a759efa6 |
1 | /* -*-c-*- |
2 | * |
8656dc50 |
3 | * $Id: bres.c,v 1.7 2004/04/08 01:36:11 mdw Exp $ |
a759efa6 |
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 | |
a759efa6 |
30 | /*----- Header files ------------------------------------------------------*/ |
31 | |
32 | #include <errno.h> |
33 | #include <signal.h> |
34 | #include <stdio.h> |
35 | #include <stdlib.h> |
36 | #include <string.h> |
37 | |
38 | #include <sys/types.h> |
39 | #include <sys/time.h> |
40 | #include <unistd.h> |
41 | #include <sys/wait.h> |
42 | |
43 | #include <sys/socket.h> |
44 | #include <netinet/in.h> |
45 | #include <arpa/inet.h> |
46 | #include <netdb.h> |
47 | |
6c3a7cf7 |
48 | #include "alloc.h" |
a759efa6 |
49 | #include "bres.h" |
6c3a7cf7 |
50 | #include "report.h" |
51 | #include "sel.h" |
a759efa6 |
52 | |
53 | /*----- Magic numbers -----------------------------------------------------*/ |
54 | |
55 | #define BRES_MAX 15 /* Maximum number of resolvers */ |
56 | #define BRES_IDLE 60 /* Lifetime of an idle resolver */ |
57 | |
58 | /*----- Static variables --------------------------------------------------*/ |
59 | |
60 | #ifndef BRES_STANDALONE |
61 | |
62 | static bres_server servers[BRES_MAX]; /* Statically allocated servers */ |
63 | |
64 | #define FREE ((bres_server *)&freelist) |
65 | static struct { bres_server *next, *prev; } freelist = { FREE, FREE }; |
66 | |
67 | #define QUEUE ((bres_client *)&queue) |
68 | static struct { bres_client *next, *prev; } queue = { QUEUE, QUEUE }; |
69 | |
70 | static sel_state *sel; |
71 | |
72 | static const char *server = 0; |
73 | |
74 | #endif |
75 | |
76 | /*----- Background resolver protocol --------------------------------------*/ |
77 | |
78 | /* --- Requests and responses --- * |
79 | * |
80 | * There are two types of requests: name and addr, corresponding to the |
81 | * standard @gethostbyname@ and @gethostbyaddr@ calls. There are two types |
82 | * of responses too: a positive response consists of an encoded equivalent of |
83 | * a @struct hostent@ structure containing the requested information; a |
84 | * negative response consists of an @h_errno@ value explaining the problem. |
85 | */ |
86 | |
87 | #define BRES_BYNAME 0 /* Request: resolve given name */ |
88 | #define BRES_BYADDR 1 /* Request: resolve given address */ |
89 | |
90 | #define BRES_HOSTENT 0 /* Response: resolved ok */ |
91 | #define BRES_ERROR 1 /* Response: resolution failed */ |
92 | |
93 | /* --- Encodings --- * |
94 | * |
95 | * A string is encoded as a @size_t@ length followed by the actual data. The |
96 | * null terminator is not transmitted. |
97 | * |
98 | * Addresses for resolution are transmitted as raw @struct in_addr@ |
99 | * structures. |
100 | * |
101 | * A @hostent@ structure is transmitted as a header containing fixed-size |
102 | * information, followed by the official name, an array of aliases, and an |
103 | * array of addresses. The number of items in the arrays is specified in the |
104 | * header. |
105 | * |
106 | * The implementation assumes that a complete request or reply is always |
107 | * sent. Undesirable blocking will occur if this is not the case. Both ends |
108 | * are assumed to trust each other. A protocol failure results in the child |
