lib/util: consolidate module loading into common code

This creates a samba-modules private libary that handles the details.

Andrew Bartlett

3 files changed, 314 insertions, 0 deletions

diff --git a/lib/util/modules.c b/lib/util/modules.c
new file mode 100644
index 0000000000..d25cabf760
--- /dev/null
+++ b/lib/util/modules.c
@@ -0,0 +1,243 @@
+/*
+   Unix SMB/CIFS implementation.
+   Samba utility functions
+   Copyright (C) Jelmer Vernooij 2002-2003,2005-2007
+   Copyright (C) Stefan (metze) Metzmacher 2003
+   Copyright (C) Andrew Bartlett 2011
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "includes.h"
+#include "dynconfig/dynconfig.h"
+#include "lib/util/samba_modules.h"
+#include "system/filesys.h"
+#include "system/dir.h"
+
+/**
+ * Obtain the init function from a shared library file
+ */
+init_module_fn load_module(TALLOC_CTX *mem_ctx, const char *path)
+{
+	void *handle;
+	void *init_fn;
+
+	handle = dlopen(path, RTLD_NOW);
+	if (handle == NULL) {
+		DEBUG(0, ("Unable to open %s: %s\n", path, dlerror()));
+		return NULL;
+	}
+
+	init_fn = dlsym(handle, SAMBA_INIT_MODULE);
+
+	if (init_fn == NULL) {
+		DEBUG(0, ("Unable to find %s() in %s: %s\n",
+			  SAMBA_INIT_MODULE, path, dlerror()));
+		DEBUG(1, ("Loading module '%s' failed\n", path));
+		dlclose(handle);
+		return NULL;
+	}
+
+	return (init_module_fn)init_fn;
+}
+
+/**
+ * Obtain list of init functions from the modules in the specified
+ * directory
+ */
+init_module_fn *load_modules(TALLOC_CTX *mem_ctx, const char *path)
+{
+	DIR *dir;
+	struct dirent *entry;
+	char *filename;
+	int success = 0;
+	init_module_fn *ret = talloc_array(mem_ctx, init_module_fn, 2);
+
+	ret[0] = NULL;
+
+	dir = opendir(path);
+	if (dir == NULL) {
+		talloc_free(ret);
+		return NULL;
+	}
+
+	while((entry = readdir(dir))) {
+		if (ISDOT(entry->d_name) || ISDOTDOT(entry->d_name))
+			continue;
+
+		filename = talloc_asprintf(mem_ctx, "%s/%s", path, entry->d_name);
+
+		ret[success] = load_module(mem_ctx, filename);
+		if (ret[success]) {
+			ret = talloc_realloc(mem_ctx, ret, init_module_fn, success+2);
+			success++;
+			ret[success] = NULL;
+		}
+
+		talloc_free(filename);
+	}
+
+	closedir(dir);
+
+	return ret;
+}
+
+/**
+ * Run the specified init functions.
+ *
+ * @return true if all functions ran successfully, false otherwise
+ */
+bool run_init_functions(init_module_fn *fns)
+{
+	int i;
+	bool ret = true;
+
+	if (fns == NULL)
+		return true;
+
+	for (i = 0; fns[i]; i++) { ret &= (bool)NT_STATUS_IS_OK(fns[i]()); }
+
+	return ret;
+}
+
+/**
+ * Load the initialization functions from DSO files for a specific subsystem.
+ *
+ * Will return an array of function pointers to initialization functions
+ */
+
+init_module_fn *load_samba_modules(TALLOC_CTX *mem_ctx, const char *subsystem)
+{
+	char *path = modules_path(mem_ctx, subsystem);
+	init_module_fn *ret;
+
+	ret = load_modules(mem_ctx, path);
+
+	talloc_free(path);
+
+	return ret;
+}
+
+
+/* Load a dynamic module.  Only log a level 0 error if we are not checking
+   for the existence of a module (probling). */
+
+static NTSTATUS do_smb_load_module(const char *module_name, bool is_probe)
+{
+	void *handle;
+	init_module_function *init;
+	NTSTATUS status;
+	const char *error;
+
+	/* Always try to use LAZY symbol resolving; if the plugin has
+	 * backwards compatibility, there might be symbols in the
+	 * plugin referencing to old (removed) functions
+	 */
+	handle = dlopen(module_name, RTLD_LAZY);
+
+	/* This call should reset any possible non-fatal errors that
+	   occured since last call to dl* functions */
+	error = dlerror();
+
+	if(!handle) {
+		int level = is_probe ? 3 : 0;
+		DEBUG(level, ("Error loading module '%s': %s\n", module_name, error ? error : ""));
+		return NT_STATUS_UNSUCCESSFUL;
+	}
+
+	init = (init_module_function *)dlsym(handle, "init_samba_module");
+
+	/* we must check dlerror() to determine if it worked, because
+           dlsym() can validly return NULL */
+	error = dlerror();
+	if (error) {
+		DEBUG(0, ("Error trying to resolve symbol 'init_samba_module' "
