Enable H5Fopen to probe list of available VOL connectors when opening a (#182)

file

10 files changed, 479 insertions, 49 deletions

diff --git a/src/H5F.c b/src/H5F.c
index 365decf..d535ffe 100644
--- a/src/H5F.c
+++ b/src/H5F.c
@@ -690,7 +690,7 @@ done:
 static hid_t
 H5F__open_api_common(const char *filename, unsigned flags, hid_t fapl_id, void **token_ptr)
 {
-    H5F_t *               new_file = NULL;             /* File struct for new file                 */
+    void *                new_file = NULL;             /* File struct for new file                 */
     H5P_genplist_t *      plist;                       /* Property list pointer                    */
     H5VL_connector_prop_t connector_prop;              /* Property for VOL connector ID & info     */
     hid_t                 ret_value = H5I_INVALID_HID; /* Return value                             */
@@ -730,8 +730,8 @@ H5F__open_api_common(const char *filename, unsigned flags, hid_t fapl_id, void *
         HGOTO_ERROR(H5E_FILE, H5E_CANTSET, H5I_INVALID_HID, "can't set VOL connector info in API context")
 
     /* Open the file through the VOL layer */
-    if (NULL == (new_file = (H5F_t *)H5VL_file_open(&connector_prop, filename, flags, fapl_id,
-                                                    H5P_DATASET_XFER_DEFAULT, token_ptr)))
+    if (NULL == (new_file = H5VL_file_open(&connector_prop, filename, flags, fapl_id,
+                                           H5P_DATASET_XFER_DEFAULT, token_ptr)))
         HGOTO_ERROR(H5E_FILE, H5E_CANTOPENFILE, H5I_INVALID_HID, "unable to open file")
 
     /* Get an ID for the file */
diff --git a/src/H5PLint.c b/src/H5PLint.c
index 3b9683b..da9e084 100644
--- a/src/H5PLint.c
+++ b/src/H5PLint.c
@@ -253,7 +253,7 @@ H5PL_load(H5PL_type_t type, const H5PL_key_t *key)
 
     /* Search in the table of already loaded plugin libraries */
     if (H5PL__find_plugin_in_cache(&search_params, &found, &plugin_info) < 0)
-        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, NULL, "search in plugin cache  failed")
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, NULL, "search in plugin cache failed")
 
     /* If not found, try iterating through the path table to find an appropriate plugin */
     if (!found)
@@ -293,12 +293,14 @@ done:
 H5_GCC_DIAG_OFF("pedantic")
 herr_t
 H5PL__open(const char *path, H5PL_type_t type, const H5PL_key_t *key, hbool_t *success,
-           const void **plugin_info)
+           H5PL_type_t *plugin_type, const void **plugin_info)
 {
     H5PL_HANDLE            handle          = NULL;
     H5PL_get_plugin_type_t get_plugin_type = NULL;
     H5PL_get_plugin_info_t get_plugin_info = NULL;
-    herr_t                 ret_value       = SUCCEED;
+    H5PL_type_t            loaded_plugin_type;
+    H5PL_key_t             tmp_key;
+    herr_t                 ret_value = SUCCEED;
 
     FUNC_ENTER_PACKAGE
 
@@ -310,6 +312,8 @@ H5PL__open(const char *path, H5PL_type_t type, const H5PL_key_t *key, hbool_t *s
     /* Initialize out parameters */
     *success     = FALSE;
     *plugin_info = NULL;
+    if (plugin_type)
+        *plugin_type = H5PL_TYPE_ERROR;
 
     /* There are different reasons why a library can't be open, e.g. wrong architecture.
      * If we can't open the library, just return.
@@ -332,11 +336,12 @@ H5PL__open(const char *path, H5PL_type_t type, const H5PL_key_t *key, hbool_t *s
         HGOTO_DONE(SUCCEED)
 
     /* Check the plugin type and return if it doesn't match the one passed in */
-    if (type != (H5PL_type_t)(*get_plugin_type)())
+    loaded_plugin_type = (H5PL_type_t)(*get_plugin_type)();
+    if ((type != H5PL_TYPE_NONE) && (type != loaded_plugin_type))
         HGOTO_DONE(SUCCEED)
 
     /* Get the plugin information */
-    switch (type) {
+    switch (loaded_plugin_type) {
         case H5PL_TYPE_FILTER: {
             const H5Z_class2_t *filter_info;
 
@@ -344,8 +349,16 @@ H5PL__open(const char *path, H5PL_type_t type, const H5PL_key_t *key, hbool_t *s
             if (NULL == (filter_info = (const H5Z_class2_t *)(*get_plugin_info)()))
                 HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, FAIL, "can't get filter info from plugin")
 
