CDRIVER-721 mongoc_client_destroy crash after connection fails

Undo two bad changes introduced while fixing CDRIVER-695, and add
another safety check in _mongoc_cluster_node_destroy.

Author: ajdavis

src/mongoc/mongoc-cluster.c

@@ -320,7 +320,6 @@ _mongoc_cluster_node_destroy (mongoc_cluster_node_t *node)
    ENTRY;
 
    ALWAYS_ASSERT(node);
-   ALWAYS_ASSERT(node->valid);
 
    if (node->stream) {
       mongoc_stream_close(node->stream);
@@ -572,9 +571,12 @@ _mongoc_cluster_destroy (mongoc_cluster_t *cluster) /* INOUT */
 
    mongoc_uri_destroy (cluster->uri);
 
-   for (i = 0; i < cluster->nodes_len; i++) {
-      if (cluster->nodes[i].stream) {
-         _mongoc_cluster_node_destroy (&cluster->nodes [i]);
+   /* nodes should never be NULL if nodes_len > 0, but check anyway */
+   if (cluster->nodes) {
+      for (i = 0; i < cluster->nodes_len; i++) {
+         if (cluster->nodes[i].stream) {
+            _mongoc_cluster_node_destroy (&cluster->nodes[i]);
+         }
       }
    }
 
@@ -2094,8 +2096,8 @@ _mongoc_cluster_reconnect_replica_set (mongoc_cluster_t *cluster,
    mongoc_list_t *liter;
    int32_t ping;
    const char *replSet;
-   int i;
-   int j;
+   uint32_t i;
+   uint32_t j;
    bool rval = false;
 
    ENTRY;
@@ -2205,6 +2207,7 @@ _mongoc_cluster_reconnect_replica_set (mongoc_cluster_t *cluster,
    /* reinitialize nodes with same length as peer list. */
    for (liter = list, i = 0; liter; liter = liter->next, i++) {}
    cluster->nodes = bson_realloc (cluster->nodes, sizeof (*cluster->nodes) * i);
+   cluster->nodes_len = i;
 
    for (j = 0; j < i; j++) {
       _mongoc_cluster_node_init (&cluster->nodes[j]);
@@ -2284,7 +2287,7 @@ _mongoc_cluster_reconnect_replica_set (mongoc_cluster_t *cluster,
 
       cluster->nodes[i].valid = true;
       i++;
-      cluster->nodes_len = (uint32_t) i;
+      cluster->nodes_len = i;
    }
 
    _mongoc_list_foreach(list, (void(*)(void*,void*))bson_free, NULL);

tests/test-mongoc-client.c

@@ -455,6 +455,54 @@ test_mongoc_client_preselect (void)
 }
 
 
+static void
+test_unavailable_seeds(void)
+{
+   mongoc_client_t *client;
+   mongoc_collection_t *collection;
+   mongoc_cursor_t *cursor;
+   bson_t query = BSON_INITIALIZER;
+   const bson_t *doc;
+   
+   const char* uri_strs[] = {
+      "mongodb://a:1/?connectTimeoutMS=1",
+      "mongodb://a:1,a:2/?connectTimeoutMS=1",
+      "mongodb://a:1,a:2/?replicaSet=r&connectTimeoutMS=1",
+      "mongodb://u:p@a:1/?connectTimeoutMS=1",
+      "mongodb://u:p@a:1,a:2/?connectTimeoutMS=1",
+      "mongodb://u:p@a:1,a:2/?replicaSet=r&connectTimeoutMS=1",
+   };
+
+   int i;
+
+   /* hardcode the number of error messages we have to suppress */
+   for (i = 0; i < 18; i++) {
+      suppress_one_message ();
+   }
+
+   for (i = 0; i < (sizeof(uri_strs) / sizeof(const char *)); i++) {
+      client = mongoc_client_new (uri_strs[i]);
+      assert (client);
+
+      collection = mongoc_client_get_collection (client, "test", "test");
+      cursor = mongoc_collection_find (collection,
+                                       MONGOC_QUERY_NONE,
+                                       0,
+                                       0,
+                                       0,
+                                       &query,
+                                       NULL,
+                                       NULL);
+
+      assert (! mongoc_cursor_next (cursor, &doc));
+
+      mongoc_cursor_destroy (cursor);
+      mongoc_collection_destroy (collection);
+      mongoc_client_destroy (client);
+   }
+}
+
+
 static void
 test_exhaust_cursor (void)
 {
@@ -693,6 +741,7 @@ test_client_install (TestSuite *suite)
    TestSuite_Add (suite, "/Client/command", test_mongoc_client_command);
    TestSuite_Add (suite, "/Client/command_secondary", test_mongoc_client_command_secondary);
    TestSuite_Add (suite, "/Client/preselect", test_mongoc_client_preselect);
+   TestSuite_Add (suite, "/Client/unavailable_seeds", test_unavailable_seeds);
    TestSuite_Add (suite, "/Client/exhaust_cursor", test_exhaust_cursor);
    TestSuite_Add (suite, "/Client/server_status", test_server_status);
 }