Set EPOLLER flags when necessary

Author: tiif

src/shims/unix/unnamed_socket.rs

@@ -95,6 +95,10 @@ impl FileDescription for AnonSocket {
             // for read and write.
             epoll_ready_events.epollin = true;
             epoll_ready_events.epollout = true;
+            // If there is data lost in peer_fd, set EPOLLERR.
+            if self.peer_lost_data.get() {
+                epoll_ready_events.epollerr = true;
+            }
         }
         Ok(epoll_ready_events)
     }
@@ -105,6 +109,13 @@ impl FileDescription for AnonSocket {
         ecx: &mut MiriInterpCx<'tcx>,
     ) -> InterpResult<'tcx, io::Result<()>> {
         if let Some(peer_fd) = self.peer_fd().upgrade() {
+            // If the current readbuf is non-empty when the file description is closed,
+            // notify the peer that data lost has happened in current file description.
+            if let Some(readbuf) = &self.readbuf {
+                if !readbuf.borrow().buf.is_empty() {
+                    peer_fd.downcast::<AnonSocket>().unwrap().peer_lost_data.set(true);
+                }
+            }
             // Notify peer fd that close has happened, since that can unblock reads and writes.
             ecx.check_and_update_readiness(&peer_fd)?;
         }