+            /* Setup temporary plugin key if one wasn't supplied */
+            if (!key) {
+                tmp_key.id = filter_info->id;
+                key        = &tmp_key;
+            }
+
             /* If the filter IDs match, we're done. Set the output parameters. */
             if (filter_info->id == key->id) {
+                if (plugin_type)
+                    *plugin_type = H5PL_TYPE_FILTER;
                 *plugin_info = (const void *)filter_info;
                 *success     = TRUE;
             }
@@ -360,13 +373,23 @@ H5PL__open(const char *path, H5PL_type_t type, const H5PL_key_t *key, hbool_t *s
             if (NULL == (cls = (const void *)(*get_plugin_info)()))
                 HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, FAIL, "can't get VOL connector info from plugin")
 
+            /* Setup temporary plugin key if one wasn't supplied */
+            if (!key) {
+                tmp_key.vol.kind   = H5VL_GET_CONNECTOR_BY_NAME;
+                tmp_key.vol.u.name = ((const H5VL_class_t *)cls)->name;
+                key                = &tmp_key;
+            }
+
             /* Ask VOL interface if this class is the one we are looking for and is compatible, etc */
             if (H5VL_check_plugin_load(cls, key, success) < 0)
                 HGOTO_ERROR(H5E_PLUGIN, H5E_CANTLOAD, FAIL, "VOL connector compatibility check failed")
 
             /* Check for finding the correct plugin */
-            if (*success)
+            if (*success) {
+                if (plugin_type)
+                    *plugin_type = H5PL_TYPE_VOL;
                 *plugin_info = cls;
+            }
 
             break;
         }
@@ -379,7 +402,7 @@ H5PL__open(const char *path, H5PL_type_t type, const H5PL_key_t *key, hbool_t *s
 
     /* If we found the correct plugin, store it in the cache */
     if (*success)
-        if (H5PL__add_plugin(type, key, handle))
+        if (H5PL__add_plugin(loaded_plugin_type, key, handle))
             HGOTO_ERROR(H5E_PLUGIN, H5E_CANTINSERT, FAIL, "unable to add new plugin to plugin cache")
 
 done:
@@ -409,3 +432,29 @@ H5PL__close(H5PL_HANDLE handle)
 
     FUNC_LEAVE_NOAPI(SUCCEED)
 } /* end H5PL__close() */
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL_iterate
+ *
+ * Purpose:     Iterates over all the available plugins and calls the
+ *              specified callback function on each plugin.
+ *
+ * Return:      H5_ITER_CONT if all plugins are processed successfully
+ *              H5_ITER_STOP if short-circuit success occurs while
+ *                  processing plugins
+ *              H5_ITER_ERROR if an error occurs while processing plugins
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5PL_iterate(H5PL_iterate_type_t iter_type, H5PL_iterate_t iter_op, void *op_data)
+{
+    herr_t ret_value = H5_ITER_CONT;
+
+    FUNC_ENTER_NOAPI(H5_ITER_ERROR)
+
+    ret_value = H5PL__path_table_iterate(iter_type, iter_op, op_data);
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL_iterate() */
diff --git a/src/H5PLpath.c b/src/H5PLpath.c
index ff4dc0e..d566f66 100644
--- a/src/H5PLpath.c
+++ b/src/H5PLpath.c
@@ -62,6 +62,8 @@ static herr_t H5PL__insert_at(const char *path, unsigned int idx);
 static herr_t H5PL__make_space_at(unsigned int idx);
 static herr_t H5PL__replace_at(const char *path, unsigned int idx);
 static herr_t H5PL__expand_path_table(void);
+static herr_t H5PL__path_table_iterate_process_path(const char *plugin_path, H5PL_iterate_type_t iter_type,
+                                                    H5PL_iterate_t iter_op, void *op_data);
 static herr_t H5PL__find_plugin_in_path(const H5PL_search_params_t *search_params, hbool_t *found,
                                         const char *dir, const void **plugin_info);
 
