Handle client-disabled server push (#486)

src/codec/error.rs

@@ -63,6 +63,9 @@ pub enum UserError {
 
     /// Tries to update local SETTINGS while ACK has not been received.
     SendSettingsWhilePending,
+
+    /// Tries to send push promise to peer who has disabled server push
+    PeerDisabledServerPush,
 }
 
 // ===== impl RecvError =====
@@ -136,6 +139,7 @@ impl fmt::Display for UserError {
             PollResetAfterSendResponse => "poll_reset after send_response is illegal",
             SendPingWhilePending => "send_ping before received previous pong",
             SendSettingsWhilePending => "sending SETTINGS before received previous ACK",
+            PeerDisabledServerPush => "sending PUSH_PROMISE to peer who disabled server push",
         })
     }
 }

src/frame/settings.rs

@@ -99,8 +99,8 @@ impl Settings {
         self.max_header_list_size = size;
     }
 
-    pub fn is_push_enabled(&self) -> bool {
-        self.enable_push.unwrap_or(1) != 0
+    pub fn is_push_enabled(&self) -> Option<bool> {
+        self.enable_push.map(|val| val != 0)
     }
 
     pub fn set_enable_push(&mut self, enable: bool) {

src/proto/connection.rs

@@ -86,7 +86,7 @@ where
                 .unwrap_or(DEFAULT_INITIAL_WINDOW_SIZE),
             initial_max_send_streams: config.initial_max_send_streams,
             local_next_stream_id: config.next_stream_id,
-            local_push_enabled: config.settings.is_push_enabled(),
+            local_push_enabled: config.settings.is_push_enabled().unwrap_or(true),
             local_reset_duration: config.reset_stream_duration,
             local_reset_max: config.reset_stream_max,
             remote_init_window_sz: DEFAULT_INITIAL_WINDOW_SIZE,

src/proto/streams/send.rs

@@ -32,6 +32,8 @@ pub(super) struct Send {
 
     /// Prioritization layer
     prioritize: Prioritize,
+
+    is_push_enabled: bool,
 }
 
 /// A value to detect which public API has called `poll_reset`.
@@ -49,6 +51,7 @@ impl Send {
             max_stream_id: StreamId::MAX,
             next_stream_id: Ok(config.local_next_stream_id),
             prioritize: Prioritize::new(config),
+            is_push_enabled: true,
         }
     }
 
@@ -95,6 +98,10 @@ impl Send {
         stream: &mut store::Ptr,
         task: &mut Option<Waker>,
     ) -> Result<(), UserError> {
+        if !self.is_push_enabled {
+            return Err(UserError::PeerDisabledServerPush);
+        }
+
         tracing::trace!(
             "send_push_promise; frame={:?}; init_window={:?}",
             frame,
@@ -496,6 +503,10 @@ impl Send {
             }
         }
 
+        if let Some(val) = settings.is_push_enabled() {
+            self.is_push_enabled = val
+        }
+
         Ok(())
     }