module: Introduce a basic module dependency framework

Makefile.am

@@ -214,6 +214,7 @@ src_iwd_SOURCES = src/main.c linux/nl80211.h src/iwd.h src/missing.h \
 					src/resolve.h src/resolve.c\
 					src/hotspot.h src/hotspot.c \
 					src/p2putil.h src/p2putil.c \
+					src/module.c \
 					$(eap_sources) \
 					$(builtin_sources)
 

src/hotspot.c

@@ -360,3 +360,4 @@ static void hotspot_exit(void)
 }
 
 IWD_MODULE(hotspot, hotspot_init, hotspot_exit)
+IWD_MODULE_DEPENDS(hotspot, known_networks)

src/iwd.h

@@ -44,8 +44,25 @@ struct iwd_module_desc {
 	bool active;
 } __attribute__((aligned(8)));
 
+struct iwd_module_depends {
+	const char *self;
+	const char *target;
+};
+
 #define IWD_MODULE(name, init, exit)					\
 	static struct iwd_module_desc __iwd_module_ ## name		\
 		__attribute__((used, section("__iwd_module"), aligned(8))) = {\
 			#name, init, exit				\
 		};
+
+#define IWD_MODULE_DEPENDS(name, dep)					\
+	static struct iwd_module_depends				\
+				__iwd_module__##name_##dep		\
+		__attribute__((used, section("__iwd_module_dep"),       \
+					aligned(8))) = {		\
+			.self = #name,					\
+			.target = #dep,					\
+		};
+
+int iwd_modules_init();
+void iwd_modules_exit();

src/main.c

@@ -159,44 +159,6 @@ static void nl80211_appeared(const struct l_genl_family_info *info,
 	netdev_set_nl80211(nl80211);
 }
 
-extern struct iwd_module_desc __start___iwd_module[];
-extern struct iwd_module_desc __stop___iwd_module[];
-
-static int iwd_modules_init()
-{
-	struct iwd_module_desc *desc;
-	int r;
-
-	l_debug("");
-
-	for (desc = __start___iwd_module; desc < __stop___iwd_module; desc++) {
-		r = desc->init();
-		if (r < 0)
-			return r;
-
-		l_debug("Initialized module: %s", desc->name);
-		desc->active = true;
-	}
-
-	return 0;
-}
-
-static void iwd_modules_exit()
-{
-	struct iwd_module_desc *desc;
-
-	l_debug("");
-
-	for (desc = __stop___iwd_module - 1;
-			desc >= __start___iwd_module; desc--) {
-		if (!desc->active)
-			continue;
-		l_debug("Removing module: %s", desc->name);
-		desc->exit();
-		desc->active = false;
-	}
-}
-
 static void request_name_callback(struct l_dbus *dbus, bool success,
 					bool queued, void *user_data)
 {

src/module.c

@@ -0,0 +1,184 @@
+/*
+ *
+ *  Wireless daemon for Linux
+ *
+ *  Copyright (C) 2019  Intel Corporation. All rights reserved.
+ *
+ *  This library is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU Lesser General Public
+ *  License as published by the Free Software Foundation; either
+ *  version 2.1 of the License, or (at your option) any later version.
+ *
+ *  This library 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
+ *  Lesser General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Lesser General Public
+ *  License along with this library; if not, write to the Free Software
+ *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ */
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <errno.h>
+#include <ell/ell.h>
+
+#include "src/iwd.h"
+
+struct dependency {
+	struct dependency *next;
+	struct module *module;
+};
+
+struct module {
+	struct iwd_module_desc *desc;
+	struct dependency *depends;
+	bool visited : 1;
+	bool processed : 1;
+};
+
+extern struct iwd_module_desc __start___iwd_module[];
+extern struct iwd_module_desc __stop___iwd_module[];
+extern struct iwd_module_depends __start___iwd_module_dep[];
+extern struct iwd_module_depends __stop___iwd_module_dep[];
+
+struct iwd_module_desc **modules_sorted;
+
+static struct module *module_find(struct module *modules, size_t count,
+						const char *name)
+{
+	unsigned int i;
+
+	for (i = 0; i < count; i++)
+		if (!strcmp(modules[i].desc->name, name))
+			return &modules[i];
+
+	return NULL;
+}
+
+static int module_topological_order(struct module *module,
+					struct iwd_module_desc **sorted,
+					size_t *offset)
+{
+	struct dependency *d;
+	int r;
+
+	module->visited = true;
+
+	for (d = module->depends; d; d = d->next) {
+		if (d->module->processed)
+			continue;
+
+		if (d->module->visited) {
+			l_error("Circular dependency between %s and %s",
+					module->desc->name,
+					d->module->desc->name);
+			return -EINVAL;
+		}
+
+		r = module_topological_order(d->module, sorted, offset);
+		if (r < 0)
+			return r;
+	}
+
+	module->processed = true;
+	sorted[*offset] = module->desc;
+	*offset += 1;
+	return 0;
+}
+
+int iwd_modules_init()
+{
+	struct iwd_module_desc *desc;
+	struct iwd_module_depends *dep;
+	L_AUTO_FREE_VAR(struct module *, modules) = NULL;
+	L_AUTO_FREE_VAR(struct dependency *, deps) = NULL;
+	L_AUTO_FREE_VAR(struct iwd_module_desc **, sorted) = NULL;
+	unsigned int i = 0;
+	size_t n_modules;
+	size_t n_deps;
+	size_t offset;
+	int r;
+
+	l_debug("");
+
+	n_modules = (__stop___iwd_module - __start___iwd_module);
+	modules = l_new(struct module, n_modules);
+
+	for (desc = __start___iwd_module; desc < __stop___iwd_module; desc++)
+		modules[i++].desc = desc;
+
+	n_deps = (__stop___iwd_module_dep - __start___iwd_module_dep);
+	deps = l_new(struct dependency, n_deps);
+
+	for (dep = __start___iwd_module_dep, i = 0;
+				dep < __stop___iwd_module_dep; dep++, i++) {
+		struct module *src;
+		struct module *dst;
+
+		src = module_find(modules, n_modules, dep->self);
+		dst = module_find(modules, n_modules, dep->target);
+		if (!src || !dst) {
+			l_error("Module dependency %s->%s not found",
+					dep->self, dep->target);
+			return -EINVAL;
+		}
+
+		deps[i].next = src->depends;
+		deps[i].module = dst;
+		src->depends = &deps[i];
+	}
+
+	sorted = l_new(struct iwd_module_desc *, n_modules);
+
+	for (i = 0, offset = 0; i < n_modules; i++) {
+		if (modules[i].processed)
+			continue;
+
+		if (module_topological_order(&modules[i], sorted,
+							&offset) < 0)
+			return -EINVAL;
+	}
+
+	modules_sorted = sorted;
+	sorted = NULL;
+
+	for (i = 0; i < n_modules; i++) {
+		desc = modules_sorted[i];
+		r = desc->init();
+
+		if (r < 0)
+			return r;
+
+		desc->active = true;
+	}
+
+	return 0;
+}
+
+void iwd_modules_exit()
+{
+	struct iwd_module_desc *desc;
+	unsigned int i;
+	size_t n_modules = (__stop___iwd_module - __start___iwd_module);
+
+	l_debug("");
+
+	if (!modules_sorted)
+		return;
+
+	for (i = 0; i < n_modules; i++) {
+		desc = modules_sorted[i];
+		if (!desc->active)
+			continue;
+
+		desc->exit();
+		desc->active = false;
+	}
+
+	l_free(modules_sorted);
+	modules_sorted = NULL;
+}