@@ -546,7 +548,220 @@ H5PL__get_path(unsigned int idx)
     return H5PL_paths_g[idx];
 done:
     FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5PL__replace_path() */
+} /* end H5PL__get_path() */
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__path_table_iterate
+ *
+ * Purpose:     Iterates over all the plugins in the plugin path table and
+ *              calls the specified callback function on each plugin found.
+ *
+ * Return:      H5_ITER_CONT if all plugins are processed successfully
+ *              H5_ITER_STOP if short-circuit success occurs while
+ *                  processing plugins
+ *              H5_ITER_ERROR if an error occurs while processing plugins
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5PL__path_table_iterate(H5PL_iterate_type_t iter_type, H5PL_iterate_t iter_op, void *op_data)
+{
+    unsigned int u;
+    herr_t       ret_value = H5_ITER_CONT;
+
+    FUNC_ENTER_PACKAGE
+
+    for (u = 0; (u < H5PL_num_paths_g) && (ret_value == H5_ITER_CONT); u++)
+        ret_value = H5PL__path_table_iterate_process_path(H5PL_paths_g[u], iter_type, iter_op, op_data);
+
+    if (ret_value < 0)
+        HGOTO_ERROR(H5E_PLUGIN, H5E_BADITER, H5_ITER_ERROR, "can't iterate over plugins in plugin path '%s'",
+                    H5PL_paths_g[u]);
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value);
+} /* end H5PL__path_table_iterate() */
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__path_table_iterate_process_path
+ *
+ * Purpose:     Iterates over all the plugins within a single plugin path
+ *              entry in the plugin path table and calls the specified
+ *              callback function on each plugin found. Two function
+ *              definitions are for Unix and Windows.
+ *
+ * Return:      H5_ITER_CONT if all plugins are processed successfully
+ *              H5_ITER_STOP if short-circuit success occurs while
+ *                  processing plugins
+ *              H5_ITER_ERROR if an error occurs while processing plugins
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef H5_HAVE_WIN32_API
+static herr_t
+H5PL__path_table_iterate_process_path(const char *plugin_path, H5PL_iterate_type_t iter_type,
+                                      H5PL_iterate_t iter_op, void *op_data)
+{
+    H5PL_type_t    plugin_type;
+    const void *   plugin_info = NULL;
+    hbool_t        plugin_loaded;
+    char *         path      = NULL;
+    DIR *          dirp      = NULL; /* Directory stream */
+    struct dirent *dp        = NULL; /* Directory entry */
+    herr_t         ret_value = H5_ITER_CONT;
+
+    FUNC_ENTER_STATIC
+
+    HDassert(plugin_path);
+    HDassert(iter_op);
+
+    /* Open the directory */
+    if (!(dirp = HDopendir(plugin_path)))
+        HGOTO_ERROR(H5E_PLUGIN, H5E_OPENERROR, H5_ITER_ERROR, "can't open directory: %s", plugin_path)
+
+    /* Iterate through all entries in the directory */
+    while (NULL != (dp = HDreaddir(dirp))) {
+        /* The library we are looking for should be called libxxx.so... on Unix
+         * or libxxx.xxx.dylib on Mac.
+         */
+#ifndef __CYGWIN__
+        if (!HDstrncmp(dp->d_name, "lib", (size_t)3) &&
+            (HDstrstr(dp->d_name, ".so") || HDstrstr(dp->d_name, ".dylib"))) {
+#else
+        if (!HDstrncmp(dp->d_name, "cyg", (size_t)3) && HDstrstr(dp->d_name, ".dll")) {
+#endif
+
+            hbool_t   plugin_matches;
+            h5_stat_t my_stat;
+            size_t    len;
+
+            /* Allocate & initialize the path name */
+            len = HDstrlen(plugin_path) + HDstrlen(H5PL_PATH_SEPARATOR) + HDstrlen(dp->d_name) + 1 /*\0*/ +
+                  4; /* Extra "+4" to quiet GCC warning - 2019/07/05, QAK */
+
+            if (NULL == (path = (char *)H5MM_calloc(len)))
+                HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, H5_ITER_ERROR, "can't allocate memory for path")
+
+            HDsnprintf(path, len, "%s/%s", plugin_path, dp->d_name);
+
+            /* Get info for directory entry */
+            if (HDstat(path, &my_stat) == -1)
+                HGOTO_ERROR(H5E_FILE, H5E_CANTGET, H5_ITER_ERROR, "can't stat file %s -- error was: %s", path,
+                            HDstrerror(errno))
+
+            /* If it is a directory, skip it */
+            if (S_ISDIR(my_stat.st_mode))
+                continue;
+
+            /* Attempt to open the dynamic library */
+            plugin_type   = H5PL_TYPE_ERROR;
+            plugin_info   = NULL;
+            plugin_loaded = FALSE;
+            if (H5PL__open(path, H5PL_TYPE_NONE, NULL, &plugin_loaded, &plugin_type, &plugin_info) < 0)
+                HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, H5_ITER_ERROR, "failed to open plugin '%s'", path);
+
+            /* Determine if we should process this plugin */
+            plugin_matches = (iter_type == H5PL_ITER_TYPE_ALL) ||
+                             ((iter_type == H5PL_ITER_TYPE_FILTER) && (plugin_type == H5PL_TYPE_FILTER)) ||
+                             ((iter_type == H5PL_ITER_TYPE_VOL) && (plugin_type == H5PL_TYPE_VOL));
+
+            /* If the plugin was successfully loaded, call supplied callback function on plugin */
+            if (plugin_loaded && plugin_matches && (ret_value = iter_op(plugin_type, plugin_info, op_data)))
+                break;
+
+            path = (char *)H5MM_xfree(path);
+        } /* end if */
+    }     /* end while */
+
+    if (ret_value < 0)
+        HERROR(H5E_PLUGIN, H5E_CALLBACK, "callback operator function returned failure");
+
+done:
+    if (dirp)
+        if (HDclosedir(dirp) < 0)
+            HDONE_ERROR(H5E_FILE, H5E_CLOSEERROR, H5_ITER_ERROR, "can't close directory: %s",
+                        HDstrerror(errno))
+
+    path = (char *)H5MM_xfree(path);
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__path_table_iterate_process_path() */
+#else  /* H5_HAVE_WIN32_API */
+static herr_t
+H5PL__path_table_iterate_process_path(const char *plugin_path, H5PL_iterate_type_t iter_type,
+                                      H5PL_iterate_t iter_op, void *op_data)
+{
+    WIN32_FIND_DATAA fdFile;
+    HANDLE           hFind = INVALID_HANDLE_VALUE;
+    H5PL_type_t      plugin_type;
+    const void *     plugin_info = NULL;
+    hbool_t          plugin_loaded;
+    char *           path = NULL;
+    char             service[2048];
+    herr_t           ret_value = H5_ITER_CONT;
+
+    FUNC_ENTER_STATIC
+
+    /* Check args - Just assert on package functions */
+    HDassert(plugin_path);
+    HDassert(iter_op);
+
+    /* Specify a file mask. *.* = We want everything! */
+    HDsprintf(service, "%s\\*.dll", plugin_path);
+    if ((hFind = FindFirstFileA(service, &fdFile)) == INVALID_HANDLE_VALUE)
+        HGOTO_ERROR(H5E_PLUGIN, H5E_OPENERROR, H5_ITER_ERROR, "can't open directory")
+
+    /* Loop over all the files */
+    do {
+        /* Ignore '.' and '..' */
+        if (HDstrcmp(fdFile.cFileName, ".") != 0 && HDstrcmp(fdFile.cFileName, "..") != 0) {
+            hbool_t plugin_matches;
+            size_t  len;
+
+            /* Allocate & initialize the path name */
+            len = HDstrlen(plugin_path) + HDstrlen(H5PL_PATH_SEPARATOR) + HDstrlen(fdFile.cFileName) + 1;
+
+            if (NULL == (path = (char *)H5MM_calloc(len)))
+                HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, H5_ITER_ERROR, "can't allocate memory for path")
+
+            HDsnprintf(path, len, "%s\\%s", plugin_path, fdFile.cFileName);
+
+            /* Ignore directories */
+            if (fdFile.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
+                continue;
+
+            /* Attempt to open the dynamic library */
+            plugin_type   = H5PL_TYPE_ERROR;
+            plugin_info   = NULL;
+            plugin_loaded = FALSE;
+            if (H5PL__open(path, H5PL_TYPE_NONE, NULL, &plugin_loaded, &plugin_type, &plugin_info) < 0)
+                HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, H5_ITER_ERROR, "failed to open plugin '%s'", path);
+
+            /* Determine if we should process this plugin */
+            plugin_matches = (iter_type == H5PL_ITER_TYPE_ALL) ||
+                             ((iter_type == H5PL_ITER_TYPE_FILTER) && (plugin_type == H5PL_TYPE_FILTER)) ||
+                             ((iter_type == H5PL_ITER_TYPE_VOL) && (plugin_type == H5PL_TYPE_VOL));
+
+            /* If the plugin was successfully loaded, call supplied callback function on plugin */
+            if (plugin_loaded && plugin_matches && (ret_value = iter_op(plugin_type, plugin_info, op_data)))
+                break;
+
+            path = (char *)H5MM_xfree(path);
+        }
+    } while (FindNextFileA(hFind, &fdFile));
+
+    if (ret_value < 0)
+        HERROR(H5E_PLUGIN, H5E_CALLBACK, "callback operator function returned failure");
+
+done:
+    if (hFind != INVALID_HANDLE_VALUE)
+        FindClose(hFind);
+
+    path = (char *)H5MM_xfree(path);
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__path_table_iterate_process_path() */
+#endif /* H5_HAVE_WIN32_API */
 
