diff options
Diffstat (limited to 'src/grp-resolve/systemd-resolved/resolved-resolv-conf.c')
| -rw-r--r-- | src/grp-resolve/systemd-resolved/resolved-resolv-conf.c | 277 |
1 files changed, 277 insertions, 0 deletions
diff --git a/src/grp-resolve/systemd-resolved/resolved-resolv-conf.c b/src/grp-resolve/systemd-resolved/resolved-resolv-conf.c new file mode 100644 index 0000000000..5cc79a0040 --- /dev/null +++ b/src/grp-resolve/systemd-resolved/resolved-resolv-conf.c @@ -0,0 +1,277 @@ +/*** + 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 "systemd-basic/alloc-util.h" +#include "systemd-basic/fd-util.h" +#include "systemd-basic/fileio-label.h" +#include "systemd-basic/fileio.h" +#include "systemd-basic/ordered-set.h" +#include "systemd-basic/string-util.h" +#include "systemd-basic/strv.h" +#include "systemd-shared/dns-domain.h" + +#include "resolved-conf.h" +#include "resolved-resolv-conf.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_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("# 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_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" + "# 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 resolv.conf(5) in a different way,\n" + "# replace this symlink by a static file or a different symlink.\n#\n" + "# See 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); +} + +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; +} |