Commit | Line | Data |
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059ec3d9 PH |
1 | /* $Cambridge: exim/src/src/exim_lock.c,v 1.1 2004/10/07 10:39:01 ph10 Exp $ */ |
2 | ||
3 | /* A program to lock a file exactly as Exim would, for investigation of | |
4 | interlocking problems. | |
5 | ||
6 | Options: -fcntl use fcntl() lock | |
7 | -flock use flock() lock | |
8 | -lockfile use lock file | |
9 | -mbx use mbx locking rules, with either fcntl() or flock() | |
10 | ||
11 | Default is -fcntl -lockfile. | |
12 | ||
13 | Argument: the name of the lock file | |
14 | */ | |
15 | ||
16 | #include "os.h" | |
17 | ||
18 | #include <stdio.h> | |
19 | #include <stdlib.h> | |
20 | #include <string.h> | |
21 | #include <signal.h> | |
22 | #include <errno.h> | |
23 | #include <time.h> | |
24 | #include <netdb.h> | |
25 | #include <fcntl.h> | |
26 | #include <unistd.h> | |
27 | #include <utime.h> | |
28 | #include <sys/utsname.h> | |
29 | #include <sys/stat.h> | |
30 | #include <sys/file.h> | |
31 | #include <pwd.h> | |
32 | ||
33 | /* Not all systems have flock() available. Those that do must define LOCK_SH | |
34 | in sys/file.h. */ | |
35 | ||
36 | #ifndef LOCK_SH | |
37 | #define NO_FLOCK | |
38 | #endif | |
39 | ||
40 | ||
41 | typedef int BOOL; | |
42 | #define FALSE 0 | |
43 | #define TRUE 1 | |
44 | ||
45 | ||
46 | /* Flag for timeout signal handler */ | |
47 | ||
48 | static int sigalrm_seen = FALSE; | |
49 | ||
50 | ||
51 | /* We need to pull in strerror() and os_non_restarting_signal() from the | |
52 | os.c source, if they are required for this OS. However, we don't need any of | |
53 | the other stuff in os.c, so force the other macros to omit it. */ | |
54 | ||
55 | #ifndef OS_RESTARTING_SIGNAL | |
56 | #define OS_RESTARTING_SIGNAL | |
57 | #endif | |
58 | ||
59 | #ifndef OS_STRSIGNAL | |
60 | #define OS_STRSIGNAL | |
61 | #endif | |
62 | ||
63 | #ifndef OS_STREXIT | |
64 | #define OS_STREXIT | |
65 | #endif | |
66 | ||
67 | #ifndef OS_LOAD_AVERAGE | |
68 | #define OS_LOAD_AVERAGE | |
69 | #endif | |
70 | ||
71 | #ifndef FIND_RUNNING_INTERFACES | |
72 | #define FIND_RUNNING_INTERFACES | |
73 | #endif | |
74 | ||
75 | #include "../src/os.c" | |
76 | ||
77 | ||
78 | ||
79 | /************************************************* | |
80 | * Timeout handler * | |
81 | *************************************************/ | |
82 | ||
83 | static void | |
84 | sigalrm_handler(int sig) | |
85 | { | |
86 | sig = sig; /* Keep picky compilers happy */ | |
87 | sigalrm_seen = TRUE; | |
88 | } | |
89 | ||
90 | ||
91 | ||
92 | /************************************************* | |
93 | * Give usage and die * | |
94 | *************************************************/ | |
95 | ||
96 | static void | |
97 | usage(void) | |
98 | { | |
99 | printf("usage: exim_lock [-v] [-q] [-lockfile] [-fcntl] [-flock] [-mbx]\n" | |
100 | " [-retries <n>] [-interval <n>] [-timeout <n>] [-restore-times]\n" | |
101 | " <file name> [command]\n"); | |
102 | exit(1); | |
103 | } | |
104 | ||
105 | ||
106 | ||
107 | /************************************************* | |
108 | * Apply a lock to a file descriptor * | |
109 | *************************************************/ | |
