Clean up Config docs and add compression threshold (#148)

src/config.rs

@@ -85,9 +85,9 @@ pub trait Config: Sized + Send + Sync + 'static {
         STANDARD_TPS
     }
 
-    /// Called once at startup to get the connection mode option, which
-    /// determines if client authentication and encryption should take place
-    /// and if the server should get the player data from a proxy.
+    /// Called to get the connection mode option, which determines if client
+    /// authentication and encryption should take place and if the server
+    /// should get the player data from a proxy.
     ///
     /// # Default Implementation
     ///
@@ -96,13 +96,62 @@ pub trait Config: Sized + Send + Sync + 'static {
         ConnectionMode::Online
     }
 
-    /// Called once at startup to get the "prevent-proxy-connections" option,
-    /// which determines if client IP validation should take place.
-    ///
-    /// When prevent_proxy_connections is enabled, clients can no longer log-in
-    /// if they connected to the yggdrasil server using a different IP.
+    /// Obtains the compression threshold to use for compressing packets. For a
+    /// compression threshold of `Some(N)`, packets with encoded lengths >= `N`
+    /// are compressed while all others are not. `None` disables compression.
     ///
     /// # Default Implementation
+    ///
+    /// If the connection mode is [`ConnectionMode::Online`], `Some(256)` is
+    /// returned. Otherwise, compression is disabled.
+    fn compression_threshold(&self) -> Option<u32> {
+        match self.connection_mode() {
+            ConnectionMode::Online => Some(256),
+            _ => None,
+        }
+    }
+
+    /// Called upon every client login to obtain the full URL to use for session
+    /// server requests. This is done to authenticate player accounts. This
+    /// method is not called unless [online mode] is enabled.
+    ///
+    /// It is assumed that upon successful request, a structure matching the
+    /// description in the [wiki](https://wiki.vg/Protocol_Encryption#Server) was obtained.
+    /// Providing a URL that does not return such a structure will result in a
+    /// disconnect for every client that connects.
+    ///
+    /// The arguments are described in the linked wiki article.
+    ///
+    /// # Default Implementation
+    ///
+    /// Uses the official Minecraft session server. This is formatted as
+    /// `https://sessionserver.mojang.com/session/minecraft/hasJoined?username=<username>&serverId=<auth-digest>&ip=<player-ip>`.
+    ///
+    /// [online mode]: crate::config::ConnectionMode::Online
+    fn session_server(
+        &self,
+        server: &SharedServer<Self>,
+        username: Username<&str>,
+        auth_digest: &str,
+        player_ip: &IpAddr,
+    ) -> String {
+        if self.prevent_proxy_connections() {
+            format!("https://sessionserver.mojang.com/session/minecraft/hasJoined?username={username}&serverId={auth_digest}&ip={player_ip}")
+        } else {
+            format!("https://sessionserver.mojang.com/session/minecraft/hasJoined?username={username}&serverId={auth_digest}")
+        }
+    }
+
+    /// Called from the default implementation of [`Config::session_server`] to
+    /// get the "prevent-proxy-connections" option, which determines if client
+    /// IP validation should take place.
+    ///
+    /// When `prevent_proxy_connections` is enabled, clients can no longer
+    /// log-in if they connected to the yggdrasil server using a different
+    /// IP.
+    ///
+    /// # Default Implementation
+    ///
     /// Proxy connections are allowed.
     ///
     /// Returns `false`.
@@ -119,8 +168,8 @@ pub trait Config: Sized + Send + Sync + 'static {
     ///
     /// # Default Implementation
     ///
-    /// An unspecified value is returned that should be adequate in most
-    /// situations.
+    /// An unspecified value is returned that should be adequate for most
+    /// situations. This default may change in future versions.
     fn incoming_capacity(&self) -> usize {
         MAX_PACKET_SIZE as usize
     }
@@ -134,8 +183,8 @@ pub trait Config: Sized + Send + Sync + 'static {
     ///
     /// # Default Implementation
     ///
-    /// An unspecified value is returned that should be adequate in most
-    /// situations.
+    /// An unspecified value is returned that should be adequate for most
+    /// situations. This default may change in future versions.
     fn outgoing_capacity(&self) -> usize {
         MAX_PACKET_SIZE as usize * 4
     }
@@ -229,30 +278,6 @@ pub trait Config: Sized + Send + Sync + 'static {
         Ok(())
     }
 
