network: implement icmp nat support

Cargo.toml

@@ -53,7 +53,6 @@ udp-stream = "0.0.11"
 smoltcp = "0.11.0"
 etherparse = "0.14.2"
 async-trait = "0.1.77"
-async-ping = "0.2.1"
 
 [workspace.dependencies.uuid]
 version = "1.6.1"
@@ -74,7 +73,3 @@ features = ["macros", "rt", "rt-multi-thread"]
 [workspace.dependencies.serde]
 version = "1.0.196"
 features = ["derive"]
-
-[workspace.dependencies.icmp-client]
-version = "0.2"
-features = ["impl_tokio"]

network/Cargo.toml

@@ -18,8 +18,6 @@ udp-stream = { workspace = true }
 smoltcp = { workspace = true }
 etherparse = { workspace = true }
 async-trait = { workspace = true }
-async-ping = { workspace = true }
-icmp-client = { workspace = true }
 
 [dependencies.advmac]
 path = "../libs/advmac"
@@ -30,3 +28,7 @@ path = "src/lib.rs"
 [[bin]]
 name = "hyphanet"
 path = "bin/network.rs"
+
+[[example]]
+name = "ping"
+path = "examples/ping.rs"

network/examples/ping.rs

@@ -0,0 +1,21 @@
+use std::{net::Ipv6Addr, str::FromStr, time::Duration};
+
+use anyhow::Result;
+use hyphanet::icmp::{IcmpClient, IcmpProtocol};
+
+#[tokio::main]
+async fn main() -> Result<()> {
+    let client = IcmpClient::new(IcmpProtocol::Icmp6)?;
+    let payload: [u8; 4] = [12u8, 14u8, 16u8, 32u8];
+    let result = client
+        .ping6(
+            Ipv6Addr::from_str("2606:4700:4700::1111")?,
+            0,
+            1,
+            &payload,
+            Duration::from_secs(10),
+        )
+        .await?;
+    println!("reply: {:?}", result);
+    Ok(())
+}

network/src/backend.rs

@@ -1,7 +1,7 @@
 use crate::chandev::ChannelDevice;
 use crate::nat::NatRouter;
 use crate::proxynat::ProxyNatHandlerFactory;
-use crate::raw_socket::AsyncRawSocket;
+use crate::raw_socket::{AsyncRawSocket, RawSocketProtocol};
 use advmac::MacAddr6;
 use anyhow::{anyhow, Result};
 use futures::TryStreamExt;
@@ -28,6 +28,7 @@ enum NetworkStackSelect<'a> {
 }
 
 struct NetworkStack<'a> {
+    mtu: usize,
     tx: Receiver<Vec<u8>>,
     kdev: AsyncRawSocket,
     udev: ChannelDevice,
@@ -101,7 +102,7 @@ impl NetworkBackend {
 
     pub async fn run(&self) -> Result<()> {
         let mut stack = self.create_network_stack()?;
-        let mut buffer = vec![0u8; 1500];
+        let mut buffer = vec![0u8; stack.mtu];
         loop {
             stack.poll(&mut buffer).await?;
         }
@@ -112,9 +113,11 @@ impl NetworkBackend {
         let address = IpCidr::from_str(&self.network)
             .map_err(|_| anyhow!("failed to parse cidr: {}", self.network))?;
         let addresses: Vec<IpCidr> = vec![address];
-        let kdev = AsyncRawSocket::bind(&self.interface)?;
+        let mut kdev =
+            AsyncRawSocket::bound_to_interface(&self.interface, RawSocketProtocol::Ethernet)?;
+        let mtu = kdev.mtu_of_interface(&self.interface)?;
         let (tx_sender, tx_receiver) = channel::<Vec<u8>>(4);
-        let mut udev = ChannelDevice::new(1500, tx_sender.clone());
+        let mut udev = ChannelDevice::new(mtu, tx_sender.clone());
         let mac = MacAddr6::random();
         let mac = smoltcp::wire::EthernetAddress(mac.to_array());
         let nat = NatRouter::new(proxy, mac, addresses.clone(), tx_sender.clone());
@@ -128,6 +131,7 @@ impl NetworkBackend {
         });
         let sockets = SocketSet::new(vec![]);
         Ok(NetworkStack {
+            mtu,
             tx: tx_receiver,
             kdev,
             udev,

