Use PF_ROUTE socket to track missing loopback alias instead of polling

1 files changed, 34 insertions, 52 deletions

diff --git a/talpid-core/src/resolver.rs b/talpid-core/src/resolver.rs
index 5107759297..8dcea70679 100644
--- a/talpid-core/src/resolver.rs
+++ b/talpid-core/src/resolver.rs
@@ -456,35 +456,8 @@ impl LocalResolver {
 
             log::debug!("Created loopback address {addr}");
 
-            let detect_removed_alias_task = tokio::spawn(async move {
-                // Periodically check that the alias still exists, and recreate it if it doesn't
-                // This fixes the issue that macOS sometimes removes the alias
-                // TODO: This could be done by listening to events on a PF_ROUTE socket
-                loop {
-                    tokio::time::sleep(Duration::from_secs(10)).await;
-
-                    let found_loopback_addr = match is_valid_address(LOOPBACK, addr.into()) {
-                        Ok(found_loopback_addr) => found_loopback_addr,
-                        Err(err) => {
-                            log::warn!("Failed to check if loopback address {addr} exists: {err}");
-                            continue;
-                        }
-                    };
-
-                    if !found_loopback_addr {
-                        log::debug!("Missing loopback address alias {addr}. Recreating");
-
-                        talpid_macos::net::add_alias(LOOPBACK, IpAddr::from(addr))
-                            .await
-                            .inspect_err(|e| {
-                                log::warn!("Failed to add loopback {LOOPBACK} alias {addr}: {e}");
-                            })
-                            .ok();
-                    } else {
-                        log::trace!("Loopback address {addr} exists");
-                    }
-                }
-            });
+            let detect_removed_alias_task =
+                tokio::spawn(detect_loopback_address_removal(IpAddr::from(addr)));
 
             // Clean up ip address when stopping the resolver
             let cleanup_ifconfig = on_drop(move || {
@@ -648,37 +621,46 @@ fn kill_mdnsresponder() -> io::Result<()> {
     Ok(())
 }
 
-/// Return whether the IP address is assigned for the given `interface`
-fn is_valid_address(interface: &'static str, addr_to_find: IpAddr) -> nix::Result<bool> {
-    let mut found_addr = false;
-
-    let interface_addrs = nix::ifaddrs::getifaddrs()?;
+/// Detect when the loopback address is removed on the loopback interface, and add it back whenever
+/// that occurs.
+async fn detect_loopback_address_removal(addr: IpAddr) -> Result<(), talpid_routing::RouteError> {
+    let mut routing_table = talpid_routing::RoutingTable::new().map_err(|e| {
+        log::warn!("Failed to create routing table interface: {e}");
+        e
+    })?;
 
-    for interface_addr in interface_addrs {
-        let Some(address) = interface_addr.address else {
+    // Listen for the loopback address being removed, and add it back if that happens
+    loop {
+        let Ok(msg) = routing_table.next_message().await else {
+            log::trace!("Failed to read next message from routing table");
             continue;
         };
-        if interface_addr.interface_name != interface {
-            continue;
-        }
-        let ip: Option<IpAddr> = address
-            .as_sockaddr_in()
-            .map(|addr| IpAddr::from(addr.ip()))
-            .or_else(|| {
-                address
-                    .as_sockaddr_in6()
-                    .map(|addr| IpAddr::from(addr.ip()))
-            });
-        let Some(ip) = ip else {
+
+        let RouteSocketMessage::DeleteAddress(msg) = msg else {
             continue;
         };
 
-        if ip == addr_to_find {
-            found_addr = true;
-            break;
+        // The deleted address either matches the one we care about, or we do not know
+        let matches_addr = msg
+            .address()
+            .map(|deleted_addr| deleted_addr == addr)
+            .unwrap_or(true);
+        if !matches_addr {
+            continue;
         }
+
+        // Sleep for a bit so we do not spin if something weird is going on
+        tokio::time::sleep(Duration::from_secs(1)).await;
+
+        log::debug!("Detected possible removal of loopback address {addr}. Adding it back");
+
+        talpid_macos::net::add_alias(LOOPBACK, addr)
+            .await
+            .inspect_err(|e| {
+                log::warn!("Failed to add loopback {LOOPBACK} alias {addr}: {e}");
+            })
+            .ok();
     }
-    Ok(found_addr)
 }
 
 type LookupResponse<'a> = MessageResponse<