a759efa6 |
1 | /* -*-c-*- |
2 | * |
364308dc |
3 | * $Id: bres.c,v 1.5 2001/02/03 16:21:08 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 | |
30 | /*----- Revision history --------------------------------------------------* |
31 | * |
32 | * $Log: bres.c,v $ |
364308dc |
33 | * Revision 1.5 2001/02/03 16:21:08 mdw |
34 | * Bug fixes: restore signals to their default dispositions, and set up the |
35 | * addresses properly when unpacking @hostent@ structures. |
36 | * |
d8fe3fc2 |
37 | * Revision 1.4 2000/08/15 17:35:02 mdw |
38 | * (gethost, and others): Since @gethost@ actually uses @malloc@ rather |
39 | * than @xmalloc@, it's wrong to use @xfree@ on the result. Fixed the code |
40 | * to use the right freeing function on the right data. |
41 | * |
e2a18bd0 |
42 | * Revision 1.3 2000/06/17 10:38:35 mdw |
43 | * Track changes to selbuf interface. |
44 | * |
6c3a7cf7 |
45 | * Revision 1.2 1999/10/30 11:28:39 mdw |
46 | * Fix include error, pointed out by Chris Rutter. |
47 | * |
a759efa6 |
48 | * Revision 1.1 1999/10/04 21:40:42 mdw |
49 | * Added background resolver from `fw'. |
50 | * |
51 | */ |
52 | |
53 | /*----- Header files ------------------------------------------------------*/ |
54 | |
55 | #include <errno.h> |
56 | #include <signal.h> |
57 | #include <stdio.h> |
58 | #include <stdlib.h> |
59 | #include <string.h> |
60 | |
61 | #include <sys/types.h> |
62 | #include <sys/time.h> |
63 | #include <unistd.h> |
64 | #include <sys/wait.h> |
65 | |
66 | #include <sys/socket.h> |
67 | #include <netinet/in.h> |
68 | #include <arpa/inet.h> |
69 | #include <netdb.h> |
70 | |
6c3a7cf7 |
71 | #include "alloc.h" |
a759efa6 |
72 | #include "bres.h" |
6c3a7cf7 |
73 | #include "report.h" |
74 | #include "sel.h" |
a759efa6 |
75 | |
76 | /*----- Magic numbers -----------------------------------------------------*/ |
77 | |
78 | #define BRES_MAX 15 /* Maximum number of resolvers */ |
79 | #define BRES_IDLE 60 /* Lifetime of an idle resolver */ |
80 | |
81 | /*----- Static variables --------------------------------------------------*/ |
82 | |
83 | #ifndef BRES_STANDALONE |
84 | |
85 | static bres_server servers[BRES_MAX]; /* Statically allocated servers */ |
86 | |
87 | #define FREE ((bres_server *)&freelist) |
88 | static struct { bres_server *next, *prev; } freelist = { FREE, FREE }; |
89 | |
90 | #define QUEUE ((bres_client *)&queue) |
91 | static struct { bres_client *next, *prev; } queue = { QUEUE, QUEUE }; |
92 | |
93 | static sel_state *sel; |
94 | |
95 | static const char *server = 0; |
96 | |
97 | #endif |
98 | |
99 | /*----- Background resolver protocol --------------------------------------*/ |
100 | |
101 | /* --- Requests and responses --- * |
102 | * |
103 | * There are two types of requests: name and addr, corresponding to the |
104 | * standard @gethostbyname@ and @gethostbyaddr@ calls. There are two types |
105 | * of responses too: a positive response consists of an encoded equivalent of |
106 | * a @struct hostent@ structure containing the requested information; a |
107 | * negative response consists of an @h_errno@ value explaining the problem. |
108 | */ |
109 | |
110 | #define BRES_BYNAME 0 /* Request: resolve given name */ |
111 | #define BRES_BYADDR 1 /* Request: resolve given address */ |
112 | |
113 | #define BRES_HOSTENT 0 /* Response: resolved ok */ |
