Adative max gso buffer size based on the loss

max_burst indicates the maximum size of gso buffer.
It will be reduced by 25% when the outgoing packet loss
rate is increasing, to prevent the further loss caused
by outgoing packet burstness.

apps/src/bin/quiche-server.rs

@@ -374,6 +374,8 @@ fn main() {
                     siduck_conn: None,
                     app_proto_selected: false,
                     max_datagram_size,
+                    loss_rate: 0.0,
+                    max_send_burst: MAX_BUF_SIZE,
                 };
 
                 clients.insert(client_id, client);
@@ -526,9 +528,21 @@ fn main() {
         // packets to be sent.
         continue_write = false;
         for client in clients.values_mut() {
-            let max_send_burst = client.conn.send_quantum().min(MAX_BUF_SIZE) /
-                client.max_datagram_size *
-                client.max_datagram_size;
+            // Reduce max_send_burst by 25% if loss is increasing more than 0.1%.
+            let loss_rate =
+                client.conn.stats().lost as f64 / client.conn.stats().sent as f64;
+            if loss_rate > client.loss_rate + 0.001 {
+                client.max_send_burst = client.max_send_burst / 4 * 3;
+                // Minimun bound of 10xMSS.
+                client.max_send_burst =
+                    client.max_send_burst.max(client.max_datagram_size * 10);
+                client.loss_rate = loss_rate;
+            }
+
+            let max_send_burst =
+                client.conn.send_quantum().min(client.max_send_burst) /
+                    client.max_datagram_size *
+                    client.max_datagram_size;
             let mut total_write = 0;
             let mut dst_info = None;
 

apps/src/common.rs

@@ -97,6 +97,10 @@ pub struct Client {
     pub partial_responses: std::collections::HashMap<u64, PartialResponse>,
 
     pub max_datagram_size: usize,
+
+    pub loss_rate: f64,
+
+    pub max_send_burst: usize,
 }
 
 pub type ClientIdMap = HashMap<ConnectionId<'static>, ClientId>;