[thirdparty/systemd.git] / src / resolve / resolved-resolv-conf.c

/* SPDX-License-Identifier: LGPL-2.1+ */

#include <resolv.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

#include "alloc-util.h"
#include "dns-domain.h"
#include "fd-util.h"
#include "fileio.h"
#include "ordered-set.h"
#include "resolved-conf.h"
#include "resolved-dns-server.h"
#include "resolved-resolv-conf.h"
#include "string-util.h"
#include "strv.h"
#include "tmpfile-util-label.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 server address */
#define PRIVATE_STATIC_RESOLV_CONF ROOTLIBEXECDIR "/resolv.conf"

int manager_check_resolv_conf(const Manager *m) {
        const char *path;
        struct stat st;
        int r;

        assert(m);

        /* This warns only when our stub listener is disabled and /etc/resolv.conf is a symlink to
         * PRIVATE_STATIC_RESOLV_CONF or PRIVATE_STUB_RESOLV_CONF. */

        if (m->dns_stub_listener_mode != DNS_STUB_LISTENER_NO)
                return 0;

        r = stat("/etc/resolv.conf", &st);
        if (r < 0) {
                if (errno == ENOENT)
                        return 0;

                return log_warning_errno(errno, "Failed to stat /etc/resolv.conf: %m");
        }

        FOREACH_STRING(path,
                       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) {
                        log_warning("DNSStubListener= is disabled, but /etc/resolv.conf is a symlink to %s "
                                    "which expects DNSStubListener= to be enabled.", path);
                        return -EOPNOTSUPP;
                }
        }

        return 0;
}

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;
        unsigned n = 0;
        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? */
        if (timespec_load(&st.st_mtim) == m->resolv_conf_mtime)
                return 0;

        if (file_is_our_own(&st))
                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;
        }

        if (file_is_our_own(&st))
                return 0;

        dns_server_mark_all(m->dns_servers);
        dns_search_domain_mark_all(m->search_domains);

        for (;;) {
                _cleanup_free_ char *line = NULL;
                const char *a;
                char *l;

                r = read_line(f, LONG_LINE_MAX, &line);
                if (r < 0) {
                        log_error_errno(r, "Failed to read /etc/resolv.conf: %m");
                        goto clear;
                }
                if (r == 0)
                        break;

                n++;

                l = strstrip(line);
                if (IN_SET(*l, '#', ';', 0))
                        continue;

                a = first_word(l, "nameserver");
                if (a) {
                        r = manager_parse_dns_server_string_and_warn(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);
                }

                log_syntax(NULL, LOG_DEBUG, "/etc/resolv.conf", n, 0, "Ignoring resolv.conf line: %s", l);
        }

        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
         * /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);

        /* If /etc/resolv.conf changed, make sure to forget everything we learned about the DNS servers. After all we
         * might now talk to a very different DNS server that just happens to have the same IP address as an old one
         * (think 192.168.1.1). */
        dns_server_reset_features_all(m->dns_servers);

        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) {
        DnsScope *scope;

        assert(s);
        assert(f);
        assert(count);

        if (!dns_server_string(s)) {
                log_warning("Out of memory, or invalid DNS address. Ignoring server.");
                return;
        }

        /* Check if the scope this DNS server belongs to is suitable as 'default' route for lookups; resolv.conf does
         * not have a syntax to express that, so it must not appear as a global name server to avoid routing unrelated
         * domains to it (which is a privacy violation, will most probably fail anyway, and adds unnecessary load) */
        scope = dns_server_scope(s);
        if (scope && !dns_scope_is_default_route(scope)) {
                log_debug("Scope of DNS server %s has only route-only domains, not using as global name server", dns_server_string(s));
                return;
        }

        if (*count == MAXNS)
                fputs("# Too many DNS servers configured, the following entries may be ignored.\n", f);
        (*count)++;

        fprintf(f, "nameserver %s\n", dns_server_string(s));
}

static void write_resolv_conf_search(
                OrderedSet *domains,
                FILE *f) {
        unsigned length = 0, count = 0;
        Iterator i;
        char *domain;

        assert(domains);
        assert(f);

        fputs("search", f);

