udp.rs - Codebrowser

1	use crate::io::{Interest, PollEvented, ReadBuf, Ready};
2	use crate::net::{to_socket_addrs, ToSocketAddrs};
3
4	use std::fmt;
5	use std::io;
6	use std::net::{self, Ipv4Addr, Ipv6Addr, SocketAddr};
7	use std::task::{Context, Poll};
8
9	cfg_io_util! {
10	use bytes::BufMut;
11	}
12
13	cfg_net! {
14	/// A UDP socket.
15	///
16	/// UDP is "connectionless", unlike TCP. Meaning, regardless of what address you've bound to, a `UdpSocket`
17	/// is free to communicate with many different remotes. In tokio there are basically two main ways to use `UdpSocket`:
18	///
19	/// one to many: [`bind`](`UdpSocket::bind`) and use [`send_to`](`UdpSocket::send_to`)*
20	/// and [`recv_from`](`UdpSocket::recv_from`) to communicate with many different addresses
21	/// one to one: [`connect`](`UdpSocket::connect`) and associate with a single address, using [`send`](`UdpSocket::send`)*
22	/// and [`recv`](`UdpSocket::recv`) to communicate only with that remote address
23	///
24	/// This type does not provide a `split` method, because this functionality
25	/// can be achieved by instead wrapping the socket in an [`Arc`]. Note that
26	/// you do not need a `Mutex` to share the `UdpSocket` — an `Arc<UdpSocket>`
27	/// is enough. This is because all of the methods take `&self` instead of
28	/// `&mut self`. Once you have wrapped it in an `Arc`, you can call
29	/// `.clone()` on the `Arc<UdpSocket>` to get multiple shared handles to the
30	/// same socket. An example of such usage can be found further down.
31	///
32	/// [`Arc`]: std::sync::Arc
33	///
34	/// # Streams
35	///
36	/// If you need to listen over UDP and produce a [`Stream`], you can look
37	/// at [`UdpFramed`].
38	///
39	/// [`UdpFramed`]: https://docs.rs/tokio-util/latest/tokio_util/udp/struct.UdpFramed.html
40	/// [`Stream`]: https://docs.rs/futures/0.3/futures/stream/trait.Stream.html
41	///
42	/// # Example: one to many (bind)
43	///
44	/// Using `bind` we can create a simple echo server that sends and recv's with many different clients:
45	/// ```no_run
46	/// use tokio::net::UdpSocket;
47	/// use std::io;
48	///
49	/// #[tokio::main]
50	/// async fn main() -> io::Result<()> {
51	/// let sock = UdpSocket::bind("0.0.0.0:8080").await?;
52	/// let mut buf = [0; 1024];
53	/// loop {
54	/// let (len, addr) = sock.recv_from(&mut buf).await?;
55	/// println!("{:?} bytes received from {:?}", len, addr);
56	///
57	/// let len = sock.send_to(&buf[..len], addr).await?;
58	/// println!("{:?} bytes sent", len);
59	/// }
60	/// }
61	/// ```
62	///
63	/// # Example: one to one (connect)
64	///
65	/// Or using `connect` we can echo with a single remote address using `send` and `recv`:
66	/// ```no_run
67	/// use tokio::net::UdpSocket;
68	/// use std::io;
69	///
70	/// #[tokio::main]
71	/// async fn main() -> io::Result<()> {
72	/// let sock = UdpSocket::bind("0.0.0.0:8080").await?;
73	///
74	/// let remote_addr = "127.0.0.1:59611";
75	/// sock.connect(remote_addr).await?;
76	/// let mut buf = [0; 1024];
77	/// loop {
78	/// let len = sock.recv(&mut buf).await?;
79	/// println!("{:?} bytes received from {:?}", len, remote_addr);
80	///
81	/// let len = sock.send(&buf[..len]).await?;
82	/// println!("{:?} bytes sent", len);
83	/// }
84	/// }
85	/// ```
86	///
87	/// # Example: Splitting with `Arc`
88	///
89	/// Because `send_to` and `recv_from` take `&self`. It's perfectly alright
90	/// to use an `Arc<UdpSocket>` and share the references to multiple tasks.
91	/// Here is a similar "echo" example that supports concurrent
92	/// sending/receiving:
93	///
94	/// ```no_run
95	/// use tokio::{net::UdpSocket, sync::mpsc};
96	/// use std::{io, net::SocketAddr, sync::Arc};
97	///
98	/// #[tokio::main]
99	/// async fn main() -> io::Result<()> {
100	/// let sock = UdpSocket::bind("0.0.0.0:8080".parse::<SocketAddr>().unwrap()).await?;
101	/// let r = Arc::new(sock);
102	/// let s = r.clone();
103	/// let (tx, mut rx) = mpsc::channel::<(Vec<u8>, SocketAddr)>(1_000);
104	///
105	/// tokio::spawn(async move {
106	/// while let Some((bytes, addr)) = rx.recv().await {
107	/// let len = s.send_to(&bytes, &addr).await.unwrap();
108	/// println!("{:?} bytes sent", len);
109	/// }
110	/// });
111	///
112	/// let mut buf = [0; 1024];
113	/// loop {
114	/// let (len, addr) = r.recv_from(&mut buf).await?;
115	/// println!("{:?} bytes received from {:?}", len, addr);
116	/// tx.send((buf[..len].to_vec(), addr)).await.unwrap();
117	/// }
118	/// }
119	/// ```
120	///
121	pub struct UdpSocket {
122	io: PollEvented<mio::net::UdpSocket>,
123	}
124	}
125
126	impl UdpSocket {
127	/// This function will create a new UDP socket and attempt to bind it to
128	/// the `addr` provided.
129	///
130	/// Binding with a port number of 0 will request that the OS assigns a port
131	/// to this listener. The port allocated can be queried via the `local_addr`
132	/// method.
133	///
134	/// # Example
135	///
136	/// ```no_run
137	/// use tokio::net::UdpSocket;
138	/// use std::io;
139	///
140	/// #[tokio::main]
141	/// async fn main() -> io::Result<()> {
142	/// let sock = UdpSocket::bind("0.0.0.0:8080").await?;
143	/// // use `sock`
144	/// # let _ = sock;
145	/// Ok(())
146	/// }
147	/// ```
148	pub async fn bind<A: ToSocketAddrs>(addr: A) -> io::Result<UdpSocket> {
149	let addrs = to_socket_addrs(addr).await?;
150	let mut last_err = None;
151
152	for addr in addrs {
153	match UdpSocket::bind_addr(addr) {
154	Ok(socket) => return Ok(socket),
155	Err(e) => last_err = Some(e),
156	}
157	}
158
159	Err(last_err.unwrap_or_else(\|\| {
160	io::Error::new(
161	io::ErrorKind::InvalidInput,
162	"could not resolve to any address",
163	)
164	}))
165	}
166
167	fn bind_addr(addr: SocketAddr) -> io::Result<UdpSocket> {
168	let sys = mio::net::UdpSocket::bind(addr)?;
169	UdpSocket::new(sys)
170	}
171
172	#[track_caller]
173	fn new(socket: mio::net::UdpSocket) -> io::Result<UdpSocket> {
174	let io = PollEvented::new(socket)?;
175	Ok(UdpSocket { io })
176	}
177
178	/// Creates new `UdpSocket` from a previously bound `std::net::UdpSocket`.
179	///
180	/// This function is intended to be used to wrap a UDP socket from the
181	/// standard library in the Tokio equivalent.
182	///
183	/// This can be used in conjunction with socket2's `Socket` interface to
184	/// configure a socket before it's handed off, such as setting options like
185	/// `reuse_address` or binding to multiple addresses.
186	///
187	/// # Notes
188	///
189	/// The caller is responsible for ensuring that the socket is in
190	/// non-blocking mode. Otherwise all I/O operations on the socket
191	/// will block the thread, which will cause unexpected behavior.
192	/// Non-blocking mode can be set using [`set_nonblocking`].
193	///
194	/// [`set_nonblocking`]: std::net::UdpSocket::set_nonblocking
195	///
196	/// # Panics
197	///
198	/// This function panics if thread-local runtime is not set.
199	///
200	/// The runtime is usually set implicitly when this function is called
201	/// from a future driven by a tokio runtime, otherwise runtime can be set
202	/// explicitly with [`Runtime::enter`](crate::runtime::Runtime::enter) function.
203	///
204	/// # Example
205	///
206	/// ```no_run
207	/// use tokio::net::UdpSocket;
208	/// # use std::{io, net::SocketAddr};
209	///
210	/// # #[tokio::main]
211	/// # async fn main() -> io::Result<()> {
212	/// let addr = "0.0.0.0:8080".parse::<SocketAddr>().unwrap();
213	/// let std_sock = std::net::UdpSocket::bind(addr)?;
214	/// std_sock.set_nonblocking(`true`)?;
215	/// let sock = UdpSocket::from_std(std_sock)?;
216	/// // use `sock`
217	/// # Ok(())
218	/// # }
219	/// ```
220	#[track_caller]
221	pub fn from_std(socket: net::UdpSocket) -> io::Result<UdpSocket> {
222	let io = mio::net::UdpSocket::from_std(socket);
223	UdpSocket::new(io)
224	}
225
226	/// Turns a [`tokio::net::UdpSocket`] into a [`std::net::UdpSocket`].
227	///
228	/// The returned [`std::net::UdpSocket`] will have nonblocking mode set as
229	/// `true`. Use [`set_nonblocking`] to change the blocking mode if needed.
