Refactor SO_BUSY_POLL part follow the review comments

  * Change the documentation comment of `set_busy_poll`
  * Move setter into unix under `all` feature
  * Add a getter

Author: nan-mu

src/socket.rs

@@ -381,21 +381,6 @@ impl Socket {
         sys::set_nonblocking(self.as_raw(), nonblocking)
     }
 
-    /// Sets the busy polling timeout in microseconds for blocking socket operations.
-    ///
-    /// When there is no data available, the socket will busy poll for the specified
-    /// duration (in microseconds) before falling back to blocking behavior.
-    ///
-    /// # Notes
-    ///
-    /// - Requires `CAP_NET_ADMIN` capability to increase the value
-    /// - Default value is controlled by `/proc/sys/net/core/busy_read`
-    /// - Available since Linux 3.11
-    #[cfg(target_os = "linux")]
-    pub fn set_busy_poll(&self, busy_poll: u16) -> io::Result<()> {
-        sys::set_busy_poll(self.as_raw(), busy_poll)
-    }
-
     /// Shuts down the read, write, or both halves of this connection.
     ///
     /// This function will cause all pending and future I/O on the specified

src/sys/unix.rs

@@ -993,11 +993,6 @@ pub(crate) fn set_nonblocking(fd: RawSocket, nonblocking: bool) -> io::Result<()
     }
 }
 
-#[cfg(target_os = "linux")]
-pub(crate) fn set_busy_poll(fd: RawSocket, busy_poll: u16) -> io::Result<()> {
-    unsafe { setsockopt(fd, libc::SOL_SOCKET, libc::SO_BUSY_POLL, busy_poll as c_int) }
-}
-
 pub(crate) fn shutdown(fd: RawSocket, how: Shutdown) -> io::Result<()> {
     let how = match how {
         Shutdown::Write => libc::SHUT_WR,
@@ -2818,6 +2813,29 @@ impl crate::Socket {
             )
         }
     }
+
+    /// Get the value for the `SO_BUSY_POLL` option on this socket.
+    ///
+    /// On Linux this function requires the `CAP_NET_ADMIN` capability.
+    #[cfg(all(feature = "all", target_os = "linux"))]
+    pub fn busy_poll(&self) -> io::Result<u32> {
+        unsafe { getsockopt(self.as_raw(), libc::SOL_SOCKET, libc::SO_BUSY_POLL) }
+    }
+
+    /// Set the value for the `SO_BUSY_POLL` option on this socket.
+    ///
+    /// On Linux this function requires the `CAP_NET_ADMIN` capability.
+    #[cfg(all(feature = "all", target_os = "linux"))]
+    pub fn set_busy_poll(&self, busy_poll: u32) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                libc::SOL_SOCKET,
+                libc::SO_BUSY_POLL,
+                busy_poll as c_int,
+            )
+        }
+    }
 }
 
 /// Berkeley Packet Filter (BPF).