 /*-------------------------------------------------------------------------
  * Function:    H5PL__find_plugin_in_path_table
@@ -674,8 +889,8 @@ H5PL__find_plugin_in_path(const H5PL_search_params_t *search_params, hbool_t *fo
                 continue;
             }
 
-            /* attempt to open the dynamic library as a filter library */
-            if (H5PL__open(path, search_params->type, search_params->key, found, plugin_info) < 0)
+            /* attempt to open the dynamic library */
+            if (H5PL__open(path, search_params->type, search_params->key, found, NULL, plugin_info) < 0)
                 HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, FAIL, "search in directory failed")
             if (*found)
                 HGOTO_DONE(SUCCEED)
@@ -693,7 +908,7 @@ done:
 
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5PL__find_plugin_in_path() */
-#else /* H5_HAVE_WIN32_API */
+#else  /* H5_HAVE_WIN32_API */
 static herr_t
 H5PL__find_plugin_in_path(const H5PL_search_params_t *search_params, hbool_t *found, const char *dir,
                           const void **plugin_info)
@@ -741,8 +956,8 @@ H5PL__find_plugin_in_path(const H5PL_search_params_t *search_params, hbool_t *fo
             if (fdFile.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
                 continue;
 
-            /* attempt to open the dynamic library as a filter library */
-            if (H5PL__open(path, search_params->type, search_params->key, found, plugin_info) < 0)
+            /* attempt to open the dynamic library */
+            if (H5PL__open(path, search_params->type, search_params->key, found, NULL, plugin_info) < 0)
                 HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, FAIL, "search in directory failed")
             if (*found)
                 HGOTO_DONE(SUCCEED)
diff --git a/src/H5PLpkg.h b/src/H5PLpkg.h
index 1018549..5d401a6 100644
--- a/src/H5PLpkg.h
+++ b/src/H5PLpkg.h
@@ -133,7 +133,8 @@ H5_DLL herr_t H5PL__set_plugin_control_mask(unsigned int mask);
 