109 | * in question being terminated. |
110 | */ |
111 | |
112 | typedef struct hostskel { |
113 | size_t nalias; |
114 | int addrtype; |
115 | size_t addrsz; |
116 | size_t naddr; |
117 | } hostskel; |
118 | |
119 | /* --- @doread@, @dowrite@ --- * |
120 | * |
121 | * Arguments: @int fd@ = file descriptor |
122 | * @void *buf@ = buffer for data |
123 | * @size_t sz@ = size of data |
124 | * |
125 | * Returns: Zero if successful, nonzero otherwise. |
126 | * |
127 | * Use: Reads or writes a chunk of data. @EINTR@ errors are retried; |
128 | * incomplete reads and writes are continued from where they |
129 | * left off. End-of-file is considered an I/O error. |
130 | */ |
131 | |
132 | static int doread(int fd, void *buf, size_t sz) |
133 | { |
134 | char *p = buf; |
135 | while (sz) { |
136 | int r = read(fd, p, sz); |
137 | if (r < 0) { |
138 | if (errno == EINTR) |
139 | continue; |
140 | return (-1); |
141 | } else if (r == 0) { |
142 | errno = EIO; |
143 | return (-1); |
144 | } |
145 | sz -= r; |
146 | p += r; |
147 | } |
148 | return (0); |
149 | } |
150 | |
151 | static int dowrite(int fd, const void *buf, size_t sz) |
152 | { |
153 | const char *p = buf; |
154 | while (sz) { |
155 | int r = write(fd, p, sz); |
156 | if (r < 0) { |
157 | if (errno == EINTR) |
158 | continue; |
159 | return (-1); |
160 | } else if (r == 0) { |
161 | errno = EIO; |
162 | return (-1); |
163 | } |
164 | sz -= r; |
165 | p += r; |
166 | } |
167 | return (0); |
168 | } |
169 | |
170 | /* --- @getstring@ --- * |
171 | * |
172 | * Arguments: @int fd@ = file descriptor to read |
173 | * |
174 | * Returns: String in heap-allocated block, or a null pointer. |
175 | * |
176 | * Use: Decodes a string. |
177 | */ |
178 | |
179 | static char *getstring(int fd) |
180 | { |
181 | size_t sz; |
182 | char *p; |
183 | |
184 | if (doread(fd, &sz, sizeof(sz)) || (p = malloc(sz + 1)) == 0) |
185 | return (0); |
186 | if (doread(fd, p, sz)) { |
187 | free(p); |
188 | return (0); |
189 | } |
190 | p[sz] = 0; |
191 | return (p); |
192 | } |
193 | |
194 | /* --- @putstring@ --- * |
195 | * |
196 | * Arguments: @int fd@ = file descriptor to write on |
197 | * @const char *p@ = pointer to string to write |
198 | * |
199 | * Returns: Zero if successful. |
200 | * |
201 | * Use: Encodes a string. |
202 | */ |
203 | |
204 | static int putstring(int fd, const char *p) |
205 | { |
206 | size_t sz = strlen(p); |
207 | if (dowrite(fd, &sz, sizeof(sz)) || dowrite(fd, p, sz)) |
208 | return (-1); |
209 | return (0); |
210 | } |
211 | |
212 | /* --- @gethost@ --- * |
213 | * |
214 | * Arguments: @int fd@ = file descriptor to read |
215 | * |
216 | * Returns: Pointer to heap-allocated @struct hostent@, or null. |
217 | * |
218 | * Use: Decodes a host structure. The resulting structure is all in |
219 | * one big heap block. |
220 | */ |
221 | |
222 | #ifndef BRES_STANDALONE |
223 | |
224 | static struct hostent *gethost(int fd) |
225 | { |
226 | hostskel hsk; |
227 | struct hostent *h; |
228 | char *name; |
229 | char **alias = 0; |
230 | |
231 | /* --- Read the skeleton structure --- */ |
232 | |
233 | if (doread(fd, &hsk, sizeof(hsk))) |
234 | goto tidy_0; |
235 | |
236 | /* --- Read the hostname and alias strings --- * |