114 | #define BRES_ERROR 1 /* Response: resolution failed */ |
115 | |
116 | /* --- Encodings --- * |
117 | * |
118 | * A string is encoded as a @size_t@ length followed by the actual data. The |
119 | * null terminator is not transmitted. |
120 | * |
121 | * Addresses for resolution are transmitted as raw @struct in_addr@ |
122 | * structures. |
123 | * |
124 | * A @hostent@ structure is transmitted as a header containing fixed-size |
125 | * information, followed by the official name, an array of aliases, and an |
126 | * array of addresses. The number of items in the arrays is specified in the |
127 | * header. |
128 | * |
129 | * The implementation assumes that a complete request or reply is always |
130 | * sent. Undesirable blocking will occur if this is not the case. Both ends |
131 | * are assumed to trust each other. A protocol failure results in the child |
132 | * in question being terminated. |
133 | */ |
134 | |
135 | typedef struct hostskel { |
136 | size_t nalias; |
137 | int addrtype; |
138 | size_t addrsz; |
139 | size_t naddr; |
140 | } hostskel; |
141 | |
142 | /* --- @doread@, @dowrite@ --- * |
143 | * |
144 | * Arguments: @int fd@ = file descriptor |
145 | * @void *buf@ = buffer for data |
146 | * @size_t sz@ = size of data |
147 | * |
148 | * Returns: Zero if successful, nonzero otherwise. |
149 | * |
150 | * Use: Reads or writes a chunk of data. @EINTR@ errors are retried; |
151 | * incomplete reads and writes are continued from where they |
152 | * left off. End-of-file is considered an I/O error. |
153 | */ |
154 | |
155 | static int doread(int fd, void *buf, size_t sz) |
156 | { |
157 | char *p = buf; |
158 | while (sz) { |
159 | int r = read(fd, p, sz); |
160 | if (r < 0) { |
161 | if (errno == EINTR) |
162 | continue; |
163 | return (-1); |
164 | } else if (r == 0) { |
165 | errno = EIO; |
166 | return (-1); |
167 | } |
168 | sz -= r; |
169 | p += r; |
170 | } |
171 | return (0); |
172 | } |
173 | |
174 | static int dowrite(int fd, const void *buf, size_t sz) |
175 | { |
176 | const char *p = buf; |
177 | while (sz) { |
178 | int r = write(fd, p, sz); |
179 | if (r < 0) { |
180 | if (errno == EINTR) |
181 | continue; |
182 | return (-1); |
183 | } else if (r == 0) { |
184 | errno = EIO; |
185 | return (-1); |
186 | } |
187 | sz -= r; |
188 | p += r; |
189 | } |
190 | return (0); |
191 | } |
192 | |
193 | /* --- @getstring@ --- * |
194 | * |
195 | * Arguments: @int fd@ = file descriptor to read |
196 | * |
197 | * Returns: String in heap-allocated block, or a null pointer. |
198 | * |
199 | * Use: Decodes a string. |
200 | */ |
201 | |
202 | static char *getstring(int fd) |
203 | { |
204 | size_t sz; |
205 | char *p; |
206 | |
207 | if (doread(fd, &sz, sizeof(sz)) || (p = malloc(sz + 1)) == 0) |
208 | return (0); |
209 | if (doread(fd, p, sz)) { |
210 | free(p); |
211 | return (0); |
212 | } |
213 | p[sz] = 0; |
214 | return (p); |
215 | } |
216 | |
217 | /* --- @putstring@ --- * |
218 | * |
219 | * Arguments: @int fd@ = file descriptor to write on |
220 | * @const char *p@ = pointer to string to write |
221 | * |
222 | * Returns: Zero if successful. |
223 | * |
224 | * Use: Encodes a string. |
225 | */ |
226 | |
227 | static int putstring(int fd, const char *p) |
228 | { |
229 | size_t sz = strlen(p); |
230 | if (dowrite(fd, &sz, sizeof(sz)) || dowrite(fd, p, sz)) |
