all: allow configuring default-routes as manual, static routes

Up until now, a default-route (with prefix length zero) could not
be configured directly. The user could only set ipv4.gateway,
ipv4.never-default, ipv4.route-metric and ipv4.route-table to influence
the setting of the default-route (respectively for IPv6).

That is a problematic limitation. For one, whether a route has prefix
length zero or non-zero does not make a fundamental difference. Also,
it makes it impossible to configure all the routing attributes that one can
configure otherwise for static routes. For example, the default-route could
not be configured as "onlink", could not have a special MTU, nor could it be
placed in a dedicated routing table.

Fix that by lifting the restriction. Note that "ipv4.never-default" does
not apply to /0 manual routes. Likewise, the previous manners of
configuring default-routes ("ipv4.gateway") don't conflict with manual
default-routes.

Server-side this all the pieces are already in place to accept a default-route
as static routes. This was done by earlier commits like 5c299454b4
('core: rework tracking of gateway/default-route in ip-config').

A long time ago, NMIPRoute would assert that the prefix length is
positive. That was relaxed by commit a2e93f2de4 ('libnm: allow zero
prefix length for NMIPRoute'), already before 1.0.0. Using libnm from
before 1.0.0 would result in assertion failures.

Note that the default-route-metric-penalty based on connectivity
checking applies to all /0 routes, even these static routes. Be they
added due to DHCP, "ipv4.gateway", "ipv4.routes" or "wireguard.peer-routes".
I wonder whether doing that unconditionally is desirable, and maybe
there should be a way to opt-out/opt-in for the entire profile or even
per-routes.

https://bugzilla.redhat.com/show_bug.cgi?id=1714438

clients/common/nm-meta-setting-desc.c

@@ -367,7 +367,7 @@ _parse_ip_route (int family,
 	}
 	prefix = MAX_PREFIX;
 	if (plen) {
-		if ((prefix = _nm_utils_ascii_str_to_int64 (plen, 10, 1, MAX_PREFIX, -1)) == -1) {
+		if ((prefix = _nm_utils_ascii_str_to_int64 (plen, 10, 0, MAX_PREFIX, -1)) == -1) {
 			g_set_error (error, NM_UTILS_ERROR, NM_UTILS_ERROR_INVALID_ARGUMENT,
 			             _("invalid prefix '%s'; <1-%d> allowed"),
 			             plen, MAX_PREFIX);

libnm-core/nm-keyfile.c

@@ -248,15 +248,16 @@ static gpointer
 build_route (KeyfileReaderInfo *info,
              const char *property_name,
              int family,
-             const char *dest_str, guint32 plen,
-             const char *gateway_str, const char *metric_str)
+             const char *dest_str,
+             guint32 plen,
+             const char *gateway_str,
+             const char *metric_str)
 {
 	NMIPRoute *route;
 	guint32 u32;
 	gint64 metric = -1;
 	GError *error = NULL;
 
-	g_return_val_if_fail (plen, NULL);
 	g_return_val_if_fail (dest_str, NULL);
 
 	/* Next hop */
@@ -294,7 +295,10 @@ build_route (KeyfileReaderInfo *info,
 		metric = u32;
 	}
 
-	route = nm_ip_route_new (family, dest_str, plen, gateway_str,
+	route = nm_ip_route_new (family,
+	                         dest_str,
+	                         plen,
+	                         gateway_str,
 	                         metric,
 	                         &error);
 	if (!route) {
@@ -517,8 +521,7 @@ read_one_ip_address_or_route (KeyfileReaderInfo *info,
 
 	/* parse plen, fallback to defaults */
 	if (plen_str) {
-		if (   !get_one_int (info, property_name, plen_str, ipv6 ? 128 : 32, &plen)
-		    || (route && plen == 0)) {
+		if (!get_one_int (info, property_name, plen_str, ipv6 ? 128 : 32, &plen)) {
 			plen = DEFAULT_PREFIX (route, ipv6);
 			if (   info->error
 			    || !handle_warn (info, property_name, NM_KEYFILE_WARN_SEVERITY_WARN,
@@ -536,12 +539,19 @@ read_one_ip_address_or_route (KeyfileReaderInfo *info,
 