        ORDERED_SET_FOREACH(domain, domains, i) {
                if (++count > MAXDNSRCH) {
                        fputs("\n# Too many search domains configured, remaining ones ignored.", f);
                        break;
                }
                length += strlen(domain) + 1;
                if (length > 256) {
                        fputs("\n# Total length of all search domains is too long, remaining ones ignored.", f);
                        break;
                }
                fputc(' ', f);
                fputs(domain, f);
        }

        fputs("\n", f);
}

static int write_uplink_resolv_conf_contents(FILE *f, OrderedSet *dns, OrderedSet *domains) {
        Iterator i;

        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("# 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))
                write_resolv_conf_search(domains, f);

        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 \"resolvectl 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"
                       "options edns0\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_uplink = NULL, *temp_path_stub = NULL;
        _cleanup_fclose_ FILE *f_uplink = NULL, *f_stub = NULL;
        int r;

        assert(m);

        /* Read the system /etc/resolv.conf first */
        (void) 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 log_warning_errno(r, "Failed to compile list of DNS servers: %m");

        r = manager_compile_search_domains(m, &domains, false);
        if (r < 0)
                return log_warning_errno(r, "Failed to compile list of search domains: %m");

        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_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) fchmod(fileno(f_stub), 0644);

        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_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_UPLINK_RESOLV_CONF);
        (void) unlink(temp_path_uplink);
        (void) unlink(PRIVATE_STUB_RESOLV_CONF);
        (void) unlink(temp_path_stub);