231 | return (-1); |
232 | return (0); |
233 | } |
234 | |
235 | /* --- @gethost@ --- * |
236 | * |
237 | * Arguments: @int fd@ = file descriptor to read |
238 | * |
239 | * Returns: Pointer to heap-allocated @struct hostent@, or null. |
240 | * |
241 | * Use: Decodes a host structure. The resulting structure is all in |
242 | * one big heap block. |
243 | */ |
244 | |
245 | #ifndef BRES_STANDALONE |
246 | |
247 | static struct hostent *gethost(int fd) |
248 | { |
249 | hostskel hsk; |
250 | struct hostent *h; |
251 | char *name; |
252 | char **alias = 0; |
253 | |
254 | /* --- Read the skeleton structure --- */ |
255 | |
256 | if (doread(fd, &hsk, sizeof(hsk))) |
257 | goto tidy_0; |
258 | |
259 | /* --- Read the hostname and alias strings --- * |
260 | * |
261 | * Count the length of the strings as we go. |
262 | */ |
263 | |
264 | { |
265 | size_t sz = |
266 | sizeof(struct hostent) + |
267 | hsk.naddr * hsk.addrsz + |
268 | (hsk.naddr + hsk.nalias + 2) * sizeof(char *); |
269 | |
270 | /* --- Read the primary host name --- */ |
271 | |
272 | if ((name = getstring(fd)) == 0) |
273 | goto tidy_0; |
274 | sz += strlen(name) + 1; |
275 | |
276 | /* --- Read in the alias names --- */ |
277 | |
278 | if (hsk.nalias) { |
279 | int i; |
280 | if ((alias = malloc(hsk.nalias * sizeof(char *))) == 0) |
281 | goto tidy_1; |
282 | for (i = 0; i < hsk.nalias; i++) |
283 | alias[i] = 0; |
284 | for (i = 0; i < hsk.nalias; i++) { |
285 | if ((alias[i] = getstring(fd)) == 0) |
286 | goto tidy_2; |
287 | sz += strlen(alias[i]) + 1; |
288 | } |
289 | } |
290 | |
291 | /* --- Allocate the output structure --- */ |
292 | |
293 | if ((h = malloc(sz)) == 0) |
294 | goto tidy_2; |
295 | } |
296 | |
297 | /* --- Fill in the base structure --- */ |
298 | |
299 | h->h_addrtype = hsk.addrtype; |
300 | h->h_length = hsk.addrsz; |
301 | |
302 | /* --- Start putting everything else in --- */ |
303 | |
304 | { |
305 | char **p = (char **)(h + 1); |
306 | char *a = (char *)(p + hsk.nalias + hsk.naddr + 2); |
307 | int i; |
308 | |
309 | /* --- Start with the address table --- */ |
310 | |
311 | h->h_addr_list = p; |
312 | if (doread(fd, a, hsk.naddr * hsk.addrsz)) |
313 | goto tidy_2; |
314 | for (i = 0; i < hsk.naddr; i++) { |
a759efa6 |
315 | *p++ = a; |
364308dc |
316 | a += hsk.addrsz; |
a759efa6 |
317 | } |
318 | *p++ = 0; |
319 | |
320 | /* --- Finally copy the strings over --- */ |
321 | |
322 | #define PUT(_p) do { \ |
323 | size_t _len = strlen(_p) + 1; \ |
324 | memcpy(a, (_p), _len); \ |
325 | a += _len; \ |
326 | } while (0) |
327 | |
328 | h->h_name = a; |
329 | PUT(name); |
d8fe3fc2 |
330 | free(name); |
a759efa6 |
331 | h->h_aliases = p; |
332 | for (i = 0; i < hsk.nalias; i++) { |
333 | *p++ = a; |
334 | PUT(alias[i]); |
d8fe3fc2 |
335 | free(alias[i]); |
a759efa6 |
336 | } |
337 | *p++ = 0; |
d8fe3fc2 |
338 | free(alias); |
a759efa6 |
339 | |
340 | #undef PUT |
341 | } |
342 | |
343 | return (h); |
344 | |
345 | /* --- Tidy up after various types of failure --- */ |
346 | |
347 | tidy_2: |
348 | { |
349 | int i; |
350 | for (i = 0; i < hsk.nalias && alias[i]; i++) |
d8fe3fc2 |
351 | free(alias[i]); |
352 | free(alias); |
a759efa6 |
353 | } |
354 | tidy_1: |
d8fe3fc2 |
355 | free(name); |
a759efa6 |
356 | tidy_0: |
357 | return (0); |
358 | } |
359 | |
360 | #endif |
361 | |
