如何基于 Kestrel 实现 socks5 代理

颐港 · 5 天前

前言

之前做了个轮子NZOrz, 本来打算慢慢参照Kestrel和Yarp长久地写着玩
奈何川普上台，关税，订婚案，自身和钱包等等各种乐子层出不穷，无暇慢悠悠地写轮子玩
还有有些盆友也想知道能否直接使用 Kestrel 来实现L4的处理，
所以为了2025年轻松一些，重新基于 Kestrel 实现了 L4/L7的代理 VKProxy (有兴趣的同学点个赞呗)，并简单实现 socks5 为大家展示一下
（PS：叠甲本人认知和能力有限，永远搞不懂/也不知道什么Txxxrojan/Sxxxhadowsocks等等这些东西，所以请不要咨询本人，本人不会不懂）
如何释放 Kestrel 的能力

众所周知 Kestrel 是 Aspnetcore 为了跨平台而实现的web server，只提供 http 1/2/3 的 L7层的能力
但看过源码的同学都知道，其实其本身从L4层(socket)实现的Http协议处理，只是OnBind只有http相关实现以及没有提供相关公开扩展的api，所以限制了其能力
但是既然代码是开源的，并且我们也知道dotnet有虽然麻烦但是能跨越访问限制的能力（Reflection），所以它是不能阻挡我们的魔爪
（ps
1. 不过这样绕过限制可能会在Native AOT相关场景存在问题，目前暂时没有做具体相关测试
2. 在不同版本Kestrel 可能会存在api变动，目前为了省事，不适配各版本差异，暂时以net9.0为准，net10正式发布后迁移升级到net10，此后不再适配net9.0之前版本
）
示例

首先我们先来看完成效果监听并处理 tcp/udp/http1/http2/http3，以便大家能理解我们的目的
VKProxy.Core 单纯封装释放Kestrel的能力以及简单的udp处理能力，所以大家单纯想使用 Kestrel处理相关内容就可以只使用VKProxy.Core
安装

dotnet add package VKProxy.Core --version 0.0.0.1

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程序入口

using CoreDemo;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using VKProxy.Core.Hosting;
var app = Host.CreateDefaultBuilder(args).UseVKProxyCore()
.ConfigureServices(i =>
{
// 已通过 IListenHandler 解耦监听和处理，大家可以实现其而做任意自己想做的事情
i.AddSingleton<IListenHandler, TcpListenHandler>();
i.AddSingleton<IListenHandler, UdpListenHandler>();
i.AddSingleton<IListenHandler, HttpListenHandler>();
})
.Build();
await app.RunAsync();

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如何处理 tcp

internal class TcpListenHandler : ListenHandlerBase
{
private readonly List<EndPointOptions> endPointOptions = new List<EndPointOptions>();
private readonly ILogger<TcpListenHandler> logger;
private readonly IConnectionFactory connectionFactory;
public TcpListenHandler(ILogger<TcpListenHandler> logger, IConnectionFactory connectionFactory)
{
this.logger = logger;
this.connectionFactory = connectionFactory;
}
/// 程序初次启动时，可以在此实现相关的初始化操作
public override Task InitAsync(CancellationToken cancellationToken)
{
endPointOptions.Add(new EndPointOptions()
{
EndPoint = IPEndPoint.Parse("127.0.0.1:5000"),
Key = "tcpXXX"
});
return Task.CompletedTask;
}
/// 可在此方法通过 transportManager.BindAsync 实现监听哪些端口以及如何处理，如果需要运行时监听端口变动等，可通过 GetReloadToken 和 RebindAsync 实现，这里为了简单不再举例
public override async Task BindAsync(ITransportManager transportManager, CancellationToken cancellationToken)
{
foreach (var item in endPointOptions)
{
try
{
await transportManager.BindAsync(item, Proxy, cancellationToken);
logger.LogInformation($"listen {item.EndPoint}");
}
catch (Exception ex)
{
logger.LogError(ex.Message, ex);
}
}
}
/// 处理的委托方法，这里的例子为简单的 tcp 代理
private async Task Proxy(ConnectionContext connection)
{
logger.LogInformation($"begin tcp {DateTime.Now} {connection.LocalEndPoint.ToString()} ");
var upstream = await connectionFactory.ConnectAsync(new IPEndPoint(IPAddress.Parse("14.215.177.38"), 80));
var task1 = connection.Transport.Input.CopyToAsync(upstream.Transport.Output);
var task2 = upstream.Transport.Input.CopyToAsync(connection.Transport.Output);
await Task.WhenAny(task1, task2);
upstream.Abort();
connection.Abort();
logger.LogInformation($"end tcp {DateTime.Now} {connection.LocalEndPoint.ToString()} ");
}
}

