feat: use netlink as a fallback on android

Cargo.toml

@@ -14,8 +14,13 @@ 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"
+netlink-sys = "0.8"
 
 [target.'cfg(windows)'.dependencies]
 memalloc = "0.1.0"

src/interface/android.rs

@@ -1,5 +1,15 @@
 use once_cell::sync::OnceCell;
 
+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";
 
@@ -33,32 +43,191 @@ fn get_freeifaddrs() -> Option<unsafe extern "C" fn(*mut libc::ifaddrs)> {
     *INSTANCE.get_or_init(|| load_symbol("freeifaddrs"))
 }
 
-pub unsafe fn getifaddrs(ifap: *mut *mut libc::ifaddrs) -> libc::c_int {
-    // Android is complicated
+mod netlink {
+    //! Netlink based getifaddrs.
+    //!
+    //! Based on the logic found in https://git.musl-libc.org/cgit/musl/tree/src/network/getifaddrs.c
+
+    use netlink_packet_core::{
+        NetlinkHeader, NetlinkMessage, NetlinkPayload, NLM_F_DUMP, NLM_F_REQUEST,
+    };
+    use netlink_packet_route::{
+        rtnl::address::nlas::Nla as AddressNla, rtnl::link::nlas::Nla as LinkNla, AddressMessage,
+        LinkMessage, RtnlMessage,
+    };
+    use netlink_sys::{protocols::NETLINK_ROUTE, Socket};
+    use std::net::{Ipv4Addr, Ipv6Addr};
+
+    use crate::interface::{Interface, InterfaceType, Ipv4Net, Ipv6Net, MacAddr};
+
+    pub fn unix_interfaces() -> Vec<Interface> {
+        let socket = Socket::new(NETLINK_ROUTE).unwrap();
 
-    // 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(dyn_getifaddrs) = get_getifaddrs() {
-        return dyn_getifaddrs(ifap);
+        let mut ifaces = Vec::new();
+        enumerate_netlink(
+            &socket,
+            RtnlMessage::GetLink(LinkMessage::default()),
+            &mut ifaces,
+        );
+        enumerate_netlink(
+            &socket,
+            RtnlMessage::GetAddress(AddressMessage::default()),
+            &mut ifaces,
+        );
+
+        ifaces
     }
 
-    // If API < 24 (or we can't load libc for some other reason), we fallback to using netlink
-    netlink_getifaddrs(ifap)
-}
+    fn enumerate_netlink(socket: &Socket, msg: RtnlMessage, ifaces: &mut Vec<Interface>) {
+        let mut packet = NetlinkMessage::new(NetlinkHeader::default(), NetlinkPayload::from(msg));
+        packet.header.flags = NLM_F_DUMP | NLM_F_REQUEST;
+        packet.header.sequence_number = 1;
+        packet.finalize();
+
+        let mut buf = vec![0; packet.header.length as usize];
+
+        // TODO: gracefully handle error
+        assert!(buf.len() == packet.buffer_len());
+        packet.serialize(&mut buf[..]);
+
+        socket.send(&buf[..], 0).unwrap();
 
-pub unsafe fn freeifaddrs(ifa: *mut libc::ifaddrs) {
-    if let Some(dyn_freeifaddrs) = get_freeifaddrs() {
-        return dyn_freeifaddrs(ifa);
+        let mut receive_buffer = vec![0; 4096];
+        let mut offset = 0;
+
+        loop {
+            let size = socket.recv(&mut &mut receive_buffer[..], 0).unwrap();
+
+            loop {
+                let bytes = &receive_buffer[offset..];
+                let rx_packet: NetlinkMessage<RtnlMessage> =
+                    NetlinkMessage::deserialize(bytes).unwrap();
+
+                match rx_packet.payload {
+                    NetlinkPayload::Done => {
+                        return;
                     }
+                    NetlinkPayload::Error(err) => {
+                        eprintln!("Error: {:?}", err);
+                        return;
+                    }
+                    NetlinkPayload::InnerMessage(msg) => {
+                        match msg {
+                            RtnlMessage::NewLink(link_msg) => {
+                                let mut interface: Interface = Interface {
+                                    index: link_msg.header.index,
+                                    name: String::new(),
+                                    friendly_name: None,
+                                    description: None,
+                                    if_type: InterfaceType::try_from(
+                                        link_msg.header.link_layer_type as u32,
+                                    )
+                                    .unwrap_or(InterfaceType::Unknown),
+                                    mac_addr: None,
+                                    ipv4: Vec::new(),
+                                    ipv6: Vec::new(),
+                                    flags: link_msg.header.flags,
+                                    transmit_speed: None,
+                                    receive_speed: None,
+                                    gateway: None,
+                                };
 