network/src/icmp.rs

@@ -0,0 +1,245 @@
+use crate::raw_socket::{RawSocketHandle, RawSocketProtocol};
+use anyhow::{anyhow, Result};
+use etherparse::{
+    IcmpEchoHeader, Icmpv4Header, Icmpv4Slice, Icmpv4Type, Icmpv6Header, Icmpv6Slice, Icmpv6Type,
+    IpNumber, NetSlice, SlicedPacket,
+};
+use log::warn;
+use std::{
+    collections::HashMap,
+    net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr, SocketAddrV4, SocketAddrV6},
+    os::fd::{FromRawFd, IntoRawFd},
+    sync::Arc,
+    time::Duration,
+};
+use tokio::{
+    net::UdpSocket,
+    sync::{oneshot, Mutex},
+    task::JoinHandle,
+    time::timeout,
+};
+
+#[derive(Debug)]
+pub enum IcmpProtocol {
+    Icmp4,
+    Icmp6,
+}
+
+impl IcmpProtocol {
+    pub fn to_socket_protocol(&self) -> RawSocketProtocol {
+        match self {
+            IcmpProtocol::Icmp4 => RawSocketProtocol::Icmpv4,
+            IcmpProtocol::Icmp6 => RawSocketProtocol::Icmpv6,
+        }
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+struct IcmpHandlerToken(IpAddr, Option<u16>, u16);
+
+#[derive(Debug)]
+pub enum IcmpReply {
+    Icmp4 {
+        header: Icmpv4Header,
+        echo: IcmpEchoHeader,
+        payload: Vec<u8>,
+    },
+
+    Icmp6 {
+        header: Icmpv6Header,
+        echo: IcmpEchoHeader,
+        payload: Vec<u8>,
+    },
+}
+
+type IcmpHandlerMap = Arc<Mutex<HashMap<IcmpHandlerToken, oneshot::Sender<IcmpReply>>>>;
+pub struct IcmpClient {
+    socket: Arc<UdpSocket>,
+    handlers: IcmpHandlerMap,
+    task: Arc<JoinHandle<Result<()>>>,
+}
+
+impl IcmpClient {
+    pub fn new(protocol: IcmpProtocol) -> Result<IcmpClient> {
+        let handle = RawSocketHandle::new(protocol.to_socket_protocol())?;
+        let socket = unsafe { std::net::UdpSocket::from_raw_fd(handle.into_raw_fd()) };
+        let socket: Arc<UdpSocket> = Arc::new(socket.try_into()?);
+        let handlers = Arc::new(Mutex::new(HashMap::new()));
+        let task = Arc::new(tokio::task::spawn(IcmpClient::process(
+            protocol,
+            socket.clone(),
+            handlers.clone(),
+        )));
+        Ok(IcmpClient {
+            socket,
+            handlers,
+            task,
+        })
+    }
+
+    async fn process(
+        protocol: IcmpProtocol,
+        socket: Arc<UdpSocket>,
+        handlers: IcmpHandlerMap,
+    ) -> Result<()> {
+        let mut buffer = vec![0u8; 2048];
+        loop {
+            let (size, addr) = socket.recv_from(&mut buffer).await?;
+            let packet = &buffer[0..size];
+
+            let (token, reply) = match protocol {
+                IcmpProtocol::Icmp4 => {
+                    let sliced = match SlicedPacket::from_ip(packet) {
+                        Ok(sliced) => sliced,
+                        Err(error) => {
+                            warn!("received icmp packet but failed to parse it: {}", error);
+                            continue;
+                        }
+                    };
+
+                    let Some(NetSlice::Ipv4(ipv4)) = sliced.net else {
+                        continue;
+                    };
+
+                    if ipv4.header().protocol() != IpNumber::ICMP {
+                        continue;
+                    }
+
+                    let Ok(icmpv4) = Icmpv4Slice::from_slice(ipv4.payload().payload) else {
+                        continue;
+                    };
+
+                    let Icmpv4Type::EchoReply(echo) = icmpv4.header().icmp_type else {
+                        continue;
+                    };
+
+                    let token = IcmpHandlerToken(
+                        IpAddr::V4(ipv4.header().source_addr()),
+                        Some(echo.id),
+                        echo.seq,
+                    );
+                    let reply = IcmpReply::Icmp4 {
+                        header: icmpv4.header(),
+                        echo,
+                        payload: icmpv4.payload().to_vec(),
