1 //! DNS Resolution used by the `HttpConnector`.
2 //!
3 //! This module contains:
4 //!
5 //! - A [`GaiResolver`](GaiResolver) that is the default resolver for the
6 //! `HttpConnector`.
7 //! - The `Name` type used as an argument to custom resolvers.
8 //!
9 //! # Resolvers are `Service`s
10 //!
11 //! A resolver is just a
12 //! `Service<Name, Response = impl Iterator<Item = SocketAddr>>`.
13 //!
14 //! A simple resolver that ignores the name and always returns a specific
15 //! address:
16 //!
17 //! ```rust,ignore
18 //! use std::{convert::Infallible, iter, net::SocketAddr};
19 //!
20 //! let resolver = tower::service_fn(|_name| async {
21 //! Ok::<_, Infallible>(iter::once(SocketAddr::from(([127, 0, 0, 1], 8080))))
22 //! });
23 //! ```
24 use std::error::Error;
25 use std::future::Future;
26 use std::net::{Ipv4Addr, Ipv6Addr, SocketAddr, SocketAddrV4, SocketAddrV6, ToSocketAddrs};
27 use std::pin::Pin;
28 use std::str::FromStr;
29 use std::task::{Context, Poll};
30 use std::{fmt, io, vec};
31
32 use tokio::task::JoinHandle;
33 use tower_service::Service;
34 use tracing::debug;
35
36 pub(super) use self::sealed::Resolve;
37
38 /// A domain name to resolve into IP addresses.
39 #[derive(Clone, Hash, Eq, PartialEq)]
40 pub struct Name {
41 host: Box<str>,
42 }
43
44 /// A resolver using blocking `getaddrinfo` calls in a threadpool.
45 #[derive(Clone)]
46 pub struct GaiResolver {
47 _priv: (),
48 }
49
50 /// An iterator of IP addresses returned from `getaddrinfo`.
51 pub struct GaiAddrs {
52 inner: SocketAddrs,
53 }
54
55 /// A future to resolve a name returned by `GaiResolver`.
56 pub struct GaiFuture {
57 inner: JoinHandle<Result<SocketAddrs, io::Error>>,
58 }
59
60 impl Name {
new(host: Box<str>) -> Name61 pub(super) fn new(host: Box<str>) -> Name {
62 Name { host }
63 }
64
65 /// View the hostname as a string slice.
as_str(&self) -> &str66 pub fn as_str(&self) -> &str {
67 &self.host
68 }
69 }
70
71 impl fmt::Debug for Name {
fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result72 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
73 fmt::Debug::fmt(&self.host, f)
74 }
75 }
76
77 impl fmt::Display for Name {
fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result78 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
79 fmt::Display::fmt(&self.host, f)
80 }
81 }
82
83 impl FromStr for Name {
84 type Err = InvalidNameError;
85
from_str(host: &str) -> Result<Self, Self::Err>86 fn from_str(host: &str) -> Result<Self, Self::Err> {
87 // Possibly add validation later
88 Ok(Name::new(host.into()))
89 }
90 }
91
92 /// Error indicating a given string was not a valid domain name.
93 #[derive(Debug)]
94 pub struct InvalidNameError(());
95
96 impl fmt::Display for InvalidNameError {
fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result97 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
98 f.write_str("Not a valid domain name")
99 }
100 }
101
102 impl Error for InvalidNameError {}
103
104 impl GaiResolver {
105 /// Construct a new `GaiResolver`.