+			  "in %s: %s\n", module_name, error));
+		dlclose(handle);
+		return NT_STATUS_UNSUCCESSFUL;
+	}
+
+	DEBUG(2, ("Module '%s' loaded\n", module_name));
+
+	status = init();
+	if (!NT_STATUS_IS_OK(status)) {
+		DEBUG(0, ("Module '%s' initialization failed: %s\n",
+			    module_name, get_friendly_nt_error_msg(status)));
+		dlclose(handle);
+	}
+
+	return status;
+}
+
+NTSTATUS smb_load_module(const char *module_name)
+{
+	return do_smb_load_module(module_name, false);
+}
+
+/* Load all modules in list and return number of
+ * modules that has been successfully loaded */
+int smb_load_modules(const char **modules)
+{
+	int i;
+	int success = 0;
+
+	for(i = 0; modules[i]; i++){
+		if(NT_STATUS_IS_OK(smb_load_module(modules[i]))) {
+			success++;
+		}
+	}
+
+	DEBUG(2, ("%d modules successfully loaded\n", success));
+
+	return success;
+}
+
+NTSTATUS smb_probe_module(const char *subsystem, const char *module)
+{
+	char *full_path = NULL;
+	TALLOC_CTX *ctx = talloc_stackframe();
+	NTSTATUS status;
+
+	/* Check for absolute path */
+
+	/* if we make any 'samba multibyte string'
+	   calls here, we break
+	   for loading string modules */
+
+	DEBUG(5, ("Probing module '%s'\n", module));
+
+	if (module[0] == '/') {
+		status = do_smb_load_module(module, true);
+		TALLOC_FREE(ctx);
+		return status;
+	}
+
+	full_path = talloc_asprintf(ctx,
+				    "%s/%s.%s",
+				    modules_path(ctx, subsystem),
+				    module,
+				    shlib_ext());
+	if (!full_path) {
+		TALLOC_FREE(ctx);
+		return NT_STATUS_NO_MEMORY;
+	}
+
+	DEBUG(5, ("Probing module '%s': Trying to load from %s\n",
+		module, full_path));
+
+	status = do_smb_load_module(full_path, true);
+
+	TALLOC_FREE(ctx);
+	return status;
+}
diff --git a/lib/util/samba_modules.h b/lib/util/samba_modules.h
new file mode 100644
index 0000000000..2cca622e50
--- /dev/null
+++ b/lib/util/samba_modules.h
@@ -0,0 +1,65 @@
+/*
+   Unix SMB/CIFS implementation.
+   Handling of idle/exit events
+   Copyright (C) Stefan (metze) Metzmacher	2003
+   Copyright (C) Andrew Bartlett 2011
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef _SAMBA_MODULES_H
+#define _SAMBA_MODULES_H
+
+/* Module support */
+typedef NTSTATUS (init_module_function) (void);
+typedef NTSTATUS (*init_module_fn) (void);
+
+NTSTATUS init_samba_module(void);
+
+/* this needs to be a string which is not in the C library. We
+   previously used "init_module", but that meant that modules which
+   did not define this function ended up calling the C library
+   function init_module() which makes a system call */
+#define SAMBA_INIT_MODULE "samba_init_module"
+
+/**
+ * Obtain the init function from a shared library file
+ */
+init_module_fn load_module(TALLOC_CTX *mem_ctx, const char *path);
+
+/**
+ * Obtain list of init functions from the modules in the specified
+ * directory
+ */
+init_module_fn *load_modules(TALLOC_CTX *mem_ctx, const char *path);
+
+/**
+ * Run the specified init functions.
+ *
+ * @return true if all functions ran successfully, false otherwise
+ */
+bool run_init_functions(init_module_fn *fns);
+
+/**
+ * Load the initialization functions from DSO files for a specific subsystem.
+ *
+ * Will return an array of function pointers to initialization functions
+ */
+init_module_fn *load_samba_modules(TALLOC_CTX *mem_ctx, const char *subsystem);
+
+NTSTATUS smb_load_module(const char *module_name);
+int smb_load_modules(const char **modules);
+NTSTATUS smb_probe_module(const char *subsystem, const char *module);
+
+#endif /* _SAMBA_MODULES_H */
diff --git a/lib/util/wscript_build b/lib/util/wscript_build
index 70a639d2d7..f4bd885231 100755
--- a/lib/util/wscript_build
+++ b/lib/util/wscript_build
@@ -17,6 +17,12 @@ bld.SAMBA_LIBRARY('samba-util',
                   pc_files='samba-util.pc'
                   )
 
+bld.SAMBA_LIBRARY('samba-modules',
+		  source='modules.c',
+		  deps='errors samba-util',
+		  local_include=False,
+		  private_library=True)
+
 bld.SAMBA_LIBRARY('asn1util',
                   source='asn1.c',
                   deps='talloc samba-util',