Merge pull request #9742 from yuwata/workaround-9718

resolve: add option to toggle reading /etc/hosts

man/resolved.conf.xml

@@ -227,10 +227,10 @@
 
       <varlistentry>
         <term><varname>Cache=</varname></term>
-        <listitem><para>Takes a boolean argument. If "yes" (the default), resolving a domain name which already got
-        queried earlier will return the previous result as long as it is still valid, and thus does not result in a new
-        network request. Be aware that turning off caching comes at a performance penalty, which is particularly
-        high when DNSSEC is used.</para>
+        <listitem><para>Takes a boolean argument. If <literal>yes</literal> (the default), resolving a domain name
+        which already got queried earlier will return the previous result as long as it is still valid, and thus does
+        not result in a new network request. Be aware that turning off caching comes at a performance penalty, which
+        is particularly high when DNSSEC is used.</para>
 
         <para>Note that caching is turned off implicitly if the configured DNS server is on a host-local IP address
         (such as 127.0.0.1 or ::1), in order to avoid duplicate local caching.</para></listitem>
@@ -248,6 +248,13 @@
         in use.</para></listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term><varname>ReadEtcHosts=</varname></term>
+        <listitem><para>Takes a boolean argument. If <literal>yes</literal> (the default), the DNS stub resolver will read
+        <filename>/etc/hosts</filename>, and try to resolve hosts or address by using the entries in the file before
+        sending query to DNS servers.</para></listitem>
+      </varlistentry>
+
     </variablelist>
   </refsect1>
 

src/resolve/resolved-etc-hosts.c

@@ -236,7 +236,7 @@ static int parse_line(Manager *m, unsigned nr, const char *line) {
         return r;
 }
 
-int manager_etc_hosts_read(Manager *m) {
+static int manager_etc_hosts_read(Manager *m) {
         _cleanup_fclose_ FILE *f = NULL;
         char line[LINE_MAX];
         struct stat st;
@@ -324,6 +324,9 @@ int manager_etc_hosts_lookup(Manager *m, DnsQuestion* q, DnsAnswer **answer) {
         assert(q);
         assert(answer);
 
+        if (!m->read_etc_hosts)
+                return 0;
+
         r = manager_etc_hosts_read(m);
         if (r < 0)
                 return r;

src/resolve/resolved-etc-hosts.h

@@ -6,5 +6,4 @@
 #include "resolved-dns-answer.h"
 
 void manager_etc_hosts_flush(Manager *m);
-int manager_etc_hosts_read(Manager *m);
 int manager_etc_hosts_lookup(Manager *m, DnsQuestion* q, DnsAnswer **answer);

src/resolve/resolved-gperf.gperf

@@ -26,3 +26,4 @@ Resolve.DNSSEC,          config_parse_dnssec_mode,            0,
 Resolve.DNSOverTLS,      config_parse_dns_over_tls_mode,      0,                   offsetof(Manager, dns_over_tls_mode)
 Resolve.Cache,           config_parse_bool,                   0,                   offsetof(Manager, enable_cache)
 Resolve.DNSStubListener, config_parse_dns_stub_listener_mode, 0,                   offsetof(Manager, dns_stub_listener_mode)
+Resolve.ReadEtcHosts,    config_parse_bool,                   0,                   offsetof(Manager, read_etc_hosts)

src/resolve/resolved-manager.c

@@ -581,6 +581,7 @@ int manager_new(Manager **ret) {
         m->read_resolv_conf = true;
         m->need_builtin_fallbacks = true;
         m->etc_hosts_last = m->etc_hosts_mtime = USEC_INFINITY;
+        m->read_etc_hosts = true;
 
         r = dns_trust_anchor_load(&m->trust_anchor);
         if (r < 0)

src/resolve/resolved-manager.h

@@ -117,6 +117,7 @@ struct Manager {
         Set* etc_hosts_by_address;
         Hashmap* etc_hosts_by_name;
         usec_t etc_hosts_last, etc_hosts_mtime;
+        bool read_etc_hosts;
 
         /* Local DNS stub on 127.0.0.53:53 */
         int dns_stub_udp_fd;

src/resolve/resolved.conf.in

@@ -21,3 +21,4 @@
 #DNSOverTLS=@DEFAULT_DNS_OVER_TLS_MODE@
 #Cache=yes
 #DNSStubListener=udp
+#ReadEtcHosts=yes