Use an Arc to share stub resolver

This somewhat simplifies usage for call sites. They no longer need to
use `&&StubResolver` for some APIs, and a future can be handed off
without being tied to the lifetime of the resolver.

The documentation already mentioned that the StubResolver was behind an
Arc so I did not need to updated it. StubResolver now implements clone,
which is cheap since it merely clones the Arc with the inner data.

This change is backwards-incompatible, and necessitates a bump in minor
for the next unstable release.

Fixes: #175

src/resolv/stub/mod.rs

@@ -73,8 +73,11 @@ pub mod conf;
 /// [`query`]: #method.query
 /// [`run`]: #method.run
 /// [`run_with_conf`]: #method.run_with_conf
+#[derive(Debug, Clone)]
+pub struct StubResolver(Arc<StubResolverInner>);
+
 #[derive(Debug)]
-pub struct StubResolver {
+struct StubResolverInner {
     transport: Mutex<Option<redundant::Connection<RequestMessage<Vec<u8>>>>>,
 
     /// Resolver options.
@@ -91,20 +94,19 @@ impl StubResolver {
 
     /// Creates a new resolver using the given configuraiton.
     pub fn from_conf(conf: ResolvConf) -> Self {
-        StubResolver {
+        StubResolver(Arc::new(StubResolverInner {
             transport: None.into(),
             options: conf.options,
-
             servers: conf.servers,
-        }
+        }))
     }
 
     pub fn options(&self) -> &ResolvOptions {
-        &self.options
+        &self.0.options
     }
 
     pub async fn query<N: ToName, Q: Into<Question<N>>>(
-        &self,
+        self,
         question: Q,
     ) -> Result<Answer, io::Error> {
         Query::new(self)?
@@ -113,7 +115,7 @@ impl StubResolver {
     }
 
     async fn query_message(
-        &self,
+        self,
         message: QueryMessage,
     ) -> Result<Answer, io::Error> {
         Query::new(self)?.run(message).await
@@ -147,10 +149,11 @@ impl StubResolver {
         // We have 3 modes of operation: use_vc: only use TCP, ign_tc: only
         // UDP no fallback to TCP, and normal with is UDP falling back to TCP.
 
-        for s in &self.servers {
+        for s in &self.0.servers {
             // This assumes that Transport only has UdpTcp and Tcp. Sadly, a
             // match doesn’t work here because of the use_cv flag.
-            if self.options.use_vc || matches!(s.transport, Transport::Tcp) {
+            if self.0.options.use_vc || matches!(s.transport, Transport::Tcp)
+            {
                 let (conn, tran) =
                     multi_stream::Connection::new(TcpConnect::new(s.addr));
                 // Start the run function on a separate task.
@@ -177,7 +180,7 @@ impl StubResolver {
     async fn get_transport(
         &self,
     ) -> Result<redundant::Connection<RequestMessage<Vec<u8>>>, Error> {
-        let mut opt_transport = self.transport.lock().await;
+        let mut opt_transport = self.0.transport.lock().await;
 
         match &*opt_transport {
             Some(transport) => Ok(transport.clone()),
@@ -215,22 +218,22 @@ impl StubResolver {
     pub async fn lookup_addr(
         &self,
         addr: IpAddr,
-    ) -> Result<FoundAddrs<&Self>, io::Error> {
-        lookup_addr(&self, addr).await
+    ) -> Result<FoundAddrs<Self>, io::Error> {
+        lookup_addr(self, addr).await
     }
 
     pub async fn lookup_host(
         &self,
         qname: impl ToName,
-    ) -> Result<FoundHosts<&Self>, io::Error> {
-        lookup_host(&self, qname).await
+    ) -> Result<FoundHosts<Self>, io::Error> {
+        lookup_host(self, qname).await
     }
 
     pub async fn search_host(
         &self,
         qname: impl ToRelativeName,
-    ) -> Result<FoundHosts<&Self>, io::Error> {
-        search_host(&self, qname).await
+    ) -> Result<FoundHosts<Self>, io::Error> {
+        search_host(self, qname).await
     }
 
     /// Performs an SRV lookup using this resolver.
@@ -242,7 +245,7 @@ impl StubResolver {
         name: impl ToName,
         fallback_port: u16,
     ) -> Result<Option<FoundSrvs>, SrvError> {
-        lookup_srv(&self, service, name, fallback_port).await
+        lookup_srv(self, service, name, fallback_port).await
     }
 }
 
@@ -294,39 +297,39 @@ impl Default for StubResolver {
     }
 }
 
-impl<'a> Resolver for &'a StubResolver {
+impl Resolver for StubResolver {
     type Octets = Bytes;
     type Answer = Answer;
     type Query =
-        Pin<Box<dyn Future<Output = Result<Answer, io::Error>> + Send + 'a>>;
+        Pin<Box<dyn Future<Output = Result<Answer, io::Error>> + Send>>;
 
     fn query<N, Q>(&self, question: Q) -> Self::Query
     where
         N: ToName,
         Q: Into<Question<N>>,
     {
         let message = Query::create_message(question.into());
-        Box::pin(self.query_message(message))
+        Box::pin(self.clone().query_message(message))
     }
 }
 
-impl<'a> SearchNames for &'a StubResolver {
+impl SearchNames for StubResolver {
     type Name = SearchSuffix;
-    type Iter = SearchIter<'a>;
+    type Iter = SearchIter;
 
     fn search_iter(&self) -> Self::Iter {
         SearchIter {
-            resolver: self,
+            resolver: self.clone(),
             pos: 0,
         }
     }
 }
 
 //------------ Query ---------------------------------------------------------
 
-pub struct Query<'a> {
+pub struct Query {
     /// The resolver whose configuration we are using.
-    resolver: &'a StubResolver,
+    resolver: StubResolver,
 
     edns: Arc<AtomicBool>,
 
@@ -340,8 +343,8 @@ pub struct Query<'a> {
     error: Result<Answer, io::Error>,
 }
 
-impl<'a> Query<'a> {
-    pub fn new(resolver: &'a StubResolver) -> Result<Self, io::Error> {
+impl Query {
+    pub fn new(resolver: StubResolver) -> Result<Self, io::Error> {
         Ok(Query {
             resolver,
             edns: Arc::new(AtomicBool::new(true)),
@@ -404,7 +407,7 @@ impl<'a> Query<'a> {
         })?;
         let mut gr_fut = transport.send_request(request_msg);
         let reply =
-            timeout(self.resolver.options.timeout, gr_fut.get_response())
+            timeout(self.resolver.0.options.timeout, gr_fut.get_response())
                 .await?
                 .map_err(|e| {
                     io::Error::new(io::ErrorKind::Other, e.to_string())
@@ -491,12 +494,12 @@ impl AsRef<Message<Bytes>> for Answer {
 //------------ SearchIter ----------------------------------------------------
 
 #[derive(Clone, Debug)]
-pub struct SearchIter<'a> {
-    resolver: &'a StubResolver,
+pub struct SearchIter {
+    resolver: StubResolver,
     pos: usize,
 }
 
-impl<'a> Iterator for SearchIter<'a> {
+impl Iterator for SearchIter {
     type Item = SearchSuffix;
 
     fn next(&mut self) -> Option<Self::Item> {