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// Jackson Coxson
use frame::HttpFrame;
use std::collections::{HashMap, VecDeque};
use tokio::io::{AsyncReadExt, AsyncWriteExt};
use tracing::{debug, warn};
use crate::{IdeviceError, ReadWrite};
pub mod frame;
pub use frame::Setting;
const HTTP2_MAGIC: &[u8] = "PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n".as_bytes();
/// HTTP/2 default initial flow-control window for both the connection and each
/// stream (RFC 7540 §6.9.2). The peer can raise the per-stream default via a
/// SETTINGS `InitialWindowSize`.
const DEFAULT_WINDOW: i64 = 65535;
#[derive(Debug)]
pub struct Http2Client<R: ReadWrite> {
inner: R,
cache: HashMap<u32, VecDeque<Vec<u8>>>,
/// How many payload octets we may still send on the connection as a whole
/// before the peer must replenish it with a connection-level WINDOW_UPDATE.
conn_send_window: i64,
/// Per-stream remaining send window. Lazily seeded to `peer_initial_window`.
stream_send_windows: HashMap<u32, i64>,
/// The peer's current SETTINGS `InitialWindowSize` — the window each *new*
/// stream starts with.
peer_initial_window: i64,
/// Raw inbound bytes not yet parsed into a whole frame. Persisting this
/// across reads keeps [`Self::pump`] (and therefore `recv_push`)
/// cancellation-safe: a partially-received frame survives a dropped read.
recv_buf: Vec<u8>,
}
impl<R: ReadWrite> Http2Client<R> {
/// Writes the magic and inits the caches
pub async fn new(mut inner: R) -> Result<Self, IdeviceError> {
inner.write_all(HTTP2_MAGIC).await?;
inner.flush().await?;
Ok(Self {
inner,
cache: HashMap::new(),
conn_send_window: DEFAULT_WINDOW,
stream_send_windows: HashMap::new(),
peer_initial_window: DEFAULT_WINDOW,
recv_buf: Vec::new(),
})
}
/// Read the next whole frame, buffering raw bytes in `recv_buf` until one is
/// complete. Cancellation-safe: the single `read` is cancel-safe (no bytes
/// lost if the future is dropped on `Pending`), and any bytes already
/// buffered persist in `self` for the next call.
async fn next_frame(&mut self) -> Result<frame::Frame, IdeviceError> {
loop {
if let Some((frame, consumed)) = frame::Frame::parse(&self.recv_buf)? {
self.recv_buf.drain(..consumed);
return Ok(frame);
}
let mut tmp = [0u8; 16384];
let n = self.inner.read(&mut tmp).await?;
if n == 0 {
return Err(IdeviceError::UnexpectedResponse(
"HTTP/2 connection closed by peer".into(),
));
}
self.recv_buf.extend_from_slice(&tmp[..n]);
}
}
pub async fn set_settings(
&mut self,
settings: Vec<frame::Setting>,
stream_id: u32,
) -> Result<(), IdeviceError> {
let frame = frame::SettingsFrame {
settings,
stream_id,
flags: 0,
}
.serialize();
self.inner.write_all(&frame).await?;
self.inner.flush().await?;
Ok(())
}
pub async fn window_update(
&mut self,
increment_size: u32,
stream_id: u32,
) -> Result<(), IdeviceError> {
let frame = frame::WindowUpdateFrame {
increment_size,
stream_id,
}
.serialize();
self.inner.write_all(&frame).await?;
self.inner.flush().await?;
Ok(())
}
pub async fn open_stream(&mut self, stream_id: u32) -> Result<(), IdeviceError> {
// Sometimes Apple is silly and sends data to a stream that isn't open
self.cache.entry(stream_id).or_default();
let frame = frame::HeadersFrame { stream_id }.serialize();
self.inner.write_all(&frame).await?;
self.inner.flush().await?;
Ok(())
}
pub async fn send(&mut self, payload: Vec<u8>, stream_id: u32) -> Result<(), IdeviceError> {
const MAX_FRAME_SIZE: usize = 16384;
let mut chunks = payload.chunks(MAX_FRAME_SIZE).peekable();
// Always send at least one frame, even for an empty payload. An empty
// DATA frame costs no flow-control window, so send it directly.