+                    };
+                    (token, reply)
+                }
+
+                IcmpProtocol::Icmp6 => {
+                    let Ok(icmpv6) = Icmpv6Slice::from_slice(packet) else {
+                        continue;
+                    };
+
+                    let Icmpv6Type::EchoReply(echo) = icmpv6.header().icmp_type else {
+                        continue;
+                    };
+
+                    let SocketAddr::V6(addr) = addr else {
+                        continue;
+                    };
+
+                    let token = IcmpHandlerToken(IpAddr::V6(*addr.ip()), Some(echo.id), echo.seq);
+
+                    let reply = IcmpReply::Icmp6 {
+                        header: icmpv6.header(),
+                        echo,
+                        payload: icmpv6.payload().to_vec(),
+                    };
+                    (token, reply)
+                }
+            };
+
+            if let Some(sender) = handlers.lock().await.remove(&token) {
+                let _ = sender.send(reply);
+            }
+        }
+    }
+
+    async fn add_handler(&self, token: IcmpHandlerToken) -> Result<oneshot::Receiver<IcmpReply>> {
+        let (tx, rx) = oneshot::channel();
+        if self
+            .handlers
+            .lock()
+            .await
+            .insert(token.clone(), tx)
+            .is_some()
+        {
+            return Err(anyhow!("duplicate icmp request: {:?}", token));
+        }
+        Ok(rx)
+    }
+
+    async fn remove_handler(&self, token: IcmpHandlerToken) -> Result<()> {
+        self.handlers.lock().await.remove(&token);
+        Ok(())
+    }
+
+    pub async fn ping4(
+        &self,
+        addr: Ipv4Addr,
+        id: u16,
+        seq: u16,
+        payload: &[u8],
+        deadline: Duration,
+    ) -> Result<Option<IcmpReply>> {
+        let token = IcmpHandlerToken(IpAddr::V4(addr), Some(id), seq);
+        let rx = self.add_handler(token.clone()).await?;
+
+        let echo = IcmpEchoHeader { id, seq };
+        let header = Icmpv4Header::new(Icmpv4Type::EchoRequest(echo));
+        let mut buffer: Vec<u8> = Vec::new();
+        header.write(&mut buffer)?;
+        buffer.extend_from_slice(payload);
+        self.socket
+            .send_to(&buffer, SocketAddr::V4(SocketAddrV4::new(addr, 0)))
+            .await?;
+
+        let result = timeout(deadline, rx).await;
+        self.remove_handler(token).await?;
+        let reply = match result {
+            Ok(Ok(packet)) => Some(packet),
+            Ok(Err(err)) => return Err(anyhow!("failed to wait for icmp packet: {}", err)),
+            Err(_) => None,
+        };
+        Ok(reply)
+    }
+
+    pub async fn ping6(
+        &self,
+        addr: Ipv6Addr,
+        id: u16,
+        seq: u16,
+        payload: &[u8],
+        deadline: Duration,
+    ) -> Result<Option<IcmpReply>> {
+        let token = IcmpHandlerToken(IpAddr::V6(addr), Some(id), seq);
+        let rx = self.add_handler(token.clone()).await?;
+
+        let echo = IcmpEchoHeader { id, seq };
+        let header = Icmpv6Header::new(Icmpv6Type::EchoRequest(echo));
+        let mut buffer: Vec<u8> = Vec::new();
+        header.write(&mut buffer)?;
+        buffer.extend_from_slice(payload);
+        self.socket
+            .send_to(&buffer, SocketAddr::V6(SocketAddrV6::new(addr, 0, 0, 0)))
+            .await?;
+
+        let result = timeout(deadline, rx).await;
+        self.remove_handler(token).await?;
+        let reply = match result {
+            Ok(Ok(packet)) => Some(packet),
+            Ok(Err(err)) => return Err(anyhow!("failed to wait for icmp packet: {}", err)),
+            Err(_) => None,
+        };
+        Ok(reply)
+    }
+}
+
+impl Drop for IcmpClient {
+    fn drop(&mut self) {
+        if Arc::strong_count(&self.task) <= 1 {
+            self.task.abort();
+        }
+    }
+}

