Tag 0.1.7

Critical bug fixes

Signed-off-by: Jacob Kiers <code@kiers.eu>

.cargo/config.toml

@@ -0,0 +1,3 @@
+[profile.release]
+lto = "thin"
+strip = true

.drone.jsonnet

@@ -0,0 +1,92 @@
+local executableName = 'fourth';
+local build_image = 'img.kie.rs/jjkiers/rust-cross:rust1.71.1-zig';
+
+local archs = [
+  { target: 'aarch64-unknown-linux-musl', short: 'arm64-musl' },
+  { target: 'x86_64-pc-windows-gnu', short: 'windows' },
+  { target: 'x86_64-unknown-linux-musl', short: 'amd64-musl' },
+];
+
+local getStepName(arch) = 'Build for ' + arch.short;
+
+local builtExecutableName(arch) = executableName + if std.length(std.findSubstr(arch.short, 'windows')) > 0 then '.exe' else '';
+local targetExecutableName(arch) = executableName + '-' + arch.target + if std.length(std.findSubstr(arch.short, 'windows')) > 0 then '.exe' else '';
+
+local getVolumeName(arch) = 'target-' + arch.target;
+local getLocalVolumes(arch) = [
+  {
+    name: getVolumeName(arch),
+    temp: {},
+  }
+  for arch in archs
+];
+
+local add_build_steps() = [
+  {
+    name: getStepName(arch),
+    image: build_image,
+    commands: [
+      'echo Hello World from Jsonnet on ' + arch.target + '!',
+      'cargo zigbuild --release --target ' + arch.target,
+      'cp target/' + arch.target + '/release/' + builtExecutableName(arch) + ' artifacts/' + targetExecutableName(arch),
+      'rm -rf target/' + arch.target + '/release/*',
+    ],
+    depends_on: ['Prepare'],
+    volumes: [{
+      name: getVolumeName(arch),
+      path: '/drone/src/target',
+    }],
+  }
+  for arch in archs
+];
+
+{
+  kind: 'pipeline',
+  type: 'docker',
+  name: 'default',
+  platform: {
+    arch: 'amd64',
+  },
+  steps:
+    [{
+      name: 'Prepare',
+      image: build_image,
+      commands: [
+        'mkdir artifacts',
+        'echo Using image: ' + build_image,
+        'cargo --version',
+        'rustc --version',
+      ],
+    }] +
+    add_build_steps() +
+    [
+      {
+        name: 'Show built artifacts',
+        image: build_image,
+        commands: [
+          'ls -lah artifacts',
+        ],
+        depends_on: [getStepName(a) for a in archs],
+      },
+      {
+        name: 'Create release on gitea',
+        image: 'plugins/gitea-release',
+        settings: {
+          api_key: {
+            from_secret: 'gitea_token',
+          },
+          base_url: 'https://code.kiers.eu',
+          files: 'artifacts/*',
+          checksum: 'sha256',
+        },
+        when: {
+          event: ['tag', 'promote'],
+        },
+        depends_on: ['Show built artifacts'],
+      },
+    ],
+
+  volumes: getLocalVolumes(archs),
+
+  image_pull_secrets: ['docker_private_repo'],
+}

.github/workflows/rust.yml

@@ -1,24 +0,0 @@
-name: Rust
-
-on:
-  push:
-    branches: [ main ]
-  pull_request:
-    branches: [ main ]
-
-env:
-  CARGO_TERM_COLOR: always
-
-jobs:
-  build:
-
-    runs-on: ubuntu-latest
-
-    steps:
-    - uses: actions/checkout@v2
-    - name: Upgrade Rust
-      run: rustup update
-    - name: Build
-      run: cargo build --verbose
-    - name: Run tests
-      run: cargo test --verbose

.gitignore

@@ -1 +1,2 @@
 /target
+config.yaml

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "fourth"
-version = "0.1.1"
+version = "0.1.7"
 edition = "2021"
 authors = ["LI Rui <lr_cn@outlook.com>"]
 license = "Apache-2.0"
@@ -13,12 +13,18 @@ categories = ["web-programming"]
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
+exclude = [".*"]
+
 [dependencies]
 log = "0.4"
 pretty_env_logger = "0.4"
 serde = { version = "1.0", features = ["derive"] }
-serde_yaml = "0.8"
+serde_yaml = "0.9.21"
 futures = "0.3"
 tls-parser = "0.11"
+url = "2.2.2"
+time = { version = "0.3.1", features = ["local-offset", "formatting"] }
+tokio = { version = "1.0", features = ["full"] }
 
-tokio = { version = "1.0", features = ["full"] }
+bytes = "1.1"
+byte_string = "1"

README-EN.md

@@ -1,58 +0,0 @@
-# Fourth
-
-> Hey, now we are on level 4!
-
-[![](https://img.shields.io/crates/v/fourth)](https://crates.io/crates/fourth) [![CI](https://img.shields.io/github/workflow/status/kernelerr/fourth/Rust)](https://github.com/KernelErr/fourth/actions/workflows/rust.yml)
-
-Fourth is a layer 4 proxy implemented by Rust to listen on specific ports and transfer data to remote addresses according to configuration.
-
-## Features
-
-- Listen on specific port and proxy to local or remote port
-- SNI-based rule without terminating TLS connection
-
-## Installation
-
-To gain best performance on your computer's architecture, please consider build the source code. First, you may need [Rust tool chain](https://rustup.rs/).
-
-```bash
-$ cd fourth
-$ cargo build --release
-```
-
-Binary file will be generated at `target/release/fourth`, or you can use `cargo install --path .` to install.
-
-## Configuration
-
-Fourth will read yaml format configuration file from `/etc/fourth/config.yaml`, here is an example:
-
-```yaml
-version: 1
-log: info
-
-servers:
-  example_server:
-    listen:
-      - "0.0.0.0:443"
-      - "[::]:443"
-    tls: true # Enable TLS features like SNI
-    sni:
-      proxy.example.com: proxy
-      www.example.com: nginx
-    default: ban
-  relay_server:
-    listen:
-      - "127.0.0.1:8081"
-    default: remote
-
-upstream:
-  nginx: "127.0.0.1:8080"
-  proxy: "127.0.0.1:1024"
-  other: "www.remote.example.com:8082" # proxy to remote address
-```
-
-Built-in two upstreams: ban(terminate connection immediately), echo
-
-## License
-
-Fourth is available under terms of Apache-2.0.

README-ZH.md

@@ -0,0 +1,80 @@
+# Fourth
+
+> 这一波在第四层。
+
+[![](https://img.shields.io/crates/v/fourth)](https://crates.io/crates/fourth) [![CI](https://img.shields.io/github/workflow/status/kernelerr/fourth/Rust)](https://github.com/KernelErr/fourth/actions/workflows/rust.yml)
+
+[English](/README-EN.md)
+
+**积极开发中，0.1版本迭代可能较快**
+
+Fourth是一个Rust实现的Layer 4代理，用于监听指定端口TCP/KCP流量，并根据规则转发到指定目标（目前只支持TCP）。
+
+## 功能
+
+- 监听指定端口代理到本地或远端指定端口
+- 监听指定端口，通过TLS ClientHello消息中的SNI进行分流
+- 支持KCP入站（警告：未测试）
+
+## 安装方法
+
+为了确保获得您架构下的最佳性能，请考虑自行编译，首选需要确保您拥有[Rust工具链](https://rustup.rs/)。
+
+```bash
+$ cd fourth
+$ cargo build --release
+```
+
+将在`target/release/fourth`生成二进制文件，您也可以使用`cargo install --path . `来安装二进制文件。
+
+或者您也可以使用Cargo直接安装：
+
+```bash
+$ cargo install fourth
+```
+
+或者您也可以直接从Release中下载二进制文件。
+
+## 配置
+
+Fourth使用yaml格式的配置文件，默认情况下会读取`/etc/fourth/config.yaml`，您也可以设置自定义路径到环境变量`FOURTH_CONFIG`，如下是一个最小有效配置：
+
+```yaml
+version: 1
+log: info
+
+servers:
+  proxy_server:
+    listen:
+      - "127.0.0.1:8081"
+    default: remote
+
+upstream:
+  remote: "tcp://www.remote.example.com:8082" # proxy to remote address
+```
+
+内置两个的upstream：ban（立即中断连接）、echo（返回读到的数据）。更详细的配置可以参考[示例配置](./example-config.yaml)。
+
+注意：[::]会默认同时绑定IPv4和IPv6。
+
+## 性能测试
+
+在4C2G的服务器上测试：
+
+使用Fourth代理到Nginx（直连QPS 120000）: ~70000req/s （测试命令：`wrk -t200 -c1000 -d120s --latency http://proxy-server:8081 `）
+
+使用Fourth代理到本地iperf3：8Gbps
+
+## io_uring?
+
+尽管经过了很多尝试，我们发现目前一些Rust下面的io_uring实现存在问题，我们使用的io_uring库实现尽管在吞吐量上可以做到单线程20Gbps（相比之下Tokio仅有8Gbps），但在QPS上存在性能损失较大的问题。因此在有成熟的io_uring实现之前，我们仍然选择epoll。之后我们会持续关注相关进展。
+
+可能以后会为Linux高内核版本的用户提供可选的io_uring加速。
+
+## 感谢
+
+- [tokio_kcp](https://github.com/Matrix-Zhang/tokio_kcp)
+
+## 协议
+
+Fourth以Apache-2.0协议开源。

README.md

@@ -1,66 +1,70 @@
 # Fourth
 
-> 这一波在第四层。
+> Hey, now we are on level 4!
 
 [![](https://img.shields.io/crates/v/fourth)](https://crates.io/crates/fourth) [![CI](https://img.shields.io/github/workflow/status/kernelerr/fourth/Rust)](https://github.com/KernelErr/fourth/actions/workflows/rust.yml)
 
-[English](/README-EN.md)
+**Under heavy development, version 0.1 may update frequently**
 
-Fourth是一个Rust实现的Layer 4代理，用于监听指定端口TCP流量，并根据规则转发到指定目标。
+Fourth is a layer 4 proxy implemented by Rust to listen on specific ports and transfer TCP/KCP data to remote addresses(only TCP) according to configuration.
 