237 | * |
238 | * Count the length of the strings as we go. |
239 | */ |
240 | |
241 | { |
242 | size_t sz = |
243 | sizeof(struct hostent) + |
244 | hsk.naddr * hsk.addrsz + |
245 | (hsk.naddr + hsk.nalias + 2) * sizeof(char *); |
246 | |
247 | /* --- Read the primary host name --- */ |
248 | |
249 | if ((name = getstring(fd)) == 0) |
250 | goto tidy_0; |
251 | sz += strlen(name) + 1; |
252 | |
253 | /* --- Read in the alias names --- */ |
254 | |
255 | if (hsk.nalias) { |
256 | int i; |
257 | if ((alias = malloc(hsk.nalias * sizeof(char *))) == 0) |
258 | goto tidy_1; |
259 | for (i = 0; i < hsk.nalias; i++) |
260 | alias[i] = 0; |
261 | for (i = 0; i < hsk.nalias; i++) { |
262 | if ((alias[i] = getstring(fd)) == 0) |
263 | goto tidy_2; |
264 | sz += strlen(alias[i]) + 1; |
265 | } |
266 | } |
267 | |
268 | /* --- Allocate the output structure --- */ |
269 | |
270 | if ((h = malloc(sz)) == 0) |
271 | goto tidy_2; |
272 | } |
273 | |
274 | /* --- Fill in the base structure --- */ |
275 | |
276 | h->h_addrtype = hsk.addrtype; |
277 | h->h_length = hsk.addrsz; |
278 | |
279 | /* --- Start putting everything else in --- */ |
280 | |
281 | { |
282 | char **p = (char **)(h + 1); |
283 | char *a = (char *)(p + hsk.nalias + hsk.naddr + 2); |
284 | int i; |
285 | |
286 | /* --- Start with the address table --- */ |
287 | |
288 | h->h_addr_list = p; |
289 | if (doread(fd, a, hsk.naddr * hsk.addrsz)) |
290 | goto tidy_2; |
291 | for (i = 0; i < hsk.naddr; i++) { |
a759efa6 |
292 | *p++ = a; |
364308dc |
293 | a += hsk.addrsz; |
a759efa6 |
294 | } |
295 | *p++ = 0; |
296 | |
297 | /* --- Finally copy the strings over --- */ |
298 | |
299 | #define PUT(_p) do { \ |
300 | size_t _len = strlen(_p) + 1; \ |
301 | memcpy(a, (_p), _len); \ |
302 | a += _len; \ |
303 | } while (0) |
304 | |
305 | h->h_name = a; |
306 | PUT(name); |
d8fe3fc2 |
307 | free(name); |
a759efa6 |
308 | h->h_aliases = p; |
309 | for (i = 0; i < hsk.nalias; i++) { |
310 | *p++ = a; |
311 | PUT(alias[i]); |
d8fe3fc2 |
312 | free(alias[i]); |
a759efa6 |
313 | } |
314 | *p++ = 0; |
d8fe3fc2 |
315 | free(alias); |
a759efa6 |
316 | |
317 | #undef PUT |
318 | } |
319 | |
320 | return (h); |
321 | |
322 | /* --- Tidy up after various types of failure --- */ |
323 | |
324 | tidy_2: |
325 | { |
326 | int i; |
327 | for (i = 0; i < hsk.nalias && alias[i]; i++) |
d8fe3fc2 |
328 | free(alias[i]); |
329 | free(alias); |
a759efa6 |
330 | } |
331 | tidy_1: |
d8fe3fc2 |
332 | free(name); |
a759efa6 |
333 | tidy_0: |
334 | return (0); |
335 | } |
336 | |
337 | #endif |
338 | |
339 | /* --- @puthost@ --- * |
340 | * |
341 | * Arguments: @int fd@ = file descriptor |
342 | * @struct hostent *h@ = pointer to host structure |
343 | * |
344 | * Returns: Zero if successful. |
345 | * |
346 | * Use: Encodes a host structure. |
347 | */ |
348 | |
349 | static int puthost(int fd, struct hostent *h) |
350 | { |
351 | hostskel hsk; |
352 | int i; |
353 | |
354 | /* --- Fill in and send the skeleton structure --- */ |
355 | |
356 | for (i = 0; h->h_aliases[i]; i++) |
357 | ; |
358 | hsk.nalias = i; |
359 | for (i = 0; h->h_addr_list[i]; i++) |
360 | ; |
361 | hsk.naddr = i; |
362 | hsk.addrtype = h->h_addrtype; |
363 | hsk.addrsz = h->h_length; |
