1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
2
3 #include <errno.h>
4 #include <stdio.h>
5 #include <stdlib.h>
6 #include <sys/utsname.h>
7 #include <unistd.h>
8
9 #include "alloc-util.h"
10 #include "fd-util.h"
11 #include "fileio.h"
12 #include "fs-util.h"
13 #include "hostname-setup.h"
14 #include "hostname-util.h"
15 #include "log.h"
16 #include "macro.h"
17 #include "proc-cmdline.h"
18 #include "string-table.h"
19 #include "string-util.h"
20 #include "util.h"
21
sethostname_idempotent_full(const char * s,bool really)22 static int sethostname_idempotent_full(const char *s, bool really) {
23 struct utsname u;
24
25 assert(s);
26
27 assert_se(uname(&u) >= 0);
28
29 if (streq_ptr(s, u.nodename))
30 return 0;
31
32 if (really &&
33 sethostname(s, strlen(s)) < 0)
34 return -errno;
35
36 return 1;
37 }
38
sethostname_idempotent(const char * s)39 int sethostname_idempotent(const char *s) {
40 return sethostname_idempotent_full(s, true);
41 }
42
shorten_overlong(const char * s,char ** ret)43 int shorten_overlong(const char *s, char **ret) {
44 char *h, *p;
45
46 /* Shorten an overlong name to HOST_NAME_MAX or to the first dot,
47 * whatever comes earlier. */
48
49 assert(s);
50
51 h = strdup(s);
52 if (!h)
53 return -ENOMEM;
54
55 if (hostname_is_valid(h, 0)) {
56 *ret = h;
57 return 0;
58 }
59
60 p = strchr(h, '.');
61 if (p)
62 *p = 0;
63
64 strshorten(h, HOST_NAME_MAX);
65
66 if (!hostname_is_valid(h, 0)) {
67 free(h);
68 return -EDOM;
69 }
70
71 *ret = h;
72 return 1;
73 }
74
read_etc_hostname_stream(FILE * f,char ** ret)75 int read_etc_hostname_stream(FILE *f, char **ret) {
76 int r;
77
78 assert(f);
79 assert(ret);
80
81 for (;;) {
82 _cleanup_free_ char *line = NULL;
83 char *p;
84
85 r = read_line(f, LONG_LINE_MAX, &line);
86 if (r < 0)
87 return r;
88 if (r == 0) /* EOF without any hostname? the file is empty, let's treat that exactly like no file at all: ENOENT */
89 return -ENOENT;
90
91 p = strstrip(line);
92
93 /* File may have empty lines or comments, ignore them */
94 if (!IN_SET(*p, '\0', '#')) {
95 char *copy;
96
97 hostname_cleanup(p); /* normalize the hostname */
98
99 if (!hostname_is_valid(p, VALID_HOSTNAME_TRAILING_DOT)) /* check that the hostname we return is valid */
100 return -EBADMSG;
101
102 copy = strdup(p);
103 if (!copy)
104 return -ENOMEM;
105
106 *ret = copy;
107 return 0;
108 }
109 }
110 }
111
read_etc_hostname(const char * path,char ** ret)112 int read_etc_hostname(const char *path, char **ret) {
113 _cleanup_fclose_ FILE *f = NULL;
114
115 assert(ret);
116
117 if (!path)
118 path = "/etc/hostname";
119
120 f = fopen(path, "re");
121 if (!f)
122 return -errno;
123
124 return read_etc_hostname_stream(f, ret);
125 }
126
hostname_update_source_hint(const char * hostname,HostnameSource source)127 void hostname_update_source_hint(const char *hostname, HostnameSource source) {
128 int r;
129
130 /* Why save the value and not just create a flag file? This way we will
131 * notice if somebody sets the hostname directly (not going through hostnamed).
132 */
133
134 if (source == HOSTNAME_DEFAULT) {
135 r = write_string_file("/run/systemd/default-hostname", hostname,
136 WRITE_STRING_FILE_CREATE | WRITE_STRING_FILE_ATOMIC);
137 if (r < 0)
138 log_warning_errno(r, "Failed to create \"/run/systemd/default-hostname\": %m");
139 } else
140 unlink_or_warn("/run/systemd/default-hostname");
141 }
142
hostname_setup(bool really)143 int hostname_setup(bool really) {
144 _cleanup_free_ char *b = NULL;
145 const char *hn = NULL;
146 HostnameSource source;
147 bool enoent = false;
148 int r;
149
150 r = proc_cmdline_get_key("systemd.hostname", 0, &b);
151 if (r < 0)
152 log_warning_errno(r, "Failed to retrieve system hostname from kernel command line, ignoring: %m");
153 else if (r > 0) {
154 if (hostname_is_valid(b, true)) {
155 hn = b;
156 source = HOSTNAME_TRANSIENT;
157 } else {
158 log_warning("Hostname specified on kernel command line is invalid, ignoring: %s", b);
159 b = mfree(b);
160 }
161 }
162
163 if (!hn) {
164 r = read_etc_hostname(NULL, &b);
165 if (r < 0) {
166 if (r == -ENOENT)
167 enoent = true;
168 else
169 log_warning_errno(r, "Failed to read configured hostname: %m");
170 } else {
171 hn = b;
172 source = HOSTNAME_STATIC;
173 }
174 }
175
176 if (!hn) {
177 _cleanup_free_ char *buf = NULL;
178
179 /* Don't override the hostname if it is already set and not explicitly configured */
180
181 r = gethostname_full(GET_HOSTNAME_ALLOW_LOCALHOST, &buf);
182 if (r == -ENOMEM)
183 return log_oom();
184 if (r >= 0) {
185 log_debug("No hostname configured, leaving existing hostname <%s> in place.", buf);
186 return 0;
187 }
188
189 if (enoent)
190 log_info("No hostname configured, using default hostname.");
191
192 hn = b = get_default_hostname();
193 if (!hn)
194 return log_oom();
195
196 source = HOSTNAME_DEFAULT;
197
198 }
199
200 r = sethostname_idempotent_full(hn, really);
201 if (r < 0)
202 return log_warning_errno(r, "Failed to set hostname to <%s>: %m", hn);
203 if (r == 0)
204 log_debug("Hostname was already set to <%s>.", hn);
205 else
206 log_info("Hostname %s to <%s>.",
207 really ? "set" : "would have been set",
208 hn);
209
210 if (really)
211 hostname_update_source_hint(hn, source);
212
213 return r;
214 }
215
216 static const char* const hostname_source_table[] = {
217 [HOSTNAME_STATIC] = "static",
218 [HOSTNAME_TRANSIENT] = "transient",
219 [HOSTNAME_DEFAULT] = "default",
220 };
221
222 DEFINE_STRING_TABLE_LOOKUP(hostname_source, HostnameSource);
223