Tapctl Network Interface Management Utility

Introduction

The Tapctl or tapctl.exe is a command line utility introduced to manage TAP network interfaces on Windows. It was developed to replace the tapinstall.exe utility.

User Manual

The Tapctl utility requires elevation. Please, run it from an elevated command prompt (Run as Administrator).

Creating a TAP/TUN network interface

Usage:

tapctl create [--name <desired interface name>]

A new virtual network interface is created.

When the --name parameter is omitted, Windows selects a name automatically (e.g. "Ethernet 2").

When the --name parameter is specified, the utility will rename the newly created interface to the name given. Should the interface with the given name already exist, an error is returned. If the name contains spaces, enclose it in quotes.

Upon successful creation, the newly created interface's GUID is output to stdout.

Notes:

1. The name specified using --name parameter can also be specified as OpenVPN's --dev-node option.
2. Tapctl does not install or update TAP-Windows driver. It assumes the driver is already installed. The TAP-Windows NDIS 6 driver is installed as a part of OpenVPN MSI setup or may be installed manually using the INF file.

Listing installed network interfaces

Usage:

tapctl list

This command prints all network interfaces to stdout. The list will contain interface GUIDs and names. 3rd party interfaces and system internal interfaces will also be included on the list.

Removing a network interface

Usage:

tapctl delete <interface GUID | interface name>

Deletes the specified network interface. Please note, that the Tapctl utility does not check the interface type and as such can be used to remove any network interface from your system. Use with care.

Developer Notes

The Tapctl utility was developed to compile using Microsoft Visual Studio 2017 and later upgraded to support building as a part of the OpenVPN-build system.

Source files

basic.h

Basic macro declarations

error.c and error.h

OpenVPN compatible error reporting API. Though the Tapctl utility does not rely on openvpn.exe's source code, it borrows the run-time information output scheme from it. This tries to keep the source code style and best practices as close to OpenVPN as possible.

main.c

Main utility logic. It also includes implementation of msg() function to output any messages to stdout and stderr.

tap.c and tap.h

Windows network interface management functions. All definitions in tap.h include description and usage instructions in a Doxygen form.

Some of these source files are reused by the openvpnmsica DLL.