keyfile: emit a warning when the gateway is set in different keys

The gateway can be set both in the "address*" and and in the "gateway"
keys. Raise a warning when it is set multiple times to different
values.

src/core/settings/plugins/keyfile/tests/keyfiles/Test_Duplicate_Gateways

@@ -0,0 +1,17 @@
+[connection]
+id=Test Duplicate Gateways
+uuid=5e2a7b1e-e4c8-4964-88c4-ca7255471aa1
+type=802-3-ethernet
+autoconnect=true
+timestamp=6654332
+
+[ipv4]
+method=manual
+address1=192.168.0.5/24;192.168.0.254
+address2=192.0.2.1/16
+gateway=192.168.0.253
+
+[ipv6]
+method=manual
+gateway=fd01::bbbb
+address1=fd01::1/64;fd01::aaaa

src/core/settings/plugins/keyfile/tests/test-keyfile-settings.c

@@ -403,6 +403,34 @@ test_read_valid_wired_connection(void)
     nmtst_assert_route_attribute_string(route, NM_IP_ROUTE_ATTRIBUTE_FROM, "abce::/63");
 }
 
+static void
+test_read_duplicate_gateways(void)
+{
+    gs_unref_object NMConnection *connection = NULL;
+    NMSettingIPConfig            *s_ip4;
+    NMSettingIPConfig            *s_ip6;
+
+    NMTST_EXPECT_NM_WARN(
+        "*ipv4* ignoring gateway * from \"address*\" keys because the \"gateway\" key is set*");
+    NMTST_EXPECT_NM_WARN(
+        "*ipv6* ignoring gateway * from \"address*\" keys because the \"gateway\" key is set*");
+    connection = keyfile_read_connection_from_file(TEST_KEYFILES_DIR "/Test_Duplicate_Gateways");
+    g_test_assert_expected_messages();
+
+    s_ip4 = nm_connection_get_setting_ip4_config(connection);
+    g_assert(s_ip4);
+    g_assert_cmpint(nm_setting_ip_config_get_num_addresses(s_ip4), ==, 2);
+    check_ip_address(s_ip4, 0, "192.168.0.5", 24);
+    check_ip_address(s_ip4, 1, "192.0.2.1", 16);
+    g_assert_cmpstr(nm_setting_ip_config_get_gateway(s_ip4), ==, "192.168.0.253");
+
+    s_ip6 = nm_connection_get_setting_ip6_config(connection);
+    g_assert(s_ip6);
+    g_assert_cmpint(nm_setting_ip_config_get_num_addresses(s_ip6), ==, 1);
+    check_ip_address(s_ip6, 0, "fd01::1", 64);
+    g_assert_cmpstr(nm_setting_ip_config_get_gateway(s_ip6), ==, "fd01::bbbb");
+}
+
 static void
 add_one_ip_address(NMSettingIPConfig *s_ip, const char *addr, guint32 prefix)
 {
@@ -2899,6 +2927,8 @@ main(int argc, char **argv)
     g_test_add_func("/keyfile/test_read_valid_wired_connection", test_read_valid_wired_connection);
     g_test_add_func("/keyfile/test_write_wired_connection", test_write_wired_connection);
 
+    g_test_add_func("/keyfile/test_read_duplicate_gateways", test_read_duplicate_gateways);
+
     g_test_add_func("/keyfile/test_read_ip6_wired_connection", test_read_ip6_wired_connection);
     g_test_add_func("/keyfile/test_write_ip6_wired_connection", test_write_ip6_wired_connection);
 

src/libnm-core-impl/nm-keyfile.c

@@ -938,6 +938,31 @@ _build_list_create(GKeyFile     *keyfile,
     return g_steal_pointer(&build_list);
 }
 
+static void
+gateway_parser(KeyfileReaderInfo *info, NMSetting *setting, const char *key)
+{
+    const char   *setting_name = nm_setting_get_name(setting);
+    gs_free char *gateway      = NULL;
+    const char   *old_gateway;
+
+    gateway = nm_keyfile_plugin_kf_get_string(info->keyfile, setting_name, key, NULL);
+    if (!gateway)
+        return;
+
+    old_gateway = nm_setting_ip_config_get_gateway(NM_SETTING_IP_CONFIG(setting));
+    if (old_gateway && !nm_streq0(gateway, old_gateway)) {
+        read_handle_warn(info,
+                         key,
+                         NM_SETTING_IP_CONFIG_GATEWAY,
+                         NM_KEYFILE_WARN_SEVERITY_WARN,
+                         _("ignoring gateway \"%s\" from \"address*\" keys because the "
+                           "\"gateway\" key is set"),
+                         old_gateway);
+    }
+
+    g_object_set(setting, NM_SETTING_IP_CONFIG_GATEWAY, gateway, NULL);
+}
+
 static void
 ip_address_or_route_parser(KeyfileReaderInfo *info, NMSetting *setting, const char *setting_key)
 {
@@ -3055,6 +3080,7 @@ static const ParseInfoSetting *const parse_infos[_NM_META_SETTING_TYPE_NUM] = {
                                 .parser              = ip_dns_parser,
                                 .writer              = dns_writer, ),
             PARSE_INFO_PROPERTY(NM_SETTING_IP_CONFIG_DNS_OPTIONS, .always_write = TRUE, ),
+            PARSE_INFO_PROPERTY(NM_SETTING_IP_CONFIG_GATEWAY, .parser = gateway_parser, ),
             PARSE_INFO_PROPERTY(NM_SETTING_IP_CONFIG_ROUTES,
                                 .parser_no_check_key = TRUE,
                                 .parser              = ip_address_or_route_parser,
@@ -3082,6 +3108,7 @@ static const ParseInfoSetting *const parse_infos[_NM_META_SETTING_TYPE_NUM] = {
                                 .parser              = ip_dns_parser,
                                 .writer              = dns_writer, ),
             PARSE_INFO_PROPERTY(NM_SETTING_IP_CONFIG_DNS_OPTIONS, .always_write = TRUE, ),
+            PARSE_INFO_PROPERTY(NM_SETTING_IP_CONFIG_GATEWAY, .parser = gateway_parser, ),
             PARSE_INFO_PROPERTY(NM_SETTING_IP_CONFIG_ROUTES,
                                 .parser_no_check_key = TRUE,
                                 .parser              = ip_address_or_route_parser,