VpnHood.Net.VpnAdapters.Abstractions

The contract and the base class of VpnHood's VPN adapters: virtual network interfaces (TUN) that the host's traffic is routed into, whose IP packets a VPN reads and writes. One package per platform builds on it: VpnHood.Net.VpnAdapters.WinTun, .WinDivert, .WindowsVpnPlugin, .LinuxTun, .AndroidTun and .IosTun.

dotnet add package VpnHood.Net.VpnAdapters.Abstractions

How it works

• IVpnAdapter is the contract: start with VpnAdapterOptions (addresses, DNS servers, routes, NAT, app filter), read packets through PacketReceived, write them with SendPacketQueued, stop.
• TunVpnAdapter does the work every platform shares: the order of a start's steps, the stop, the reader and the writer with their retries, stopping after repeated I/O errors, AutoRestart, and following the host when its network changes. A platform's adapter supplies only its steps: add, open, close and remove the interface, set its addresses, routes and DNS servers, read and write one packet.
• ProtectSocket keeps a socket, such as the one to the VPN server, out of the tunnel.
• NullVpnAdapter has no interface: it runs a VPN without rights, for tests.

Quick start

The example below runs as a test in CI (VpnAdaptersReadmeExampleTest.cs). Its namespaces are System.Net, VpnHood.Net.VpnAdapters.Abstractions, VpnHood.Net.Packets, VpnHood.Net.Packets.Extensions and VpnHood.Net.Toolkit.Net.

// in an app, a platform's adapter: WinTunVpnAdapter, LinuxTunVpnAdapter, AndroidVpnAdapter...
using var adapter = new NullVpnAdapter(blocking: false);

// what the host routes into the tunnel arrives here, on the adapter's reader task
adapter.PacketReceived += (_, ipPacket) => {
    Console.WriteLine($"From the host: {ipPacket}");
    ipPacket.Dispose(); // the handler owns each packet: forward it or dispose it
};

await adapter.Start(new VpnAdapterOptions {
    SessionName = "My VPN",
    VirtualIpNetworkV4 = IpNetwork.Parse("10.255.0.2/24"),
    DnsServers = [IPAddress.Parse("10.255.0.1")],
    IncludeNetworks = IpNetwork.All // every address of the IP versions the interface carries: IPv4 here
}, CancellationToken.None);

// what the VPN sends the host is queued; the adapter writes it on its own loop and disposes it
var packet = PacketBuilder.BuildUdp(
    new IPEndPoint(IPAddress.Parse("10.255.0.1"), 53),
    new IPEndPoint(IPAddress.Parse("10.255.0.2"), 5353),
    "answer"u8);
packet.UpdateAllChecksums();
adapter.SendPacketQueued(packet);

adapter.Stop(); // removes the interface, its routes and its DNS servers

License

LGPL-2.1-only. See the VpnHood repository.