ba7b2a754e
Co-authored-by: Danny Browning <danny.browning@protectwise.com> Co-authored-by: Daniel Eades <danieleades@hotmail.com>
76 lines
2.6 KiB
Rust
76 lines
2.6 KiB
Rust
use std::net::IpAddr;
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use std::sync::{Arc, Mutex, Once};
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use std::{io, vec};
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use futures::{future, Future};
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use hyper::client::connect::dns as hyper_dns;
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use tokio;
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use trust_dns_resolver::{system_conf, AsyncResolver, BackgroundLookupIp};
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// If instead the type were just `AsyncResolver`, it breaks the default recursion limit
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// for the compiler to determine if `reqwest::Client` is `Send`. This is because `AsyncResolver`
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// has **a lot** of internal generic types that pushes us over the limit.
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//
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// "Erasing" the internal resolver type saves us from this limit.
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type ErasedResolver = Box<dyn Fn(hyper_dns::Name) -> BackgroundLookupIp + Send + Sync>;
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type Background = Box<dyn Future<Item = (), Error = ()> + Send>;
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#[derive(Clone)]
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pub(crate) struct TrustDnsResolver {
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inner: Arc<Inner>,
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}
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struct Inner {
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background: Mutex<Option<Background>>,
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once: Once,
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resolver: ErasedResolver,
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}
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impl TrustDnsResolver {
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pub(crate) fn new() -> io::Result<Self> {
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let (conf, opts) = system_conf::read_system_conf()?;
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let (resolver, bg) = AsyncResolver::new(conf, opts);
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let resolver: ErasedResolver = Box::new(move |name| resolver.lookup_ip(name.as_str()));
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let background = Mutex::new(Some(Box::new(bg) as Background));
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let once = Once::new();
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Ok(TrustDnsResolver {
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inner: Arc::new(Inner {
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background,
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once,
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resolver,
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}),
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})
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}
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}
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impl hyper_dns::Resolve for TrustDnsResolver {
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type Addrs = vec::IntoIter<IpAddr>;
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type Future = Box<dyn Future<Output = Result<Self::Addrs, io::Error>> + Send>;
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fn resolve(&self, name: hyper_dns::Name) -> Self::Future {
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let inner = self.inner.clone();
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Box::new(future::lazy(move || {
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inner.once.call_once(|| {
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// The `bg` (background) future needs to be spawned onto an executor,
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// but a `reqwest::Client` may be constructed before an executor is ready.
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// So, the `bg` future cannot be spawned *until* the executor starts to
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// `poll` this future.
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let bg = inner
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.background
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.lock()
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.expect("resolver background lock")
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.take()
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.expect("background only taken once");
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tokio::spawn(bg);
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});
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(inner.resolver)(name)
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.map(|lookup| lookup.iter().collect::<Vec<_>>().into_iter())
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.map_err(|err| io::Error::new(io::ErrorKind::Other, err.to_string()))
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}))
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}
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}
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