-## 功能
+## Features
 
-- 监听指定端口代理到本地或远端指定端口
-- 监听指定端口，通过TLS ClientHello消息中的SNI进行分流
+- Listen on specific port and proxy to local or remote port
+- SNI-based rule without terminating TLS connection
+- Allow KCP inbound(warning: untested)
 
-## 安装方法
+## Installation
 
-为了确保获得您架构下的最佳性能，请考虑自行编译，首选需要确保您拥有[Rust工具链](https://rustup.rs/)。
+To gain best performance on your computer's architecture, please consider build the source code. First, you may need [Rust tool chain](https://rustup.rs/).
 
 ```bash
 $ cd fourth
 $ cargo build --release
 ```
 
-将在`target/release/fourth`生成二进制文件，您也可以使用`cargo install --path . `来安装二进制文件。
+Binary file will be generated at `target/release/fourth`, or you can use `cargo install --path .` to install.
 
-## 配置
+Or you can use Cargo to install Fourth:
 
-Fourth使用yaml格式的配置文件，默认情况下会读取`/etc/fourth/config.yaml`，如下是一个示例配置。
+```bash
+$ cargo install fourth
+```
+
+Or you can download binary file form the Release page.
+
+## Configuration
+
+Fourth will read yaml format configuration file from `/etc/fourth/config.yaml`, and you can set custom path to environment variable `FOURTH_CONFIG`, here is an minimal viable example:
 
 ```yaml
 version: 1
 log: info
 
 servers:
-  example_server:
-    listen:
-      - "0.0.0.0:443"
-      - "[::]:443"
-    tls: true # 启动SNI分流，将根据TLS请求中的主机名分流
-    sni:
-      proxy.example.com: proxy
-      www.example.com: nginx
-    default: ban
-  relay_server:
+  proxy_server:
     listen:
       - "127.0.0.1:8081"
     default: remote
 
 upstream:
-  nginx: "127.0.0.1:8080"
-  proxy: "127.0.0.1:1024"
-  other: "www.remote.example.com:8082" # 代理到远端地址
+  remote: "tcp://www.remote.example.com:8082" # proxy to remote address
 ```
 
-内置两个的upstream：ban（立即中断连接）、echo（返回读到的数据）。
+Built-in two upstreams: ban(terminate connection immediately), echo. For detailed configuration, check [this example](./example-config.yaml).
 
-## io_uring?
+## Performance Benchmark
 
-尽管经过了很多尝试，我们发现目前一些Rust下面的io_uring实现存在问题，我们使用的io_uring库实现尽管在吞吐量上可以做到单线程20Gbps（相比之下Tokio仅有8Gbps），但在QPS上存在性能损失较大的问题。因此在有成熟的io_uring实现之前，我们仍然选择epoll。之后我们会持续关注相关进展。
+Tested on 4C2G server:
 
-可能以后会为Linux高内核版本的用户提供可选的io_uring加速。
+Use fourth to proxy to Nginx(QPS of direct connection: ~120000): ~70000 req/s (Command: `wrk -t200 -c1000 -d120s --latency http://proxy-server:8081`)
 
-## 协议
+Use fourth to proxy to local iperf3: 8Gbps
 
-Fourth以Apache-2.0协议开源。
+## Thanks
+
+- [tokio_kcp](https://github.com/Matrix-Zhang/tokio_kcp)
+
+## License
+
+Fourth is available under terms of Apache-2.0.

config.yaml.example

@@ -0,0 +1,16 @@
+version: 1
+log: debug
+
+servers:
+  example_server:
+    listen:
+      - "0.0.0.0:8443"
+    tls: true # Enable TLS features like SNI filtering
+    sni:
+      api.example.org: example-api
+      www.example.org: gh-proxy
+    default: ban
+
+upstream:
+  proxy: "tcp://new-www.example.org:443" # Connect over IPv4 or IPv6 to new-www.example.org:443
+  example-api: "tcp6://api-v1.example.com:443" # Connect over IPv6 to api-v1.example.com:443

example-config.yaml

@@ -15,8 +15,13 @@ servers:
     listen:
       - "127.0.0.1:8081"
     default: remote
+  kcp_server:
+    protocol: kcp # default TCP
+    listen:
+      - "127.0.0.1:8082"
+    default: echo
 
 upstream:
-  nginx: "127.0.0.1:8080"
-  proxy: "127.0.0.1:1024"
-  other: "www.remote.example.com:8082" # proxy to remote address
+  nginx: "tcp://127.0.0.1:8080"
+  proxy: "tcp://127.0.0.1:1024"
+  remote: "tcp://www.remote.example.com:8082" # proxy to remote address

src/config.rs

@@ -1,12 +1,24 @@
-use log::debug;
+use crate::servers::upstream_address::UpstreamAddress;
+use log::{debug, warn};
 use serde::Deserialize;
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet};
 use std::fs::File;
 use std::io::{Error as IOError, Read};
+use std::net::SocketAddr;
+use tokio::sync::Mutex;
+use url::Url;
 
 #[derive(Debug, Clone)]
 pub struct Config {
-    pub base: BaseConfig,
+    pub base: ParsedConfig,
+}
+
+#[derive(Debug, Default, Deserialize, Clone)]
+pub struct ParsedConfig {
+    pub version: i32,
+    pub log: Option<String>,
+    pub servers: HashMap<String, ServerConfig>,
+    pub upstream: HashMap<String, Upstream>,
 }
 
 #[derive(Debug, Default, Deserialize, Clone)]
@@ -20,11 +32,61 @@ pub struct BaseConfig {
 #[derive(Debug, Default, Deserialize, Clone)]
 pub struct ServerConfig {
     pub listen: Vec<String>,
+    pub protocol: Option<String>,
     pub tls: Option<bool>,
     pub sni: Option<HashMap<String, String>>,
     pub default: Option<String>,
 }
 
+#[derive(Debug, Clone, Deserialize)]
+pub enum Upstream {
+    Ban,
+    Echo,
+    Custom(CustomUpstream),
+}
+
+#[derive(Debug)]
+struct Addr(Mutex<UpstreamAddress>);
+
+impl Default for Addr {
+    fn default() -> Self {
+        Self(Default::default())
+    }
+}
+
+impl Clone for Addr {
+    fn clone(&self) -> Self {
+        tokio::task::block_in_place(|| Self(Mutex::new(self.0.blocking_lock().clone())))
+    }
+}
+
+#[derive(Debug, Clone, Deserialize)]
+pub struct CustomUpstream {
+    pub name: String,
+    pub addr: String,
+    pub protocol: String,
+    #[serde(skip_deserializing)]
+    addresses: Addr,
+}
+
+impl CustomUpstream {
+    pub async fn resolve_addresses(&self) -> std::io::Result<Vec<SocketAddr>> {
+        let mut addr = self.addresses.0.lock().await;
+        addr.resolve((*self.protocol).into()).await
+    }
+}
+
+impl Default for CustomUpstream {
+    fn default() -> Self {
+        Self {
+            name: Default::default(),
+            addr: Default::default(),
+            protocol: Default::default(),
+            addresses: Default::default(),
+        }
+    }
+}
+
 #[derive(Debug)]
 pub enum ConfigError {
     IO(IOError),
@@ -40,29 +102,154 @@ impl Config {
     }
 }
 
-fn load_config(path: &str) -> Result<BaseConfig, ConfigError> {
+fn load_config(path: &str) -> Result<ParsedConfig, ConfigError> {
     let mut contents = String::new();
     let mut file = (File::open(path))?;
     (file.read_to_string(&mut contents))?;
 
-    let parsed: BaseConfig = serde_yaml::from_str(&contents)?;
+    let base: BaseConfig = serde_yaml::from_str(&contents)?;
 
-    if parsed.version != 1 {
+    if base.version != 1 {
         return Err(ConfigError::Custom(
             "Unsupported config version".to_string(),
         ));
     }
 
-    let log_level = parsed.log.clone().unwrap_or_else(|| "info".to_string());
+    let log_level = base.log.clone().unwrap_or_else(|| "info".to_string());
     if !log_level.eq("disable") {
         std::env::set_var("FOURTH_LOG", log_level.clone());
         pretty_env_logger::init_custom_env("FOURTH_LOG");
         debug!("Set log level to {}", log_level);
     }
 
-    debug!("Config version {}", parsed.version);
+    debug!("Config version {}", base.version);
 
