Merge pull request #20559 from tomty89/stub_check_in_get

resolved: filter stub listeners in manager_get_dns_server()

6 files changed, 46 insertions, 34 deletions

diff --git a/src/resolve/resolved-conf.c b/src/resolve/resolved-conf.c
index a4e44f29be..7873c363b3 100644
--- a/src/resolve/resolved-conf.c
+++ b/src/resolve/resolved-conf.c
@@ -35,15 +35,16 @@ static int manager_add_dns_server_by_string(Manager *m, DnsServerType type, cons
         if (r < 0)
                 return r;
 
-        /* Silently filter out 0.0.0.0, 127.0.0.53, 127.0.0.54 (our own stub DNS listener) */
-        if (!dns_server_address_valid(family, &address))
-                return 0;
-
-        /* By default, the port number is determined with the transaction feature level.
+        /* By default, the port number is determined by the transaction feature level.
          * See dns_transaction_port() and dns_server_port(). */
         if (IN_SET(port, 53, 853))
                 port = 0;
 
+        /* Refuse 0.0.0.0, 127.0.0.53, 127.0.0.54 and the rest of our own stub DNS listeners. */
+        if (!dns_server_address_valid(family, &address) ||
+            manager_server_address_is_stub(m, family, &address, port ?: 53))
+                return -ELOOP;
+
         /* Filter out duplicates */
         s = dns_server_find(manager_get_first_dns_server(m, type), family, &address, port, ifindex, server_name);
         if (s) {
@@ -56,7 +57,7 @@ static int manager_add_dns_server_by_string(Manager *m, DnsServerType type, cons
         return dns_server_new(m, NULL, type, NULL, family, &address, port, ifindex, server_name);
 }
 
-int manager_parse_dns_server_string_and_warn(Manager *m, DnsServerType type, const char *string) {
+int manager_parse_dns_server_string_and_warn(Manager *m, DnsServerType type, const char *string, bool ignore_self_quietly) {
         int r;
 
         assert(m);
@@ -66,17 +67,16 @@ int manager_parse_dns_server_string_and_warn(Manager *m, DnsServerType type, con
                 _cleanup_free_ char *word = NULL;
 
                 r = extract_first_word(&string, &word, NULL, 0);
-                if (r < 0)
+                if (r <= 0)
                         return r;
-                if (r == 0)
-                        break;
 
                 r = manager_add_dns_server_by_string(m, type, word);
-                if (r < 0)
+                if (r == -ELOOP)
+                        log_full(ignore_self_quietly ? LOG_DEBUG : LOG_INFO,
+                                 "DNS server string '%s' points to our own listener, ignoring.", word);
+                else if (r < 0)
                         log_warning_errno(r, "Failed to add DNS server address '%s', ignoring: %m", word);
         }
-
-        return 0;
 }
 
 static int manager_add_search_domain_by_string(Manager *m, const char *domain) {
@@ -121,17 +121,13 @@ int manager_parse_search_domains_and_warn(Manager *m, const char *string) {
                 _cleanup_free_ char *word = NULL;
 
                 r = extract_first_word(&string, &word, NULL, EXTRACT_UNQUOTE);
-                if (r < 0)
+                if (r <= 0)
                         return r;
-                if (r == 0)
-                        break;
 
                 r = manager_add_search_domain_by_string(m, word);
                 if (r < 0)
                         log_warning_errno(r, "Failed to add search domain '%s', ignoring: %m", word);
         }
-
-        return 0;
 }
 
 int config_parse_dns_servers(
@@ -159,7 +155,7 @@ int config_parse_dns_servers(
                 dns_server_unlink_all(manager_get_first_dns_server(m, ltype));
         else {
                 /* Otherwise, add to the list */
-                r = manager_parse_dns_server_string_and_warn(m, ltype, rvalue);
+                r = manager_parse_dns_server_string_and_warn(m, ltype, rvalue, false);
                 if (r < 0) {
                         log_syntax(unit, LOG_WARNING, filename, line, r,
                                    "Failed to parse DNS server string '%s', ignoring.", rvalue);
@@ -167,8 +163,7 @@ int config_parse_dns_servers(
                 }
         }
 
-        /* If we have a manual setting, then we stop reading
-         * /etc/resolv.conf */
+        /* If we have a manual setting, then we stop reading /etc/resolv.conf */
         if (ltype == DNS_SERVER_SYSTEM)
                 m->read_resolv_conf = false;
         if (ltype == DNS_SERVER_FALLBACK)
@@ -210,8 +205,7 @@ int config_parse_search_domains(
                 }
         }
 
