/*** This file is part of systemd. Copyright 2014 Tom Gundersen 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 . ***/ #include #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(PRIVATE_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 (IN_SET(*l, '#', ';')) 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); } } 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) { assert(s); assert(f); assert(count); if (!dns_server_string(s)) { log_warning("Our of memory, or invalid DNS address. Ignoring server."); return; } /* Check if the DNS server is limited to particular domains; * 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) */ if (dns_server_limited_domains(s)) { log_debug("DNS server %s has route-only domains, not using as global name server", dns_server_string(s)); return; } if (*count == MAXNS) fputs_unlocked("# 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_unlocked("search", f); ORDERED_SET_FOREACH(domain, domains, i) { if (++count > MAXDNSRCH) { fputs_unlocked("\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); break; } fputc_unlocked(' ', f); fputs_unlocked(domain, f); } fputs_unlocked("\n", f); } static int write_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); if (ordered_set_isempty(dns)) fputs_unlocked("# 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); } 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; 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_RESOLV_CONF, PRIVATE_RESOLV_CONF, &f, &temp_path); if (r < 0) return log_warning_errno(r, "Failed to open private resolv.conf file for writing: %m"); (void) fchmod(fileno(f), 0644); r = write_resolv_conf_contents(f, 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) { r = log_error_errno(errno, "Failed to move private resolv.conf file into place: %m"); goto fail; } return 0; fail: (void) unlink(PRIVATE_RESOLV_CONF); (void) unlink(temp_path); return r; }