Added SO_PRIORITY socket option (#587)

Author: boris-n

src/socket.rs

@@ -996,6 +996,41 @@ impl Socket {
         }
     }
 
+    /// Get value for the `SO_PRIORITY` option on this socket.
+    ///
+    /// For more information about this option, see [`set_priority`].
+    ///
+    /// [`set_priority`]: Socket::set_priority
+    #[cfg(all(
+        feature = "all",
+        any(target_os = "linux", target_os = "android", target_os = "fuchsia")
+    ))]
+    pub fn priority(&self) -> io::Result<u32> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), sys::SOL_SOCKET, sys::SO_PRIORITY)
+                .map(|prio| prio as u32)
+        }
+    }
+
+    /// Set value for the `SO_PRIORITY` option on this socket.
+    ///
+    /// Packets with a higher priority may be processed earlier depending on the selected device
+    /// queueing discipline.
+    #[cfg(all(
+        feature = "all",
+        any(target_os = "linux", target_os = "android", target_os = "fuchsia")
+    ))]
+    pub fn set_priority(&self, priority: u32) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::SOL_SOCKET,
+                sys::SO_PRIORITY,
+                priority as c_int,
+            )
+        }
+    }
+
     /// Get value for the `SO_RCVBUF` option on this socket.
     ///
     /// For more information about this option, see [`set_recv_buffer_size`].

src/sys/unix.rs

@@ -206,6 +206,11 @@ pub(crate) use libc::SO_LINGER;
 pub(crate) use libc::SO_LINGER_SEC as SO_LINGER;
 #[cfg(any(target_os = "linux", target_os = "cygwin"))]
 pub(crate) use libc::SO_PASSCRED;
+#[cfg(all(
+    feature = "all",
+    any(target_os = "linux", target_os = "android", target_os = "fuchsia")
+))]
+pub(crate) use libc::SO_PRIORITY;
 pub(crate) use libc::{
     ip_mreq as IpMreq, linger, IPPROTO_IP, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, IPV6_MULTICAST_IF,
     IPV6_MULTICAST_LOOP, IPV6_UNICAST_HOPS, IPV6_V6ONLY, IP_ADD_MEMBERSHIP, IP_DROP_MEMBERSHIP,

tests/socket.rs

@@ -1811,3 +1811,16 @@ fn set_passcred() {
     socket.set_passcred(true).unwrap();
     assert!(socket.passcred().unwrap());
 }
+
+#[cfg(all(feature = "all", target_os = "linux"))]
+#[test]
+fn set_priority() {
+    let socket = Socket::new(Domain::UNIX, Type::DGRAM, None).unwrap();
+    assert!(socket.priority().unwrap() == 0);
+
+    // test priorities 6 .. 0; values above 6 require additional priviledges
+    for i in (0..=6).rev() {
+        socket.set_priority(i).unwrap();
+        assert!(socket.priority().unwrap() == i);
+    }
+}