Add SockFilter

A wrapper around libc::sock_filter, so we don't use any libc types in
our API.

Author: Thomasdezeeuw

src/sys/unix.rs

@@ -2459,16 +2459,17 @@ impl crate::Socket {
         }
     }
 
-    /// Attach Berkeley Packet Filter(BPF) on this socket.
+    /// Attach Berkeley Packet Filter (BPF) on this socket.
     ///
     /// BPF allows a user-space program to attach a filter onto any socket
     /// and allow or disallow certain types of data to come through the socket.
     ///
     /// For more information about this option, see [filter](https://www.kernel.org/doc/html/v5.12/networking/filter.html)
     #[cfg(all(feature = "all", any(target_os = "linux", target_os = "android")))]
-    pub fn attach_filter(&self, filters: &[libc::sock_filter]) -> io::Result<()> {
+    pub fn attach_filter(&self, filters: &[SockFilter]) -> io::Result<()> {
         let prog = libc::sock_fprog {
             len: filters.len() as u16,
+            // SAFETY: this is safe due to `repr(transparent)`.
             filter: filters.as_ptr() as *mut _,
         };
 
@@ -2814,6 +2815,23 @@ impl crate::Socket {
     }
 }
 
+/// Berkeley Packet Filter (BPF).
+///
+/// See [`Socket::attach_filter[
+#[cfg(all(feature = "all", any(target_os = "linux", target_os = "android")))]
+#[repr(transparent)]
+pub struct SockFilter {
+    filter: libc::sock_filter,
+}
+
+#[cfg(all(feature = "all", any(target_os = "linux", target_os = "android")))]
+impl SockFilter {
+    /// Create new `SockFilter`.
+    pub fn new(code: u16, jt: u8, jf: u8, k: u32) -> SockFilter {
+        SockFilter { code, jt, jf, k }
+    }
+}
+
 /// See [`Socket::dccp_available_ccids`].
 #[cfg(all(feature = "all", target_os = "linux"))]
 #[derive(Debug)]