362 | /* --- @puthost@ --- * |
363 | * |
364 | * Arguments: @int fd@ = file descriptor |
365 | * @struct hostent *h@ = pointer to host structure |
366 | * |
367 | * Returns: Zero if successful. |
368 | * |
369 | * Use: Encodes a host structure. |
370 | */ |
371 | |
372 | static int puthost(int fd, struct hostent *h) |
373 | { |
374 | hostskel hsk; |
375 | int i; |
376 | |
377 | /* --- Fill in and send the skeleton structure --- */ |
378 | |
379 | for (i = 0; h->h_aliases[i]; i++) |
380 | ; |
381 | hsk.nalias = i; |
382 | for (i = 0; h->h_addr_list[i]; i++) |
383 | ; |
384 | hsk.naddr = i; |
385 | hsk.addrtype = h->h_addrtype; |
386 | hsk.addrsz = h->h_length; |
387 | if (dowrite(fd, &hsk, sizeof(hsk))) |
388 | return (-1); |
389 | |
390 | /* --- Send the name and alias strings --- */ |
391 | |
392 | if (putstring(fd, h->h_name)) |
393 | return (-1); |
394 | for (i = 0; h->h_aliases[i]; i++) { |
395 | if (putstring(fd, h->h_aliases[i])) |
396 | return (-1); |
397 | } |
398 | |
399 | /* --- Send the address data --- */ |
400 | |
401 | for (i = 0; h->h_addr_list[i]; i++) { |
402 | if (dowrite(fd, h->h_addr_list[i], hsk.addrsz)) |
403 | return (-1); |
404 | } |
405 | |
406 | /* --- OK, done --- */ |
407 | |
408 | return (0); |
409 | } |
410 | |
411 | /*----- Resolver server ---------------------------------------------------*/ |
412 | |
413 | /* --- @child@ --- * |
414 | * |
415 | * Arguments: @int rfd@ = output file descriptor for resolved hostnames |
416 | * @int cfd@ = input file descriptor for raw addresses |
417 | * |
418 | * Returns: Never. |
419 | * |
420 | * Use: Asynchronous name resolving process. |
421 | */ |
422 | |
423 | static void child(int rfd, int cfd) |
424 | { |
425 | /* --- Close other file descriptors --- */ |
426 | |
427 | { |
428 | int i; |
429 | int maxfd = sysconf(_SC_OPEN_MAX); |
430 | |
431 | if (maxfd < 0) |
432 | maxfd = 256; /* Fingers crossed... */ |
433 | for (i = 0; i < maxfd; i++) { |
434 | if (i != rfd && i != cfd && i != 1) |
435 | close(i); |
436 | } |
437 | } |
438 | |
364308dc |
439 | signal(SIGTERM, SIG_DFL); |
440 | signal(SIGHUP, SIG_DFL); |
441 | signal(SIGQUIT, SIG_DFL); |
442 | signal(SIGALRM, SIG_DFL); |
443 | signal(SIGINT, SIG_DFL); |
444 | |
a759efa6 |
445 | /* --- Main request/response loop --- */ |
446 | |
447 | for (;;) { |
448 | int req, resp; |
449 | struct hostent *h; |
450 | |
451 | /* --- Read the request --- */ |
452 | |
453 | if (doread(cfd, &req, sizeof(req))) |
454 | goto lose; |
455 | |
456 | /* --- Process it into a host structure --- */ |
457 | |
458 | switch (req) { |
459 | |
460 | /* --- Normal forward lookup --- */ |
461 | |
462 | case BRES_BYNAME: { |
463 | char *name = getstring(cfd); |
464 | if (!name) |
465 | goto lose; |
466 | h = gethostbyname(name); |
467 | free(name); |
468 | } break; |
469 | |
d8fe3fc2 |
470 | /* --- Reverse lookup --- */ |
a759efa6 |
471 | |
472 | case BRES_BYADDR: { |
473 | struct in_addr addr; |
474 | char *p; |
475 | if (doread(cfd, &addr, sizeof(addr))) |
476 | goto lose; |
477 | if ((h = gethostbyaddr((char *)&addr, sizeof(addr), AF_INET)) == 0) |
478 | goto fail; |
479 | |
480 | /* --- Do a forward lookup to confirm --- */ |
481 | |
482 | { |
483 | size_t sz = strlen(h->h_name) + 1; |
484 | if ((p = malloc(sz)) == 0) |
485 | goto fail; |
486 | memcpy(p, h->h_name, sz); |
487 | } |
488 | |
