modules: use topological sort with dependencies

main/gr_module.h

@@ -32,9 +32,8 @@ void gr_register_api_handler(struct gr_api_handler *);
 
 struct gr_module {
 	const char *name;
-	int init_prio;
+	const char *depends_on;
 	void (*init)(struct event_base *);
-	int fini_prio;
 	void (*fini)(struct event_base *);
 	void (*init_dp)(void);
 	void (*fini_dp)(void);

main/module.c

@@ -52,15 +52,90 @@ const struct gr_api_handler *lookup_api_handler(const struct gr_api_request *req
 static STAILQ_HEAD(, gr_module) modules = STAILQ_HEAD_INITIALIZER(modules);
 
 void gr_register_module(struct gr_module *mod) {
+	struct gr_module *m;
+
 	if (mod->name == NULL)
 		ABORT("module with no name: %p", mod);
+
+	STAILQ_FOREACH (m, &modules, entries) {
+		if (strcmp(mod->name, m->name) == 0)
+			ABORT("duplicate module name: '%s'", mod->name);
+	}
+
 	STAILQ_INSERT_TAIL(&modules, mod, entries);
 }
 
-static int module_init_prio_order(const void *a, const void *b) {
-	const struct gr_module *const *mod_a = a;
-	const struct gr_module *const *mod_b = b;
-	return (*mod_a)->init_prio - (*mod_b)->init_prio;
+static void topo_sort(struct gr_module **mods) {
+	// Create an adjacency matrix representing all edges
+	const size_t len = gr_vec_len(mods);
+	bool *adj_matrix = calloc(len * len, sizeof(bool));
+	if (adj_matrix == NULL)
+		ABORT("cannot allocate memory");
+
+	for (unsigned i = 0; i < len; i++) {
+		if (mods[i]->depends_on == NULL)
+			continue;
+
+		for (unsigned j = 0; j < len; j++) {
+			if (strcmp(mods[j]->name, mods[i]->depends_on) == 0) {
+				adj_matrix[j * len + i] = true;
+				break;
+			}
+		}
+	}
+
+	// Calculate in-degree of each vertex
+	int *in_degree = calloc(len, sizeof(int));
+	if (in_degree == NULL)
+		ABORT("cannot allocate memory");
+
+	for (unsigned i = 0; i < len; i++) {
+		for (unsigned j = 0; j < len; j++) {
+			if (adj_matrix[i * len + j]) {
+				in_degree[j]++;
+			}
+		}
+	}
+
+	// Kahn's algorithm for topological sort
+	unsigned front = 0, rear = 0;
+	unsigned *queue = calloc(len, sizeof(unsigned));
+	if (queue == NULL)
+		ABORT("cannot allocate memory");
+
+	for (unsigned i = 0; i < len; i++) {
+		if (in_degree[i] == 0) {
+			queue[rear++] = i;
+		}
+	}
+
+	struct gr_module **sorted = calloc(len, sizeof(struct gr_module *));
+	if (sorted == NULL)
+		ABORT("cannot allocate memory");
+
+	unsigned i = 0;
+	while (front < rear) {
+		unsigned u = queue[front++];
+		sorted[i++] = mods[u];
+
+		// Reduce in-degree of neighbours
+		for (unsigned v = 0; v < len; v++) {
+			if (adj_matrix[u * len + v]) {
+				in_degree[v]--;
+				if (in_degree[v] == 0) {
+					queue[rear++] = v;
+				}
+			}
+		}
+	}
+
+	// Copy the sorted modules back to the original array
+	memcpy(mods, sorted, len * sizeof(struct gr_module *));
+
+	free(sorted);
+	free(queue);
+	free(in_degree);
+	free(adj_matrix);
 }
 
 void modules_init(struct event_base *ev_base) {
@@ -72,24 +147,18 @@ void modules_init(struct event_base *ev_base) {
 	if (mods == NULL)
 		ABORT("failed to alloc module array");
 
