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f8dc7e34 LP |
1 | /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/ |
2 | ||
3 | /*** | |
4 | This file is part of systemd. | |
5 | ||
6 | Copyright 2014 Tom Gundersen <teg@jklm.no> | |
7 | ||
8 | systemd is free software; you can redistribute it and/or modify it | |
9 | under the terms of the GNU Lesser General Public License as published by | |
10 | the Free Software Foundation; either version 2.1 of the License, or | |
11 | (at your option) any later version. | |
12 | ||
13 | systemd is distributed in the hope that it will be useful, but | |
14 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
16 | Lesser General Public License for more details. | |
17 | ||
18 | You should have received a copy of the GNU Lesser General Public License | |
19 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
20 | ***/ | |
21 | ||
22 | #include <resolv.h> | |
23 | ||
24 | #include "alloc-util.h" | |
25 | #include "dns-domain.h" | |
26 | #include "fd-util.h" | |
27 | #include "fileio-label.h" | |
28 | #include "fileio.h" | |
29 | #include "ordered-set.h" | |
30 | #include "resolved-conf.h" | |
31 | #include "resolved-resolv-conf.h" | |
32 | #include "string-util.h" | |
33 | #include "strv.h" | |
34 | ||
35 | int manager_read_resolv_conf(Manager *m) { | |
36 | _cleanup_fclose_ FILE *f = NULL; | |
37 | struct stat st, own; | |
38 | char line[LINE_MAX]; | |
f8dc7e34 LP |
39 | usec_t t; |
40 | int r; | |
41 | ||
42 | assert(m); | |
43 | ||
44 | /* Reads the system /etc/resolv.conf, if it exists and is not | |
45 | * symlinked to our own resolv.conf instance */ | |
46 | ||
47 | if (!m->read_resolv_conf) | |
48 | return 0; | |
49 | ||
50 | r = stat("/etc/resolv.conf", &st); | |
51 | if (r < 0) { | |
52 | if (errno == ENOENT) | |
bf7fabd6 LP |
53 | return 0; |
54 | ||
55 | r = log_warning_errno(errno, "Failed to stat /etc/resolv.conf: %m"); | |
f8dc7e34 LP |
56 | goto clear; |
57 | } | |
58 | ||
59 | /* Have we already seen the file? */ | |
60 | t = timespec_load(&st.st_mtim); | |
61 | if (t == m->resolv_conf_mtime) | |
62 | return 0; | |
63 | ||
f8dc7e34 LP |
64 | /* Is it symlinked to our own file? */ |
65 | if (stat("/run/systemd/resolve/resolv.conf", &own) >= 0 && | |
66 | st.st_dev == own.st_dev && | |
bf7fabd6 LP |
67 | st.st_ino == own.st_ino) |
68 | return 0; | |
f8dc7e34 LP |
69 | |
70 | f = fopen("/etc/resolv.conf", "re"); | |
71 | if (!f) { | |
72 | if (errno == ENOENT) | |
bf7fabd6 LP |
73 | return 0; |
74 | ||
75 | r = log_warning_errno(errno, "Failed to open /etc/resolv.conf: %m"); | |
f8dc7e34 LP |
76 | goto clear; |
77 | } | |
78 | ||
79 | if (fstat(fileno(f), &st) < 0) { | |
80 | r = log_error_errno(errno, "Failed to stat open file: %m"); | |
81 | goto clear; | |
82 | } | |
83 | ||
4b95f179 | 84 | dns_server_mark_all(m->dns_servers); |
a51c1048 | 85 | dns_search_domain_mark_all(m->search_domains); |
f8dc7e34 LP |
86 | |
87 | FOREACH_LINE(line, f, r = -errno; goto clear) { | |
f8dc7e34 LP |
88 | const char *a; |
89 | char *l; | |
90 | ||
f8dc7e34 LP |
91 | l = strstrip(line); |
92 | if (*l == '#' || *l == ';') | |
93 | continue; | |
94 | ||
95 | a = first_word(l, "nameserver"); | |
96 | if (a) { | |