 	/* build the appropriate data structure for NetworkManager settings */
 	if (route) {
-		result = build_route (info, property_name,
+		result = build_route (info,
+		                      property_name,
 		                      ipv6 ? AF_INET6 : AF_INET,
-		                      address_str, plen, gateway_str, metric_str);
+		                      address_str,
+		                      plen,
+		                      gateway_str,
+		                      metric_str);
 	} else {
-		result = build_address (info, ipv6 ? AF_INET6 : AF_INET,
-		                        address_str, plen, property_name);
+		result = build_address (info,
+		                        ipv6 ? AF_INET6 : AF_INET,
+		                        address_str,
+		                        plen,
+		                        property_name);
 		if (!result)
 			return NULL;
 		if (gateway_str)

libnm-core/nm-setting-ip-config.c

@@ -1335,7 +1335,7 @@ nm_ip_route_attribute_validate  (const char *name,
 			if (str) {
 				addr = nm_strndup_a (200, addr, str - addr, &addr_free);
 				str++;
-				if (_nm_utils_ascii_str_to_int64 (str, 10, 1, family == AF_INET ? 32 : 128, -1) < 0) {
+				if (_nm_utils_ascii_str_to_int64 (str, 10, 0, family == AF_INET ? 32 : 128, -1) < 0) {
 					g_set_error (error,
 					             NM_CONNECTION_ERROR,
 					             NM_CONNECTION_ERROR_FAILED,
@@ -5005,15 +5005,6 @@ verify (NMSetting *setting, NMConnection *connection, GError **error)
 			g_prefix_error (error, "%s.%s: ", nm_setting_get_name (setting), NM_SETTING_IP_CONFIG_ROUTES);
 			return FALSE;
 		}
-		if (nm_ip_route_get_prefix (route) == 0) {
-			g_set_error (error,
-			             NM_CONNECTION_ERROR,
-			             NM_CONNECTION_ERROR_INVALID_PROPERTY,
-			             _("%d. route cannot be a default route"),
-			             (int) (i + 1));
-			g_prefix_error (error, "%s.%s: ", nm_setting_get_name (setting), NM_SETTING_IP_CONFIG_ROUTES);
-			return FALSE;
-		}
 	}
 
 	if (priv->routing_rules) {

src/nm-ip4-config.c

@@ -991,8 +991,6 @@ nm_ip4_config_merge_setting (NMIP4Config *self,
 
 		route.plen = nm_ip_route_get_prefix (s_route);
 		nm_assert (route.plen <= 32);
-		if (route.plen == 0)
-			continue;
 
 		nm_ip_route_get_next_hop_binary (s_route, &route.gateway);
 		if (nm_ip_route_get_metric (s_route) == -1)

src/nm-ip6-config.c

@@ -672,8 +672,6 @@ nm_ip6_config_merge_setting (NMIP6Config *self,
 
 		route.plen = nm_ip_route_get_prefix (s_route);
 		nm_assert (route.plen <= 128);
-		if (route.plen == 0)
-			continue;
 
 		nm_ip_route_get_next_hop_binary (s_route, &route.gateway);
 		if (nm_ip_route_get_metric (s_route) == -1)

src/settings/plugins/ifcfg-rh/nms-ifcfg-rh-reader.c

@@ -1116,15 +1116,6 @@ next:
 		         ? info_to->v.addr.plen
 		         : (addr_family == AF_INET ? 32 : 128);
 