network/src/lib.rs

@@ -8,11 +8,12 @@ use tokio::time::sleep;
 
 use crate::backend::NetworkBackend;
 
-mod backend;
-mod chandev;
-mod nat;
-mod proxynat;
-mod raw_socket;
+pub mod backend;
+pub mod chandev;
+pub mod icmp;
+pub mod nat;
+pub mod proxynat;
+pub mod raw_socket;
 
 pub struct NetworkService {
     pub network: String,

network/src/nat.rs

@@ -69,6 +69,12 @@ pub struct NatTable {
     inner: HashMap<NatKey, Box<dyn NatHandler>>,
 }
 
+impl Default for NatTable {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl NatTable {
     pub fn new() -> Self {
         Self {

network/src/proxynat/icmp.rs

@@ -1,13 +1,11 @@
-use std::time::Duration;
+use std::{net::IpAddr, time::Duration};
 
 use anyhow::{anyhow, Result};
-use async_ping::{
-    icmp_client::Config,
-    icmp_packet::{Icmp, Icmpv4},
-    PingClient,
-};
 use async_trait::async_trait;
-use etherparse::{Icmpv4Header, Icmpv4Type, IpNumber, PacketBuilder, SlicedPacket};
+use etherparse::{
+    Icmpv4Header, Icmpv4Type, Icmpv6Header, Icmpv6Type, IpNumber, NetSlice, PacketBuilder,
+    SlicedPacket,
+};
 use log::{debug, warn};
 use smoltcp::wire::IpAddress;
 use tokio::{
@@ -15,7 +13,10 @@ use tokio::{
     sync::mpsc::{Receiver, Sender},
 };
 
-use crate::nat::{NatHandler, NatKey};
+use crate::{
+    icmp::{IcmpClient, IcmpProtocol, IcmpReply},
+    nat::{NatHandler, NatKey},
+};
 
 const ICMP_PING_TIMEOUT_SECS: u64 = 20;
 const ICMP_TIMEOUT_SECS: u64 = 30;
@@ -49,15 +50,7 @@ impl ProxyIcmpHandler {
         tx_sender: Sender<Vec<u8>>,
         reclaim_sender: Sender<NatKey>,
     ) -> Result<()> {
-        let client = PingClient::<icmp_client::impl_tokio::Client>::new(Some(Config::new()), None)?;
-
-        {
-            let client = client.clone();
-            tokio::spawn(async move {
-                client.handle_v4_recv_from().await;
-            });
-        }
-
+        let client = IcmpClient::new(IcmpProtocol::Icmp4)?;
         let key = self.key;
         tokio::spawn(async move {
             if let Err(error) =
@@ -70,7 +63,7 @@ impl ProxyIcmpHandler {
     }
 
     async fn process(
-        client: PingClient<icmp_client::impl_tokio::Client>,
+        client: IcmpClient,
         key: NatKey,
         mut rx_receiver: Receiver<Vec<u8>>,
         tx_sender: Sender<Vec<u8>>,
@@ -94,28 +87,36 @@ impl ProxyIcmpHandler {
                         continue;
                     };
 