 /* Plugin search and manipulation */
 H5_DLL herr_t H5PL__open(const char *libname, H5PL_type_t type, const H5PL_key_t *key,
-                         hbool_t *success /*out*/, const void **plugin_info /*out*/);
+                         hbool_t *success /*out*/, H5PL_type_t *plugin_type /*out*/,
+                         const void **plugin_info /*out*/);
 H5_DLL herr_t H5PL__close(H5PL_HANDLE handle);
 
 /* Plugin cache calls */
@@ -153,7 +154,8 @@ H5_DLL herr_t      H5PL__replace_path(const char *path, unsigned int index);
 H5_DLL herr_t      H5PL__insert_path(const char *path, unsigned int index);
 H5_DLL herr_t      H5PL__remove_path(unsigned int index);
 H5_DLL const char *H5PL__get_path(unsigned int index);
-H5_DLL herr_t      H5PL__find_plugin_in_path_table(const H5PL_search_params_t *search_params,
-                                                   hbool_t *found /*out*/, const void **plugin_info /*out*/);
+H5_DLL herr_t H5PL__path_table_iterate(H5PL_iterate_type_t iter_type, H5PL_iterate_t iter_op, void *op_data);
+H5_DLL herr_t H5PL__find_plugin_in_path_table(const H5PL_search_params_t *search_params,
+                                              hbool_t *found /*out*/, const void **plugin_info /*out*/);
 
 #endif /* _H5PLpkg_H */
diff --git a/src/H5PLplugin_cache.c b/src/H5PLplugin_cache.c
index 9c25933..c5e5ca4 100644
--- a/src/H5PLplugin_cache.c
+++ b/src/H5PLplugin_cache.c
@@ -264,12 +264,12 @@ H5PL__find_plugin_in_cache(const H5PL_search_params_t *search_params, hbool_t *f
     /* Loop over all the plugins, looking for one that matches */
     for (u = 0; u < H5PL_num_plugins_g; u++) {
 
-        /* If the plugin type (filter, etc.) and ID match, query the plugin for its info */
+        /* If the plugin type (filter, VOL connector, etc.) and ID match, query the plugin for its info */
         if ((search_params->type == (H5PL_cache_g[u]).type) &&
             (search_params->key->id == (H5PL_cache_g[u]).key.id)) {
 
             H5PL_get_plugin_info_t get_plugin_info_function;
-            const H5Z_class2_t *   filter_info;
+            const void *           info;
 
             /* Get the "get plugin info" function from the plugin. */
             if (NULL == (get_plugin_info_function = (H5PL_get_plugin_info_t)H5PL_GET_LIB_FUNC(
@@ -277,12 +277,12 @@ H5PL__find_plugin_in_cache(const H5PL_search_params_t *search_params, hbool_t *f
                 HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, FAIL, "can't get function for H5PLget_plugin_info")
 
             /* Call the "get plugin info" function */
-            if (NULL == (filter_info = (const H5Z_class2_t *)(*get_plugin_info_function)()))
+            if (NULL == (info = (*get_plugin_info_function)()))
                 HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, FAIL, "can't get plugin info")
 
             /* Set output parameters */
             *found       = TRUE;
-            *plugin_info = filter_info;
+            *plugin_info = info;
 
             /* No need to continue processing */
             break;
diff --git a/src/H5PLprivate.h b/src/H5PLprivate.h
index fff36a7..938959e 100644
--- a/src/H5PLprivate.h
+++ b/src/H5PLprivate.h
@@ -44,6 +44,18 @@ typedef union H5PL_key_t {
     } vol;
 } H5PL_key_t;
 
+/* Enum dictating the type of plugins to process
+ * when iterating through available plugins
+ */
+typedef enum {
+    H5PL_ITER_TYPE_FILTER,
+    H5PL_ITER_TYPE_VOL,
+    H5PL_ITER_TYPE_ALL,
+} H5PL_iterate_type_t;
+
+/* Callback function for iterating through the available plugins */
+typedef herr_t (*H5PL_iterate_t)(H5PL_type_t plugin_type, const void *plugin_info, void *op_data);
+
 /*****************************/
 /* Library-private Variables */
 /*****************************/
@@ -54,5 +66,6 @@ typedef union H5PL_key_t {
 
 /* Internal API routines */
 H5_DLL const void *H5PL_load(H5PL_type_t plugin_type, const H5PL_key_t *key);
+H5_DLL herr_t      H5PL_iterate(H5PL_iterate_type_t iter_type, H5PL_iterate_t iter_op, void *op_data);
 