-    Ok(parsed)
+    let mut parsed_upstream: HashMap<String, Upstream> = HashMap::new();
+
+    for (name, upstream) in base.upstream.iter() {
+        let upstream_url = match Url::parse(upstream) {
+            Ok(url) => url,
+            Err(_) => {
+                return Err(ConfigError::Custom(format!(
+                    "Invalid upstream url {}",
+                    upstream
+                )))
+            }
+        };
+
+        let upstream_host = match upstream_url.host_str() {
+            Some(host) => host,
+            None => {
+                return Err(ConfigError::Custom(format!(
+                    "Invalid upstream url {}",
+                    upstream
+                )))
+            }
+        };
+
+        let upsteam_port = match upstream_url.port_or_known_default() {
+            Some(port) => port,
+            None => {
+                return Err(ConfigError::Custom(format!(
+                    "Invalid upstream url {}",
+                    upstream
+                )))
+            }
+        };
+
+        match upstream_url.scheme() {
+            "tcp" | "tcp4" | "tcp6" => {}
+            _ => {
+                return Err(ConfigError::Custom(format!(
+                    "Invalid upstream scheme {}",
+                    upstream
+                )))
+            }
+        }
+
+        parsed_upstream.insert(
+            name.to_string(),
+            Upstream::Custom(CustomUpstream {
+                name: name.to_string(),
+                addr: format!("{}:{}", upstream_host, upsteam_port),
+                protocol: upstream_url.scheme().to_string(),
+                addresses: Addr(Mutex::new(UpstreamAddress::new(format!(
+                    "{}:{}",
+                    upstream_host, upsteam_port
+                )))),
+                ..Default::default()
+            }),
+        );
+    }
+
+    parsed_upstream.insert("ban".to_string(), Upstream::Ban);
+
+    parsed_upstream.insert("echo".to_string(), Upstream::Echo);
+
+    let parsed = ParsedConfig {
+        version: base.version,
+        log: base.log,
+        servers: base.servers,
+        upstream: parsed_upstream,
+    };
+
+    verify_config(parsed)
+}
+
+fn verify_config(config: ParsedConfig) -> Result<ParsedConfig, ConfigError> {
+    let mut used_upstreams: HashSet<String> = HashSet::new();
+    let mut upstream_names: HashSet<String> = HashSet::new();
+    let mut listen_addresses: HashSet<String> = HashSet::new();
+
+    // Check for duplicate upstream names
+    for (name, _) in config.upstream.iter() {
+        if upstream_names.contains(name) {
+            return Err(ConfigError::Custom(format!(
+                "Duplicate upstream name {}",
+                name
+            )));
+        }
+
+        upstream_names.insert(name.to_string());
+    }
+
+    for (_, server) in config.servers.clone() {
+        // check for duplicate listen addresses
+        for listen in server.listen {
+            if listen_addresses.contains(&listen) {
+                return Err(ConfigError::Custom(format!(
+                    "Duplicate listen address {}",
+                    listen
+                )));
+            }
+
+            listen_addresses.insert(listen.to_string());
+        }
+
+        if server.tls.unwrap_or_default() && server.sni.is_some() {
+            for (_, val) in server.sni.unwrap() {
+                used_upstreams.insert(val.to_string());
+            }
+        }
+
+        if server.default.is_some() {
+            used_upstreams.insert(server.default.unwrap().to_string());
+        }
+
+        for key in &used_upstreams {
+            if !config.upstream.contains_key(key) {
+                return Err(ConfigError::Custom(format!("Upstream {} not found", key)));
+            }
+        }
+    }
+
+    for key in &upstream_names {
+        if !used_upstreams.contains(key) && !key.eq("echo") && !key.eq("ban") {
+            warn!("Upstream {} not used", key);
+        }
+    }
+
+    Ok(config)
 }
 
 impl From<IOError> for ConfigError {
@@ -86,7 +273,7 @@ mod tests {
         let config = Config::new("tests/config.yaml").unwrap();
         assert_eq!(config.base.version, 1);
         assert_eq!(config.base.log.unwrap(), "disable");
-        assert_eq!(config.base.servers.len(), 2);
-        assert_eq!(config.base.upstream.len(), 2);
+        assert_eq!(config.base.servers.len(), 5);
+        assert_eq!(config.base.upstream.len(), 3 + 2); // Add ban and echo upstreams
     }
 }

src/main.rs

@@ -1,13 +1,18 @@
 mod config;
+mod plugins;
 mod servers;
 
 use crate::config::Config;
 use crate::servers::Server;
 
 use log::{debug, error};
+use std::env;
+use std::path::Path;
 
 fn main() {
-    let config = match Config::new("/etc/fourth/config.yaml") {
+    let config_path = find_config();
+
+    let config = match Config::new(&config_path) {
         Ok(config) => config,
         Err(e) => {
             println!("Could not load config: {:?}", e);
@@ -19,6 +24,21 @@ fn main() {
     let mut server = Server::new(config.base);
     debug!("{:?}", server);
 
-    let res = server.run();
-    error!("Server returned an error: {:?}", res);
+    let _ = server.run();
+    error!("Server ended with errors");
+}
+
+fn find_config() -> String {
+    let config_path =
+        env::var("FOURTH_CONFIG").unwrap_or_else(|_| "/etc/fourth/config.yaml".to_string());
+
+    if Path::new(&config_path).exists() {
+        return config_path;
+    }
+
+    if Path::new("config.yaml").exists() {
+        return String::from("config.yaml");
+    }
+
+    String::from("")
 }

src/plugins/kcp/config.rs

@@ -0,0 +1,110 @@
+use std::{io::Write, time::Duration};
+
+use kcp::Kcp;
+
+/// Kcp Delay Config
+#[derive(Debug, Clone, Copy)]
+pub struct KcpNoDelayConfig {
+    /// Enable nodelay
+    pub nodelay: bool,
+    /// Internal update interval (ms)
+    pub interval: i32,
+    /// ACK number to enable fast resend
+    pub resend: i32,
+    /// Disable congetion control
+    pub nc: bool,
+}
+
+impl Default for KcpNoDelayConfig {
+    fn default() -> KcpNoDelayConfig {
+        KcpNoDelayConfig {
+            nodelay: false,
+            interval: 100,
+            resend: 0,
+            nc: false,
+        }
+    }
+}
+
+#[allow(unused)]
+impl KcpNoDelayConfig {
+    /// Get a fastest configuration
+    ///
+    /// 1. Enable NoDelay
+    /// 2. Set ticking interval to be 10ms
+    /// 3. Set fast resend to be 2
+    /// 4. Disable congestion control
+    pub fn fastest() -> KcpNoDelayConfig {
+        KcpNoDelayConfig {
+            nodelay: true,
+            interval: 10,
+            resend: 2,
+            nc: true,
+        }
+    }
+
+    /// Get a normal configuration
+    ///
+    /// 1. Disable NoDelay
+    /// 2. Set ticking interval to be 40ms
+    /// 3. Disable fast resend
+    /// 4. Enable congestion control
+    pub fn normal() -> KcpNoDelayConfig {
+        KcpNoDelayConfig {
+            nodelay: false,
+            interval: 40,
+            resend: 0,
+            nc: false,
+        }
+    }
+}
+
+/// Kcp Config
+#[derive(Debug, Clone, Copy)]
+pub struct KcpConfig {
+    /// Max Transmission Unit
+    pub mtu: usize,
+    /// nodelay
+    pub nodelay: KcpNoDelayConfig,
+    /// Send window size
+    pub wnd_size: (u16, u16),
+    /// Session expire duration, default is 90 seconds
+    pub session_expire: Duration,
+    /// Flush KCP state immediately after write
+    pub flush_write: bool,
+    /// Flush ACKs immediately after input
+    pub flush_acks_input: bool,
+    /// Stream mode
+    pub stream: bool,
+}
+
+impl Default for KcpConfig {
+    fn default() -> KcpConfig {
+        KcpConfig {
+            mtu: 1400,
+            nodelay: KcpNoDelayConfig::normal(),
+            wnd_size: (256, 256),
+            session_expire: Duration::from_secs(90),
+            flush_write: false,
+            flush_acks_input: false,
+            stream: true,
+        }
+    }
+}
+
+impl KcpConfig {
+    /// Applies config onto `Kcp`
+    #[doc(hidden)]
+    pub fn apply_config<W: Write>(&self, k: &mut Kcp<W>) {
+        k.set_mtu(self.mtu).expect("invalid MTU");
+
+        k.set_nodelay(
+            self.nodelay.nodelay,
+            self.nodelay.interval,
+            self.nodelay.resend,
+            self.nodelay.nc,
+        );
+
+        k.set_wndsize(self.wnd_size.0, self.wnd_size.1);
+    }
+}

src/plugins/kcp/listener.rs

@@ -0,0 +1,128 @@
+use std::{
+    io::{self, ErrorKind},
+    net::SocketAddr,
+    sync::Arc,
+    time::Duration,
+};
+
+use byte_string::ByteStr;
+use kcp::{Error as KcpError, KcpResult};
+use log::{debug, error, trace};
+use tokio::{
+    net::{ToSocketAddrs, UdpSocket},
+    sync::mpsc,
+    task::JoinHandle,
+    time,
+};
+
+use crate::plugins::kcp::{config::KcpConfig, session::KcpSessionManager, stream::KcpStream};
+
+#[allow(unused)]
+pub struct KcpListener {
+    udp: Arc<UdpSocket>,
+    accept_rx: mpsc::Receiver<(KcpStream, SocketAddr)>,
+    task_watcher: JoinHandle<()>,
+}
+
+impl Drop for KcpListener {
+    fn drop(&mut self) {
+        self.task_watcher.abort();
+    }
+}
+
+impl KcpListener {
+    pub async fn bind<A: ToSocketAddrs>(config: KcpConfig, addr: A) -> KcpResult<KcpListener> {
+        let udp = UdpSocket::bind(addr).await?;
+        let udp = Arc::new(udp);
+        let server_udp = udp.clone();
+
+        let (accept_tx, accept_rx) = mpsc::channel(1024 /* backlogs */);
+        let task_watcher = tokio::spawn(async move {
+            let (close_tx, mut close_rx) = mpsc::channel(64);
+
+            let mut sessions = KcpSessionManager::new();
+            let mut packet_buffer = [0u8; 65536];
+            loop {
+                tokio::select! {
+                    conv = close_rx.recv() => {
+                        let conv = conv.expect("close_tx closed unexpectly");
+                        sessions.close_conv(conv);
+                        trace!("session conv: {} removed", conv);
+                    }
+
+                    recv_res = udp.recv_from(&mut packet_buffer) => {
+                        match recv_res {
+                            Err(err) => {
+                                error!("udp.recv_from failed, error: {}", err);
+                                time::sleep(Duration::from_secs(1)).await;
+                            }
+                            Ok((n, peer_addr)) => {
+                                let packet = &mut packet_buffer[..n];
+
+                                log::trace!("received peer: {}, {:?}", peer_addr, ByteStr::new(packet));
+
+                                let mut conv = kcp::get_conv(packet);
+                                if conv == 0 {
+                                    // Allocate a conv for client.
+                                    conv = sessions.alloc_conv();
+                                    debug!("allocate {} conv for peer: {}", conv, peer_addr);
+
+                                    kcp::set_conv(packet, conv);
+                                }
+
+                                let session = match sessions.get_or_create(&config, conv, &udp, peer_addr, &close_tx) {
+                                    Ok((s, created)) => {
+                                        if created {
+                                            // Created a new session, constructed a new accepted client
+                                            let stream = KcpStream::with_session(s.clone());
+                                            if let Err(..) = accept_tx.try_send((stream, peer_addr)) {
+                                                debug!("failed to create accepted stream due to channel failure");
+
+                                                // remove it from session
+                                                sessions.close_conv(conv);
+                                                continue;
+                                            }
+                                        }
+
+                                        s
+                                    },
+                                    Err(err) => {
+                                        error!("failed to create session, error: {}, peer: {}, conv: {}", err, peer_addr, conv);
+                                        continue;
+                                    }
+                                };
+
+                                // let mut kcp = session.kcp_socket().lock().await;
+                                // if let Err(err) = kcp.input(packet) {
+                                //     error!("kcp.input failed, peer: {}, conv: {}, error: {}, packet: {:?}", peer_addr, conv, err, ByteStr::new(packet));
+                                // }
+                                session.input(packet).await;
+                            }
+                        }
+                    }
+                }
+            }
+        });
+
+        Ok(KcpListener {
+            udp: server_udp,
+            accept_rx,
+            task_watcher,
+        })
+    }
+
+    pub async fn accept(&mut self) -> KcpResult<(KcpStream, SocketAddr)> {
+        match self.accept_rx.recv().await {
+            Some(s) => Ok(s),
+            None => Err(KcpError::IoError(io::Error::new(
+                ErrorKind::Other,
+                "accept channel closed unexpectly",
+            ))),
+        }
+    }
+
+    #[allow(unused)]
+    pub fn local_addr(&self) -> io::Result<SocketAddr> {
+        self.udp.local_addr()
+    }
+}

