simplify android impl, to only use netlink

Cargo.toml

@@ -14,9 +14,6 @@ license = "MIT"
 libc = "0.2"
 
 [target.'cfg(target_os = "android")'.dependencies]
-# DL Open
-dlopen = "0.1.8"
-once_cell = "1.17.1"
 # netlink
 netlink-packet-core = "0.5"
 netlink-packet-route = "0.15"

src/interface/android.rs

@@ -1,46 +1,7 @@
-use once_cell::sync::OnceCell;
+use crate::interface::Interface;
 
-pub fn get_libc_ifaddrs() -> Option<(
-    unsafe extern "C" fn(*mut *mut libc::ifaddrs) -> libc::c_int,
-    unsafe extern "C" fn(*mut libc::ifaddrs),
-)> {
-    match (get_getifaddrs(), get_freeifaddrs()) {
-        (Some(a), Some(b)) => Some((a, b)),
-        _ => None,
-    }
-}
-
-fn load_symbol<T>(sym: &'static str) -> Option<T> {
-    const LIB_NAME: &str = "libc.so";
-
-    println!("loading symbol: {} from {}", sym, LIB_NAME);
-    match dlopen::raw::Library::open(LIB_NAME) {
-        Ok(lib) => match unsafe { lib.symbol::<T>(sym) } {
-            Ok(val) => Some(val),
-            Err(err) => {
-                eprintln!("failed to load symbol {} from {}: {:?}", sym, LIB_NAME, err);
-                None
-            }
-        },
-        Err(err) => {
-            eprintln!("failed to load {}: {:?}", LIB_NAME, err);
-            None
-        }
-    }
-}
-
-fn get_getifaddrs() -> Option<unsafe extern "C" fn(*mut *mut libc::ifaddrs) -> libc::c_int> {
-    static INSTANCE: OnceCell<
-        Option<unsafe extern "C" fn(*mut *mut libc::ifaddrs) -> libc::c_int>,
-    > = OnceCell::new();
-
-    *INSTANCE.get_or_init(|| load_symbol("getifaddrs"))
-}
-
-fn get_freeifaddrs() -> Option<unsafe extern "C" fn(*mut libc::ifaddrs)> {
-    static INSTANCE: OnceCell<Option<unsafe extern "C" fn(*mut libc::ifaddrs)>> = OnceCell::new();
-
-    *INSTANCE.get_or_init(|| load_symbol("freeifaddrs"))
+pub fn unix_interfaces() -> Vec<Interface> {
+    netlink::unix_interfaces()
 }
 
 mod netlink {

src/interface/unix.rs

@@ -198,33 +198,17 @@ fn sockaddr_to_network_addr(sa: *const libc::sockaddr) -> (Option<MacAddr>, Opti
     }
 }
 
-#[cfg(not(target_os = "android"))]
-pub fn unix_interfaces() -> Vec<Interface> {
-    unix_interfaces_inner(libc::getifaddrs, libc::freeifaddrs)
-}
 
 #[cfg(target_os = "android")]
 pub fn unix_interfaces() -> Vec<Interface> {
-    // Android is complicated
-
-    // API 24+ contains the getifaddrs and freeifaddrs functions but the NDK doesn't
-    // expose those functions in ifaddrs.h when the minimum supported SDK is lower than 24
-    // and therefore we need to load them manually.
-    if let Some((getifaddrs, freeeifaddrs)) = android::get_libc_ifaddrs() {
-        return unix_interfaces_inner(getifaddrs, freeifaddrs);
+    super::android::unix_interfaces()
 }
 
-    // If API < 24 (or we can't load libc for some other reason), we fallback to using netlink
-    android::netlink::unix_interfaces()
-}
-
-pub fn unix_interfaces_inner(
-    getifaddrs: unsafe extern "C" fn(ifap: *mut *mut libc::ifaddrs) -> libc::c_int,
-    freeifaddrs: unsafe extern "C" fn(ifa: *mut libc::ifaddrs),
-) -> Vec<Interface> {
+#[cfg(not(target_os = "android"))]
+pub fn unix_interfaces() -> Vec<Interface> {
     let mut ifaces: Vec<Interface> = vec![];
     let mut addrs: MaybeUninit<*mut libc::ifaddrs> = MaybeUninit::uninit();
-    if unsafe { getifaddrs(addrs.as_mut_ptr()) } != 0 {
+    if unsafe { libc::getifaddrs(addrs.as_mut_ptr()) } != 0 {
         return ifaces;
     }
     let addrs = unsafe { addrs.assume_init() };
@@ -320,7 +304,7 @@ pub fn unix_interfaces_inner(
         addr = addr_ref.ifa_next;
     }
     unsafe {
-        freeifaddrs(addrs);
+        libc::freeifaddrs(addrs);
     }
     for iface in &mut ifaces {
         let name = CString::new(iface.name.as_bytes()).unwrap();