Introduce support for OptionNegotiationFailed error code

Author: lazy404

examples/tftpd-dir.rs

@@ -11,7 +11,7 @@ async fn main() -> Result<()> {
         .expect("Failed to initialize logger");
 
     let tftpd = TftpServerBuilder::with_dir_ro(".")?
-        .bind("0.0.0.0:6969".parse().unwrap())
+        .bind("127.0.0.1:6969".parse().unwrap())
         // Workaround to handle cases where client is behind VPN
         .block_size_limit(1024)
         .build()

src/packet.rs

@@ -32,6 +32,7 @@ pub enum Error {
     UnknownTransferId,
     FileAlreadyExists,
     NoSuchUser,
+    OptionNegotiationFailed,
 }
 
 #[derive(Debug)]
@@ -192,6 +193,7 @@ impl Error {
             5 => Error::UnknownTransferId,
             6 => Error::FileAlreadyExists,
             7 => Error::NoSuchUser,
+            8 => Error::OptionNegotiationFailed,
             0 | _ => match msg {
                 Some(msg) => Error::Msg(msg.to_string()),
                 None => Error::UnknownError,
@@ -210,6 +212,7 @@ impl Error {
             Error::UnknownTransferId => 5,
             Error::FileAlreadyExists => 6,
             Error::NoSuchUser => 7,
+            Error::OptionNegotiationFailed => 8,
         }
     }
 
@@ -224,8 +227,13 @@ impl Error {
             Error::UnknownTransferId => "Unknown transfer ID",
             Error::FileAlreadyExists => "File already exists",
             Error::NoSuchUser => "No such user",
+            Error::OptionNegotiationFailed => "Option negotiation failed",
         }
     }
+
+    pub(crate) fn is_client_error(&self) -> bool {
+        matches!(self, Error::OptionNegotiationFailed)
+    }
 }
 
 impl From<Error> for Packet<'_> {

src/server/read_req.rs

@@ -77,12 +77,20 @@ where
     pub(crate) async fn handle(&mut self) {
         if let Err(e) = self.try_handle().await {
             trace!("RRQ request failed (peer: {}, error: {})", &self.peer, &e);
-            let mut buffer = BytesMut::with_capacity(DEFAULT_BLOCK_SIZE);
-            Packet::Error(e.into()).encode(&mut buffer);
-            let buf = buffer.split().freeze();
-            // Errors are never retransmitted.
-            // We do not care if `send_to` resulted to an IO error.
-            let _ = self.socket.send_to(&buf[..], self.peer).await;
+
+            if let Error::Packet(
+                crate::packet::Error::OptionNegotiationFailed,
+            ) = e
+            {
+                // client aborted the connection, nothing to do
+            } else {
+                let mut buffer = BytesMut::with_capacity(DEFAULT_BLOCK_SIZE);
+                Packet::Error(e.into()).encode(&mut buffer);
+                let buf = buffer.split().freeze();
+                // Errors are never retransmitted.
+                // We do not care if `send_to` resulted to an IO error.
+                let _ = self.socket.send_to(&buf[..], self.peer).await;
+            }
         }
     }
 
@@ -92,17 +100,20 @@ where
         let mut block_id: u16;
         let mut window_base: u16 = 1;
         let mut buf: Bytes;
-        let mut is_last_block: bool;
+        let mut is_last_block: bool = false;
 
-        (buf, is_last_block) = self.fill_data_block(window_base).await?;
-        window.push_back(buf);
-
-        // Send OACK after we manage to read the first block from reader.
-        //
-        // We do this because we want to give the developers the option to
-        // produce an error after they construct a reader.
-        if let Some(opts) = self.oack_opts.as_ref() {
+        if let Some(opts) = self.oack_opts.take() {
             trace!("RRQ OACK (peer: {}, opts: {:?}", &self.peer, &opts);
+            // Send OACK after we manage to read the first block from the reader for
+            // non-transfer size probe requests (oack.transfer_size value is set).
+            // During transfer size probes a client aborts the connection after receiving
+            // oack from the server. For normal requests we do this because we want to give
+            // the developers the option to produce an error after they construct a reader.
+            if opts.transfer_size.is_none() {
+                (buf, is_last_block) =
+                    self.fill_data_block(window_base).await?;
+                window.push_back(buf);
+            }
             let mut buff = BytesMut::with_capacity(PACKET_DATA_HEADER_LEN + 64);
             Packet::OAck(opts.to_owned()).encode(&mut buff);
             // OACK is not really part of the window, so we send it separately
@@ -186,15 +197,17 @@ where
                     );
                     return Ok(blocks_acked);
                 }
-                Err(ref e) if e.kind() == io::ErrorKind::TimedOut => {
+                Err(Error::Io(ref e))
+                    if e.kind() == io::ErrorKind::TimedOut =>
+                {
                     trace!(
                         "RRQ (peer: {}, block_id: {}) - Timeout",
                         &self.peer,
                         window_base
                     );
                     continue;
                 }
-                Err(e) => return Err(e.into()),
+                Err(e) => return Err(e),
             }
         }
 