97 | r = manager_add_dns_server_by_string(m, DNS_SERVER_SYSTEM, a); | |
98 | if (r < 0) | |
99 | log_warning_errno(r, "Failed to parse DNS server address '%s', ignoring.", a); | |
100 | ||
101 | continue; | |
102 | } | |
a51c1048 LP |
103 | |
104 | a = first_word(l, "domain"); | |
105 | if (!a) /* We treat "domain" lines, and "search" lines as equivalent, and add both to our list. */ | |
106 | a = first_word(l, "search"); | |
107 | if (a) { | |
108 | r = manager_parse_search_domains_and_warn(m, a); | |
109 | if (r < 0) | |
110 | log_warning_errno(r, "Failed to parse search domain string '%s', ignoring.", a); | |
111 | } | |
f8dc7e34 LP |
112 | } |
113 | ||
bf7fabd6 LP |
114 | m->resolv_conf_mtime = t; |
115 | ||
a51c1048 LP |
116 | /* Flush out all servers and search domains that are still |
117 | * marked. Those are then ones that didn't appear in the new | |
118 | * /etc/resolv.conf */ | |
4b95f179 | 119 | dns_server_unlink_marked(m->dns_servers); |
a51c1048 | 120 | dns_search_domain_unlink_marked(m->search_domains); |
f8dc7e34 LP |
121 | |
122 | /* Whenever /etc/resolv.conf changes, start using the first | |
123 | * DNS server of it. This is useful to deal with broken | |
124 | * network managing implementations (like NetworkManager), | |
125 | * that when connecting to a VPN place both the VPN DNS | |
126 | * servers and the local ones in /etc/resolv.conf. Without | |
127 | * resetting the DNS server to use back to the first entry we | |
128 | * will continue to use the local one thus being unable to | |
129 | * resolve VPN domains. */ | |
130 | manager_set_dns_server(m, m->dns_servers); | |
131 | ||
452b4e32 LP |
132 | /* Unconditionally flush the cache when /etc/resolv.conf is |
133 | * modified, even if the data it contained was completely | |
134 | * identical to the previous version we used. We do this | |
135 | * because altering /etc/resolv.conf is typically done when | |
136 | * the network configuration changes, and that should be | |
137 | * enough to flush the global unicast DNS cache. */ | |
138 | if (m->unicast_scope) | |
139 | dns_cache_flush(&m->unicast_scope->cache); | |
140 | ||
f8dc7e34 LP |
141 | return 0; |
142 | ||
143 | clear: | |
4b95f179 | 144 | dns_server_unlink_all(m->dns_servers); |
a51c1048 | 145 | dns_search_domain_unlink_all(m->search_domains); |
f8dc7e34 LP |
146 | return r; |
147 | } | |
148 | ||
149 | static void write_resolv_conf_server(DnsServer *s, FILE *f, unsigned *count) { | |
150 | _cleanup_free_ char *t = NULL; | |
151 | int r; | |
152 | ||
153 | assert(s); | |
154 | assert(f); | |
155 | assert(count); | |
156 | ||
157 | r = in_addr_to_string(s->family, &s->address, &t); | |
158 | if (r < 0) { | |
159 | log_warning_errno(r, "Invalid DNS address. Ignoring: %m"); | |
160 | return; | |
161 | } | |
162 | ||
163 | if (*count == MAXNS) | |
164 | fputs("# Too many DNS servers configured, the following entries may be ignored.\n", f); | |
165 | (*count) ++; | |
166 | ||
167 | fprintf(f, "nameserver %s\n", t); | |
168 | } | |
169 | ||
170 | static void write_resolv_conf_search( | |
171 | const char *domain, | |
172 | FILE *f, | |
173 | unsigned *count, | |
174 | unsigned *length) { | |
175 | ||
176 | assert(domain); | |