110 | ||
111 | static int | |
112 | apply_lock(int fd, int fcntltype, BOOL dofcntl, int fcntltime, BOOL doflock, | |
113 | int flocktime) | |
114 | { | |
115 | int yield = 0; | |
116 | int save_errno; | |
117 | struct flock lock_data; | |
118 | lock_data.l_type = fcntltype; | |
119 | lock_data.l_whence = lock_data.l_start = lock_data.l_len = 0; | |
120 | ||
121 | sigalrm_seen = FALSE; | |
122 | ||
123 | if (dofcntl) | |
124 | { | |
125 | if (fcntltime > 0) | |
126 | { | |
127 | os_non_restarting_signal(SIGALRM, sigalrm_handler); | |
128 | alarm(fcntltime); | |
129 | yield = fcntl(fd, F_SETLKW, &lock_data); | |
130 | save_errno = errno; | |
131 | alarm(0); | |
132 | errno = save_errno; | |
133 | } | |
134 | else yield = fcntl(fd, F_SETLK, &lock_data); | |
135 | if (yield < 0) printf("exim_lock: fcntl() failed: %s\n", strerror(errno)); | |
136 | } | |
137 | ||
138 | #ifndef NO_FLOCK | |
139 | if (doflock && (yield >= 0)) | |
140 | { | |
141 | int flocktype = (fcntltype == F_WRLCK)? LOCK_EX : LOCK_SH; | |
142 | if (flocktime > 0) | |
143 | { | |
144 | os_non_restarting_signal(SIGALRM, sigalrm_handler); | |
145 | alarm(flocktime); | |
146 | yield = flock(fd, flocktype); | |
147 | save_errno = errno; | |
148 | alarm(0); | |
149 | errno = save_errno; | |
150 | } | |
151 | else yield = flock(fd, flocktype | LOCK_NB); | |
152 | if (yield < 0) printf("exim_lock: flock() failed: %s\n", strerror(errno)); | |
153 | } | |
154 | #endif | |
155 | ||
156 | return yield; | |
157 | } | |
158 | ||
159 | ||
160 | ||
161 | /************************************************* | |
162 | * The exim_lock program * | |
163 | *************************************************/ | |
164 | ||
165 | int main(int argc, char **argv) | |
166 | { | |
167 | int lock_retries = 10; | |
168 | int lock_interval = 3; | |
169 | int lock_fcntl_timeout = 0; | |
170 | int lock_flock_timeout = 0; | |
171 | int i, j, len; | |
172 | int fd = -1; | |
173 | int hd = -1; | |
174 | int md = -1; | |
175 | int yield = 0; | |
176 | int now = time(NULL); | |
177 | BOOL use_lockfile = FALSE; | |
178 | BOOL use_fcntl = FALSE; | |
179 | BOOL use_flock = FALSE; | |
180 | BOOL use_mbx = FALSE; | |
181 | BOOL verbose = FALSE; | |
182 | BOOL quiet = FALSE; | |
183 | BOOL restore_times = FALSE; | |
184 | char *filename; | |
185 | char *lockname = NULL, *hitchname = NULL; | |
186 | char *primary_hostname, *command; | |
187 | struct utsname s; | |
188 | char buffer[256]; | |
189 | char tempname[256]; | |
190 | ||
191 | /* Decode options */ | |
192 | ||
193 | for (i = 1; i < argc; i++) | |
194 | { | |
195 | char *arg = argv[i]; | |
196 | if (*arg != '-') break; | |
197 | if (strcmp(arg, "-fcntl") == 0) use_fcntl = TRUE; | |
198 | else if (strcmp(arg, "-flock") == 0) use_flock = TRUE; | |
199 | else if (strcmp(arg, "-lockfile") == 0) use_lockfile = TRUE; | |
200 | else if (strcmp(arg, "-mbx") == 0) use_mbx = TRUE; | |
201 | else if (strcmp(arg, "-v") == 0) verbose = TRUE; | |
202 | else if (strcmp(arg, "-q") == 0) quiet = TRUE; | |
203 | else if (strcmp(arg, "-restore-times") == 0) restore_times = TRUE; | |
204 | else if (++i < argc) | |
205 | { | |
