1 /*
2  * Copyright (c) 2019 Stefan Sperling <stsp@openbsd.org>
3  *
4  * Permission to use, copy, modify, and distribute this software for any
5  * purpose with or without fee is hereby granted, provided that the above
6  * copyright notice and this permission notice appear in all copies.
7  *
8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15  */
16 
17 #include <sys/stat.h>
18 #include <sys/queue.h>
19 
20 #include <errno.h>
21 #include <fcntl.h>
22 #include <stdlib.h>
23 #include <unistd.h>
24 #include <string.h>
25 #include <stdio.h>
26 #include <time.h>
27 
28 #include "got_error.h"
29 
30 #include "got_lib_lockfile.h"
31 #include "got_lib_path.h"
32 
33 const struct got_error *
34 got_lockfile_lock(struct got_lockfile **lf, const char *path)
35 {
36 	const struct got_error *err = NULL;
37 	const int flags = O_RDONLY | O_CREAT | O_EXCL | O_EXLOCK;
38 	int attempts = 5;
39 
40 	*lf = calloc(1, sizeof(**lf));
41 	if (*lf == NULL)
42 		return got_error_from_errno();
43 	(*lf)->fd = -1;
44 
45 	(*lf)->locked_path = strdup(path);
46 	if ((*lf)->locked_path == NULL) {
47 		err = got_error_from_errno();
48 		goto done;
49 	}
50 
51 	if (asprintf(&(*lf)->path, "%s%s", path, GOT_LOCKFILE_SUFFIX) == -1) {
52 		err = got_error_from_errno();
53 		goto done;
54 	}
55 
56 	do {
57 		(*lf)->fd = open((*lf)->path, flags, GOT_DEFAULT_FILE_MODE);
58 		if ((*lf)->fd != -1)
59 			break;
60 		if (errno != EEXIST) {
61 			err = got_error_from_errno();
62 			goto done;
63 		}
64 		sleep(1);
65 	} while (--attempts > 0);
66 
67 	if ((*lf)->fd == -1)
68 		err = got_error(GOT_ERR_LOCKFILE_TIMEOUT);
69 done:
70 	if (err) {
71 		got_lockfile_unlock(*lf);
72 		*lf = NULL;
73 	}
74 	return err;
75 }
76 
77 const struct got_error *
78 got_lockfile_unlock(struct got_lockfile *lf)
79 {
80 	const struct got_error *err = NULL;
81 
82 	if (lf->path && lf->fd != -1 && unlink(lf->path) != 0)
83 		err = got_error_from_errno();
84 	if (lf->fd != -1 && close(lf->fd) != 0 && err == NULL)
85 		err = got_error_from_errno();
86 	free(lf->path);
87 	free(lf->locked_path);
88 	free(lf);
89 	return err;
90 }