if chunks.peek().is_none() {
let frame = frame::DataFrame {
stream_id,
payload: Vec::new(),
}
.serialize();
self.inner.write_all(&frame).await?;
self.inner.flush().await?;
return Ok(());
}
for chunk in chunks {
let need = chunk.len() as i64;
// Respect the peer's flow-control window: a DATA frame must not exceed
// either the connection-level or the stream-level send window, or the
// peer aborts the connection with a GOAWAY (FLOW_CONTROL_ERROR). When
// either window is exhausted, pump inbound frames until the peer grants
// more room with a WINDOW_UPDATE. (Matters for large payloads like
// pasteboard images; small ones fit in the initial 64 KiB window.)
while self.conn_send_window < need || self.stream_send_window(stream_id) < need {
self.pump().await?;
}
let frame = frame::DataFrame {
stream_id,
payload: chunk.to_vec(),
}
.serialize();
self.inner.write_all(&frame).await?;
self.conn_send_window -= need;
*self
.stream_send_windows
.get_mut(&stream_id)
.expect("seeded by stream_send_window above") -= need;
}
self.inner.flush().await?;
Ok(())
}
/// The remaining send window for `stream_id`, seeding it to the peer's current
/// initial window size the first time we touch the stream.
fn stream_send_window(&mut self, stream_id: u32) -> i64 {
*self
.stream_send_windows
.entry(stream_id)
.or_insert(self.peer_initial_window)
}
pub async fn read(&mut self, stream_id: u32) -> Result<Vec<u8>, IdeviceError> {
self.cache.entry(stream_id).or_default();
loop {
// Return any frame already buffered for this stream.
if let Some(d) = self.cache.get_mut(&stream_id).and_then(|c| c.pop_front()) {
return Ok(d);
}
self.pump().await?;
}
}
/// Read and handle a single inbound frame: ack SETTINGS (applying any
/// `InitialWindowSize` change), apply WINDOW_UPDATEs to our send windows,
/// replenish the peer's receive window for inbound DATA and buffer that DATA
/// by stream. GOAWAY / RST_STREAM surface as errors via [`frame::Frame::next`].
async fn pump(&mut self) -> Result<(), IdeviceError> {
let frame = self.next_frame().await?;
match frame {
frame::Frame::Settings(settings_frame) if settings_frame.flags != 1 => {
// Adjust every existing stream's send window by the delta in the
// new InitialWindowSize (RFC 7540 §6.9.2), then ack.
for setting in &settings_frame.settings {
if let frame::Setting::InitialWindowSize(new) = setting {
let delta = *new as i64 - self.peer_initial_window;
self.peer_initial_window = *new as i64;
for w in self.stream_send_windows.values_mut() {
*w += delta;
}
}
}
let ack = frame::SettingsFrame {
settings: Vec::new(),
stream_id: settings_frame.stream_id,
flags: 1,
}
.serialize();
self.inner.write_all(&ack).await?;
self.inner.flush().await?;
}
frame::Frame::WindowUpdate(w) => {
if w.stream_id == 0 {
self.conn_send_window += w.increment_size as i64;
} else {
let initial = self.peer_initial_window;
*self
.stream_send_windows
.entry(w.stream_id)
.or_insert(initial) += w.increment_size as i64;
}
}
frame::Frame::Data(data_frame) => {
debug!(
"Got data frame for {} with {} bytes",
data_frame.stream_id,
data_frame.payload.len()
);
let len = data_frame.payload.len() as u32;
let stream_id = data_frame.stream_id;
// Cache the payload BEFORE any await so a cancelled pump (the poll
// tick interrupting `recv_push`) can never drop it.
self.cache
.entry(stream_id)
.or_insert_with(|| {
// Apple sometimes sends data before the stream is "open".
warn!("Received message for stream ID {stream_id} not in cache");
VecDeque::new()
})
.push_back(data_frame.payload);
if len > 0 {
// Replenish the peer's view of our receive window so it keeps
// sending (e.g. the rest of a large pasteboard image). Queue
// both WINDOW_UPDATE frames, then flush once: write_all on the
// tunnel stream queues a whole frame without suspending, so a
// cancellation can only land on the flush — by which point both
// frames are already queued (never a torn or dropped update).
let conn = frame::WindowUpdateFrame {
increment_size: len,
stream_id: 0,
}
.serialize();
let stream = frame::WindowUpdateFrame {
increment_size: len,
stream_id,
}
.serialize();
self.inner.write_all(&conn).await?;
self.inner.write_all(&stream).await?;
self.inner.flush().await?;
}
}
_ => {
// SETTINGS ack / HEADERS — nothing to do.
}
}
Ok(())
}
}