206 | int value = atoi(argv[i]); | |
207 | if (strcmp(arg, "-retries") == 0) lock_retries = value; | |
208 | else if (strcmp(arg, "-interval") == 0) lock_interval = value; | |
209 | else if (strcmp(arg, "-timeout") == 0) | |
210 | lock_fcntl_timeout = lock_flock_timeout = value; | |
211 | else usage(); | |
212 | } | |
213 | else usage(); | |
214 | } | |
215 | ||
216 | if (quiet) verbose = 0; | |
217 | ||
218 | /* Can't use flock() if the OS doesn't provide it */ | |
219 | ||
220 | #ifdef NO_FLOCK | |
221 | if (use_flock) | |
222 | { | |
223 | printf("exim_lock: can't use flock() because it was not available in the\n" | |
224 | " operating system when exim_lock was compiled\n"); | |
225 | exit(1); | |
226 | } | |
227 | #endif | |
228 | ||
229 | /* Default is to use lockfiles and fcntl(). */ | |
230 | ||
231 | if (!use_lockfile && !use_fcntl && !use_flock && !use_mbx) | |
232 | use_lockfile = use_fcntl = TRUE; | |
233 | ||
234 | /* Default fcntl() for use with mbx */ | |
235 | ||
236 | if (use_mbx && !use_fcntl && !use_flock) use_fcntl = TRUE; | |
237 | ||
238 | /* Unset unused timeouts */ | |
239 | ||
240 | if (!use_fcntl) lock_fcntl_timeout = 0; | |
241 | if (!use_flock) lock_flock_timeout = 0; | |
242 | ||
243 | /* A file name is required */ | |
244 | ||
245 | if (i >= argc) usage(); | |
246 | ||
247 | filename = argv[i++]; | |
248 | ||
249 | /* Expand file names starting with ~ */ | |
250 | ||
251 | if (*filename == '~') | |
252 | { | |
253 | struct passwd *pw; | |
254 | ||
255 | if (*(++filename) == '/') | |
256 | pw = getpwuid(getuid()); | |
257 | else | |
258 | { | |
259 | char *s = buffer; | |
260 | while (*filename != 0 && *filename != '/') | |
261 | *s++ = *filename++; | |
262 | *s = 0; | |
263 | pw = getpwnam(buffer); | |
264 | } | |
265 | ||
266 | if (pw == NULL) | |
267 | { | |
268 | printf("exim_lock: unable to expand file name %s\n", argv[i-1]); | |
269 | exit(1); | |
270 | } | |
271 | ||
272 | if ((int)strlen(pw->pw_dir) + (int)strlen(filename) + 1 > sizeof(buffer)) | |
273 | { | |
274 | printf("exim_lock: expanded file name %s%s is too long", pw->pw_dir, | |
275 | filename); | |
276 | exit(1); | |
277 | } | |
278 | ||
279 | strcpy(buffer, pw->pw_dir); | |
280 | strcat(buffer, filename); | |
281 | filename = buffer; | |
282 | } | |
283 | ||
284 | /* If using a lock file, prepare by creating the lock file name and | |
285 | the hitching post name. */ | |
286 | ||
287 | if (use_lockfile) | |
288 | { | |
289 | if (uname(&s) < 0) | |
290 | { | |
291 | printf("exim_lock: failed to find host name using uname()\n"); | |
292 | exit(1); | |
293 | } | |
294 | primary_hostname = s.nodename; | |
295 | ||
296 | len = (int)strlen(filename); | |
297 | lockname = malloc(len + 8); | |
298 | sprintf(lockname, "%s.lock", filename); | |
299 | hitchname = malloc(len + 32 + (int)strlen(primary_hostname)); | |
300 | sprintf(hitchname, "%s.%s.%08x.%08x", lockname, primary_hostname, | |
301 | now, (int)getpid()); | |
302 | ||
303 | if (verbose) | |
304 | printf("exim_lock: lockname = %s\n hitchname = %s\n", lockname, | |
305 | hitchname); | |
306 | } | |
307 | ||
308 | /* Locking retry loop */ | |
309 | ||
