Protect pooled clients against later API changes

Author: alcaeus

src/libmongoc/src/mongoc/mongoc-client-pool.c

@@ -245,6 +245,7 @@ _initialize_new_client (mongoc_client_pool_t *pool, mongoc_client_t *client)
       client, &pool->apm_callbacks, pool->apm_context);
 
    client->api = mongoc_server_api_copy (pool->api);
+   client->api_set = true;
 
 #ifdef MONGOC_ENABLE_SSL
    if (pool->ssl_opts_set) {
@@ -528,6 +529,14 @@ mongoc_client_pool_set_server_api (mongoc_client_pool_t *pool,
       return false;
    }
 
+   if (mongoc_client_pool_get_size (pool)) {
+      bson_set_error (error,
+                      MONGOC_ERROR_POOL,
+                      MONGOC_ERROR_POOL_API_TOO_LATE,
+                      "Cannot set server api after a client has been created");
+      return false;
+   }
+
    pool->api = mongoc_server_api_copy (api);
    _mongoc_topology_scanner_set_server_api (pool->topology->scanner, api);
    return true;

src/libmongoc/src/mongoc/mongoc-client-private.h

@@ -119,6 +119,7 @@ struct _mongoc_client_t {
    bool error_api_set;
 
    mongoc_server_api_t *api;
+   bool api_set;
 
    /* mongoc_client_session_t's in use, to look up lsids and clusterTimes */
    mongoc_set_t *client_sessions;

src/libmongoc/src/mongoc/mongoc-client.c

@@ -3105,7 +3105,7 @@ mongoc_client_set_server_api (mongoc_client_t *client,
    BSON_ASSERT_PARAM (client);
    BSON_ASSERT_PARAM (api);
 
-   if (client->api) {
+   if (client->api_set) {
       bson_set_error (error,
                       MONGOC_ERROR_CLIENT,
                       MONGOC_ERROR_CLIENT_API_ALREADY_SET,
@@ -3114,6 +3114,7 @@ mongoc_client_set_server_api (mongoc_client_t *client,
    }
 
    client->api = mongoc_server_api_copy (api);
+   client->api_set = true;
    _mongoc_topology_scanner_set_server_api (client->topology->scanner, api);
    return true;
 }

src/libmongoc/src/mongoc/mongoc-error.h

@@ -130,7 +130,8 @@ typedef enum {
 
    /* An error related to server version api */
    MONGOC_ERROR_CLIENT_API_ALREADY_SET,
-   MONGOC_ERROR_POOL_API_ALREADY_SET
+   MONGOC_ERROR_POOL_API_ALREADY_SET,
+   MONGOC_ERROR_POOL_API_TOO_LATE
 } mongoc_error_code_t;
 
 MONGOC_EXPORT (bool)

src/libmongoc/tests/test-mongoc-versioned-api.c

@@ -135,6 +135,43 @@ _test_mongoc_server_api_client_pool (void)
    mongoc_uri_destroy (uri);
 }
 
+static void
+_test_mongoc_server_api_client_pool_once (void)
+{
+   mongoc_uri_t *uri;
+   mongoc_client_pool_t *pool;
+   mongoc_client_t *client;
+   mongoc_server_api_t *api;
+   bson_error_t error;
+
+   uri = mongoc_uri_new ("mongodb://localhost");
+   pool = mongoc_client_pool_new (uri);
+
+   api = mongoc_server_api_new (MONGOC_SERVER_API_V1);
+
+   client = mongoc_client_pool_pop (pool);
+   BSON_ASSERT (!client->api);
+
+   /* Cannot change server API once a client has been popped. */
+   ASSERT (!mongoc_client_pool_set_server_api (pool, api, &error));
+   ASSERT_ERROR_CONTAINS (
+      error,
+      MONGOC_ERROR_POOL,
+      MONGOC_ERROR_POOL_API_TOO_LATE,
+      "Cannot set server api after a client has been created");
+
+   ASSERT (!mongoc_client_set_server_api (client, api, &error));
+   ASSERT_ERROR_CONTAINS (error,
+                          MONGOC_ERROR_CLIENT,
+                          MONGOC_ERROR_CLIENT_API_ALREADY_SET,
+                          "Cannot set server api more than once");
+
+   mongoc_client_pool_push (pool, client);
+   mongoc_client_pool_destroy (pool);
+   mongoc_server_api_destroy (api);
+   mongoc_uri_destroy (uri);
+}
+
 void
 test_client_versioned_api_install (TestSuite *suite)
 {
@@ -144,6 +181,9 @@ test_client_versioned_api_install (TestSuite *suite)
       suite, "/VersionedApi/client", _test_mongoc_server_api_client);
    TestSuite_Add (
       suite, "/VersionedApi/client_pool", _test_mongoc_server_api_client_pool);
+   TestSuite_Add (suite,
+                  "/VersionedApi/client_pool_once",
+                  _test_mongoc_server_api_client_pool_once);
    TestSuite_Add (suite, "/VersionedApi/copy", _test_mongoc_server_api_copy);
    TestSuite_Add (
       suite, "/VersionedApi/setters", _test_mongoc_server_api_setters);