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如何处理 udp

默认已提供简单的udp 处理，所以无需大家自己实现监听循环，当然由于实现过于简单，复杂场景可能需要大家自己实现 IConnectionListenerFactory 或者 IMultiplexedConnectionListenerFactory

internal class UdpListenHandler : ListenHandlerBase
{
private readonly ILogger<UdpListenHandler> logger;
private readonly IUdpConnectionFactory udp;
private readonly IPEndPoint proxyServer = new(IPAddress.Parse("127.0.0.1"), 11000);
public UdpListenHandler(ILogger<UdpListenHandler> logger, IUdpConnectionFactory udp)
{
this.logger = logger;
this.udp = udp;
}
public override async Task BindAsync(ITransportManager transportManager, CancellationToken cancellationToken)
{
var ip = new EndPointOptions()
{
EndPoint = UdpEndPoint.Parse("127.0.0.1:5000"), // 为了区别 Kestrel 默认的tcp实现，所以必须通过 UdpEndPoint 屏蔽默认的tcp监听
Key = "udpXXX"
};
await transportManager.BindAsync(ip, Proxy, cancellationToken);
logger.LogInformation($"listen {ip.EndPoint}");
}
/// 处理的委托方法，这里的例子为简单的 UDP 代理
private async Task Proxy(ConnectionContext connection)
{
if (connection is UdpConnectionContext context)
{
Console.WriteLine($"{context.LocalEndPoint} received {context.ReceivedBytesCount} from {context.RemoteEndPoint}");
var socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
await udp.SendToAsync(socket, proxyServer, context.ReceivedBytes, CancellationToken.None);
var r = await udp.ReceiveAsync(socket, CancellationToken.None);
await udp.SendToAsync(context.Socket, context.RemoteEndPoint, r.GetReceivedBytes(), CancellationToken.None);
}
}
}

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如何处理 http

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Server.Kestrel.Core;
using Microsoft.AspNetCore.Server.Kestrel.Https;
using Microsoft.Extensions.Logging;
using System.Net;
using VKProxy.Core.Adapters;
using VKProxy.Core.Config;
using VKProxy.Core.Hosting;
namespace CoreDemo;
public class HttpListenHandler : ListenHandlerBase
{
private readonly ILogger<HttpListenHandler> logger;
private readonly ICertificateLoader certificateLoader;
public HttpListenHandler(ILogger<HttpListenHandler> logger, ICertificateLoader certificateLoader)
{
this.logger = logger;
this.certificateLoader = certificateLoader;
}
private async Task Proxy(HttpContext context)
{
var resp = context.Response;
resp.StatusCode = 404;
await resp.WriteAsJsonAsync(new { context.Request.Protocol });
await resp.CompleteAsync().ConfigureAwait(false);
}
public override async Task BindAsync(ITransportManager transportManager, CancellationToken cancellationToken)
{
try
{
// http （http2和http3都需要证书，所以这里监听会忽略，只监听http1）
var ip = new EndPointOptions()
{
EndPoint = IPEndPoint.Parse("127.0.0.1:4000"),
Key = "http"
};
await transportManager.BindHttpAsync(ip, Proxy, cancellationToken);
logger.LogInformation($"listen {ip.EndPoint}");
// https
ip = new EndPointOptions()
{
EndPoint = IPEndPoint.Parse("127.0.0.1:4001"),
Key = "https"
};
var (c, f) = certificateLoader.LoadCertificate(new CertificateConfig() { Path = "testCert.pfx", Password = "testPassword" }); //读取证书
await transportManager.BindHttpAsync(ip, Proxy, cancellationToken, HttpProtocols.Http1AndHttp2AndHttp3, callbackOptions: new HttpsConnectionAdapterOptions()
{
//ServerCertificateSelector = (context, host) => c http3 由于底层 quic 实现，无法支持动态ServerCertificate
ServerCertificate = c,
CheckCertificateRevocation = false,
ClientCertificateMode = ClientCertificateMode.AllowCertificate
});
logger.LogInformation($"listen {ip.EndPoint}");
}
catch (Exception ex)
{
logger.LogError(ex.Message, ex);
}
}
}

