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1 | /* |
2 | * Copyright (c) 2014 Nicira, Inc. | |
3 | * | |
4 | * Licensed under the Apache License, Version 2.0 (the "License"); | |
5 | * you may not use this file except in compliance with the License. | |
6 | * You may obtain a copy of the License at: | |
7 | * | |
8 | * http://www.apache.org/licenses/LICENSE-2.0 | |
9 | * | |
10 | * Unless required by applicable law or agreed to in writing, software | |
11 | * distributed under the License is distributed on an "AS IS" BASIS, | |
12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
13 | * See the License for the specific language governing permissions and | |
14 | * limitations under the License. | |
15 | */ | |
16 | #include <config.h> | |
17 | #include "daemon.h" | |
3834bcf2 | 18 | #include "daemon-private.h" |
d6bc33f3 GS |
19 | #include <errno.h> |
20 | #include <fcntl.h> | |
21 | #include <unistd.h> | |
e6211adc TG |
22 | #include "util.h" |
23 | #include "ovs-thread.h" | |
24 | #include "openvswitch/vlog.h" | |
d6bc33f3 GS |
25 | |
26 | VLOG_DEFINE_THIS_MODULE(daemon); | |
27 | ||
28 | /* For each of the standard file descriptors, whether to replace it by | |
29 | * /dev/null (if false) or keep it for the daemon to use (if true). */ | |
30 | static bool save_fds[3]; | |
31 | ||
3834bcf2 GS |
32 | /* Will daemonize() really detach? */ |
33 | bool | |
34 | get_detach(void) | |
35 | { | |
36 | return detach; | |
37 | } | |
38 | ||
39 | /* If configured with set_pidfile() or set_detach(), creates the pid file and | |
40 | * detaches from the foreground session. */ | |
41 | void | |
42 | daemonize(void) | |
43 | { | |
44 | daemonize_start(); | |
45 | daemonize_complete(); | |
46 | } | |
47 | ||
48 | /* Sets up a following call to daemonize() to create a pidfile named 'name'. | |
49 | * If 'name' begins with '/' (or contains ':' in windows), then it is treated | |
50 | * as an absolute path. Otherwise, it is taken relative to RUNDIR, | |
51 | * which is $(prefix)/var/run by default. | |
52 | * | |
53 | * If 'name' is null, then program_name followed by ".pid" is used. */ | |
54 | void | |
55 | set_pidfile(const char *name) | |
56 | { | |
57 | assert_single_threaded(); | |
58 | free(pidfile); | |
59 | pidfile = make_pidfile_name(name); | |
60 | } | |
61 | ||
d6bc33f3 GS |
62 | /* A daemon doesn't normally have any use for the file descriptors for stdin, |
63 | * stdout, and stderr after it detaches. To keep these file descriptors from | |
64 | * e.g. holding an SSH session open, by default detaching replaces each of | |
65 | * these file descriptors by /dev/null. But a few daemons expect the user to | |
66 | * redirect stdout or stderr to a file, in which case it is desirable to keep | |
67 | * these file descriptors. This function, therefore, disables replacing 'fd' | |
68 | * by /dev/null when the daemon detaches. */ | |
69 | void | |
70 | daemon_save_fd(int fd) | |
71 | { | |
72 | ovs_assert(fd == STDIN_FILENO || | |
73 | fd == STDOUT_FILENO || | |
74 | fd == STDERR_FILENO); | |
75 | save_fds[fd] = true; | |
76 | } | |
77 | ||
78 | /* Returns a readable and writable fd for /dev/null, if successful, otherwise | |
79 | * a negative errno value. The caller must not close the returned fd (because | |
80 | * the same fd will be handed out to subsequent callers). */ | |
81 | static int | |
82 | get_null_fd(void) | |
83 | { | |
84 | static int null_fd; | |
85 | #ifndef _WIN32 | |
86 | char *device = "/dev/null"; | |
87 | #else | |
88 | char *device = "nul"; | |
89 | #endif | |
90 | ||
91 | if (!null_fd) { | |
92 | null_fd = open(device, O_RDWR); | |
93 | if (null_fd < 0) { | |
94 | int error = errno; | |
95 | VLOG_ERR("could not open %s: %s", device, ovs_strerror(error)); | |
96 | null_fd = -error; | |
97 | } | |
98 | } | |
99 | ||
100 | return null_fd; | |
101 | } | |
102 | ||
103 | /* Close standard file descriptors (except any that the client has requested we | |
104 | * leave open by calling daemon_save_fd()). If we're started from e.g. an SSH | |
105 | * session, then this keeps us from holding that session open artificially. */ | |
106 | void | |
107 | close_standard_fds(void) | |
108 | { | |
109 | int null_fd = get_null_fd(); | |
110 | if (null_fd >= 0) { | |
111 | int fd; | |
112 | ||
113 | for (fd = 0; fd < 3; fd++) { | |
114 | if (!save_fds[fd]) { | |
115 | dup2(null_fd, fd); | |
116 | } | |
117 | } | |
118 | } | |
119 | ||
120 | /* Disable logging to stderr to avoid wasting CPU time. */ | |
121 | vlog_set_levels(NULL, VLF_CONSOLE, VLL_OFF); | |
122 | } |