364 | if (dowrite(fd, &hsk, sizeof(hsk))) |
365 | return (-1); |
366 | |
367 | /* --- Send the name and alias strings --- */ |
368 | |
369 | if (putstring(fd, h->h_name)) |
370 | return (-1); |
371 | for (i = 0; h->h_aliases[i]; i++) { |
372 | if (putstring(fd, h->h_aliases[i])) |
373 | return (-1); |
374 | } |
375 | |
376 | /* --- Send the address data --- */ |
377 | |
378 | for (i = 0; h->h_addr_list[i]; i++) { |
379 | if (dowrite(fd, h->h_addr_list[i], hsk.addrsz)) |
380 | return (-1); |
381 | } |
382 | |
383 | /* --- OK, done --- */ |
384 | |
385 | return (0); |
386 | } |
387 | |
388 | /*----- Resolver server ---------------------------------------------------*/ |
389 | |
390 | /* --- @child@ --- * |
391 | * |
392 | * Arguments: @int rfd@ = output file descriptor for resolved hostnames |
393 | * @int cfd@ = input file descriptor for raw addresses |
394 | * |
395 | * Returns: Never. |
396 | * |
397 | * Use: Asynchronous name resolving process. |
398 | */ |
399 | |
400 | static void child(int rfd, int cfd) |
401 | { |
402 | /* --- Close other file descriptors --- */ |
403 | |
404 | { |
405 | int i; |
5d6d2d94 |
406 | #if defined(_SC_OPEN_MAX) |
a759efa6 |
407 | int maxfd = sysconf(_SC_OPEN_MAX); |
5d6d2d94 |
408 | #elif defined(OPEN_MAX) |
409 | int maxfd = OPEN_MAX; |
410 | #else |
411 | int maxfd = -1; |
412 | #endif |
a759efa6 |
413 | |
414 | if (maxfd < 0) |
415 | maxfd = 256; /* Fingers crossed... */ |
416 | for (i = 0; i < maxfd; i++) { |
417 | if (i != rfd && i != cfd && i != 1) |
418 | close(i); |
419 | } |
420 | } |
421 | |
364308dc |
422 | signal(SIGTERM, SIG_DFL); |
423 | signal(SIGHUP, SIG_DFL); |
424 | signal(SIGQUIT, SIG_DFL); |
425 | signal(SIGALRM, SIG_DFL); |
426 | signal(SIGINT, SIG_DFL); |
427 | |
a759efa6 |
428 | /* --- Main request/response loop --- */ |
429 | |
430 | for (;;) { |
431 | int req, resp; |
432 | struct hostent *h; |
433 | |
434 | /* --- Read the request --- */ |
435 | |
436 | if (doread(cfd, &req, sizeof(req))) |
437 | goto lose; |
438 | |
439 | /* --- Process it into a host structure --- */ |
440 | |
441 | switch (req) { |
442 | |
443 | /* --- Normal forward lookup --- */ |
444 | |
445 | case BRES_BYNAME: { |
446 | char *name = getstring(cfd); |
447 | if (!name) |
448 | goto lose; |
449 | h = gethostbyname(name); |
450 | free(name); |
451 | } break; |
452 | |
d8fe3fc2 |
453 | /* --- Reverse lookup --- */ |
a759efa6 |
454 | |
455 | case BRES_BYADDR: { |
456 | struct in_addr addr; |
457 | char *p; |
458 | if (doread(cfd, &addr, sizeof(addr))) |
459 | goto lose; |
460 | if ((h = gethostbyaddr((char *)&addr, sizeof(addr), AF_INET)) == 0) |
461 | goto fail; |
462 | |
463 | /* --- Do a forward lookup to confirm --- */ |
464 | |
465 | { |
466 | size_t sz = strlen(h->h_name) + 1; |
467 | if ((p = malloc(sz)) == 0) |
468 | goto fail; |
469 | memcpy(p, h->h_name, sz); |
470 | } |
471 | |
472 | h = gethostbyname(p); |
473 | free(p); |
474 | if (!h) |
475 | goto fail; |
476 | p = 0; |
477 | if (h) { |
478 | char **pp; |
479 | for (pp = h->h_addr_list; *pp; pp++) { |
480 | struct in_addr a; |
481 | memcpy(&a, *pp, sizeof(a)); |
482 | if (a.s_addr == addr.s_addr) { |
483 | p = h->h_name; |
484 | break; |
485 | } |
486 | } |
487 | } |
488 | if (!p) { |
489 | h = 0; |