src/plugins/kcp/mod.rs

@@ -0,0 +1,14 @@
+//! Library of KCP on Tokio
+
+pub use self::{
+    config::{KcpConfig, KcpNoDelayConfig},
+    listener::KcpListener,
+    stream::KcpStream,
+};
+
+mod config;
+mod listener;
+mod session;
+mod skcp;
+mod stream;
+mod utils;

src/plugins/kcp/session.rs

@@ -0,0 +1,256 @@
+use std::{
+    collections::{hash_map::Entry, HashMap},
+    net::SocketAddr,
+    sync::{
+        atomic::{AtomicBool, Ordering},
+        Arc,
+    },
+    time::Duration,
+};
+
+use byte_string::ByteStr;
+use kcp::KcpResult;
+use log::{error, trace};
+use tokio::{
+    net::UdpSocket,
+    sync::{mpsc, Mutex},
+    time::{self, Instant},
+};
+
+use crate::plugins::kcp::{skcp::KcpSocket, KcpConfig};
+
+pub struct KcpSession {
+    socket: Mutex<KcpSocket>,
+    closed: AtomicBool,
+    session_expire: Duration,
+    session_close_notifier: Option<mpsc::Sender<u32>>,
+    input_tx: mpsc::Sender<Vec<u8>>,
+}
+
+impl KcpSession {
+    fn new(
+        socket: KcpSocket,
+        session_expire: Duration,
+        session_close_notifier: Option<mpsc::Sender<u32>>,
+        input_tx: mpsc::Sender<Vec<u8>>,
+    ) -> KcpSession {
+        KcpSession {
+            socket: Mutex::new(socket),
+            closed: AtomicBool::new(false),
+            session_expire,
+            session_close_notifier,
+            input_tx,
+        }
+    }
+
+    pub fn new_shared(
+        socket: KcpSocket,
+        session_expire: Duration,
+        session_close_notifier: Option<mpsc::Sender<u32>>,
+    ) -> Arc<KcpSession> {
+        let is_client = session_close_notifier.is_none();
+
+        let (input_tx, mut input_rx) = mpsc::channel(64);
+
+        let udp_socket = socket.udp_socket().clone();
+
+        let session = Arc::new(KcpSession::new(
+            socket,
+            session_expire,
+            session_close_notifier,
+            input_tx,
+        ));
+
+        {
+            let session = session.clone();
+            tokio::spawn(async move {
+                let mut input_buffer = [0u8; 65536];
+                let update_timer = time::sleep(Duration::from_millis(10));
+                tokio::pin!(update_timer);
+
+                loop {
+                    tokio::select! {
+                        // recv() then input()
+                        // Drives the KCP machine forward
+                        recv_result = udp_socket.recv(&mut input_buffer), if is_client => {
+                            match recv_result {
+                                Err(err) => {
+                                    error!("[SESSION] UDP recv failed, error: {}", err);
+                                }
+                                Ok(n) => {
+                                    let input_buffer = &input_buffer[..n];
+                                    trace!("[SESSION] UDP recv {} bytes, going to input {:?}", n, ByteStr::new(input_buffer));
+
+                                    let mut socket = session.socket.lock().await;
+
+                                    match socket.input(input_buffer) {
+                                        Ok(true) => {
+                                            trace!("[SESSION] UDP input {} bytes and waked sender/receiver", n);
+                                        }
+                                        Ok(false) => {}
+                                        Err(err) => {
+                                            error!("[SESSION] UDP input {} bytes error: {}, input buffer {:?}", n, err, ByteStr::new(input_buffer));
+                                        }
+                                    }
+                                }
+                            }
+                        }
+
+                        // bytes received from listener socket
+                        input_opt = input_rx.recv() => {
+                            if let Some(input_buffer) = input_opt {
+                                let mut socket = session.socket.lock().await;
+                                match socket.input(&input_buffer) {
+                                    Ok(..) => {
+                                        trace!("[SESSION] UDP input {} bytes from channel {:?}", input_buffer.len(), ByteStr::new(&input_buffer));
+                                    }
+                                    Err(err) => {
+                                        error!("[SESSION] UDP input {} bytes from channel failed, error: {}, input buffer {:?}",
+                                               input_buffer.len(), err, ByteStr::new(&input_buffer));
+                                    }
+                                }
+                            }
+                        }
+
+                        // Call update() in period
+                        _ = &mut update_timer => {
+                            let mut socket = session.socket.lock().await;
+
+                            let is_closed = session.closed.load(Ordering::Acquire);
+                            if is_closed && socket.can_close() {
+                                trace!("[SESSION] KCP session closed");
+                                break;
+                            }
+
+                            // server socket expires
+                            if !is_client {
+                                // If this is a server stream, close it automatically after a period of time
+                                let last_update_time = socket.last_update_time();
+                                let elapsed = last_update_time.elapsed();
+
+                                if elapsed > session.session_expire {
+                                    if elapsed > session.session_expire * 2 {
+                                        // Force close. Client may have already gone.
+                                        trace!(
+                                            "[SESSION] force close inactive session, conv: {}, last_update: {}s ago",
+                                            socket.conv(),
+                                            elapsed.as_secs()
+                                        );
+                                        break;
+                                    }
+
+                                    if !is_closed {
+                                        trace!(
+                                            "[SESSION] closing inactive session, conv: {}, last_update: {}s ago",
+                                            socket.conv(),
+                                            elapsed.as_secs()
+                                        );
+                                        session.closed.store(true, Ordering::Release);
+                                    }
+                                }
+                            }
+
+                            match socket.update() {
+                                Ok(next_next) => {
+                                    update_timer.as_mut().reset(Instant::from_std(next_next));
+                                }
+                                Err(err) => {
+                                    error!("[SESSION] KCP update failed, error: {}", err);
+                                    update_timer.as_mut().reset(Instant::now() + Duration::from_millis(10));
+                                }
+                            }
+                        }
+                    }
+                }
+
+                {
+                    // Close the socket.
+                    // Wake all pending tasks and let all send/recv return EOF
+
+                    let mut socket = session.socket.lock().await;
+                    socket.close();
+                }
+
+                if let Some(ref notifier) = session.session_close_notifier {
+                    let socket = session.socket.lock().await;
+                    let _ = notifier.send(socket.conv()).await;
+                }
+            });
+        }
+
+        session
+    }
+
+    pub fn kcp_socket(&self) -> &Mutex<KcpSocket> {
+        &self.socket
+    }
+
+    pub fn close(&self) {
+        self.closed.store(true, Ordering::Release);
+    }
+
+    pub async fn input(&self, buf: &[u8]) {
+        self.input_tx
+            .send(buf.to_owned())
+            .await
+            .expect("input channel closed")
+    }
+}
+
+pub struct KcpSessionManager {
+    sessions: HashMap<u32, Arc<KcpSession>>,
+    next_free_conv: u32,
+}
+
+impl KcpSessionManager {
+    pub fn new() -> KcpSessionManager {
+        KcpSessionManager {
+            sessions: HashMap::new(),
+            next_free_conv: 0,
+        }
+    }
+
+    pub fn close_conv(&mut self, conv: u32) {
+        self.sessions.remove(&conv);
+    }
+
+    pub fn alloc_conv(&mut self) -> u32 {
+        loop {
+            let (mut c, _) = self.next_free_conv.overflowing_add(1);
+            if c == 0 {
+                let (nc, _) = c.overflowing_add(1);
+                c = nc;
+            }
+            self.next_free_conv = c;
+
+            if self.sessions.get(&self.next_free_conv).is_none() {
+                let conv = self.next_free_conv;
+                return conv;
+            }
+        }
+    }
+
+    pub fn get_or_create(
+        &mut self,
+        config: &KcpConfig,
+        conv: u32,
+        udp: &Arc<UdpSocket>,
+        peer_addr: SocketAddr,
+        session_close_notifier: &mpsc::Sender<u32>,
+    ) -> KcpResult<(Arc<KcpSession>, bool)> {
+        match self.sessions.entry(conv) {
+            Entry::Occupied(occ) => Ok((occ.get().clone(), false)),
+            Entry::Vacant(vac) => {
+                let socket = KcpSocket::new(config, conv, udp.clone(), peer_addr, config.stream)?;
+                let session = KcpSession::new_shared(
+                    socket,
+                    config.session_expire,
+                    Some(session_close_notifier.clone()),
+                );
+                trace!("created session for conv: {}, peer: {}", conv, peer_addr);
+                vac.insert(session.clone());
+                Ok((session, true))
+            }
+        }
+    }
+}

