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

@@ -201,7 +201,7 @@ pub(crate) use libc::{
     IPV6_MULTICAST_LOOP, IPV6_UNICAST_HOPS, IPV6_V6ONLY, IP_ADD_MEMBERSHIP, IP_DROP_MEMBERSHIP,
     IP_MULTICAST_IF, IP_MULTICAST_LOOP, IP_MULTICAST_TTL, IP_TTL, MSG_OOB, MSG_PEEK, SOL_SOCKET,
     SO_BROADCAST, SO_ERROR, SO_KEEPALIVE, SO_RCVBUF, SO_RCVTIMEO, SO_REUSEADDR, SO_SNDBUF,
-    SO_SNDTIMEO, SO_TYPE, TCP_NODELAY,
+    SO_SNDTIMEO, SO_TYPE, TCP_NODELAY
 };
 #[cfg(not(any(
     target_os = "dragonfly",
@@ -993,6 +993,18 @@ 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,