v1.17: Limit max concurrent connections (backport of #851) (#925)

* Limit max concurrent connections (#851)


Co-authored-by: Lijun Wang <[email protected]>

streamer/src/nonblocking/quic.rs

@@ -115,7 +115,9 @@ pub fn spawn_server(
     coalesce: Duration,
 ) -> Result<(Endpoint, Arc<StreamStats>, JoinHandle<()>), QuicServerError> {
     info!("Start {name} quic server on {sock:?}");
-    let (config, _cert) = configure_server(keypair, gossip_host)?;
+    let concurrent_connections = max_staked_connections + max_unstaked_connections;
+    let max_concurrent_connections = concurrent_connections + concurrent_connections / 4;
+    let (config, _cert) = configure_server(keypair, gossip_host, max_concurrent_connections)?;
 
     let endpoint = Endpoint::new(
         EndpointConfig::default(),

streamer/src/quic.rs

@@ -56,6 +56,7 @@ impl rustls::server::ClientCertVerifier for SkipClientVerification {
 pub(crate) fn configure_server(
     identity_keypair: &Keypair,
     gossip_host: IpAddr,
+    max_concurrent_connections: usize,
 ) -> Result<(ServerConfig, String), QuicServerError> {
     let (cert, priv_key) = new_self_signed_tls_certificate(identity_keypair, gossip_host)?;
     let cert_chain_pem_parts = vec![Pem {
@@ -71,6 +72,7 @@ pub(crate) fn configure_server(
     server_tls_config.alpn_protocols = vec![ALPN_TPU_PROTOCOL_ID.to_vec()];
 
     let mut server_config = ServerConfig::with_crypto(Arc::new(server_tls_config));
+    server_config.concurrent_connections(max_concurrent_connections as u32);
     server_config.use_retry(true);
     let config = Arc::get_mut(&mut server_config.transport).unwrap();