src/plugins/kcp/skcp.rs

@@ -0,0 +1,288 @@
+use std::{
+    io::{self, ErrorKind, Write},
+    net::SocketAddr,
+    sync::Arc,
+    task::{Context, Poll, Waker},
+    time::{Duration, Instant},
+};
+
+use futures::future;
+use kcp::{Error as KcpError, Kcp, KcpResult};
+use log::{error, trace};
+use tokio::{net::UdpSocket, sync::mpsc};
+
+use crate::plugins::kcp::{utils::now_millis, KcpConfig};
+
+/// Writer for sending packets to the underlying UdpSocket
+struct UdpOutput {
+    socket: Arc<UdpSocket>,
+    target_addr: SocketAddr,
+    delay_tx: mpsc::UnboundedSender<Vec<u8>>,
+}
+
+impl UdpOutput {
+    /// Create a new Writer for writing packets to UdpSocket
+    pub fn new(socket: Arc<UdpSocket>, target_addr: SocketAddr) -> UdpOutput {
+        let (delay_tx, mut delay_rx) = mpsc::unbounded_channel::<Vec<u8>>();
+
+        {
+            let socket = socket.clone();
+            tokio::spawn(async move {
+                while let Some(buf) = delay_rx.recv().await {
+                    if let Err(err) = socket.send_to(&buf, target_addr).await {
+                        error!("[SEND] UDP delayed send failed, error: {}", err);
+                    }
+                }
+            });
+        }
+
+        UdpOutput {
+            socket,
+            target_addr,
+            delay_tx,
+        }
+    }
+}
+
+impl Write for UdpOutput {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        match self.socket.try_send_to(buf, self.target_addr) {
+            Ok(n) => Ok(n),
+            Err(ref err) if err.kind() == ErrorKind::WouldBlock => {
+                // send return EAGAIN
+                // ignored as packet was lost in transmission
+                trace!(
+                    "[SEND] UDP send EAGAIN, packet.size: {} bytes, delayed send",
+                    buf.len()
+                );
+
+                self.delay_tx
+                    .send(buf.to_owned())
+                    .expect("channel closed unexpectly");
+
+                Ok(buf.len())
+            }
+            Err(err) => Err(err),
+        }
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+pub struct KcpSocket {
+    kcp: Kcp<UdpOutput>,
+    last_update: Instant,
+    socket: Arc<UdpSocket>,
+    flush_write: bool,
+    flush_ack_input: bool,
+    sent_first: bool,
+    pending_sender: Option<Waker>,
+    pending_receiver: Option<Waker>,
+    closed: bool,
+}
+
+impl KcpSocket {
+    pub fn new(
+        c: &KcpConfig,
+        conv: u32,
+        socket: Arc<UdpSocket>,
+        target_addr: SocketAddr,
+        stream: bool,
+    ) -> KcpResult<KcpSocket> {
+        let output = UdpOutput::new(socket.clone(), target_addr);
+        let mut kcp = if stream {
+            Kcp::new_stream(conv, output)
+        } else {
+            Kcp::new(conv, output)
+        };
+        c.apply_config(&mut kcp);
+
+        // Ask server to allocate one
+        if conv == 0 {
+            kcp.input_conv();
+        }
+
+        kcp.update(now_millis())?;
+
+        Ok(KcpSocket {
+            kcp,
+            last_update: Instant::now(),
+            socket,
+            flush_write: c.flush_write,
+            flush_ack_input: c.flush_acks_input,
+            sent_first: false,
+            pending_sender: None,
+            pending_receiver: None,
+            closed: false,
+        })
+    }
+
+    /// Call every time you got data from transmission
+    pub fn input(&mut self, buf: &[u8]) -> KcpResult<bool> {
+        match self.kcp.input(buf) {
+            Ok(..) => {}
+            Err(KcpError::ConvInconsistent(expected, actual)) => {
+                trace!(
+                    "[INPUT] Conv expected={} actual={} ignored",
+                    expected,
+                    actual
+                );
+                return Ok(false);
+            }
+            Err(err) => return Err(err),
+        }
+        self.last_update = Instant::now();
+
+        if self.flush_ack_input {
+            self.kcp.flush_ack()?;
+        }
+
+        Ok(self.try_wake_pending_waker())
+    }
+
+    /// Call if you want to send some data
+    pub fn poll_send(&mut self, cx: &mut Context<'_>, mut buf: &[u8]) -> Poll<KcpResult<usize>> {
+        if self.closed {
+            return Ok(0).into();
+        }
+
+        // If:
+        //     1. Have sent the first packet (asking for conv)
+        //     2. Too many pending packets
+        if self.sent_first
+            && (self.kcp.wait_snd() >= self.kcp.snd_wnd() as usize || self.kcp.waiting_conv())
+        {
+            trace!(
+                "[SEND] waitsnd={} sndwnd={} excceeded or waiting conv={}",
+                self.kcp.wait_snd(),
+                self.kcp.snd_wnd(),
+                self.kcp.waiting_conv()
+            );
+            self.pending_sender = Some(cx.waker().clone());
+            return Poll::Pending;
+        }
+
+        if !self.sent_first && self.kcp.waiting_conv() && buf.len() > self.kcp.mss() as usize {
+            buf = &buf[..self.kcp.mss() as usize];
+        }
+
+        let n = self.kcp.send(buf)?;
+        self.sent_first = true;
+        self.last_update = Instant::now();
+
+        if self.flush_write {
+            self.kcp.flush()?;
+        }
+
+        Ok(n).into()
+    }
+
+    /// Call if you want to send some data
+    #[allow(dead_code)]
+    pub async fn send(&mut self, buf: &[u8]) -> KcpResult<usize> {
+        future::poll_fn(|cx| self.poll_send(cx, buf)).await
+    }
+
+    #[allow(dead_code)]
+    pub fn try_recv(&mut self, buf: &mut [u8]) -> KcpResult<usize> {
+        if self.closed {
+            return Ok(0);
+        }
+        self.kcp.recv(buf)
+    }
+
+    pub fn poll_recv(&mut self, cx: &mut Context<'_>, buf: &mut [u8]) -> Poll<KcpResult<usize>> {
+        if self.closed {
+            return Ok(0).into();
+        }
+
+        match self.kcp.recv(buf) {
+            Ok(n) => Ok(n).into(),
+            Err(KcpError::RecvQueueEmpty) => {
+                self.pending_receiver = Some(cx.waker().clone());
+                Poll::Pending
+            }
+            Err(err) => Err(err).into(),
+        }
+    }
+
+    #[allow(dead_code)]
+    pub async fn recv(&mut self, buf: &mut [u8]) -> KcpResult<usize> {
+        future::poll_fn(|cx| self.poll_recv(cx, buf)).await
+    }
+
+    pub fn flush(&mut self) -> KcpResult<()> {
+        self.kcp.flush()?;
+        self.last_update = Instant::now();
+        Ok(())
+    }
+
+    fn try_wake_pending_waker(&mut self) -> bool {
+        let mut waked = false;
+
+        if self.pending_sender.is_some()
+            && self.kcp.wait_snd() < self.kcp.snd_wnd() as usize
+            && !self.kcp.waiting_conv()
+        {
+            let waker = self.pending_sender.take().unwrap();
+            waker.wake();
+
+            waked = true;
+        }
+
+        if self.pending_receiver.is_some() {
+            if let Ok(peek) = self.kcp.peeksize() {
+                if peek > 0 {
+                    let waker = self.pending_receiver.take().unwrap();
+                    waker.wake();
+
+                    waked = true;
+                }
+            }
+        }
+
+        waked
+    }
+
+    pub fn update(&mut self) -> KcpResult<Instant> {
+        let now = now_millis();
+        self.kcp.update(now)?;
+        let next = self.kcp.check(now);
+
+        self.try_wake_pending_waker();
+
+        Ok(Instant::now() + Duration::from_millis(next as u64))
+    }
+
+    pub fn close(&mut self) {
+        self.closed = true;
+        if let Some(w) = self.pending_sender.take() {
+            w.wake();
+        }
+        if let Some(w) = self.pending_receiver.take() {
+            w.wake();
+        }
+    }
+
+    pub fn udp_socket(&self) -> &Arc<UdpSocket> {
+        &self.socket
+    }
+
+    pub fn can_close(&self) -> bool {
+        self.kcp.wait_snd() == 0
+    }
+
+    pub fn conv(&self) -> u32 {
+        self.kcp.conv()
+    }
+
+    pub fn peek_size(&self) -> KcpResult<usize> {
+        self.kcp.peeksize()
+    }
+
+    pub fn last_update_time(&self) -> Instant {
+        self.last_update
+    }
+}

