Implement option to turn off DNS cache use on a client port

(This is part 2 of making DNS cache use enabled/disabled on a
per-client port basis.  This implements the CacheIPv[46]DNS options,
but not the UseCachedIPv[46] ones.)

src/or/addressmap.c

@@ -335,7 +335,9 @@ addressmap_match_superdomains(char *address)
  * was a .exit.
  */
 int
-addressmap_rewrite(char *address, size_t maxlen, time_t *expires_out,
+addressmap_rewrite(char *address, size_t maxlen,
+                   unsigned flags,
+                   time_t *expires_out,
                    addressmap_entry_source_t *exit_source_out)
 {
   addressmap_entry_t *ent;
@@ -368,6 +370,16 @@ addressmap_rewrite(char *address, size_t maxlen, time_t *expires_out,
       goto done;
     }
 
+    if (ent && ent->source == ADDRMAPSRC_DNS) {
+      sa_family_t f;
+      tor_addr_t tmp;
+      f = tor_addr_parse(&tmp, ent->new_address);
+      if (f == AF_INET && !(flags & AMR_FLAG_USE_IPV4_DNS))
+        goto done;
+      else if (f == AF_INET6 && !(flags & AMR_FLAG_USE_IPV6_DNS))
+        goto done;
+    }
+
     if (ent->dst_wildcard && !exact_match) {
       strlcat(address, ".", maxlen);
       strlcat(address, ent->new_address, maxlen);
@@ -409,11 +421,22 @@ addressmap_rewrite(char *address, size_t maxlen, time_t *expires_out,
  * *<b>expires_out</b> to the expiry time of the result, or to <b>time_max</b>
  * if the result does not expire. */
 int
-addressmap_rewrite_reverse(char *address, size_t maxlen, time_t *expires_out)
+addressmap_rewrite_reverse(char *address, size_t maxlen, unsigned flags,
+                           time_t *expires_out)
 {
   char *s, *cp;
   addressmap_entry_t *ent;
   int r = 0;
+  {
+    sa_family_t f;
+    tor_addr_t tmp;
+    f = tor_addr_parse(&tmp, address);
+    if (f == AF_INET && !(flags & AMR_FLAG_USE_IPV4_DNS))
+      return 0;
+    else if (f == AF_INET6 && !(flags & AMR_FLAG_USE_IPV6_DNS))
+      return 0;
+  }
+
   tor_asprintf(&s, "REVERSE[%s]", address);
   ent = strmap_get(addressmap, s);
   if (ent) {

src/or/addressmap.h

@@ -14,9 +14,12 @@ void addressmap_clean(time_t now);
 void addressmap_clear_configured(void);
 void addressmap_clear_transient(void);
 void addressmap_free_all(void);
-int addressmap_rewrite(char *address, size_t maxlen, time_t *expires_out,
+#define AMR_FLAG_USE_IPV4_DNS (1u<<0)
+#define AMR_FLAG_USE_IPV6_DNS (1u<<1)
+int addressmap_rewrite(char *address, size_t maxlen, unsigned flags,
+                       time_t *expires_out,
                        addressmap_entry_source_t *exit_source_out);
-int addressmap_rewrite_reverse(char *address, size_t maxlen,
+int addressmap_rewrite_reverse(char *address, size_t maxlen, unsigned flags,
                                time_t *expires_out);
 int addressmap_have_mapping(const char *address, int update_timeout);
 

src/or/connection_edge.c

@@ -952,8 +952,14 @@ connection_ap_handshake_rewrite_and_attach(entry_connection_t *conn,
   }
 
   if (socks->command == SOCKS_COMMAND_RESOLVE_PTR) {
+    unsigned rewrite_flags = 0;
+    if (conn->use_cached_ipv4_answers)
+      rewrite_flags |= AMR_FLAG_USE_IPV4_DNS;
+    if (conn->use_cached_ipv6_answers)
+      rewrite_flags |= AMR_FLAG_USE_IPV6_DNS;
+
     if (addressmap_rewrite_reverse(socks->address, sizeof(socks->address),
-                                   &map_expires)) {
+                                   rewrite_flags, &map_expires)) {
       char *result = tor_strdup(socks->address);
       /* remember _what_ is supposed to have been resolved. */
       tor_snprintf(socks->address, sizeof(socks->address), "REVERSE[%s]",
@@ -984,8 +990,13 @@ connection_ap_handshake_rewrite_and_attach(entry_connection_t *conn,
     }
   } else if (!automap) {
     /* For address map controls, remap the address. */
+    unsigned rewrite_flags = 0;
+    if (conn->use_cached_ipv4_answers)
+      rewrite_flags |= AMR_FLAG_USE_IPV4_DNS;
+    if (conn->use_cached_ipv6_answers)
+      rewrite_flags |= AMR_FLAG_USE_IPV6_DNS;
     if (addressmap_rewrite(socks->address, sizeof(socks->address),
-                           &map_expires, &exit_source)) {
+                           rewrite_flags, &map_expires, &exit_source)) {
       control_event_stream_status(conn, STREAM_EVENT_REMAP,
                                   REMAP_STREAM_SOURCE_CACHE);
     }

src/or/relay.c

@@ -758,11 +758,18 @@ connection_ap_process_end_not_open(
           policies_set_node_exitpolicy_to_reject_all(exitrouter);
         }
         /* rewrite it to an IP if we learned one. */
+        {
+          unsigned rewrite_flags = 0;
+          if (conn->use_cached_ipv4_answers)
+            rewrite_flags |= AMR_FLAG_USE_IPV4_DNS;
+          if (conn->use_cached_ipv6_answers)
+            rewrite_flags |= AMR_FLAG_USE_IPV6_DNS;
           if (addressmap_rewrite(conn->socks_request->address,
                                  sizeof(conn->socks_request->address),
-                               NULL, NULL)) {
+                                 rewrite_flags, NULL, NULL)) {
             control_event_stream_status(conn, STREAM_EVENT_REMAP, 0);
           }
+        }
         if (conn->chosen_exit_optional ||
             conn->chosen_exit_retries) {
           /* stop wanting a specific exit */

src/test/test_config.c

@@ -42,6 +42,11 @@ test_config_addressmap(void *arg)
   config_get_lines(buf, &(get_options_mutable()->AddressMap), 0);
   config_register_addressmaps(get_options());
 
+/* Use old interface for now, so we don't need to rewrite the unit tests */
+#define addressmap_rewrite(a,s,eo,ao)                                   \
+  addressmap_rewrite((a),(s),AMR_FLAG_USE_IPV4_DNS|AMR_FLAG_USE_IPV6_DNS, \
+                     (eo),(ao))
+
   /* MapAddress .invalidwildcard.com .torserver.exit  - no match */
   strlcpy(address, "www.invalidwildcard.com", sizeof(address));
   test_assert(!addressmap_rewrite(address, sizeof(address), &expires, NULL));
@@ -158,6 +163,8 @@ test_config_addressmap(void *arg)
   strlcpy(address, "www.torproject.org", sizeof(address));
   test_assert(!addressmap_rewrite(address, sizeof(address), &expires, NULL));
 
+#undef addressmap_rewrite
+
  done:
   ;
 }