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