230	///
231	/// # Examples
232	///
233	/// ```rust,no_run
234	/// use std::error::Error;
235	///
236	/// #[tokio::main]
237	/// async fn main() -> Result<(), Box<dyn Error>> {
238	/// let tokio_socket = tokio::net::UdpSocket::bind("127.0.0.1:0").await?;
239	/// let std_socket = tokio_socket.into_std()?;
240	/// std_socket.set_nonblocking(`false`)?;
241	/// Ok(())
242	/// }
243	/// ```
244	///
245	/// [`tokio::net::UdpSocket`]: UdpSocket
246	/// [`std::net::UdpSocket`]: std::net::UdpSocket
247	/// [`set_nonblocking`]: fn@std::net::UdpSocket::set_nonblocking
248	pub fn into_std(self) -> io::Result<std::net::UdpSocket> {
249	#[cfg(unix)]
250	{
251	use std::os::unix::io::{FromRawFd, IntoRawFd};
252	self.io
253	.into_inner()
254	.map(IntoRawFd::into_raw_fd)
255	.map(\|raw_fd\| unsafe { std::net::UdpSocket::from_raw_fd(raw_fd) })
256	}
257
258	#[cfg(windows)]
259	{
260	use std::os::windows::io::{FromRawSocket, IntoRawSocket};
261	self.io
262	.into_inner()
263	.map(\|io\| io.into_raw_socket())
264	.map(\|raw_socket\| unsafe { std::net::UdpSocket::from_raw_socket(raw_socket) })
265	}
266	}
267
268	fn as_socket(&self) -> socket2::SockRef<'_> {
269	socket2::SockRef::from(self)
270	}
271
272	/// Returns the local address that this socket is bound to.
273	///
274	/// # Example
275	///
276	/// ```no_run
277	/// use tokio::net::UdpSocket;
278	/// # use std::{io, net::SocketAddr};
279	///
280	/// # #[tokio::main]
281	/// # async fn main() -> io::Result<()> {
282	/// let addr = "0.0.0.0:8080".parse::<SocketAddr>().unwrap();
283	/// let sock = UdpSocket::bind(addr).await?;
284	/// // the address the socket is bound to
285	/// let local_addr = sock.local_addr()?;
286	/// # Ok(())
287	/// # }
288	/// ```
289	pub fn local_addr(&self) -> io::Result<SocketAddr> {
290	self.io.local_addr()
291	}
292
293	/// Returns the socket address of the remote peer this socket was connected to.
294	///
295	/// # Example
296	///
297	/// ```
298	/// use tokio::net::UdpSocket;
299	///
300	/// # use std::{io, net::SocketAddr};
301	/// # #[tokio::main]
302	/// # async fn main() -> io::Result<()> {
303	/// let addr = "0.0.0.0:8080".parse::<SocketAddr>().unwrap();
304	/// let peer = "127.0.0.1:11100".parse::<SocketAddr>().unwrap();
305	/// let sock = UdpSocket::bind(addr).await?;
306	/// sock.connect(peer).await?;
307	/// assert_eq!(peer, sock.peer_addr()?);
308	/// # Ok(())
309	/// # }
310	/// ```
311	pub fn peer_addr(&self) -> io::Result<SocketAddr> {
312	self.io.peer_addr()
313	}
314
315	/// Connects the UDP socket setting the default destination for send() and
316	/// limiting packets that are read via recv from the address specified in
317	/// `addr`.
318	///
319	/// # Example
320	///
321	/// ```no_run
322	/// use tokio::net::UdpSocket;
323	/// # use std::{io, net::SocketAddr};
324	///
325	/// # #[tokio::main]
326	/// # async fn main() -> io::Result<()> {
327	/// let sock = UdpSocket::bind("0.0.0.0:8080".parse::<SocketAddr>().unwrap()).await?;
328	///
329	/// let remote_addr = "127.0.0.1:59600".parse::<SocketAddr>().unwrap();
330	/// sock.connect(remote_addr).await?;
331	/// let mut buf = [`0u8`; `32`];
332	/// // recv from remote_addr
333	/// let len = sock.recv(&mut buf).await?;
334	/// // send to remote_addr
335	/// let _len = sock.send(&buf[..len]).await?;
336	/// # Ok(())
337	/// # }
338	/// ```
339	pub async fn connect<A: ToSocketAddrs>(&self, addr: A) -> io::Result<()> {
340	let addrs = to_socket_addrs(addr).await?;
341	let mut last_err = None;
342
343	for addr in addrs {
344	match self.io.connect(addr) {
345	Ok(()) => return Ok(()),
346	Err(e) => last_err = Some(e),
347	}
348	}
349
350	Err(last_err.unwrap_or_else(\|\| {
351	io::Error::new(
352	io::ErrorKind::InvalidInput,
353	"could not resolve to any address",
354	)
355	}))
356	}
357
358	/// Waits for any of the requested ready states.
359	///
360	/// This function is usually paired with `try_recv()` or `try_send()`. It
361	/// can be used to concurrently recv / send to the same socket on a single
362	/// task without splitting the socket.
363	///
364	/// The function may complete without the socket being ready. This is a
365	/// false-positive and attempting an operation will return with
366	/// `io::ErrorKind::WouldBlock`. The function can also return with an empty
367	/// [`Ready`] set, so you should always check the returned value and possibly
368	/// wait again if the requested states are not set.
369	///
370	/// # Cancel safety
371	///
372	/// This method is cancel safe. Once a readiness event occurs, the method
373	/// will continue to return immediately until the readiness event is
374	/// consumed by an attempt to read or write that fails with `WouldBlock` or
375	/// `Poll::Pending`.
376	///
377	/// # Examples
378	///
379	/// Concurrently receive from and send to the socket on the same task
380	/// without splitting.
381	///
382	/// ```no_run
383	/// use tokio::io::{self, Interest};
384	/// use tokio::net::UdpSocket;
385	///
386	/// #[tokio::main]
387	/// async fn main() -> io::Result<()> {
388	/// let socket = UdpSocket::bind("127.0.0.1:8080").await?;
389	/// socket.connect("127.0.0.1:8081").await?;
390	///
391	/// loop {
392	/// let ready = socket.ready(Interest::READABLE \| Interest::WRITABLE).await?;
393	///
394	/// if ready.is_readable() {
395	/// // The buffer is not* included in the async task and will only exist*
396	/// // on the stack.
397	/// let mut data = [`0`; `1024`];
398	/// match socket.try_recv(&mut data[..]) {
399	/// Ok(n) => {
400	/// println!("received {:?}", &data[..n]);
401	/// }
402	/// // False-positive, continue
403	/// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {}
404	/// Err(e) => {
405	/// return Err(e);
406	/// }
407	/// }
408	/// }
409	///
410	/// if ready.is_writable() {
411	/// // Write some data
412	/// match socket.try_send(b"hello world") {
413	/// Ok(n) => {
414	/// println!("sent {} bytes", n);
415	/// }
416	/// // False-positive, continue
417	/// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {}
418	/// Err(e) => {
419	/// return Err(e);
420	/// }
421	/// }
422	/// }
423	/// }
424	/// }
425	/// ```
426	pub async fn ready(&self, interest: Interest) -> io::Result<Ready> {
427	let event = self.io.registration().readiness(interest).await?;
428	Ok(event.ready)
429	}
430
431	/// Waits for the socket to become writable.
432	///
433	/// This function is equivalent to `ready(Interest::WRITABLE)` and is
434	/// usually paired with `try_send()` or `try_send_to()`.
435	///
436	/// The function may complete without the socket being writable. This is a
437	/// false-positive and attempting a `try_send()` will return with
438	/// `io::ErrorKind::WouldBlock`.
439	///
440	/// # Cancel safety
441	///
442	/// This method is cancel safe. Once a readiness event occurs, the method
443	/// will continue to return immediately until the readiness event is
444	/// consumed by an attempt to write that fails with `WouldBlock` or
445	/// `Poll::Pending`.
446	///
447	/// # Examples
448	///
449	/// ```no_run
450	/// use tokio::net::UdpSocket;
451	/// use std::io;
452	///
453	/// #[tokio::main]
454	/// async fn main() -> io::Result<()> {
455	/// // Bind socket
456	/// let socket = UdpSocket::bind("127.0.0.1:8080").await?;
457	/// socket.connect("127.0.0.1:8081").await?;
458	///
459	/// loop {
460	/// // Wait for the socket to be writable
461	/// socket.writable().await?;
462	///
463	/// // Try to send data, this may still fail with `WouldBlock`
464	/// // if the readiness event is a false positive.
465	/// match socket.try_send(b"hello world") {
466	/// Ok(n) => {
467	/// break;
468	/// }
469	/// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
470	/// continue;
471	/// }
472	/// Err(e) => {
473	/// return Err(e);
474	/// }
475	/// }
476	/// }
477	///
478	/// Ok(())
479	/// }
480	/// ```
481	pub async fn writable(&self) -> io::Result<()> {
482	self.ready(Interest::WRITABLE).await?;
483	Ok(())
484	}
485
486	/// Polls for write/send readiness.
487	///
488	/// If the udp stream is not currently ready for sending, this method will
489	/// store a clone of the `Waker` from the provided `Context`. When the udp
490	/// stream becomes ready for sending, `Waker::wake` will be called on the
491	/// waker.
492	///
493	/// Note that on multiple calls to `poll_send_ready` or `poll_send`, only
494	/// the `Waker` from the `Context` passed to the most recent call is
495	/// scheduled to receive a wakeup. (However, `poll_recv_ready` retains a
496	/// second, independent waker.)
497	///
498	/// This function is intended for cases where creating and pinning a future
499	/// via [`writable`] is not feasible. Where possible, using [`writable`] is
500	/// preferred, as this supports polling from multiple tasks at once.
501	///
502	/// # Return value
503	///
504	/// The function returns:
505	///
506	/// `Poll::Pending` if the udp stream is not ready for writing.*
507	/// `Poll::Ready(Ok(()))` if the udp stream is ready for writing.*
508	/// `Poll::Ready(Err(e))` if an error is encountered.*
509	///
510	/// # Errors
511	///
512	/// This function may encounter any standard I/O error except `WouldBlock`.
513	///
514	/// [`writable`]: method@Self::writable
515	pub fn poll_send_ready(&self, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
516	self.io.registration().poll_write_ready(cx).map_ok(\|_\| ())
517	}
518
519	/// Sends data on the socket to the remote address that the socket is
520	/// connected to.
521	///
522	/// The [`connect`] method will connect this socket to a remote address.
523	/// This method will fail if the socket is not connected.
524	///
525	/// [`connect`]: method@Self::connect
526	///
527	/// # Return
528	///
529	/// On success, the number of bytes sent is returned, otherwise, the
530	/// encountered error is returned.