new() -> Self106 pub fn new() -> Self {
107 GaiResolver { _priv: () }
108 }
109 }
110
111 impl Service<Name> for GaiResolver {
112 type Response = GaiAddrs;
113 type Error = io::Error;
114 type Future = GaiFuture;
115
poll_ready(&mut self, _cx: &mut Context<'_>) -> Poll<Result<(), io::Error>>116 fn poll_ready(&mut self, _cx: &mut Context<'_>) -> Poll<Result<(), io::Error>> {
117 Poll::Ready(Ok(()))
118 }
119
call(&mut self, name: Name) -> Self::Future120 fn call(&mut self, name: Name) -> Self::Future {
121 let blocking = tokio::task::spawn_blocking(move || {
122 debug!("resolving host={:?}", name.host);
123 (&*name.host, 0)
124 .to_socket_addrs()
125 .map(|i| SocketAddrs { iter: i })
126 });
127
128 GaiFuture { inner: blocking }
129 }
130 }
131
132 impl fmt::Debug for GaiResolver {
fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result133 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
134 f.pad("GaiResolver")
135 }
136 }
137
138 impl Future for GaiFuture {
139 type Output = Result<GaiAddrs, io::Error>;
140
poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output>141 fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
142 Pin::new(&mut self.inner).poll(cx).map(|res| match res {
143 Ok(Ok(addrs)) => Ok(GaiAddrs { inner: addrs }),
144 Ok(Err(err)) => Err(err),
145 Err(join_err) => {
146 if join_err.is_cancelled() {
147 Err(io::Error::new(io::ErrorKind::Interrupted, join_err))
148 } else {
149 panic!("gai background task failed: {:?}", join_err)
150 }
151 }
152 })
153 }
154 }
155
156 impl fmt::Debug for GaiFuture {
fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result157 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
158 f.pad("GaiFuture")
159 }
160 }
161
162 impl Drop for GaiFuture {
drop(&mut self)163 fn drop(&mut self) {
164 self.inner.abort();
165 }
166 }
167
168 impl Iterator for GaiAddrs {
169 type Item = SocketAddr;
170
next(&mut self) -> Option<Self::Item>171 fn next(&mut self) -> Option<Self::Item> {
172 self.inner.next()
173 }
174 }
175
176 impl fmt::Debug for GaiAddrs {
fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result177 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
178 f.pad("GaiAddrs")
179 }
180 }
181
182 pub(super) struct SocketAddrs {
183 iter: vec::IntoIter<SocketAddr>,
184 }
185
186 impl SocketAddrs {
new(addrs: Vec<SocketAddr>) -> Self187 pub(super) fn new(addrs: Vec<SocketAddr>) -> Self {
188 SocketAddrs {
189 iter: addrs.into_iter(),
190 }
191 }
192
try_parse(host: &str, port: u16) -> Option<SocketAddrs>193 pub(super) fn try_parse(host: &str, port: u16) -> Option<SocketAddrs> {
194 if let Ok(addr) = host.parse::<Ipv4Addr>() {
195 let addr = SocketAddrV4::new(addr, port);
196 return Some(SocketAddrs {
197 iter: vec![SocketAddr::V4(addr)].into_iter(),
198 });
199 }
200 if let Ok(addr) = host.parse::<Ipv6Addr>() {
201 let addr = SocketAddrV6::new(addr, port, 0, 0);
202 return Some(SocketAddrs {
203 iter: vec![SocketAddr::V6(addr)].into_iter(),
204 });
205 }
206 None
207 }
208
209 #[inline]
filter(self, predicate: impl FnMut(&SocketAddr) -> bool) -> SocketAddrs210 fn filter(self, predicate: impl FnMut(&SocketAddr) -> bool) -> SocketAddrs {
211 SocketAddrs::new(self.iter.filter(predicate).collect())
212 }
213
split_by_preference( self, local_addr_ipv4: Option<Ipv4Addr>, local_addr_ipv6: Option<Ipv6Addr>, ) -> (SocketAddrs, SocketAddrs)214 pub(super) fn split_by_preference(
215 self,
216 local_addr_ipv4: Option<Ipv4Addr>,
217 local_addr_ipv6: Option<Ipv6Addr>,
218 ) -> (SocketAddrs, SocketAddrs) {
219 match (local_addr_ipv4, local_addr_ipv6) {
220 (Some(_), None) => (self.filter(SocketAddr::is_ipv4), SocketAddrs::new(vec![])),
221 (None, Some(_)) => (self.filter(SocketAddr::is_ipv6), SocketAddrs::new(vec![])),
222 _ => {
223 let preferring_v6 = self
224 .iter
225 .as_slice()
226 .first()
227 .map(SocketAddr::is_ipv6)
228 .unwrap_or(false);
229
230 let (preferred, fallback) = self
231 .iter
232 .partition::<Vec<_>, _>(|addr| addr.is_ipv6() == preferring_v6);
233
234 (SocketAddrs::new(preferred), SocketAddrs::new(fallback))
235 }
236 }
237 }
238
is_empty(&self) -> bool239 pub(super) fn is_empty(&self) -> bool {
240 self.iter.as_slice().is_empty()
241 }
242
len(&self) -> usize243 pub(super) fn len(&self) -> usize {
244 self.iter.as_slice().len()
245 }
246 }
247
248 impl Iterator for SocketAddrs {
249 type Item = SocketAddr;
250 #[inline]
next(&mut self) -> Option<SocketAddr>251 fn next(&mut self) -> Option<SocketAddr> {
252 self.iter.next()
253 }
254 }
255
256 /*
257 /// A resolver using `getaddrinfo` calls via the `tokio_executor::threadpool::blocking` API.