 #endif /* _H5PLprivate_H */
diff --git a/src/H5VL.c b/src/H5VL.c
index 55779d7..c1f8adb 100644
--- a/src/H5VL.c
+++ b/src/H5VL.c
@@ -87,27 +87,6 @@ H5VLregister_connector(const H5VL_class_t *cls, hid_t vipl_id)
     FUNC_ENTER_API(H5I_INVALID_HID)
     H5TRACE2("i", "*#i", cls, vipl_id);
 
-    /* Check arguments */
-    if (!cls)
-        HGOTO_ERROR(H5E_ARGS, H5E_UNINITIALIZED, H5I_INVALID_HID,
-                    "VOL connector class pointer cannot be NULL")
-    if (H5VL_VERSION != cls->version)
-        HGOTO_ERROR(H5E_VOL, H5E_CANTREGISTER, H5I_INVALID_HID, "VOL connector has incompatible version")
-    if (!cls->name)
-        HGOTO_ERROR(H5E_VOL, H5E_CANTREGISTER, H5I_INVALID_HID,
-                    "VOL connector class name cannot be the NULL pointer")
-    if (0 == HDstrlen(cls->name))
-        HGOTO_ERROR(H5E_VOL, H5E_CANTREGISTER, H5I_INVALID_HID,
-                    "VOL connector class name cannot be the empty string")
-    if (cls->info_cls.copy && !cls->info_cls.free)
-        HGOTO_ERROR(
-            H5E_VOL, H5E_CANTREGISTER, H5I_INVALID_HID,
-            "VOL connector must provide free callback for VOL info objects when a copy callback is provided")
-    if (cls->wrap_cls.get_wrap_ctx && !cls->wrap_cls.free_wrap_ctx)
-        HGOTO_ERROR(H5E_VOL, H5E_CANTREGISTER, H5I_INVALID_HID,
-                    "VOL connector must provide free callback for object wrapping contexts when a get "
-                    "callback is provided")
-
     /* Check VOL initialization property list */
     if (H5P_DEFAULT == vipl_id)
         vipl_id = H5P_VOL_INITIALIZE_DEFAULT;
diff --git a/src/H5VLcallback.c b/src/H5VLcallback.c
index 4ab398f..8b58cea 100644
--- a/src/H5VLcallback.c
+++ b/src/H5VLcallback.c
@@ -29,10 +29,11 @@
 
 #include "H5private.h"   /* Generic Functions                                */
 #include "H5Eprivate.h"  /* Error handling                                   */
-#include "H5Fprivate.h"  /* File access				             */
+#include "H5Fprivate.h"  /* File access	                                     */
 #include "H5Iprivate.h"  /* IDs                                              */
 #include "H5MMprivate.h" /* Memory management                                */
 #include "H5Pprivate.h"  /* Property lists                                   */
+#include "H5PLprivate.h" /* Plugins                                          */
 #include "H5VLpkg.h"     /* Virtual Object Layer                             */
 
 /****************/
@@ -43,6 +44,16 @@
 /* Local Typedefs */
 /******************/
 
+/* Structure used when trying to find a
+ * VOL connector to open a given file with.
+ */
+typedef struct H5VL_file_open_find_connector_t {
+    const char *           filename;
+    const H5VL_class_t *   cls;
+    H5VL_connector_prop_t *connector_prop;
+    hid_t                  fapl_id;
+} H5VL_file_open_find_connector_t;
+
 /********************/
 /* Package Typedefs */
 /********************/
@@ -101,6 +112,8 @@ static void * H5VL__file_create(const H5VL_class_t *cls, const char *name, unsig
                                 hid_t fapl_id, hid_t dxpl_id, void **req);
 static void * H5VL__file_open(const H5VL_class_t *cls, const char *name, unsigned flags, hid_t fapl_id,
                               hid_t dxpl_id, void **req);
+static herr_t H5VL__file_open_find_connector_cb(H5PL_type_t plugin_type, const void *plugin_info,
+                                                void *op_data);
 static herr_t H5VL__file_get(void *obj, const H5VL_class_t *cls, H5VL_file_get_t get_type, hid_t dxpl_id,
                              void **req, va_list arguments);
 static herr_t H5VL__file_specific(void *obj, const H5VL_class_t *cls, H5VL_file_specific_t specific_type,
@@ -3347,6 +3360,98 @@ done:
 } /* end H5VL__file_open() */
 
