netconfig: Track gateway address strings

Cache the latest v4 and v6 gateway IP string in struct netconfig state
to be able to more easily detect changes in those values in future
commits and perhaps to simplify the ..._routes_install functions.
netconfig_ipv4_get_gateway's out_mac parameter can now be NULL.  While
editing that function fix a small formatting annoyance.

src/netconfig.c

@@ -63,6 +63,8 @@ struct netconfig {
 	char **dns6_overrides;
 	char *mdns;
 	struct ie_fils_ip_addr_response_info *fils_override;
+	char *v4_gateway_str;
+	char *v6_gateway_str;
 
 	const struct l_settings *active_settings;
 
@@ -510,6 +512,7 @@ no_prefix_len:
 
 static struct l_rtnl_route *netconfig_get_static6_gateway(
 						struct netconfig *netconfig,
+						char **out_str,
 						const uint8_t **out_mac)
 {
 	L_AUTO_FREE_VAR(char *, gateway);
@@ -540,6 +543,7 @@ static struct l_rtnl_route *netconfig_get_static6_gateway(
 
 	l_rtnl_route_set_priority(ret, ROUTE_PRIORITY_OFFSET);
 	l_rtnl_route_set_protocol(ret, RTPROT_STATIC);
+	*out_str = l_steal_ptr(gateway);
 	*out_mac = mac;
 
 	return ret;
@@ -923,7 +927,9 @@ static void netconfig_ipv6_ifaddr_add_cmd_cb(int error, uint16_t type,
 		return;
 	}
 
-	gateway = netconfig_get_static6_gateway(netconfig, &gateway_mac);
+	gateway = netconfig_get_static6_gateway(netconfig,
+						&netconfig->v6_gateway_str,
+						&gateway_mac);
 	if (gateway) {
 		netconfig->route6_add_cmd_id = l_rtnl_route_add(rtnl,
 							netconfig->ifindex,
@@ -980,10 +986,24 @@ static void netconfig_ipv4_dhcp_event_handler(struct l_dhcp_client *client,
 					netconfig->v4_address,
 					netconfig_ifaddr_del_cmd_cb,
 					netconfig, NULL));
-		l_rtnl_address_free(netconfig->v4_address);
 		/* Fall through. */
 	case L_DHCP_CLIENT_EVENT_LEASE_OBTAINED:
-		netconfig->v4_address = netconfig_get_dhcp4_address(netconfig);
+	{
+		char *gateway_str;
+		struct l_rtnl_address *address;
+
+		gateway_str = netconfig_ipv4_get_gateway(netconfig, NULL);
+		if (l_streq0(netconfig->v4_gateway_str, gateway_str))
+			l_free(gateway_str);
+		else {
+			l_free(netconfig->v4_gateway_str);
+			netconfig->v4_gateway_str = gateway_str;
+		}
+
+		address = netconfig_get_dhcp4_address(netconfig);
+		l_rtnl_address_free(netconfig->v4_address);
+		netconfig->v4_address = address;
+
 		if (!netconfig->v4_address) {
 			l_error("netconfig: Failed to obtain IP addresses from "
 							"DHCPv4 lease.");
@@ -996,6 +1016,7 @@ static void netconfig_ipv4_dhcp_event_handler(struct l_dhcp_client *client,
 					netconfig_ipv4_ifaddr_add_cmd_cb,
 					netconfig, NULL)));
 		break;
+	}
 	case L_DHCP_CLIENT_EVENT_LEASE_RENEWED:
 		break;
 	case L_DHCP_CLIENT_EVENT_LEASE_EXPIRED:
@@ -1005,6 +1026,7 @@ static void netconfig_ipv4_dhcp_event_handler(struct l_dhcp_client *client,
 					netconfig, NULL));
 		l_rtnl_address_free(netconfig->v4_address);
 		netconfig->v4_address = NULL;
+		l_free(l_steal_ptr(netconfig->v4_gateway_str));
 
 		/* Fall through. */
 	case L_DHCP_CLIENT_EVENT_NO_LEASE:
@@ -1039,6 +1061,18 @@ static void netconfig_dhcp6_event_handler(struct l_dhcp6_client *client,
 		_auto_(l_free) char *addr_str =
 			l_dhcp6_lease_get_address(lease);
 		struct l_rtnl_address *address;
+		struct l_icmp6_client *icmp6 =
+			l_dhcp6_client_get_icmp6(netconfig->dhcp6_client);
+		const struct l_icmp6_router *router =
+			l_icmp6_client_get_router(icmp6);
+		char *gateway_str = l_icmp6_router_get_address(router);
+
+		if (l_streq0(netconfig->v6_gateway_str, gateway_str))
+			l_free(gateway_str);
+		else {
+			l_free(netconfig->v6_gateway_str);
+			netconfig->v6_gateway_str = gateway_str;
+		}
 
 		address = l_rtnl_address_new(addr_str,
 					l_dhcp6_lease_get_prefix_length(lease));
@@ -1055,6 +1089,7 @@ static void netconfig_dhcp6_event_handler(struct l_dhcp6_client *client,
 		netconfig_set_domains(netconfig);
 		l_rtnl_address_free(netconfig->v6_address);
 		netconfig->v6_address = NULL;
+		l_free(l_steal_ptr(netconfig->v6_gateway_str));
 
 		/* Fall through */
 	case L_DHCP6_CLIENT_EVENT_NO_LEASE:
@@ -1091,6 +1126,8 @@ static void netconfig_reset_v4(struct netconfig *netconfig)
 
 		l_acd_destroy(netconfig->acd);
 		netconfig->acd = NULL;
+
+		l_free(l_steal_ptr(netconfig->v4_gateway_str));
 	}
 }
 
@@ -1484,6 +1521,8 @@ bool netconfig_reset(struct netconfig *netconfig)
 
 		sysfs_write_ipv6_setting(netdev_get_name(netdev),
 						"disable_ipv6", "1");
+
+		l_free(l_steal_ptr(netconfig->v6_gateway_str));
 	}
 
 	l_free(l_steal_ptr(netconfig->fils_override));