531	///
532	/// # Cancel safety
533	///
534	/// This method is cancel safe. If `send` is used as the event in a
535	/// [`tokio::select!`](crate::select) statement and some other branch
536	/// completes first, then it is guaranteed that the message was not sent.
537	///
538	/// # Examples
539	///
540	/// ```no_run
541	/// use tokio::io;
542	/// use tokio::net::UdpSocket;
543	///
544	/// #[tokio::main]
545	/// async fn main() -> io::Result<()> {
546	/// // Bind socket
547	/// let socket = UdpSocket::bind("127.0.0.1:8080").await?;
548	/// socket.connect("127.0.0.1:8081").await?;
549	///
550	/// // Send a message
551	/// socket.send(b"hello world").await?;
552	///
553	/// Ok(())
554	/// }
555	/// ```
556	pub async fn send(&self, buf: &[u8]) -> io::Result<usize> {
557	self.io
558	.registration()
559	.async_io(Interest::WRITABLE, \|\| self.io.send(buf))
560	.await
561	}
562
563	/// Attempts to send data on the socket to the remote address to which it
564	/// was previously `connect`ed.
565	///
566	/// The [`connect`] method will connect this socket to a remote address.
567	/// This method will fail if the socket is not connected.
568	///
569	/// Note that on multiple calls to a `poll_` method in the send direction,*
570	/// only the `Waker` from the `Context` passed to the most recent call will
571	/// be scheduled to receive a wakeup.
572	///
573	/// # Return value
574	///
575	/// The function returns:
576	///
577	/// `Poll::Pending` if the socket is not available to write*
578	/// `Poll::Ready(Ok(n))` `n` is the number of bytes sent*
579	/// `Poll::Ready(Err(e))` if an error is encountered.*
580	///
581	/// # Errors
582	///
583	/// This function may encounter any standard I/O error except `WouldBlock`.
584	///
585	/// [`connect`]: method@Self::connect
586	pub fn poll_send(&self, cx: &mut Context<'_>, buf: &[u8]) -> Poll<io::Result<usize>> {
587	self.io
588	.registration()
589	.poll_write_io(cx, \|\| self.io.send(buf))
590	}
591
592	/// Tries to send data on the socket to the remote address to which it is
593	/// connected.
594	///
595	/// When the socket buffer is full, `Err(io::ErrorKind::WouldBlock)` is
596	/// returned. This function is usually paired with `writable()`.
597	///
598	/// # Returns
599	///
600	/// If successful, `Ok(n)` is returned, where `n` is the number of bytes
601	/// sent. If the socket is not ready to send data,
602	/// `Err(ErrorKind::WouldBlock)` is returned.
603	///
604	/// # Examples
605	///
606	/// ```no_run
607	/// use tokio::net::UdpSocket;
608	/// use std::io;
609	///
610	/// #[tokio::main]
611	/// async fn main() -> io::Result<()> {
612	/// // Bind a UDP socket
613	/// let socket = UdpSocket::bind("127.0.0.1:8080").await?;
614	///
615	/// // Connect to a peer
616	/// socket.connect("127.0.0.1:8081").await?;
617	///
618	/// loop {
619	/// // Wait for the socket to be writable
620	/// socket.writable().await?;
621	///
622	/// // Try to send data, this may still fail with `WouldBlock`
623	/// // if the readiness event is a false positive.
624	/// match socket.try_send(b"hello world") {
625	/// Ok(n) => {
626	/// break;
627	/// }
628	/// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
629	/// continue;
630	/// }
631	/// Err(e) => {
632	/// return Err(e);
633	/// }
634	/// }
635	/// }
636	///
637	/// Ok(())
638	/// }
639	/// ```
640	pub fn try_send(&self, buf: &[u8]) -> io::Result<usize> {
641	self.io
642	.registration()
643	.try_io(Interest::WRITABLE, \|\| self.io.send(buf))
644	}
645
646	/// Waits for the socket to become readable.
647	///
648	/// This function is equivalent to `ready(Interest::READABLE)` and is usually
649	/// paired with `try_recv()`.
650	///
651	/// The function may complete without the socket being readable. This is a
652	/// false-positive and attempting a `try_recv()` will return with
653	/// `io::ErrorKind::WouldBlock`.
654	///
655	/// # Cancel safety
656	///
657	/// This method is cancel safe. Once a readiness event occurs, the method
658	/// will continue to return immediately until the readiness event is
659	/// consumed by an attempt to read that fails with `WouldBlock` or
660	/// `Poll::Pending`.
661	///
662	/// # Examples
663	///
664	/// ```no_run
665	/// use tokio::net::UdpSocket;
666	/// use std::io;
667	///
668	/// #[tokio::main]
669	/// async fn main() -> io::Result<()> {
670	/// // Connect to a peer
671	/// let socket = UdpSocket::bind("127.0.0.1:8080").await?;
672	/// socket.connect("127.0.0.1:8081").await?;
673	///
674	/// loop {
675	/// // Wait for the socket to be readable
676	/// socket.readable().await?;
677	///
678	/// // The buffer is not* included in the async task and will*
679	/// // only exist on the stack.
680	/// let mut buf = [`0`; `1024`];
681	///
682	/// // Try to recv data, this may still fail with `WouldBlock`
683	/// // if the readiness event is a false positive.
684	/// match socket.try_recv(&mut buf) {
685	/// Ok(n) => {
686	/// println!("GOT {:?}", &buf[..n]);
687	/// break;
688	/// }
689	/// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
690	/// continue;
691	/// }
692	/// Err(e) => {
693	/// return Err(e);
694	/// }
695	/// }
696	/// }
697	///
698	/// Ok(())
699	/// }
700	/// ```
701	pub async fn readable(&self) -> io::Result<()> {
702	self.ready(Interest::READABLE).await?;
703	Ok(())
704	}
705
706	/// Polls for read/receive readiness.
707	///
708	/// If the udp stream is not currently ready for receiving, this method will
709	/// store a clone of the `Waker` from the provided `Context`. When the udp
710	/// socket becomes ready for reading, `Waker::wake` will be called on the
711	/// waker.
712	///
713	/// Note that on multiple calls to `poll_recv_ready`, `poll_recv` or
714	/// `poll_peek`, only the `Waker` from the `Context` passed to the most
715	/// recent call is scheduled to receive a wakeup. (However,
716	/// `poll_send_ready` retains a second, independent waker.)
717	///
718	/// This function is intended for cases where creating and pinning a future
719	/// via [`readable`] is not feasible. Where possible, using [`readable`] is
720	/// preferred, as this supports polling from multiple tasks at once.
721	///
722	/// # Return value
723	///
724	/// The function returns:
725	///
726	/// `Poll::Pending` if the udp stream is not ready for reading.*
727	/// `Poll::Ready(Ok(()))` if the udp stream is ready for reading.*
728	/// `Poll::Ready(Err(e))` if an error is encountered.*
729	///
730	/// # Errors
731	///
732	/// This function may encounter any standard I/O error except `WouldBlock`.
733	///
734	/// [`readable`]: method@Self::readable
735	pub fn poll_recv_ready(&self, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
736	self.io.registration().poll_read_ready(cx).map_ok(\|_\| ())
737	}
738
739	/// Receives a single datagram message on the socket from the remote address
740	/// to which it is connected. On success, returns the number of bytes read.
741	///
742	/// The function must be called with valid byte array `buf` of sufficient
743	/// size to hold the message bytes. If a message is too long to fit in the
744	/// supplied buffer, excess bytes may be discarded.
745	///
746	/// The [`connect`] method will connect this socket to a remote address.
747	/// This method will fail if the socket is not connected.
748	///
749	/// # Cancel safety
750	///
751	/// This method is cancel safe. If `recv` is used as the event in a
752	/// [`tokio::select!`](crate::select) statement and some other branch
753	/// completes first, it is guaranteed that no messages were received on this
754	/// socket.
755	///
756	/// [`connect`]: method@Self::connect
757	///
758	/// ```no_run
759	/// use tokio::net::UdpSocket;
760	/// use std::io;
761	///
762	/// #[tokio::main]
763	/// async fn main() -> io::Result<()> {
764	/// // Bind socket
765	/// let socket = UdpSocket::bind("127.0.0.1:8080").await?;
766	/// socket.connect("127.0.0.1:8081").await?;
767	///
768	/// let mut buf = vec![`0`; `10`];
769	/// let n = socket.recv(&mut buf).await?;
770	///
771	/// println!("received {} bytes {:?}", n, &buf[..n]);
772	///
773	/// Ok(())
774	/// }
775	/// ```
776	pub async fn recv(&self, buf: &mut [u8]) -> io::Result<usize> {
777	self.io
778	.registration()
779	.async_io(Interest::READABLE, \|\| self.io.recv(buf))
780	.await
781	}
782
783	/// Attempts to receive a single datagram message on the socket from the remote
784	/// address to which it is `connect`ed.
785	///
786	/// The [`connect`] method will connect this socket to a remote address. This method
787	/// resolves to an error if the socket is not connected.
788	///
789	/// Note that on multiple calls to a `poll_` method in the recv direction, only the*
790	/// `Waker` from the `Context` passed to the most recent call will be scheduled to
791	/// receive a wakeup.
792	///
793	/// # Return value
794	///
795	/// The function returns:
796	///
797	/// `Poll::Pending` if the socket is not ready to read*
798	/// `Poll::Ready(Ok(()))` reads data `ReadBuf` if the socket is ready*
799	/// `Poll::Ready(Err(e))` if an error is encountered.*
800	///
801	/// # Errors
802	///
803	/// This function may encounter any standard I/O error except `WouldBlock`.
804	///
805	/// [`connect`]: method@Self::connect
806	pub fn poll_recv(&self, cx: &mut Context<'_>, buf: &mut ReadBuf<'_>) -> Poll<io::Result<()>> {
807	let n = ready!(self.io.registration().poll_read_io(cx, \|\| {
808	// Safety: will not read the maybe uninitialized bytes.