-    netlink_freeifaddrs(ifa)
-}
+                                for nla in link_msg.nlas {
+                                    match nla {
+                                        LinkNla::IfName(name) => {
+                                            interface.name = name;
+                                        }
+                                        LinkNla::Address(addr) => {
+                                            match addr.len() {
+                                                6 => {
+                                                    interface.mac_addr = Some(MacAddr::new(
+                                                        addr.try_into().unwrap(),
+                                                    ));
+                                                }
+                                                4 => {
+                                                    let ip = Ipv4Addr::from(
+                                                        <[u8; 4]>::try_from(addr).unwrap(),
+                                                    );
+                                                    interface.ipv4.push(Ipv4Net::new_with_netmask(
+                                                        ip,
+                                                        Ipv4Addr::UNSPECIFIED,
+                                                    ));
+                                                }
+                                                _ => {
+                                                    // unclear what these would be
+                                                }
+                                            }
+                                        }
+                                        _ => {}
+                                    }
+                                }
+                                ifaces.push(interface);
+                            }
+                            RtnlMessage::NewAddress(addr_msg) => {
+                                println!("NewAddress: {:?}", addr_msg);
+                                if let Some(interface) =
+                                    ifaces.iter_mut().find(|i| i.index == addr_msg.header.index)
+                                {
+                                    for nla in addr_msg.nlas {
+                                        match nla {
+                                            AddressNla::Address(addr) => match addr.len() {
+                                                4 => {
+                                                    let ip = Ipv4Addr::from(
+                                                        <[u8; 4]>::try_from(addr).unwrap(),
+                                                    );
+                                                    interface.ipv4.push(Ipv4Net::new(
+                                                        ip,
+                                                        addr_msg.header.prefix_len,
+                                                    ));
+                                                }
+                                                16 => {
+                                                    let ip = Ipv6Addr::from(
+                                                        <[u8; 16]>::try_from(addr).unwrap(),
+                                                    );
+                                                    interface.ipv6.push(Ipv6Net::new(
+                                                        ip,
+                                                        addr_msg.header.prefix_len,
+                                                    ));
+                                                }
+                                                _ => {
+                                                    // what else?
+                                                }
+                                            },
+                                            _ => {}
+                                        }
+                                    }
+                                } else {
+                                    eprintln!(
+                                        "found unknown interface with index: {}",
+                                        addr_msg.header.index
+                                    );
+                                }
+                            }
+                            _ => {
+                                // not expecting other messages
+                            }
+                        }
+                    }
+                    _ => {}
+                }
+                offset += rx_packet.header.length as usize;
+                if offset == size || rx_packet.header.length == 0 {
+                    offset = 0;
+                    break;
+                }
+            }
+        }
+    }
 
-unsafe fn netlink_getifaddrs(ifap: *mut *mut libc::ifaddrs) -> libc::c_int {
-    todo!()
-}
+    #[cfg(test)]
+    mod tests {
+        use super::*;
 
-unsafe fn netlink_freeifaddrs(ifa: *mut libc::ifaddrs) {
-    todo!()
+        #[test]
+        fn test_netlink_ifaddrs() {
+            let interfaces = unix_interfaces();
+            dbg!(&interfaces);
+            assert!(!interfaces.is_empty());
+        }
+    }
 }

src/interface/unix.rs

@@ -1,10 +1,10 @@
 use super::Interface;
 use super::MacAddr;
 use crate::gateway;
+use crate::interface::InterfaceType;
 use crate::ip::{Ipv4Net, Ipv6Net};
 use crate::sys;
 
-use crate::interface::InterfaceType;
 use libc;
 use std::ffi::{CStr, CString};
 use std::mem::{self, MaybeUninit};
@@ -12,9 +12,6 @@ use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
 use std::os::raw::c_char;
 use std::str::from_utf8_unchecked;
 
-#[cfg(target_os = "android")]
-use super::android::{freeifaddrs, getifaddrs};
-
 #[cfg(any(target_os = "openbsd", target_os = "freebsd", target_os = "netbsd"))]
 pub fn interfaces() -> Vec<Interface> {
     let mut interfaces: Vec<Interface> = unix_interfaces();
@@ -128,7 +125,9 @@ pub fn interfaces() -> Vec<Interface> {
 }
 
 #[cfg(any(target_os = "linux", target_os = "android"))]
-fn sockaddr_to_network_addr(sa: *const libc::sockaddr) -> (Option<MacAddr>, Option<IpAddr>) {
+pub(super) fn sockaddr_to_network_addr(
+    sa: *const libc::sockaddr,
+) -> (Option<MacAddr>, Option<IpAddr>) {
     use std::net::SocketAddr;
 
     unsafe {
@@ -150,7 +149,7 @@ fn sockaddr_to_network_addr(sa: *const libc::sockaddr) -> (Option<MacAddr>, Opti
             let addr =
                 sys::sockaddr_to_addr(mem::transmute(sa), mem::size_of::<libc::sockaddr_storage>());
 
-            match addr {
+            match dbg!(addr) {
                 Ok(SocketAddr::V4(sa)) => (None, Some(IpAddr::V4(*sa.ip()))),
                 Ok(SocketAddr::V6(sa)) => (None, Some(IpAddr::V6(*sa.ip()))),
                 Err(_) => (None, None),
@@ -199,7 +198,30 @@ 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);
+    }
+
+    // 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> {
     let mut ifaces: Vec<Interface> = vec![];
     let mut addrs: MaybeUninit<*mut libc::ifaddrs> = MaybeUninit::uninit();
     if unsafe { getifaddrs(addrs.as_mut_ptr()) } != 0 {
@@ -212,6 +234,7 @@ pub fn unix_interfaces() -> Vec<Interface> {
         let c_str = addr_ref.ifa_name as *const c_char;
         let bytes = unsafe { CStr::from_ptr(c_str).to_bytes() };
         let name = unsafe { from_utf8_unchecked(bytes).to_owned() };
+
         let (mac, ip) = sockaddr_to_network_addr(addr_ref.ifa_addr as *const libc::sockaddr);
         let (_, netmask) = sockaddr_to_network_addr(addr_ref.ifa_netmask as *const libc::sockaddr);
         let mut ini_ipv4: Vec<Ipv4Net> = vec![];
@@ -308,17 +331,6 @@ pub fn unix_interfaces() -> Vec<Interface> {
     ifaces
 }
 
-#[cfg(not(target_os = "android"))]
-unsafe fn getifaddrs(ifap: *mut *mut libc::ifaddrs) -> libc::c_int {
-    // Not android, everything is easy
-    libc::getifaddrs(ifap)
-}
-
-#[cfg(not(target_os = "android"))]
-unsafe fn freeifaddrs(ifa: *mut libc::ifaddrs) {
-    libc::freeifaddrs(ifa);
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;