1//! DNS Resolution used by the `HttpConnector`.
2//!
3//! This module contains:
4//!
5//! - A [`GaiResolver`] that is the default resolver for the `HttpConnector`.
6//! - The `Name` type used as an argument to custom resolvers.
7//!
8//! # Resolvers are `Service`s
9//!
10//! A resolver is just a
11//! `Service<Name, Response = impl Iterator<Item = SocketAddr>>`.
12//!
13//! A simple resolver that ignores the name and always returns a specific
14//! address:
15//!
16//! ```rust,ignore
17//! use std::{convert::Infallible, iter, net::SocketAddr};
18//!
19//! let resolver = tower::service_fn(|_name| async {
20//! Ok::<_, Infallible>(iter::once(SocketAddr::from(([127, 0, 0, 1], 8080))))
21//! });
22//! ```
23use std::error::Error;
24use std::future::Future;
25use std::net::{Ipv4Addr, Ipv6Addr, SocketAddr, SocketAddrV4, SocketAddrV6, ToSocketAddrs};
26use std::pin::Pin;
27use std::str::FromStr;
28use std::task::{self, Poll};
29use std::{fmt, io, vec};
30
31use tokio::task::JoinHandle;
32use tower_service::Service;
33use tracing::debug_span;
34
35pub(super) use self::sealed::Resolve;
36
37/// A domain name to resolve into IP addresses.
38#[derive(Clone, Hash, Eq, PartialEq)]
39pub struct Name {
40 host: Box<str>,
41}
42
43/// A resolver using blocking `getaddrinfo` calls in a threadpool.
44#[derive(Clone)]
45pub struct GaiResolver {
46 _priv: (),
47}
48
49/// An iterator of IP addresses returned from `getaddrinfo`.
50pub struct GaiAddrs {
51 inner: SocketAddrs,
52}
53
54/// A future to resolve a name returned by `GaiResolver`.
55pub struct GaiFuture {
56 inner: JoinHandle<Result<SocketAddrs, io::Error>>,
57}
58
59impl Name {
60 pub(super) fn new(host: Box<str>) -> Name {
61 Name { host }
62 }
63
64 /// View the hostname as a string slice.
65 pub fn as_str(&self) -> &str {
66 &self.host
67 }
68}
69
70impl fmt::Debug for Name {
71 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
72 fmt::Debug::fmt(&self.host, f)
73 }
74}
75
76impl fmt::Display for Name {
77 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
78 fmt::Display::fmt(&self.host, f)
79 }
80}
81
82impl FromStr for Name {
83 type Err = InvalidNameError;
84
85 fn from_str(host: &str) -> Result<Self, Self::Err> {
86 // Possibly add validation later
87 Ok(Name::new(host.into()))
88 }
89}
90
91/// Error indicating a given string was not a valid domain name.
92#[derive(Debug)]
93pub struct InvalidNameError(());
94
95impl fmt::Display for InvalidNameError {
96 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
97 f.write_str(data:"Not a valid domain name")
98 }
99}
100
101impl Error for InvalidNameError {}
102
103impl GaiResolver {
104 /// Construct a new `GaiResolver`.
105 pub fn new() -> Self {
106 GaiResolver { _priv: () }
107 }
108}
109
110impl Service<Name> for GaiResolver {
111 type Response = GaiAddrs;
112 type Error = io::Error;
113 type Future = GaiFuture;
114
115 fn poll_ready(&mut self, _cx: &mut task::Context<'_>) -> Poll<Result<(), io::Error>> {
116 Poll::Ready(Ok(()))
117 }
118
119 fn call(&mut self, name: Name) -> Self::Future {
120 let span: Span = debug_span!("resolve", host = %name.host);
121 let blocking: JoinHandle> = tokio::task::spawn_blocking(move || {
122 let _enter: Entered<'_> = span.enter();
123 (&*name.host, 0)
124 .to_socket_addrs()
125 .map(|i: IntoIter| SocketAddrs { iter: i })
126 });
127
128 GaiFuture { inner: blocking }
129 }
130}
131
132impl fmt::Debug for GaiResolver {
133 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
134 f.pad("GaiResolver")
135 }
136}
137
138impl Future for GaiFuture {
139 type Output = Result<GaiAddrs, io::Error>;
140
141 fn poll(mut self: Pin<&mut Self>, cx: &mut task::Context<'_>) -> Poll<Self::Output> {
142 Pin::new(&mut self.inner).poll(cx).map(|res: Result, …>| match res {
143 Ok(Ok(addrs: SocketAddrs)) => Ok(GaiAddrs { inner: addrs }),
144 Ok(Err(err: Error)) => Err(err),
145 Err(join_err: JoinError) => {
146 if join_err.is_cancelled() {
147 Err(io::Error::new(kind:io::ErrorKind::Interrupted, error:join_err))
148 } else {
149 panic!("gai background task failed: {:?}", join_err)
150 }
151 }
152 })
153 }
154}
155
156impl fmt::Debug for GaiFuture {
157 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
158 f.pad("GaiFuture")
159 }
160}
161
162impl Drop for GaiFuture {
163 fn drop(&mut self) {
164 self.inner.abort();
165 }
166}
167
168impl Iterator for GaiAddrs {
169 type Item = SocketAddr;
170
171 fn next(&mut self) -> Option<Self::Item> {