490 | h_errno = NO_RECOVERY; |
491 | } |
492 | fail:; |
493 | } break; |
494 | |
495 | /* --- Unknown request -- may have lost sync --- */ |
496 | |
497 | default: |
498 | goto lose; |
499 | } |
500 | |
501 | /* --- Transmit the response --- */ |
502 | |
503 | if (h) { |
504 | resp = BRES_HOSTENT; |
505 | if (dowrite(rfd, &resp, sizeof(resp)) || puthost(rfd, h)) |
506 | goto lose; |
507 | } else { |
508 | resp = BRES_ERROR; |
509 | if (dowrite(rfd, &resp, sizeof(resp)) || |
510 | dowrite(rfd, &h_errno, sizeof(h_errno))) |
511 | goto lose; |
512 | } |
513 | } |
514 | |
515 | lose: |
516 | _exit(1); |
517 | } |
518 | |
519 | /* --- @main@ --- * |
520 | * |
521 | * Arguments: @int argc@ = number of command line arguments |
522 | * @char *argv[]@ = array of arguments |
523 | * |
524 | * Returns: Runs until killed or an error occurs. |
525 | * |
526 | * Use: A name resolver server process for mLib programs which need |
527 | * this sort of thing. |
528 | */ |
529 | |
530 | #ifdef BRES_STANDALONE |
531 | |
532 | int main(int argc, char *argv[]) |
533 | { |
534 | if (isatty(STDIN_FILENO)) { |
535 | char *p = strrchr(argv[0], '/'); |
536 | if (p) |
537 | p++; |
538 | else |
539 | p = argv[0]; |
540 | fprintf(stderr, |
541 | "%s: don't run this program unless you know what you're doing.\n", |
542 | p); |
543 | exit(1); |
544 | } |
545 | child(STDOUT_FILENO, STDIN_FILENO); |
546 | return (1); |
547 | } |
548 | |
549 | #endif |
550 | |
551 | /*----- Main code ---------------------------------------------------------*/ |
552 | |
553 | #ifndef BRES_STANDALONE |
554 | |
555 | /* --- @zap@ --- * |
556 | * |
557 | * Arguments: @bres_server *rs@ = pointer to server block |
558 | * |
559 | * Returns: --- |
560 | * |
561 | * Use: Kills a server process, reaps the losing child and makes |
562 | * things generally clean again. |
563 | */ |
564 | |
565 | static void zap(bres_server *rs) |
566 | { |
567 | /* --- Close the pipes, kill the child, and reap it --- */ |
568 | |
569 | if (rs->kid != -1) { |
570 | close(rs->fd); |
571 | close(rs->f.fd); |
572 | kill(rs->kid, SIGTERM); |
573 | waitpid(rs->kid, 0, 0); |
574 | rs->kid = -1; |
575 | } |
576 | |
577 | /* --- Move the server to the back of the list --- */ |
578 | |
579 | rs->next->prev = rs->prev; |
580 | rs->prev->next = rs->next; |
581 | rs->next = FREE; |
582 | rs->prev = FREE->prev; |
583 | FREE->prev->next = rs; |
584 | FREE->prev = rs; |
585 | } |
586 | |
587 | /* --- @bres_abort@ --- * |
588 | * |
589 | * Arguments: @bres_client *rc@ = pointer to client block |
590 | * |
591 | * Returns: --- |
592 | * |
593 | * Use: Removes a queued job. |
594 | */ |
595 | |
596 | void bres_abort(bres_client *rc) |
597 | { |
598 | if (rc->q == BRES_BYNAME) |
e2a18bd0 |
599 | xfree(rc->u.name); |
a759efa6 |
600 | if (rc->rs) { |
601 | sel_rmfile(&rc->rs->f); |
602 | zap(rc->rs); |
603 | rc->rs = 0; |
604 | } else { |
605 | rc->next->prev = rc->prev; |
606 | rc->prev->next = rc->next; |
607 | } |
608 | } |
609 | |
610 | /* --- @idle@ --- * |
611 | * |
612 | * Arguments: @struct timeval *tv@ = pointer to the current time |
613 | * @void *vp@ = pointer to a server block |
614 | * |
615 | * Returns: --- |
616 | * |
617 | * Use: Kills off a child which has been idle for too long. |
