network: begin work on ICMP

network/src/proxynat/icmp.rs

@@ -0,0 +1,166 @@
+use std::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 log::{debug, warn};
+use smoltcp::wire::IpAddress;
+use tokio::{
+    select,
+    sync::mpsc::{Receiver, Sender},
+};
+
+use crate::nat::{NatHandler, NatKey};
+
+const ICMP_PING_TIMEOUT_SECS: u64 = 20;
+const ICMP_TIMEOUT_SECS: u64 = 30;
+
+pub struct ProxyIcmpHandler {
+    key: NatKey,
+    rx_sender: Sender<Vec<u8>>,
+}
+
+#[async_trait]
+impl NatHandler for ProxyIcmpHandler {
+    async fn receive(&self, data: &[u8]) -> Result<()> {
+        self.rx_sender.try_send(data.to_vec())?;
+        Ok(())
+    }
+}
+
+enum ProxyIcmpSelect {
+    Internal(Vec<u8>),
+    Close,
+}
+
+impl ProxyIcmpHandler {
+    pub fn new(key: NatKey, rx_sender: Sender<Vec<u8>>) -> Self {
+        ProxyIcmpHandler { key, rx_sender }
+    }
+
+    pub async fn spawn(
+        &mut self,
+        rx_receiver: Receiver<Vec<u8>>,
+        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 key = self.key;
+        tokio::spawn(async move {
+            if let Err(error) =
+                ProxyIcmpHandler::process(client, key, rx_receiver, tx_sender, reclaim_sender).await
+            {
+                warn!("processing of icmp proxy failed: {}", error);
+            }
+        });
+        Ok(())
+    }
+
+    async fn process(
+        client: PingClient<icmp_client::impl_tokio::Client>,
+        key: NatKey,
+        mut rx_receiver: Receiver<Vec<u8>>,
+        tx_sender: Sender<Vec<u8>>,
+        reclaim_sender: Sender<NatKey>,
+    ) -> Result<()> {
+        loop {
+            let deadline = tokio::time::sleep(Duration::from_secs(ICMP_TIMEOUT_SECS));
+            let selection = select! {
+                x = rx_receiver.recv() => if let Some(data) = x {
+                    ProxyIcmpSelect::Internal(data)
+                } else {
+                    ProxyIcmpSelect::Close
+                },
+                _ =  deadline => ProxyIcmpSelect::Close,
+            };
+
+            match selection {
+                ProxyIcmpSelect::Internal(data) => {
+                    let packet = SlicedPacket::from_ethernet(&data)?;
+                    let Some(ref net) = packet.net else {
+                        continue;
+                    };
+
+                    let Some(ip) = net.ip_payload_ref() else {
+                        continue;
+                    };
+
+                    if ip.ip_number != IpNumber::ICMP {
+                        continue;
+                    }
+
+                    let (header, payload) = Icmpv4Header::from_slice(ip.payload)?;
+                    if let Icmpv4Type::EchoRequest(echo) = header.icmp_type {
+                        let result = client
+                            .ping(
+                                key.external_ip.addr.into(),
+                                Some(echo.id),
+                                Some(echo.seq),
+                                payload,
+                                Duration::from_secs(ICMP_PING_TIMEOUT_SECS),
+                            )
+                            .await;
+                        match result {
+                            Ok((icmp, _)) => match icmp {
+                                Icmp::V4(Icmpv4::EchoReply(reply)) => {
+                                    let packet =
+                                        PacketBuilder::ethernet2(key.local_mac.0, key.client_mac.0);
+                                    let packet = match (key.external_ip.addr, key.client_ip.addr) {
+                                        (
+                                            IpAddress::Ipv4(external_addr),
+                                            IpAddress::Ipv4(client_addr),
+                                        ) => packet.ipv4(external_addr.0, client_addr.0, 20),
+                                        (
+                                            IpAddress::Ipv6(external_addr),
+                                            IpAddress::Ipv6(client_addr),
+                                        ) => packet.ipv6(external_addr.0, client_addr.0, 20),
+                                        _ => {
+                                            return Err(anyhow!("IP endpoint mismatch"));
+                                        }
+                                    };
+                                    let packet = packet.icmpv4_echo_reply(
+                                        reply.identifier.0,
+                                        reply.sequence_number.0,
+                                    );
+                                    let mut buffer: Vec<u8> = Vec::new();
+                                    packet.write(&mut buffer, &reply.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);
+                            }
+                        }
+                    }
+                }
+
+                ProxyIcmpSelect::Close => {
+                    reclaim_sender.send(key).await?;
+                    break;
+                }
+            }
+        }
+
+        Ok(())
+    }
+}