-        /* If we have a manual setting, then we stop reading
-         * /etc/resolv.conf */
+        /* If we have a manual setting, then we stop reading /etc/resolv.conf */
         m->read_resolv_conf = false;
 
         return 0;
@@ -493,7 +487,7 @@ int manager_parse_config_file(Manager *m) {
                 return r;
 
         if (m->need_builtin_fallbacks) {
-                r = manager_parse_dns_server_string_and_warn(m, DNS_SERVER_FALLBACK, DNS_SERVERS);
+                r = manager_parse_dns_server_string_and_warn(m, DNS_SERVER_FALLBACK, DNS_SERVERS, false);
                 if (r < 0)
                         return r;
         }
diff --git a/src/resolve/resolved-conf.h b/src/resolve/resolved-conf.h
index 07ce2591a9..4639cefbd8 100644
--- a/src/resolve/resolved-conf.h
+++ b/src/resolve/resolved-conf.h
@@ -8,7 +8,7 @@
 int manager_parse_config_file(Manager *m);
 
 int manager_parse_search_domains_and_warn(Manager *m, const char *string);
-int manager_parse_dns_server_string_and_warn(Manager *m, DnsServerType type, const char *string);
+int manager_parse_dns_server_string_and_warn(Manager *m, DnsServerType type, const char *string, bool ignore_self_quietly);
 
 const struct ConfigPerfItem* resolved_gperf_lookup(const char *key, GPERF_LEN_TYPE length);
 const struct ConfigPerfItem* resolved_dnssd_gperf_lookup(const char *key, GPERF_LEN_TYPE length);
diff --git a/src/resolve/resolved-dns-server.c b/src/resolve/resolved-dns-server.c
index 7d180378b6..cd755b13d4 100644
--- a/src/resolve/resolved-dns-server.c
+++ b/src/resolve/resolved-dns-server.c
@@ -875,9 +875,18 @@ DnsServer *manager_get_dns_server(Manager *m) {
         manager_read_resolv_conf(m);
 
         /* If no DNS server was chosen so far, pick the first one */
-        if (!m->current_dns_server)
+        if (!m->current_dns_server ||
+            /* In case m->current_dns_server != m->dns_servers */
+            manager_server_is_stub(m, m->current_dns_server))
                 manager_set_dns_server(m, m->dns_servers);
 
+        while (m->current_dns_server &&
+               manager_server_is_stub(m, m->current_dns_server)) {
+                manager_next_dns_server(m, NULL);
+                if (m->current_dns_server == m->dns_servers)
+                        manager_set_dns_server(m, NULL);
+        }
+
         if (!m->current_dns_server) {
                 bool found = false;
 
diff --git a/src/resolve/resolved-manager.c b/src/resolve/resolved-manager.c
index 6b32ee4cf0..223ef36691 100644
--- a/src/resolve/resolved-manager.c
+++ b/src/resolve/resolved-manager.c
@@ -1620,30 +1620,37 @@ bool manager_next_dnssd_names(Manager *m) {
         return tried;
 }
 
-bool manager_server_is_stub(Manager *m, DnsServer *s) {
+bool manager_server_address_is_stub(Manager *m, int family, const union in_addr_union *address, uint16_t port) {
         DnsStubListenerExtra *l;
 
         assert(m);
-        assert(s);
+        assert(address);
 
         /* Safety check: we generally already skip the main stub when parsing configuration. But let's be
          * extra careful, and check here again */
-        if (s->family == AF_INET &&
-            s->address.in.s_addr == htobe32(INADDR_DNS_STUB) &&
-            dns_server_port(s) == 53)
+        if (family == AF_INET &&
+            address->in.s_addr == htobe32(INADDR_DNS_STUB) &&
+            port == 53)
                 return true;
 
         /* Main reason to call this is to check server data against the extra listeners, and filter things
          * out. */
         ORDERED_SET_FOREACH(l, m->dns_extra_stub_listeners)
-                if (s->family == l->family &&
-                    in_addr_equal(s->family, &s->address, &l->address) &&
-                    dns_server_port(s) == dns_stub_listener_extra_port(l))
+                if (family == l->family &&
+                    in_addr_equal(family, address, &l->address) &&
+                    port == dns_stub_listener_extra_port(l))
                         return true;
 
         return false;
 }
 
+bool manager_server_is_stub(Manager *m, DnsServer *s) {
+        assert(m);
+        assert(s);
+
+        return manager_server_address_is_stub(m, s->family, &s->address, dns_server_port(s));
+}
+
 int socket_disable_pmtud(int fd, int af) {
         int r;
 
diff --git a/src/resolve/resolved-manager.h b/src/resolve/resolved-manager.h
index 35e0068a83..e969738978 100644
--- a/src/resolve/resolved-manager.h
+++ b/src/resolve/resolved-manager.h
@@ -207,6 +207,7 @@ void manager_cleanup_saved_user(Manager *m);
 
 bool manager_next_dnssd_names(Manager *m);
 
+bool manager_server_address_is_stub(Manager *m, int family, const union in_addr_union *address, uint16_t port);
 bool manager_server_is_stub(Manager *m, DnsServer *s);
 
 int socket_disable_pmtud(int fd, int af);
diff --git a/src/resolve/resolved-resolv-conf.c b/src/resolve/resolved-resolv-conf.c
index 100894d6b2..e9785ab964 100644
--- a/src/resolve/resolved-resolv-conf.c
+++ b/src/resolve/resolved-resolv-conf.c
@@ -143,7 +143,8 @@ int manager_read_resolv_conf(Manager *m) {
 
                 a = first_word(l, "nameserver");
                 if (a) {
-                        r = manager_parse_dns_server_string_and_warn(m, DNS_SERVER_SYSTEM, a);
+                        r = manager_parse_dns_server_string_and_warn(m, DNS_SERVER_SYSTEM, a,
+                                                                     true /* don't warn about loops to our own stub listeners */);
                         if (r < 0)
                                 log_warning_errno(r, "Failed to parse DNS server address '%s', ignoring.", a);