@@ -206,7 +219,7 @@ where
         &mut self,
         window_base: u16,
         window_len: u16,
-    ) -> io::Result<u16> {
+    ) -> Result<u16> {
         // We can not use `self` within `async_std::io::timeout` because not all
         // struct members implement `Sync`. So we borrow only what we need.
         let socket = &mut self.socket;
@@ -224,30 +237,37 @@ where
                 }
 
                 // parse only valid Ack packets, the rest are ignored
-                if let Ok(Packet::Ack(recved_block_id)) =
-                    Packet::decode(&buf[..len])
+                // if let Ok(Packet::Ack(recved_block_id)) =
+                match Packet::decode(&buf[..len])
                 {
-                    let window_end = window_base.wrapping_add(window_len);
-
-                    if window_end > window_base {
-                        // window_end did not wrap
-                        if recved_block_id >= window_base && recved_block_id < window_end {
-                            // number of blocks acked
-                            return Ok(recved_block_id-window_base+1u16);
-                        }
-                        else {
-                            trace!("Unexpected ack packet {recved_block_id}, window_base: {window_base}, window_len: {window_len}");
-                        }
-                    }else {
-                        // window_end wrapped
-                        if recved_block_id >= window_base {
-                            return Ok(1u16 + (recved_block_id - window_base));
-                        } else if recved_block_id < window_end {
-                            return Ok(1u16 + recved_block_id + (window_len - window_end));
+                    Ok(Packet::Ack(recved_block_id)) => {
+                        let window_end = window_base.wrapping_add(window_len);
+
+                        if window_end > window_base {
+                            // window_end did not wrap
+                            if recved_block_id >= window_base && recved_block_id < window_end {
+                                // number of blocks acked
+                                return Ok(recved_block_id - window_base + 1u16);
+                            } else {
+                                trace!("Unexpected ack packet {recved_block_id}, window_base: {window_base}, window_len: {window_len}");
+                            }
                         } else {
-                            trace!("Unexpected ack packet {recved_block_id}, window_base: {window_base}, window_len: {window_len}");
+                            // window_end wrapped
+                            if recved_block_id >= window_base {
+                                return Ok(1u16 + (recved_block_id - window_base));
+                            } else if recved_block_id < window_end {
+                                return Ok(1u16 + recved_block_id + (window_len - window_end));
+                            } else {
+                                trace!("Unexpected ack packet {recved_block_id}, window_base: {window_base}, window_len: {window_len}");
+                            }
                         }
+                    },
+                     Ok(Packet::Error(error)) if error.is_client_error()=> {
+                         // pass errors coming from the client
+                        return Err(Error::Packet(error))
                     }
+                    // ignore all other errors
+                    _ => {}
                 }
             }
         })

src/server/write_req.rs

@@ -75,12 +75,20 @@ where
     pub(crate) async fn handle(&mut self) {
         if let Err(e) = self.try_handle().await {
             trace!("WRQ request failed (peer: {}, error: {}", self.peer, &e);
-
-            Packet::Error(e.into()).encode(&mut self.buffer);
-            let buf = self.buffer.split().freeze();
-            // Errors are never retransmitted.
-            // We do not care if `send_to` resulted to an IO error.
-            let _ = self.socket.send_to(&buf[..], self.peer).await;
+            match e {
+                Error::Packet(client_error)
+                    if client_error.is_client_error() =>
+                {
+                    //we don't have to acknowledge client errors}
+                }
+                e => {
+                    Packet::Error(e.into()).encode(&mut self.buffer);
+                    let buf = self.buffer.split().freeze();
+                    // Errors are never retransmitted.
+                    // We do not care if `send_to` resulted to an IO error.
+                    let _ = self.socket.send_to(&buf[..], self.peer).await;
+                }
+            }
         }
     }
 
@@ -122,19 +130,21 @@ where
                     self.socket.send_to(&self.ack, self.peer).await?;
                     return Ok(data);
                 }
-                Err(ref e) if e.kind() == io::ErrorKind::TimedOut => {
+                Err(Error::Io(ref e))
+                    if e.kind() == io::ErrorKind::TimedOut =>
+                {
                     // On timeout reply with the previous ACK packet
                     self.socket.send_to(&self.ack, self.peer).await?;
                     continue;
                 }
-                Err(e) => return Err(e.into()),
+                Err(e) => return Err(e),
             }
         }
 
