| /* SPDX-License-Identifier: LGPL-2.1-or-later */ |
| |
| #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 "fs-util.h" |
| #include "label.h" |
| #include "ordered-set.h" |
| #include "resolved-conf.h" |
| #include "resolved-dns-server.h" |
| #include "resolved-resolv-conf.h" |
| #include "stat-util.h" |
| #include "string-table.h" |
| #include "string-util.h" |
| #include "strv.h" |
| #include "tmpfile-util-label.h" |
| |
| int manager_check_resolv_conf(const Manager *m) { |
| struct stat st, own; |
| |
| assert(m); |
| |
| /* This warns only when our stub listener is disabled and /etc/resolv.conf is a symlink to |
| * PRIVATE_STATIC_RESOLV_CONF. */ |
| |
| if (m->dns_stub_listener_mode != DNS_STUB_LISTENER_NO) |
| return 0; |
| |
| if (stat("/etc/resolv.conf", &st) < 0) { |
| if (errno == ENOENT) |
| return 0; |
| |
| return log_warning_errno(errno, "Failed to stat /etc/resolv.conf: %m"); |
| } |
| |
| /* Is it symlinked to our own uplink file? */ |
| if (stat(PRIVATE_STATIC_RESOLV_CONF, &own) >= 0 && |
| stat_inode_same(&st, &own)) |
| return log_warning_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), |
| "DNSStubListener= is disabled, but /etc/resolv.conf is a symlink to " |
| PRIVATE_STATIC_RESOLV_CONF " which expects DNSStubListener= to be enabled."); |
| |
| return 0; |
| } |
| |
| static bool file_is_our_own(const struct stat *st) { |
| 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 && |
| stat_inode_same(st, &own)) |
| 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 (stat_inode_unmodified(&st, &m->resolv_conf_stat)) |
| 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); |
| |
| continue; |
| } |
| |
| log_syntax(NULL, LOG_DEBUG, "/etc/resolv.conf", n, 0, "Ignoring resolv.conf line: %s", l); |
| } |
| |
| m->resolv_conf_stat = st; |
| |
| /* 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; |
| } |
| |
| /* resolv.conf simply doesn't support any other ports than 53, hence there's nothing much we can |
| * do — we have to suppress these entries */ |
| if (dns_server_port(s) != 53) { |
| log_debug("DNS server %s with non-standard UDP port number, suppressing from generated resolv.conf.", dns_server_string(s)); |
| 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) { |
| char *domain; |
| |
| assert(domains); |
| assert(f); |
| |
| fputs("search", f); |
| |
| ORDERED_SET_FOREACH(domain, domains) { |
| fputc(' ', f); |
| fputs(domain, f); |
| } |
| |
| fputs("\n", f); |
| } |
| |
| static int write_uplink_resolv_conf_contents(FILE *f, OrderedSet *dns, OrderedSet *domains) { |
| |
| fputs("# This is "PRIVATE_UPLINK_RESOLV_CONF" managed by man:systemd-resolved(8).\n" |
| "# Do not edit.\n" |
| "#\n" |
| "# This file might be symlinked as /etc/resolv.conf. If you're looking at\n" |
| "# /etc/resolv.conf and seeing this text, you have followed the symlink.\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 should typically not access this file directly, but only\n" |
| "# through the symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a\n" |
| "# different way, 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) |
| write_resolv_conf_server(s, f, &count); |
| } |
| |
| if (ordered_set_isempty(domains)) |
| fputs("search .\n", f); /* Make sure that if the local hostname is chosen as fqdn this does not |
| * imply a search domain */ |
| else |
| 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("# This is "PRIVATE_STUB_RESOLV_CONF" managed by man:systemd-resolved(8).\n" |
| "# Do not edit.\n" |
| "#\n" |
| "# This file might be symlinked as /etc/resolv.conf. If you're looking at\n" |