310 | for (j = 0; j < lock_retries; j++) | |
311 | { | |
312 | int sleep_before_retry = TRUE; | |
313 | struct stat statbuf, ostatbuf; | |
314 | ||
315 | /* Try to build a lock file if so configured */ | |
316 | ||
317 | if (use_lockfile) | |
318 | { | |
319 | int rc; | |
320 | if (verbose) printf("exim_lock: creating lock file\n"); | |
321 | hd = open(hitchname, O_WRONLY | O_CREAT | O_EXCL, 0440); | |
322 | if (hd < 0) | |
323 | { | |
324 | printf("exim_lock: failed to create hitching post %s: %s\n", hitchname, | |
325 | strerror(errno)); | |
326 | exit(1); | |
327 | } | |
328 | ||
329 | /* Apply hitching post algorithm. */ | |
330 | ||
331 | if ((rc = link(hitchname, lockname)) != 0) fstat(hd, &statbuf); | |
332 | close(hd); | |
333 | unlink(hitchname); | |
334 | ||
335 | if (rc != 0 && statbuf.st_nlink != 2) | |
336 | { | |
337 | printf("exim_lock: failed to link hitching post to lock file\n"); | |
338 | hd = -1; | |
339 | goto RETRY; | |
340 | } | |
341 | ||
342 | if (!quiet) printf("exim_lock: lock file successfully created\n"); | |
343 | } | |
344 | ||
345 | /* We are done if no other locking required. */ | |
346 | ||
347 | if (!use_fcntl && !use_flock && !use_mbx) break; | |
348 | ||
349 | /* Open the file for writing. */ | |
350 | ||
351 | fd = open(filename, O_RDWR + O_APPEND); | |
352 | if (fd < 0) | |
353 | { | |
354 | printf("exim_lock: failed to open %s for writing: %s\n", filename, | |
355 | strerror(errno)); | |
356 | yield = 1; | |
357 | goto CLEAN_UP; | |
358 | } | |
359 | ||
360 | /* If there is a timeout, implying blocked locking, we don't want to | |
361 | sleep before any retries after this. */ | |
362 | ||
363 | if (lock_fcntl_timeout > 0 || lock_flock_timeout > 0) | |
364 | sleep_before_retry = FALSE; | |
365 | ||
366 | /* Lock using fcntl. There are pros and cons to using a blocking call vs | |
367 | a non-blocking call and retries. Exim is non-blocking by default, but setting | |
368 | a timeout changes it to blocking. */ | |
369 | ||
370 | if (!use_mbx && (use_fcntl || use_flock)) | |
371 | { | |
372 | if (apply_lock(fd, F_WRLCK, use_fcntl, lock_fcntl_timeout, use_flock, | |
373 | lock_flock_timeout) >= 0) | |
374 | { | |
375 | if (!quiet) | |
376 | { | |
377 | if (use_fcntl) printf("exim_lock: fcntl() lock successfully applied\n"); | |
378 | if (use_flock) printf("exim_lock: flock() lock successfully applied\n"); | |
379 | } | |
380 | break; | |
381 | } | |
382 | else goto RETRY; /* Message already output */ | |
383 | } | |
384 | ||
385 | /* Lock using MBX rules. This is complicated and is documented with the | |
386 | source of the c-client library that goes with Pine and IMAP. What has to | |
387 | be done to interwork correctly is to take out a shared lock on the mailbox, | |
388 | and an exclusive lock on a /tmp file. */ | |
389 | ||
390 | else | |
391 | { | |
392 | if (apply_lock(fd, F_RDLCK, use_fcntl, lock_fcntl_timeout, use_flock, | |
393 | lock_flock_timeout) >= 0) | |
394 | { | |
395 | if (!quiet) | |
396 | { | |
397 | if (use_fcntl) | |
398 | printf("exim_lock: fcntl() read lock successfully applied\n"); | |
399 | if (use_flock) | |
400 | printf("exim_lock: fcntl() read lock successfully applied\n"); | |