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适配Kestrel 的核心点

核心重点在暴露TransportManager api，这样大家就有了L4层的处理能力
TransportManagerAdapter 实现

public class TransportManagerAdapter : ITransportManager, IHeartbeat
{
private static MethodInfo StopAsyncMethod;
private static MethodInfo StopEndpointsAsyncMethod;
private static MethodInfo MultiplexedBindAsyncMethod;
private static MethodInfo BindAsyncMethod;
private static MethodInfo StartHeartbeatMethod;
private object transportManager;
private object heartbeat;
private object serviceContext;
private object metrics;
private int multiplexedTransportCount;
private int transportCount;
internal readonly IServiceProvider serviceProvider;
IServiceProvider ITransportManager.ServiceProvider => serviceProvider;
public TransportManagerAdapter(IServiceProvider serviceProvider, IEnumerable<IConnectionListenerFactory> transportFactories, IEnumerable<IMultiplexedConnectionListenerFactory> multiplexedConnectionListenerFactories)
{
(transportManager, heartbeat, serviceContext, metrics) = CreateTransportManager(serviceProvider);
multiplexedTransportCount = multiplexedConnectionListenerFactories.Count();
transportCount = transportFactories.Count();
this.serviceProvider = serviceProvider;
}
private static (object, object, object, object) CreateTransportManager(IServiceProvider serviceProvider)
{
foreach (var item in KestrelExtensions.TransportManagerType.GetTypeInfo().DeclaredMethods)
{
if (item.Name == "StopAsync")
{
StopAsyncMethod = item;
}
else if (item.Name == "StopEndpointsAsync")
{
StopEndpointsAsyncMethod = item;
}
else if (item.Name == "BindAsync")
{
if (item.GetParameters().Any(i => i.ParameterType == typeof(ConnectionDelegate)))
{
BindAsyncMethod = item;
}
else
{
MultiplexedBindAsyncMethod = item;
}
}
}
var s = CreateServiceContext(serviceProvider);
var r = Activator.CreateInstance(KestrelExtensions.TransportManagerType,
Enumerable.Reverse(serviceProvider.GetServices<IConnectionListenerFactory>()).ToList(),
Enumerable.Reverse(serviceProvider.GetServices<IMultiplexedConnectionListenerFactory>()).ToList(),
CreateHttpsConfigurationService(serviceProvider),
s.context
);
return (r, s.heartbeat, s.context, s.metrics);
static object CreateHttpsConfigurationService(IServiceProvider serviceProvider)
{
var CreateLogger = typeof(LoggerFactoryExtensions).GetTypeInfo().DeclaredMethods.First(i => i.Name == "CreateLogger" && i.ContainsGenericParameters);
var r = Activator.CreateInstance(KestrelExtensions.HttpsConfigurationServiceType);
var m = KestrelExtensions.HttpsConfigurationServiceType.GetMethod("Initialize");
var log = serviceProvider.GetRequiredService<ILoggerFactory>();
var l = CreateLogger.MakeGenericMethod(KestrelExtensions.HttpsConnectionMiddlewareType).Invoke(null, new object[] { log });
m.Invoke(r, new object[] { serviceProvider.GetRequiredService<IHostEnvironment>(), log.CreateLogger<KestrelServer>(), l });
return r;
}
static (object context, object heartbeat, object metrics) CreateServiceContext(IServiceProvider serviceProvider)
{
var m = CreateKestrelMetrics();
