fix: Fix EOF spin loop by removing intermediate buffer in LazyConfigAcceptor (#87)

* chore: Remove intermediate buffer in LazyConfigAcceptor

* chore: Document WouldBlock behavior

* chore: satisfy clippy

* chore: Rename Reader -> SyncReadAdapter

* chore: add test for EOF

tokio-rustls/src/common/mod.rs

@@ -89,24 +89,7 @@ where
     }
 
     pub fn read_io(&mut self, cx: &mut Context) -> Poll<io::Result<usize>> {
-        struct Reader<'a, 'b, T> {
-            io: &'a mut T,
-            cx: &'a mut Context<'b>,
-        }
-
-        impl<'a, 'b, T: AsyncRead + Unpin> Read for Reader<'a, 'b, T> {
-            #[inline]
-            fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
-                let mut buf = ReadBuf::new(buf);
-                match Pin::new(&mut self.io).poll_read(self.cx, &mut buf) {
-                    Poll::Ready(Ok(())) => Ok(buf.filled().len()),
-                    Poll::Ready(Err(err)) => Err(err),
-                    Poll::Pending => Err(io::ErrorKind::WouldBlock.into()),
-                }
-            }
-        }
-
-        let mut reader = Reader { io: self.io, cx };
+        let mut reader = SyncReadAdapter { io: self.io, cx };
 
         let n = match self.session.read_tls(&mut reader) {
             Ok(n) => n,
@@ -145,7 +128,7 @@ where
                 &mut self,
                 f: impl FnOnce(Pin<&mut T>, &mut Context<'_>) -> Poll<io::Result<U>>,
             ) -> io::Result<U> {
-                match f(Pin::new(&mut self.io), self.cx) {
+                match f(Pin::new(self.io), self.cx) {
                     Poll::Ready(result) => result,
                     Poll::Pending => Err(io::ErrorKind::WouldBlock.into()),
                 }
@@ -343,5 +326,26 @@ where
     }
 }
 
+/// An adapter that implements a [`Read`] interface for [`AsyncRead`] types and an
+/// associated [`Context`].
+///
+/// Turns `Poll::Pending` into `WouldBlock`.
+pub struct SyncReadAdapter<'a, 'b, T> {
+    pub io: &'a mut T,
+    pub cx: &'a mut Context<'b>,
+}
+
+impl<'a, 'b, T: AsyncRead + Unpin> Read for SyncReadAdapter<'a, 'b, T> {
+    #[inline]
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        let mut buf = ReadBuf::new(buf);
+        match Pin::new(&mut self.io).poll_read(self.cx, &mut buf) {
+            Poll::Ready(Ok(())) => Ok(buf.filled().len()),
+            Poll::Ready(Err(err)) => Err(err),
+            Poll::Pending => Err(io::ErrorKind::WouldBlock.into()),
+        }
+    }
+}
+
 #[cfg(test)]
 mod test_stream;

tokio-rustls/src/lib.rs

@@ -190,8 +190,6 @@ impl TlsAcceptor {
 
 pub struct LazyConfigAcceptor<IO> {
     acceptor: rustls::server::Acceptor,
-    buf: Vec<u8>,
-    used: usize,
     io: Option<IO>,
 }
 
@@ -203,8 +201,6 @@ where
     pub fn new(acceptor: rustls::server::Acceptor, io: IO) -> Self {
         Self {
             acceptor,
-            buf: vec![0; 512],
-            used: 0,
             io: Some(io),
         }
     }
@@ -229,25 +225,12 @@ where
                 }
             };
 
-            let mut buf = ReadBuf::new(&mut this.buf);
-            buf.advance(this.used);
-            if buf.remaining() > 0 {
-                if let Err(err) = ready!(Pin::new(io).poll_read(cx, &mut buf)) {
-                    return Poll::Ready(Err(err));
-                }
-            }
-
-            let read = match this.acceptor.read_tls(&mut buf.filled()) {
-                Ok(read) => read,
-                Err(err) => return Poll::Ready(Err(err)),
-            };
-
-            let received = buf.filled().len();
-            if read < received {
-                this.buf.copy_within(read.., 0);
-                this.used = received - read;
-            } else {
-                this.used = 0;
+            let mut reader = common::SyncReadAdapter { io, cx };
+            match this.acceptor.read_tls(&mut reader) {
+                Ok(0) => return Err(io::ErrorKind::UnexpectedEof.into()).into(),
+                Ok(_) => {}
+                Err(e) if e.kind() == io::ErrorKind::WouldBlock => return Poll::Pending,
+                Err(e) => return Err(e).into(),
             }
 
             match this.acceptor.accept() {

tokio-rustls/tests/test.rs

@@ -3,14 +3,15 @@ use lazy_static::lazy_static;
 use rustls::{ClientConfig, OwnedTrustAnchor};
 use rustls_pemfile::{certs, rsa_private_keys};
 use std::convert::TryFrom;
-use std::io::{BufReader, Cursor};
+use std::io::{BufReader, Cursor, ErrorKind};
 use std::net::SocketAddr;
 use std::sync::mpsc::channel;
 use std::sync::Arc;
+use std::time::Duration;
 use std::{io, thread};
 use tokio::io::{copy, split, AsyncReadExt, AsyncWriteExt};
 use tokio::net::{TcpListener, TcpStream};
-use tokio::runtime;
+use tokio::{runtime, time};
 use tokio_rustls::{LazyConfigAcceptor, TlsAcceptor, TlsConnector};
 
 const CERT: &str = include_str!("end.cert");
@@ -202,5 +203,23 @@ async fn test_lazy_config_acceptor() -> io::Result<()> {
     Ok(())
 }
 
+// This test is a follow-up from https://github.com/tokio-rs/tls/issues/85
+#[tokio::test]
+async fn lazy_config_acceptor_eof() {
+    let buf = Cursor::new(Vec::new());
+    let acceptor = LazyConfigAcceptor::new(rustls::server::Acceptor::new().unwrap(), buf);
+
+    let accept_result = match time::timeout(Duration::from_secs(3), acceptor).await {
+        Ok(res) => res,
+        Err(_elapsed) => panic!("timeout"),
+    };
+
+    match accept_result {
+        Ok(_) => panic!("accepted a connection from zero bytes of data"),
+        Err(e) if e.kind() == ErrorKind::UnexpectedEof => {}
+        Err(e) => panic!("unexpected error: {:?}", e),
+    }
+}
+
 // Include `utils` module
 include!("utils.rs");