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-rw-r--r--src/resolve/resolved-resolv-conf.c273
1 files changed, 273 insertions, 0 deletions
diff --git a/src/resolve/resolved-resolv-conf.c b/src/resolve/resolved-resolv-conf.c
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+++ b/src/resolve/resolved-resolv-conf.c
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+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+ This file is part of systemd.
+
+ Copyright 2014 Tom Gundersen <teg@jklm.no>
+
+ systemd is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
+ (at your option) any later version.
+
+ systemd is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with systemd; If not, see <http://www.gnu.org/licenses/>.
+ ***/
+
+#include <resolv.h>
+
+#include "alloc-util.h"
+#include "dns-domain.h"
+#include "fd-util.h"
+#include "fileio-label.h"
+#include "fileio.h"
+#include "ordered-set.h"
+#include "resolved-conf.h"
+#include "resolved-resolv-conf.h"
+#include "string-util.h"
+#include "strv.h"
+
+int manager_read_resolv_conf(Manager *m) {
+ _cleanup_fclose_ FILE *f = NULL;
+ struct stat st, own;
+ char line[LINE_MAX];
+ usec_t t;
+ int r;
+
+ assert(m);
+
+ /* Reads the system /etc/resolv.conf, if it exists and is not
+ * symlinked to our own resolv.conf instance */
+
+ if (!m->read_resolv_conf)
+ return 0;
+
+ r = stat("/etc/resolv.conf", &st);
+ if (r < 0) {
+ if (errno == ENOENT)
+ return 0;
+
+ r = log_warning_errno(errno, "Failed to stat /etc/resolv.conf: %m");
+ goto clear;
+ }
+
+ /* Have we already seen the file? */
+ t = timespec_load(&st.st_mtim);
+ if (t == m->resolv_conf_mtime)
+ return 0;
+
+ /* Is it symlinked to our own file? */
+ if (stat("/run/systemd/resolve/resolv.conf", &own) >= 0 &&
+ st.st_dev == own.st_dev &&
+ st.st_ino == own.st_ino)
+ return 0;
+
+ f = fopen("/etc/resolv.conf", "re");
+ if (!f) {
+ if (errno == ENOENT)
+ return 0;
+
+ r = log_warning_errno(errno, "Failed to open /etc/resolv.conf: %m");
+ goto clear;
+ }
+
+ if (fstat(fileno(f), &st) < 0) {
+ r = log_error_errno(errno, "Failed to stat open file: %m");
+ goto clear;
+ }
+
+ dns_server_mark_all(m->dns_servers);
+ dns_search_domain_mark_all(m->search_domains);
+
+ FOREACH_LINE(line, f, r = -errno; goto clear) {
+ const char *a;
+ char *l;
+
+ l = strstrip(line);
+ if (*l == '#' || *l == ';')
+ continue;
+
+ a = first_word(l, "nameserver");
+ if (a) {
+ r = manager_add_dns_server_by_string(m, DNS_SERVER_SYSTEM, a);
+ if (r < 0)
+ log_warning_errno(r, "Failed to parse DNS server address '%s', ignoring.", a);
+
+ continue;
+ }
+
+ a = first_word(l, "domain");
+ if (!a) /* We treat "domain" lines, and "search" lines as equivalent, and add both to our list. */
+ a = first_word(l, "search");
+ if (a) {
+ r = manager_parse_search_domains_and_warn(m, a);
+ if (r < 0)
+ log_warning_errno(r, "Failed to parse search domain string '%s', ignoring.", a);
+ }
+ }
+
+ m->resolv_conf_mtime = t;
+
+ /* Flush out all servers and search domains that are still
+ * marked. Those are then ones that didn't appear in the new
+ * /etc/resolv.conf */
+ dns_server_unlink_marked(m->dns_servers);
+ dns_search_domain_unlink_marked(m->search_domains);
+
+ /* Whenever /etc/resolv.conf changes, start using the first
+ * DNS server of it. This is useful to deal with broken
+ * network managing implementations (like NetworkManager),
+ * that when connecting to a VPN place both the VPN DNS
+ * servers and the local ones in /etc/resolv.conf. Without
+ * resetting the DNS server to use back to the first entry we
+ * will continue to use the local one thus being unable to
