Add BBR initial_window config

tuic-server/README.md

@@ -103,6 +103,10 @@ replace <tag> with [current version tag](https://github.com/Itsusinn/tuic/pkgs/c
     // Default: 1500
     "max_external_packet_size": 1500,
 
+    // Optional. Sets the initial congestion window size in bytes for the BBR algorithm, which may improve burst performance but could lead to congestion under high concurrency.
+    // Default: None
+    "initial_window": 1048576,
+
     // Optional. Maximum number of bytes to transmit to a peer without acknowledgment
     // Should be set to at least the expected connection latency multiplied by the maximum desired throughput
     // Default: 8MiB * 2

tuic-server/src/config.rs

@@ -85,6 +85,9 @@ pub struct Config {
     #[serde(default = "default::max_external_packet_size")]
     pub max_external_packet_size: usize,
 
+    #[serde(default = "default::initial_window")]
+    pub initial_window: Option<u64>,
+
     #[serde(default = "default::send_window")]
     pub send_window: u64,
 
@@ -191,6 +194,10 @@ mod default {
         1500
     }
 
+    pub fn initial_window() -> Option<u64> {
+        None
+    }
+
     pub fn send_window() -> u64 {
         8 * 1024 * 1024 * 2
     }

tuic-server/src/server.rs

@@ -65,6 +65,16 @@ impl Server {
         ));
         let mut tp_cfg = TransportConfig::default();
 
+        fn create_bbr_with_initial_window(initial_window: Option<u64>) -> BbrConfig {
+            let mut bbr_config = BbrConfig::default();
+
+            if let Some(window) = initial_window {
+                bbr_config.initial_window(window);
+            }
+
+            bbr_config
+        }
+
         tp_cfg
             .max_concurrent_bidi_streams(VarInt::from(DEFAULT_CONCURRENT_STREAMS))
             .max_concurrent_uni_streams(VarInt::from(DEFAULT_CONCURRENT_STREAMS))
@@ -91,7 +101,8 @@ impl Server {
                 tp_cfg.congestion_controller_factory(Arc::new(NewRenoConfig::default()))
             }
             CongestionControl::Bbr => {
-                tp_cfg.congestion_controller_factory(Arc::new(BbrConfig::default()))
+                let bbr_config = create_bbr_with_initial_window(cfg.initial_window);
+                tp_cfg.congestion_controller_factory(Arc::new(bbr_config))
             }
         };