Fix a bug in poll's handling of input pollfds

src/libos/src/net/io_multiplexing/poll_new/event_monitor.rs

@@ -200,17 +200,12 @@ impl EventMonitorBuilder {
     }
 
     pub fn add_file(&mut self, file: FileRef, events: IoEvents) {
-        let host_file_idx = if file.host_fd().is_some() {
+        if file.host_fd().is_some() {
-            Some(self.files_and_events.len())
+            let host_file_idx = self.files_and_events.len();
-        } else {
-            None
-        };
-
-        self.files_and_events.push((file, events));
-
-        if let Some(host_file_idx) = host_file_idx {
             self.host_file_idxes.push(host_file_idx);
         }
+
+        self.files_and_events.push((file, events));
     }
 
     fn init_ocall_pollfds(&mut self) {

src/libos/src/net/io_multiplexing/poll_new/mod.rs

@@ -13,6 +13,12 @@ mod event_monitor;
 pub fn do_poll_new(poll_fds: &[PollFd], mut timeout: Option<&mut Duration>) -> Result<usize> {
     debug!("poll: poll_fds: {:?}, timeout: {:?}", poll_fds, timeout);
 
+    // Always clear the revents fields first
+    for poll_fd in poll_fds {
+        poll_fd.revents.set(IoEvents::empty());
+    }
+
+    // Map poll_fds to FileRef's
     let thread = current!();
     let files: Vec<FileRef> = poll_fds
         .iter()