nmtui: add page for configuring loopback interface

NEWS

@@ -14,6 +14,7 @@ USE AT YOUR OWN RISK.  NOT RECOMMENDED FOR PRODUCTION USE!
 * Add a new "prefix-delegation" setting containing a "subnet-id"
   property that specifies the subnet to choose on the downstream
   interface when using IPv6 prefix delegation.
+* Add support for configuring the loopback interface in nmtui.
 
 =============================================
 NetworkManager-1.52

po/POTFILES.in

@@ -180,6 +180,7 @@ src/nmtui/nmt-page-infiniband.c
 src/nmtui/nmt-page-ip-tunnel.c
 src/nmtui/nmt-page-ip4.c
 src/nmtui/nmt-page-ip6.c
+src/nmtui/nmt-page-loopback.c
 src/nmtui/nmt-page-macsec.c
 src/nmtui/nmt-page-ppp.c
 src/nmtui/nmt-page-team-port.c

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

@@ -3359,6 +3359,8 @@ nm_connection_get_virtual_device_description(NMConnection *connection)
         display_type = _("TUN/TAP");
     else if (nm_streq(type, NM_SETTING_VETH_SETTING_NAME))
         display_type = _("Veth");
+    else if (nm_streq(type, NM_SETTING_LOOPBACK_SETTING_NAME))
+        display_type = _("Loopback");
 
     if (!iface || !display_type)
         return NULL;

src/nmtui/meson.build

@@ -28,6 +28,7 @@ executable(
     'nmt-page-ip4.c',
     'nmt-page-ip6.c',
     'nmt-page-ip-tunnel.c',
+    'nmt-page-loopback.c',
     'nmt-page-macsec.c',
     'nmt-page-ppp.c',
     'nmt-page-team.c',

src/nmtui/nm-editor-utils.c

@@ -156,6 +156,14 @@ nm_editor_utils_get_connection_type_list(void)
     item->id_format         = _("Veth connection %d");
     g_ptr_array_add(array, item);
 
+    item                    = g_new0(NMEditorConnectionTypeDataReal, 1);
+    item->data.name         = _("Loopback");
+    item->data.setting_type = NM_TYPE_SETTING_LOOPBACK;
+    item->data.device_type  = NM_TYPE_DEVICE_LOOPBACK;
+    item->data.virtual      = TRUE;
+    item->id_format         = _("Loopback connection %d");
+    g_ptr_array_add(array, item);
+
     item                        = g_new0(NMEditorConnectionTypeDataReal, 1);
     item->data.name             = _("Wi-Fi");
     item->data.setting_type     = NM_TYPE_SETTING_WIRELESS;

src/nmtui/nmt-connect-connection-list.c

@@ -95,6 +95,7 @@ static const char *device_sort_order[]   = {"NMDeviceEthernet",
                                             "NMDeviceVeth",
                                             "NMDeviceInfiniband",
                                             "NMDeviceWifi",
+                                            "NMDeviceLoopback",
                                             NM_SETTING_VLAN_SETTING_NAME,
                                             NM_SETTING_VETH_SETTING_NAME,
                                             NM_SETTING_BOND_SETTING_NAME,

src/nmtui/nmt-editor.c

@@ -35,6 +35,7 @@
 #include "nmt-page-ip-tunnel.h"
 #include "nmt-page-ip4.h"
 #include "nmt-page-ip6.h"
+#include "nmt-page-loopback.h"
 #include "nmt-page-macsec.h"
 #include "nmt-page-ppp.h"
 #include "nmt-page-team.h"
@@ -376,6 +377,8 @@ nmt_editor_constructed(GObject *object)
         page = nmt_page_vlan_new(priv->edit_connection, deventry);
     else if (nm_connection_is_type(priv->edit_connection, NM_SETTING_WIRED_SETTING_NAME))
         page = nmt_page_ethernet_new(priv->edit_connection, deventry);
+    else if (nm_connection_is_type(priv->edit_connection, NM_SETTING_LOOPBACK_SETTING_NAME))
+        page = nmt_page_loopback_new(priv->edit_connection, deventry);
     else if (nm_connection_is_type(priv->edit_connection, NM_SETTING_WIRELESS_SETTING_NAME))
         page = nmt_page_wifi_new(priv->edit_connection, deventry);
     else if (nm_connection_is_type(priv->edit_connection, NM_SETTING_IP_TUNNEL_SETTING_NAME))

