Change stream ID handling to consider flags. (#436)

Replaces the former odd/even distinction of IDs. However we still increment stream IDs by 2
for backwards compatibility.

core/src/upgrade/traits.rs

@@ -20,10 +20,10 @@
 
 use bytes::Bytes;
 use futures::future::Future;
-use std::io::Error as IoError;
+use std::{io::Error as IoError, ops::Not};
 
 /// Type of connection for the upgrade.
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
 pub enum Endpoint {
     /// The socket comes from a dialer.
     Dialer,
@@ -31,6 +31,18 @@ pub enum Endpoint {
     Listener,
 }
 
+impl Not for Endpoint {
+    type Output = Endpoint;
+
+    fn not(self) -> Self::Output {
+        match self {
+            Endpoint::Dialer => Endpoint::Listener,
+            Endpoint::Listener => Endpoint::Dialer
+        }
+    }
+}
+
+
 /// Implemented on structs that describe a possible upgrade to a connection between two peers.
 ///
 /// The generic `C` is the type of the incoming connection before it is upgraded.

muxers/mplex/src/codec.rs

@@ -49,6 +49,15 @@ impl Elem {
         }
     }
 
+    pub fn endpoint(&self) -> Option<Endpoint> {
+        match *self {
+            Elem::Open { .. } => None,
+            Elem::Data { endpoint, .. } => Some(endpoint),
+            Elem::Close { endpoint, .. } => Some(endpoint),
+            Elem::Reset { endpoint, .. } => Some(endpoint)
+        }
+    }
+
     /// Returns true if this message is `Close` or `Reset`.
     #[inline]
     pub fn is_close_or_reset_msg(&self) -> bool {

muxers/mplex/src/lib.rs

@@ -171,7 +171,9 @@ struct MultiplexInner<C> {
     buffer: Vec<codec::Elem>,
     // List of Ids of opened substreams. Used to filter out messages that don't belong to any
     // substream. Note that this is handled exclusively by `next_match`.
-    opened_substreams: FnvHashSet<u32>,
+    // The `Endpoint` value denotes who initiated the substream from our point of view
+    // (see note [StreamId]).
+    opened_substreams: FnvHashSet<(u32, Endpoint)>,
     // Id of the next outgoing substream. Should always increase by two.
     next_outbound_stream_id: u32,
     /// List of tasks to notify when a read event happens on the underlying stream.
@@ -200,6 +202,16 @@ task_local!{
     static TASK_ID: usize = NEXT_TASK_ID.fetch_add(1, Ordering::Relaxed)
 }
 
+// Note [StreamId]: mplex no longer partitions stream IDs into odd (for initiators) and
+// even ones (for receivers). Streams are instead identified by a number and whether the flag
+// is odd (for receivers) or even (for initiators). `Open` frames do not have a flag, but are
+// sent unidirectional. As a consequence, we need to remember if the stream was initiated by us
+// or remotely and we store the information from our point of view, i.e. receiving an `Open` frame
+// is stored as `(<u32>, Listener)`, sending an `Open` frame as `(<u32>, Dialer)`. Receiving
+// a `Data` frame with flag `MessageReceiver` (= 1) means that we initiated the stream, so the
+// entry has been stored as `(<u32>, Dialer)`. So, when looking up streams based on frames
+// received, we have to invert the `Endpoint`, except for `Open`.
+
 /// Processes elements in `inner` until one matching `filter` is found.
 ///
 /// If `NotReady` is returned, the current task is scheduled for later, just like with any `Poll`.
@@ -259,25 +271,21 @@ where C: AsyncRead + AsyncWrite,
         // Handle substreams opening/closing.
         match elem {
             codec::Elem::Open { substream_id } => {
-                if (substream_id % 2) == (inner.next_outbound_stream_id % 2) {
-                    inner.error = Err(IoError::new(IoErrorKind::Other, "invalid substream id opened"));
-                    return Err(IoError::new(IoErrorKind::Other, "invalid substream id opened"));
-                }
-
-                if !inner.opened_substreams.insert(substream_id) {
+                if !inner.opened_substreams.insert((substream_id, Endpoint::Listener)) {
                     debug!("Received open message for substream {} which was already open", substream_id)
                 }
-            },
-            codec::Elem::Close { substream_id, .. } | codec::Elem::Reset { substream_id, .. } => {
-                inner.opened_substreams.remove(&substream_id);
-            },
+            }
+            codec::Elem::Close { substream_id, endpoint, .. } | codec::Elem::Reset { substream_id, endpoint, .. } => {
+                inner.opened_substreams.remove(&(substream_id, !endpoint));
+            }
             _ => ()
         }
 
         if let Some(out) = filter(&elem) {
             return Ok(Async::Ready(Some(out)));
         } else {
-            if inner.opened_substreams.contains(&elem.substream_id()) || elem.is_open_msg() {
+            let endpoint = elem.endpoint().unwrap_or(Endpoint::Dialer);
+            if inner.opened_substreams.contains(&(elem.substream_id(), !endpoint)) || elem.is_open_msg() {
                 inner.buffer.push(elem);
             } else if !elem.is_close_or_reset_msg() {
                 debug!("Ignored message {:?} because the substream wasn't open", elem);
@@ -346,7 +354,7 @@ where C: AsyncRead + AsyncWrite
             n
         };
 
-        inner.opened_substreams.insert(substream_id);
+        inner.opened_substreams.insert((substream_id, Endpoint::Dialer));
 
         OutboundSubstream {
             num: substream_id,
@@ -423,10 +431,12 @@ where C: AsyncRead + AsyncWrite
             let mut inner = self.inner.lock();
             let next_data_poll = next_match(&mut inner, |elem| {
                 match elem {
-                    &codec::Elem::Data { ref substream_id, ref data, .. } if *substream_id == substream.num => {     // TODO: check endpoint?
+                    codec::Elem::Data { substream_id, endpoint, data, .. }
+                        if *substream_id == substream.num && *endpoint != substream.endpoint => // see note [StreamId]
+                    {
                         Some(data.clone())
-                    },
-                    _ => None,
+                    }
+                    _ => None
                 }
             });
 
@@ -438,7 +448,7 @@ where C: AsyncRead + AsyncWrite
                 Ok(Async::NotReady) => {
                     // There was no data packet in the buffer about this substream ; maybe it's
                     // because it has been closed.
-                    if inner.opened_substreams.contains(&substream.num) {
+                    if inner.opened_substreams.contains(&(substream.num, substream.endpoint)) {
                         return Err(IoErrorKind::WouldBlock.into());
                     } else {
                         return Ok(0);