Networking with curl

Networking with curl#

There are several options for providing network functionality on L4Re.

Basically two variants exists with respect to where a driver for a network device can be placed.

One way is using an existing system, such as Linux, running it in a VM and using Virtio-net to expose networking to outside of the VM. Using an existing system, for example, Linux, gives further plenty of networking features, such as firewalls and routing capabilities, and also plenty of drivers for many, if not all, devices. A downside is that a whole operating system and VM is required for this option, even if it can be specifically customized for purpose of handling networking only.

A driver running in an L4Re application. This driver can either be ported from some other environment or operating system, or written from scratch. Eventually such a driver needs to interact with with the software components that use it. Use could be in-process, i.e. an application has a specific network driver built-in and thus directly talks to the network device. Or the driver offers its services to other components in the system through a shared memory interface. For network, Virtio-net is a common and established interface.

In L4Re, there’s a virtual network switch that also has support to integrate device drivers. Thus the virtual network switch can be seen as a network device driver with multiple Virtio-net interfaces, or a virtual network switch where one port is not Virtio but a physical network device.

Running the network switch with the ixl drivers#

The virtual network switch has support for the ixl network drivers. Please refer to the ixl drivers for details, such as supported network devices.

The application using the network is the famous curl. To work with the driver via virtio-net, it needs a networking stack. We use lwIP, which has also been brought to L4Re with appropriate connectors for virtio-net.

Building ixl and virtio-net-switch#

The switch has a compile-time configuration that needs to be enabled such that the functionality for network device drivers is included. Please have the ixl package cloned to l4/pkg/ixl and the CONFIG_VNS_IXL enabled option in the L4Re configuration.

Building curl#

Please have curl, zstd, and LwIP cloned to l4/pkg/curl, l4/pkg/zstd and l4/pkg/lwip respectively, next to the standard L4Re packages.

Compile everything.

Starting the network switch and curl#

The following ned script starts the network switch together with curl, downloading a web page.

 1-- vim:ft=lua
 2
 3local L4 = require("L4");
 4local ld = L4.default_loader;
 5
 6local vbus_eth  = ld:new_channel();
 7
 8ld:start(
 9    {
10        caps = {
11            sigma0   = L4.Env.sigma0;
12            icu      = L4.Env.icu;
13            iommu    = L4.Env.iommu;
14            ethdevs  = vbus_eth:svr();
15        },
16    },
17    "rom/io rom/ixl.vbus"
18);
19
20local vswitch = ld:new_channel();
21
22ld:start(
23    { caps = { vbus = vbus_eth, svr = vswitch:svr(); }, },
24    "rom/l4vio_switch");
25
26ld:start(
27   { caps = { virtnet = vswitch:create(0), etc = L4.Env.rom }, },
28   "rom/curl -s http://ftp.de.debian.org/debian/",
29   { IFCONFIG_IP4_vn0="dhcp" });

Please find a possible ixl.vbus here.

A resolv.conf file also needs to be supplied with the following content:

nameserver 10.0.2.3
Contents