401 | } | |
402 | } | |
403 | else goto RETRY; /* Message already output */ | |
404 | ||
405 | if (fstat(fd, &statbuf) < 0) | |
406 | { | |
407 | printf("exim_lock: fstat() of %s failed: %s\n", filename, | |
408 | strerror(errno)); | |
409 | yield = 1; | |
410 | goto CLEAN_UP; | |
411 | } | |
412 | ||
413 | /* Set up file in /tmp and check its state if already existing. */ | |
414 | ||
415 | sprintf(tempname, "/tmp/.%lx.%lx", (long)statbuf.st_dev, | |
416 | (long)statbuf.st_ino); | |
417 | ||
418 | if (lstat(tempname, &statbuf) >= 0) | |
419 | { | |
420 | if ((statbuf.st_mode & S_IFMT) == S_IFLNK) | |
421 | { | |
422 | printf("exim_lock: symbolic link on lock name %s\n", tempname); | |
423 | yield = 1; | |
424 | goto CLEAN_UP; | |
425 | } | |
426 | if (statbuf.st_nlink > 1) | |
427 | { | |
428 | printf("exim_lock: hard link to lock name %s\n", tempname); | |
429 | yield = 1; | |
430 | goto CLEAN_UP; | |
431 | } | |
432 | } | |
433 | ||
434 | md = open(tempname, O_RDWR | O_CREAT, 0600); | |
435 | if (md < 0) | |
436 | { | |
437 | printf("exim_lock: failed to create mbx lock file %s: %s\n", | |
438 | tempname, strerror(errno)); | |
439 | goto CLEAN_UP; | |
440 | } | |
441 | ||
442 | chmod (tempname, 0600); | |
443 | ||
444 | if (apply_lock(md, F_WRLCK, use_fcntl, lock_fcntl_timeout, use_flock, | |
445 | lock_flock_timeout) >= 0) | |
446 | { | |
447 | if (!quiet) | |
448 | { | |
449 | if (use_fcntl) | |
450 | printf("exim_lock: fcntl() lock successfully applied to mbx " | |
451 | "lock file %s\n", tempname); | |
452 | if (use_flock) | |
453 | printf("exim_lock: flock() lock successfully applied to mbx " | |
454 | "lock file %s\n", tempname); | |
455 | } | |
456 | ||
457 | /* This test checks for a race condition */ | |
458 | ||
459 | if (lstat(tempname, &statbuf) != 0 || | |
460 | fstat(md, &ostatbuf) != 0 || | |
461 | statbuf.st_dev != ostatbuf.st_dev || | |
462 | statbuf.st_ino != ostatbuf.st_ino) | |
463 | { | |
464 | if (!quiet) printf("exim_lock: mbx lock file %s changed between " | |
465 | "creation and locking\n", tempname); | |
466 | goto RETRY; | |
467 | } | |
468 | else break; | |
469 | } | |
470 | else goto RETRY; /* Message already output */ | |
471 | } | |
472 | ||
473 | /* Clean up before retrying */ | |
474 | ||
475 | RETRY: | |
476 | ||
477 | if (md >= 0) | |
478 | { | |
479 | if (close(md) < 0) | |
480 | printf("exim_lock: close %s failed: %s\n", tempname, strerror(errno)); | |
481 | else | |
482 | if (!quiet) printf("exim_lock: %s closed\n", tempname); | |
483 | md = -1; | |
484 | } | |
485 | ||
486 | if (fd >= 0) | |
487 | { | |
488 | if (close(fd) < 0) | |
489 | printf("exim_lock: close failed: %s\n", strerror(errno)); | |
490 | else | |
491 | if (!quiet) printf("exim_lock: file closed\n"); | |
492 | fd = -1; | |
493 | } | |
494 | ||
495 | if (hd >= 0) | |
496 | { | |
497 | if (unlink(lockname) < 0) | |
498 | printf("exim_lock: unlink of %s failed: %s\n", lockname, strerror(errno)); | |
499 | else | |
500 | if (!quiet) printf("exim_lock: lock file removed\n"); | |
501 | hd = -1; | |
502 | } | |
503 | ||
504 | /* If a blocking call timed out, break the retry loop if the total time | |