809	let b = unsafe {
810	&mut (buf.unfilled_mut() as mut [std::mem::MaybeUninit<u8>] as *mut [u8])
811	};
812
813	self.io.recv(b)
814	}))?;
815
816	// Safety: We trust `recv` to have filled up `n` bytes in the buffer.
817	unsafe {
818	buf.assume_init(n);
819	}
820	buf.advance(n);
821	Poll::Ready(Ok(()))
822	}
823
824	/// Tries to receive a single datagram message on the socket from the remote
825	/// address to which it is connected. On success, returns the number of
826	/// bytes read.
827	///
828	/// This method must be called with valid byte array buf of sufficient size
829	/// to hold the message bytes. If a message is too long to fit in the
830	/// supplied buffer, excess bytes may be discarded.
831	///
832	/// When there is no pending data, `Err(io::ErrorKind::WouldBlock)` is
833	/// returned. This function is usually paired with `readable()`.
834	///
835	/// # Examples
836	///
837	/// ```no_run
838	/// use tokio::net::UdpSocket;
839	/// use std::io;
840	///
841	/// #[tokio::main]
842	/// async fn main() -> io::Result<()> {
843	/// // Connect to a peer
844	/// let socket = UdpSocket::bind("127.0.0.1:8080").await?;
845	/// socket.connect("127.0.0.1:8081").await?;
846	///
847	/// loop {
848	/// // Wait for the socket to be readable
849	/// socket.readable().await?;
850	///
851	/// // The buffer is not* included in the async task and will*
852	/// // only exist on the stack.
853	/// let mut buf = [`0`; `1024`];
854	///
855	/// // Try to recv data, this may still fail with `WouldBlock`
856	/// // if the readiness event is a false positive.
857	/// match socket.try_recv(&mut buf) {
858	/// Ok(n) => {
859	/// println!("GOT {:?}", &buf[..n]);
860	/// break;
861	/// }
862	/// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
863	/// continue;
864	/// }
865	/// Err(e) => {
866	/// return Err(e);
867	/// }
868	/// }
869	/// }
870	///
871	/// Ok(())
872	/// }
873	/// ```
874	pub fn try_recv(&self, buf: &mut [u8]) -> io::Result<usize> {
875	self.io
876	.registration()
877	.try_io(Interest::READABLE, \|\| self.io.recv(buf))
878	}
879
880	cfg_io_util! {
881	/// Tries to receive data from the stream into the provided buffer, advancing the
882	/// buffer's internal cursor, returning how many bytes were read.
883	///
884	/// This method must be called with valid byte array buf of sufficient size
885	/// to hold the message bytes. If a message is too long to fit in the
886	/// supplied buffer, excess bytes may be discarded.
887	///
888	/// This method can be used even if `buf` is uninitialized.
889	///
890	/// When there is no pending data, `Err(io::ErrorKind::WouldBlock)` is
891	/// returned. This function is usually paired with `readable()`.
892	///
893	/// # Examples
894	///
895	/// ```no_run
896	/// use tokio::net::UdpSocket;
897	/// use std::io;
898	///
899	/// #[tokio::main]
900	/// async fn main() -> io::Result<()> {
901	/// // Connect to a peer
902	/// let socket = UdpSocket::bind("127.0.0.1:8080").await?;
903	/// socket.connect("127.0.0.1:8081").await?;
904	///
905	/// loop {
906	/// // Wait for the socket to be readable
907	/// socket.readable().await?;
908	///
909	/// let mut buf = Vec::with_capacity(1024);
910	///
911	/// // Try to recv data, this may still fail with `WouldBlock`
912	/// // if the readiness event is a false positive.
913	/// match socket.try_recv_buf(&mut buf) {
914	/// Ok(n) => {
915	/// println!("GOT {:?}", &buf[..n]);
916	/// break;
917	/// }
918	/// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
919	/// continue;
920	/// }
921	/// Err(e) => {
922	/// return Err(e);
923	/// }
924	/// }
925	/// }
926	///
927	/// Ok(())
928	/// }
929	/// ```
930	pub fn try_recv_buf<B: BufMut>(&self, buf: &mut B) -> io::Result<usize> {
931	self.io.registration().try_io(Interest::READABLE, \|\| {
932	let dst = buf.chunk_mut();
933	let dst =
934	unsafe { &mut (dst as mut _ as *mut [std::mem::MaybeUninit<u8>] as *mut [u8]) };
935
936	let n = (*self.io).recv(dst)?;
937
938	// Safety: We trust `UdpSocket::recv` to have filled up `n` bytes in the
939	// buffer.
940	unsafe {
941	buf.advance_mut(n);
942	}
943
944	Ok(n)
945	})
946	}
947
948	/// Receives a single datagram message on the socket from the remote address
949	/// to which it is connected, advancing the buffer's internal cursor,
950	/// returning how many bytes were read.
951	///
952	/// This method must be called with valid byte array buf of sufficient size
953	/// to hold the message bytes. If a message is too long to fit in the
954	/// supplied buffer, excess bytes may be discarded.
955	///
956	/// This method can be used even if `buf` is uninitialized.
957	///
958	/// # Examples
959	///
960	/// ```no_run
961	/// use tokio::net::UdpSocket;
962	/// use std::io;
963	///
964	/// #[tokio::main]
965	/// async fn main() -> io::Result<()> {
966	/// // Connect to a peer
967	/// let socket = UdpSocket::bind("127.0.0.1:8080").await?;
968	/// socket.connect("127.0.0.1:8081").await?;
969	///
970	/// let mut buf = Vec::with_capacity(512);
971	/// let len = socket.recv_buf(&mut buf).await?;
972	///
973	/// println!("received {} bytes {:?}", len, &buf[..len]);
974	///
975	/// Ok(())
976	/// }
977	/// ```
978	pub async fn recv_buf<B: BufMut>(&self, buf: &mut B) -> io::Result<usize> {
979	self.io.registration().async_io(Interest::READABLE, \|\| {
980	let dst = buf.chunk_mut();
981	let dst =
982	unsafe { &mut (dst as mut _ as *mut [std::mem::MaybeUninit<u8>] as *mut [u8]) };
983
984	let n = (*self.io).recv(dst)?;
985
986	// Safety: We trust `UdpSocket::recv` to have filled up `n` bytes in the
987	// buffer.
988	unsafe {
989	buf.advance_mut(n);
990	}
991
992	Ok(n)
993	}).await
994	}
995
996	/// Tries to receive a single datagram message on the socket. On success,
997	/// returns the number of bytes read and the origin.
998	///
999	/// This method must be called with valid byte array buf of sufficient size
1000	/// to hold the message bytes. If a message is too long to fit in the
1001	/// supplied buffer, excess bytes may be discarded.
1002	///
1003	/// This method can be used even if `buf` is uninitialized.
1004	///
1005	/// When there is no pending data, `Err(io::ErrorKind::WouldBlock)` is
1006	/// returned. This function is usually paired with `readable()`.
1007	///
1008	/// # Notes
1009	/// Note that the socket address cannot* be implicitly trusted, because it is relatively*
1010	/// trivial to send a UDP datagram with a spoofed origin in a [packet injection attack].
1011	/// Because UDP is stateless and does not validate the origin of a packet,
1012	/// the attacker does not need to be able to intercept traffic in order to interfere.
1013	/// It is important to be aware of this when designing your application-level protocol.
1014	///
1015	/// [packet injection attack]: https://en.wikipedia.org/wiki/Packet_injection
1016	///
1017	/// # Examples
1018	///
1019	/// ```no_run
1020	/// use tokio::net::UdpSocket;
1021	/// use std::io;
1022	///
1023	/// #[tokio::main]
1024	/// async fn main() -> io::Result<()> {
1025	/// // Connect to a peer
1026	/// let socket = UdpSocket::bind("127.0.0.1:8080").await?;
1027	///
1028	/// loop {
1029	/// // Wait for the socket to be readable
1030	/// socket.readable().await?;
1031	///
1032	/// let mut buf = Vec::with_capacity(1024);
1033	///
1034	/// // Try to recv data, this may still fail with `WouldBlock`
1035	/// // if the readiness event is a false positive.
1036	/// match socket.try_recv_buf_from(&mut buf) {
1037	/// Ok((n, _addr)) => {
1038	/// println!("GOT {:?}", &buf[..n]);
1039	/// break;
1040	/// }
1041	/// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
1042	/// continue;
1043	/// }
1044	/// Err(e) => {
1045	/// return Err(e);
1046	/// }
1047	/// }
1048	/// }
1049	///
1050	/// Ok(())
1051	/// }
1052	/// ```
1053	pub fn try_recv_buf_from<B: BufMut>(&self, buf: &mut B) -> io::Result<(usize, SocketAddr)> {
1054	self.io.registration().try_io(Interest::READABLE, \|\| {
1055	let dst = buf.chunk_mut();
1056	let dst =
1057	unsafe { &mut (dst as mut _ as *mut [std::mem::MaybeUninit<u8>] as *mut [u8]) };
1058
1059	let (n, addr) = (*self.io).recv_from(dst)?;
1060
1061	// Safety: We trust `UdpSocket::recv_from` to have filled up `n` bytes in the
1062	// buffer.
1063	unsafe {
1064	buf.advance_mut(n);
1065	}
1066
1067	Ok((n, addr))
1068	})
1069	}
1070
1071	/// Receives a single datagram message on the socket, advancing the
1072	/// buffer's internal cursor, returning how many bytes were read and the origin.
1073	///
1074	/// This method must be called with valid byte array buf of sufficient size
1075	/// to hold the message bytes. If a message is too long to fit in the
1076	/// supplied buffer, excess bytes may be discarded.
1077	///
1078	/// This method can be used even if `buf` is uninitialized.
1079	///
1080	/// # Notes
1081	/// Note that the socket address cannot* be implicitly trusted, because it is relatively*
1082	/// trivial to send a UDP datagram with a spoofed origin in a [packet injection attack].
1083	/// Because UDP is stateless and does not validate the origin of a packet,
1084	/// the attacker does not need to be able to intercept traffic in order to interfere.
1085	/// It is important to be aware of this when designing your application-level protocol.
