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