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use dns_parser::{ rdata::{Srv, A}, Packet, RData, ResourceRecord, }; use if_addrs::IfAddr; use std::{ collections::{HashMap, HashSet}, error::Error, io, net::{Ipv4Addr, SocketAddr, UdpSocket}, sync::{ mpsc::{sync_channel, RecvTimeoutError, SyncSender}, Arc, Mutex, }, thread::{self, JoinHandle}, time::{Duration, Instant}, }; #[cfg(not(target_os = "windows"))] use net2::unix::UnixUdpBuilderExt; const MULTICAST_ADDR: Ipv4Addr = Ipv4Addr::new(224, 0, 0, 251); const MULTICAST_PORT: u16 = 5353; #[cfg(not(target_os = "windows"))] fn create_socket(addr: Ipv4Addr) -> io::Result<std::net::UdpSocket> { net2::UdpBuilder::new_v4()? .reuse_address(true)? .reuse_port(true)? .bind((addr, MULTICAST_PORT)) } #[cfg(target_os = "windows")] fn create_socket(addr: Ipv4Addr) -> io::Result<std::net::UdpSocket> { net2::UdpBuilder::new_v4()? .reuse_address(true)? .bind((addr, MULTICAST_PORT)) } pub fn send_request(socket: &UdpSocket, service: &str) -> Result<(), Box<dyn Error>> { let mut builder = dns_parser::Builder::new_query(0, false); let prefer_unicast = false; builder.add_question( service, prefer_unicast, dns_parser::QueryType::SRV, dns_parser::QueryClass::IN, ); let packet_data = builder.build().unwrap(); let addr = SocketAddr::new(MULTICAST_ADDR.into(), MULTICAST_PORT); socket.send_to(&packet_data, addr).ok(); Ok(()) } pub fn handle_response( packet: &Packet, service: &str, database: &Mutex<HashMap<Service, ServiceRecord>>, ) { if packet.header.query { return; } let mut database = database.lock().unwrap(); for answer in &packet.answers { if let ResourceRecord { name, data: RData::SRV(Srv { target, port, .. }), .. } = answer { if name.to_string() == service { let service = Service { host: target.to_string(), port: *port, }; database .entry(service) .and_modify(|e| e.last_seen_time = Instant::now()) .or_insert_with(|| ServiceRecord { last_seen_time: Instant::now(), addresses: HashSet::new(), }); } } } for answer in &packet.answers { if let ResourceRecord { name, data: RData::A(A(addr)), .. } = answer { for (k, v) in database.iter_mut() { if k.host == name.to_string() { v.addresses.insert(*addr); } } } } } pub fn recive_response( socket: &UdpSocket, service: &str, database: &Mutex<HashMap<Service, ServiceRecord>>, ) -> Result<(), Box<dyn Error>> { let mut buffer: [u8; 2048] = [0; 2048]; loop { let count = socket.recv(&mut buffer)?; if let Ok(packet) = dns_parser::Packet::parse(&buffer[..count]) { handle_response(&packet, service, database); } } } fn remove_old_entries(database: &Mutex<HashMap<Service, ServiceRecord>>) { let mut database = database.lock().unwrap(); database.retain(|_, v| v.last_seen_time.elapsed() < Duration::from_secs(5)); } #[derive(Clone, Debug, Hash, PartialEq, Eq)] pub struct Service { pub host: String, pub port: u16, } #[derive(Clone, Debug)] pub struct ServiceRecord { pub last_seen_time: Instant, pub addresses: HashSet<Ipv4Addr>, } pub struct MdnsClient { database: Arc<Mutex<HashMap<Service, ServiceRecord>>>, exit_tx: SyncSender<()>, thread: Option<JoinHandle<()>>, } impl MdnsClient { pub fn new(service: &str) -> Result<MdnsClient, Box<dyn Error>> { let database = Arc::new(Mutex::new(HashMap::new())); let mut sockets = Vec::new(); for iface in if_addrs::get_if_addrs()? .into_iter() .filter(|i| !i.addr.is_loopback()) .filter_map(|i| { if let IfAddr::V4(v4_addr) = i.addr { Some(v4_addr) } else { None } }) { let socket = create_socket(iface.ip)?; socket.set_multicast_loop_v4(true)?; socket.join_multicast_v4(&MULTICAST_ADDR, &iface.ip)?; socket.set_nonblocking(true)?; sockets.push(socket); } let (exit_tx, exit_rx) = sync_channel(0); let thread = thread::spawn({ let service = service.to_string(); let database = database.clone(); move || loop { match exit_rx.recv_timeout(Duration::from_secs(1)) { Ok(()) | Err(RecvTimeoutError::Disconnected) => break, Err(RecvTimeoutError::Timeout) => { for socket in &sockets { send_request(&socket, &service).ok(); recive_response(&socket, &service, &database).ok(); } remove_old_entries(&database); } } } }); Ok(MdnsClient { database, exit_tx, thread: Some(thread), }) } pub fn get_services(&self) -> Vec<(Service, ServiceRecord)> { self.database .lock() .unwrap() .iter() .map(|(service, record)| (service.clone(), record.clone())) .collect() } } impl Drop for MdnsClient { fn drop(&mut self) { self.exit_tx.send(()).ok(); self.thread.take().map(JoinHandle::join); } }