 /*-------------------------------------------------------------------------
+ * Function:    H5VL__file_open_find_connector_cb
+ *
+ * Purpose:     Iteration callback for H5PL_iterate that tries to find the
+ *              correct VOL connector to open a file with when
+ *              H5VL_file_open fails for its given VOL connector. Iterates
+ *              through all of the available VOL connector plugins until
+ *              H5Fis_accessible returns true for the given filename and
+ *              VOL connector.
+ *
+ * Return:      H5_ITER_CONT if current plugin can't open the given file
+ *              H5_ITER_STOP if current plugin can open given file
+ *              H5_ITER_ERROR if an error occurs while trying to determine
+ *                  if current plugin can open given file.
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5VL__file_open_find_connector_cb(H5PL_type_t plugin_type, const void *plugin_info, void *op_data)
+{
+    H5VL_file_open_find_connector_t *udata = (H5VL_file_open_find_connector_t *)op_data;
+    const H5VL_class_t *             cls   = (const H5VL_class_t *)plugin_info;
+    H5P_genplist_t *                 fapl_plist;
+    H5P_genplist_t *                 fapl_plist_copy;
+    herr_t                           status;
+    htri_t                           is_accessible = FALSE;
+    hid_t                            connector_id  = H5I_INVALID_HID;
+    hid_t                            fapl_id       = H5I_INVALID_HID;
+    herr_t                           ret_value     = H5_ITER_CONT;
+
+    FUNC_ENTER_STATIC
+
+    HDassert(udata);
+    HDassert(udata->filename);
+    HDassert(udata->connector_prop);
+    HDassert(cls);
+    HDassert(plugin_type == H5PL_TYPE_VOL);
+
+    /* Silence compiler */
+    (void)plugin_type;
+
+    udata->cls = cls;
+
+    /* Attempt to register plugin as a VOL connector */
+    if ((connector_id = H5VL__register_connector_by_class(cls, TRUE, H5P_VOL_INITIALIZE_DEFAULT)) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTREGISTER, H5_ITER_ERROR, "unable to register VOL connector")
+
+    /* Setup FAPL with registered VOL connector */
+    if (NULL == (fapl_plist = (H5P_genplist_t *)H5I_object_verify(udata->fapl_id, H5I_GENPROP_LST)))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, H5_ITER_ERROR, "not a property list")
+    if ((fapl_id = H5P_copy_plist(fapl_plist, TRUE)) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTCOPY, H5_ITER_ERROR, "can't copy fapl");
+    if (NULL == (fapl_plist_copy = (H5P_genplist_t *)H5I_object_verify(fapl_id, H5I_GENPROP_LST)))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, H5_ITER_ERROR, "not a property list")
+    if (H5P_set_vol(fapl_plist_copy, connector_id, NULL) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, H5_ITER_ERROR, "can't set VOL connector on fapl")
+
+    /* Check if file is accessible with given VOL connector */
+    H5E_BEGIN_TRY
+    {
+        status = H5VL_file_specific(NULL, H5VL_FILE_IS_ACCESSIBLE, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL,
+                                    fapl_id, udata->filename, &is_accessible);
+    }
+    H5E_END_TRY;
+
+    /* If the file was accessible with the current VOL connector, return
+     * the FAPL with that VOL connector set on it. Errors are ignored here
+     * as some VOL connectors may not support H5Fis_accessible.
+     */
+    if (status == SUCCEED && is_accessible > 0) {
+        /* Modify 'connector_prop' to point to the VOL connector that
+         * was actually used to open the file, rather than the original
+         * VOL connector that was requested.
+         */
+        udata->connector_prop->connector_id   = connector_id;
+        udata->connector_prop->connector_info = NULL;
+
+        udata->fapl_id = fapl_id;
+        ret_value      = H5_ITER_STOP;
+    } /* end if */
+
+done:
+    if (ret_value != H5_ITER_STOP) {
+        if (fapl_id >= 0 && H5I_dec_app_ref(fapl_id) < 0)
+            HDONE_ERROR(H5E_PLIST, H5E_CANTCLOSEOBJ, H5_ITER_ERROR, "can't close fapl")
+        if (connector_id >= 0 && H5I_dec_app_ref(connector_id) < 0)
+            HDONE_ERROR(H5E_ID, H5E_CANTCLOSEOBJ, H5_ITER_ERROR, "can't close VOL connector ID")
+    } /* end if */
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__file_open_find_connector_cb() */
+
+/*-------------------------------------------------------------------------
  * Function:	H5VL_file_open
  *
  * Purpose:	Opens a file through the VOL.
@@ -3360,7 +3465,7 @@ done:
  *-------------------------------------------------------------------------
  */
 void *
-H5VL_file_open(const H5VL_connector_prop_t *connector_prop, const char *name, unsigned flags, hid_t fapl_id,
+H5VL_file_open(H5VL_connector_prop_t *connector_prop, const char *name, unsigned flags, hid_t fapl_id,
                hid_t dxpl_id, void **req)
 {
     H5VL_class_t *cls;              /* VOL Class structure for callback info    */
@@ -3373,8 +3478,54 @@ H5VL_file_open(const H5VL_connector_prop_t *connector_prop, const char *name, un
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, NULL, "not a VOL connector ID")
 