+ * resolve VPN domains. */
+ manager_set_dns_server(m, m->dns_servers);
+
+ /* Unconditionally flush the cache when /etc/resolv.conf is
+ * modified, even if the data it contained was completely
+ * identical to the previous version we used. We do this
+ * because altering /etc/resolv.conf is typically done when
+ * the network configuration changes, and that should be
+ * enough to flush the global unicast DNS cache. */
+ if (m->unicast_scope)
+ dns_cache_flush(&m->unicast_scope->cache);
+
+ return 0;
+
+clear:
+ dns_server_unlink_all(m->dns_servers);
+ dns_search_domain_unlink_all(m->search_domains);
+ return r;
+}
+
+static void write_resolv_conf_server(DnsServer *s, FILE *f, unsigned *count) {
+ _cleanup_free_ char *t = NULL;
+ int r;
+
+ assert(s);
+ assert(f);
+ assert(count);
+
+ r = in_addr_to_string(s->family, &s->address, &t);
+ if (r < 0) {
+ log_warning_errno(r, "Invalid DNS address. Ignoring: %m");
+ return;
+ }
+
+ if (*count == MAXNS)
+ fputs("# Too many DNS servers configured, the following entries may be ignored.\n", f);
+ (*count) ++;
+
+ fprintf(f, "nameserver %s\n", t);
+}
+
+static void write_resolv_conf_search(
+ const char *domain,
+ FILE *f,
+ unsigned *count,
+ unsigned *length) {
+
+ assert(domain);
+ assert(f);
+ assert(length);
+
+ if (*count >= MAXDNSRCH ||
+ *length + strlen(domain) > 256) {
+ if (*count == MAXDNSRCH)
+ fputs(" # Too many search domains configured, remaining ones ignored.", f);
+ if (*length <= 256)
+ fputs(" # Total length of all search domains is too long, remaining ones ignored.", f);
+
+ return;
+ }
+
+ (*length) += strlen(domain);
+ (*count) ++;
+
+ fputc(' ', f);
+ fputs(domain, f);
+}
+
+static int write_resolv_conf_contents(FILE *f, OrderedSet *dns, OrderedSet *domains) {
+ Iterator i;
+
+ fputs("# This file is managed by systemd-resolved(8). Do not edit.\n#\n"
+ "# Third party programs must not access this file directly, but\n"
+ "# only through the symlink at /etc/resolv.conf. To manage\n"
+ "# resolv.conf(5) in a different way, replace the symlink by a\n"
+ "# static file or a different symlink.\n\n", f);
+
+ if (ordered_set_isempty(dns))
+ fputs("# No DNS servers known.\n", f);
+ else {
+ unsigned count = 0;
+ DnsServer *s;
+
+ ORDERED_SET_FOREACH(s, dns, i)
+ write_resolv_conf_server(s, f, &count);
+ }
+
+ if (!ordered_set_isempty(domains)) {
+ unsigned length = 0, count = 0;
+ char *domain;
+
+ fputs("search", f);
+ ORDERED_SET_FOREACH(domain, domains, i)
+ write_resolv_conf_search(domain, f, &count, &length);
+ fputs("\n", f);
+ }
+
+ return fflush_and_check(f);
+}
+
+int manager_write_resolv_conf(Manager *m) {
+
+ #define PRIVATE_RESOLV_CONF "/run/systemd/resolve/resolv.conf"
+
+ _cleanup_ordered_set_free_ OrderedSet *dns = NULL, *domains = NULL;
+ _cleanup_free_ char *temp_path = NULL;
+ _cleanup_fclose_ FILE *f = NULL;
+ int r;
+
+ assert(m);
+
+ /* Read the system /etc/resolv.conf first */
+ manager_read_resolv_conf(m);
+
+ /* Add the full list to a set, to filter out duplicates */
+ r = manager_compile_dns_servers(m, &dns);
+ if (r < 0)
+ return r;
+
+ r = manager_compile_search_domains(m, &domains);
+ if (r < 0)
+ return r;
+
+ r = fopen_temporary_label(PRIVATE_RESOLV_CONF, PRIVATE_RESOLV_CONF, &f, &temp_path);
+ if (r < 0)
+ return r;
+
+ fchmod(fileno(f), 0644);
+
+ r = write_resolv_conf_contents(f, dns, domains);
+ if (r < 0)
+ goto fail;
+
+ if (rename(temp_path, PRIVATE_RESOLV_CONF) < 0) {
+ r = -errno;
+ goto fail;
+ }
+
+ return 0;
+
+fail:
+ (void) unlink(PRIVATE_RESOLV_CONF);
+ (void) unlink(temp_path);
+ return r;
+}