core: truncate parent ifname when constructing virtual ifname for VLAN

https://bugzilla.redhat.com/show_bug.cgi?id=1300755

src/NetworkManagerUtils.c

@@ -2141,8 +2141,32 @@ nm_utils_complete_generic (NMConnection *connection,
 char *
 nm_utils_new_vlan_name (const char *parent_iface, guint32 vlan_id)
 {
-	/* Basically VLAN_NAME_TYPE_RAW_PLUS_VID_NO_PAD */
+	guint id_len;
-	return g_strdup_printf ("%s.%d", parent_iface, vlan_id);
+	gsize parent_len;
+	char *ifname;
+
+	g_return_val_if_fail (parent_iface && *parent_iface, NULL);
+
+	if (vlan_id < 10) {
+		g_return_val_if_fail (vlan_id > 0, NULL);
+		id_len = 2;
+	} else if (vlan_id < 100)
+		id_len = 3;
+	else if (vlan_id < 1000)
+		id_len = 4;
+	else {
+		g_return_val_if_fail (vlan_id < 4096, NULL);
+		id_len = 5;
+	}
+
+	ifname = g_new (char, IFNAMSIZ);
+
+	parent_len = strlen (parent_iface);
+	parent_len = MIN (parent_len, IFNAMSIZ - 1 - id_len);
+	memcpy (ifname, parent_iface, parent_len);
+	g_snprintf (&ifname[parent_len], IFNAMSIZ - parent_len, ".%u", vlan_id);
+
+	return ifname;
 }
 
 /**

src/tests/test-general-with-expect.c

@@ -855,6 +855,48 @@ test_nm_multi_index (void)
 
 /*******************************************/
 
+static void
+test_nm_utils_new_vlan_name (void)
+{
+	guint i, j;
+	const char *parent_names[] = {
+		"a",
+		"a2",
+		"a23",
+		"a23456789",
+		"a2345678901",
+		"a23456789012",
+		"a234567890123",
+		"a2345678901234",
+		"a23456789012345",
+		"a234567890123456",
+		"a2345678901234567",
+	};
+
+	for (i = 0; i < G_N_ELEMENTS (parent_names); i++) {
+		for (j = 0; j < 10; j++) {
+			gs_free char *ifname = NULL;
+			gs_free char *vlan_id_s = NULL;
+			guint vlan_id;
+
+			vlan_id = nmtst_get_rand_int () % 4096;
+
+			vlan_id_s = g_strdup_printf (".%d", vlan_id);
+
+			ifname = nm_utils_new_vlan_name (parent_names[i], vlan_id);
+			g_assert (ifname && ifname[0]);
+			g_assert_cmpint (strlen (ifname), ==, MIN (15, strlen (parent_names[i]) + strlen (vlan_id_s)));
+			g_assert (g_str_has_suffix (ifname, vlan_id_s));
+			g_assert (ifname[strlen (ifname) - strlen (vlan_id_s)] == '.');
+			g_assert (strncmp (ifname, parent_names[i], strlen (ifname) - strlen (vlan_id_s)) == 0);
+			if (!g_str_has_prefix (ifname, parent_names[i]))
+				g_assert_cmpint (strlen (ifname), ==, 15);
+		}
+	}
+}
+
+/*******************************************/
+
 NMTST_DEFINE ();
 
 int
@@ -867,6 +909,7 @@ main (int argc, char **argv)
 	g_test_add_func ("/general/nm_utils_array_remove_at_indexes", test_nm_utils_array_remove_at_indexes);
 	g_test_add_func ("/general/nm_ethernet_address_is_valid", test_nm_ethernet_address_is_valid);
 	g_test_add_func ("/general/nm_multi_index", test_nm_multi_index);
+	g_test_add_func ("/general/nm_utils_new_vlan_name", test_nm_utils_new_vlan_name);
 
 	return g_test_run ();
 }