Http2 to origin fix (#4)

* Fix for connection level window mismatch + force connection level window update

* Fix for HPACK corruption on closed streams
Todo: check stream level error returns, these should still decode
  the headers to prevent HPACK corruption for following header
  frames

---------

Co-authored-by: Kees Spoelstra <kd.spoelstra@gmail.com>

Author: keesspoelstra

proxy/http2/Http2CommonSession.cc

@@ -369,6 +369,7 @@ Http2CommonSession::do_process_frame_read(int event, VIO *vio, bool inside_frame
     // Return if there was an error
     if (err > Http2ErrorCode::HTTP2_ERROR_NO_ERROR || do_start_frame_read(err) < 0) {
       // send an error if specified.  Otherwise, just go away
+      this->connection_state.restart_receiving(nullptr);
       if (err > Http2ErrorCode::HTTP2_ERROR_NO_ERROR) {
         if (!this->connection_state.is_state_closed()) {
           this->connection_state.send_goaway_frame(this->connection_state.get_latest_stream_id_in(), err);
@@ -387,6 +388,7 @@ Http2CommonSession::do_process_frame_read(int event, VIO *vio, bool inside_frame
 
     if (this->_should_do_something_else()) {
       if (this->_reenable_event == nullptr) {
+        this->connection_state.restart_receiving(nullptr);
         vio->disable();
         this->_reenable_event = this->get_mutex()->thread_holding->schedule_in(this->get_proxy_session(), HRTIME_MSECONDS(1),
                                                                                HTTP2_SESSION_EVENT_REENABLE, vio);
@@ -397,6 +399,7 @@ Http2CommonSession::do_process_frame_read(int event, VIO *vio, bool inside_frame
 
   // If the client hasn't shut us down, reenable
   if (!this->get_proxy_session()->is_peer_closed()) {
+    this->connection_state.restart_receiving(nullptr);
     vio->reenable();
   }
   return 0;

proxy/http2/Http2ConnectionState.cc

@@ -89,6 +89,9 @@ Http2ConnectionState::rcv_data_frame(const Http2Frame &frame)
 
   Http2StreamDebug(this->session, id, "Received DATA frame");
 
+  // Update connection window size, before any stream specific handling
+  this->decrement_local_rwnd(payload_length);
+
   if (this->get_zombie_event()) {
     Warning("Data frame for zombied session %" PRId64, this->session->get_connection_id());
   }
@@ -174,7 +177,8 @@ Http2ConnectionState::rcv_data_frame(const Http2Frame &frame)
   }
 
   // Check whether Window Size is acceptable
-  if (!this->_local_rwnd_is_shrinking && this->get_local_rwnd() < payload_length) {
+  // compare to 0 because we already decreased the connection rwnd with payload_length
+  if (!this->_local_rwnd_is_shrinking && this->get_local_rwnd() < 0) {
     return Http2Error(Http2ErrorClass::HTTP2_ERROR_CLASS_CONNECTION, Http2ErrorCode::HTTP2_ERROR_FLOW_CONTROL_ERROR,
                       "recv data this->local_rwnd < payload_length");
   }
@@ -183,8 +187,7 @@ Http2ConnectionState::rcv_data_frame(const Http2Frame &frame)
                       "recv data stream->local_rwnd < payload_length");
   }
 
-  // Update Window size
-  this->decrement_local_rwnd(payload_length);
+  // Update stream window size
   stream->decrement_local_rwnd(payload_length);
 
   if (is_debug_tag_set("http2_con")) {
@@ -316,9 +319,17 @@ Http2ConnectionState::rcv_headers_frame(const Http2Frame &frame)
     }
   }
 
-  // Ignoring HEADERS frame on a closed stream.  The HdrHeap has gone away and it will core.
+  // HEADERS frame on a closed stream.  The HdrHeap has gone away and it will core.
   if (stream->get_state() == Http2StreamState::HTTP2_STREAM_STATE_CLOSED) {
-    return Http2Error(Http2ErrorClass::HTTP2_ERROR_CLASS_NONE);
+    Http2StreamDebug(session, stream_id, "Replaced closed stream");
+    free_stream_after_decoding = true;
+    stream = THREAD_ALLOC_INIT(http2StreamAllocator, this_ethread(), session->get_proxy_session(), stream_id,
+                               peer_settings.get(HTTP2_SETTINGS_INITIAL_WINDOW_SIZE), true, false);
+    if (!stream) {
+      // This happening is possibly catastrophic, the HPACK tables can be out of sync
+      // Maybe this is a connection level error?
+      return Http2Error(Http2ErrorClass::HTTP2_ERROR_CLASS_NONE);
+    }
   }
 
   Http2HeadersParameter params;