src/nmtui/nmt-page-loopback.c

@@ -0,0 +1,69 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2025 Red Hat, Inc.
+ */
+/**
+ * SECTION:nmt-page-loopback
+ * @short_description: The editor page for the loopback interface
+ */
+
+#include "libnm-client-aux-extern/nm-default-client.h"
+
+#include <linux/if_ether.h>
+
+#include "nmt-page-loopback.h"
+
+#include "libnm-core-aux-intern/nm-libnm-core-utils.h"
+#include "nmt-device-entry.h"
+#include "nmt-mtu-entry.h"
+
+G_DEFINE_TYPE(NmtPageLoopback, nmt_page_loopback, NMT_TYPE_EDITOR_PAGE_DEVICE)
+
+#define NMT_PAGE_LOOPBACK_GET_PRIVATE(o) \
+    _NM_GET_PRIVATE(self, NmtPageLoopback, NMT_IS_PAGE_LOOPBACK)
+
+static void
+nmt_page_loopback_init(NmtPageLoopback *loopback)
+{}
+
+NmtEditorPage *
+nmt_page_loopback_new(NMConnection *conn, NmtDeviceEntry *deventry)
+{
+    return g_object_new(NMT_TYPE_PAGE_LOOPBACK, "connection", conn, "device-entry", deventry, NULL);
+}
+
+static void
+nmt_page_loopback_constructed(GObject *object)
+{
+    NmtPageLoopback   *loopback = NMT_PAGE_LOOPBACK(object);
+    NmtEditorSection  *section;
+    NmtEditorGrid     *grid;
+    NMSettingLoopback *s_loopback;
+    NmtNewtWidget     *widget;
+    NMConnection      *conn;
+
+    conn       = nmt_editor_page_get_connection(NMT_EDITOR_PAGE(loopback));
+    s_loopback = _nm_connection_ensure_setting(conn, NM_TYPE_SETTING_LOOPBACK);
+
+    section = nmt_editor_section_new(_("LOOPBACK"), NULL, FALSE);
+    grid    = nmt_editor_section_get_body(section);
+
+    widget = nmt_mtu_entry_new();
+    g_object_bind_property(s_loopback,
+                           NM_SETTING_LOOPBACK_MTU,
+                           widget,
+                           "mtu",
+                           G_BINDING_BIDIRECTIONAL | G_BINDING_SYNC_CREATE);
+    nmt_editor_grid_append(grid, _("MTU"), widget, NULL);
+
+    nmt_editor_page_add_section(NMT_EDITOR_PAGE(loopback), section);
+
+    G_OBJECT_CLASS(nmt_page_loopback_parent_class)->constructed(object);
+}
+
+static void
+nmt_page_loopback_class_init(NmtPageLoopbackClass *loopback_class)
+{
+    GObjectClass *object_class = G_OBJECT_CLASS(loopback_class);
+    object_class->constructed  = nmt_page_loopback_constructed;
+}

src/nmtui/nmt-page-loopback.h

@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2025 Red Hat, Inc.
+ */
+
+#ifndef NMT_PAGE_LOOPBACK_H
+#define NMT_PAGE_LOOPBACK_H
+
+#include "nmt-editor-page-device.h"
+
+#define NMT_TYPE_PAGE_LOOPBACK (nmt_page_loopback_get_type())
+#define NMT_PAGE_LOOPBACK(obj) \
+    (_NM_G_TYPE_CHECK_INSTANCE_CAST((obj), NMT_TYPE_PAGE_LOOPBACK, NmtPageLoopback))
+#define NMT_PAGE_LOOPBACK_CLASS(klass) \
+    (G_TYPE_CHECK_CLASS_CAST((klass), NMT_TYPE_PAGE_LOOPBACK, NmtPageLoopbackClass))
+#define NMT_IS_PAGE_LOOPBACK(obj)         (G_TYPE_CHECK_INSTANCE_TYPE((obj), NMT_TYPE_PAGE_LOOPBACK))
+#define NMT_IS_PAGE_LOOPBACK_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE((klass), NMT_TYPE_PAGE_LOOPBACK))
+#define NMT_PAGE_LOOPBACK_GET_CLASS(obj) \
+    (G_TYPE_INSTANCE_GET_CLASS((obj), NMT_TYPE_PAGE_LOOPBACK, NmtPageLoopbackClass))
+
+typedef struct {
+    NmtEditorPageDevice parent;
+} NmtPageLoopback;
+
+typedef struct {
+    NmtEditorPageDeviceClass parent;
+} NmtPageLoopbackClass;
+
+GType nmt_page_loopback_get_type(void);
+
+NmtEditorPage *nmt_page_loopback_new(NMConnection *conn, NmtDeviceEntry *deventry);
+
+#endif /* NMT_PAGE_LOOPBACK_H */