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refactor(iroh-net): use tokio-util::codec for derp protocol implement…
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…ation (#1386)

We have been having issues multiple times with the buffer management,
this cleans up things and should make them more reliable. The core
change is to use `tokio_util::codec` to implement the derp protocol.
Additionally there are a couple smaller fixes in the derper code and
tests, for issues that where discovered while doing this.

Fixes #1384, #1381, #1247

---------

Co-authored-by: Ruediger Klaehn <rklaehn@protonmail.com>
Co-authored-by: Kasey <klhuizinga@gmail.com>
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@dignifiedquire @rklaehn @ramfox
3 people committed Aug 23, 2023
1 parent 03339f1 commit fe98c8d
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2 changes: 1 addition & 1 deletion iroh-net/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -52,7 +52,7 @@ tracing = "0.1"
trust-dns-resolver = "0.22.0"
time = "0.3.20"
tokio = { version = "1", features = ["io-util", "sync", "rt", "net", "fs", "io-std", "signal", "process"] }
tokio-util = { version = "0.7", features = ["io-util", "io"] }
tokio-util = { version = "0.7", features = ["io-util", "io", "codec"] }
tokio-rustls = { version = "0.24" }
tokio-rustls-acme = { version = "0.2" }
tokio-stream = { version = "0.1", features = ["sync"]}
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357 changes: 2 additions & 355 deletions iroh-net/src/derp.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,372 +12,19 @@
pub(crate) mod client;
pub(crate) mod client_conn;
pub(crate) mod clients;
mod codec;
pub mod http;
mod map;
mod metrics;
pub(crate) mod server;
pub(crate) mod types;

pub use self::client::{Client as DerpClient, ReceivedMessage};
pub use self::codec::MAX_PACKET_SIZE;
pub use self::http::Client as HttpClient;
pub use self::map::{DerpMap, DerpNode, DerpRegion, UseIpv4, UseIpv6};
pub use self::metrics::Metrics;
pub use self::server::{
ClientConnHandler, MaybeTlsStream as MaybeTlsStreamServer, PacketForwarderHandler, Server,
};
pub use self::types::{MeshKey, PacketForwarder};

use std::time::Duration;

use anyhow::{ensure, Context, Result};
use bytes::BytesMut;
use tokio::io::{AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
use tracing::debug;

use crate::key::{PublicKey, SecretKey, SharedSecret, PUBLIC_KEY_LENGTH};
use types::ClientInfo;

/// The maximum size of a packet sent over DERP.
/// (This only includes the data bytes visible to magicsock, not
/// including its on-wire framing overhead)
pub const MAX_PACKET_SIZE: usize = 64 * 1024;

const MAX_FRAME_SIZE: usize = 1024 * 1024;

/// The DERP magic number, sent in the FrameType::ServerKey frame
/// upon initial connection
///
/// 8 bytes: 0x44 45 52 50 f0 9f 94 91
const MAGIC: &str = "DERP🔑";

const KEEP_ALIVE: Duration = Duration::from_secs(60);
// TODO: what should this be?
const SERVER_CHANNEL_SIZE: usize = 1024 * 100;
/// The number of packets buffered for sending per client
const PER_CLIENT_SEND_QUEUE_DEPTH: usize = 512; //32;

/// ProtocolVersion is bumped whenever there's a wire-incompatiable change.
/// - version 1 (zero on wire): consistent box headers, in use by employee dev nodes a bit
/// - version 2: received packets have src addrs in FrameType::RecvPacket at beginning
const PROTOCOL_VERSION: usize = 2;

///
/// Protocol flow:
///
/// Login:
/// * client connects
/// * server sends FrameType::ServerKey
/// * client sends FrameType::ClientInfo
/// * server sends FrameType::ServerInfo
///
/// Steady state:
/// * server occasionally sends FrameType::KeepAlive (or FrameType::Ping)
/// * client responds to any FrameType::Ping with a FrameType::Pong
/// * clients sends FrameType::SendPacket
/// * server then sends FrameType::RecvPacket to recipient
///

const PREFERRED: u8 = 1u8;
/// indicates this is NOT the client's home node
const NOT_PREFERRED: u8 = 0u8;