489 | h = gethostbyname(p); |
490 | free(p); |
491 | if (!h) |
492 | goto fail; |
493 | p = 0; |
494 | if (h) { |
495 | char **pp; |
496 | for (pp = h->h_addr_list; *pp; pp++) { |
497 | struct in_addr a; |
498 | memcpy(&a, *pp, sizeof(a)); |
499 | if (a.s_addr == addr.s_addr) { |
500 | p = h->h_name; |
501 | break; |
502 | } |
503 | } |
504 | } |
505 | if (!p) { |
506 | h = 0; |
507 | h_errno = NO_RECOVERY; |
508 | } |
509 | fail:; |
510 | } break; |
511 | |
512 | /* --- Unknown request -- may have lost sync --- */ |
513 | |
514 | default: |
515 | goto lose; |
516 | } |
517 | |
518 | /* --- Transmit the response --- */ |
519 | |
520 | if (h) { |
521 | resp = BRES_HOSTENT; |
522 | if (dowrite(rfd, &resp, sizeof(resp)) || puthost(rfd, h)) |
523 | goto lose; |
524 | } else { |
525 | resp = BRES_ERROR; |
526 | if (dowrite(rfd, &resp, sizeof(resp)) || |
527 | dowrite(rfd, &h_errno, sizeof(h_errno))) |
528 | goto lose; |
529 | } |
530 | } |
531 | |
532 | lose: |
533 | _exit(1); |
534 | } |
535 | |
536 | /* --- @main@ --- * |
537 | * |
538 | * Arguments: @int argc@ = number of command line arguments |
539 | * @char *argv[]@ = array of arguments |
540 | * |
541 | * Returns: Runs until killed or an error occurs. |
542 | * |
543 | * Use: A name resolver server process for mLib programs which need |
544 | * this sort of thing. |
545 | */ |
546 | |
547 | #ifdef BRES_STANDALONE |
548 | |
549 | int main(int argc, char *argv[]) |
550 | { |
551 | if (isatty(STDIN_FILENO)) { |
552 | char *p = strrchr(argv[0], '/'); |
553 | if (p) |
554 | p++; |
555 | else |
556 | p = argv[0]; |
557 | fprintf(stderr, |
558 | "%s: don't run this program unless you know what you're doing.\n", |
559 | p); |
560 | exit(1); |
561 | } |
562 | child(STDOUT_FILENO, STDIN_FILENO); |
563 | return (1); |
564 | } |
565 | |
566 | #endif |
567 | |
568 | /*----- Main code ---------------------------------------------------------*/ |
569 | |
570 | #ifndef BRES_STANDALONE |
571 | |
572 | /* --- @zap@ --- * |
573 | * |
574 | * Arguments: @bres_server *rs@ = pointer to server block |
575 | * |
576 | * Returns: --- |
577 | * |
578 | * Use: Kills a server process, reaps the losing child and makes |
579 | * things generally clean again. |
580 | */ |
581 | |
582 | static void zap(bres_server *rs) |
583 | { |
584 | /* --- Close the pipes, kill the child, and reap it --- */ |
585 | |
586 | if (rs->kid != -1) { |
587 | close(rs->fd); |
588 | close(rs->f.fd); |
589 | kill(rs->kid, SIGTERM); |
590 | waitpid(rs->kid, 0, 0); |
591 | rs->kid = -1; |
592 | } |
593 | |
594 | /* --- Move the server to the back of the list --- */ |
595 | |
596 | rs->next->prev = rs->prev; |
597 | rs->prev->next = rs->next; |
598 | rs->next = FREE; |
599 | rs->prev = FREE->prev; |
600 | FREE->prev->next = rs; |
601 | FREE->prev = rs; |
602 | } |
603 | |
604 | /* --- @bres_abort@ --- * |
605 | * |
606 | * Arguments: @bres_client *rc@ = pointer to client block |
607 | * |
608 | * Returns: --- |
609 | * |
610 | * Use: Removes a queued job. |
611 | */ |
612 | |
613 | void bres_abort(bres_client *rc) |
614 | { |
615 | if (rc->q == BRES_BYNAME) |
e2a18bd0 |
616 | xfree(rc->u.name); |
a759efa6 |
617 | if (rc->rs) { |
618 | sel_rmfile(&rc->rs->f); |
619 | zap(rc->rs); |
620 | rc->rs = 0; |
621 | } else { |
622 | rc->next->prev = rc->prev; |
623 | rc->prev->next = rc->next; |