618 | */ |
619 | |
620 | static void idle(struct timeval *tv, void *vp) |
621 | { |
622 | bres_server *rs = vp; |
623 | zap(rs); |
624 | } |
625 | |
626 | /* --- @answer@ --- * |
627 | * |
628 | * Arguments: @int fd@ = file descriptor which is ready |
629 | * @unsigned mode@ = what it's doing now |
630 | * @void *vp@ = pointer to server block |
631 | * |
632 | * Returns: --- |
633 | * |
634 | * Use: Retrieves an answer from a name resolver process. |
635 | */ |
636 | |
637 | static void attach(bres_client */*rc*/); |
638 | |
639 | static void answer(int fd, unsigned mode, void *vp) |
640 | { |
641 | bres_server *rs = vp; |
642 | bres_client *rc = rs->rc; |
643 | struct hostent *h = 0; |
644 | int resp; |
645 | int fail = 1; |
646 | |
647 | /* --- Report the result to my client --- */ |
648 | |
649 | sel_rmfile(&rs->f); |
650 | h_errno = -1; |
651 | if (doread(fd, &resp, sizeof(resp)) == 0) { |
652 | switch (resp) { |
653 | case BRES_ERROR: |
654 | doread(fd, &h_errno, sizeof(h_errno)); |
655 | fail = 0; |
656 | break; |
657 | case BRES_HOSTENT: |
658 | h = gethost(fd); |
659 | fail = 0; |
660 | break; |
661 | } |
662 | } |
663 | if (rc) { |
664 | rc->func(h, rc->p); |
665 | if (rc->q == BRES_BYNAME) |
e2a18bd0 |
666 | xfree(rc->u.name); |
a759efa6 |
667 | } |
668 | if (h) |
d8fe3fc2 |
669 | free(h); |
a759efa6 |
670 | if (fail) |
671 | zap(rs); |
672 | if (!rc) |
673 | return; |
674 | |
675 | /* --- Wrap up the various structures --- */ |
676 | |
677 | rs->rc = 0; |
678 | rc->rs = 0; |
679 | rs->next = FREE->next; |
680 | rs->prev = FREE; |
681 | FREE->next->prev = rs; |
682 | FREE->next = rs; |
683 | |
684 | /* --- Tie a timer onto the server block --- */ |
685 | |
686 | { |
687 | struct timeval tv; |
688 | |
689 | gettimeofday(&tv, 0); |
690 | tv.tv_sec += BRES_IDLE; |
691 | sel_addtimer(sel, &rs->t, &tv, idle, rs); |
692 | } |
693 | |
694 | /* --- If there are any clients waiting, attach one --- */ |
695 | |
696 | if (QUEUE->next != QUEUE) { |
697 | rc = QUEUE->next; |
698 | QUEUE->next = rc->next; |
699 | rc->next->prev = QUEUE; |
700 | attach(rc); |
701 | } |
702 | } |
703 | |
704 | /* --- @start@ --- * |
705 | * |
706 | * Arguments: @bres_server *rs@ = pointer to a server block |
707 | * |
708 | * Returns: Zero if OK, nonzero if something failed. |
709 | * |
710 | * Use: Starts up a child resolver process. |
711 | */ |
712 | |
713 | static int start(bres_server *rs) |
714 | { |
715 | int rfd[2], cfd[2]; |
716 | pid_t kid; |
717 | |
718 | /* --- Make the pipes --- */ |
719 | |
720 | if (pipe(rfd)) |
721 | goto fail_0; |
722 | if (pipe(cfd)) |
723 | goto fail_1; |
724 | |
725 | /* --- Start up the child process --- */ |
726 | |
727 | if ((kid = fork()) < 0) |
728 | goto fail_2; |
729 | if (kid == 0) { |
730 | close(cfd[1]); |
731 | close(rfd[0]); |
732 | |
733 | if (server) { |
734 | dup2(cfd[0], STDIN_FILENO); |
735 | dup2(rfd[1], STDOUT_FILENO); |
736 | close(cfd[0]); |
737 | close(rfd[1]); |
738 | execlp(server, server, (char *)0); |
739 | child(STDOUT_FILENO, STDIN_FILENO); |
740 | } else |
741 | child(rfd[1], cfd[0]); |
742 | _exit(1); |
743 | } |
744 | |
745 | /* --- Fix up everything in the server block --- */ |
746 | |
747 | close(cfd[0]); |
748 | close(rfd[1]); |