-                    let Some(ip) = net.ip_payload_ref() else {
-                        continue;
-                    };
-
-                    if ip.ip_number != IpNumber::ICMP {
+                    match net {
+                        NetSlice::Ipv4(ipv4) => {
+                            if ipv4.header().protocol() != IpNumber::ICMP {
                                 continue;
                             }
 
-                    let (header, payload) = Icmpv4Header::from_slice(ip.payload)?;
+                            let (header, payload) =
+                                Icmpv4Header::from_slice(ipv4.payload().payload)?;
                             if let Icmpv4Type::EchoRequest(echo) = header.icmp_type {
-                        let result = client
-                            .ping(
-                                key.external_ip.addr.into(),
-                                Some(echo.id),
-                                Some(echo.seq),
+                                let IpAddr::V4(external_ipv4) = key.external_ip.addr.into() else {
+                                    continue;
+                                };
+
+                                let Some(IcmpReply::Icmp4 {
+                                    header: _,
+                                    echo,
+                                    payload,
+                                }) = client
+                                    .ping4(
+                                        external_ipv4,
+                                        echo.id,
+                                        echo.seq,
                                         payload,
                                         Duration::from_secs(ICMP_PING_TIMEOUT_SECS),
                                     )
-                            .await;
-                        match result {
-                            Ok((icmp, _)) => match icmp {
-                                Icmp::V4(Icmpv4::EchoReply(reply)) => {
+                                    .await?
+                                else {
+                                    continue;
+                                };
+
                                 let packet =
                                     PacketBuilder::ethernet2(key.local_mac.0, key.client_mac.0);
                                 let packet = match (key.external_ip.addr, key.client_ip.addr) {
@@ -123,6 +124,51 @@ impl ProxyIcmpHandler {
                                         IpAddress::Ipv4(external_addr),
                                         IpAddress::Ipv4(client_addr),
                                     ) => packet.ipv4(external_addr.0, client_addr.0, 20),
+                                    _ => {
+                                        return Err(anyhow!("IP endpoint mismatch"));
+                                    }
+                                };
+                                let packet = packet.icmpv4_echo_reply(echo.id, echo.seq);
+                                let mut buffer: Vec<u8> = Vec::new();
+                                packet.write(&mut buffer, &payload)?;
+                                if let Err(error) = tx_sender.try_send(buffer) {
+                                    debug!("failed to transmit icmp packet: {}", error);
+                                }
+                            }
+                        }
+
+                        NetSlice::Ipv6(ipv6) => {
+                            if ipv6.header().next_header() != IpNumber::ICMP {
+                                continue;
+                            }
+
+                            let (header, payload) =
+                                Icmpv6Header::from_slice(ipv6.payload().payload)?;
+                            if let Icmpv6Type::EchoRequest(echo) = header.icmp_type {
+                                let IpAddr::V6(external_ipv6) = key.external_ip.addr.into() else {
+                                    continue;
+                                };
+
+                                let Some(IcmpReply::Icmp6 {
+                                    header: _,
+                                    echo,
+                                    payload,
+                                }) = client
+                                    .ping6(
+                                        external_ipv6,
+                                        echo.id,
+                                        echo.seq,
+                                        payload,
+                                        Duration::from_secs(ICMP_PING_TIMEOUT_SECS),
+                                    )
+                                    .await?
+                                else {
+                                    continue;
+                                };
+
+                                let packet =
+                                    PacketBuilder::ethernet2(key.local_mac.0, key.client_mac.0);
+                                let packet = match (key.external_ip.addr, key.client_ip.addr) {
                                     (
                                         IpAddress::Ipv6(external_addr),
                                         IpAddress::Ipv6(client_addr),
@@ -131,25 +177,13 @@ impl ProxyIcmpHandler {
                                         return Err(anyhow!("IP endpoint mismatch"));
                                     }
                                 };
-                                    let packet = packet.icmpv4_echo_reply(
-                                        reply.identifier.0,
-                                        reply.sequence_number.0,
-                                    );
+                                let packet = packet.icmpv6_echo_reply(echo.id, echo.seq);
                                 let mut buffer: Vec<u8> = Vec::new();
-                                    packet.write(&mut buffer, &reply.payload)?;
+                                packet.write(&mut buffer, &payload)?;
                                 if let Err(error) = tx_sender.try_send(buffer) {
                                     debug!("failed to transmit icmp packet: {}", error);
                                 }
                             }
-
-                                Icmp::V4(Icmpv4::Other(_type, _code, _payload)) => {}
-
-                                _ => {}
-                            },
-
-                            Err(error) => {
-                                debug!("proxy for icmp failed to emulate ICMP ping: {}", error);
-                            }
                         }
                     }
                 }