| "# /etc/resolv.conf and seeing this text, you have followed the symlink.\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 should typically not access this file directly, but only\n" |
| "# through the symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a\n" |
| "# different way, 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 trust-ad\n", f); |
| |
| if (ordered_set_isempty(domains)) |
| fputs("search .\n", f); /* Make sure that if the local hostname is chosen as fqdn this does not |
| * imply a search domain */ |
| else |
| 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_(unlink_and_freep) 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, ignoring: %m"); |
| |
| r = manager_compile_search_domains(m, &domains, false); |
| if (r < 0) |
| return log_warning_errno(r, "Failed to compile list of search domains, ignoring: %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 new %s for writing, ignoring: %m", PRIVATE_UPLINK_RESOLV_CONF); |
| |
| (void) fchmod(fileno(f_uplink), 0644); |
| |
| r = write_uplink_resolv_conf_contents(f_uplink, dns, domains); |
| if (r < 0) |
| return log_warning_errno(r, "Failed to write new %s, ignoring: %m", PRIVATE_UPLINK_RESOLV_CONF); |
| |
| if (m->dns_stub_listener_mode != DNS_STUB_LISTENER_NO) { |
| 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 new %s for writing, ignoring: %m", PRIVATE_STUB_RESOLV_CONF); |
| |
| (void) fchmod(fileno(f_stub), 0644); |
| |
| r = write_stub_resolv_conf_contents(f_stub, dns, domains); |
| if (r < 0) |
| return log_warning_errno(r, "Failed to write new %s, ignoring: %m", PRIVATE_STUB_RESOLV_CONF); |
| |
| r = conservative_rename(temp_path_stub, PRIVATE_STUB_RESOLV_CONF); |
| if (r < 0) |
| log_warning_errno(r, "Failed to move new %s into place, ignoring: %m", PRIVATE_STUB_RESOLV_CONF); |
| |
| temp_path_stub = mfree(temp_path_stub); /* free the string explicitly, so that we don't unlink anymore */ |
| } else { |
| r = symlink_atomic_label(basename(PRIVATE_UPLINK_RESOLV_CONF), PRIVATE_STUB_RESOLV_CONF); |
| if (r < 0) |
| log_warning_errno(r, "Failed to symlink %s, ignoring: %m", PRIVATE_STUB_RESOLV_CONF); |
| } |
| |
| r = conservative_rename(temp_path_uplink, PRIVATE_UPLINK_RESOLV_CONF); |
| if (r < 0) |
| log_warning_errno(r, "Failed to move new %s into place: %m", PRIVATE_UPLINK_RESOLV_CONF); |
| |
| temp_path_uplink = mfree(temp_path_uplink); /* free the string explicitly, so that we don't unlink anymore */ |
| return r; |
| } |
| |
| int resolv_conf_mode(void) { |
| static const char * const table[_RESOLV_CONF_MODE_MAX] = { |
| [RESOLV_CONF_UPLINK] = PRIVATE_UPLINK_RESOLV_CONF, |
| [RESOLV_CONF_STUB] = PRIVATE_STUB_RESOLV_CONF, |
| [RESOLV_CONF_STATIC] = PRIVATE_STATIC_RESOLV_CONF, |
| }; |
| |
| struct stat system_st; |
| |
| if (stat("/etc/resolv.conf", &system_st) < 0) { |
| if (errno == ENOENT) |
| return RESOLV_CONF_MISSING; |
| |
| return -errno; |
| } |
| |
| for (ResolvConfMode m = 0; m < _RESOLV_CONF_MODE_MAX; m++) { |
| struct stat our_st; |
| |
| if (!table[m]) |
| continue; |
| |
| if (stat(table[m], &our_st) < 0) { |
| if (errno != ENOENT) |
| log_debug_errno(errno, "Failed to stat() %s, ignoring: %m", table[m]); |
| |
| continue; |
| } |
| |
| if (stat_inode_same(&system_st, &our_st)) |
| return m; |
| } |
| |
| return RESOLV_CONF_FOREIGN; |
| } |
| |
| static const char* const resolv_conf_mode_table[_RESOLV_CONF_MODE_MAX] = { |
| [RESOLV_CONF_UPLINK] = "uplink", |
| [RESOLV_CONF_STUB] = "stub", |
| [RESOLV_CONF_STATIC] = "static", |
| [RESOLV_CONF_MISSING] = "missing", |
| [RESOLV_CONF_FOREIGN] = "foreign", |
| }; |
| DEFINE_STRING_TABLE_LOOKUP(resolv_conf_mode, ResolvConfMode); |
