From 5ea24254a91c3794ceb69e68c940b13f5447f40c Mon Sep 17 00:00:00 2001
From: Alex Auvolat <alex@adnab.me>
Date: Tue, 13 Feb 2024 12:55:41 +0100
Subject: [import-netapp] import Netapp code into Garage codebase

---
 src/net/recv.rs | 153 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 153 insertions(+)
 create mode 100644 src/net/recv.rs

(limited to 'src/net/recv.rs')

diff --git a/src/net/recv.rs b/src/net/recv.rs
new file mode 100644
index 00000000..0de7bef2
--- /dev/null
+++ b/src/net/recv.rs
@@ -0,0 +1,153 @@
+use std::collections::HashMap;
+use std::sync::Arc;
+
+use async_trait::async_trait;
+use bytes::Bytes;
+use log::*;
+
+use futures::AsyncReadExt;
+use tokio::sync::mpsc;
+
+use crate::error::*;
+use crate::send::*;
+use crate::stream::*;
+
+/// Structure to warn when the sender is dropped before end of stream was reached, like when
+/// connection to some remote drops while transmitting data
+struct Sender {
+	inner: Option<mpsc::UnboundedSender<Packet>>,
+}
+
+impl Sender {
+	fn new(inner: mpsc::UnboundedSender<Packet>) -> Self {
+		Sender { inner: Some(inner) }
+	}
+
+	fn send(&self, packet: Packet) {
+		let _ = self.inner.as_ref().unwrap().send(packet);
+	}
+
+	fn end(&mut self) {
+		self.inner = None;
+	}
+}
+
+impl Drop for Sender {
+	fn drop(&mut self) {
+		if let Some(inner) = self.inner.take() {
+			let _ = inner.send(Err(std::io::Error::new(
+				std::io::ErrorKind::BrokenPipe,
+				"Netapp connection dropped before end of stream",
+			)));
+		}
+	}
+}
+
+/// The RecvLoop trait, which is implemented both by the client and the server
+/// connection objects (ServerConn and ClientConn) adds a method `.recv_loop()`
+/// and a prototype of a handler for received messages `.recv_handler()` that
+/// must be filled by implementors. `.recv_loop()` receives messages in a loop
+/// according to the protocol defined above: chunks of message in progress of being
+/// received are stored in a buffer, and when the last chunk of a message is received,
+/// the full message is passed to the receive handler.
+#[async_trait]
+pub(crate) trait RecvLoop: Sync + 'static {
+	fn recv_handler(self: &Arc<Self>, id: RequestID, stream: ByteStream);
+	fn cancel_handler(self: &Arc<Self>, _id: RequestID) {}
+
+	async fn recv_loop<R>(self: Arc<Self>, mut read: R, debug_name: String) -> Result<(), Error>
+	where
+		R: AsyncReadExt + Unpin + Send + Sync,
+	{
+		let mut streams: HashMap<RequestID, Sender> = HashMap::new();
+		loop {
+			trace!(
+				"recv_loop({}): in_progress = {:?}",
+				debug_name,
+				streams.iter().map(|(id, _)| id).collect::<Vec<_>>()
+			);
+
+			let mut header_id = [0u8; RequestID::BITS as usize / 8];
+			match read.read_exact(&mut header_id[..]).await {
+				Ok(_) => (),
+				Err(e) if e.kind() == std::io::ErrorKind::UnexpectedEof => break,
+				Err(e) => return Err(e.into()),
+			};
+			let id = RequestID::from_be_bytes(header_id);
+
+			let mut header_size = [0u8; ChunkLength::BITS as usize / 8];
+			read.read_exact(&mut header_size[..]).await?;
+			let size = ChunkLength::from_be_bytes(header_size);
+
+			if size == CANCEL_REQUEST {
+				if let Some(mut stream) = streams.remove(&id) {
+					let _ = stream.send(Err(std::io::Error::new(
+						std::io::ErrorKind::Other,
+						"netapp: cancel requested",
+					)));
+					stream.end();
+				}
+				self.cancel_handler(id);
+				continue;
+			}
+
+			let has_cont = (size & CHUNK_FLAG_HAS_CONTINUATION) != 0;
+			let is_error = (size & CHUNK_FLAG_ERROR) != 0;
+			let size = (size & CHUNK_LENGTH_MASK) as usize;
+			let mut next_slice = vec![0; size as usize];
+			read.read_exact(&mut next_slice[..]).await?;
+
+			let packet = if is_error {
+				let kind = u8_to_io_errorkind(next_slice[0]);
+				let msg =
+					std::str::from_utf8(&next_slice[1..]).unwrap_or("<invalid utf8 error message>");
+				debug!(
+					"recv_loop({}): got id {}, error {:?}: {}",
+					debug_name, id, kind, msg
+				);
+				Some(Err(std::io::Error::new(kind, msg.to_string())))
+			} else {
+				trace!(
+					"recv_loop({}): got id {}, size {}, has_cont {}",
+					debug_name,
+					id,
+					size,
+					has_cont
+				);
+				if !next_slice.is_empty() {
+					Some(Ok(Bytes::from(next_slice)))
+				} else {
+					None
+				}
+			};
+
+			let mut sender = if let Some(send) = streams.remove(&(id)) {
+				send
+			} else {
+				let (send, recv) = mpsc::unbounded_channel();
+				trace!("recv_loop({}): id {} is new channel", debug_name, id);
+				self.recv_handler(
+					id,
+					Box::pin(tokio_stream::wrappers::UnboundedReceiverStream::new(recv)),
+				);
+				Sender::new(send)
+			};
+
+			if let Some(packet) = packet {
+				// If we cannot put packet in channel, it means that the
+				// receiving end of the channel is disconnected.
+				// We still need to reach eos before dropping this sender
+				let _ = sender.send(packet);
+			}
+
+			if has_cont {
+				assert!(!is_error);
+				streams.insert(id, sender);
+			} else {
+				trace!("recv_loop({}): close channel id {}", debug_name, id);
+				sender.end();
+			}
+		}
+		Ok(())
+	}
+}
-- 
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