Remove additive flag.

Always interpret the initial window update as additive.

src/connection.rs

@@ -466,7 +466,6 @@ impl<T: AsyncRead + AsyncWrite + Unpin> Connection<T> {
                 if !self.config.lazy_open {
                     let mut frame = Frame::window_update(id, self.config.receive_window);
                     frame.header_mut().syn();
-                    frame.header_mut().additive();
                     log::trace!("{}: sending initial {}", self.id, frame.header());
                     self.socket.get_mut().send(&frame).await.or(Err(ConnectionError::Closed))?
                 }
@@ -747,7 +746,6 @@ impl<T: AsyncRead + AsyncWrite + Unpin> Connection<T> {
         }
 
         let is_finish = frame.header().flags().contains(header::FIN); // half-close
-        let is_additive = frame.header().flags().contains(header::ADD); // additive window update
 
         if frame.header().flags().contains(header::SYN) { // new stream
             if !self.is_valid_remote_id(stream_id, Tag::WindowUpdate) {
@@ -763,7 +761,7 @@ impl<T: AsyncRead + AsyncWrite + Unpin> Connection<T> {
                 return Action::Terminate(Frame::protocol_error())
             }
             let stream = {
-                let credit = frame.header().credit() + if is_additive { DEFAULT_CREDIT } else { 0 };
+                let credit = frame.header().credit() + DEFAULT_CREDIT;
                 let config = self.config.clone();
                 let sender = self.stream_sender.clone();
                 let mut stream = Stream::new(stream_id, self.id, config, DEFAULT_CREDIT, credit, sender);

src/frame/header.rs

@@ -99,11 +99,6 @@ impl<T: HasSyn> Header<T> {
     pub fn syn(&mut self) {
         self.flags.0 |= SYN.0
     }
-
-    /// Set the [`ADD`] flag.
-    pub fn additive(&mut self) {
-        self.flags.0 |= ADD.0
-    }
 }
 
 impl<T: HasAck> Header<T> {
@@ -349,10 +344,6 @@ pub const FIN: Flags = Flags(4);
 /// Indicates an immediate stream reset.
 pub const RST: Flags = Flags(8);
 
-/// Temporary flag indicating that the initial window update is additive.
-/// (See https://github.com/paritytech/yamux/issues/92)
-pub const ADD: Flags = Flags(0x8000);
-
 /// The serialised header size in bytes.
 pub const HEADER_SIZE: usize = 12;