netconfig: Subscribe for IPv4 link address notifications

iwd keeps track of the addresses assigned to the managed
interfaces. The list of assigned IPv4/IPv6 addresses is stored
in ifaddr_list inside of netconfig. The tracking of the IP
addresses will help to remove them from an interface once they
are no longer valid.

src/netconfig.c

@@ -30,18 +30,47 @@
 #include <ell/ell.h>
 
 #include "src/iwd.h"
+#include "src/rtnlutil.h"
 #include "src/netconfig.h"
 
 struct netconfig {
 	uint32_t ifindex;
+	struct l_queue *ifaddr_list;
 };
 
+struct netconfig_ifaddr {
+	uint8_t family;
+	uint8_t prefix_len;
+	char *ip;
+	char *broadcast;
+};
+
+static struct l_netlink *rtnl;
 static struct l_queue *netconfig_list;
 
+static void do_debug(const char *str, void *user_data)
+{
+	const char *prefix = user_data;
+
+	l_info("%s%s", prefix, str);
+}
+
+static void netconfig_ifaddr_destroy(void *data)
+{
+	struct netconfig_ifaddr *ifaddr = data;
+
+	l_free(ifaddr->ip);
+	l_free(ifaddr->broadcast);
+
+	l_free(ifaddr);
+}
+
 static void netconfig_destroy(void *data)
 {
 	struct netconfig *netconfig = data;
 
+	l_queue_destroy(netconfig->ifaddr_list, netconfig_ifaddr_destroy);
+
 	l_free(netconfig);
 }
 
@@ -73,6 +102,99 @@ static struct netconfig *netconfig_find(uint32_t ifindex)
 	return NULL;
 }
 
+static struct netconfig_ifaddr *netconfig_ifaddr_find(
+					const struct netconfig *netconfig,
+					uint8_t family, uint8_t prefix_len,
+					const char *ip)
+{
+	const struct l_queue_entry *entry;
+
+	for (entry = l_queue_get_entries(netconfig->ifaddr_list); entry;
+							entry = entry->next) {
+		struct netconfig_ifaddr *ifaddr = entry->data;
+
+		if (ifaddr->family != family)
+			continue;
+
+		if (ifaddr->prefix_len != prefix_len)
+			continue;
+
+		if (strcmp(ifaddr->ip, ip))
+			continue;
+
+		return ifaddr;
+	}
+
+	return NULL;
+}
+
+static void netconfig_ifaddr_added(struct netconfig *netconfig,
+					const struct ifaddrmsg *ifa, int bytes)
+{
+	struct netconfig_ifaddr *ifaddr;
+	char *label;
+
+	ifaddr = l_new(struct netconfig_ifaddr, 1);
+	ifaddr->family = ifa->ifa_family;
+	ifaddr->prefix_len = ifa->ifa_prefixlen;
+
+	rtnl_ifaddr_extract(ifa, bytes, &label, &ifaddr->ip,
+							&ifaddr->broadcast);
+
+	l_debug("%s: ifaddr %s/%u broadcast %s", label, ifaddr->ip,
+					ifaddr->prefix_len, ifaddr->broadcast);
+	l_free(label);
+
+	l_queue_push_tail(netconfig->ifaddr_list, ifaddr);
+}
+
+static void netconfig_ifaddr_deleted(struct netconfig *netconfig,
+					const struct ifaddrmsg *ifa, int bytes)
+{
+	struct netconfig_ifaddr *ifaddr;
+	char *ip;
+
+	rtnl_ifaddr_extract(ifa, bytes, NULL, &ip, NULL);
+
+	ifaddr = netconfig_ifaddr_find(netconfig, ifa->ifa_family,
+							ifa->ifa_prefixlen, ip);
+
+	l_free(ip);
+
+	if (!ifaddr)
+		return;
+
+	l_debug("ifaddr %s/%u", ifaddr->ip, ifaddr->prefix_len);
+
+	l_queue_remove(netconfig->ifaddr_list, ifaddr);
+
+	netconfig_ifaddr_destroy(ifaddr);
+}
+
+static void netconfig_ifaddr_notify(uint16_t type, const void *data,
+						uint32_t len, void *user_data)
+{
+	const struct ifaddrmsg *ifa = data;
+	struct netconfig *netconfig;
+	unsigned int bytes;
+
+	netconfig = netconfig_find(ifa->ifa_index);
+	if (!netconfig)
+		/* Ignore the interfaces which aren't managed by iwd. */
+		return;
+
+	bytes = len - NLMSG_ALIGN(sizeof(struct ifaddrmsg));
+
+	switch (type) {
+	case RTM_NEWADDR:
+		netconfig_ifaddr_added(netconfig, ifa, bytes);
+		break;
+	case RTM_DELADDR:
+		netconfig_ifaddr_deleted(netconfig, ifa, bytes);
+		break;
+	}
+}
+
 bool netconfig_ifindex_add(uint32_t ifindex)
 {
 	struct netconfig *netconfig;
@@ -88,6 +210,7 @@ bool netconfig_ifindex_add(uint32_t ifindex)
 
 	netconfig = l_new(struct netconfig, 1);
 	netconfig->ifindex = ifindex;
+	netconfig->ifaddr_list = l_queue_new();
 
 	l_queue_push_tail(netconfig_list, netconfig);
 
@@ -116,6 +239,7 @@ bool netconfig_ifindex_remove(uint32_t ifindex)
 static int netconfig_init(void)
 {
 	bool enabled;
+	uint32_t r;
 
 	if (netconfig_list)
 		return -EALREADY;
@@ -128,6 +252,26 @@ static int netconfig_init(void)
 		return false;
 	}
 
+	rtnl = l_netlink_new(NETLINK_ROUTE);
+	if (!rtnl) {
+		l_error("netconfig: Failed to open route netlink socket");
+		return -EPERM;
+	}
+
+	if (getenv("IWD_RTNL_DEBUG"))
+		l_netlink_set_debug(rtnl, do_debug, "[NETCONFIG RTNL] ", NULL);
+
+	r = l_netlink_register(rtnl, RTNLGRP_IPV4_IFADDR,
+					netconfig_ifaddr_notify, NULL, NULL);
+	if (!r) {
+		l_error("netconfig: Failed to register for RTNL link address"
+							" notifications.");
+		l_netlink_destroy(rtnl);
+		rtnl = NULL;
+
+		return r;
+	}
+
 	netconfig_list = l_queue_new();
 
 	return 0;
@@ -138,6 +282,9 @@ static void netconfig_exit(void)
 	if (!netconfig_list)
 		return;
 
+	l_netlink_destroy(rtnl);
+	rtnl = NULL;
+
 	l_queue_destroy(netconfig_list, netconfig_destroy);
 }