177 | assert(f); | |
178 | assert(length); | |
179 | ||
180 | if (*count >= MAXDNSRCH || | |
181 | *length + strlen(domain) > 256) { | |
182 | if (*count == MAXDNSRCH) | |
183 | fputs(" # Too many search domains configured, remaining ones ignored.", f); | |
184 | if (*length <= 256) | |
185 | fputs(" # Total length of all search domains is too long, remaining ones ignored.", f); | |
186 | ||
187 | return; | |
188 | } | |
189 | ||
190 | (*length) += strlen(domain); | |
191 | (*count) ++; | |
192 | ||
193 | fputc(' ', f); | |
194 | fputs(domain, f); | |
195 | } | |
196 | ||
197 | static int write_resolv_conf_contents(FILE *f, OrderedSet *dns, OrderedSet *domains) { | |
198 | Iterator i; | |
199 | ||
200 | fputs("# This file is managed by systemd-resolved(8). Do not edit.\n#\n" | |
201 | "# Third party programs must not access this file directly, but\n" | |
202 | "# only through the symlink at /etc/resolv.conf. To manage\n" | |
203 | "# resolv.conf(5) in a different way, replace the symlink by a\n" | |
204 | "# static file or a different symlink.\n\n", f); | |
205 | ||
206 | if (ordered_set_isempty(dns)) | |
207 | fputs("# No DNS servers known.\n", f); | |
208 | else { | |
209 | unsigned count = 0; | |
210 | DnsServer *s; | |
211 | ||
212 | ORDERED_SET_FOREACH(s, dns, i) | |
213 | write_resolv_conf_server(s, f, &count); | |
214 | } | |
215 | ||
216 | if (!ordered_set_isempty(domains)) { | |
217 | unsigned length = 0, count = 0; | |
218 | char *domain; | |
219 | ||
220 | fputs("search", f); | |
221 | ORDERED_SET_FOREACH(domain, domains, i) | |
222 | write_resolv_conf_search(domain, f, &count, &length); | |
223 | fputs("\n", f); | |
224 | } | |
225 | ||
226 | return fflush_and_check(f); | |
227 | } | |
228 | ||
229 | int manager_write_resolv_conf(Manager *m) { | |
9176a57c LP |
230 | |
231 | #define PRIVATE_RESOLV_CONF "/run/systemd/resolve/resolv.conf" | |
232 | ||
233 | _cleanup_ordered_set_free_ OrderedSet *dns = NULL, *domains = NULL; | |
f8dc7e34 LP |
234 | _cleanup_free_ char *temp_path = NULL; |
235 | _cleanup_fclose_ FILE *f = NULL; | |
f8dc7e34 LP |
236 | int r; |
237 | ||
238 | assert(m); | |
239 | ||
240 | /* Read the system /etc/resolv.conf first */ | |
241 | manager_read_resolv_conf(m); | |
242 | ||
243 | /* Add the full list to a set, to filter out duplicates */ | |
9176a57c LP |
244 | r = manager_compile_dns_servers(m, &dns); |
245 | if (r < 0) | |
246 | return r; | |
f8dc7e34 | 247 | |
9176a57c LP |
248 | r = manager_compile_search_domains(m, &domains); |
249 | if (r < 0) | |
250 | return r; | |
f8dc7e34 | 251 | |
9176a57c | 252 | r = fopen_temporary_label(PRIVATE_RESOLV_CONF, PRIVATE_RESOLV_CONF, &f, &temp_path); |
f8dc7e34 LP |
253 | if (r < 0) |
254 | return r; | |
255 | ||
256 | fchmod(fileno(f), 0644); | |
257 | ||
258 | r = write_resolv_conf_contents(f, dns, domains); | |
259 | if (r < 0) | |
260 | goto fail; | |
261 | ||
9176a57c | 262 | if (rename(temp_path, PRIVATE_RESOLV_CONF) < 0) { |
f8dc7e34 LP |
263 | r = -errno; |
264 | goto fail; | |
265 | } | |
266 | ||
267 | return 0; | |
268 | ||
269 | fail: | |
9176a57c | 270 | (void) unlink(PRIVATE_RESOLV_CONF); |
f8dc7e34 LP |
271 | (void) unlink(temp_path); |
272 | return r; | |
273 | } |