var KestrelCreateServiceContext = KestrelExtensions.KestrelServerImplType.GetMethod("CreateServiceContext", System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.NonPublic);
var r = KestrelCreateServiceContext.Invoke(null, new object[]
{
serviceProvider.GetRequiredService<IOptions<KestrelServerOptions>>(),
serviceProvider.GetRequiredService<ILoggerFactory>(),
null,
m
});
var h = KestrelExtensions.ServiceContextType.GetTypeInfo().DeclaredProperties.First(i => i.Name == "Heartbeat");
StartHeartbeatMethod = KestrelExtensions.HeartbeatType.GetTypeInfo().DeclaredMethods.First(i => i.Name == "Start");
return (r, h.GetGetMethod().Invoke(r, null), m);
}
static object CreateKestrelMetrics()
{
return Activator.CreateInstance(KestrelExtensions.KestrelMetricsType, Activator.CreateInstance(KestrelExtensions.DummyMeterFactoryType));
}
}
public Task<EndPoint> BindAsync(EndPointOptions endpointConfig, ConnectionDelegate connectionDelegate, CancellationToken cancellationToken)
{
return BindAsyncMethod.Invoke(transportManager, new object[] { endpointConfig.EndPoint, connectionDelegate, endpointConfig.Init(), cancellationToken }) as Task<EndPoint>;
}
public Task<EndPoint> BindAsync(EndPointOptions endpointConfig, MultiplexedConnectionDelegate multiplexedConnectionDelegate, CancellationToken cancellationToken)
{
return MultiplexedBindAsyncMethod.Invoke(transportManager, new object[] { endpointConfig.EndPoint, multiplexedConnectionDelegate, endpointConfig.GetListenOptions(), cancellationToken }) as Task<EndPoint>;
}
public Task StopEndpointsAsync(List<EndPointOptions> endpointsToStop, CancellationToken cancellationToken)
{
return StopEndpointsAsyncMethod.Invoke(transportManager, new object[] { EndPointOptions.Init(endpointsToStop), cancellationToken }) as Task;
}
public Task StopAsync(CancellationToken cancellationToken)
{
return StopAsyncMethod.Invoke(transportManager, new object[] { cancellationToken }) as Task;
}
public void StartHeartbeat()
{
if (heartbeat != null)
{
StartHeartbeatMethod.Invoke(heartbeat, null);
}
}
public void StopHeartbeat()
{
if (heartbeat is IDisposable disposable)
{
disposable.Dispose();
}
}
public IConnectionBuilder UseHttpServer(IConnectionBuilder builder, IHttpApplication<HttpApplication.Context> application, HttpProtocols protocols, bool addAltSvcHeader)
{
KestrelExtensions.UseHttpServerMethod.Invoke(null, new object[] { builder, serviceContext, application, protocols, addAltSvcHeader });
return builder;
}
public IMultiplexedConnectionBuilder UseHttp3Server(IMultiplexedConnectionBuilder builder, IHttpApplication<HttpApplication.Context> application, HttpProtocols protocols, bool addAltSvcHeader)
{
KestrelExtensions.UseHttp3ServerMethod.Invoke(null, new object[] { builder, serviceContext, application, protocols, addAltSvcHeader });
return builder;
}
public ConnectionDelegate UseHttps(ConnectionDelegate next, HttpsConnectionAdapterOptions tlsCallbackOptions, HttpProtocols protocols)
{
if (tlsCallbackOptions == null)
return next;
var o = KestrelExtensions.HttpsConnectionMiddlewareInitMethod.Invoke(new object[] { next, tlsCallbackOptions, protocols, serviceProvider.GetRequiredService<ILoggerFactory>(), metrics });