-	qsort(mods, gr_vec_len(mods), sizeof(struct gr_module *), module_init_prio_order);
+	topo_sort(mods);
 
 	gr_vec_foreach (mod, mods) {
 		if (mod->init != NULL) {
-			LOG(DEBUG, "%s prio %i", mod->name, mod->init_prio);
+			LOG(DEBUG, "'%s' (depends on '%s')", mod->name, mod->depends_on ?: "");
 			mod->init(ev_base);
 		}
 	}
 
 	gr_vec_free(mods);
 }
 
-static int module_fini_prio_order(const void *a, const void *b) {
-	const struct gr_module *const *mod_a = a;
-	const struct gr_module *const *mod_b = b;
-	return (*mod_a)->fini_prio - (*mod_b)->fini_prio;
-}
-
 void modules_fini(struct event_base *ev_base) {
 	struct gr_module *mod, **mods = NULL;
 
@@ -99,11 +168,13 @@ void modules_fini(struct event_base *ev_base) {
 	if (mods == NULL)
 		ABORT("failed to alloc module array");
 
-	qsort(mods, gr_vec_len(mods), sizeof(struct gr_module *), module_fini_prio_order);
+	topo_sort(mods);
 
-	gr_vec_foreach (mod, mods) {
+	// call fini() functions in reverse topological order
+	for (int i = gr_vec_len(mods) - 1; i >= 0; i--) {
+		mod = mods[i];
 		if (mod->fini != NULL) {
-			LOG(DEBUG, "%s prio %i", mod->name, mod->fini_prio);
+			LOG(DEBUG, "'%s' (depends on '%s')", mod->name, mod->depends_on ?: "");
 			mod->fini(ev_base);
 		}
 	}

modules/infra/control/control_output.c

@@ -107,6 +107,7 @@ static void control_output_fini(struct event_base *) {
 
 static struct gr_module control_output_module = {
 	.name = "control_output",
+	.depends_on = "graph",
 	.init = control_output_init,
 	.fini = control_output_fini,
 };

modules/infra/control/graph.c

@@ -337,10 +337,9 @@ static void graph_fini(struct event_base *) {
 
 static struct gr_module graph_module = {
 	.name = "graph",
+	.depends_on = "iface",
 	.init = graph_init,
-	.init_prio = -999,
 	.fini = graph_fini,
-	.fini_prio = -999,
 };
 
 RTE_INIT(control_graph_init) {

modules/infra/control/iface.c

@@ -298,9 +298,9 @@ static void iface_fini(struct event_base *) {
 
 static struct gr_module iface_module = {
 	.name = "iface",
+	.depends_on = "iface port",
 	.init = iface_init,
 	.fini = iface_fini,
-	.fini_prio = 1000,
 };
 
 static void iface_event_debug(uint32_t event, const void *obj) {

modules/infra/control/loopback.c

@@ -273,7 +273,6 @@ static struct gr_module loopback_module = {
 	.name = "iface loopback",
 	.init = loopback_module_init,
 	.fini = loopback_module_fini,
-	.fini_prio = 1000,
 };
 
 RTE_INIT(loopback_constructor) {

modules/infra/control/nexthop.c

@@ -311,7 +311,6 @@ static struct gr_module module = {
 	.name = "nexthop",
 	.init = nh_init,
 	.fini = nh_fini,
-	.fini_prio = 20000,
 };
 
 RTE_INIT(init) {

modules/infra/control/vlan.c

@@ -257,7 +257,6 @@ static struct gr_module vlan_module = {
 	.name = "vlan",
 	.init = vlan_init,
 	.fini = vlan_fini,
-	.fini_prio = 1000,
 };
 
 static void port_event(uint32_t event, const void *obj) {

modules/infra/control/worker.c

@@ -422,9 +422,9 @@ static void worker_fini(struct event_base *) {
 
 static struct gr_module worker_module = {
 	.name = "worker",
+	.depends_on = "control_output",
 	.init = worker_init,
 	.fini = worker_fini,
-	.fini_prio = -1000,
 };
 
