L4Re – L4 Runtime Environment
l4vio_net_p2p, a virtual network point-to-point link

The virtual network point-to-point server (p2p) connects two clients with a virtual network connection.

It uses virtio as the transport mechanism. Each virtual network p2p endpoint implements the device-side of a virtio network device. Each client can access its endpoint using the driver-side semantics of a virtio network device.

Building and Configuration

The virtual network p2p server can be built using the L4Re build system by placing this project into the pkg directory.

Starting the service

The virtual network p2p server can be started with Lua like this:

local p2p = L4.default_loader:new_channel();
  caps = {
    svr = p2p:svr(),
"rom/l4vio_net_p2p [<options>]");

First an IPC gate (p2p) is created which is used between the virtual network p2p server and a client to create new virtual ports. The server-side is assigned to the mandatory svr capability of the virtual network p2p server. See the section below on how to create a new virtual port and connect a client to it.


The following command line options are supported:

  • -p <num_usec>, --poll <num_usec>

    Enable polling mode and set the poll interval. IRQ notification is disabled for queues while in polling mode. Must be a positive integer specified in microseconds.

  • -s <num>, --size <num>

    Set the maximum queue size for the device-side virtio queues. Must be a power of 2 in the range of 1 to 32768 inclusive.

Connecting a client

Prior to connecting a client to a virtual network p2p server port it has to be created using the following Lua function. It has to be called on the client side of the IPC gate capability whose server side is bound to the virtual network p2p server.

The "key=value" pairs passed to create() can be omitted and their order is not important.

create(obj_type, ["ds-max=<max>" , "mac-addr=<mac_address>"])
  • obj_type

    The type of object that should be created by the server. The type must be a positive integer. Currently the following objects are supported:

    • 0: Virtual p2p port
  • "ds-max=<max>"

    Specifies the upper limit of the number of dataspaces the client is allowed to register with the server for virtio DMA. Must be in the range of 1 to 80 inclusive. The default value is 2.

  • "mac-addr=<mac_address>"

    Specify the MAC address of the endpoint where <mac_address> is of the form X:XX:Xx:x:xx:xX.

If the create() call is successful a new capability which references a virtual network p2p server port is returned. A client uses this capability to talk to the virtual network p2p server using the virtio network protocol.

A couple of examples on how to create ports with different properties are listed below.

-- two normal ports with at most 4 data spaces
net0 = p2p:create(0, "ds-max=4")
net1 = p2p:create(0, "ds-max=4")
-- normal port with 4 data spaces and MAC address
net0 = p2p:create(0, "ds-max=4", "mac-addr=11:22:33:44:55:66")