⭐ proof of concept for UDP-over-TCP

.gitignore

@@ -12,3 +12,6 @@
 
 # TLS certs used for QUIC experiments
 *.crt
+
+# Kate editor temp file
+*.kate-swp

Cargo.lock

@@ -2253,6 +2253,14 @@ version = "0.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "56dee185309b50d1f11bfedef0fe6d036842e3fb77413abef29f8f8d1c5d4c1c"
 
+[[package]]
+name = "udp_over_tcp"
+version = "0.1.0"
+dependencies = [
+ "anyhow",
+ "tokio",
+]
+
 [[package]]
 name = "unicase"
 version = "2.6.0"

crates/udp_over_tcp/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "udp_over_tcp"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+anyhow = "1.0.38"
+tokio = { version = "1.8.1", features = ["full"] }

crates/udp_over_tcp/src/client.rs

@@ -0,0 +1,47 @@
+use std::{
+	net::{
+		Ipv4Addr,
+		SocketAddr,
+		SocketAddrV4,
+	},
+	sync::Arc,
+};
+
+use tokio::{
+	net::{
+		TcpSocket,
+		UdpSocket,
+	},
+	spawn,
+};
+
+use crate::loops;
+
+pub async fn main () -> anyhow::Result <()> {
+	let udp_sock = UdpSocket::bind (SocketAddrV4::new (Ipv4Addr::UNSPECIFIED, crate::PORT_1)).await?;
+	udp_sock.connect ((Ipv4Addr::LOCALHOST, crate::PORT_0)).await?;
+	
+	let tcp_sock = TcpSocket::new_v4 ()?;
+	let tcp_conn = tcp_sock.connect (SocketAddr::V4 (SocketAddrV4::new (Ipv4Addr::LOCALHOST, crate::PORT_2))).await?;
+	let (tcp_read, tcp_write) = tcp_conn.into_split ();
+	
+	let tx_task;
+	let rx_task;
+	
+	{
+		let udp_sock = Arc::new (udp_sock);
+		rx_task = spawn (loops::rx (Arc::clone (&udp_sock), tcp_read));
+		tx_task = spawn (loops::tx (Arc::clone (&udp_sock), tcp_write));
+	}
+	
+	tokio::select! {
+		_val = tx_task => {
+			println! ("client_main: tx_task exited, exiting");
+		}
+		_val = rx_task => {
+			println! ("client_main: rx_task exited, exiting");
+		}
+	}
+	
+	Ok (())
+}

crates/udp_over_tcp/src/loops.rs

@@ -0,0 +1,69 @@
+use std::{
+	sync::Arc,
+};
+
+use tokio::{
+	io::{
+		AsyncReadExt,
+		AsyncWriteExt,
+	},
+	net::{
+		UdpSocket,
+		tcp,
+	}
+};
+
+pub async fn rx (
+	udp_sock: Arc <UdpSocket>,
+	mut tcp_read: tcp::OwnedReadHalf,
+) -> anyhow::Result <()> {
+	loop {
+		let mut tag = [0u8, 0, 0, 0];
+		let bytes_read = tcp_read.read (&mut tag).await?;
+		if bytes_read != 4 {
+			anyhow::anyhow! ("loops::rx: Couldn't read 4 bytes for tag");
+		}
+		if tag != [1, 0, 0, 0] {
+			anyhow::anyhow! ("loops::rx: unexpected tag in framing");
+		}
+		
+		let mut length = [0u8, 0, 0, 0];
+		let bytes_read = tcp_read.read (&mut length).await?;
+		if bytes_read != 4 {
+			anyhow::anyhow! ("loops::rx: Couldn't read 4 bytes for tag");
+		}
+		
+		let length = usize::try_from (u32::from_le_bytes (length))?;
+		if length >= 8_192 {
+			anyhow::anyhow! ("loops::rx: Length too big for UDP packets");
+		}
+		
+		let mut buf = vec! [0u8; length];
+		let bytes_read = tcp_read.read_exact (&mut buf).await?;
+		if length != bytes_read {
+			anyhow::anyhow! ("loops::rx: read_exact failed");
+		}
+		buf.truncate (bytes_read);
+		
+		udp_sock.send (&buf).await?;
+	}
+}
+
+pub async fn tx (
+	udp_sock: Arc <UdpSocket>,
+	mut tcp_write: tcp::OwnedWriteHalf,
+) -> anyhow::Result <()> 
+{
+	loop {
+		let mut buf = vec! [0u8; 8_192];
+		let bytes_read = udp_sock.recv (&mut buf).await?;
+		buf.truncate (bytes_read);
+		
+		let tag = [1u8, 0, 0, 0];
+		let length = u32::try_from (bytes_read)?.to_le_bytes ();
+		
+		tcp_write.write_all (&tag).await?;
+		tcp_write.write_all (&length).await?;
+		tcp_write.write_all (&buf).await?;
+	}
+}