        return r;
}
Commit	Line	Data
53e1b683	1	/* SPDX-License-Identifier: LGPL-2.1+ */
f8dc7e34 LP	2
f8dc7e34 LP	3	#include <resolv.h>
ca78ad1d ZJS	4	#include <sys/stat.h>
	5	#include <sys/types.h>
	6	#include <unistd.h>
f8dc7e34 LP	7
	8	#include "alloc-util.h"
	9	#include "dns-domain.h"
	10	#include "fd-util.h"
f8dc7e34 LP	11	#include "fileio.h"
	12	#include "ordered-set.h"
	13	#include "resolved-conf.h"
59c0fd0e	14	#include "resolved-dns-server.h"
f8dc7e34 LP	15	#include "resolved-resolv-conf.h"
	16	#include "string-util.h"
	17	#include "strv.h"
e4de7287	18	#include "tmpfile-util-label.h"
f8dc7e34	19
b6de578d	20	/* A resolv.conf file containing the DNS server and domain data we learnt from uplink, i.e. the full uplink data */
a50d7910	21	#define PRIVATE_UPLINK_RESOLV_CONF "/run/systemd/resolve/resolv.conf"
b6de578d LP	22
b6de578d LP	23	/* A resolv.conf file containing the domain data we learnt from uplink, but our own DNS server address. */
a50d7910 LP	24	#define PRIVATE_STUB_RESOLV_CONF "/run/systemd/resolve/stub-resolv.conf"
a50d7910 LP	25
f43580f1	26	/* A static resolv.conf file containing no domains, but only our own DNS server address */
b6de578d LP	27	#define PRIVATE_STATIC_RESOLV_CONF ROOTLIBEXECDIR "/resolv.conf"
b6de578d LP	28
f43580f1 YW	29	int manager_check_resolv_conf(const Manager *m) {
	30	const char *path;
	31	struct stat st;
	32	int r;
	33
	34	assert(m);
	35
	36	/* This warns only when our stub listener is disabled and /etc/resolv.conf is a symlink to
	37	* PRIVATE_STATIC_RESOLV_CONF or PRIVATE_STUB_RESOLV_CONF. */
	38
	39	if (m->dns_stub_listener_mode != DNS_STUB_LISTENER_NO)
	40	return 0;
	41
	42	r = stat("/etc/resolv.conf", &st);
	43	if (r < 0) {
	44	if (errno == ENOENT)
	45	return 0;
	46
	47	return log_warning_errno(errno, "Failed to stat /etc/resolv.conf: %m");
	48	}
	49
	50	FOREACH_STRING(path,
	51	PRIVATE_STUB_RESOLV_CONF,
	52	PRIVATE_STATIC_RESOLV_CONF) {
	53
	54	struct stat own;
	55
	56	/* Is it symlinked to our own uplink file? */
	57	if (stat(path, &own) >= 0 &&
	58	st.st_dev == own.st_dev &&
	59	st.st_ino == own.st_ino) {
052a85d1 ZJS	60	log_warning("DNSStubListener= is disabled, but /etc/resolv.conf is a symlink to %s "
052a85d1 ZJS	61	"which expects DNSStubListener= to be enabled.", path);
f43580f1 YW	62	return -EOPNOTSUPP;
	63	}
	64	}
	65
	66	return 0;
	67	}
	68
043d3928	69	static bool file_is_our_own(const struct stat *st) {
b6de578d	70	const char *path;
043d3928 LP	71
	72	assert(st);
	73
b6de578d LP	74	FOREACH_STRING(path,
	75	PRIVATE_UPLINK_RESOLV_CONF,
	76	PRIVATE_STUB_RESOLV_CONF,
	77	PRIVATE_STATIC_RESOLV_CONF) {
	78
	79	struct stat own;
	80
	81	/* Is it symlinked to our own uplink file? */
	82	if (stat(path, &own) >= 0 &&
	83	st->st_dev == own.st_dev &&
	84	st->st_ino == own.st_ino)
	85	return true;
	86	}
043d3928 LP	87
	88	return false;
	89	}
	90
f8dc7e34 LP	91	int manager_read_resolv_conf(Manager *m) {
f8dc7e34 LP	92	_cleanup_fclose_ FILE *f = NULL;
043d3928	93	struct stat st;
b351c300	94	unsigned n = 0;
f8dc7e34 LP	95	int r;
	96
	97	assert(m);
	98
	99	/* Reads the system /etc/resolv.conf, if it exists and is not
	100	* symlinked to our own resolv.conf instance */
	101
	102	if (!m->read_resolv_conf)
	103	return 0;
	104
	105	r = stat("/etc/resolv.conf", &st);
	106	if (r < 0) {
	107	if (errno == ENOENT)
bf7fabd6 LP	108	return 0;
	109
	110	r = log_warning_errno(errno, "Failed to stat /etc/resolv.conf: %m");
f8dc7e34 LP	111	goto clear;
	112	}
	113
	114	/* Have we already seen the file? */
ace68cd7	115	if (timespec_load(&st.st_mtim) == m->resolv_conf_mtime)
f8dc7e34 LP	116	return 0;
f8dc7e34 LP	117
043d3928	118	if (file_is_our_own(&st))
bf7fabd6	119	return 0;
