[libos] Remove uring udp socket redundant msg when returning error

src/libos/src/net/socket/uring/datagram/sender.rs

@@ -168,8 +168,7 @@ impl<A: Addr, R: Runtime> Sender<A, R> {
         let mut msg = DataMsg::new(buf_len);
         let total_copied = msg.copy_buf(bufs)?;
         msg.copy_control(control)?;
-
-        let msghdr_ptr = new_send_req(&mut msg, addr);
+        msg.build(addr);
 
         if !inner.msg_queue.push_msg(msg) {
             // Msg queue can not push this msg, mark the socket as non-writable
@@ -179,12 +178,12 @@ impl<A: Addr, R: Runtime> Sender<A, R> {
 
         // Since the send buffer is not empty, try to flush the buffer
         if inner.io_handle.is_none() {
-            self.do_send(&mut inner, msghdr_ptr);
+            self.do_send(&mut inner);
         }
         Ok(total_copied)
     }
 
-    fn do_send(self: &Arc<Self>, inner: &mut MutexGuard<Inner>, msghdr_ptr: *const libc::msghdr) {
+    fn do_send(self: &Arc<Self>, inner: &mut MutexGuard<Inner>) {
         debug_assert!(!inner.msg_queue.is_empty());
         debug_assert!(inner.io_handle.is_none());
         let sender = self.clone();
@@ -195,6 +194,7 @@ impl<A: Addr, R: Runtime> Sender<A, R> {
 
             // Release the handle to the async recv
             inner.io_handle.take();
+            inner.msg_queue.pop_msg();
 
             if retval < 0 {
                 // TODO: add PRI event if set SO_SELECT_ERR_QUEUE
@@ -207,12 +207,9 @@ impl<A: Addr, R: Runtime> Sender<A, R> {
             }
 
             // Need to handle normal case
-            inner.msg_queue.pop_msg();
             sender.common.pollee().add_events(Events::OUT);
             if !inner.msg_queue.is_empty() {
-                let msghdr_ptr = inner.msg_queue.first_msg_ptr();
-                debug_assert!(msghdr_ptr.is_some());
-                sender.do_send(&mut inner, msghdr_ptr.unwrap());
+                sender.do_send(&mut inner);
             } else if inner.is_shutdown == ShutdownStatus::PreShutdown {
                 // The buffer is empty and the write side is shutdown by the user.
                 // We can safely shutdown host file here.
@@ -224,38 +221,12 @@ impl<A: Addr, R: Runtime> Sender<A, R> {
         // Generate the async recv request
         let io_uring = self.common.io_uring();
         let host_fd = Fd(self.common.host_fd() as _);
+        let msghdr_ptr = inner.msg_queue.first_msg_ptr().unwrap();
         let handle = unsafe { io_uring.sendmsg(host_fd, msghdr_ptr, 0, complete_fn) };
         inner.io_handle.replace(handle);
     }
 }
 
-fn new_send_req<A: Addr>(dmsg: &mut DataMsg, addr: &A) -> *const libc::msghdr {
-    let iovec = libc::iovec {
-        iov_base: dmsg.send_buf.as_ptr() as _,
-        iov_len: dmsg.send_buf.len(),
-    };
-
-    let (control, controllen) = match &dmsg.control {
-        Some(control) => (control.as_mut_ptr() as *mut c_void, control.len()),
-        None => (ptr::null_mut(), 0),
-    };
-
-    dmsg.req.iovec = iovec;
-
-    dmsg.req.msg.msg_iov = &raw mut dmsg.req.iovec as _;
-    dmsg.req.msg.msg_iovlen = 1;
-
-    let (c_addr_storage, c_addr_len) = addr.to_c_storage();
-
-    dmsg.req.addr = c_addr_storage;
-    dmsg.req.msg.msg_name = &raw mut dmsg.req.addr as _;
-    dmsg.req.msg.msg_namelen = c_addr_len as _;
-    dmsg.req.msg.msg_control = control;
-    dmsg.req.msg.msg_controllen = controllen;
-
-    &mut dmsg.req.msg
-}
-
 pub struct Inner {
     io_handle: Option<IoHandle>,
     error: Option<Errno>,
@@ -396,6 +367,33 @@ impl DataMsg {
     fn len(&self) -> usize {
         self.send_buf.len()
     }
+
+    fn build<A: Addr>(&mut self, addr: &A) -> *const libc::msghdr {
+        let iovec = libc::iovec {
+            iov_base: self.send_buf.as_ptr() as _,
+            iov_len: self.send_buf.len(),
+        };
+
+        let (control, controllen) = match &self.control {
+            Some(control) => (control.as_mut_ptr() as *mut c_void, control.len()),
+            None => (ptr::null_mut(), 0),
+        };
+
+        self.req.iovec = iovec;
+
+        self.req.msg.msg_iov = &raw mut self.req.iovec as _;
+        self.req.msg.msg_iovlen = 1;
+
+        let (c_addr_storage, c_addr_len) = addr.to_c_storage();
+
+        self.req.addr = c_addr_storage;
+        self.req.msg.msg_name = &raw mut self.req.addr as _;
+        self.req.msg.msg_namelen = c_addr_len as _;
+        self.req.msg.msg_control = control;
+        self.req.msg.msg_controllen = controllen;
+
+        &mut self.req.msg
+    }
 }
 
 #[derive(Debug, PartialEq)]