         Err(Error::MaxSendRetriesReached(self.peer, block_id))
     }
 
-    async fn recv_data_block(&mut self, block_id: u16) -> io::Result<Bytes> {
+    async fn recv_data_block(&mut self, block_id: u16) -> Result<Bytes> {
         let socket = &mut self.socket;
         let peer = self.peer;
 

src/tests/client.rs

@@ -0,0 +1,111 @@
+use crate::packet::Error::OptionNegotiationFailed;
+use crate::packet::{self, Mode, Opts, RwReq};
+use crate::server::TftpServerBuilder;
+use async_executor::Executor;
+use async_io::{Async, Timer};
+use futures_lite::future::block_on;
+use futures_lite::{future, AsyncRead};
+use std::cell::Cell;
+use std::io;
+use std::net::UdpSocket;
+use std::rc::Rc;
+use std::sync::Arc;
+
+use super::handlers::*;
+use super::packet::packet_to_bytes;
+use std::task::Poll;
+use std::time::Duration;
+
+struct ResultsReader {
+    results: Vec<io::Result<Vec<u8>>>,
+}
+
+impl AsyncRead for ResultsReader {
+    fn poll_read(
+        self: std::pin::Pin<&mut Self>,
+        _cx: &mut std::task::Context<'_>,
+        buf: &mut [u8],
+    ) -> Poll<io::Result<usize>> {
+        Poll::Ready(match self.get_mut().results.pop() {
+            Some(Ok(result)) => {
+                buf[..result.len()].copy_from_slice(&result);
+                Ok(result.len())
+            }
+            Some(Err(err)) => Err(err),
+            None => Err(io::ErrorKind::NotFound.into()),
+        })
+    }
+}
+
+#[test]
+fn test_abort_on_read_error() {
+    let ex = Arc::new(Executor::new());
+    let transferred = Rc::new(Cell::new(false));
+
+    block_on(ex.run({
+        let ex = ex.clone();
+        let transferred = transferred.clone();
+
+        async move {
+            let handler = ReaderHandler::new(ResultsReader { results: vec![Err(io::ErrorKind::InvalidInput.into())] }, Some(4));
+            let tftpd = TftpServerBuilder::with_handler(handler)
+                .bind("127.0.0.1:0".parse().unwrap())
+                .timeout(Duration::from_secs(1))
+                .build()
+                .await
+                .unwrap();
+            let addr = tftpd.listen_addr().unwrap();
+            // start server
+            let server_task = ex.spawn(async move {
+                tftpd.serve().await.unwrap();
+            });
+
+            let socket = Async::<UdpSocket>::bind(([127, 0, 0, 1], 0)).unwrap();
+            // send rrq with transfer size to 0 to simulate a transfer size probe
+            let req_opts = Opts {
+                transfer_size: Some(0),
+                ..Default::default()
+            };
+            let rrq = packet::Packet::Rrq(RwReq {
+                filename: "abc".to_string(),
+                mode: Mode::Octet,
+                opts: req_opts,
+            });
+            socket.send_to(&packet_to_bytes(&rrq), addr).await.unwrap();
+
+            // read the ack
+            let mut buf = [0u8; 1024];
+            let (len, peer) = socket.recv_from(&mut buf).await.unwrap();
+            let response = packet::Packet::decode(&buf[..len]).unwrap();
+            assert!(matches!(
+                    response,
+                    packet::Packet::OAck(Opts {transfer_size: Some(4),..})),
+                "Server did not send OAck packet: {:?}", response);
+
+            // send error packet
+            let abort_packet = packet::Packet::Error(OptionNegotiationFailed);
+            socket.send_to(&packet_to_bytes(&abort_packet), peer).await.unwrap();
+
+            // make sure the server doesn't send anything else
+            assert!(
+                future::race(
+                    async move {
+                        Timer::after(Duration::from_secs(3)).await;
+                        true
+                    },
+                    async move {
+                        // fail if we get anything after sending OptionNegotiationFailed error
+                        let _ = socket.recv_from(&mut buf).await.unwrap();
+                        false
+                    }
+                )
+                    .await,
+                "Server sent data after client sent OptionNegotiationFailed error"
+            );
+            server_task.cancel().await;
+            transferred.set(true);
+        }
+        }));
+
+    assert!(transferred.get());
+}