aya: Add bpf_map_delete_elem for XskMap

aya/src/maps/xdp/xsk_map.rs

@@ -7,7 +7,7 @@ use std::{
 
 use crate::{
     maps::{check_bounds, check_kv_size, MapData, MapError},
-    sys::{bpf_map_update_elem, SyscallError},
+    sys::{bpf_map_delete_elem, bpf_map_update_elem, SyscallError},
 };
 
 /// An array of AF_XDP sockets.
@@ -78,4 +78,23 @@ impl<T: BorrowMut<MapData>> XskMap<T> {
         )?;
         Ok(())
     }
+
+    /// Removes the `AF_XDP` socket stored at `index` from the map.
+    ///
+    /// Returns [`MapError::OutOfBounds`] if `index` is out of bounds, [`MapError::SyscallError`]
+    /// if `bpf_map_update_elem` fails.
+    pub fn clear_index(&mut self, index: u32) -> Result<(), MapError> {
+        let data = self.inner.borrow_mut();
+        check_bounds(data, index)?;
+        let fd = data.fd().as_fd();
+        bpf_map_delete_elem(fd, &index)
+            .map(|_| ())
+            .map_err(|(_, io_error)| {
+                SyscallError {
+                    call: "bpf_map_delete_elem",
+                    io_error,
+                }
+                .into()
+            })
+    }
 }

test/integration-test/src/tests/xdp.rs

@@ -29,7 +29,7 @@ fn af_xdp() {
     // So this needs to be page aligned. Pages are 4k on all mainstream architectures except for
     // Apple Silicon which uses 16k pages. So let's align on that for tests to run natively there.
     #[repr(C, align(16384))]
-    struct PacketMap(MaybeUninit<[u8; 4096]>);
+    struct PacketMap(MaybeUninit<[u8; 2 * 4096]>);
 
     // Safety: don't access alloc down the line.
     let mut alloc = Box::new(PacketMap(MaybeUninit::uninit()));
@@ -60,10 +60,12 @@ fn af_xdp() {
     socks.set(0, rx.as_raw_fd(), 0).unwrap();
 
     let frame = umem.frame(BufIdx(0)).unwrap();
+    let frame1 = umem.frame(BufIdx(1)).unwrap();
 
-    // Produce a frame to be filled by the kernel
-    let mut writer = fq_cq.fill(1);
+    // Produce two frames to be filled by the kernel
+    let mut writer = fq_cq.fill(2);
     writer.insert_once(frame.offset);
+    writer.insert_once(frame1.offset);
     writer.commit();
 
     let sock = UdpSocket::bind("127.0.0.1:0").unwrap();
@@ -84,6 +86,17 @@ fn af_xdp() {
     assert_eq!(&udp[0..2], port.to_be_bytes().as_slice()); // Source
     assert_eq!(&udp[2..4], 1777u16.to_be_bytes().as_slice()); // Dest
     assert_eq!(payload, b"hello AF_XDP");
+
+    assert_eq!(rx.available(), 1);
+    // Removes socket from map, no more packets will be redirected.
+    socks.clear_index(0).unwrap();
+    assert_eq!(rx.available(), 1);
+    sock.send_to(b"hello AF_XDP", "127.0.0.1:1777").unwrap();
+    assert_eq!(rx.available(), 1);
+    // Adds socket to map again, packets will be redirected again.
+    socks.set(0, rx.as_raw_fd(), 0).unwrap();
+    sock.send_to(b"hello AF_XDP", "127.0.0.1:1777").unwrap();
+    assert_eq!(rx.available(), 2);
 }
 
 #[test]