network/src/proxynat/mod.rs

@@ -16,6 +16,12 @@ mod udp;
 
 pub struct ProxyNatHandlerFactory {}
 
+impl Default for ProxyNatHandlerFactory {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl ProxyNatHandlerFactory {
     pub fn new() -> Self {
         Self {}

network/src/raw_socket.rs

@@ -1,5 +1,6 @@
 use anyhow::Result;
 use futures::ready;
+use std::os::fd::IntoRawFd;
 use std::os::unix::io::{AsRawFd, RawFd};
 use std::pin::Pin;
 use std::task::{Context, Poll};
@@ -7,14 +8,42 @@ use std::{io, mem};
 use tokio::io::unix::AsyncFd;
 use tokio::io::{AsyncRead, AsyncWrite, ReadBuf};
 
+#[derive(Debug)]
+pub enum RawSocketProtocol {
+    Icmpv4,
+    Icmpv6,
+    Ethernet,
+}
+
+impl RawSocketProtocol {
+    pub fn to_socket_domain(&self) -> i32 {
+        match self {
+            RawSocketProtocol::Icmpv4 => libc::AF_INET,
+            RawSocketProtocol::Icmpv6 => libc::AF_INET6,
+            RawSocketProtocol::Ethernet => libc::AF_PACKET,
+        }
+    }
+
+    pub fn to_socket_protocol(&self) -> u16 {
+        match self {
+            RawSocketProtocol::Icmpv4 => libc::IPPROTO_ICMP as u16,
+            RawSocketProtocol::Icmpv6 => libc::IPPROTO_ICMPV6 as u16,
+            RawSocketProtocol::Ethernet => (libc::ETH_P_ALL as u16).to_be(),
+        }
+    }
+
+    pub fn to_socket_type(&self) -> i32 {
+        libc::SOCK_RAW
+    }
+}
+
 const SIOCGIFINDEX: libc::c_ulong = 0x8933;
+const SIOCGIFMTU: libc::c_ulong = 0x8921;
 
 #[derive(Debug)]
 pub struct RawSocketHandle {
-    pub mtu: usize,
-    protocol: libc::c_short,
+    protocol: RawSocketProtocol,
     lower: libc::c_int,
-    ifreq: Ifreq,
 }
 
 impl AsRawFd for RawSocketHandle {
@@ -23,14 +52,21 @@ impl AsRawFd for RawSocketHandle {
     }
 }
 
