iprule: rework interface based rules to handle dynamic interfaces

Previous netifd would only apply `ip rule`s while config phase.
If the iprule is depending on an interface (iif or oif), the rule
will fail if the interface is not up.

Allow iprules to track interfaces and their devices by using
the interface events.

Fixes: FS#1571
Acked-by: Hans Dedecker <dedeckeh@gmail.com>
Signed-off-by: Alexander Couzens <lynxis@fe80.eu>

iprule.c

@@ -2,6 +2,7 @@
  * netifd - network interface daemon
  * Copyright (C) 2012 Felix Fietkau <nbd@openwrt.org>
  * Copyright (C) 2013 Jo-Philipp Wich <jow@openwrt.org>
+ * Copyright (C) 2018 Alexander Couzens <lynxis@fe80.eu>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2
@@ -12,6 +13,7 @@
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  */
+#include <assert.h>
 #include <string.h>
 #include <stdlib.h>
 #include <stdio.h>
@@ -66,6 +68,16 @@ const struct uci_blob_param_list rule_attr_list = {
 	.params = rule_attr,
 };
 
+/* interface based rules are dynamic. */
+static bool rule_ready(struct iprule *rule) {
+	if (rule->flags & IPRULE_OUT && rule->out_dev == NULL)
+		return false;
+
+	if (rule->flags & IPRULE_IN && rule->in_dev == NULL)
+		return false;
+
+	return true;
+}
 
 static bool
 iprule_parse_mark(const char *mark, struct iprule *rule)
@@ -97,13 +109,102 @@ iprule_parse_mark(const char *mark, struct iprule *rule)
 	return true;
 }
 
+/* called on interface changes of the incoming interface */
+static void rule_in_cb(
+		struct interface_user *dep,
+		struct interface *iface,
+		enum interface_event ev)
+{
+	struct iprule *rule = container_of(dep, struct iprule, in_iface_user);
+
+	switch (ev) {
+	case IFEV_UP:
+		if (!iface->l3_dev.dev)
+			break;
+		memcpy(rule->in_dev, iface->l3_dev.dev->ifname, sizeof(rule->in_dev));
+		if (rule_ready(rule))
+			system_add_iprule(rule);
+		break;
+	case IFEV_DOWN:
+	case IFEV_UP_FAILED:
+	case IFEV_FREE:
+		if (rule_ready(rule))
+			system_del_iprule(rule);
+		rule->in_dev[0] = 0;
+		break;
+	default:
+		break;
+	}
+}
+
+/* called on interface changes of the outgoing interface */
+static void rule_out_cb(
+		struct interface_user *dep,
+		struct interface *iface,
+		enum interface_event ev)
+{
+	struct iprule *rule = container_of(dep, struct iprule, out_iface_user);
+
+	switch (ev) {
+	case IFEV_UP:
+		if (!iface->l3_dev.dev)
+			break;
+		memcpy(rule->out_dev, iface->l3_dev.dev->ifname, sizeof(rule->out_dev));
+		if (rule_ready(rule))
+			system_add_iprule(rule);
+		break;
+	case IFEV_DOWN:
+	case IFEV_UP_FAILED:
+	case IFEV_FREE:
+		if (rule_ready(rule))
+			system_del_iprule(rule);
+		rule->out_dev[0] = 0;
+		break;
+	default:
+		break;
+	}
+}
+
+/* called on all interface events */
+static void generic_interface_cb(
+		struct interface_user *dep,
+		struct interface *iface,
+		enum interface_event ev)
+{
+	struct iprule *rule;
+
+	if (ev != IFEV_CREATE)
+		return;
+
+	/* add new interfaces to rules */
+	vlist_for_each_element(&iprules, rule, node) {
+		if (rule_ready(rule))
+			continue;
+
+		if (!strcmp(rule->out_iface, iface->name)) {
+			assert(!rule->out_dev);
+			memcpy(rule->out_dev, iface->l3_dev.dev->ifname, sizeof(rule->out_dev));
+			interface_add_user(&rule->out_iface_user, iface);
+		}
+
+		if (!strcmp(rule->in_iface, iface->name)) {
+			assert(!rule->in_dev);
+			memcpy(rule->in_dev, iface->l3_dev.dev->ifname, sizeof(rule->in_dev));
+			interface_add_user(&rule->in_iface_user, iface);
+		}
+	}
+}
+
+struct interface_user generic_listener = {
+	.cb = generic_interface_cb
+};
+
 void
 iprule_add(struct blob_attr *attr, bool v6)
 {
-	struct interface *iif = NULL, *oif = NULL;
 	struct blob_attr *tb[__RULE_MAX], *cur;
-	struct interface *iface;
 	struct iprule *rule;
+	char *iface_name;
 	int af = v6 ? AF_INET6 : AF_INET;
 