1086	///
1087	/// [packet injection attack]: https://en.wikipedia.org/wiki/Packet_injection
1088	///
1089	/// # Examples
1090	///
1091	/// ```no_run
1092	/// use tokio::net::UdpSocket;
1093	/// use std::io;
1094	///
1095	/// #[tokio::main]
1096	/// async fn main() -> io::Result<()> {
1097	/// // Connect to a peer
1098	/// let socket = UdpSocket::bind("127.0.0.1:8080").await?;
1099	/// socket.connect("127.0.0.1:8081").await?;
1100	///
1101	/// let mut buf = Vec::with_capacity(512);
1102	/// let (len, addr) = socket.recv_buf_from(&mut buf).await?;
1103	///
1104	/// println!("received {:?} bytes from {:?}", len, addr);
1105	///
1106	/// Ok(())
1107	/// }
1108	/// ```
1109	pub async fn recv_buf_from<B: BufMut>(&self, buf: &mut B) -> io::Result<(usize, SocketAddr)> {
1110	self.io.registration().async_io(Interest::READABLE, \|\| {
1111	let dst = buf.chunk_mut();
1112	let dst =
1113	unsafe { &mut (dst as mut _ as *mut [std::mem::MaybeUninit<u8>] as *mut [u8]) };
1114
1115	let (n, addr) = (*self.io).recv_from(dst)?;
1116
1117	// Safety: We trust `UdpSocket::recv_from` to have filled up `n` bytes in the
1118	// buffer.
1119	unsafe {
1120	buf.advance_mut(n);
1121	}
1122
1123	Ok((n,addr))
1124	}).await
1125	}
1126	}
1127
1128	/// Sends data on the socket to the given address. On success, returns the
1129	/// number of bytes written.
1130	///
1131	/// Address type can be any implementor of [`ToSocketAddrs`] trait. See its
1132	/// documentation for concrete examples.
1133	///
1134	/// It is possible for `addr` to yield multiple addresses, but `send_to`
1135	/// will only send data to the first address yielded by `addr`.
1136	///
1137	/// This will return an error when the IP version of the local socket does
1138	/// not match that returned from [`ToSocketAddrs`].
1139	///
1140	/// [`ToSocketAddrs`]: crate::net::ToSocketAddrs
1141	///
1142	/// # Cancel safety
1143	///
1144	/// This method is cancel safe. If `send_to` is used as the event in a
1145	/// [`tokio::select!`](crate::select) statement and some other branch
1146	/// completes first, then it is guaranteed that the message was not sent.
1147	///
1148	/// # Example
1149	///
1150	/// ```no_run
1151	/// use tokio::net::UdpSocket;
1152	/// use std::io;
1153	///
1154	/// #[tokio::main]
1155	/// async fn main() -> io::Result<()> {
1156	/// let socket = UdpSocket::bind("127.0.0.1:8080").await?;
1157	/// let len = socket.send_to(b"hello world", "127.0.0.1:8081").await?;
1158	///
1159	/// println!("Sent {} bytes", len);
1160	///
1161	/// Ok(())
1162	/// }
1163	/// ```
1164	pub async fn send_to<A: ToSocketAddrs>(&self, buf: &[u8], target: A) -> io::Result<usize> {
1165	let mut addrs = to_socket_addrs(target).await?;
1166
1167	match addrs.next() {
1168	Some(target) => self.send_to_addr(buf, target).await,
1169	None => Err(io::Error::new(
1170	io::ErrorKind::InvalidInput,
1171	"no addresses to send data to",
1172	)),
1173	}
1174	}
1175
1176	/// Attempts to send data on the socket to a given address.
1177	///
1178	/// Note that on multiple calls to a `poll_` method in the send direction, only the*
1179	/// `Waker` from the `Context` passed to the most recent call will be scheduled to
1180	/// receive a wakeup.
1181	///
1182	/// # Return value
1183	///
1184	/// The function returns:
1185	///
1186	/// `Poll::Pending` if the socket is not ready to write*
1187	/// `Poll::Ready(Ok(n))` `n` is the number of bytes sent.*
1188	/// `Poll::Ready(Err(e))` if an error is encountered.*
1189	///
1190	/// # Errors
1191	///
1192	/// This function may encounter any standard I/O error except `WouldBlock`.
1193	pub fn poll_send_to(
1194	&self,
1195	cx: &mut Context<'_>,
1196	buf: &[u8],
1197	target: SocketAddr,
1198	) -> Poll<io::Result<usize>> {
1199	self.io
1200	.registration()
1201	.poll_write_io(cx, \|\| self.io.send_to(buf, target))
1202	}
1203
1204	/// Tries to send data on the socket to the given address, but if the send is
1205	/// blocked this will return right away.
1206	///
1207	/// This function is usually paired with `writable()`.
1208	///
1209	/// # Returns
1210	///
1211	/// If successful, returns the number of bytes sent
1212	///
1213	/// Users should ensure that when the remote cannot receive, the
1214	/// [`ErrorKind::WouldBlock`] is properly handled. An error can also occur
1215	/// if the IP version of the socket does not match that of `target`.
1216	///
1217	/// [`ErrorKind::WouldBlock`]: std::io::ErrorKind::WouldBlock
1218	///
1219	/// # Example
1220	///
1221	/// ```no_run
1222	/// use tokio::net::UdpSocket;
1223	/// use std::error::Error;
1224	/// use std::io;
1225	///
1226	/// #[tokio::main]
1227	/// async fn main() -> Result<(), Box<dyn Error>> {
1228	/// let socket = UdpSocket::bind("127.0.0.1:8080").await?;
1229	///
1230	/// let dst = "127.0.0.1:8081".parse()?;
1231	///
1232	/// loop {
1233	/// socket.writable().await?;
1234	///
1235	/// match socket.try_send_to(&b"hello world"[..], dst) {
1236	/// Ok(sent) => {
1237	/// println!("sent {} bytes", sent);
1238	/// break;
1239	/// }
1240	/// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
1241	/// // Writable false positive.
1242	/// continue;
1243	/// }
1244	/// Err(e) => return Err(e.into()),
1245	/// }
1246	/// }
1247	///
1248	/// Ok(())
1249	/// }
1250	/// ```
1251	pub fn try_send_to(&self, buf: &[u8], target: SocketAddr) -> io::Result<usize> {
1252	self.io
1253	.registration()
1254	.try_io(Interest::WRITABLE, \|\| self.io.send_to(buf, target))
1255	}
1256
1257	async fn send_to_addr(&self, buf: &[u8], target: SocketAddr) -> io::Result<usize> {
1258	self.io
1259	.registration()
1260	.async_io(Interest::WRITABLE, \|\| self.io.send_to(buf, target))
1261	.await
1262	}
1263
1264	/// Receives a single datagram message on the socket. On success, returns
1265	/// the number of bytes read and the origin.
1266	///
1267	/// The function must be called with valid byte array `buf` of sufficient
1268	/// size to hold the message bytes. If a message is too long to fit in the
1269	/// supplied buffer, excess bytes may be discarded.
1270	///
1271	/// # Cancel safety
1272	///
1273	/// This method is cancel safe. If `recv_from` is used as the event in a
1274	/// [`tokio::select!`](crate::select) statement and some other branch
1275	/// completes first, it is guaranteed that no messages were received on this
1276	/// socket.
1277	///
1278	/// # Example
1279	///
1280	/// ```no_run
1281	/// use tokio::net::UdpSocket;
1282	/// use std::io;
1283	///
1284	/// #[tokio::main]
1285	/// async fn main() -> io::Result<()> {
1286	/// let socket = UdpSocket::bind("127.0.0.1:8080").await?;
1287	///
1288	/// let mut buf = vec![`0u8`; `32`];
1289	/// let (len, addr) = socket.recv_from(&mut buf).await?;
1290	///
1291	/// println!("received {:?} bytes from {:?}", len, addr);
1292	///
1293	/// Ok(())
1294	/// }
1295	/// ```
1296	///
1297	/// # Notes
1298	/// Note that the socket address cannot* be implicitly trusted, because it is relatively*
1299	/// trivial to send a UDP datagram with a spoofed origin in a [packet injection attack].
1300	/// Because UDP is stateless and does not validate the origin of a packet,
1301	/// the attacker does not need to be able to intercept traffic in order to interfere.
1302	/// It is important to be aware of this when designing your application-level protocol.
1303	///
1304	/// [packet injection attack]: https://en.wikipedia.org/wiki/Packet_injection
1305	pub async fn recv_from(&self, buf: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
1306	self.io
1307	.registration()
1308	.async_io(Interest::READABLE, \|\| self.io.recv_from(buf))
1309	.await
1310	}
1311
1312	/// Attempts to receive a single datagram on the socket.
1313	///
1314	/// Note that on multiple calls to a `poll_` method in the recv direction, only the*
1315	/// `Waker` from the `Context` passed to the most recent call will be scheduled to
1316	/// receive a wakeup.
1317	///
1318	/// # Return value
1319	///
1320	/// The function returns:
1321	///
1322	/// `Poll::Pending` if the socket is not ready to read*
1323	/// `Poll::Ready(Ok(addr))` reads data from `addr` into `ReadBuf` if the socket is ready*
1324	/// `Poll::Ready(Err(e))` if an error is encountered.*
1325	///
1326	/// # Errors
1327	///
1328	/// This function may encounter any standard I/O error except `WouldBlock`.
1329	///
1330	/// # Notes
1331	/// Note that the socket address cannot* be implicitly trusted, because it is relatively*
1332	/// trivial to send a UDP datagram with a spoofed origin in a [packet injection attack].
1333	/// Because UDP is stateless and does not validate the origin of a packet,
1334	/// the attacker does not need to be able to intercept traffic in order to interfere.
1335	/// It is important to be aware of this when designing your application-level protocol.
1336	///
1337	/// [packet injection attack]: https://en.wikipedia.org/wiki/Packet_injection
1338	pub fn poll_recv_from(
1339	&self,
1340	cx: &mut Context<'_>,
1341	buf: &mut ReadBuf<'_>,
1342	) -> Poll<io::Result<SocketAddr>> {
1343	let (n, addr) = ready!(self.io.registration().poll_read_io(cx, \|\| {
1344	// Safety: will not read the maybe uninitialized bytes.
