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Diffstat (limited to 'src/resolve/resolved-resolv-conf.c')
-rw-r--r--src/resolve/resolved-resolv-conf.c149
1 files changed, 115 insertions, 34 deletions
diff --git a/src/resolve/resolved-resolv-conf.c b/src/resolve/resolved-resolv-conf.c
index e3d6a33409..bad04d6a29 100644
--- a/src/resolve/resolved-resolv-conf.c
+++ b/src/resolve/resolved-resolv-conf.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
/***
This file is part of systemd.
@@ -18,6 +19,7 @@
***/
#include <resolv.h>
+#include <stdio_ext.h>
#include "alloc-util.h"
#include "dns-domain.h"
@@ -31,11 +33,41 @@
#include "string-util.h"
#include "strv.h"
+/* A resolv.conf file containing the DNS server and domain data we learnt from uplink, i.e. the full uplink data */
+#define PRIVATE_UPLINK_RESOLV_CONF "/run/systemd/resolve/resolv.conf"
+
+/* A resolv.conf file containing the domain data we learnt from uplink, but our own DNS server address. */
+#define PRIVATE_STUB_RESOLV_CONF "/run/systemd/resolve/stub-resolv.conf"
+
+/* A static resolv.conf file containing no domains, but only our own DNS sever address */
+#define PRIVATE_STATIC_RESOLV_CONF ROOTLIBEXECDIR "/resolv.conf"
+
+static bool file_is_our_own(const struct stat *st) {
+ const char *path;
+
+ assert(st);
+
+ FOREACH_STRING(path,
+ PRIVATE_UPLINK_RESOLV_CONF,
+ PRIVATE_STUB_RESOLV_CONF,
+ PRIVATE_STATIC_RESOLV_CONF) {
+
+ struct stat own;
+
+ /* Is it symlinked to our own uplink file? */
+ if (stat(path, &own) >= 0 &&
+ st->st_dev == own.st_dev &&
+ st->st_ino == own.st_ino)
+ return true;
+ }
+
+ return false;
+}
+
int manager_read_resolv_conf(Manager *m) {
_cleanup_fclose_ FILE *f = NULL;
- struct stat st, own;
+ struct stat st;
char line[LINE_MAX];
- usec_t t;
int r;
assert(m);
@@ -56,14 +88,10 @@ int manager_read_resolv_conf(Manager *m) {
}
/* Have we already seen the file? */
- t = timespec_load(&st.st_mtim);
- if (t == m->resolv_conf_mtime)
+ if (timespec_load(&st.st_mtim) == m->resolv_conf_mtime)
return 0;
- /* Is it symlinked to our own file? */
- if (stat(PRIVATE_RESOLV_CONF, &own) >= 0 &&
- st.st_dev == own.st_dev &&
- st.st_ino == own.st_ino)
+ if (file_is_our_own(&st))
return 0;
f = fopen("/etc/resolv.conf", "re");
@@ -80,6 +108,9 @@ int manager_read_resolv_conf(Manager *m) {
goto clear;
}
+ if (file_is_our_own(&st))
+ return 0;
+
dns_server_mark_all(m->dns_servers);
dns_search_domain_mark_all(m->search_domains);
@@ -110,7 +141,7 @@ int manager_read_resolv_conf(Manager *m) {
}
}
- m->resolv_conf_mtime = t;
+ m->resolv_conf_mtime = timespec_load(&st.st_mtim);
/* Flush out all servers and search domains that are still
* marked. Those are then ones that didn't appear in the new
@@ -171,7 +202,7 @@ static void write_resolv_conf_server(DnsServer *s, FILE *f, unsigned *count) {
}
if (*count == MAXNS)
- fputs_unlocked("# Too many DNS servers configured, the following entries may be ignored.\n", f);
+ fputs("# Too many DNS servers configured, the following entries may be ignored.\n", f);
(*count)++;
fprintf(f, "nameserver %s\n", dns_server_string(s));
@@ -187,39 +218,43 @@ static void write_resolv_conf_search(
assert(domains);
assert(f);
- fputs_unlocked("search", f);
+ fputs("search", f);
ORDERED_SET_FOREACH(domain, domains, i) {
if (++count > MAXDNSRCH) {
- fputs_unlocked("\n# Too many search domains configured, remaining ones ignored.", f);
+ fputs("\n# Too many search domains configured, remaining ones ignored.", f);
break;
}
length += strlen(domain) + 1;
if (length > 256) {
- fputs_unlocked("\n# Total length of all search domains is too long, remaining ones ignored.", f);
+ fputs("\n# Total length of all search domains is too long, remaining ones ignored.", f);
break;
}
- fputc_unlocked(' ', f);
- fputs_unlocked(domain, f);
+ fputc(' ', f);
+ fputs(domain, f);
}
- fputs_unlocked("\n", f);
+ fputs("\n", f);
}
-static int write_resolv_conf_contents(FILE *f, OrderedSet *dns, OrderedSet *domains) {
+static int write_uplink_resolv_conf_contents(FILE *f, OrderedSet *dns, OrderedSet *domains) {
Iterator i;
- fputs_unlocked("# This file is managed by man:systemd-resolved(8). Do not edit.\n#\n"
- "# This is a dynamic resolv.conf file for connecting local clients directly to\n"
- "# all known DNS servers.\n#\n"
- "# Third party programs must not access this file directly, but only through the\n"
- "# symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a different way,\n"
