4 files changed, 41 insertions, 12 deletions

diff --git a/mullvad-daemon/src/relays.rs b/mullvad-daemon/src/relays.rs
index c3c2e7e365..ee53b7dde2 100644
--- a/mullvad-daemon/src/relays.rs
+++ b/mullvad-daemon/src/relays.rs
@@ -826,7 +826,7 @@ impl RelayListUpdater {
                 cmd = cmd_rx.next() => {
                     match cmd {
                         Some(_) => {
-                            self.consume_new_relay_list(self.rpc_client.relay_list().await).await;
+                            self.consume_new_relay_list(self.rpc_client.relay_list(None).await).await;
                         },
                         None => {
                             log::error!("Relay list updater shutting down");
@@ -841,14 +841,15 @@ impl RelayListUpdater {
 
     async fn consume_new_relay_list(
         &mut self,
-        result: Result<RelayList, mullvad_rpc::rest::Error>,
+        result: Result<Option<RelayList>, mullvad_rpc::rest::Error>,
     ) {
         match result {
-            Ok(relay_list) => {
+            Ok(Some(relay_list)) => {
                 if let Err(err) = self.update_cache(relay_list).await {
                     log::error!("Failed to update relay list cache: {}", err);
                 }
             }
+            Ok(None) => log::debug!("Relay list is up-to-date"),
             Err(err) => {
                 log::error!(
                     "Failed to fetch new relay list: {}. Will retry in {} minutes",
@@ -875,8 +876,8 @@ impl RelayListUpdater {
 
     fn download_relay_list(
         rpc_handle: RelayListProxy,
-    ) -> impl Future<Output = Result<RelayList, mullvad_rpc::rest::Error>> + 'static {
-        let download_futures = move || rpc_handle.relay_list();
+    ) -> impl Future<Output = Result<Option<RelayList>, mullvad_rpc::rest::Error>> + 'static {
+        let download_futures = move || rpc_handle.relay_list(None);
 
         let exponential_backoff = ExponentialBackoff::from_millis(EXPONENTIAL_BACKOFF_DELAY_MS)
             .factor(EXPONENTIAL_BACKOFF_FACTOR)
diff --git a/mullvad-rpc/src/bin/relay_list.rs b/mullvad-rpc/src/bin/relay_list.rs
index 8213d736da..e3ca00a9bc 100644
--- a/mullvad-rpc/src/bin/relay_list.rs
+++ b/mullvad-rpc/src/bin/relay_list.rs
@@ -10,7 +10,7 @@ async fn main() {
         MullvadRpcRuntime::new(tokio::runtime::Handle::current()).expect("Failed to load runtime");
 
     let relay_list_request = RelayListProxy::new(runtime.mullvad_rest_handle())
-        .relay_list()
+        .relay_list(None)
         .await;
 
     let relay_list = match relay_list_request {
diff --git a/mullvad-rpc/src/relay_list.rs b/mullvad-rpc/src/relay_list.rs
index b6784d3fda..cdf72c8c1f 100644
--- a/mullvad-rpc/src/relay_list.rs
+++ b/mullvad-rpc/src/relay_list.rs
@@ -1,7 +1,7 @@
 /// A module dedicated to retrieving the relay list from the master API.
 use crate::rest;
 
-use hyper::{Method, StatusCode};
+use hyper::{header, Method, StatusCode};
 use mullvad_types::{location, relay_list};
 use talpid_types::net::wireguard;
 
@@ -27,7 +27,10 @@ impl RelayListProxy {
     }
 
     /// Fetch the relay list
-    pub fn relay_list(&self) -> impl Future<Output = Result<relay_list::RelayList, rest::Error>> {
+    pub fn relay_list(
+        &self,
+        etag: Option<String>,
+    ) -> impl Future<Output = Result<Option<relay_list::RelayList>, rest::Error>> {
         let service = self.handle.service.clone();
         let request = self.handle.factory.request("/v1/relays", Method::GET);
 
@@ -35,13 +38,35 @@ impl RelayListProxy {
             let mut request = request?;
             request.set_timeout(RELAY_LIST_TIMEOUT);
 
+            let has_tag = etag.is_some();
+            if let Some(tag) = etag {
+                request.add_header("If-None-Match", tag)?;
+            }
+
             let response = service.request(request).await?;
+            if has_tag && response.status() == StatusCode::NOT_MODIFIED {
+                return Ok(None);
+            }
             if response.status() != StatusCode::OK {
                 return rest::handle_error_response(response).await;
             }
-            Ok(rest::deserialize_body::<ServerRelayList>(response)
-                .await?
-                .into_relay_list())
+
+            let etag = response
+                .headers()
+                .get(header::ETAG)
+                .and_then(|tag| match tag.to_str() {
+                    Ok(tag) => Some(tag.to_string()),
+                    Err(_) => {
+                        log::error!("Ignoring invalid tag from server: {:?}", tag.as_bytes());
+                        None
+                    }
+                });
+
+            Ok(Some(
+                rest::deserialize_body::<ServerRelayList>(response)
+                    .await?
+                    .into_relay_list(etag),
+            ))
         };
         future
     }
@@ -57,7 +82,7 @@ struct ServerRelayList {
 }
 
 impl ServerRelayList {
-    fn into_relay_list(self) -> relay_list::RelayList {
+    fn into_relay_list(self, etag: Option<String>) -> relay_list::RelayList {
         let mut countries = BTreeMap::new();
         let Self {
             locations,
@@ -90,6 +115,7 @@ impl ServerRelayList {
 
 
         relay_list::RelayList {
+            etag,
             countries: countries
                 .into_iter()
                 .map(|(_key, country)| country)
diff --git a/mullvad-types/src/relay_list.rs b/mullvad-types/src/relay_list.rs
index c3bbc33b6f..863e704792 100644
--- a/mullvad-types/src/relay_list.rs
+++ b/mullvad-types/src/relay_list.rs
@@ -21,12 +21,14 @@ use talpid_types::net::{
 #[cfg_attr(target_os = "android", derive(IntoJava))]
 #[cfg_attr(target_os = "android", jnix(package = "net.mullvad.mullvadvpn.model"))]
 pub struct RelayList {
+    pub etag: Option<String>,
     pub countries: Vec<RelayListCountry>,
 }
 
 impl RelayList {
     pub fn empty() -> Self {
         Self {
+            etag: None,
             countries: Vec::new(),
         }
     }