f8dc7e34 LP	120
	121	f = fopen("/etc/resolv.conf", "re");
	122	if (!f) {
	123	if (errno == ENOENT)
bf7fabd6 LP	124	return 0;
	125
	126	r = log_warning_errno(errno, "Failed to open /etc/resolv.conf: %m");
f8dc7e34 LP	127	goto clear;
	128	}
	129
	130	if (fstat(fileno(f), &st) < 0) {
	131	r = log_error_errno(errno, "Failed to stat open file: %m");
	132	goto clear;
	133	}
	134
043d3928 LP	135	if (file_is_our_own(&st))
	136	return 0;
	137
4b95f179	138	dns_server_mark_all(m->dns_servers);
a51c1048	139	dns_search_domain_mark_all(m->search_domains);
f8dc7e34	140
e1b9fc23 LP	141	for (;;) {
e1b9fc23 LP	142	_cleanup_free_ char *line = NULL;
f8dc7e34 LP	143	const char *a;
	144	char *l;
	145
e1b9fc23 LP	146	r = read_line(f, LONG_LINE_MAX, &line);
	147	if (r < 0) {
	148	log_error_errno(r, "Failed to read /etc/resolv.conf: %m");
	149	goto clear;
	150	}
	151	if (r == 0)
	152	break;
	153
b351c300 LP	154	n++;
b351c300 LP	155
f8dc7e34	156	l = strstrip(line);
b351c300	157	if (IN_SET(*l, '#', ';', 0))
f8dc7e34 LP	158	continue;
	159
	160	a = first_word(l, "nameserver");
	161	if (a) {
2817157b	162	r = manager_parse_dns_server_string_and_warn(m, DNS_SERVER_SYSTEM, a);
f8dc7e34 LP	163	if (r < 0)
	164	log_warning_errno(r, "Failed to parse DNS server address '%s', ignoring.", a);
	165
	166	continue;
	167	}
a51c1048 LP	168
	169	a = first_word(l, "domain");
	170	if (!a) /* We treat "domain" lines, and "search" lines as equivalent, and add both to our list. */
	171	a = first_word(l, "search");
	172	if (a) {
	173	r = manager_parse_search_domains_and_warn(m, a);
	174	if (r < 0)
	175	log_warning_errno(r, "Failed to parse search domain string '%s', ignoring.", a);
	176	}
b351c300 LP	177
b351c300 LP	178	log_syntax(NULL, LOG_DEBUG, "/etc/resolv.conf", n, 0, "Ignoring resolv.conf line: %s", l);
f8dc7e34 LP	179	}
f8dc7e34 LP	180
ace68cd7	181	m->resolv_conf_mtime = timespec_load(&st.st_mtim);
bf7fabd6	182
a51c1048 LP	183	/* Flush out all servers and search domains that are still
	184	* marked. Those are then ones that didn't appear in the new
	185	* /etc/resolv.conf */
4b95f179	186	dns_server_unlink_marked(m->dns_servers);
a51c1048	187	dns_search_domain_unlink_marked(m->search_domains);
f8dc7e34 LP	188
	189	/* Whenever /etc/resolv.conf changes, start using the first
	190	* DNS server of it. This is useful to deal with broken
	191	* network managing implementations (like NetworkManager),
	192	* that when connecting to a VPN place both the VPN DNS
	193	* servers and the local ones in /etc/resolv.conf. Without
	194	* resetting the DNS server to use back to the first entry we
	195	* will continue to use the local one thus being unable to
	196	* resolve VPN domains. */
	197	manager_set_dns_server(m, m->dns_servers);
	198
452b4e32 LP	199	/* Unconditionally flush the cache when /etc/resolv.conf is
	200	* modified, even if the data it contained was completely
	201	* identical to the previous version we used. We do this
	202	* because altering /etc/resolv.conf is typically done when
	203	* the network configuration changes, and that should be
	204	* enough to flush the global unicast DNS cache. */
	205	if (m->unicast_scope)
	206	dns_cache_flush(&m->unicast_scope->cache);
	207
59c0fd0e LP	208	/* If /etc/resolv.conf changed, make sure to forget everything we learned about the DNS servers. After all we
	209	* might now talk to a very different DNS server that just happens to have the same IP address as an old one
	210	* (think 192.168.1.1). */
	211	dns_server_reset_features_all(m->dns_servers);
	212
f8dc7e34 LP	213	return 0;
	214
	215	clear:
4b95f179	216	dns_server_unlink_all(m->dns_servers);
a51c1048	217	dns_search_domain_unlink_all(m->search_domains);
