Go OpenVPN Management Protocol Client

This repository contains a Go package that implements a client for the OpenVPN management interface.

This can be used to monitor and control an OpenVPN process running with its management port enabled.

Currently only a subset of the protocol is supported, primarily focused on monitoring status changes and cleanly shutting down or restarting connections. Patches that add additional functionality in a manner consistent with the existing features will be gratefully accepted.

Installation

go get github.com/apparentlymart/go-openvpn-mgmt/openvpn

Usage

First, we can import the package:

import (
    "github.com/apparentlymart/go-openvpn-mgmt/openvpn"
)

The default imported package name is openvpn.

OpenVPN's management interface can be used in two different modes: either OpenVPN opens a TCP listen port and the management client connects to it, or the management client opens a TCP listen port and OpenVPN connects to it.

The default configuration is for the OpenVPN process to act as the TCP server. Launch OpenVPN with the argument --management <listen-addr> <port> to activate this mode, and then connect to it by passing the same address and port to openvpn.Dial. For example:

eventCh := make(chan openvpn.Event, 10)
client, err := openvpn.Dial("127.0.0.1:6061", eventCh);
if err != nil {
    panic(err)
}

// "client" is now connected to the OpenVPN process and can send
// it commands. "eventCh" can be read to get asynchronous events from
// OpenVPN.

The alternative configuration, with OpenVPN acting as the TCP client, can be useful for processes that manage a number of separate OpenVPN instances running as child processes, since they can all be commanded to connect to the same listen port on the parent management process. Launch OpenVPN with the arguments --management-client --management <remote-addr> <port> to activate this mode, after creating a listen server using openvpn.ListenAndServe. For example:

func main() {
    log.Fatal(openvpn.ListenAndServe(
        "127.0.0.1:6061",
        openvpn.IncomingConnHandlerFunc(newConnection),
    ))
}

func newConnection(conn openvpn.IncomingConn) {
    eventCh := make(chan openvpn.Event, 10)
    client := conn.Open(eventCh)

    // "client" is now connected to the OpenVPN process and can send
    // it commands. "eventCh" can be read to get asynchronous events from
    // OpenVPN.
}

For more usage information on both modes, see the reference documentation.

License

Copyright (c) 2016 Martin Atkins

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.