crates/udp_over_tcp/src/main.rs

@@ -0,0 +1,54 @@
+/*
+
+To test manually, run this 3 commands:
+
+- Terminal A: `nc -l -u -p 9503`
+- Terminal B: `cargo run -p udp_over_tcp`
+- Terminal C: `nc -p 9500 -u 127.0.0.1 9501`
+
+Terminals A and C should be connected through the UDP-over-TCP connection
+
+*/
+
+use tokio::{
+	runtime,
+	spawn,
+};
+
+mod client;
+mod loops;
+mod server;
+
+// The ephemeral UDP port that the PTTH_QUIC client will bind
+const PORT_0: u16 = 9500;
+
+// The well-known UDP port that the UDP-over-TCP client will bind
+// The PTTH_QUIC client must connect to this instead of the real relay address
+const PORT_1: u16 = 9501;
+
+// The well-known TCP port that the UDP-over-TCP server will bind
+const PORT_2: u16 = 9502;
+
+// The well-known UDP port that the PTTH_QUIC relay will bind
+const PORT_3: u16 = 9503;
+
+fn main () -> anyhow::Result <()> {
+	let rt = runtime::Runtime::new ()?;
+	
+	rt.block_on (async_main ())?;
+	
+	Ok (())
+}
+
+async fn async_main () -> anyhow::Result <()> {
+	tokio::select! {
+		_val = spawn (client::main ()) => {
+			println! ("Client exited, exiting");
+		},
+		_val = spawn (server::main ()) => {
+			println! ("Server exited, exiting");
+		},
+	}
+	
+	Ok (())
+}

crates/udp_over_tcp/src/server.rs

@@ -0,0 +1,55 @@
+use std::{
+	net::{
+		Ipv4Addr,
+		SocketAddrV4,
+	},
+	sync::Arc,
+};
+
+use tokio::{
+	net::{
+		TcpListener,
+		TcpStream,
+		UdpSocket,
+	},
+	spawn,
+};
+
+use crate::loops;
+
+pub async fn main () -> anyhow::Result <()> {
+	let tcp_listener = TcpListener::bind ((Ipv4Addr::UNSPECIFIED, crate::PORT_2)).await?;
+	
+	loop { 
+		let (conn, _peer_addr) = tcp_listener.accept ().await?;
+		
+		spawn (handle_connection (conn));
+	}
+}
+
+async fn handle_connection (conn: TcpStream) -> anyhow::Result <()> {
+	let udp_sock = UdpSocket::bind (SocketAddrV4::new (Ipv4Addr::UNSPECIFIED, 0)).await?;
+	udp_sock.connect ((Ipv4Addr::LOCALHOST, crate::PORT_3)).await?;
+	
+	let (tcp_read, tcp_write) = conn.into_split ();
+	
+	let rx_task;
+	let tx_task;
+	
+	{
+		let udp_sock = Arc::new (udp_sock);
+		rx_task = spawn (loops::rx (Arc::clone (&udp_sock), tcp_read));
+		tx_task = spawn (loops::tx (Arc::clone (&udp_sock), tcp_write));
+	}
+	
+	tokio::select! {
+		_val = tx_task => {
+			println! ("server_handle_connection: tx_task exited, exiting");
+		}
+		_val = rx_task => {
+			println! ("server_handle_connection: rx_task exited, exiting");
+		}
+	}
+	
+	Ok (())
+}