f8dc7e34 LP	218	return r;
	219	}
	220
	221	static void write_resolv_conf_server(DnsServer s, FILE f, unsigned *count) {
f76fa088 LP	222	DnsScope *scope;
f76fa088 LP	223
f8dc7e34 LP	224	assert(s);
	225	assert(f);
	226	assert(count);
	227
2817157b	228	if (!dns_server_string(s)) {
be4bf266	229	log_warning("Out of memory, or invalid DNS address. Ignoring server.");
f8dc7e34 LP	230	return;
	231	}
	232
ca5394d2 LP	233	/* Check if the scope this DNS server belongs to is suitable as 'default' route for lookups; resolv.conf does
	234	* not have a syntax to express that, so it must not appear as a global name server to avoid routing unrelated
	235	* domains to it (which is a privacy violation, will most probably fail anyway, and adds unnecessary load) */
f76fa088	236	scope = dns_server_scope(s);
ca5394d2	237	if (scope && !dns_scope_is_default_route(scope)) {
f76fa088	238	log_debug("Scope of DNS server %s has only route-only domains, not using as global name server", dns_server_string(s));
b9fe94ca MP	239	return;
	240	}
	241
f8dc7e34	242	if (*count == MAXNS)
0d536673	243	fputs("# Too many DNS servers configured, the following entries may be ignored.\n", f);
313cefa1	244	(*count)++;
f8dc7e34	245
2817157b	246	fprintf(f, "nameserver %s\n", dns_server_string(s));
f8dc7e34 LP	247	}
	248
	249	static void write_resolv_conf_search(
d2bc1251 MP	250	OrderedSet *domains,
	251	FILE *f) {
	252	unsigned length = 0, count = 0;
	253	Iterator i;
	254	char *domain;
f8dc7e34	255
d2bc1251	256	assert(domains);
f8dc7e34	257	assert(f);
f8dc7e34	258
0d536673	259	fputs("search", f);
f8dc7e34	260
d2bc1251 MP	261	ORDERED_SET_FOREACH(domain, domains, i) {
d2bc1251 MP	262	if (++count > MAXDNSRCH) {
0d536673	263	fputs("\n# Too many search domains configured, remaining ones ignored.", f);
d2bc1251 MP	264	break;
	265	}
	266	length += strlen(domain) + 1;
	267	if (length > 256) {
0d536673	268	fputs("\n# Total length of all search domains is too long, remaining ones ignored.", f);
d2bc1251 MP	269	break;
d2bc1251 MP	270	}
0d536673 LP	271	fputc(' ', f);
0d536673 LP	272	fputs(domain, f);
f8dc7e34 LP	273	}
f8dc7e34 LP	274
0d536673	275	fputs("\n", f);
f8dc7e34 LP	276	}
f8dc7e34 LP	277
e6b2d948	278	static int write_uplink_resolv_conf_contents(FILE f, OrderedSet dns, OrderedSet *domains) {
f8dc7e34 LP	279	Iterator i;
f8dc7e34 LP	280
0d536673 LP	281	fputs("# This file is managed by man:systemd-resolved(8). Do not edit.\n"
	282	"#\n"
	283	"# This is a dynamic resolv.conf file for connecting local clients directly to\n"
	284	"# all known uplink DNS servers. This file lists all configured search domains.\n"
	285	"#\n"
	286	"# Third party programs must not access this file directly, but only through the\n"
	287	"# symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a different way,\n"
	288	"# replace this symlink by a static file or a different symlink.\n"
	289	"#\n"
	290	"# See man:systemd-resolved.service(8) for details about the supported modes of\n"
	291	"# operation for /etc/resolv.conf.\n"
	292	"\n", f);
f8dc7e34 LP	293
f8dc7e34 LP	294	if (ordered_set_isempty(dns))
0d536673	295	fputs("# No DNS servers known.\n", f);
f8dc7e34 LP	296	else {
	297	unsigned count = 0;
	298	DnsServer *s;
	299
	300	ORDERED_SET_FOREACH(s, dns, i)
	301	write_resolv_conf_server(s, f, &count);
	302	}
	303
d2bc1251 MP	304	if (!ordered_set_isempty(domains))
d2bc1251 MP	305	write_resolv_conf_search(domains, f);
f8dc7e34 LP	306
	307	return fflush_and_check(f);
	308	}
	309
e6b2d948	310	static int write_stub_resolv_conf_contents(FILE f, OrderedSet dns, OrderedSet *domains) {
d937ef74 LP	311	fputs_unlocked("# This file is managed by man:systemd-resolved(8). Do not edit.\n"
	312	"#\n"
