[PATCH 10/15] netconfig: Wait for link-local address before DHCPv6

Keep one global rtnl instance instead of one per interface so that we
can have just one RTM_NEWADDR listener.  On l_netconfig_start dump
existing IPv6 addresses and wait until a link-local address is added so
it can be used as the source address for our DHCPv6 frames.
---
 ell/netconfig.c | 149 +++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 146 insertions(+), 3 deletions(-)

diff --git a/ell/netconfig.c b/ell/netconfig.c
index 63ad154..e3ca85a 100644
--- a/ell/netconfig.c
+++ b/ell/netconfig.c
@@ -65,6 +65,7 @@ struct l_netconfig {
 	char **v6_domain_names_override;
 
 	struct l_netlink *rtnl;
+	unsigned int ifaddr6_dump_cmd_id;
 	bool started;
 	struct l_idle *do_static_work;
 	bool v4_configured;
@@ -115,6 +116,9 @@ union netconfig_addr {
 	struct in6_addr v6;
 };
 
+static struct l_queue *addr_wait_list;
+static unsigned int rtnl_id;
+
 static void netconfig_update_cleanup(struct l_netconfig *nc)
 {
 	l_queue_clear(nc->addresses.added, NULL);
@@ -1202,6 +1206,117 @@ static void netconfig_do_static_config(struct l_idle *idle, void *user_data)
 	}
 }
 
+static void netconfig_rtnl_unregister(void *user_data)
+{
+	struct l_netlink *rtnl = user_data;
+
+	if (!addr_wait_list || !l_queue_isempty(addr_wait_list))
+		return;
+
+	l_queue_destroy(l_steal_ptr(addr_wait_list), NULL);
+	l_netlink_unregister(rtnl, rtnl_id);
+	rtnl_id = 0;
+}
+
+static void netconfig_addr_wait_unregister(struct l_netconfig *nc,
+						bool in_notify)
+{
+	if (nc->ifaddr6_dump_cmd_id) {
+		unsigned int cmd_id = nc->ifaddr6_dump_cmd_id;
+
+		nc->ifaddr6_dump_cmd_id = 0;
+		l_netlink_cancel(nc->rtnl, cmd_id);
+	}
+
+	if (!l_queue_remove(addr_wait_list, nc))
+		return;
+
+	if (!l_queue_isempty(addr_wait_list))
+		return;
+
+	/* We can't do l_netlink_unregister() inside a notification */
+	if (in_notify)
+		l_idle_oneshot(netconfig_rtnl_unregister, nc->rtnl, NULL);
+	else
+		netconfig_rtnl_unregister(nc->rtnl);
+}
+
+static void netconfig_ifaddr_ipv6_added(struct l_netconfig *nc,
+					const struct ifaddrmsg *ifa,
+					uint32_t len)
+{
+	struct in6_addr in6;
+	_auto_(l_free) char *ip = NULL;
+
+	if (ifa->ifa_flags & IFA_F_TENTATIVE)
+		return;
+
+	if (!nc->started)
+		return;
+
+	l_rtnl_ifaddr6_extract(ifa, len, &ip);
+	inet_pton(AF_INET6, ip, &in6);
+
+	if (!IN6_IS_ADDR_LINKLOCAL(&in6))
+		return;
+
+	netconfig_addr_wait_unregister(nc, true);
+
+	l_dhcp6_client_set_link_local_address(nc->dhcp6_client, ip);
+
+	/*
+	 * Only now that we have a link-local address start actual DHCPv6
+	 * setup.
+	 */
+	if (l_dhcp6_client_start(nc->dhcp6_client))
+		return;
+
+	netconfig_emit_event(nc, AF_INET6, L_NETCONFIG_EVENT_FAILED);
+}
+
+static void netconfig_ifaddr_ipv6_notify(uint16_t type, const void *data,
+						uint32_t len, void *user_data)
+{
+	const struct ifaddrmsg *ifa = data;
+	uint32_t bytes = len - NLMSG_ALIGN(sizeof(struct ifaddrmsg));
+	const struct l_queue_entry *entry, *next;
+
+	switch (type) {
+	case RTM_NEWADDR:
+		/* Iterate safely since elements may be removed */
+		for (entry = l_queue_get_entries(addr_wait_list); entry;
+				entry = next) {
+			struct l_netconfig *nc = entry->data;
+
+			next = entry->next;
+			netconfig_ifaddr_ipv6_added(nc, ifa, bytes);
+		}
+
+		break;
+	}
+}
+
+static void netconfig_ifaddr_ipv6_dump_cb(int error, uint16_t type,
+						const void *data, uint32_t len,
+						void *user_data)
+{
+	struct l_netconfig *nc = user_data;
+
+	if (!nc->ifaddr6_dump_cmd_id || !nc->started)
+		return;
+
+	if (error) {
+		netconfig_addr_wait_unregister(nc, false);
+		netconfig_emit_event(nc, AF_INET6, L_NETCONFIG_EVENT_FAILED);
+		return;
+	}
+
+	if (type != RTM_NEWADDR)
+		return;
+
+	netconfig_ifaddr_ipv6_notify(type, data, len, user_data);
+}
+
 LIB_EXPORT bool l_netconfig_start(struct l_netconfig *netconfig)
 {
 	if (unlikely(!netconfig || netconfig->started))
@@ -1244,14 +1359,40 @@ configure_ipv6:
 		goto done;
 	}
 
-	if (!l_dhcp6_client_start(netconfig->dhcp6_client))
-		goto stop_ipv4;
+	/*
+	 * We only care about being on addr_wait_list if we're waiting for
+	 * the link-local address for DHCP6.  Add ourself to the list here
+	 * before we start the dump, instead of after it ends, to eliminate
+	 * the possibility of missing an RTM_NEWADDR between the end of
+	 * the dump command and registering for the events.
+	 */
+	if (!addr_wait_list) {
+		addr_wait_list = l_queue_new();
+
+		rtnl_id = l_netlink_register(l_rtnl_get(&netconfig->rtnl),
+						RTNLGRP_IPV6_IFADDR,
+						netconfig_ifaddr_ipv6_notify,
+						netconfig, NULL);
+		if (!rtnl_id)
+			goto unregister;
+	}
+
+	netconfig->ifaddr6_dump_cmd_id = l_rtnl_ifaddr6_dump(
+						l_rtnl_get(&netconfig->rtnl),
+						netconfig_ifaddr_ipv6_dump_cb,
+						netconfig, NULL);
+	if (!netconfig->ifaddr6_dump_cmd_id)
+		goto unregister;
+
+	l_queue_push_tail(addr_wait_list, netconfig);
 
 done:
 	netconfig->started = true;
 	return true;
 
-stop_ipv4:
+unregister:
+	netconfig_addr_wait_unregister(netconfig, false);
+
 	if (netconfig->v4_enabled) {
 		if (netconfig->v4_static_addr)
 			l_idle_remove(l_steal_ptr(netconfig->do_static_work));
@@ -1275,6 +1416,8 @@ LIB_EXPORT void l_netconfig_stop(struct l_netconfig *netconfig)
 	if (netconfig->signal_expired_work)
 		l_idle_remove(l_steal_ptr(netconfig->signal_expired_work));
 
+	netconfig_addr_wait_unregister(netconfig, false);
+
 	netconfig_update_cleanup(netconfig);
 	l_queue_clear(netconfig->routes.current,
 			(l_queue_destroy_func_t) l_rtnl_route_free);
-- 
2.32.0