Fix race in close frames during reads

CHANGELOG.md

@@ -3,6 +3,7 @@
 WebSocket
 
 * Fix race in pings during reads
+* Fix race in close frames during reads
 
 --------------------------------------------------------------------------------
 

include/beast/websocket/impl/close.ipp

@@ -147,25 +147,33 @@ operator()(error_code ec, bool again)
                         boost::asio::error::operation_aborted));
                 return;
             }
-            // fall through
+            d.ws.wr_block_ = &d;
+            // [[fallthrough]]
 
         case 1:
             // send close frame
+            BOOST_ASSERT(d.ws.wr_block_ == &d);
             d.state = 99;
             d.ws.wr_close_ = true;
-            BOOST_ASSERT(! d.ws.wr_block_);
-            d.ws.wr_block_ = &d;
             boost::asio::async_write(d.ws.stream_,
                 d.fb.data(), std::move(*this));
             return;
 
         case 2:
+            BOOST_ASSERT(! d.ws.wr_block_);
+            d.ws.wr_block_ = &d;
             d.state = 3;
+            // The current context is safe but might not be
+            // the same as the one for this operation (since
+            // we are being called from a write operation).
+            // Call post to make sure we are invoked the same
+            // way as the final handler for this operation.
             d.ws.get_io_service().post(
                 bind_handler(std::move(*this), ec));
             return;
 
         case 3:
+            BOOST_ASSERT(d.ws.wr_block_ == &d);
             if(d.ws.failed_ || d.ws.wr_close_)
             {
                 // call handler