src/plugins/kcp/stream.rs

@@ -0,0 +1,183 @@
+use std::{
+    io::{self, ErrorKind},
+    net::{IpAddr, SocketAddr},
+    pin::Pin,
+    sync::Arc,
+    task::{Context, Poll},
+};
+
+use futures::{future, ready};
+use kcp::{Error as KcpError, KcpResult};
+use log::trace;
+use tokio::{
+    io::{AsyncRead, AsyncWrite, ReadBuf},
+    net::UdpSocket,
+};
+
+use crate::plugins::kcp::{config::KcpConfig, session::KcpSession, skcp::KcpSocket};
+
+pub struct KcpStream {
+    session: Arc<KcpSession>,
+    recv_buffer: Vec<u8>,
+    recv_buffer_pos: usize,
+    recv_buffer_cap: usize,
+}
+
+impl Drop for KcpStream {
+    fn drop(&mut self) {
+        self.session.close();
+    }
+}
+
+#[allow(unused)]
+impl KcpStream {
+    pub async fn connect(config: &KcpConfig, addr: SocketAddr) -> KcpResult<KcpStream> {
+        let udp = match addr.ip() {
+            IpAddr::V4(..) => UdpSocket::bind("0.0.0.0:0").await?,
+            IpAddr::V6(..) => UdpSocket::bind("[::]:0").await?,
+        };
+
+        let udp = Arc::new(udp);
+        let socket = KcpSocket::new(config, 0, udp, addr, config.stream)?;
+
+        let session = KcpSession::new_shared(socket, config.session_expire, None);
+
+        Ok(KcpStream::with_session(session))
+    }
+
+    pub(crate) fn with_session(session: Arc<KcpSession>) -> KcpStream {
+        KcpStream {
+            session,
+            recv_buffer: Vec::new(),
+            recv_buffer_pos: 0,
+            recv_buffer_cap: 0,
+        }
+    }
+
+    pub fn poll_send(&mut self, cx: &mut Context<'_>, buf: &[u8]) -> Poll<KcpResult<usize>> {
+        // Mutex doesn't have poll_lock, spinning on it.
+        let socket = self.session.kcp_socket();
+        let mut kcp = match socket.try_lock() {
+            Ok(guard) => guard,
+            Err(..) => {
+                cx.waker().wake_by_ref();
+                return Poll::Pending;
+            }
+        };
+
+        kcp.poll_send(cx, buf)
+    }
+
+    pub async fn send(&mut self, buf: &[u8]) -> KcpResult<usize> {
+        future::poll_fn(|cx| self.poll_send(cx, buf)).await
+    }
+
+    pub fn poll_recv(&mut self, cx: &mut Context<'_>, buf: &mut [u8]) -> Poll<KcpResult<usize>> {
+        loop {
+            // Consumes all data in buffer
+            if self.recv_buffer_pos < self.recv_buffer_cap {
+                let remaining = self.recv_buffer_cap - self.recv_buffer_pos;
+                let copy_length = remaining.min(buf.len());
+
+                buf.copy_from_slice(
+                    &self.recv_buffer[self.recv_buffer_pos..self.recv_buffer_pos + copy_length],
+                );
+                self.recv_buffer_pos += copy_length;
+                return Ok(copy_length).into();
+            }
+
+            // Mutex doesn't have poll_lock, spinning on it.
+            let socket = self.session.kcp_socket();
+            let mut kcp = match socket.try_lock() {
+                Ok(guard) => guard,
+                Err(..) => {
+                    cx.waker().wake_by_ref();
+                    return Poll::Pending;
+                }
+            };
+
+            // Try to read from KCP
+            // 1. Read directly with user provided `buf`
+            match ready!(kcp.poll_recv(cx, buf)) {
+                Ok(n) => {
+                    trace!("[CLIENT] recv directly {} bytes", n);
+                    return Ok(n).into();
+                }
+                Err(KcpError::UserBufTooSmall) => {}
+                Err(err) => return Err(err).into(),
+            }
+
+            // 2. User `buf` too small, read to recv_buffer
+            let required_size = kcp.peek_size()?;
+            if self.recv_buffer.len() < required_size {
+                self.recv_buffer.resize(required_size, 0);
+            }
+
+            match ready!(kcp.poll_recv(cx, &mut self.recv_buffer)) {
+                Ok(n) => {
+                    trace!("[CLIENT] recv buffered {} bytes", n);
+                    self.recv_buffer_pos = 0;
+                    self.recv_buffer_cap = n;
+                }
+                Err(err) => return Err(err).into(),
+            }
+        }
+    }
+
+    pub async fn recv(&mut self, buf: &mut [u8]) -> KcpResult<usize> {
+        future::poll_fn(|cx| self.poll_recv(cx, buf)).await
+    }
+}
+
+impl AsyncRead for KcpStream {
+    fn poll_read(
+        mut self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &mut ReadBuf<'_>,
+    ) -> Poll<io::Result<()>> {
+        match ready!(self.poll_recv(cx, buf.initialize_unfilled())) {
+            Ok(n) => {
+                buf.advance(n);
+                Ok(()).into()
+            }
+            Err(KcpError::IoError(err)) => Err(err).into(),
+            Err(err) => Err(io::Error::new(ErrorKind::Other, err)).into(),
+        }
+    }
+}
+
+impl AsyncWrite for KcpStream {
+    fn poll_write(
+        mut self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &[u8],
+    ) -> Poll<io::Result<usize>> {
+        match ready!(self.poll_send(cx, buf)) {
+            Ok(n) => Ok(n).into(),
+            Err(KcpError::IoError(err)) => Err(err).into(),
+            Err(err) => Err(io::Error::new(ErrorKind::Other, err)).into(),
+        }
+    }
+
+    fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+        // Mutex doesn't have poll_lock, spinning on it.
+        let socket = self.session.kcp_socket();
+        let mut kcp = match socket.try_lock() {
+            Ok(guard) => guard,
+            Err(..) => {
+                cx.waker().wake_by_ref();
+                return Poll::Pending;
+            }
+        };
+
+        match kcp.flush() {
+            Ok(..) => Ok(()).into(),
+            Err(KcpError::IoError(err)) => Err(err).into(),
+            Err(err) => Err(io::Error::new(ErrorKind::Other, err)).into(),
+        }
+    }
+
+    fn poll_shutdown(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+        Ok(()).into()
+    }
+}

src/plugins/kcp/utils.rs

@@ -0,0 +1,10 @@
+use std::time::{SystemTime, UNIX_EPOCH};
+
+#[inline]
+pub fn now_millis() -> u32 {
+    let start = SystemTime::now();
+    let since_the_epoch = start
+        .duration_since(UNIX_EPOCH)
+        .expect("time went afterwards");
+    (since_the_epoch.as_secs() * 1000 + since_the_epoch.subsec_millis() as u64 / 1_000_000) as u32
+}

src/plugins/mod.rs

@@ -0,0 +1 @@
+//pub mod kcp;

src/servers/mod.rs

@@ -1,41 +1,39 @@
-use futures::future::try_join;
-use log::{debug, error, info, warn};
+use log::{error, info};
 use std::collections::{HashMap, HashSet};
 use std::net::SocketAddr;
 use std::sync::Arc;
-use tokio::io;
-use tokio::io::{AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
-use tokio::net::{TcpListener, TcpStream};
 use tokio::task::JoinHandle;
 
-mod tls;
-use self::tls::get_sni;
-use crate::config::BaseConfig;
+mod protocol;
+pub(crate) mod upstream_address;
+
+use crate::config::{ParsedConfig, Upstream};
+use protocol::tcp;
 
 #[derive(Debug)]
-pub struct Server {
+pub(crate) struct Server {
     pub proxies: Vec<Arc<Proxy>>,
-    pub config: BaseConfig,
 }
 
 #[derive(Debug, Clone)]
-pub struct Proxy {
+pub(crate) struct Proxy {
     pub name: String,
     pub listen: SocketAddr,
+    pub protocol: String,
     pub tls: bool,
     pub sni: Option<HashMap<String, String>>,
-    pub default: String,
-    pub upstream: HashMap<String, String>,
+    pub default_action: String,
+    pub upstream: HashMap<String, Upstream>,
 }
 
 impl Server {
-    pub fn new(config: BaseConfig) -> Self {
+    pub fn new(config: ParsedConfig) -> Self {
         let mut new_server = Server {
             proxies: Vec::new(),
-            config: config.clone(),
         };
 
         for (name, proxy) in config.servers.iter() {
+            let protocol = proxy.protocol.clone().unwrap_or_else(|| "tcp".to_string());
             let tls = proxy.tls.unwrap_or(false);
             let sni = proxy.sni.clone();
             let default = proxy.default.clone().unwrap_or_else(|| "ban".to_string());
@@ -48,7 +46,6 @@ impl Server {
                 upstream_set.insert(key.clone());
             }
             for listen in proxy.listen.clone() {
-                println!("{:?}", listen);
                 let listen_addr: SocketAddr = match listen.parse() {
                     Ok(addr) => addr,
                     Err(_) => {
@@ -56,12 +53,14 @@ impl Server {
                         continue;
                     }
                 };
+
                 let proxy = Proxy {
                     name: name.clone(),
                     listen: listen_addr,
+                    protocol: protocol.clone(),
                     tls,
                     sni: sni.clone(),
-                    default: default.clone(),
+                    default_action: default.clone(),
                     upstream: upstream.clone(),
                 };
                 new_server.proxies.push(Arc::new(proxy));
@@ -77,9 +76,40 @@ impl Server {
         let mut handles: Vec<JoinHandle<()>> = Vec::new();
 
         for config in proxies {
-            info!("Starting server {} on {}", config.name, config.listen);
+            info!(
+                "Starting {} server {} on {}",
+                config.protocol, config.name, config.listen
+            );
             let handle = tokio::spawn(async move {
-                let _ = proxy(config).await;
+                match config.protocol.as_ref() {
+                    "tcp" => {
+                        let res = tcp::proxy(config.clone()).await;
+                        if res.is_err() {
+                            error!("Failed to start {}: {}", config.name, res.err().unwrap());
+                        }
+                    }
+                    "tcp4" => {
+                        let res = tcp::proxy(config.clone()).await;
+                        if res.is_err() {
+                            error!("Failed to start {}: {}", config.name, res.err().unwrap());
+                        }
+                    }
+                    "tcp6" => {
+                        let res = tcp::proxy(config.clone()).await;
+                        if res.is_err() {
+                            error!("Failed to start {}: {}", config.name, res.err().unwrap());
+                        }
+                    }
+                    // "kcp" => {
+                    //     let res = kcp::proxy(config.clone()).await;
+                    //     if res.is_err() {
+                    //         error!("Failed to start {}: {}", config.name, res.err().unwrap());
+                    //     }
+                    // }
+                    _ => {
+                        error!("Invalid protocol: {}", config.protocol)
+                    }
+                }
             });
             handles.push(handle);
         }
@@ -91,145 +121,92 @@ impl Server {
     }
 }
 
