netsim
is a crate for simulating networks for the sake of testing network-oriented Rust
code. You can use it to run Rust functions in network-isolated containers, and assemble
virtual networks for these functions to communicate over.
Network namespaces are a linux feature which can provide a thread or process with its own view
of the system's network interfaces and routing table. This crate's spawn
module provides the
new_namespace
function for spawning threads into their own network namespaces. In this
demonstration we list the visible network interfaces using the
get_if_addrs
crate.
extern crate netsim;
extern crate get_if_addrs;
extern crate tokio_core;
use netsim::spawn;
use tokio_core::reactor::Core;
use get_if_addrs::get_if_addrs;
// First, check that there is more than one network interface. This will generally be true
// since there will at least be the loopback interface.
let interfaces = get_if_addrs().unwrap();
assert!(interfaces.len() > 0);
// Now check how many network interfaces we can see inside a fresh network namespace. There
// should be zero.
let spawn_complete = spawn::new_namespace(|| {
get_if_addrs().unwrap()
});
let mut core = Core::new().unwrap();
let interfaces = core.run(spawn_complete).unwrap();
assert!(interfaces.is_empty());
This demonstrates how to launch a thread - perhaps running an automated test - into a sandboxed environment. However an environment with no network interfaces is pretty useless...
We can create virtual IP and Ethernet interfaces using the types in the iface
module. For
example, IpIface
lets you create a new IP (TUN) interface and implements futures::{Stream, Sink}
so that you can read/write raw packets to it.
extern crate netsim;
extern crate tokio_core;
extern crate futures;
use std::net::Ipv4Addr;
use tokio_core::reactor::Core;
use futures::{Future, Stream};
use netsim::iface::IpIfaceBuilder;
use netsim::spawn;
let mut core = Core::new().unwrap();
let handle = core.handle();
// Create a network interface named "netsim"
// Note: This will likely fail with "permission denied" unless we run it in a fresh network
// environment
let iface = {
IpIfaceBuilder::new()
.name("netsim")
.ipv4_addr(Ipv4Addr::new(192, 168, 0, 24), 24)
.build(&handle)
.unwrap()
};
// Read the first `Ipv4Packet` sent from the interface.
let packet = core.run({
iface
.into_future()
.map_err(|(e, _)| e)
.map(|(packet_opt, _)| packet_opt.unwrap())
}).unwrap();
However, for simply testing network code, you don't need to create interfaces manually like this.
Rather than performing the above two steps individually, you can use the spawn::ipv4_tree
function along with the node
module to set up a namespace with an IPv4 interface for you.
extern crate netsim;
extern crate tokio_core;
extern crate futures;
use std::net::UdpSocket;
use tokio_core::reactor::Core;
use futures::{Future, Stream};
use netsim::{spawn, node, Network, Ipv4Range};
use netsim::wire::Ipv4Payload;
// Create an event loop and a network to bind devices to.
let mut core = Core::new().unwrap();
let network = Network::new(&core.handle());
let handle = network.handle();
// Spawn a network with a single node - a machine with an IPv4 interface in the 10.0.0.0/8
// range, running the given callback.
let (spawn_complete, ipv4_plug) = spawn::ipv4_tree(
&handle,
Ipv4Range::local_subnet_10(),
node::ipv4::machine(|ipv4_addr| {
// Send a packet out the interface
let socket = UdpSocket::bind("0.0.0.0:0").unwrap();
socket.send_to(b"hello world", "10.1.2.3:4567").unwrap();
}),
);
let (packet_tx, packet_rx) = ipv4_plug.split();
// Inspect the packet sent out the interface.
core.run({
packet_rx
.into_future()
.map(|(packet_opt, _)| {
let packet = packet_opt.unwrap();
match packet.payload() {
Ipv4Payload::Udp(udp) => {
assert_eq!(&udp.payload()[..], &b"hello world"[..]);
},
_ => panic!("unexpected payload"),
}
})
}).unwrap()
Using the spawn
and node
modules you can set up a bunch of nodes connected over a virtual
network.
extern crate tokio_core;
extern crate future_utils;
extern crate netsim;
use std::net::UdpSocket;
use tokio_core::reactor::Core;
use netsim::{spawn, node, Network, Ipv4Range};
// Create an event loop and a network to bind devices to.
let mut core = Core::new().unwrap();
let network = Network::new(&core.handle());
let handle = network.handle();
let (tx, rx) = std::sync::mpsc::channel();
// Create a machine which will receive a UDP packet and return its contents
let receiver_node = node::ipv4::machine(move |ipv4_addr| {
let socket = UdpSocket::bind(("0.0.0.0", 1234)).unwrap();
/// Tell the sending node our IP address
tx.send(ipv4_addr).unwrap();
let mut buffer = [0; 1024];
let (n, _sender_addr) = socket.recv_from(&mut buffer).unwrap();
buffer[..n].to_owned()
});
// Create the machine which will send the UDP packet
let sender_node = node::ipv4::machine(move |_ipv4_addr| {
let receiver_ip = rx.recv().unwrap();
let socket = UdpSocket::bind("0.0.0.0:0").unwrap();
socket.send_to(b"hello world", (receiver_ip, 1234)).unwrap();
});
// Connect the sending and receiving nodes via a router
let router_node = node::ipv4::router((receiver_node, sender_node));
// Run the network with the router as the top-most node. `_plug` could be used send/receive
// packets from/to outside the network
let (spawn_complete, _plug) = spawn::ipv4_tree(&handle, Ipv4Range::global(), router_node);
// Drive the network on the event loop and get the data returned by the receiving node.
let (received, ()) = core.run(spawn_complete).unwrap();
assert_eq!(&received[..], b"hello world");
It's possible to set up more complicated (non-hierarchical) network topologies, ethernet
networks, namespaces with multiple interfaces etc. by directly using the primitives in the
device
module. Have an explore of the API, and if anything needs clarification or could be
better designed then let us know on the bug tracker :)
netsim
only runs on Linux as it makes use of the Linux namespaces APIs.
netsim
depends on the POSIX capabilities library, usually called libcap-dev
or libcap-devel
on most distros.
netsim has it's own unit/integration tests. There are different ways to run these tests depending on the environment you're in.
If you're on a Linux host machine, you can just use cargo test
like normal:
$ cargo test
If you're inside a Linux container, say running tests on travis CI, the Linux
namespace APIs probably won't be available. In this case you need to disable
the linux_host
feature of this crate:
$ cargo test --no-default-features
This library is dual-licensed under the Modified BSD (LICENSE-BSD https://opensource.org/licenses/BSD-3-Clause) or the MIT license (LICENSE-MIT https://opensource.org/licenses/MIT) at your option.