 	blobmsg_parse(rule_attr, __RULE_MAX, tb, blobmsg_data(attr), blobmsg_data_len(attr));
@@ -119,26 +220,16 @@ iprule_add(struct blob_attr *attr, bool v6)
 		rule->invert = blobmsg_get_bool(cur);
 
 	if ((cur = tb[RULE_INTERFACE_IN]) != NULL) {
-		iif = vlist_find(&interfaces, blobmsg_data(cur), iface, node);
-
-		if (!iif || !iif->l3_dev.dev) {
-			DPRINTF("Failed to resolve device of network: %s\n", (char *) blobmsg_data(cur));
-			goto error;
-		}
-
-		memcpy(rule->in_dev, iif->l3_dev.dev->ifname, sizeof(rule->in_dev));
+		iface_name = calloc(1, strlen(blobmsg_data(cur)) + 1);
+		rule->in_iface = strcpy(iface_name, blobmsg_data(cur));
+		rule->in_iface_user.cb = &rule_in_cb;
 		rule->flags |= IPRULE_IN;
 	}
 
 	if ((cur = tb[RULE_INTERFACE_OUT]) != NULL) {
-		oif = vlist_find(&interfaces, blobmsg_data(cur), iface, node);
-
-		if (!oif || !oif->l3_dev.dev) {
-			DPRINTF("Failed to resolve device of network: %s\n", (char *) blobmsg_data(cur));
-			goto error;
-		}
-
-		memcpy(rule->out_dev, oif->l3_dev.dev->ifname, sizeof(rule->out_dev));
+		iface_name = calloc(1, strlen(blobmsg_data(cur)) + 1);
+		rule->out_iface = strcpy(iface_name, blobmsg_data(cur));
+		rule->out_iface_user.cb = &rule_out_cb;
 		rule->flags |= IPRULE_OUT;
 	}
 
@@ -238,6 +329,31 @@ rule_cmp(const void *k1, const void *k2, void *ptr)
 	return memcmp(k1, k2, sizeof(struct iprule)-offsetof(struct iprule, flags));
 }
 
+static void deregister_interfaces(struct iprule *rule)
+{
+	if (rule->flags & IPRULE_IN && rule->in_iface_user.iface)
+		interface_remove_user(&rule->in_iface_user);
+
+	if (rule->flags & IPRULE_OUT && rule->out_iface_user.iface)
+		interface_remove_user(&rule->out_iface_user);
+}
+
+static void register_interfaces(struct iprule *rule)
+{
+	struct interface *iface, *tmp;
+
+	if (rule->flags & IPRULE_IN) {
+		tmp = vlist_find(&interfaces, rule->in_iface, iface, node);
+		if (tmp)
+			interface_add_user(&rule->in_iface_user, tmp);
+	}
+	if (rule->flags & IPRULE_OUT) {
+		tmp = vlist_find(&interfaces, rule->out_iface, iface, node);
+		if (tmp)
+			interface_add_user(&rule->out_iface_user, tmp);
+	}
+}
+
 static void
 iprule_update_rule(struct vlist_tree *tree,
 			struct vlist_node *node_new, struct vlist_node *node_old)
@@ -248,16 +364,34 @@ iprule_update_rule(struct vlist_tree *tree,
 	rule_new = container_of(node_new, struct iprule, node);
 
 	if (node_old) {
-		system_del_iprule(rule_old);
+		if (rule_ready(rule_old))
+			system_del_iprule(rule_old);
+
+		if (rule_old->flags & (IPRULE_IN | IPRULE_OUT))
+			deregister_interfaces(rule_old);
+
+		if (rule_old->in_iface)
+			free(rule_old->in_iface);
+
+		if (rule_old->out_iface)
+			free(rule_old->out_iface);
+
 		free(rule_old);
 	}
 
-	if (node_new)
-		system_add_iprule(rule_new);
+	if (node_new) {
+		/* interface based rules calls system_add_iprule over the event cb */
+		if (rule_new->flags & (IPRULE_IN | IPRULE_OUT)) {
+			register_interfaces(rule_new);
+		} else {
+			system_add_iprule(rule_new);
+		}
+	}
 }
 
 static void __init
 iprule_init_list(void)
 {
 	vlist_init(&iprules, rule_cmp, iprule_update_rule);
+	interface_add_user(&generic_listener, NULL);
 }

iprule.h

@@ -74,6 +74,15 @@ struct iprule {
 
 	bool invert;
 
+	/* uci interface name */
+	char *in_iface;
+	char *out_iface;
+
+	/* to receive interface events */
+	struct interface_user in_iface_user;
+	struct interface_user out_iface_user;
+
+	/* device name */
 	char in_dev[IFNAMSIZ + 1];
 	char out_dev[IFNAMSIZ + 1];