Simple Connection and Packet Router in Rust

This is a simple connection/port-based network router implemented in Rust using Tokio and async/await.

For UDP it currently implement simple UDP packet forwarding. It can listen on one port and forward packets received to one or more other addresses.

For TCP it currently implement simple round-robin selection of incoming connections. It listens on one port and for every connection request arriving, it will establish an outgoing connection to a list of other addresses in a round-robin fashion. Packets will then simply be forwarded when they arrive in both directions independently of each others.

Routes right now have to be set up statically, but the intention is to implement a good API for dynamically setting up and changing routes.

How to build

cd network-router-rs
cargo build

How to run

Edit the config.json file.

Start the router.

target/debug/network-router --config-file=config.json

You can get a list of command-line options using --help.

Configuration file format

The configuration file is in JSON and is split into separate sections with one section for each forwarding configuration:

{
    "sections": [
	{
	    "protocol":"udp",
	    "mode":"broadcast",
	    "source": "127.0.0.1:8080",
	    "destinations": ["127.0.0.1:8081"]
	}
    ]
}

Each section can contain four different attributes:

protocol is the protocol that the section should use. It can be either udp or tcp.
mode can be either broadcast or round-robin and the default is broadcast for UDP and round-robin for TCP.
- In broadcast mode, each packet will be sent to all destinations, which only make sense for UDP.
- In round-robin mode, each packet will be sent to or connection established with one target at a time in a round-robin fashion.
source is a source addresses that the router should listen on.
destinations is a list of destination addresses that the router should send packets or establish connections with.

Caveat

For the TCP connection, shutdown does not currently work since the "shutdown" function for a TcpStream does not do anything at all (!). See Issue #852 in (tokio-rs/tokio)[https://github.com/tokio-rs/tokio].

A simple (but ugly) way around this is to apply the following patch to tokio repository:

diff --git a/tokio-tcp/src/stream.rs b/tokio-tcp/src/stream.rs
index 1a00679..ea0205d 100644
--- a/tokio-tcp/src/stream.rs
+++ b/tokio-tcp/src/stream.rs
@@ -844,6 +844,7 @@ impl<'a> AsyncRead for &'a TcpStream {
 
 impl<'a> AsyncWrite for &'a TcpStream {
     fn shutdown(&mut self) -> Poll<(), io::Error> {
+        self.io.get_ref().shutdown(Shutdown::Write)?;
         Ok(().into())
     }

Contribution