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 #include "got_path.h"
30 
31 #include "got_lib_lockfile.h"
32 
33 const struct got_error *
34 got_lockfile_lock(struct got_lockfile **lf, const char *path, int dir_fd)
35 {
36 	const struct got_error *err = NULL;
37 	int attempts = 5;
38 
39 	*lf = calloc(1, sizeof(**lf));
40 	if (*lf == NULL)
41 		return got_error_from_errno("calloc");
42 	(*lf)->fd = -1;
43 
44 	(*lf)->locked_path = strdup(path);
45 	if ((*lf)->locked_path == NULL) {
46 		err = got_error_from_errno("strdup");
47 		goto done;
48 	}
49 
50 	if (asprintf(&(*lf)->path, "%s%s", path, GOT_LOCKFILE_SUFFIX) == -1) {
51 		err = got_error_from_errno("asprintf");
52 		goto done;
53 	}
54 
55 	do {
56 		if (dir_fd != -1) {
57 			(*lf)->fd = openat(dir_fd, (*lf)->path,
58 			    O_RDONLY | O_CREAT | O_EXCL | O_EXLOCK | O_CLOEXEC,
59 			    GOT_DEFAULT_FILE_MODE);
60 		} else {
61 			(*lf)->fd = open((*lf)->path,
62 			    O_RDONLY | O_CREAT | O_EXCL | O_EXLOCK | O_CLOEXEC,
63 			    GOT_DEFAULT_FILE_MODE);
64 		}
65 		if ((*lf)->fd != -1)
66 			break;
67 		if (errno != EEXIST) {
68 			err = got_error_from_errno2("open", (*lf)->path);
69 			goto done;
70 		}
71 		sleep(1);
72 	} while (--attempts > 0);
73 
74 	if ((*lf)->fd == -1)
75 		err = got_error(GOT_ERR_LOCKFILE_TIMEOUT);
76 done:
77 	if (err) {
78 		got_lockfile_unlock(*lf, dir_fd);
79 		*lf = NULL;
80 	}
81 	return err;
82 }
83 
84 const struct got_error *
85 got_lockfile_unlock(struct got_lockfile *lf, int dir_fd)
86 {
87 	const struct got_error *err = NULL;
88 
89 	if (dir_fd != -1) {
90 		if (lf->path && lf->fd != -1 &&
91 		    unlinkat(dir_fd, lf->path, 0) != 0)
92 			err = got_error_from_errno("unlinkat");
93 	} else if (lf->path && lf->fd != -1 && unlink(lf->path) != 0)
94 		err = got_error_from_errno("unlink");
95 	if (lf->fd != -1 && close(lf->fd) == -1 && err == NULL)
96 		err = got_error_from_errno("close");
97 	free(lf->path);
98 	free(lf->locked_path);
99 	free(lf);
100 	return err;
101 }