- "# replace this symlink by a static file or a different symlink.\n#\n"
- "# See man:systemd-resolved.service(8) for details about the supported modes of\n"
- "# operation for /etc/resolv.conf.\n\n", f);
+ fputs("# This file is managed by man:systemd-resolved(8). Do not edit.\n"
+ "#\n"
+ "# This is a dynamic resolv.conf file for connecting local clients directly to\n"
+ "# all known uplink DNS servers. This file lists all configured search domains.\n"
+ "#\n"
+ "# Third party programs must not access this file directly, but only through the\n"
+ "# symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a different way,\n"
+ "# replace this symlink by a static file or a different symlink.\n"
+ "#\n"
+ "# See man:systemd-resolved.service(8) for details about the supported modes of\n"
+ "# operation for /etc/resolv.conf.\n"
+ "\n", f);
if (ordered_set_isempty(dns))
- fputs_unlocked("# No DNS servers known.\n", f);
+ fputs("# No DNS servers known.\n", f);
else {
unsigned count = 0;
DnsServer *s;
@@ -234,11 +269,36 @@ static int write_resolv_conf_contents(FILE *f, OrderedSet *dns, OrderedSet *doma
return fflush_and_check(f);
}
+static int write_stub_resolv_conf_contents(FILE *f, OrderedSet *dns, OrderedSet *domains) {
+ fputs_unlocked("# This file is managed by man:systemd-resolved(8). Do not edit.\n"
+ "#\n"
+ "# This is a dynamic resolv.conf file for connecting local clients to the\n"
+ "# internal DNS stub resolver of systemd-resolved. This file lists all\n"
+ "# configured search domains.\n"
+ "#\n"
+ "# Run \"systemd-resolve --status\" to see details about the uplink DNS servers\n"
+ "# currently in use.\n"
+ "#\n"
+ "# Third party programs must not access this file directly, but only through the\n"
+ "# symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a different way,\n"
+ "# replace this symlink by a static file or a different symlink.\n"
+ "#\n"
+ "# See man:systemd-resolved.service(8) for details about the supported modes of\n"
+ "# operation for /etc/resolv.conf.\n"
+ "\n"
+ "nameserver 127.0.0.53\n", f);
+
+ if (!ordered_set_isempty(domains))
+ write_resolv_conf_search(domains, f);
+
+ return fflush_and_check(f);
+}
+
int manager_write_resolv_conf(Manager *m) {
_cleanup_ordered_set_free_ OrderedSet *dns = NULL, *domains = NULL;
- _cleanup_free_ char *temp_path = NULL;
- _cleanup_fclose_ FILE *f = NULL;
+ _cleanup_free_ char *temp_path_uplink = NULL, *temp_path_stub = NULL;
+ _cleanup_fclose_ FILE *f_uplink = NULL, *f_stub = NULL;
int r;
assert(m);
@@ -255,28 +315,49 @@ int manager_write_resolv_conf(Manager *m) {
if (r < 0)
return log_warning_errno(r, "Failed to compile list of search domains: %m");
- r = fopen_temporary_label(PRIVATE_RESOLV_CONF, PRIVATE_RESOLV_CONF, &f, &temp_path);
+ r = fopen_temporary_label(PRIVATE_UPLINK_RESOLV_CONF, PRIVATE_UPLINK_RESOLV_CONF, &f_uplink, &temp_path_uplink);
if (r < 0)
return log_warning_errno(r, "Failed to open private resolv.conf file for writing: %m");
- (void) fchmod(fileno(f), 0644);
+ (void) __fsetlocking(f_uplink, FSETLOCKING_BYCALLER);
+ (void) fchmod(fileno(f_uplink), 0644);
+
+ r = fopen_temporary_label(PRIVATE_STUB_RESOLV_CONF, PRIVATE_STUB_RESOLV_CONF, &f_stub, &temp_path_stub);
+ if (r < 0)
+ return log_warning_errno(r, "Failed to open private stub-resolv.conf file for writing: %m");
+
+ (void) __fsetlocking(f_stub, FSETLOCKING_BYCALLER);
+ (void) fchmod(fileno(f_stub), 0644);
- r = write_resolv_conf_contents(f, dns, domains);
+ r = write_uplink_resolv_conf_contents(f_uplink, dns, domains);
if (r < 0) {
log_error_errno(r, "Failed to write private resolv.conf contents: %m");
goto fail;
}
- if (rename(temp_path, PRIVATE_RESOLV_CONF) < 0) {
+ if (rename(temp_path_uplink, PRIVATE_UPLINK_RESOLV_CONF) < 0) {
r = log_error_errno(errno, "Failed to move private resolv.conf file into place: %m");
goto fail;
}
+ r = write_stub_resolv_conf_contents(f_stub, dns, domains);
+ if (r < 0) {
+ log_error_errno(r, "Failed to write private stub-resolv.conf contents: %m");
+ goto fail;
+ }
+
+ if (rename(temp_path_stub, PRIVATE_STUB_RESOLV_CONF) < 0) {
+ r = log_error_errno(errno, "Failed to move private stub-resolv.conf file into place: %m");
+ goto fail;
+ }
+
return 0;
fail:
- (void) unlink(PRIVATE_RESOLV_CONF);
- (void) unlink(temp_path);
+ (void) unlink(PRIVATE_UPLINK_RESOLV_CONF);
+ (void) unlink(temp_path_uplink);
+ (void) unlink(PRIVATE_STUB_RESOLV_CONF);
+ (void) unlink(temp_path_stub);
return r;
}
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