1345	let b = unsafe {
1346	&mut (buf.unfilled_mut() as mut [std::mem::MaybeUninit<u8>] as *mut [u8])
1347	};
1348
1349	self.io.recv_from(b)
1350	}))?;
1351
1352	// Safety: We trust `recv` to have filled up `n` bytes in the buffer.
1353	unsafe {
1354	buf.assume_init(n);
1355	}
1356	buf.advance(n);
1357	Poll::Ready(Ok(addr))
1358	}
1359
1360	/// Tries to receive a single datagram message on the socket. On success,
1361	/// returns the number of bytes read and the origin.
1362	///
1363	/// This method must be called with valid byte array buf of sufficient size
1364	/// to hold the message bytes. If a message is too long to fit in the
1365	/// supplied buffer, excess bytes may be discarded.
1366	///
1367	/// When there is no pending data, `Err(io::ErrorKind::WouldBlock)` is
1368	/// returned. This function is usually paired with `readable()`.
1369	///
1370	/// # Notes
1371	///
1372	/// Note that the socket address cannot* be implicitly trusted, because it is relatively*
1373	/// trivial to send a UDP datagram with a spoofed origin in a [packet injection attack].
1374	/// Because UDP is stateless and does not validate the origin of a packet,
1375	/// the attacker does not need to be able to intercept traffic in order to interfere.
1376	/// It is important to be aware of this when designing your application-level protocol.
1377	///
1378	/// [packet injection attack]: https://en.wikipedia.org/wiki/Packet_injection
1379	///
1380	/// # Examples
1381	///
1382	/// ```no_run
1383	/// use tokio::net::UdpSocket;
1384	/// use std::io;
1385	///
1386	/// #[tokio::main]
1387	/// async fn main() -> io::Result<()> {
1388	/// // Connect to a peer
1389	/// let socket = UdpSocket::bind("127.0.0.1:8080").await?;
1390	///
1391	/// loop {
1392	/// // Wait for the socket to be readable
1393	/// socket.readable().await?;
1394	///
1395	/// // The buffer is not* included in the async task and will*
1396	/// // only exist on the stack.
1397	/// let mut buf = [`0`; `1024`];
1398	///
1399	/// // Try to recv data, this may still fail with `WouldBlock`
1400	/// // if the readiness event is a false positive.
1401	/// match socket.try_recv_from(&mut buf) {
1402	/// Ok((n, _addr)) => {
1403	/// println!("GOT {:?}", &buf[..n]);
1404	/// break;
1405	/// }
1406	/// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
1407	/// continue;
1408	/// }
1409	/// Err(e) => {
1410	/// return Err(e);
1411	/// }
1412	/// }
1413	/// }
1414	///
1415	/// Ok(())
1416	/// }
1417	/// ```
1418	pub fn try_recv_from(&self, buf: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
1419	self.io
1420	.registration()
1421	.try_io(Interest::READABLE, \|\| self.io.recv_from(buf))
1422	}
1423
1424	/// Tries to read or write from the socket using a user-provided IO operation.
1425	///
1426	/// If the socket is ready, the provided closure is called. The closure
1427	/// should attempt to perform IO operation on the socket by manually
1428	/// calling the appropriate syscall. If the operation fails because the
1429	/// socket is not actually ready, then the closure should return a
1430	/// `WouldBlock` error and the readiness flag is cleared. The return value
1431	/// of the closure is then returned by `try_io`.
1432	///
1433	/// If the socket is not ready, then the closure is not called
1434	/// and a `WouldBlock` error is returned.
1435	///
1436	/// The closure should only return a `WouldBlock` error if it has performed
1437	/// an IO operation on the socket that failed due to the socket not being
1438	/// ready. Returning a `WouldBlock` error in any other situation will
1439	/// incorrectly clear the readiness flag, which can cause the socket to
1440	/// behave incorrectly.
1441	///
1442	/// The closure should not perform the IO operation using any of the methods
1443	/// defined on the Tokio `UdpSocket` type, as this will mess with the
1444	/// readiness flag and can cause the socket to behave incorrectly.
1445	///
1446	/// This method is not intended to be used with combined interests.
1447	/// The closure should perform only one type of IO operation, so it should not
1448	/// require more than one ready state. This method may panic or sleep forever
1449	/// if it is called with a combined interest.
1450	///
1451	/// Usually, [`readable()`], [`writable()`] or [`ready()`] is used with this function.
1452	///
1453	/// [`readable()`]: UdpSocket::readable()
1454	/// [`writable()`]: UdpSocket::writable()
1455	/// [`ready()`]: UdpSocket::ready()
1456	pub fn try_io<R>(
1457	&self,
1458	interest: Interest,
1459	f: impl FnOnce() -> io::Result<R>,
1460	) -> io::Result<R> {
1461	self.io
1462	.registration()
1463	.try_io(interest, \|\| self.io.try_io(f))
1464	}
1465
1466	/// Reads or writes from the socket using a user-provided IO operation.
1467	///
1468	/// The readiness of the socket is awaited and when the socket is ready,
1469	/// the provided closure is called. The closure should attempt to perform
1470	/// IO operation on the socket by manually calling the appropriate syscall.
1471	/// If the operation fails because the socket is not actually ready,
1472	/// then the closure should return a `WouldBlock` error. In such case the
1473	/// readiness flag is cleared and the socket readiness is awaited again.
1474	/// This loop is repeated until the closure returns an `Ok` or an error
1475	/// other than `WouldBlock`.
1476	///
1477	/// The closure should only return a `WouldBlock` error if it has performed
1478	/// an IO operation on the socket that failed due to the socket not being
1479	/// ready. Returning a `WouldBlock` error in any other situation will
1480	/// incorrectly clear the readiness flag, which can cause the socket to
1481	/// behave incorrectly.
1482	///
1483	/// The closure should not perform the IO operation using any of the methods
1484	/// defined on the Tokio `UdpSocket` type, as this will mess with the
1485	/// readiness flag and can cause the socket to behave incorrectly.
1486	///
1487	/// This method is not intended to be used with combined interests.
1488	/// The closure should perform only one type of IO operation, so it should not
1489	/// require more than one ready state. This method may panic or sleep forever
1490	/// if it is called with a combined interest.
1491	pub async fn async_io<R>(
1492	&self,
1493	interest: Interest,
1494	mut f: impl FnMut() -> io::Result<R>,
1495	) -> io::Result<R> {
1496	self.io
1497	.registration()
1498	.async_io(interest, \|\| self.io.try_io(&mut f))
1499	.await
1500	}
1501
1502	/// Receives data from the socket, without removing it from the input queue.
1503	/// On success, returns the number of bytes read and the address from whence
1504	/// the data came.
1505	///
1506	/// # Notes
1507	///
1508	/// On Windows, if the data is larger than the buffer specified, the buffer
1509	/// is filled with the first part of the data, and `peek_from` returns the error
1510	/// WSAEMSGSIZE(10040). The excess data is lost.
1511	/// Make sure to always use a sufficiently large buffer to hold the
1512	/// maximum UDP packet size, which can be up to 65536 bytes in size.
1513	///
1514	/// MacOS will return an error if you pass a zero-sized buffer.
1515	///
1516	/// If you're merely interested in learning the sender of the data at the head of the queue,
1517	/// try [`peek_sender`].
1518	///
1519	/// Note that the socket address cannot* be implicitly trusted, because it is relatively*
1520	/// trivial to send a UDP datagram with a spoofed origin in a [packet injection attack].
1521	/// Because UDP is stateless and does not validate the origin of a packet,
1522	/// the attacker does not need to be able to intercept traffic in order to interfere.
1523	/// It is important to be aware of this when designing your application-level protocol.
1524	///
1525	/// # Examples
1526	///
1527	/// ```no_run
1528	/// use tokio::net::UdpSocket;
1529	/// use std::io;
1530	///
1531	/// #[tokio::main]
1532	/// async fn main() -> io::Result<()> {
1533	/// let socket = UdpSocket::bind("127.0.0.1:8080").await?;
1534	///
1535	/// let mut buf = vec![`0u8`; `32`];
1536	/// let (len, addr) = socket.peek_from(&mut buf).await?;
1537	///
1538	/// println!("peeked {:?} bytes from {:?}", len, addr);
1539	///
1540	/// Ok(())
1541	/// }
1542	/// ```
1543	///
1544	/// [`peek_sender`]: method@Self::peek_sender
1545	/// [packet injection attack]: https://en.wikipedia.org/wiki/Packet_injection
1546	pub async fn peek_from(&self, buf: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
1547	self.io
1548	.registration()
1549	.async_io(Interest::READABLE, \|\| self.io.peek_from(buf))
1550	.await
1551	}
1552
1553	/// Receives data from the socket, without removing it from the input queue.
1554	/// On success, returns the sending address of the datagram.
1555	///
1556	/// # Notes
1557	///
1558	/// Note that on multiple calls to a `poll_` method in the recv direction, only the*
1559	/// `Waker` from the `Context` passed to the most recent call will be scheduled to
1560	/// receive a wakeup
1561	///
1562	/// On Windows, if the data is larger than the buffer specified, the buffer
1563	/// is filled with the first part of the data, and peek returns the error
1564	/// WSAEMSGSIZE(10040). The excess data is lost.
1565	/// Make sure to always use a sufficiently large buffer to hold the
1566	/// maximum UDP packet size, which can be up to 65536 bytes in size.
1567	///
1568	/// MacOS will return an error if you pass a zero-sized buffer.
1569	///
1570	/// If you're merely interested in learning the sender of the data at the head of the queue,
1571	/// try [`poll_peek_sender`].
1572	///
1573	/// Note that the socket address cannot* be implicitly trusted, because it is relatively*
1574	/// trivial to send a UDP datagram with a spoofed origin in a [packet injection attack].
1575	/// Because UDP is stateless and does not validate the origin of a packet,
1576	/// the attacker does not need to be able to intercept traffic in order to interfere.
1577	/// It is important to be aware of this when designing your application-level protocol.