258 ///
259 /// Unlike the `GaiResolver` this will not spawn dedicated threads, but only works when running on the
260 /// multi-threaded Tokio runtime.
261 #[cfg(feature = "runtime")]
262 #[derive(Clone, Debug)]
263 pub struct TokioThreadpoolGaiResolver(());
264
265 /// The future returned by `TokioThreadpoolGaiResolver`.
266 #[cfg(feature = "runtime")]
267 #[derive(Debug)]
268 pub struct TokioThreadpoolGaiFuture {
269 name: Name,
270 }
271
272 #[cfg(feature = "runtime")]
273 impl TokioThreadpoolGaiResolver {
274 /// Creates a new DNS resolver that will use tokio threadpool's blocking
275 /// feature.
276 ///
277 /// **Requires** its futures to be run on the threadpool runtime.
278 pub fn new() -> Self {
279 TokioThreadpoolGaiResolver(())
280 }
281 }
282
283 #[cfg(feature = "runtime")]
284 impl Service<Name> for TokioThreadpoolGaiResolver {
285 type Response = GaiAddrs;
286 type Error = io::Error;
287 type Future = TokioThreadpoolGaiFuture;
288
289 fn poll_ready(&mut self, _cx: &mut Context<'_>) -> Poll<Result<(), io::Error>> {
290 Poll::Ready(Ok(()))
291 }
292
293 fn call(&mut self, name: Name) -> Self::Future {
294 TokioThreadpoolGaiFuture { name }
295 }
296 }
297
298 #[cfg(feature = "runtime")]
299 impl Future for TokioThreadpoolGaiFuture {
300 type Output = Result<GaiAddrs, io::Error>;
301
302 fn poll(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Self::Output> {
303 match ready!(tokio_executor::threadpool::blocking(|| (
304 self.name.as_str(),
305 0
306 )
307 .to_socket_addrs()))
308 {
309 Ok(Ok(iter)) => Poll::Ready(Ok(GaiAddrs {
310 inner: IpAddrs { iter },
311 })),
312 Ok(Err(e)) => Poll::Ready(Err(e)),
313 // a BlockingError, meaning not on a tokio_executor::threadpool :(
314 Err(e) => Poll::Ready(Err(io::Error::new(io::ErrorKind::Other, e))),
315 }
316 }
317 }
318 */
319
320 mod sealed {
321 use std::future::Future;
322 use std::task::{Context, Poll};
323
324 use super::{Name, SocketAddr};
325 use tower_service::Service;
326
327 // "Trait alias" for `Service<Name, Response = Addrs>`
328 pub trait Resolve {
329 type Addrs: Iterator<Item = SocketAddr>;
330 type Error: Into<Box<dyn std::error::Error + Send + Sync>>;
331 type Future: Future<Output = Result<Self::Addrs, Self::Error>>;
332
poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>>333 fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>>;
resolve(&mut self, name: Name) -> Self::Future334 fn resolve(&mut self, name: Name) -> Self::Future;
335 }
336
337 impl<S> Resolve for S
338 where
339 S: Service<Name>,
340 S::Response: Iterator<Item = SocketAddr>,
341 S::Error: Into<Box<dyn std::error::Error + Send + Sync>>,
342 {
343 type Addrs = S::Response;
344 type Error = S::Error;
345 type Future = S::Future;
346
poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>>347 fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
348 Service::poll_ready(self, cx)
349 }
350
resolve(&mut self, name: Name) -> Self::Future351 fn resolve(&mut self, name: Name) -> Self::Future {
352 Service::call(self, name)
353 }
354 }
355 }
356
resolve<R>(resolver: &mut R, name: Name) -> Result<R::Addrs, R::Error> where R: Resolve,357 pub(super) async fn resolve<R>(resolver: &mut R, name: Name) -> Result<R::Addrs, R::Error>
358 where
359 R: Resolve,
360 {
361 futures_util::future::poll_fn(|cx| resolver.poll_ready(cx)).await?;
362 resolver.resolve(name).await
363 }
364
365 #[cfg(test)]
366 mod tests {
367 use super::*;
368 use std::net::{Ipv4Addr, Ipv6Addr};
369
370 #[test]
test_ip_addrs_split_by_preference()371 fn test_ip_addrs_split_by_preference() {
372 let ip_v4 = Ipv4Addr::new(127, 0, 0, 1);
373 let ip_v6 = Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1);
374 let v4_addr = (ip_v4, 80).into();
375 let v6_addr = (ip_v6, 80).into();
376
377 let (mut preferred, mut fallback) = SocketAddrs {
378 iter: vec![v4_addr, v6_addr].into_iter(),
379 }
380 .split_by_preference(None, None);
381 assert!(preferred.next().unwrap().is_ipv4());
382 assert!(fallback.next().unwrap().is_ipv6());
383
384 let (mut preferred, mut fallback) = SocketAddrs {
385 iter: vec![v6_addr, v4_addr].into_iter(),
386 }
387 .split_by_preference(None, None);
388 assert!(preferred.next().unwrap().is_ipv6());
389 assert!(fallback.next().unwrap().is_ipv4());
390
391 let (mut preferred, mut fallback) = SocketAddrs {
392 iter: vec![v4_addr, v6_addr].into_iter(),
393 }
394 .split_by_preference(Some(ip_v4), Some(ip_v6));
395 assert!(preferred.next().unwrap().is_ipv4());
396 assert!(fallback.next().unwrap().is_ipv6());
397
398 let (mut preferred, mut fallback) = SocketAddrs {
399 iter: vec![v6_addr, v4_addr].into_iter(),
400 }
401 .split_by_preference(Some(ip_v4), Some(ip_v6));
402 assert!(preferred.next().unwrap().is_ipv6());
403 assert!(fallback.next().unwrap().is_ipv4());
404
405 let (mut preferred, fallback) = SocketAddrs {
406 iter: vec![v4_addr, v6_addr].into_iter(),
407 }
408 .split_by_preference(Some(ip_v4), None);
409 assert!(preferred.next().unwrap().is_ipv4());
410 assert!(fallback.is_empty());
411
412 let (mut preferred, fallback) = SocketAddrs {
413 iter: vec![v4_addr, v6_addr].into_iter(),
414 }
415 .split_by_preference(None, Some(ip_v6));
416 assert!(preferred.next().unwrap().is_ipv6());
417 assert!(fallback.is_empty());
418 }
419
420 #[test]
test_name_from_str()421 fn test_name_from_str() {
422 const DOMAIN: &str = "test.example.com";
423 let name = Name::from_str(DOMAIN).expect("Should be a valid domain");
424 assert_eq!(name.as_str(), DOMAIN);
425 assert_eq!(name.to_string(), DOMAIN);
426 }
427 }
428