+impl IntoRawFd for RawSocketHandle {
+    fn into_raw_fd(self) -> RawFd {
+        let fd = self.lower;
+        mem::forget(self);
+        fd
+    }
+}
+
 impl RawSocketHandle {
-    pub fn new(interface: &str) -> io::Result<RawSocketHandle> {
-        let protocol: libc::c_short = 0x0003;
+    pub fn new(protocol: RawSocketProtocol) -> io::Result<RawSocketHandle> {
         let lower = unsafe {
             let lower = libc::socket(
-                libc::AF_PACKET,
-                libc::SOCK_RAW | libc::SOCK_NONBLOCK,
-                protocol.to_be() as i32,
+                protocol.to_socket_domain(),
+                protocol.to_socket_type() | libc::SOCK_NONBLOCK,
+                protocol.to_socket_protocol() as i32,
             );
             if lower == -1 {
                 return Err(io::Error::last_os_error());
@@ -38,25 +74,21 @@ impl RawSocketHandle {
             lower
         };
 
-        Ok(RawSocketHandle {
-            mtu: 1500,
-            protocol,
-            lower,
-            ifreq: ifreq_for(interface),
-        })
+        Ok(RawSocketHandle { protocol, lower })
     }
 
-    pub fn bind(interface: &str) -> Result<Self> {
-        let mut socket = RawSocketHandle::new(interface)?;
-        socket.bind_interface()?;
+    pub fn bound_to_interface(interface: &str, protocol: RawSocketProtocol) -> Result<Self> {
+        let mut socket = RawSocketHandle::new(protocol)?;
+        socket.bind_to_interface(interface)?;
         Ok(socket)
     }
 
-    pub fn bind_interface(&mut self) -> io::Result<()> {
+    pub fn bind_to_interface(&mut self, interface: &str) -> io::Result<()> {
+        let mut ifreq = ifreq_for(interface);
         let sockaddr = libc::sockaddr_ll {
             sll_family: libc::AF_PACKET as u16,
-            sll_protocol: self.protocol.to_be() as u16,
-            sll_ifindex: ifreq_ioctl(self.lower, &mut self.ifreq, SIOCGIFINDEX)?,
+            sll_protocol: self.protocol.to_socket_protocol(),
+            sll_ifindex: ifreq_ioctl(self.lower, &mut ifreq, SIOCGIFINDEX)?,
             sll_hatype: 1,
             sll_pkttype: 0,
             sll_halen: 6,
@@ -77,6 +109,11 @@ impl RawSocketHandle {
         Ok(())
     }
 
+    pub fn mtu_of_interface(&mut self, interface: &str) -> io::Result<usize> {
+        let mut ifreq = ifreq_for(interface);
+        ifreq_ioctl(self.lower, &mut ifreq, SIOCGIFMTU).map(|mtu| mtu as usize)
+    }
+
     pub fn recv(&self, buffer: &mut [u8]) -> io::Result<usize> {
         unsafe {
             let len = libc::recv(
@@ -120,7 +157,7 @@ impl Drop for RawSocketHandle {
 #[derive(Debug)]
 struct Ifreq {
     ifr_name: [libc::c_char; libc::IF_NAMESIZE],
-    ifr_data: libc::c_int, /* ifr_ifindex or ifr_mtu */
+    ifr_data: libc::c_int,
 }
 
 fn ifreq_for(name: &str) -> Ifreq {
@@ -160,10 +197,24 @@ impl AsyncRawSocket {
         })
     }
 
-    pub fn bind(interface: &str) -> Result<Self> {
-        let socket = RawSocketHandle::bind(interface)?;
+    pub fn bound_to_interface(interface: &str, protocol: RawSocketProtocol) -> Result<Self> {
+        let socket = RawSocketHandle::bound_to_interface(interface, protocol)?;
         AsyncRawSocket::new(socket)
     }
+
+    pub fn mtu_of_interface(&mut self, interface: &str) -> Result<usize> {
+        Ok(self.inner.get_mut().mtu_of_interface(interface)?)
+    }
+}
+
+impl TryFrom<RawSocketHandle> for AsyncRawSocket {
+    type Error = anyhow::Error;
+
+    fn try_from(value: RawSocketHandle) -> Result<Self, Self::Error> {
+        Ok(Self {
+            inner: AsyncFd::new(value)?,
+        })
+    }
 }
 
 impl AsyncRead for AsyncRawSocket {