/// The one byte frame type at the beginning of the frame
/// header. The second field is a big-endian u32 describing the
/// length of the remaining frame (not including the initial 5 bytes)
#[derive(Debug, PartialEq, Eq)]
#[repr(u8)]
enum FrameType {
/// 8B magic + 32B public key + (0+ bytes future use)
ServerKey = 1,
/// 32b pub key + 24B nonce + chachabox(bytes)
ClientInfo = 2,
/// 24B nonce + chachabox(bytes)
ServerInfo = 3,
/// 32B dest pub key + packet bytes
SendPacket = 4,
/// v0/1 packet bytes, v2: 32B src pub key + packet bytes
RecvPacket = 5,
/// no payload, no-op (to be replaced with ping/pong)
KeepAlive = 6,
/// 1 byte payload: 0x01 or 0x00 for whether this is client's home node
NotePreferred = 7,
/// Sent from server to client to signal that a previous sender is no longer connected.
///
/// That is, if A sent to B, and then if A disconnects, the server sends `FrameType::PeerGone`
/// to B so B can forget that a reverse path exists on that connection to get back to A
///
/// 32B pub key of peer that's gone
PeerGone = 8,
/// Like [`FrameType::PeerGone`], but for other members of the DERP region
/// when they're meshed up together
///
/// 32B pub key of peer that's connected
PeerPresent = 9,
/// How one DERP node in a regional mesh subscribes to the others in the region.
///
/// There's no payload. If the sender doesn't have permission, the connection
/// is closed. Otherwise, the client is initially flooded with
/// [`FrameType::PeerPresent`] for all connected nodes, and then a stream of
/// [`FrameType::PeerPresent`] & [`FrameType::PeerGone`] has peers connect and disconnect.
WatchConns = 10,
/// A priviledged frame type (requires the mesh key for now) that closes
/// the provided peer's connection. (To be used for cluster load balancing
/// purposes, when clients end up on a non-ideal node)
///
/// 32B pub key of peer close.
ClosePeer = 11,
/// 8 byte ping payload, to be echoed back in FrameType::Pong
Ping = 12,
/// 8 byte payload, the contents of ping being replied to
Pong = 13,
/// Sent from server to client to tell the client if their connection is
/// unhealthy somehow. Currently the only unhealthy state is whether the
/// connection is detected as a duplicate.
/// The entire frame body is the text of the error message. An empty message
/// clears the error state.
Health = 14,

/// Sent from server to client for the server to declare that it's restarting.
/// Payload is two big endian u32 durations in milliseconds: when to reconnect,
/// and how long to try total.
///
/// Handled on the `[derp::Client]`, but currently never sent on the `[derp::Server]`
Restarting = 15,
/// 32B src pub key + 32B dst pub key + packet bytes
ForwardPacket = 16,
Unknown = 255,
}

impl std::fmt::Display for FrameType {
fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
write!(f, "{self:?}")
}
}

impl From<u8> for FrameType {
fn from(value: u8) -> Self {
match value {
1 => FrameType::ServerKey,
2 => FrameType::ClientInfo,
3 => FrameType::ServerInfo,
4 => FrameType::SendPacket,
5 => FrameType::RecvPacket,
6 => FrameType::KeepAlive,
7 => FrameType::NotePreferred,
8 => FrameType::PeerGone,
9 => FrameType::PeerPresent,
10 => FrameType::WatchConns,
11 => FrameType::ClosePeer,
12 => FrameType::Ping,
13 => FrameType::Pong,
14 => FrameType::Health,
15 => FrameType::Restarting,
16 => FrameType::ForwardPacket,
_ => FrameType::Unknown,
}
}
}

impl From<FrameType> for u8 {
fn from(value: FrameType) -> Self {
value as u8
}
}

async fn read_frame_header(mut reader: impl AsyncRead + Unpin) -> Result<(FrameType, usize)> {
let frame_type = reader.read_u8().await?;
let frame_len = reader.read_u32().await?;
Ok((frame_type.into(), frame_len.try_into()?))
}

/// AsyncReads a frame header and then reads a `frame_len` of bytes into `buf`.
/// It resizes the `buf` to the expected `frame_len`.
///
/// If the frame header length is greater than `max_size`, `read_frame` returns
/// an error after reading the frame header.
///
/// Also errors if we receive EOF before the end of the expected length of the frame.
async fn read_frame(
mut reader: impl AsyncRead + Unpin,
max_size: usize,
buf: &mut BytesMut,
) -> Result<(FrameType, usize)> {
let (frame_type, frame_len) = read_frame_header(&mut reader)
.await
.context("frame header")?;
debug!("read frame header: {:?} - {:?}", frame_type, frame_len);
ensure!(
frame_len < max_size,
"frame header size {frame_len} exceeds reader limit of {max_size}"
);
buf.resize(frame_len, 0u8);
reader.read_exact(buf).await.context("read exact")?;
Ok((frame_type, frame_len))
}

async fn read_frame_timeout(
mut reader: impl AsyncRead + Unpin,
max_size: usize,
buf: &mut BytesMut,
timeout: Option<Duration>,
) -> Result<(FrameType, usize)> {
if let Some(duration) = timeout {
let (frame_type, frame_len) =
tokio::time::timeout(duration, read_frame(&mut reader, max_size, buf))
.await
.context("timeout")??;
Ok((frame_type, frame_len))
} else {
read_frame(&mut reader, max_size, buf).await
}
}

async fn write_frame_header(
mut writer: impl AsyncWrite + Unpin,
frame_type: FrameType,
frame_len: usize,
) -> Result<()> {
let frame_len = u32::try_from(frame_len)?;
writer.write_u8(frame_type.into()).await?;
writer.write_u32(frame_len).await?;
Ok(())
}