-async fn proxy(config: Arc<Proxy>) -> Result<(), Box<dyn std::error::Error>> {
-    let listener = TcpListener::bind(config.listen).await?;
-    let config = config.clone();
-
-    loop {
-        let thread_proxy = config.clone();
-        match listener.accept().await {
-            Err(err) => {
-                error!("Failed to accept connection: {}", err);
-                return Err(Box::new(err));
-            }
-            Ok((stream, _)) => {
-                tokio::spawn(async move {
-                    match accept(stream, thread_proxy).await {
-                        Ok(_) => {}
-                        Err(err) => {
-                            error!("Relay thread returned an error: {}", err);
-                        }
-                    };
-                });
-            }
-        }
-    }
-}
-
-async fn accept(inbound: TcpStream, proxy: Arc<Proxy>) -> Result<(), Box<dyn std::error::Error>> {
-    debug!("New connection from {:?}", inbound.peer_addr()?);
-
-    let upstream_name = match proxy.tls {
-        false => proxy.default.clone(),
-        true => {
-            let mut hello_buf = [0u8; 1024];
-            inbound.peek(&mut hello_buf).await?;
-            let snis = get_sni(&hello_buf);
-            if snis.is_empty() {
-                proxy.default.clone()
-            } else {
-                match proxy.sni.clone() {
-                    Some(sni_map) => {
-                        let mut upstream = proxy.default.clone();
-                        for sni in snis {
-                            let m = sni_map.get(&sni);
-                            if m.is_some() {
-                                upstream = m.unwrap().clone();
-                                break;
-                            }
-                        }
-                        upstream
-                    }
-                    None => proxy.default.clone(),
-                }
-            }
-        }
-    };
-
-    debug!("Upstream: {}", upstream_name);
-
-    let upstream = match proxy.upstream.get(&upstream_name) {
-        Some(upstream) => upstream,
-        None => {
-            warn!(
-                "No upstream named {:?} on server {:?}",
-                proxy.default, proxy.name
-            );
-            return process(inbound, &proxy.default).await;
-        }
-    };
-    return process(inbound, upstream).await;
-}
-
-async fn process(mut inbound: TcpStream, upstream: &str) -> Result<(), Box<dyn std::error::Error>> {
-    if upstream == "ban" {
-        let _ = inbound.shutdown();
-        return Ok(());
-    } else if upstream == "echo" {
-        loop {
-            let mut buf = [0u8; 1];
-            let b = inbound.read(&mut buf).await?;
-            if b == 0 {
-                break;
-            } else {
-                inbound.write(&buf).await?;
-            }
-        }
-        return Ok(());
-    }
-
-    let outbound = TcpStream::connect(upstream).await?;
-
-    let (mut ri, mut wi) = io::split(inbound);
-    let (mut ro, mut wo) = io::split(outbound);
-
-    let inbound_to_outbound = copy(&mut ri, &mut wo);
-    let outbound_to_inbound = copy(&mut ro, &mut wi);
-
-    let (bytes_tx, bytes_rx) = try_join(inbound_to_outbound, outbound_to_inbound).await?;
-
-    debug!("Bytes read: {:?} write: {:?}", bytes_tx, bytes_rx);
-
-    Ok(())
-}
-
-async fn copy<'a, R, W>(reader: &'a mut R, writer: &'a mut W) -> io::Result<u64>
-where
-    R: AsyncRead + Unpin + ?Sized,
-    W: AsyncWrite + Unpin + ?Sized,
-{
-    match io::copy(reader, writer).await {
-        Ok(u64) => {
-            let _ = writer.shutdown().await;
-            Ok(u64)
-        }
-        Err(_) => Ok(0),
-    }
-}
-
 #[cfg(test)]
-mod test {
+mod tests {
+    //use crate::plugins::kcp::{KcpConfig, KcpStream};
     use std::thread::{self, sleep};
     use std::time::Duration;
+    use tokio::io::{AsyncReadExt, AsyncWriteExt};
+    use tokio::net::TcpListener;
 
     use super::*;
 
+    #[tokio::main]
+    async fn tcp_mock_server() {
+        let server_addr: SocketAddr = "127.0.0.1:54599".parse().unwrap();
+        let listener = TcpListener::bind(server_addr).await.unwrap();
+        loop {
+            let (mut stream, _) = listener.accept().await.unwrap();
+            let mut buf = [0u8; 2];
+            let mut n = stream.read(&mut buf).await.unwrap();
+            while n > 0 {
+                stream.write(b"hello").await.unwrap();
+                if buf.eq(b"by") {
+                    stream.shutdown().await.unwrap();
+                    break;
+                }
+                n = stream.read(&mut buf).await.unwrap();
+            }
+            stream.shutdown().await.unwrap();
+        }
+    }
+
     #[tokio::test]
-    async fn test_echo_server() {
+    async fn test_proxy() {
         use crate::config::Config;
         let config = Config::new("tests/config.yaml").unwrap();
         let mut server = Server::new(config.base);
+        thread::spawn(move || {
+            tcp_mock_server();
+        });
+        sleep(Duration::from_secs(1)); // wait for server to start
         thread::spawn(move || {
             let _ = server.run();
         });
         sleep(Duration::from_secs(1)); // wait for server to start
-        let mut conn = TcpStream::connect("127.0.0.1:54956").await.unwrap();
+
+        // test TCP proxy
+        let mut conn = tokio::net::TcpStream::connect("127.0.0.1:54500")
+            .await
+            .unwrap();
+        let mut buf = [0u8; 5];
+        conn.write(b"hi").await.unwrap();
+        conn.read(&mut buf).await.unwrap();
+        assert_eq!(&buf, b"hello");
+        conn.shutdown().await.unwrap();
+
+        // test TCP echo
+        let mut conn = tokio::net::TcpStream::connect("127.0.0.1:54956")
+            .await
+            .unwrap();
         let mut buf = [0u8; 1];
-        for i in 0..=255u8 {
+        for i in 0..=10u8 {
             conn.write(&[i]).await.unwrap();
             conn.read(&mut buf).await.unwrap();
             assert_eq!(&buf, &[i]);
         }
         conn.shutdown().await.unwrap();
+
+        // test KCP echo
+        // let kcp_config = KcpConfig::default();
+        // let server_addr: SocketAddr = "127.0.0.1:54959".parse().unwrap();
+        // let mut conn = KcpStream::connect(&kcp_config, server_addr).await.unwrap();
+        // let mut buf = [0u8; 1];
+        // for i in 0..=10u8 {
+        //     conn.write(&[i]).await.unwrap();
+        //     conn.read(&mut buf).await.unwrap();
+        //     assert_eq!(&buf, &[i]);
+        // }
+        // conn.shutdown().await.unwrap();
+        //
+        // // test KCP proxy and close mock server
+        // let kcp_config = KcpConfig::default();
+        // let server_addr: SocketAddr = "127.0.0.1:54958".parse().unwrap();
+        // let mut conn = KcpStream::connect(&kcp_config, server_addr).await.unwrap();
+        // let mut buf = [0u8; 5];
+        // conn.write(b"by").await.unwrap();
+        // conn.read(&mut buf).await.unwrap();
+        // assert_eq!(&buf, b"hello");
+        // conn.shutdown().await.unwrap();
     }
 }

src/servers/protocol/kcp.rs

@@ -0,0 +1,112 @@
+use crate::config::Upstream;
+use crate::plugins::kcp::{KcpConfig, KcpListener, KcpStream};
+use crate::servers::Proxy;
+use futures::future::try_join;
+use log::{debug, error, warn};
+use std::net::SocketAddr;
+use std::sync::Arc;
+use tokio::io;
+use tokio::io::{AsyncRead, AsyncWrite, AsyncWriteExt};
+use tokio::net::TcpStream;
+
+pub async fn proxy(config: Arc<Proxy>) -> Result<(), Box<dyn std::error::Error>> {
+    let kcp_config = KcpConfig::default();
+    let mut listener = KcpListener::bind(kcp_config, config.listen).await?;
+    let config = config.clone();
+
+    loop {
+        let thread_proxy = config.clone();
+        match listener.accept().await {
+            Err(err) => {
+                error!("Failed to accept connection: {}", err);
+                return Err(Box::new(err));
+            }
+            Ok((stream, peer)) => {
+                tokio::spawn(async move {
+                    match accept(stream, peer, thread_proxy).await {
+                        Ok(_) => {}
+                        Err(err) => {
+                            error!("Relay thread returned an error: {}", err);
+                        }
+                    };
+                });
+            }
+        }
+    }
+}
+
+async fn accept(
+    inbound: KcpStream,
+    peer: SocketAddr,
+    proxy: Arc<Proxy>,
+) -> Result<(), Box<dyn std::error::Error>> {
+    debug!("New connection from {:?}", peer);
+
+    let upstream_name = proxy.default.clone();
+
+    debug!("Upstream: {}", upstream_name);
+
+    let upstream = match proxy.upstream.get(&upstream_name) {
+        Some(upstream) => upstream,
+        None => {
+            warn!(
+                "No upstream named {:?} on server {:?}",
+                proxy.default, proxy.name
+            );
+            return process(inbound, proxy.upstream.get(&proxy.default).unwrap()).await;
+            // ToDo: Remove unwrap and check default option
+        }
+    };
+    return process(inbound, upstream).await;
+}
+
+async fn process(
+    mut inbound: KcpStream,
+    upstream: &Upstream,
+) -> Result<(), Box<dyn std::error::Error>> {
+    match upstream {
+        Upstream::Ban => {
+            let _ = inbound.shutdown();
+        }
+        Upstream::Echo => {
+            let (mut ri, mut wi) = io::split(inbound);
+            let inbound_to_inbound = copy(&mut ri, &mut wi);
+            let bytes_tx = inbound_to_inbound.await;
+            debug!("Bytes read: {:?}", bytes_tx);
+        }
+        Upstream::Custom(custom) => match custom.protocol.as_ref() {
+            "tcp" => {
+                let outbound = TcpStream::connect(custom.addr.clone()).await?;
+
+                let (mut ri, mut wi) = io::split(inbound);
+                let (mut ro, mut wo) = io::split(outbound);
+
+                let inbound_to_outbound = copy(&mut ri, &mut wo);
+                let outbound_to_inbound = copy(&mut ro, &mut wi);
+
+                let (bytes_tx, bytes_rx) =
+                    try_join(inbound_to_outbound, outbound_to_inbound).await?;
+
+                debug!("Bytes read: {:?} write: {:?}", bytes_tx, bytes_rx);
+            }
+            _ => {
+                error!("Reached unknown protocol: {:?}", custom.protocol);
+            }
+        },
+    };
+    Ok(())
+}
+
+async fn copy<'a, R, W>(reader: &'a mut R, writer: &'a mut W) -> io::Result<u64>
+where
+    R: AsyncRead + Unpin + ?Sized,
+    W: AsyncWrite + Unpin + ?Sized,
+{
+    match io::copy(reader, writer).await {
+        Ok(u64) => {
+            let _ = writer.shutdown().await;
+            Ok(u64)
+        }
+        Err(_) => Ok(0),
+    }
+}

src/servers/protocol/mod.rs

@@ -0,0 +1,3 @@
+//pub mod kcp;
+pub mod tcp;
+pub mod tls;

