ip-pool: Track IPv4 addresses in use

Add the ip-pool submodule that tracks IPv4 addresses in use on the
system for use when selecting the address for a new AP.  l_rtnl_address
is used internally because if we're going to return l_rtnl_address
objects it would be misleading if we didn't fill in all of their
properties like flags etc.

Makefile.am

@@ -243,6 +243,7 @@ src_iwd_SOURCES = src/main.c linux/nl80211.h src/iwd.h src/missing.h \
 					src/eap-wsc.c src/eap-wsc.h \
 					src/wscutil.h src/wscutil.c \
 					src/diagnostic.h src/diagnostic.c \
+					src/ip-pool.h src/ip-pool.c \
 					$(eap_sources) \
 					$(builtin_sources)
 

src/ip-pool.c

@@ -0,0 +1,175 @@
+/*
+ *
+ *  Wireless daemon for Linux
+ *
+ *  Copyright (C) 2021  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 <netinet/in.h>
+#include <arpa/inet.h>
+
+#include <ell/ell.h>
+
+#include "src/util.h"
+#include "src/iwd.h"
+#include "src/module.h"
+#include "src/netdev.h"
+#include "src/ip-pool.h"
+
+struct ip_pool_addr4_record {
+	uint32_t ifindex;
+	struct l_rtnl_address *addr;
+};
+
+static struct l_queue *used_addr4_list;
+static struct l_netlink *rtnl;
+
+static void ip_pool_addr4_record_free(void *data)
+{
+	struct ip_pool_addr4_record *rec = data;
+
+	l_rtnl_address_free(rec->addr);
+	l_free(rec);
+}
+
+static bool ip_pool_addr4_match_ifindex(const void *a, const void *b)
+{
+	const struct ip_pool_addr4_record *addr = a;
+
+	return addr->ifindex == L_PTR_TO_UINT(b);
+}
+
+struct l_rtnl_address *ip_pool_get_addr4(uint32_t ifindex)
+{
+	const struct ip_pool_addr4_record *rec =
+		l_queue_find(used_addr4_list, ip_pool_addr4_match_ifindex,
+				L_UINT_TO_PTR(ifindex));
+
+	return rec ? l_rtnl_address_clone(rec->addr) : 0;
+}
+
+static bool ip_pool_addr4_match_free(void *data, void *user_data)
+{
+	const struct ip_pool_addr4_record *a = data;
+	const struct ip_pool_addr4_record *b = user_data;
+	char a_addr_str[INET_ADDRSTRLEN];
+	char b_addr_str[INET_ADDRSTRLEN];
+
+	if (a->ifindex != b->ifindex ||
+			l_rtnl_address_get_prefix_length(a->addr) !=
+			l_rtnl_address_get_prefix_length(b->addr))
+		return false;
+
+	if (!l_rtnl_address_get_address(a->addr, a_addr_str) ||
+			!l_rtnl_address_get_address(b->addr, b_addr_str) ||
+			strcmp(a_addr_str, b_addr_str))
+		return false;
+
+	ip_pool_addr4_record_free(data);
+	return true;
+}
+
+static void ip_pool_addr_notify(uint16_t type, const void *data, uint32_t len,
+				void *user_data)
+{
+	const struct ifaddrmsg *ifa = data;
+	struct l_rtnl_address *addr;
+
+	if (ifa->ifa_family != AF_INET || ifa->ifa_prefixlen < 1)
+		return;
+
+	len -= NLMSG_ALIGN(sizeof(struct ifaddrmsg));
+
+	addr = l_rtnl_ifaddr_extract(ifa, len);
+	if (!addr)
+		return;
+
+	if (type == RTM_NEWADDR) {
+		struct ip_pool_addr4_record *rec;
+
+		rec = l_new(struct ip_pool_addr4_record, 1);
+		rec->ifindex = ifa->ifa_index;
+		rec->addr = l_steal_ptr(addr);
+		l_queue_push_tail(used_addr4_list, rec);
+	} else if (type == RTM_DELADDR) {
+		struct ip_pool_addr4_record rec;
+
+		rec.ifindex = ifa->ifa_index;
+		rec.addr = addr;
+
+		l_queue_foreach_remove(used_addr4_list,
+					ip_pool_addr4_match_free, &rec);
+	}
+
+	l_rtnl_address_free(addr);
+}
+
+static void ip_pool_addr4_dump_cb(int error,
+					uint16_t type, const void *data,
+					uint32_t len, void *user_data)
+{
+	if (error) {
+		l_error("addr4_dump_cb: %s (%i)", strerror(-error), -error);
+		return;
+	}
+
+	ip_pool_addr_notify(type, data, len, user_data);
+}
+
+static int ip_pool_init(void)
+{
+	const struct l_settings *settings = iwd_get_config();
+	bool netconfig_enabled;
+
+	if (!l_settings_get_bool(settings, "General",
+				"EnableNetworkConfiguration",
+				&netconfig_enabled))
+		netconfig_enabled = false;
+
+	if (!netconfig_enabled)
+		return 0;
+
+	rtnl = iwd_get_rtnl();
+
+	if (!l_netlink_register(rtnl, RTNLGRP_IPV4_IFADDR,
+				ip_pool_addr_notify, NULL, NULL)) {
+		l_error("Failed to register for RTNL link notifications");
+		return -EIO;
+	}
+
+	if (!l_rtnl_ifaddr4_dump(rtnl, ip_pool_addr4_dump_cb, NULL, NULL)) {
+		l_error("Sending the IPv4 addr dump req failed");
+		return -EIO;
+	}
+
+	used_addr4_list = l_queue_new();
+	return 0;
+}
+
+static void ip_pool_exit(void)
+{
+	l_queue_destroy(used_addr4_list, ip_pool_addr4_record_free);
+	used_addr4_list = NULL;
+}
+
+IWD_MODULE(ip_pool, ip_pool_init, ip_pool_exit)

src/ip-pool.h

@@ -0,0 +1,23 @@
+/*
+ *
+ *  Wireless daemon for Linux
+ *
+ *  Copyright (C) 2021  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
+ *
+ */
+
+struct l_rtnl_address *ip_pool_get_addr4(uint32_t ifindex);