-    /// Called upon (every) client connect (if online mode is enabled) to obtain
-    /// the full URL to use for session server requests. Defaults to
-    /// `https://sessionserver.mojang.com/session/minecraft/hasJoined?username=<username>&serverId=<auth-digest>&ip=<player-ip>`.
-    ///
-    /// It is assumed, that upon successful request, a structure matching the
-    /// description in the [wiki](https://wiki.vg/Protocol_Encryption#Server) was obtained.
-    /// Providing a URL that does not return such a structure will result in a
-    /// disconnect for every client that connects.
-    ///
-    /// The arguments are described in the linked wiki article.
-    fn format_session_server_url(
-        &self,
-        server: &SharedServer<Self>,
-        username: Username<&str>,
-        auth_digest: &str,
-        player_ip: &IpAddr,
-    ) -> String {
-        if self.prevent_proxy_connections() {
-            format!("https://sessionserver.mojang.com/session/minecraft/hasJoined?username={username}&serverId={auth_digest}&ip={player_ip}")
-        } else {
-            format!("https://sessionserver.mojang.com/session/minecraft/hasJoined?username={username}&serverId={auth_digest}")
-        }
-    }
-
     /// Called after the server is created, but prior to accepting connections
     /// and entering the update loop.
     ///
@@ -276,7 +301,7 @@ pub trait Config: Sized + Send + Sync + 'static {
     /// # Default Implementation
     ///
     /// The default implementation does nothing.
-    fn update(&self, server: &mut Server<Self>);
+    fn update(&self, server: &mut Server<Self>) {}
 }
 
 /// The result of the [`server_list_ping`](Config::server_list_ping) callback.
@@ -316,7 +341,7 @@ pub enum ConnectionMode {
     /// This mode should be used for all publicly exposed servers which are not
     /// behind a proxy.
     ///
-    /// [configured session server]: Config::format_session_server_url
+    /// [configured session server]: Config::session_server
     #[default]
     Online,
     /// Disables client authentication with the configured session server.
@@ -395,6 +420,4 @@ where
     type WorldState = W;
     type ChunkState = Ch;
     type PlayerListState = P;
-
-    fn update(&self, _server: &mut Server<Self>) {}
 }

src/protocol/codec.rs

@@ -53,7 +53,7 @@ impl PacketEncoder {
 
         if let Some(threshold) = self.compression_threshold {
             if data_len >= threshold as usize {
-                let mut z = ZlibEncoder::new(&mut self.compress_buf, Compression::best());
+                let mut z = ZlibEncoder::new(&mut self.compress_buf, Compression::new(4));
                 pkt.encode_packet(&mut z)?;
                 drop(z);
 

src/server.rs

@@ -615,13 +615,14 @@ async fn handle_login(
         ConnectionMode::Velocity { secret } => login::velocity(ctrl, username, secret).await?,
     };
 
-    let compression_threshold = 256;
+    if let Some(threshold) = server.0.cfg.compression_threshold() {
         ctrl.send_packet(&SetCompression {
-        threshold: VarInt(compression_threshold as i32),
+            threshold: VarInt(threshold as i32),
         })
         .await?;
 
-    ctrl.set_compression(Some(compression_threshold));
+        ctrl.set_compression(Some(threshold));
+    }
 
     if let Err(reason) = server.0.cfg.login(server, &ncd).await {
         log::info!("Disconnect at login: \"{reason}\"");

src/server/byte_channel.rs

@@ -123,7 +123,7 @@ impl ByteSender {
 pub enum TrySendError {
     #[error("sender disconnected")]
     Disconnected(BytesMut),
-    #[error("channel full")]
+    #[error("channel full (see `Config::outgoing_capacity`)")]
     Full(BytesMut),
 }
 

src/server/login.rs

@@ -96,7 +96,7 @@ pub(super) async fn online(
         .chain(&server.0.public_key_der)
         .finalize();
 
-    let url = server.config().format_session_server_url(
+    let url = server.config().session_server(
         server,
         username.as_str_username(),
         &auth_digest(&hash),