	313	"# This is a dynamic resolv.conf file for connecting local clients to the\n"
	314	"# internal DNS stub resolver of systemd-resolved. This file lists all\n"
	315	"# configured search domains.\n"
	316	"#\n"
5bc53fee	317	"# Run \"resolvectl status\" to see details about the uplink DNS servers\n"
d937ef74 LP	318	"# currently in use.\n"
	319	"#\n"
	320	"# Third party programs must not access this file directly, but only through the\n"
	321	"# symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a different way,\n"
	322	"# replace this symlink by a static file or a different symlink.\n"
	323	"#\n"
	324	"# See man:systemd-resolved.service(8) for details about the supported modes of\n"
	325	"# operation for /etc/resolv.conf.\n"
	326	"\n"
93158c77 TA	327	"nameserver 127.0.0.53\n"
93158c77 TA	328	"options edns0\n", f);
e6b2d948 DJL	329
	330	if (!ordered_set_isempty(domains))
	331	write_resolv_conf_search(domains, f);
	332
	333	return fflush_and_check(f);
	334	}
	335
f8dc7e34	336	int manager_write_resolv_conf(Manager *m) {
9176a57c	337
9176a57c	338	_cleanup_ordered_set_free_ OrderedSet dns = NULL, domains = NULL;
0d536673 LP	339	_cleanup_free_ char temp_path_uplink = NULL, temp_path_stub = NULL;
0d536673 LP	340	_cleanup_fclose_ FILE f_uplink = NULL, f_stub = NULL;
f8dc7e34 LP	341	int r;
	342
	343	assert(m);
	344
	345	/* Read the system /etc/resolv.conf first */
7207052d	346	(void) manager_read_resolv_conf(m);
f8dc7e34 LP	347
f8dc7e34 LP	348	/* Add the full list to a set, to filter out duplicates */
9176a57c LP	349	r = manager_compile_dns_servers(m, &dns);
9176a57c LP	350	if (r < 0)
7207052d	351	return log_warning_errno(r, "Failed to compile list of DNS servers: %m");
f8dc7e34	352
6f7da49d	353	r = manager_compile_search_domains(m, &domains, false);
9176a57c	354	if (r < 0)
7207052d	355	return log_warning_errno(r, "Failed to compile list of search domains: %m");
f8dc7e34	356
e6b2d948	357	r = fopen_temporary_label(PRIVATE_UPLINK_RESOLV_CONF, PRIVATE_UPLINK_RESOLV_CONF, &f_uplink, &temp_path_uplink);
f8dc7e34	358	if (r < 0)
7207052d	359	return log_warning_errno(r, "Failed to open private resolv.conf file for writing: %m");
0d536673	360
0d536673 LP	361	(void) fchmod(fileno(f_uplink), 0644);
0d536673 LP	362
e6b2d948 DJL	363	r = fopen_temporary_label(PRIVATE_STUB_RESOLV_CONF, PRIVATE_STUB_RESOLV_CONF, &f_stub, &temp_path_stub);
	364	if (r < 0)
	365	return log_warning_errno(r, "Failed to open private stub-resolv.conf file for writing: %m");
0d536673	366
e6b2d948	367	(void) fchmod(fileno(f_stub), 0644);
f8dc7e34	368
e6b2d948	369	r = write_uplink_resolv_conf_contents(f_uplink, dns, domains);
7207052d LP	370	if (r < 0) {
7207052d LP	371	log_error_errno(r, "Failed to write private resolv.conf contents: %m");
f8dc7e34	372	goto fail;
7207052d	373	}
f8dc7e34	374
e6b2d948	375	if (rename(temp_path_uplink, PRIVATE_UPLINK_RESOLV_CONF) < 0) {
7207052d	376	r = log_error_errno(errno, "Failed to move private resolv.conf file into place: %m");
f8dc7e34 LP	377	goto fail;
	378	}
	379
e6b2d948 DJL	380	r = write_stub_resolv_conf_contents(f_stub, dns, domains);
	381	if (r < 0) {
	382	log_error_errno(r, "Failed to write private stub-resolv.conf contents: %m");
	383	goto fail;
	384	}
	385
	386	if (rename(temp_path_stub, PRIVATE_STUB_RESOLV_CONF) < 0) {
	387	r = log_error_errno(errno, "Failed to move private stub-resolv.conf file into place: %m");
	388	goto fail;
	389	}
	390
f8dc7e34 LP	391	return 0;
	392
	393	fail:
e6b2d948 DJL	394	(void) unlink(PRIVATE_UPLINK_RESOLV_CONF);
	395	(void) unlink(temp_path_uplink);
	396	(void) unlink(PRIVATE_STUB_RESOLV_CONF);
	397	(void) unlink(temp_path_stub);
7207052d	398
f8dc7e34 LP	399	return r;
f8dc7e34 LP	400	}