624 | } |
625 | } |
626 | |
627 | /* --- @idle@ --- * |
628 | * |
629 | * Arguments: @struct timeval *tv@ = pointer to the current time |
630 | * @void *vp@ = pointer to a server block |
631 | * |
632 | * Returns: --- |
633 | * |
634 | * Use: Kills off a child which has been idle for too long. |
635 | */ |
636 | |
637 | static void idle(struct timeval *tv, void *vp) |
638 | { |
639 | bres_server *rs = vp; |
640 | zap(rs); |
641 | } |
642 | |
643 | /* --- @answer@ --- * |
644 | * |
645 | * Arguments: @int fd@ = file descriptor which is ready |
646 | * @unsigned mode@ = what it's doing now |
647 | * @void *vp@ = pointer to server block |
648 | * |
649 | * Returns: --- |
650 | * |
651 | * Use: Retrieves an answer from a name resolver process. |
652 | */ |
653 | |
654 | static void attach(bres_client */*rc*/); |
655 | |
656 | static void answer(int fd, unsigned mode, void *vp) |
657 | { |
658 | bres_server *rs = vp; |
659 | bres_client *rc = rs->rc; |
660 | struct hostent *h = 0; |
661 | int resp; |
662 | int fail = 1; |
663 | |
664 | /* --- Report the result to my client --- */ |
665 | |
666 | sel_rmfile(&rs->f); |
667 | h_errno = -1; |
668 | if (doread(fd, &resp, sizeof(resp)) == 0) { |
669 | switch (resp) { |
670 | case BRES_ERROR: |
671 | doread(fd, &h_errno, sizeof(h_errno)); |
672 | fail = 0; |
673 | break; |
674 | case BRES_HOSTENT: |
675 | h = gethost(fd); |
676 | fail = 0; |
677 | break; |
678 | } |
679 | } |
680 | if (rc) { |
681 | rc->func(h, rc->p); |
682 | if (rc->q == BRES_BYNAME) |
e2a18bd0 |
683 | xfree(rc->u.name); |
a759efa6 |
684 | } |
685 | if (h) |
d8fe3fc2 |
686 | free(h); |
a759efa6 |
687 | if (fail) |
688 | zap(rs); |
689 | if (!rc) |
690 | return; |
691 | |
692 | /* --- Wrap up the various structures --- */ |
693 | |
694 | rs->rc = 0; |
695 | rc->rs = 0; |
696 | rs->next = FREE->next; |
697 | rs->prev = FREE; |
698 | FREE->next->prev = rs; |
699 | FREE->next = rs; |
700 | |
701 | /* --- Tie a timer onto the server block --- */ |
702 | |
703 | { |
704 | struct timeval tv; |
705 | |
706 | gettimeofday(&tv, 0); |
707 | tv.tv_sec += BRES_IDLE; |
708 | sel_addtimer(sel, &rs->t, &tv, idle, rs); |
709 | } |
710 | |
711 | /* --- If there are any clients waiting, attach one --- */ |
712 | |
713 | if (QUEUE->next != QUEUE) { |
714 | rc = QUEUE->next; |
715 | QUEUE->next = rc->next; |
716 | rc->next->prev = QUEUE; |
717 | attach(rc); |
718 | } |
719 | } |
720 | |
721 | /* --- @start@ --- * |
722 | * |
723 | * Arguments: @bres_server *rs@ = pointer to a server block |
724 | * |
725 | * Returns: Zero if OK, nonzero if something failed. |
726 | * |
727 | * Use: Starts up a child resolver process. |
728 | */ |
729 | |
730 | static int start(bres_server *rs) |
731 | { |
732 | int rfd[2], cfd[2]; |
733 | pid_t kid; |
734 | |
735 | /* --- Make the pipes --- */ |
736 | |
737 | if (pipe(rfd)) |
738 | goto fail_0; |
739 | if (pipe(cfd)) |
740 | goto fail_1; |
741 | |
742 | /* --- Start up the child process --- */ |
743 | |
744 | if ((kid = fork()) < 0) |
745 | goto fail_2; |
746 | if (kid == 0) { |
747 | close(cfd[1]); |
748 | close(rfd[0]); |
749 | |
750 | if (server) { |
751 | dup2(cfd[0], STDIN_FILENO); |
752 | dup2(rfd[1], STDOUT_FILENO); |
753 | close(cfd[0]); |
754 | close(rfd[1]); |
755 | execlp(server, server, (char *)0); |
756 | child(STDOUT_FILENO, STDIN_FILENO); |
