Resolution override

include/aws/mqtt/client.h

@@ -386,6 +386,14 @@ int aws_mqtt_client_connection_set_http_proxy_options(
     struct aws_mqtt_client_connection *connection,
     struct aws_http_proxy_options *proxy_options);
 
+/**
+ * Set host resolution ooptions for the connection.
+ */
+AWS_MQTT_API
+int aws_mqtt_client_connection_set_host_resolution_options(
+    struct aws_mqtt_client_connection *connection,
+    struct aws_host_resolution_config *host_resolution_config);
+
 /**
  * Sets the minimum and maximum reconnect timeouts.
  *

include/aws/mqtt/private/client_impl.h

@@ -192,6 +192,7 @@ struct aws_mqtt_client_connection {
     struct aws_socket_options socket_options;
     struct aws_http_proxy_config *http_proxy_config;
     struct aws_event_loop *loop;
+    struct aws_host_resolution_config host_resolution_config;
 
     /* Connect parameters */
     struct aws_byte_buf client_id;

include/aws/mqtt/private/v5/mqtt5_options_storage.h

@@ -12,6 +12,7 @@
 #include <aws/common/logging.h>
 #include <aws/common/ref_count.h>
 #include <aws/http/proxy.h>
+#include <aws/io/host_resolver.h>
 #include <aws/io/retry_strategy.h>
 #include <aws/io/socket.h>
 #include <aws/io/tls_channel_handler.h>
@@ -176,6 +177,8 @@ struct aws_mqtt5_client_options_storage {
 
     aws_mqtt5_client_termination_completion_fn *client_termination_handler;
     void *client_termination_handler_user_data;
+
+    struct aws_host_resolution_config host_resolution_override;
 };
 
 AWS_EXTERN_C_BEGIN

include/aws/mqtt/v5/mqtt5_client.h

@@ -21,8 +21,8 @@
 
 struct aws_allocator;
 struct aws_client_bootstrap;
+struct aws_host_resolution_config;
 struct aws_http_message;
-struct aws_input_stream;
 struct aws_mqtt5_client;
 struct aws_mqtt5_client_lifecycle_event;
 struct aws_tls_connection_options;
@@ -655,6 +655,12 @@ struct aws_mqtt5_client_options {
      */
     aws_mqtt5_client_termination_completion_fn *client_termination_handler;
     void *client_termination_handler_user_data;
+
+    /**
+     * Options to override aspects of DNS resolution.  If unspecified, use a default that matches the regular
+     * configuration but changes the refresh frequency to a value that prevents DNS pinging.
+     */
+    struct aws_host_resolution_config *host_resolution_override;
 };
 
 AWS_EXTERN_C_BEGIN

source/client.c

@@ -888,6 +888,10 @@ struct aws_mqtt_client_connection *aws_mqtt_client_connection_new(struct aws_mqt
 
     connection->loop = aws_event_loop_group_get_next_loop(client->bootstrap->event_loop_group);
 
+    connection->host_resolution_config = aws_host_resolver_init_default_resolution_config();
+    connection->host_resolution_config.resolve_frequency_ns =
+        aws_timestamp_convert(connection->reconnect_timeouts.max_sec, AWS_TIMESTAMP_SECS, AWS_TIMESTAMP_NANOS, NULL);
+
     /* Initialize the handler */
     connection->handler.alloc = connection->allocator;
     connection->handler.vtable = aws_mqtt_get_client_channel_vtable();
@@ -1195,6 +1199,15 @@ int aws_mqtt_client_connection_set_http_proxy_options(
     return connection->http_proxy_config != NULL ? AWS_OP_SUCCESS : AWS_OP_ERR;
 }
 
+int aws_mqtt_client_connection_set_host_resolution_options(
+    struct aws_mqtt_client_connection *connection,
+    struct aws_host_resolution_config *host_resolution_config) {
+
+    connection->host_resolution_config = *host_resolution_config;
+
+    return AWS_OP_SUCCESS;
+}
+
 static void s_on_websocket_shutdown(struct aws_websocket *websocket, int error_code, void *user_data) {
     struct aws_mqtt_client_connection *connection = user_data;
 

source/v5/mqtt5_client.c

@@ -939,7 +939,7 @@ void s_websocket_transform_complete_task_fn(struct aws_task *task, void *arg, en
             .on_connection_setup = s_on_websocket_setup,
             .on_connection_shutdown = s_on_websocket_shutdown,
             .requested_event_loop = client->loop,
-        };
+            .host_resolution_config = &client->config->host_resolution_override};
 
         if (client->config->http_proxy_config != NULL) {
             websocket_options.proxy_options = &client->config->http_proxy_options;
@@ -1055,6 +1055,7 @@ static void s_change_current_state_to_connecting(struct aws_mqtt5_client *client
         channel_options.shutdown_callback = &s_mqtt5_client_shutdown;
         channel_options.user_data = client;
         channel_options.requested_event_loop = client->loop;
+        channel_options.host_resolution_override_config = &client->config->host_resolution_override;
 
         if (client->config->http_proxy_config == NULL) {
             result = (*client->vtable->client_bootstrap_new_socket_channel_fn)(&channel_options);

source/v5/mqtt5_options_storage.c

@@ -3956,6 +3956,15 @@ struct aws_mqtt5_client_options_storage *aws_mqtt5_client_options_storage_new(
 
     s_apply_zero_valued_defaults_to_client_options_storage(options_storage);
 
+    /* must do this after zero-valued defaults are applied so that max reconnect is accurate */
+    if (options->host_resolution_override) {
+        options_storage->host_resolution_override = *options->host_resolution_override;
+    } else {
+        options_storage->host_resolution_override = aws_host_resolver_init_default_resolution_config();
+        options_storage->host_resolution_override.resolve_frequency_ns = aws_timestamp_convert(
+            options_storage->max_reconnect_delay_ms, AWS_TIMESTAMP_MILLIS, AWS_TIMESTAMP_NANOS, NULL);
+    }
+
     return options_storage;
 
 error: