Add simple interface for busy_poll on Linux

Author: nan-mu

src/socket.rs

@@ -381,6 +381,21 @@ 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

@@ -993,6 +993,11 @@ 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,