 RTE_INIT(control_infra_init) {

modules/ip/control/address.c

@@ -217,7 +217,6 @@ static struct gr_module addr_module = {
 	.name = "ipv4 address",
 	.init = addr_init,
 	.fini = addr_fini,
-	.fini_prio = 2000,
 };
 
 static struct gr_event_subscription iface_pre_rm_subscription = {

modules/ip/control/nexthop.c

@@ -294,6 +294,7 @@ static struct gr_api_handler nh4_list_handler = {
 
 static struct gr_module nh4_module = {
 	.name = "ipv4 nexthop",
+	.depends_on = "graph",
 	.init = nh4_init,
 };
 

modules/ip/control/route.c

@@ -476,7 +476,6 @@ static struct gr_module route4_module = {
 	.name = "ipv4 route",
 	.init = route4_init,
 	.fini = route4_fini,
-	.fini_prio = 10000,
 };
 
 RTE_INIT(control_ip_init) {

modules/ip/datapath/fib4.c

@@ -155,7 +155,6 @@ static struct gr_module module = {
 	.name = "fib4",
 	.init = fib4_init,
 	.fini = fib4_fini,
-	.fini_prio = 10000,
 };
 
 RTE_INIT(init) {

modules/ip6/control/address.c

@@ -378,7 +378,6 @@ static struct gr_module addr6_module = {
 	.name = "ipv6 address",
 	.init = addr6_init,
 	.fini = addr6_fini,
-	.fini_prio = 2000,
 };
 
 static struct gr_event_subscription iface_event_subscription = {

modules/ip6/control/nexthop.c

@@ -339,6 +339,7 @@ static struct gr_api_handler nh6_list_handler = {
 
 static struct gr_module nh6_module = {
 	.name = "ipv6 nexthop",
+	.depends_on = "graph",
 	.init = nh6_init,
 };
 

modules/ip6/control/route.c

@@ -504,7 +504,6 @@ static struct gr_module route6_module = {
 	.name = "ipv6 route",
 	.init = route6_init,
 	.fini = route6_fini,
-	.fini_prio = 10000,
 };
 
 RTE_INIT(control_ip_init) {

modules/ip6/control/router_advert.c

@@ -210,9 +210,9 @@ static void ra_fini(struct event_base * /*ev_base*/) {
 
 static struct gr_module ra_module = {
 	.name = "ipv6 router advertisement",
+	.depends_on = "graph",
 	.init = ra_init,
 	.fini = ra_fini,
-	.fini_prio = 20000,
 };
 
 static struct gr_api_handler ra_set_handler = {

modules/ip6/datapath/fib6.c

@@ -175,7 +175,6 @@ static struct gr_module module = {
 	.name = "fib6",
 	.init = fib6_init,
 	.fini = fib6_fini,
-	.fini_prio = 10000,
 };
 
 RTE_INIT(init) {

modules/ipip/control.c

@@ -156,7 +156,6 @@ static struct gr_module ipip_module = {
 	.name = "ipip",
 	.init = ipip_init,
 	.fini = ipip_fini,
-	.fini_prio = 1000,
 };
 
 RTE_INIT(ipip_constructor) {

modules/srv6/control_headend.c

@@ -510,7 +510,6 @@ static struct gr_module srv6_headend_module = {
 	.name = "srv6_headend",
 	.init = srv6_init,
 	.fini = srv6_fini,
-	.fini_prio = 1000,
 };
 
 RTE_INIT(srv6_constructor) {

modules/srv6/control_local.c

@@ -176,7 +176,6 @@ static struct gr_module srv6_local_module = {
 	.name = "srv6_local",
 	.init = srv6_init,
 	.fini = srv6_fini,
-	.fini_prio = 1000,
 };
 
 RTE_INIT(srv6_constructor) {