Implement timeout for DNS resolution

1 files changed, 32 insertions, 4 deletions

diff --git a/mullvad-rpc/src/cached_dns_resolver.rs b/mullvad-rpc/src/cached_dns_resolver.rs
index 3acfad378c..f667214499 100644
--- a/mullvad-rpc/src/cached_dns_resolver.rs
+++ b/mullvad-rpc/src/cached_dns_resolver.rs
@@ -2,21 +2,35 @@ use std::fs::File;
 use std::io::{self, Read, Write};
 use std::net::{IpAddr, ToSocketAddrs};
 use std::path::{Path, PathBuf};
+use std::sync::mpsc;
+use std::thread;
 use std::time::{Duration, SystemTime, UNIX_EPOCH};
 
 
+static DNS_TIMEOUT: Duration = Duration::from_secs(2);
 static MAX_CACHE_AGE: Duration = Duration::from_secs(3600);
 static EXPIRED_CACHE_TIMESTAMP: SystemTime = UNIX_EPOCH;
 
 
 pub trait DnsResolver {
-    fn resolve(&self, host: &str) -> io::Result<IpAddr>;
+    fn resolve(&mut self, host: &str) -> io::Result<IpAddr>;
 }
 
 pub struct SystemDnsResolver;
 
-impl DnsResolver for SystemDnsResolver {
-    fn resolve(&self, host: &str) -> io::Result<IpAddr> {
+impl SystemDnsResolver {
+    fn resolve_in_background_thread(host: &str) -> mpsc::Receiver<io::Result<IpAddr>> {
+        let host = host.to_owned();
+        let (tx, rx) = mpsc::channel();
+
+        thread::spawn(move || {
+            let _ = tx.send(Self::resolve_hostname(&host));
+        });
+
+        rx
+    }
+
+    fn resolve_hostname(host: &str) -> io::Result<IpAddr> {
         (host, 0)
             .to_socket_addrs()?
             .next()
@@ -27,6 +41,20 @@ impl DnsResolver for SystemDnsResolver {
     }
 }
 
+impl DnsResolver for SystemDnsResolver {
+    fn resolve(&mut self, host: &str) -> io::Result<IpAddr> {
+        Self::resolve_in_background_thread(host)
+            .recv_timeout(DNS_TIMEOUT)
+            .map_err(|_| {
+                io::Error::new(
+                    io::ErrorKind::Other,
+                    "Timeout while performing DNS resolution",
+                )
+            })
+            .and_then(|result| result)
+    }
+}
+
 pub struct CachedDnsResolver<R: DnsResolver = SystemDnsResolver> {
     hostname: String,
     dns_resolver: R,
@@ -317,7 +345,7 @@ mod tests {
     }
 
     impl DnsResolver for MockDnsResolver {
-        fn resolve(&self, host: &str) -> io::Result<IpAddr> {
+        fn resolve(&mut self, host: &str) -> io::Result<IpAddr> {
             self.called.store(true, Ordering::Release);
 
             self.address.ok_or_else(|| {