Tweak surb management to be more conservative (#5570)

To reduce the risk of the IPR DoS the client:

- Lower the timeout until the IPR will disconnect a client
- Reduce fewer surbs at a time. Large surb requests increases the
  latency until all fragments in the response have been delivered. The
  efficiency gains of having large surb requests dimishes quickly for
  large sizes as well

common/client-core/config-types/src/lib.rs

@@ -50,7 +50,7 @@ const DEFAULT_MINIMUM_REPLY_SURB_THRESHOLD_BUFFER: usize = 0;
 // define how much to request at once
 // clients/client-core/src/client/replies/reply_controller.rs
 const DEFAULT_MINIMUM_REPLY_SURB_REQUEST_SIZE: u32 = 10;
-const DEFAULT_MAXIMUM_REPLY_SURB_REQUEST_SIZE: u32 = 100;
+const DEFAULT_MAXIMUM_REPLY_SURB_REQUEST_SIZE: u32 = 30;
 
 const DEFAULT_MAXIMUM_ALLOWED_SURB_REQUEST_SIZE: u32 = 500;
 

common/client-core/src/client/real_messages_control/message_handler.rs

@@ -33,10 +33,12 @@ pub enum PreparationError {
     #[error(transparent)]
     NymTopologyError(#[from] NymTopologyError),
 
-    #[error("The received message cannot be sent using a single reply surb. It ended up getting split into {fragments} fragments.")]
+    #[error("message too long for a single SURB, splitting into {fragments} fragments.")]
     MessageTooLongForSingleSurb { fragments: usize },
 
-    #[error("Not enough reply SURBs to send the message. We have {available} available and require at least {required}.")]
+    #[error(
+        "not enough reply SURBs to send the message, available: {available} required: {required}."
+    )]
     NotEnoughSurbs { available: usize, required: usize },
 }
 

common/client-core/src/client/replies/reply_controller/mod.rs

@@ -746,7 +746,7 @@ where
             .request_additional_reply_surbs(target, request_size)
             .await
         {
-            warn!("failed to request additional surbs... - {err}")
+            info!("{err}")
         }
     }
 

service-providers/ip-packet-router/src/constants.rs

@@ -7,8 +7,8 @@ use std::time::Duration;
 pub(crate) const DISCONNECT_TIMER_INTERVAL: Duration = Duration::from_secs(10);
 
 // We consider a client inactive if it hasn't sent any mixnet packets in this duration
-pub(crate) const CLIENT_MIXNET_INACTIVITY_TIMEOUT: Duration = Duration::from_secs(5 * 60);
+pub(crate) const CLIENT_MIXNET_INACTIVITY_TIMEOUT: Duration = Duration::from_secs(60);
 
 // We consider a client handler inactive if it hasn't received any packets from the tun device in
 // this duration
-pub(crate) const CLIENT_HANDLER_ACTIVITY_TIMEOUT: Duration = Duration::from_secs(10 * 60);
+pub(crate) const CLIENT_HANDLER_ACTIVITY_TIMEOUT: Duration = Duration::from_secs(5 * 60);