749 | rs->fd = cfd[1]; |
750 | sel_initfile(sel, &rs->f, rfd[0], SEL_READ, answer, rs); |
751 | rs->kid = kid; |
752 | return (0); |
753 | |
754 | /* --- Fix up after errors --- */ |
755 | |
756 | fail_2: |
757 | close(cfd[0]); |
758 | close(cfd[1]); |
759 | fail_1: |
760 | close(rfd[0]); |
761 | close(rfd[1]); |
762 | fail_0: |
763 | return (-1); |
764 | } |
765 | |
766 | /* --- @attach@ --- * |
767 | * |
768 | * Arguments: @bres_client *rc@ = pointer to a client block |
769 | * |
770 | * Returns: --- |
771 | * |
772 | * Use: Attaches a client to a spare server (which is assumed to |
773 | * exist). |
774 | */ |
775 | |
776 | static void attach(bres_client *rc) |
777 | { |
778 | bres_server *rs; |
779 | int lose = 0; |
780 | |
781 | /* --- Fix up the server ready for the job --- * |
782 | * |
783 | * If the server has a process, remove its timer. Otherwise, fork off a |
784 | * new resolver process. This is also where I go if I find that the child |
785 | * resolver process has lost while I wasn't looking. Only one attempt at |
786 | * forking is performed. |
787 | */ |
788 | |
789 | again: |
790 | rs = FREE->next; |
791 | if (rs->kid != -1) |
792 | sel_rmtimer(&rs->t); |
793 | else { |
794 | if (lose || start(rs)) |
795 | goto lost; |
796 | lose = 1; |
797 | } |
798 | |
799 | /* --- Submit the job to the resolver --- */ |
800 | |
801 | { |
802 | struct sigaction sa, osa; |
803 | int e; |
804 | |
805 | /* --- Ignore @SIGPIPE@ for now --- * |
806 | * |
807 | * This way I can trap @EPIPE@ and reap a losing child, if there was one. |
808 | */ |
809 | |
810 | sa.sa_handler = SIG_IGN; |
811 | sa.sa_flags = 0; |
812 | sigemptyset(&sa.sa_mask); |
813 | sigaction(SIGPIPE, &sa, &osa); |
814 | |
815 | /* --- Write the new job to the child --- */ |
816 | |
817 | e = 0; |
818 | if (dowrite(rs->fd, &rc->q, sizeof(rc->q))) |
819 | e = errno; |
820 | else switch (rc->q) { |
821 | case BRES_BYADDR: |
822 | if (dowrite(rs->fd, &rc->u.addr, sizeof(rc->u.addr))) |
823 | e = errno; |
824 | break; |
825 | case BRES_BYNAME: |
826 | if (putstring(rs->fd, rc->u.name)) |
827 | e = errno; |
828 | break; |
829 | } |
830 | sigaction(SIGPIPE, &osa, 0); |
831 | |
832 | /* --- Sort out various errors --- * |
833 | * |
834 | * This was once more complicated, handling @EPIPE@ separately from other |
835 | * errors. Now everything's handled the same way. |
836 | */ |
837 | |
838 | if (e) { |
839 | zap(rs); |
840 | goto again; |
841 | } |
842 | } |
843 | |
844 | /* --- Fiddle with lists so that everything's OK --- */ |
845 | |
846 | sel_addfile(&rs->f); |
847 | rs->next->prev = FREE; |
848 | FREE->next = rs->next; |
849 | rs->next = rs->prev = rs; |
850 | rs->rc = rc; |
851 | rc->rs = rs; |
852 | return; |
853 | |
854 | lost: |
855 | rc->func(0, rc->p); |
856 | if (rc->q == BRES_BYNAME) |
e2a18bd0 |
857 | xfree(rc->u.name); |
a759efa6 |
858 | } |
859 | |
860 | /* --- @resolve@ --- * |
861 | * |
862 | * Arguments: @bres_client *rc@ = pointer to filled-in client block |
863 | * |
864 | * Returns: --- |
865 | * |
866 | * Use: Dispatcher for incoming resolution jobs. |
867 | */ |
868 | |
869 | static void resolve(bres_client *rc) |
870 | { |
871 | /* --- If there's a free server, plug it in --- */ |
872 | |