505 | so far is not less than than retries * interval. */ | |
506 | ||
507 | if (sigalrm_seen && | |
508 | (j + 1) * ((lock_fcntl_timeout > lock_flock_timeout)? | |
509 | lock_fcntl_timeout : lock_flock_timeout) >= | |
510 | lock_retries * lock_interval) | |
511 | j = lock_retries; | |
512 | ||
513 | /* Wait a bit before retrying, except when it was a blocked fcntl() that | |
514 | caused the problem. */ | |
515 | ||
516 | if (j < lock_retries && sleep_before_retry) | |
517 | { | |
518 | printf(" ... waiting\n"); | |
519 | sleep(lock_interval); | |
520 | } | |
521 | } | |
522 | ||
523 | if (j >= lock_retries) | |
524 | { | |
525 | printf("exim_lock: locking failed too many times\n"); | |
526 | yield = 1; | |
527 | goto CLEAN_UP; | |
528 | } | |
529 | ||
530 | if (!quiet) printf("exim_lock: locking %s succeeded: ", filename); | |
531 | ||
532 | /* If there are no further arguments, run the user's shell; otherwise | |
533 | the next argument is a command to run. */ | |
534 | ||
535 | if (i >= argc) | |
536 | { | |
537 | command = getenv("SHELL"); | |
538 | if (command == NULL || *command == 0) command = "/bin/sh"; | |
539 | if (!quiet) printf("running %s ...\n", command); | |
540 | } | |
541 | else | |
542 | { | |
543 | command = argv[i]; | |
544 | if (!quiet) printf("running the command ...\n"); | |
545 | } | |
546 | ||
547 | /* Run the command, saving and restoring the times if required. */ | |
548 | ||
549 | if (restore_times) | |
550 | { | |
551 | struct stat strestore; | |
552 | struct utimbuf ut; | |
553 | stat(filename, &strestore); | |
554 | system(command); | |
555 | ut.actime = strestore.st_atime; | |
556 | ut.modtime = strestore.st_mtime; | |
557 | utime(filename, &ut); | |
558 | } | |
559 | else system(command); | |
560 | ||
561 | /* Remove the locks and exit. Unlink the /tmp file if we can get an exclusive | |
562 | lock on the mailbox. This should be a non-blocking lock call, as there is no | |
563 | point in waiting. */ | |
564 | ||
565 | CLEAN_UP: | |
566 | ||
567 | if (md >= 0) | |
568 | { | |
569 | if (apply_lock(fd, F_WRLCK, use_fcntl, 0, use_flock, 0) >= 0) | |
570 | { | |
571 | if (!quiet) printf("exim_lock: %s unlinked - no sharers\n", tempname); | |
572 | unlink(tempname); | |
573 | } | |
574 | else if (!quiet) | |
575 | printf("exim_lock: %s not unlinked - unable to get exclusive mailbox lock\n", | |
576 | tempname); | |
577 | if (close(md) < 0) | |
578 | printf("exim_lock: close %s failed: %s\n", tempname, strerror(errno)); | |
579 | else | |
580 | if (!quiet) printf("exim_lock: %s closed\n", tempname); | |
581 | } | |
582 | ||
583 | if (fd >= 0) | |
584 | { | |
585 | if (close(fd) < 0) | |
586 | printf("exim_lock: close %s failed: %s\n", filename, strerror(errno)); | |
587 | else | |
588 | if (!quiet) printf("exim_lock: %s closed\n", filename); | |
589 | } | |
590 | ||
591 | if (hd >= 0) | |
592 | { | |
593 | if (unlink(lockname) < 0) | |
594 | printf("exim_lock: unlink %s failed: %s\n", lockname, strerror(errno)); | |
595 | else | |
596 | if (!quiet) printf("exim_lock: lock file removed\n"); | |
597 | } | |
598 | ||
599 | return yield; | |
600 | } | |
601 | ||
602 | /* End */ |