1578	///
1579	/// # Return value
1580	///
1581	/// The function returns:
1582	///
1583	/// `Poll::Pending` if the socket is not ready to read*
1584	/// `Poll::Ready(Ok(addr))` reads data from `addr` into `ReadBuf` if the socket is ready*
1585	/// `Poll::Ready(Err(e))` if an error is encountered.*
1586	///
1587	/// # Errors
1588	///
1589	/// This function may encounter any standard I/O error except `WouldBlock`.
1590	///
1591	/// [`poll_peek_sender`]: method@Self::poll_peek_sender
1592	/// [packet injection attack]: https://en.wikipedia.org/wiki/Packet_injection
1593	pub fn poll_peek_from(
1594	&self,
1595	cx: &mut Context<'_>,
1596	buf: &mut ReadBuf<'_>,
1597	) -> Poll<io::Result<SocketAddr>> {
1598	let (n, addr) = ready!(self.io.registration().poll_read_io(cx, \|\| {
1599	// Safety: will not read the maybe uninitialized bytes.
1600	let b = unsafe {
1601	&mut (buf.unfilled_mut() as mut [std::mem::MaybeUninit<u8>] as *mut [u8])
1602	};
1603
1604	self.io.peek_from(b)
1605	}))?;
1606
1607	// Safety: We trust `recv` to have filled up `n` bytes in the buffer.
1608	unsafe {
1609	buf.assume_init(n);
1610	}
1611	buf.advance(n);
1612	Poll::Ready(Ok(addr))
1613	}
1614
1615	/// Tries to receive data on the socket without removing it from the input queue.
1616	/// On success, returns the number of bytes read and the sending address of the
1617	/// datagram.
1618	///
1619	/// When there is no pending data, `Err(io::ErrorKind::WouldBlock)` is
1620	/// returned. This function is usually paired with `readable()`.
1621	///
1622	/// # Notes
1623	///
1624	/// On Windows, if the data is larger than the buffer specified, the buffer
1625	/// is filled with the first part of the data, and peek returns the error
1626	/// WSAEMSGSIZE(10040). The excess data is lost.
1627	/// Make sure to always use a sufficiently large buffer to hold the
1628	/// maximum UDP packet size, which can be up to 65536 bytes in size.
1629	///
1630	/// MacOS will return an error if you pass a zero-sized buffer.
1631	///
1632	/// If you're merely interested in learning the sender of the data at the head of the queue,
1633	/// try [`try_peek_sender`].
1634	///
1635	/// Note that the socket address cannot* be implicitly trusted, because it is relatively*
1636	/// trivial to send a UDP datagram with a spoofed origin in a [packet injection attack].
1637	/// Because UDP is stateless and does not validate the origin of a packet,
1638	/// the attacker does not need to be able to intercept traffic in order to interfere.
1639	/// It is important to be aware of this when designing your application-level protocol.
1640	///
1641	/// [`try_peek_sender`]: method@Self::try_peek_sender
1642	/// [packet injection attack]: https://en.wikipedia.org/wiki/Packet_injection
1643	pub fn try_peek_from(&self, buf: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
1644	self.io
1645	.registration()
1646	.try_io(Interest::READABLE, \|\| self.io.peek_from(buf))
1647	}
1648
1649	/// Retrieve the sender of the data at the head of the input queue, waiting if empty.
1650	///
1651	/// This is equivalent to calling [`peek_from`] with a zero-sized buffer,
1652	/// but suppresses the `WSAEMSGSIZE` error on Windows and the "invalid argument" error on macOS.
1653	///
1654	/// Note that the socket address cannot* be implicitly trusted, because it is relatively*
1655	/// trivial to send a UDP datagram with a spoofed origin in a [packet injection attack].
1656	/// Because UDP is stateless and does not validate the origin of a packet,
1657	/// the attacker does not need to be able to intercept traffic in order to interfere.
1658	/// It is important to be aware of this when designing your application-level protocol.
1659	///
1660	/// [`peek_from`]: method@Self::peek_from
1661	/// [packet injection attack]: https://en.wikipedia.org/wiki/Packet_injection
1662	pub async fn peek_sender(&self) -> io::Result<SocketAddr> {
1663	self.io
1664	.registration()
1665	.async_io(Interest::READABLE, \|\| self.peek_sender_inner())
1666	.await
1667	}
1668
1669	/// Retrieve the sender of the data at the head of the input queue,
1670	/// scheduling a wakeup if empty.
1671	///
1672	/// This is equivalent to calling [`poll_peek_from`] with a zero-sized buffer,
1673	/// but suppresses the `WSAEMSGSIZE` error on Windows and the "invalid argument" error on macOS.
1674	///
1675	/// # Notes
1676	///
1677	/// Note that on multiple calls to a `poll_` method in the recv direction, only the*
1678	/// `Waker` from the `Context` passed to the most recent call will be scheduled to
1679	/// receive a wakeup.
1680	///
1681	/// Note that the socket address cannot* be implicitly trusted, because it is relatively*
1682	/// trivial to send a UDP datagram with a spoofed origin in a [packet injection attack].
1683	/// Because UDP is stateless and does not validate the origin of a packet,
1684	/// the attacker does not need to be able to intercept traffic in order to interfere.
1685	/// It is important to be aware of this when designing your application-level protocol.
1686	///
1687	/// [`poll_peek_from`]: method@Self::poll_peek_from
1688	/// [packet injection attack]: https://en.wikipedia.org/wiki/Packet_injection
1689	pub fn poll_peek_sender(&self, cx: &mut Context<'_>) -> Poll<io::Result<SocketAddr>> {
1690	self.io
1691	.registration()
1692	.poll_read_io(cx, \|\| self.peek_sender_inner())
1693	}
1694
1695	/// Try to retrieve the sender of the data at the head of the input queue.
1696	///
1697	/// When there is no pending data, `Err(io::ErrorKind::WouldBlock)` is
1698	/// returned. This function is usually paired with `readable()`.
1699	///
1700	/// Note that the socket address cannot* be implicitly trusted, because it is relatively*
1701	/// trivial to send a UDP datagram with a spoofed origin in a [packet injection attack].
1702	/// Because UDP is stateless and does not validate the origin of a packet,
1703	/// the attacker does not need to be able to intercept traffic in order to interfere.
1704	/// It is important to be aware of this when designing your application-level protocol.
1705	///
1706	/// [packet injection attack]: https://en.wikipedia.org/wiki/Packet_injection
1707	pub fn try_peek_sender(&self) -> io::Result<SocketAddr> {
1708	self.io
1709	.registration()
1710	.try_io(Interest::READABLE, \|\| self.peek_sender_inner())
1711	}
1712
1713	#[inline]
1714	fn peek_sender_inner(&self) -> io::Result<SocketAddr> {
1715	self.io.try_io(\|\| {
1716	self.as_socket()
1717	.peek_sender()?
1718	// May be `None` if the platform doesn't populate the sender for some reason.
1719	// In testing, that only occurred on macOS if you pass a zero-sized buffer,
1720	// but the implementation of `Socket::peek_sender()` covers that.
1721	.as_socket()
1722	.ok_or_else(\|\| io::Error::new(io::ErrorKind::Other, "sender not available"))
1723	})
1724	}
1725
1726	/// Gets the value of the `SO_BROADCAST` option for this socket.
1727	///
1728	/// For more information about this option, see [`set_broadcast`].
1729	///
1730	/// [`set_broadcast`]: method@Self::set_broadcast
1731	pub fn broadcast(&self) -> io::Result<bool> {
1732	self.io.broadcast()
1733	}
1734
1735	/// Sets the value of the `SO_BROADCAST` option for this socket.
1736	///
1737	/// When enabled, this socket is allowed to send packets to a broadcast
1738	/// address.
1739	pub fn set_broadcast(&self, on: bool) -> io::Result<()> {
1740	self.io.set_broadcast(on)
1741	}
1742
1743	/// Gets the value of the `IP_MULTICAST_LOOP` option for this socket.
1744	///
1745	/// For more information about this option, see [`set_multicast_loop_v4`].
1746	///
1747	/// [`set_multicast_loop_v4`]: method@Self::set_multicast_loop_v4
1748	pub fn multicast_loop_v4(&self) -> io::Result<bool> {
1749	self.io.multicast_loop_v4()
1750	}
1751
1752	/// Sets the value of the `IP_MULTICAST_LOOP` option for this socket.
1753	///
1754	/// If enabled, multicast packets will be looped back to the local socket.
1755	///
1756	/// # Note
1757	///
1758	/// This may not have any affect on IPv6 sockets.
1759	pub fn set_multicast_loop_v4(&self, on: bool) -> io::Result<()> {
1760	self.io.set_multicast_loop_v4(on)
1761	}
1762
1763	/// Gets the value of the `IP_MULTICAST_TTL` option for this socket.
1764	///
1765	/// For more information about this option, see [`set_multicast_ttl_v4`].
1766	///
1767	/// [`set_multicast_ttl_v4`]: method@Self::set_multicast_ttl_v4
1768	pub fn multicast_ttl_v4(&self) -> io::Result<u32> {
1769	self.io.multicast_ttl_v4()
1770	}
1771
1772	/// Sets the value of the `IP_MULTICAST_TTL` option for this socket.
1773	///
1774	/// Indicates the time-to-live value of outgoing multicast packets for
1775	/// this socket. The default value is 1 which means that multicast packets
1776	/// don't leave the local network unless explicitly requested.
1777	///
1778	/// # Note
1779	///
1780	/// This may not have any affect on IPv6 sockets.
1781	pub fn set_multicast_ttl_v4(&self, ttl: u32) -> io::Result<()> {
1782	self.io.set_multicast_ttl_v4(ttl)
1783	}
1784
1785	/// Gets the value of the `IPV6_MULTICAST_LOOP` option for this socket.
1786	///
1787	/// For more information about this option, see [`set_multicast_loop_v6`].
1788	///
1789	/// [`set_multicast_loop_v6`]: method@Self::set_multicast_loop_v6
1790	pub fn multicast_loop_v6(&self) -> io::Result<bool> {
1791	self.io.multicast_loop_v6()
1792	}
1793
1794	/// Sets the value of the `IPV6_MULTICAST_LOOP` option for this socket.