/// AsyncWrites a complete frame. Does not flush.
async fn write_frame<'a>(
mut writer: impl AsyncWrite + Unpin,
frame_type: FrameType,
bytes: &[&[u8]],
) -> Result<()> {
let bytes_len: usize = bytes.iter().map(|b| b.len()).sum();
ensure!(
bytes_len <= MAX_FRAME_SIZE,
"unreasonably large frame write"
);
write_frame_header(&mut writer, frame_type, bytes_len).await?;
for b in bytes {
writer.write_all(b).await?;
}
Ok(())
}

/// AsyncWrites a complete frame, errors if it is unable to write within the given `timeout`.
/// Ignores the timeout if `timeout.is_zero()`
///
/// Does not flush.
async fn write_frame_timeout(
writer: impl AsyncWrite + Unpin,
frame_type: FrameType,
bytes: &[&[u8]],
timeout: Option<Duration>,
) -> Result<()> {
if let Some(duration) = timeout {
tokio::time::timeout(duration, write_frame(writer, frame_type, bytes)).await??;
Ok(())
} else {
write_frame(writer, frame_type, bytes).await
}
}

/// Writes a `FrameType::ClientInfo`, including the client's [`PublicKey`],
/// and the client's [`ClientInfo`], sealed using the server's [`PublicKey`].
///
/// Flushes after writing.
pub(crate) async fn send_client_key<W: AsyncWrite + Unpin>(
mut writer: W,
shared_secret: &SharedSecret,
client_public_key: &PublicKey,
client_info: &ClientInfo,
) -> Result<()> {
let mut msg = postcard::to_stdvec(client_info)?;
shared_secret.seal(&mut msg);
write_frame(
&mut writer,
FrameType::ClientInfo,
&[client_public_key.as_bytes(), &msg],
)
.await?;
writer.flush().await?;
Ok(())
}

/// Reads the `FrameType::ClientInfo` frame from the client (its proof of identity)
/// upon it's initial connection.
async fn recv_client_key<R: AsyncRead + Unpin>(
secret_key: SecretKey,
mut reader: R,
) -> Result<(PublicKey, ClientInfo, SharedSecret)> {
let mut buf = BytesMut::new();
// the client is untrusted at this point, limit the input size even smaller than our usual
// maximum frame size, and give a timeout
let (frame_type, _) = read_frame_timeout(
&mut reader,
256 * 1024,
&mut buf,
Some(Duration::from_secs(10)),
)
.await
.context("read frame")?;
ensure!(
frame_type == FrameType::ClientInfo,
"expected FrameType::ClientInfo frame got {frame_type}"
);
let key = PublicKey::try_from(&buf[..PUBLIC_KEY_LENGTH]).context("public key")?;
let mut msg = buf[PUBLIC_KEY_LENGTH..].to_vec();
let shared_secret = secret_key.shared(&key);
shared_secret.open(&mut msg).context("shared secret")?;
let info: ClientInfo = postcard::from_bytes(&msg).context("deserialization")?;
Ok((key, info, shared_secret))
}

#[cfg(test)]
mod tests {
use super::*;

#[tokio::test]
async fn test_basic_read_write() -> Result<()> {
let (mut reader, mut writer) = tokio::io::duplex(1024);

write_frame_header(&mut writer, FrameType::PeerGone, 301).await?;
let (frame_type, frame_len) = read_frame_header(&mut reader).await?;
assert_eq!(frame_type, FrameType::PeerGone);
assert_eq!(frame_len, 301);

let expect_buf = b"hello world!";
write_frame(&mut writer, FrameType::Health, &[expect_buf]).await?;
writer.flush().await?;
println!("{:?}", reader);
let mut got_buf = BytesMut::new();
let (frame_type, frame_len) = read_frame(&mut reader, 1024, &mut got_buf).await?;
assert_eq!(FrameType::Health, frame_type);
assert_eq!(expect_buf.len(), frame_len);
assert_eq!(expect_buf.as_slice(), &got_buf);
Ok(())
}

#[tokio::test]
async fn test_send_recv_client_key() -> Result<()> {
let (mut reader, mut writer) = tokio::io::duplex(1024);
let server_key = SecretKey::generate();
let client_key = SecretKey::generate();
let client_info = ClientInfo {
version: PROTOCOL_VERSION,
mesh_key: Some([1u8; 32]),
can_ack_pings: true,
is_prober: true,
};
println!("client_key pub {:?}", client_key.public());
let shared_secret = client_key.shared(&server_key.public());
send_client_key(
&mut writer,
&shared_secret,
&client_key.public(),
&client_info,
)
.await?;
let (client_pub_key, got_client_info, _) = recv_client_key(server_key, &mut reader).await?;
assert_eq!(client_key.public(), client_pub_key);
assert_eq!(client_info, got_client_info);
Ok(())
}
}
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