-		if (   (   (addr_family == AF_INET  && !info_to->v.addr.addr.addr4)
-		        || (addr_family == AF_INET6 && IN6_IS_ADDR_UNSPECIFIED (&info_to->v.addr.addr.addr6)))
-		    && prefix == 0) {
-			/* we ignore default routes by returning -ERANGE. */
-			g_set_error (error, NM_SETTINGS_ERROR, NM_SETTINGS_ERROR_INVALID_CONNECTION,
-			             "Ignore manual default route");
-			return -ERANGE;
-		}
-
 		route = nm_ip_route_new_binary (addr_family,
 		                                &info_to->v.addr.addr,
 		                                prefix,
@@ -1244,7 +1235,7 @@ read_one_ip4_route (shvarFile *ifcfg,
 		return FALSE;
 	if (has_key) {
 		prefix = nm_utils_ip4_netmask_to_prefix (netmask);
-		if (prefix == 0 || netmask != _nm_utils_ip4_prefix_to_netmask (prefix)) {
+		if (netmask != _nm_utils_ip4_prefix_to_netmask (prefix)) {
 			g_set_error (error, NM_SETTINGS_ERROR, NM_SETTINGS_ERROR_INVALID_CONNECTION,
 			             "Invalid IP4 netmask '%s' \"%s\"", netmask_tag, nm_utils_inet4_ntop (netmask, inet_buf));
 			return FALSE;

src/settings/plugins/ifcfg-rh/tests/test-ifcfg-rh.c

@@ -1520,10 +1520,8 @@ test_read_wired_ipv6_manual (void)
 	NMIPAddress *ip6_addr;
 	NMIPRoute *ip6_route;
 
-	NMTST_EXPECT_NM_WARN ("*ignoring manual default route*");
 	connection = _connection_from_file (TEST_IFCFG_DIR"/ifcfg-test-wired-ipv6-manual",
 	                                    NULL, TYPE_ETHERNET, &unmanaged);
-	g_test_assert_expected_messages ();
 	g_assert (!unmanaged);
 
 	/* ===== CONNECTION SETTING ===== */
@@ -1581,7 +1579,7 @@ test_read_wired_ipv6_manual (void)
 	g_assert_cmpint (nm_ip_address_get_prefix (ip6_addr), ==, 96);
 
 	/* Routes */
-	g_assert_cmpint (nm_setting_ip_config_get_num_routes (s_ip6), ==, 3);
+	g_assert_cmpint (nm_setting_ip_config_get_num_routes (s_ip6), ==, 4);
 	/* Route #1 */
 	ip6_route = nm_setting_ip_config_get_route (s_ip6, 0);
 	g_assert (ip6_route);
@@ -1592,12 +1590,19 @@ test_read_wired_ipv6_manual (void)
 	/* Route #2 */
 	ip6_route = nm_setting_ip_config_get_route (s_ip6, 1);
 	g_assert (ip6_route);
+	g_assert_cmpstr (nm_ip_route_get_dest (ip6_route), ==, "::");
+	g_assert_cmpint (nm_ip_route_get_prefix (ip6_route), ==, 0);
+	g_assert_cmpstr (nm_ip_route_get_next_hop (ip6_route), ==, "dead::beaf");
+	g_assert_cmpint (nm_ip_route_get_metric (ip6_route), ==, -1);
+	/* Route #3 */
+	ip6_route = nm_setting_ip_config_get_route (s_ip6, 2);
+	g_assert (ip6_route);
 	g_assert_cmpstr (nm_ip_route_get_dest (ip6_route), ==, "abbe::cafe");
 	g_assert_cmpint (nm_ip_route_get_prefix (ip6_route), ==, 64);
 	g_assert_cmpstr (nm_ip_route_get_next_hop (ip6_route), ==, NULL);
 	g_assert_cmpint (nm_ip_route_get_metric (ip6_route), ==, 777);
-	/* Route #3 */
-	ip6_route = nm_setting_ip_config_get_route (s_ip6, 2);
+	/* Route #4 */
+	ip6_route = nm_setting_ip_config_get_route (s_ip6, 3);
 	g_assert (ip6_route);
 	g_assert_cmpstr (nm_ip_route_get_dest (ip6_route), ==, "aaaa::cccc");
 	g_assert_cmpint (nm_ip_route_get_prefix (ip6_route), ==, 64);