src/servers/protocol/tcp.rs

@@ -0,0 +1,136 @@
+use crate::config::Upstream;
+use crate::servers::protocol::tls::get_sni;
+use crate::servers::Proxy;
+use futures::future::try_join;
+use log::{debug, error, info, warn};
+use std::sync::Arc;
+use tokio::io;
+use tokio::io::{AsyncRead, AsyncWrite, AsyncWriteExt};
+use tokio::net::{TcpListener, TcpStream};
+
+pub(crate) async fn proxy(config: Arc<Proxy>) -> Result<(), Box<dyn std::error::Error>> {
+    let listener = TcpListener::bind(config.listen).await?;
+    let config = config.clone();
+
+    loop {
+        let thread_proxy = config.clone();
+        match listener.accept().await {
+            Err(err) => {
+                error!("Failed to accept connection: {}", err);
+                return Err(Box::new(err));
+            }
+            Ok((stream, _)) => {
+                tokio::spawn(async move {
+                    match accept(stream, thread_proxy).await {
+                        Ok(_) => {}
+                        Err(err) => {
+                            error!("Relay thread returned an error: {}", err);
+                        }
+                    };
+                });
+            }
+        }
+    }
+}
+
+async fn accept(inbound: TcpStream, proxy: Arc<Proxy>) -> Result<(), Box<dyn std::error::Error>> {
+    info!("New connection from {:?}", inbound.peer_addr()?);
+
+    let upstream_name = match proxy.tls {
+        false => proxy.default_action.clone(),
+        true => {
+            let mut hello_buf = [0u8; 1024];
+            inbound.peek(&mut hello_buf).await?;
+            let snis = get_sni(&hello_buf);
+            if snis.is_empty() {
+                proxy.default_action.clone()
+            } else {
+                match proxy.sni.clone() {
+                    Some(sni_map) => {
+                        let mut upstream = proxy.default_action.clone();
+                        for sni in snis {
+                            let m = sni_map.get(&sni);
+                            if m.is_some() {
+                                upstream = m.unwrap().clone();
+                                break;
+                            }
+                        }
+                        upstream
+                    }
+                    None => proxy.default_action.clone(),
+                }
+            }
+        }
+    };
+
+    debug!("Upstream: {}", upstream_name);
+
+    let upstream = match proxy.upstream.get(&upstream_name) {
+        Some(upstream) => upstream,
+        None => {
+            warn!(
+                "No upstream named {:?} on server {:?}",
+                proxy.default_action, proxy.name
+            );
+            return process(inbound, proxy.upstream.get(&proxy.default_action).unwrap()).await;
+            // ToDo: Remove unwrap and check default option
+        }
+    };
+
+    return process(inbound, &upstream).await;
+}
+
+async fn process(
+    mut inbound: TcpStream,
+    upstream: &Upstream,
+) -> Result<(), Box<dyn std::error::Error>> {
+    match upstream {
+        Upstream::Ban => {
+            let _ = inbound.shutdown();
+        }
+        Upstream::Echo => {
+            let (mut ri, mut wi) = io::split(inbound);
+            let inbound_to_inbound = copy(&mut ri, &mut wi);
+            let bytes_tx = inbound_to_inbound.await;
+            debug!("Bytes read: {:?}", bytes_tx);
+        }
+        Upstream::Custom(custom) => {
+            let outbound = match custom.protocol.as_ref() {
+                "tcp4" | "tcp6" | "tcp" => {
+                    TcpStream::connect(custom.resolve_addresses().await?.as_slice()).await?
+                }
+                _ => {
+                    error!("Reached unknown protocol: {:?}", custom.protocol);
+                    return Err("Reached unknown protocol".into());
+                }
+            };
+
+            debug!("Connected to {:?}", outbound.peer_addr().unwrap());
+
+            let (mut ri, mut wi) = io::split(inbound);
+            let (mut ro, mut wo) = io::split(outbound);
+
+            let inbound_to_outbound = copy(&mut ri, &mut wo);
+            let outbound_to_inbound = copy(&mut ro, &mut wi);
+
+            let (bytes_tx, bytes_rx) = try_join(inbound_to_outbound, outbound_to_inbound).await?;
+
+            debug!("Bytes read: {:?} write: {:?}", bytes_tx, bytes_rx);
+        }
+    };
+    Ok(())
+}
+
+async fn copy<'a, R, W>(reader: &'a mut R, writer: &'a mut W) -> io::Result<u64>
+where
+    R: AsyncRead + Unpin + ?Sized,
+    W: AsyncWrite + Unpin + ?Sized,
+{
+    match io::copy(reader, writer).await {
+        Ok(u64) => {
+            let _ = writer.shutdown().await;
+            Ok(u64)
+        }
+        Err(_) => Ok(0),
+    }
+}

src/servers/protocol/tls.rs

@@ -49,6 +49,7 @@ pub fn get_sni(buf: &[u8]) -> Vec<String> {
         }
     }
 
+    debug!("Found SNIs: {:?}", &snis);
     snis
 }
 

src/servers/upstream_address.rs

@@ -0,0 +1,141 @@
+use log::debug;
+use std::fmt::{Display, Formatter};
+use std::io::Result;
+use std::net::SocketAddr;
+use time::{Duration, Instant, OffsetDateTime};
+
+#[derive(Debug, Clone, Default)]
+pub(crate) struct UpstreamAddress {
+    address: String,
+    resolved_addresses: Vec<SocketAddr>,
+    resolved_time: Option<Instant>,
+    ttl: Option<Duration>,
+}
+
+impl Display for UpstreamAddress {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        self.address.fmt(f)
+    }
+}
+
+impl UpstreamAddress {
+    pub fn new(address: String) -> Self {
+        UpstreamAddress {
+            address,
+            ..Default::default()
+        }
+    }
+
+    pub fn is_valid(&self) -> bool {
+        if let Some(resolved) = self.resolved_time {
+            if let Some(ttl) = self.ttl {
+                return resolved.elapsed() < ttl;
+            }
+        }
+
+        false
+    }
+
+    fn is_resolved(&self) -> bool {
+        self.resolved_addresses.len() > 0
+    }
+
+    fn time_remaining(&self) -> Duration {
+        if !self.is_valid() {
+            return Duration::seconds(0);
+        }
+
+        self.ttl.unwrap() - self.resolved_time.unwrap().elapsed()
+    }
+
+    pub async fn resolve(&mut self, mode: ResolutionMode) -> Result<Vec<SocketAddr>> {
+        if self.is_resolved() && self.is_valid() {
+            debug!(
+                "Already got address {:?}, still valid for {:.3}s",
+                &self.resolved_addresses,
+                self.time_remaining().as_seconds_f64()
+            );
+            return Ok(self.resolved_addresses.clone());
+        }
+
+        debug!(
+            "Resolving addresses for {} with mode {:?}",
+            &self.address, &mode
+        );
+
+        let lookup_result = tokio::net::lookup_host(&self.address).await;
+
+        let resolved_addresses: Vec<SocketAddr> = match lookup_result {
+            Ok(resolved_addresses) => resolved_addresses.into_iter().collect(),
+            Err(e) => {
+                debug!("Failed looking up {}: {}", &self.address, &e);
+                // Protect against DNS flooding. Cache the result for 1 second.
+                self.resolved_time = Some(Instant::now());
+                self.ttl = Some(Duration::seconds(3));
+                return Err(e);
+            }
+        };
+
+        debug!("Resolved addresses: {:?}", &resolved_addresses);
+
+        let addresses: Vec<SocketAddr> = match mode {
+            ResolutionMode::Ipv4 => resolved_addresses
+                .into_iter()
+                .filter(|a| a.is_ipv4())
+                .collect(),
+
+            ResolutionMode::Ipv6 => resolved_addresses
+                .into_iter()
+                .filter(|a| a.is_ipv6())
+                .collect(),
+
+            _ => resolved_addresses,
+        };
+
+        debug!(
+            "Got {} addresses for {}: {:?}",
+            &mode, &self.address, &addresses
+        );
+        debug!(
+            "Resolved at {}",
+            OffsetDateTime::now_utc()
+                .format(&time::format_description::well_known::Rfc3339)
+                .expect("Format")
+        );
+
+        self.resolved_addresses = addresses;
+        self.resolved_time = Some(Instant::now());
+        self.ttl = Some(Duration::minutes(1));
+
+        Ok(self.resolved_addresses.clone())
+    }
+}
+
+#[derive(Debug, Default, Clone)]
+pub(crate) enum ResolutionMode {
+    #[default]
+    Ipv4AndIpv6,
+    Ipv4,
+    Ipv6,
+}
+
+impl From<&str> for ResolutionMode {
+    fn from(value: &str) -> Self {
+        match value {
+            "tcp4" => ResolutionMode::Ipv4,
+            "tcp6" => ResolutionMode::Ipv6,
+            "tcp" => ResolutionMode::Ipv4AndIpv6,
+            _ => panic!("This should never happen. Please check configuration parser."),
+        }
+    }
+}
+
+impl Display for ResolutionMode {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        match self {
+            ResolutionMode::Ipv4 => write!(f, "IPv4Only"),
+            ResolutionMode::Ipv6 => write!(f, "IPv6Only"),
+            ResolutionMode::Ipv4AndIpv6 => write!(f, "IPv4 and IPv6"),
+        }
+    }
+}

tests/config.yaml

@@ -11,11 +11,26 @@ servers:
       proxy.test.com: proxy
       www.test.com: web
     default: ban
-  echo_server:
+  tcp_server:
+    listen:
+      - "127.0.0.1:54500"
+    default: tester
+  tcp_echo_server:
     listen:
       - "0.0.0.0:54956"
     default: echo
+  kcp_server:
+    protocol: kcp
+    listen:
+      - "127.0.0.1:54958"
+    default: tester
+  kcp_echo_server:
+    protocol: kcp
+    listen:
+      - "127.0.0.1:54959"
+    default: echo
 
 upstream:
-  web: "127.0.0.1:8080"
-  proxy: "www.example.com:1024"
+  web: "tcp://127.0.0.1:8080"
+  proxy: "tcp://www.example.com:1024"
+  tester: "tcp://127.0.0.1:54599"