to |
776 | * exist). |
777 | */ |
778 | |
779 | static void attach(bres_client *rc) |
780 | { |
781 | bres_server *rs; |
782 | int lose = 0; |
783 | |
784 | /* --- Fix up the server ready for the job --- * |
785 | * |
786 | * If the server has a process, remove its timer. Otherwise, fork off a |
787 | * new resolver process. This is also where I go if I find that the child |
788 | * resolver process has lost while I wasn't looking. Only one attempt at |
789 | * forking is performed. |
790 | */ |
791 | |
792 | again: |
793 | rs = FREE->next; |
794 | if (rs->kid != -1) |
795 | sel_rmtimer(&rs->t); |
796 | else { |
797 | if (lose || start(rs)) |
798 | goto lost; |
799 | lose = 1; |
800 | } |
801 | |
802 | /* --- Submit the job to the resolver --- */ |
803 | |
804 | { |
805 | struct sigaction sa, osa; |
806 | int e; |
807 | |
808 | /* --- Ignore @SIGPIPE@ for now --- * |
809 | * |
810 | * This way I can trap @EPIPE@ and reap a losing child, if there was one. |
811 | */ |
812 | |
813 | sa.sa_handler = SIG_IGN; |
814 | sa.sa_flags = 0; |
815 | sigemptyset(&sa.sa_mask); |
816 | sigaction(SIGPIPE, &sa, &osa); |
817 | |
818 | /* --- Write the new job to the child --- */ |
819 | |
820 | e = 0; |
821 | if (dowrite(rs->fd, &rc->q, sizeof(rc->q))) |
822 | e = errno; |
823 | else switch (rc->q) { |
824 | case BRES_BYADDR: |
825 | if (dowrite(rs->fd, &rc->u.addr, sizeof(rc->u.addr))) |
826 | e = errno; |
827 | break; |
828 | case BRES_BYNAME: |
829 | if (putstring(rs->fd, rc->u.name)) |
830 | e = errno; |
831 | break; |
832 | } |
833 | sigaction(SIGPIPE, &osa, 0); |
834 | |
835 | /* --- Sort out various errors --- * |
836 | * |
837 | * This was once more complicated, handling @EPIPE@ separately from other |
838 | * errors. Now everything's handled the same way. |
839 | */ |
840 | |
841 | if (e) { |
842 | zap(rs); |
843 | goto again; |
844 | } |
845 | } |
846 | |
847 | /* --- Fiddle with lists so that everything's OK --- */ |
848 | |
849 | sel_addfile(&rs->f); |
850 | rs->next->prev = FREE; |
851 | FREE->next = rs->next; |
852 | rs->next = rs->prev = rs; |
853 | rs->rc = rc; |
854 | rc->rs = rs; |
855 | return; |
856 | |
857 | lost: |
858 | rc->func(0, rc->p); |
859 | if (rc->q == BRES_BYNAME) |
e2a18bd0 |
860 | xfree(rc->u.name); |
a759efa6 |
861 | } |
862 | |
863 | /* --- @resolve@ --- * |
864 | * |
865 | * Arguments: @bres_client *rc@ = pointer to filled-in client block |
866 | * |
867 | * Returns: --- |
868 | * |
869 | * Use: Dispatcher for incoming resolution jobs. |
870 | */ |
871 | |
872 | static void resolve(bres_client *rc) |
873 | { |
874 | /* --- If there's a free server, plug it in --- */ |
875 | |
876 | rc->rs = 0; |
877 | if (FREE->next == FREE) { |
878 | rc->next = QUEUE; |
879 | rc->prev = QUEUE->prev; |
880 | QUEUE->prev->next = rc; |
881 | QUEUE->prev = rc; |
882 | } else |
883 | attach(rc); |
884 | } |
885 | |
886 | /* --- @bres_byaddr@ --- * |
887 | * |
888 | * Arguments: @bres_client *rc@ = pointer to client block |
889 | * @struct in_addr addr@ = address to resolve |
890 | * @void (*func)(struct hostent *h, void *p)@ = handler function |
891 | * @void *p@ = argument for handler function |
892 | * |
893 | * Returns: --- |
894 | * |
895 | * Use: Adds an address lookup job to the queue. The job will be |
896 | * processed when there's a spare resolver process to deal with |
897 | * it. |
898 | */ |
899 | |
900 | void bres_byaddr(bres_client *rc, struct in_addr addr, |
901 | void (*func)(struct hostent */*h*/, void */*p*/), |
902 | void *p) |
903 | { |
904 | rc->q = BRES_BYADDR; |
905 | rc->u.addr = addr; |
906 | rc->func = func; |
907 | rc->p = p; |
908 | resolve(rc); |
909 | } |
910 | |
911 | /* --- @bres_byname@ --- * |
912 | * |
913 | * Arguments: @bres_client *rc@ = pointer to client block |
914 | * @const char *name@ = name to resolve |
915 | * @void (*func)(struct hostent *h, void *p)@ = handler function |
916 | * @void *p@ = argument for handler function |
917 | * |
918 | * Returns: --- |
919 | * |
920 | * Use: Adds a name lookup job to the queue. The job will be |
921 | * processed when there's a spare resolver process to deal with |
922 | * it. |
923 | */ |
924 | |
925 | void bres_byname(bres_client *rc, const char *name, |
926 | void (*func)(struct hostent */*h*/, void */*p*/), |
927 | void *p) |
928 | { |
929 | rc->q = BRES_BYNAME; |
930 | rc->u.name = xstrdup(name); |
931 | rc->func = func; |
932 | rc->p = p; |
933 | resolve(rc); |
934 | } |
935 | |
936 | /* --- @bres_exec@ --- * |
937 | * |
938 | * Arguments: @const char *file@ = file containing server code or null |
939 | * |
940 | * Returns: --- |
941 | * |
942 | * Use: Makes `bres' use a standalone server rather than copies of |
943 | * the current process. This can reduce memory consumption for |
944 | * large processes, at the expense of startup time (which |
945 | * shouldn't be too bad anyway, because of the resolver design). |
946 | * If the filename is null, a default set up at install time is |
947 | * used. It's probably a good idea to leave it alone. |
948 | */ |
949 | |
950 | void bres_exec(const char *file) |
951 | { |
952 | if (file) |
953 | server = file; |
954 | else |
955 | server = BRES_SERVER; |
956 | } |
957 | |
958 | /* --- @bres_init@ --- * |
959 | * |
960 | * Arguments: @sel_state *s@ = pointer to select multiplexor |
961 | * |
962 | * Returns: --- |
963 | * |
964 | * Use: Initializes the background resolver for use. |
965 | */ |
966 | |
967 | void bres_init(sel_state *s) |
968 | { |
969 | int i; |
970 | |
971 | sel = s; |
972 | for (i = 0; i < BRES_MAX; i++) { |
973 | servers[i].next = FREE; |
974 | servers[i].prev = FREE->prev; |
975 | servers[i].kid = -1; |
976 | servers[i].rc = 0; |
977 | FREE->prev->next = &servers[i]; |
978 | FREE->prev = &servers[i]; |
979 | } |
980 | } |
981 | |
982 | #endif |
983 | |
984 | /*----- That's all, folks -------------------------------------------------*/ |