bpf/devmap: don't expose `bpf_devmap_value`

Use our own type that:
- is stable as not from bindgen
- does not have an union inside

bpf/aya-bpf/src/maps/xdp/dev_map.rs

@@ -104,13 +104,18 @@ impl DevMap {
     /// // redirect to ifindex
     /// ```
     #[inline(always)]
-    pub fn get(&self, index: u32) -> Option<bpf_devmap_val> {
+    pub fn get(&self, index: u32) -> Option<DevMapValue> {
         unsafe {
             let value = bpf_map_lookup_elem(
                 self.def.get() as *mut _,
                 &index as *const _ as *const c_void,
             );
-            NonNull::new(value as *mut bpf_devmap_val).map(|p| *p.as_ref())
+            NonNull::new(value as *mut bpf_devmap_val).map(|p| DevMapValue {
+                ifindex: p.as_ref().ifindex,
+                // SAFETY: map writes use fd, map reads use id.
+                // https://elixir.bootlin.com/linux/v6.2/source/include/uapi/linux/bpf.h#L6136
+                prog_id: p.as_ref().bpf_prog.id,
+            })
         }
     }
 
@@ -142,3 +147,9 @@ impl DevMap {
         }
     }
 }
+
+#[derive(Clone, Copy)]
+pub struct DevMapValue {
+    pub ifindex: u32,
+    pub prog_id: u32,
+}

bpf/aya-bpf/src/maps/xdp/dev_map_hash.rs

@@ -9,6 +9,8 @@ use crate::{
     maps::PinningType,
 };
 
+use super::dev_map::DevMapValue;
+
 /// A map of network devices.
 ///
 /// XDP programs can use this map to redirect packets to other network devices. It is similar to
@@ -106,11 +108,16 @@ impl DevMapHash {
     /// // redirect to ifindex
     /// ```
     #[inline(always)]
-    pub fn get(&self, key: u32) -> Option<bpf_devmap_val> {
+    pub fn get(&self, key: u32) -> Option<DevMapValue> {
         unsafe {
             let value =
                 bpf_map_lookup_elem(self.def.get() as *mut _, &key as *const _ as *const c_void);
-            NonNull::new(value as *mut bpf_devmap_val).map(|p| *p.as_ref())
+            NonNull::new(value as *mut bpf_devmap_val).map(|p| DevMapValue {
+                ifindex: p.as_ref().ifindex,
+                // SAFETY: map writes use fd, map reads use id.
+                // https://elixir.bootlin.com/linux/v6.2/source/include/uapi/linux/bpf.h#L6136
+                prog_id: p.as_ref().bpf_prog.id,
+            })
         }
     }