757 | } else |
758 | child(rfd[1], cfd[0]); |
759 | _exit(1); |
760 | } |
761 | |
762 | /* --- Fix up everything in the server block --- */ |
763 | |
764 | close(cfd[0]); |
765 | close(rfd[1]); |
766 | rs->fd = cfd[1]; |
767 | sel_initfile(sel, &rs->f, rfd[0], SEL_READ, answer, rs); |
768 | rs->kid = kid; |
769 | return (0); |
770 | |
771 | /* --- Fix up after errors --- */ |
772 | |
773 | fail_2: |
774 | close(cfd[0]); |
775 | close(cfd[1]); |
776 | fail_1: |
777 | close(rfd[0]); |
778 | close(rfd[1]); |
779 | fail_0: |
780 | return (-1); |
781 | } |
782 | |
783 | /* --- @attach@ --- * |
784 | * |
785 | * Arguments: @bres_client *rc@ = pointer to a client block |
786 | * |
787 | * Returns: --- |
788 | * |
789 | * Use: Attaches a client to a spare server (which is assumed to |
790 | * exist). |
791 | */ |
792 | |
793 | static void attach(bres_client *rc) |
794 | { |
795 | bres_server *rs; |
796 | int lose = 0; |
797 | |
798 | /* --- Fix up the server ready for the job --- * |
799 | * |
800 | * If the server has a process, remove its timer. Otherwise, fork off a |
801 | * new resolver process. This is also where I go if I find that the child |
802 | * resolver process has lost while I wasn't looking. Only one attempt at |
803 | * forking is performed. |
804 | */ |
805 | |
806 | again: |
807 | rs = FREE->next; |
808 | if (rs->kid != -1) |
809 | sel_rmtimer(&rs->t); |
810 | else { |
811 | if (lose || start(rs)) |
812 | goto lost; |
813 | lose = 1; |
814 | } |
815 | |
816 | /* --- Submit the job to the resolver --- */ |
817 | |
818 | { |
819 | struct sigaction sa, osa; |
820 | int e; |
821 | |
822 | /* --- Ignore @SIGPIPE@ for now --- * |
823 | * |
824 | * This way I can trap @EPIPE@ and reap a losing child, if there was one. |
825 | */ |
826 | |
827 | sa.sa_handler = SIG_IGN; |
828 | sa.sa_flags = 0; |
829 | sigemptyset(&sa.sa_mask); |
830 | sigaction(SIGPIPE, &sa, &osa); |
831 | |
832 | /* --- Write the new job to the child --- */ |
833 | |
834 | e = 0; |
835 | if (dowrite(rs->fd, &rc->q, sizeof(rc->q))) |
836 | e = errno; |
837 | else switch (rc->q) { |
838 | case BRES_BYADDR: |
839 | if (dowrite(rs->fd, &rc->u.addr, sizeof(rc->u.addr))) |
840 | e = errno; |
841 | break; |
842 | case BRES_BYNAME: |
843 | if (putstring(rs->fd, rc->u.name)) |
844 | e = errno; |
845 | break; |
846 | } |
847 | sigaction(SIGPIPE, &osa, 0); |
848 | |
849 | /* --- Sort out various errors --- * |
850 | * |
851 | * This was once more complicated, handling @EPIPE@ separately from other |
852 | * errors. Now everything's handled the same way. |
853 | */ |
854 | |
855 | if (e) { |
856 | zap(rs); |
857 | goto again; |
858 | } |
859 | } |
860 | |
861 | /* --- Fiddle with lists so that everything's OK --- */ |
862 | |
863 | sel_addfile(&rs->f); |
864 | rs->next->prev = FREE; |
865 | FREE->next = rs->next; |
866 | rs->next = rs->prev = rs; |
867 | rs->rc = rc; |
868 | rc->rs = rs; |
869 | return; |
870 | |
871 | lost: |
872 | rc->func(0, rc->p); |
873 | if (rc->q == BRES_BYNAME) |
e2a18bd0 |
874 | xfree(rc->u.name); |
a759efa6 |
875 | } |
876 | |
877 | /* --- @resolve@ --- * |
878 | * |
879 | * Arguments: @bres_client *rc@ = pointer to filled-in client block |
880 | * |
881 | * Returns: --- |
882 | * |
883 | * Use: Dispatcher for incoming resolution jobs. |
884 | */ |
885 | |
886 | static void resolve(bres_client *rc) |