873 | rc->rs = 0; |
874 | if (FREE->next == FREE) { |
875 | rc->next = QUEUE; |
876 | rc->prev = QUEUE->prev; |
877 | QUEUE->prev->next = rc; |
878 | QUEUE->prev = rc; |
879 | } else |
880 | attach(rc); |
881 | } |
882 | |
883 | /* --- @bres_byaddr@ --- * |
884 | * |
885 | * Arguments: @bres_client *rc@ = pointer to client block |
886 | * @struct in_addr addr@ = address to resolve |
887 | * @void (*func)(struct hostent *h, void *p)@ = handler function |
888 | * @void *p@ = argument for handler function |
889 | * |
890 | * Returns: --- |
891 | * |
892 | * Use: Adds an address lookup job to the queue. The job will be |
893 | * processed when there's a spare resolver process to deal with |
894 | * it. |
895 | */ |
896 | |
897 | void bres_byaddr(bres_client *rc, struct in_addr addr, |
898 | void (*func)(struct hostent */*h*/, void */*p*/), |
899 | void *p) |
900 | { |
901 | rc->q = BRES_BYADDR; |
902 | rc->u.addr = addr; |
903 | rc->func = func; |
904 | rc->p = p; |
905 | resolve(rc); |
906 | } |
907 | |
908 | /* --- @bres_byname@ --- * |
909 | * |
910 | * Arguments: @bres_client *rc@ = pointer to client block |
911 | * @const char *name@ = name to resolve |
912 | * @void (*func)(struct hostent *h, void *p)@ = handler function |
913 | * @void *p@ = argument for handler function |
914 | * |
915 | * Returns: --- |
916 | * |
917 | * Use: Adds a name lookup job to the queue. The job will be |
918 | * processed when there's a spare resolver process to deal with |
919 | * it. |
920 | */ |
921 | |
922 | void bres_byname(bres_client *rc, const char *name, |
923 | void (*func)(struct hostent */*h*/, void */*p*/), |
924 | void *p) |
925 | { |
926 | rc->q = BRES_BYNAME; |
927 | rc->u.name = xstrdup(name); |
928 | rc->func = func; |
929 | rc->p = p; |
930 | resolve(rc); |
931 | } |
932 | |
933 | /* --- @bres_exec@ --- * |
934 | * |
935 | * Arguments: @const char *file@ = file containing server code or null |
936 | * |
937 | * Returns: --- |
938 | * |
939 | * Use: Makes `bres' use a standalone server rather than copies of |
940 | * the current process. This can reduce memory consumption for |
941 | * large processes, at the expense of startup time (which |
942 | * shouldn't be too bad anyway, because of the resolver design). |
943 | * If the filename is null, a default set up at install time is |
944 | * used. It's probably a good idea to leave it alone. |
945 | */ |
946 | |
947 | void bres_exec(const char *file) |
948 | { |
949 | if (file) |
950 | server = file; |
951 | else |
952 | server = BRES_SERVER; |
953 | } |
954 | |
955 | /* --- @bres_init@ --- * |
956 | * |
957 | * Arguments: @sel_state *s@ = pointer to select multiplexor |
958 | * |
959 | * Returns: --- |
960 | * |
961 | * Use: Initializes the background resolver for use. |
962 | */ |
963 | |
964 | void bres_init(sel_state *s) |
965 | { |
966 | int i; |
967 | |
968 | sel = s; |
969 | for (i = 0; i < BRES_MAX; i++) { |
970 | servers[i].next = FREE; |
971 | servers[i].prev = FREE->prev; |
972 | servers[i].kid = -1; |
973 | servers[i].rc = 0; |
974 | FREE->prev->next = &servers[i]; |
975 | FREE->prev = &servers[i]; |
976 | } |
977 | } |
978 | |
979 | #endif |
980 | |
981 | /*----- That's all, folks -------------------------------------------------*/ |