adjust AEAD-2022 client & server remembered session count

Author: zonyitoo

crates/shadowsocks-service/src/local/net/mod.rs

@@ -6,4 +6,4 @@ pub use self::{
 };
 
 mod tcp;
-mod udp;
+pub(crate) mod udp;

crates/shadowsocks-service/src/local/net/udp/association.rs

@@ -187,10 +187,26 @@ struct ServerSessionContext {
     server_session_map: LruCache<u64, ServerContext>,
 }
 
+// Server shouldn't be remembered too long.
+//
+// Server session will only changed if
+// 1. Association expired
+// 2. Server restarted
+//
+// Normally there should only be 1 unqiue server session.
+pub const SERVER_SESSION_REMEMBER_DURATION: Duration = Duration::from_secs(60);
+
+// Remember 2 server sessions. When server restarts,
+// some of the packet on wire may be received later then those new ones.
+pub const SERVER_SESSION_REMEMBER_COUNT: usize = 2;
+
 impl ServerSessionContext {
     fn new() -> ServerSessionContext {
         ServerSessionContext {
-            server_session_map: LruCache::with_expiry_duration_and_capacity(Duration::from_secs(30 * 60), 5),
+            server_session_map: LruCache::with_expiry_duration_and_capacity(
+                SERVER_SESSION_REMEMBER_DURATION,
+                SERVER_SESSION_REMEMBER_COUNT,
+            ),
         }
     }
 }

crates/shadowsocks-service/src/local/tunnel/udprelay.rs

@@ -25,7 +25,11 @@ use shadowsocks::{
 use tokio::{net::UdpSocket, sync::mpsc, task::JoinHandle, time};
 
 use crate::{
-    local::{context::ServiceContext, loadbalancing::PingBalancer},
+    local::{
+        context::ServiceContext,
+        loadbalancing::PingBalancer,
+        net::udp::association::{SERVER_SESSION_REMEMBER_COUNT, SERVER_SESSION_REMEMBER_DURATION},
+    },
     net::{
         packet_window::PacketWindowFilter,
         MonProxySocket,
@@ -217,7 +221,10 @@ struct ServerSessionContext {
 impl ServerSessionContext {
     fn new() -> ServerSessionContext {
         ServerSessionContext {
-            server_session_map: LruCache::with_expiry_duration_and_capacity(Duration::from_secs(30 * 60), 5),
+            server_session_map: LruCache::with_expiry_duration_and_capacity(
+                SERVER_SESSION_REMEMBER_DURATION,
+                SERVER_SESSION_REMEMBER_COUNT,
+            ),
         }
     }
 }

crates/shadowsocks-service/src/server/udprelay.rs

@@ -324,9 +324,20 @@ struct ClientSessionContext {
 
 impl ClientSessionContext {
     fn new(client_session_id: u64) -> ClientSessionContext {
+        // Client shouldn't be remembered too long.
+        // If a client was switching between networks (like Wi-Fi and Cellular),
+        // when it switched back from another, the packet filter window will be too old.
+        const CLIENT_SESSION_REMEMBER_DURATION: Duration = Duration::from_secs(60);
+
+        // Wi-Fi & Cellular network device, so it is 2 for most users
+        const CLIENT_SESSION_REMEMBER_COUNT: usize = 2;
+
         ClientSessionContext {
             client_session_id,
-            client_context_map: LruCache::with_expiry_duration_and_capacity(Duration::from_secs(30 * 60), 10),
+            client_context_map: LruCache::with_expiry_duration_and_capacity(
+                CLIENT_SESSION_REMEMBER_DURATION,
+                CLIENT_SESSION_REMEMBER_COUNT,
+            ),
         }
     }
 }