1795	///
1796	/// Controls whether this socket sees the multicast packets it sends itself.
1797	///
1798	/// # Note
1799	///
1800	/// This may not have any affect on IPv4 sockets.
1801	pub fn set_multicast_loop_v6(&self, on: bool) -> io::Result<()> {
1802	self.io.set_multicast_loop_v6(on)
1803	}
1804
1805	/// Gets the value of the `IP_TTL` option for this socket.
1806	///
1807	/// For more information about this option, see [`set_ttl`].
1808	///
1809	/// [`set_ttl`]: method@Self::set_ttl
1810	///
1811	/// # Examples
1812	///
1813	/// ```no_run
1814	/// use tokio::net::UdpSocket;
1815	/// # use std::io;
1816	///
1817	/// # async fn dox() -> io::Result<()> {
1818	/// let sock = UdpSocket::bind("127.0.0.1:8080").await?;
1819	///
1820	/// println!("{:?}", sock.ttl()?);
1821	/// # Ok(())
1822	/// # }
1823	/// ```
1824	pub fn ttl(&self) -> io::Result<u32> {
1825	self.io.ttl()
1826	}
1827
1828	/// Sets the value for the `IP_TTL` option on this socket.
1829	///
1830	/// This value sets the time-to-live field that is used in every packet sent
1831	/// from this socket.
1832	///
1833	/// # Examples
1834	///
1835	/// ```no_run
1836	/// use tokio::net::UdpSocket;
1837	/// # use std::io;
1838	///
1839	/// # async fn dox() -> io::Result<()> {
1840	/// let sock = UdpSocket::bind("127.0.0.1:8080").await?;
1841	/// sock.set_ttl(`60`)?;
1842	///
1843	/// # Ok(())
1844	/// # }
1845	/// ```
1846	pub fn set_ttl(&self, ttl: u32) -> io::Result<()> {
1847	self.io.set_ttl(ttl)
1848	}
1849
1850	/// Gets the value of the `IP_TOS` option for this socket.
1851	///
1852	/// For more information about this option, see [`set_tos`].
1853	///
1854	/// NOTE:* On Windows, `IP_TOS` is only supported on [Windows 8+ or*
1855	/// Windows Server 2012+.](https://docs.microsoft.com/en-us/windows/win32/winsock/ipproto-ip-socket-options)
1856	///
1857	/// [`set_tos`]: Self::set_tos
1858	// https://docs.rs/socket2/0.5.3/src/socket2/socket.rs.html#1464
1859	#[cfg(not(any(
1860	target_os = "fuchsia",
1861	target_os = "redox",
1862	target_os = "solaris",
1863	target_os = "illumos",
1864	)))]
1865	#[cfg_attr(
1866	docsrs,
1867	doc(cfg(not(any(
1868	target_os = "fuchsia",
1869	target_os = "redox",
1870	target_os = "solaris",
1871	target_os = "illumos",
1872	))))
1873	)]
1874	pub fn tos(&self) -> io::Result<u32> {
1875	self.as_socket().tos()
1876	}
1877
1878	/// Sets the value for the `IP_TOS` option on this socket.
1879	///
1880	/// This value sets the type-of-service field that is used in every packet
1881	/// sent from this socket.
1882	///
1883	/// NOTE:* On Windows, `IP_TOS` is only supported on [Windows 8+ or*
1884	/// Windows Server 2012+.](https://docs.microsoft.com/en-us/windows/win32/winsock/ipproto-ip-socket-options)
1885	// https://docs.rs/socket2/0.5.3/src/socket2/socket.rs.html#1446
1886	#[cfg(not(any(
1887	target_os = "fuchsia",
1888	target_os = "redox",
1889	target_os = "solaris",
1890	target_os = "illumos",
1891	)))]
1892	#[cfg_attr(
1893	docsrs,
1894	doc(cfg(not(any(
1895	target_os = "fuchsia",
1896	target_os = "redox",
1897	target_os = "solaris",
1898	target_os = "illumos",
1899	))))
1900	)]
1901	pub fn set_tos(&self, tos: u32) -> io::Result<()> {
1902	self.as_socket().set_tos(tos)
1903	}
1904
1905	/// Gets the value for the `SO_BINDTODEVICE` option on this socket
1906	///
1907	/// This value gets the socket-bound device's interface name.
1908	#[cfg(any(target_os = "android", target_os = "fuchsia", target_os = "linux",))]
1909	#[cfg_attr(
1910	docsrs,
1911	doc(cfg(any(target_os = "android", target_os = "fuchsia", target_os = "linux",)))
1912	)]
1913	pub fn device(&self) -> io::Result<Option<Vec<u8>>> {
1914	self.as_socket().device()
1915	}
1916
1917	/// Sets the value for the `SO_BINDTODEVICE` option on this socket
1918	///
1919	/// If a socket is bound to an interface, only packets received from that
1920	/// particular interface are processed by the socket. Note that this only
1921	/// works for some socket types, particularly `AF_INET` sockets.
1922	///
1923	/// If `interface` is `None` or an empty string it removes the binding.
1924	#[cfg(any(target_os = "android", target_os = "fuchsia", target_os = "linux"))]
1925	#[cfg_attr(
1926	docsrs,
1927	doc(cfg(all(any(target_os = "android", target_os = "fuchsia", target_os = "linux"))))
1928	)]
1929	pub fn bind_device(&self, interface: Option<&[u8]>) -> io::Result<()> {
1930	self.as_socket().bind_device(interface)
1931	}
1932
1933	/// Executes an operation of the `IP_ADD_MEMBERSHIP` type.
1934	///
1935	/// This function specifies a new multicast group for this socket to join.
1936	/// The address must be a valid multicast address, and `interface` is the
1937	/// address of the local interface with which the system should join the
1938	/// multicast group. If it's equal to `INADDR_ANY` then an appropriate
1939	/// interface is chosen by the system.
1940	pub fn join_multicast_v4(&self, multiaddr: Ipv4Addr, interface: Ipv4Addr) -> io::Result<()> {
1941	self.io.join_multicast_v4(&multiaddr, &interface)
1942	}
1943
1944	/// Executes an operation of the `IPV6_ADD_MEMBERSHIP` type.
1945	///
1946	/// This function specifies a new multicast group for this socket to join.
1947	/// The address must be a valid multicast address, and `interface` is the
1948	/// index of the interface to join/leave (or 0 to indicate any interface).
1949	pub fn join_multicast_v6(&self, multiaddr: &Ipv6Addr, interface: u32) -> io::Result<()> {
1950	self.io.join_multicast_v6(multiaddr, interface)
1951	}
1952
1953	/// Executes an operation of the `IP_DROP_MEMBERSHIP` type.
1954	///
1955	/// For more information about this option, see [`join_multicast_v4`].
1956	///
1957	/// [`join_multicast_v4`]: method@Self::join_multicast_v4
1958	pub fn leave_multicast_v4(&self, multiaddr: Ipv4Addr, interface: Ipv4Addr) -> io::Result<()> {
1959	self.io.leave_multicast_v4(&multiaddr, &interface)
1960	}
1961
1962	/// Executes an operation of the `IPV6_DROP_MEMBERSHIP` type.
1963	///
1964	/// For more information about this option, see [`join_multicast_v6`].
1965	///
1966	/// [`join_multicast_v6`]: method@Self::join_multicast_v6
1967	pub fn leave_multicast_v6(&self, multiaddr: &Ipv6Addr, interface: u32) -> io::Result<()> {
1968	self.io.leave_multicast_v6(multiaddr, interface)
1969	}
1970
1971	/// Returns the value of the `SO_ERROR` option.
1972	///
1973	/// # Examples
1974	/// ```
1975	/// use tokio::net::UdpSocket;
1976	/// use std::io;
1977	///
1978	/// #[tokio::main]
1979	/// async fn main() -> io::Result<()> {
1980	/// // Create a socket
1981	/// let socket = UdpSocket::bind("0.0.0.0:8080").await?;
1982	///
1983	/// if let Ok(Some(err)) = socket.take_error() {
1984	/// println!("Got error: {:?}", err);
1985	/// }
1986	///
1987	/// Ok(())
1988	/// }
1989	/// ```
1990	pub fn take_error(&self) -> io::Result<Option<io::Error>> {
1991	self.io.take_error()
1992	}
1993	}
1994
1995	impl TryFrom<std::net::UdpSocket> for UdpSocket {
1996	type Error = io::Error;
1997
1998	/// Consumes stream, returning the tokio I/O object.
1999	///
2000	/// This is equivalent to
2001	/// [`UdpSocket::from_std(stream)`](UdpSocket::from_std).
2002	fn try_from(stream: std::net::UdpSocket) -> Result<Self, Self::Error> {
2003	Self::from_std(stream)
2004	}
2005	}
2006
2007	impl fmt::Debug for UdpSocket {
2008	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2009	self.io.fmt(f)
2010	}
2011	}
2012
2013	#[cfg(unix)]
2014	mod sys {
2015	use super::UdpSocket;
2016	use std::os::unix::prelude::*;
2017
2018	impl AsRawFd for UdpSocket {
2019	fn as_raw_fd(&self) -> RawFd {
2020	self.io.as_raw_fd()
2021	}
2022	}
2023
2024	impl AsFd for UdpSocket {
2025	fn as_fd(&self) -> BorrowedFd<'_> {
2026	unsafe { BorrowedFd::borrow_raw(self.as_raw_fd()) }
2027	}
2028	}
2029	}
2030
2031	cfg_windows! {
2032	use crate::os::windows::io::{AsRawSocket, RawSocket};
2033	use crate::os::windows::io::{AsSocket, BorrowedSocket};
2034
2035	impl AsRawSocket for UdpSocket {
2036	fn as_raw_socket(&self) -> RawSocket {
2037	self.io.as_raw_socket()
2038	}
2039	}
2040
2041	impl AsSocket for UdpSocket {
2042	fn as_socket(&self) -> BorrowedSocket<'_> {
2043	unsafe { BorrowedSocket::borrow_raw(self.as_raw_socket()) }
2044	}
2045	}
2046	}
2047