887 | { |
888 | /* --- If there's a free server, plug it in --- */ |
889 | |
890 | rc->rs = 0; |
891 | if (FREE->next == FREE) { |
892 | rc->next = QUEUE; |
893 | rc->prev = QUEUE->prev; |
894 | QUEUE->prev->next = rc; |
895 | QUEUE->prev = rc; |
896 | } else |
897 | attach(rc); |
898 | } |
899 | |
900 | /* --- @bres_byaddr@ --- * |
901 | * |
902 | * Arguments: @bres_client *rc@ = pointer to client block |
903 | * @struct in_addr addr@ = address to resolve |
904 | * @void (*func)(struct hostent *h, void *p)@ = handler function |
905 | * @void *p@ = argument for handler function |
906 | * |
907 | * Returns: --- |
908 | * |
909 | * Use: Adds an address lookup job to the queue. The job will be |
910 | * processed when there's a spare resolver process to deal with |
911 | * it. |
912 | */ |
913 | |
914 | void bres_byaddr(bres_client *rc, struct in_addr addr, |
915 | void (*func)(struct hostent */*h*/, void */*p*/), |
916 | void *p) |
917 | { |
918 | rc->q = BRES_BYADDR; |
919 | rc->u.addr = addr; |
920 | rc->func = func; |
921 | rc->p = p; |
922 | resolve(rc); |
923 | } |
924 | |
925 | /* --- @bres_byname@ --- * |
926 | * |
927 | * Arguments: @bres_client *rc@ = pointer to client block |
928 | * @const char *name@ = name to resolve |
929 | * @void (*func)(struct hostent *h, void *p)@ = handler function |
930 | * @void *p@ = argument for handler function |
931 | * |
932 | * Returns: --- |
933 | * |
934 | * Use: Adds a name lookup job to the queue. The job will be |
935 | * processed when there's a spare resolver process to deal with |
936 | * it. |
937 | */ |
938 | |
939 | void bres_byname(bres_client *rc, const char *name, |
940 | void (*func)(struct hostent */*h*/, void */*p*/), |
941 | void *p) |
942 | { |
943 | rc->q = BRES_BYNAME; |
944 | rc->u.name = xstrdup(name); |
945 | rc->func = func; |
946 | rc->p = p; |
947 | resolve(rc); |
948 | } |
949 | |
950 | /* --- @bres_exec@ --- * |
951 | * |
952 | * Arguments: @const char *file@ = file containing server code or null |
953 | * |
954 | * Returns: --- |
955 | * |
956 | * Use: Makes `bres' use a standalone server rather than copies of |
957 | * the current process. This can reduce memory consumption for |
958 | * large processes, at the expense of startup time (which |
959 | * shouldn't be too bad anyway, because of the resolver design). |
960 | * If the filename is null, a default set up at install time is |
961 | * used. It's probably a good idea to leave it alone. |
962 | */ |
963 | |
964 | void bres_exec(const char *file) |
965 | { |
966 | if (file) |
967 | server = file; |
968 | else |
969 | server = BRES_SERVER; |
970 | } |
971 | |
972 | /* --- @bres_init@ --- * |
973 | * |
974 | * Arguments: @sel_state *s@ = pointer to select multiplexor |
975 | * |
976 | * Returns: --- |
977 | * |
978 | * Use: Initializes the background resolver for use. |
979 | */ |
980 | |
981 | void bres_init(sel_state *s) |
982 | { |
983 | int i; |
984 | |
985 | sel = s; |
986 | for (i = 0; i < BRES_MAX; i++) { |
987 | servers[i].next = FREE; |
988 | servers[i].prev = FREE->prev; |
989 | servers[i].kid = -1; |
990 | servers[i].rc = 0; |
991 | FREE->prev->next = &servers[i]; |
992 | FREE->prev = &servers[i]; |
993 | } |
994 | } |
995 | |
996 | #endif |
997 | |
998 | /*----- That's all, folks -------------------------------------------------*/ |