     /* Call the corresponding internal VOL routine */
-    if (NULL == (ret_value = H5VL__file_open(cls, name, flags, fapl_id, dxpl_id, req)))
-        HGOTO_ERROR(H5E_VOL, H5E_CANTOPENOBJ, NULL, "open failed")
+    if (NULL == (ret_value = H5VL__file_open(cls, name, flags, fapl_id, dxpl_id, req))) {
+        H5VL_file_open_find_connector_t find_connector_ud;
+        hbool_t                         find_connector;
+        hbool_t                         connector_available = FALSE;
+
+        /* Opening the file failed - Determine whether we should search
+         * the plugin path to see if any other VOL connectors are available
+         * to attempt to open the file with. This only occurs if no particular
+         * VOL connector was specified (either via a FAPL or the
+         * HDF5_VOL_CONNECTOR environment variable).
+         */
+        find_connector = !getenv("HDF5_VOL_CONNECTOR") && ((H5P_FILE_ACCESS_DEFAULT == fapl_id) ||
+                                                           connector_prop->connector_id == H5_DEFAULT_VOL);
+
+        if (find_connector) {
+            herr_t iter_ret;
+
+            find_connector_ud.connector_prop = connector_prop;
+            find_connector_ud.filename       = name;
+            find_connector_ud.cls            = NULL;
+            find_connector_ud.fapl_id        = fapl_id;
+
+            iter_ret = H5PL_iterate(H5PL_ITER_TYPE_VOL, H5VL__file_open_find_connector_cb,
+                                    (void *)&find_connector_ud);
+            if (iter_ret < 0)
+                HGOTO_ERROR(H5E_VOL, H5E_BADITER, NULL,
+                            "failed to iterate over available VOL connector plugins")
+            else if (iter_ret)
+                connector_available = TRUE;
+        } /* end if */
+
+        /* If one of the available VOL connector plugins is
+         * able to open the file, clear the error stack from any
+         * previous file open failures and then open the file.
+         * Otherwise, if no VOL connectors are available, throw
+         * error from original file open failure.
+         */
+        if (connector_available) {
+            H5E_clear_stack(NULL);
+
+            if (NULL == (ret_value = H5VL__file_open(find_connector_ud.cls, name, flags,
+                                                     find_connector_ud.fapl_id, dxpl_id, req)))
+                HGOTO_ERROR(H5E_VOL, H5E_CANTOPENOBJ, NULL, "can't open file '%s' with VOL connector '%s'",
+                            name, find_connector_ud.cls->name)
+        }
+        else
+            HGOTO_ERROR(H5E_VOL, H5E_CANTOPENOBJ, NULL, "open failed")
+    } /* end if */
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
diff --git a/src/H5VLint.c b/src/H5VLint.c
index bc06361..17578b8 100644
--- a/src/H5VLint.c
+++ b/src/H5VLint.c
@@ -1197,6 +1197,27 @@ H5VL__register_connector_by_class(const H5VL_class_t *cls, hbool_t app_ref, hid_
 
     FUNC_ENTER_PACKAGE
 
+    /* Check arguments */
+    if (!cls)
+        HGOTO_ERROR(H5E_ARGS, H5E_UNINITIALIZED, H5I_INVALID_HID,
+                    "VOL connector class pointer cannot be NULL")
+    if (H5VL_VERSION != cls->version)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTREGISTER, H5I_INVALID_HID, "VOL connector has incompatible version")
+    if (!cls->name)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTREGISTER, H5I_INVALID_HID,
+                    "VOL connector class name cannot be the NULL pointer")
+    if (0 == HDstrlen(cls->name))
+        HGOTO_ERROR(H5E_VOL, H5E_CANTREGISTER, H5I_INVALID_HID,
+                    "VOL connector class name cannot be the empty string")
+    if (cls->info_cls.copy && !cls->info_cls.free)
+        HGOTO_ERROR(
+            H5E_VOL, H5E_CANTREGISTER, H5I_INVALID_HID,
+            "VOL connector must provide free callback for VOL info objects when a copy callback is provided")
+    if (cls->wrap_cls.get_wrap_ctx && !cls->wrap_cls.free_wrap_ctx)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTREGISTER, H5I_INVALID_HID,
+                    "VOL connector must provide free callback for object wrapping contexts when a get "
+                    "callback is provided")
+
     /* Set up op data for iteration */
     op_data.kind     = H5VL_GET_CONNECTOR_BY_NAME;
     op_data.u.name   = cls->name;
diff --git a/src/H5VLprivate.h b/src/H5VLprivate.h
index eefd648..a224a14 100644
--- a/src/H5VLprivate.h
+++ b/src/H5VLprivate.h
@@ -197,7 +197,7 @@ H5_DLL herr_t H5VL_datatype_close(const H5VL_object_t *vol_obj, hid_t dxpl_id, v
 /* File functions */
 H5_DLL void * H5VL_file_create(const H5VL_connector_prop_t *connector_prop, const char *name, unsigned flags,
                                hid_t fcpl_id, hid_t fapl_id, hid_t dxpl_id, void **req);
-H5_DLL void * H5VL_file_open(const H5VL_connector_prop_t *connector_prop, const char *name, unsigned flags,
+H5_DLL void * H5VL_file_open(H5VL_connector_prop_t *connector_prop, const char *name, unsigned flags,
                              hid_t fapl_id, hid_t dxpl_id, void **req);
 H5_DLL herr_t H5VL_file_get(const H5VL_object_t *vol_obj, H5VL_file_get_t get_type, hid_t dxpl_id, void **req,
                             ...);