172 self.inner.next()
173 }
174}
175
176impl fmt::Debug for GaiAddrs {
177 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
178 f.pad("GaiAddrs")
179 }
180}
181
182pub(super) struct SocketAddrs {
183 iter: vec::IntoIter<SocketAddr>,
184}
185
186impl SocketAddrs {
187 pub(super) fn new(addrs: Vec<SocketAddr>) -> Self {
188 SocketAddrs {
189 iter: addrs.into_iter(),
190 }
191 }
192
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]
210 fn filter(self, predicate: impl FnMut(&SocketAddr) -> bool) -> SocketAddrs {
211 SocketAddrs::new(self.iter.filter(predicate).collect())
212 }
213
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
239 pub(super) fn is_empty(&self) -> bool {
240 self.iter.as_slice().is_empty()
241 }
242
243 pub(super) fn len(&self) -> usize {
244 self.iter.as_slice().len()
245 }
246}
247
248impl Iterator for SocketAddrs {
249 type Item = SocketAddr;
250 #[inline]
251 fn next(&mut self) -> Option<SocketAddr> {
252 self.iter.next()
253 }
254}
255
256mod sealed {
257 use std::future::Future;
258 use std::task::{self, Poll};
259
260 use super::{Name, SocketAddr};
261 use tower_service::Service;
262
263 // "Trait alias" for `Service<Name, Response = Addrs>`
264 pub trait Resolve {
265 type Addrs: Iterator<Item = SocketAddr>;
266 type Error: Into<Box<dyn std::error::Error + Send + Sync>>;
267 type Future: Future<Output = Result<Self::Addrs, Self::Error>>;
268
269 fn poll_ready(&mut self, cx: &mut task::Context<'_>) -> Poll<Result<(), Self::Error>>;
270 fn resolve(&mut self, name: Name) -> Self::Future;
271 }
272
273 impl<S> Resolve for S
274 where
275 S: Service<Name>,
276 S::Response: Iterator<Item = SocketAddr>,
277 S::Error: Into<Box<dyn std::error::Error + Send + Sync>>,
278 {
279 type Addrs = S::Response;
280 type Error = S::Error;
281 type Future = S::Future;
282
283 fn poll_ready(&mut self, cx: &mut task::Context<'_>) -> Poll<Result<(), Self::Error>> {
284 Service::poll_ready(self, cx)
285 }
286
287 fn resolve(&mut self, name: Name) -> Self::Future {
288 Service::call(self, name)
289 }
290 }
291}
292
293pub(super) async fn resolve<R>(resolver: &mut R, name: Name) -> Result<R::Addrs, R::Error>
294where
295 R: Resolve,
296{
297 futures_util::future::poll_fn(|cx: &mut Context<'_>| resolver.poll_ready(cx)).await?;
298 resolver.resolve(name).await
299}
300
301#[cfg(test)]
302mod tests {
303 use super::*;
304 use std::net::{Ipv4Addr, Ipv6Addr};
305
306 #[test]
307 fn test_ip_addrs_split_by_preference() {
308 let ip_v4 = Ipv4Addr::new(127, 0, 0, 1);
309 let ip_v6 = Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1);
310 let v4_addr = (ip_v4, 80).into();
311 let v6_addr = (ip_v6, 80).into();
312
313 let (mut preferred, mut fallback) = SocketAddrs {
314 iter: vec![v4_addr, v6_addr].into_iter(),
315 }
316 .split_by_preference(None, None);
317 assert!(preferred.next().unwrap().is_ipv4());
318 assert!(fallback.next().unwrap().is_ipv6());
319
320 let (mut preferred, mut fallback) = SocketAddrs {
321 iter: vec![v6_addr, v4_addr].into_iter(),
322 }
323 .split_by_preference(None, None);
324 assert!(preferred.next().unwrap().is_ipv6());
325 assert!(fallback.next().unwrap().is_ipv4());
326
327 let (mut preferred, mut fallback) = SocketAddrs {
328 iter: vec![v4_addr, v6_addr].into_iter(),
329 }
330 .split_by_preference(Some(ip_v4), Some(ip_v6));
331 assert!(preferred.next().unwrap().is_ipv4());
332 assert!(fallback.next().unwrap().is_ipv6());
333
334 let (mut preferred, mut fallback) = SocketAddrs {
335 iter: vec![v6_addr, v4_addr].into_iter(),
336 }
337 .split_by_preference(Some(ip_v4), Some(ip_v6));
338 assert!(preferred.next().unwrap().is_ipv6());
339 assert!(fallback.next().unwrap().is_ipv4());
340
341 let (mut preferred, fallback) = SocketAddrs {
342 iter: vec![v4_addr, v6_addr].into_iter(),
343 }
344 .split_by_preference(Some(ip_v4), None);
345 assert!(preferred.next().unwrap().is_ipv4());
346 assert!(fallback.is_empty());
347
348 let (mut preferred, fallback) = SocketAddrs {
349 iter: vec![v4_addr, v6_addr].into_iter(),
350 }
351 .split_by_preference(None, Some(ip_v6));
352 assert!(preferred.next().unwrap().is_ipv6());
353 assert!(fallback.is_empty());
354 }
355
356 #[test]
357 fn test_name_from_str() {
358 const DOMAIN: &str = "test.example.com";
359 let name = Name::from_str(DOMAIN).expect("Should be a valid domain");
360 assert_eq!(name.as_str(), DOMAIN);
361 assert_eq!(name.to_string(), DOMAIN);
362 }
363}
364