return KestrelExtensions.HttpsConnectionMiddlewareOnConnectionAsyncMethod.CreateDelegate<ConnectionDelegate>(o);
}
public async Task BindHttpApplicationAsync(EndPointOptions options, IHttpApplication<HttpApplication.Context> application, CancellationToken cancellationToken, HttpProtocols protocols = HttpProtocols.Http1AndHttp2AndHttp3, bool addAltSvcHeader = true, Action<IConnectionBuilder> config = null
, Action<IMultiplexedConnectionBuilder> configMultiplexed = null, HttpsConnectionAdapterOptions callbackOptions = null)
{
var hasHttp1 = protocols.HasFlag(HttpProtocols.Http1);
var hasHttp2 = protocols.HasFlag(HttpProtocols.Http2);
var hasHttp3 = protocols.HasFlag(HttpProtocols.Http3);
var hasTls = callbackOptions is not null;
if (hasTls)
{
if (hasHttp3)
{
options.GetListenOptions().Protocols = protocols;
options.SetHttpsOptions(callbackOptions);
}
//callbackOptions.SetHttpProtocols(protocols);
//if (hasHttp3)
//{
// HttpsConnectionAdapterOptions
// options.SetHttpsCallbackOptions(callbackOptions);
//}
}
else
{
// Http/1 without TLS, no-op HTTP/2 and 3.
if (hasHttp1)
{
hasHttp2 = false;
hasHttp3 = false;
}
// Http/3 requires TLS. Note we only let it fall back to HTTP/1, not HTTP/2
else if (hasHttp3)
{
throw new InvalidOperationException("HTTP/3 requires HTTPS.");
}
}
// Quic isn't registered if it's not supported, throw if we can't fall back to 1 or 2
if (hasHttp3 && multiplexedTransportCount == 0 && !(hasHttp1 || hasHttp2))
{
throw new InvalidOperationException("Unable to bind an HTTP/3 endpoint. This could be because QUIC has not been configured using UseQuic, or the platform doesn't support QUIC or HTTP/3.");
}
addAltSvcHeader = addAltSvcHeader && multiplexedTransportCount > 0;
// Add the HTTP middleware as the terminal connection middleware
if (hasHttp1 || hasHttp2
|| protocols == HttpProtocols.None)
{
if (transportCount == 0)
{
throw new InvalidOperationException($"Cannot start HTTP/1.x or HTTP/2 server if no {nameof(IConnectionListenerFactory)} is registered.");
}
var builder = new ConnectionBuilder(serviceProvider);
config?.Invoke(builder);
UseHttpServer(builder, application, protocols, addAltSvcHeader);
var connectionDelegate = UseHttps(builder.Build(), callbackOptions, protocols);
options.EndPoint = await BindAsync(options, connectionDelegate, cancellationToken).ConfigureAwait(false);
}
if (hasHttp3 && multiplexedTransportCount > 0)
{
var builder = new MultiplexedConnectionBuilder(serviceProvider);
configMultiplexed?.Invoke(builder);
UseHttp3Server(builder, application, protocols, addAltSvcHeader);
var multiplexedConnectionDelegate = builder.Build();
options.EndPoint = await BindAsync(options, multiplexedConnectionDelegate, cancellationToken).ConfigureAwait(false);
}
}
}

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其次通过重写 VKServer 从而去除 OnBind 方法的影响，达到大家可以使用 ITransportManager 做任意 L4/L7的处理

public class VKServer : IServer
{
private readonly ITransportManager transportManager;
private readonly IHeartbeat heartbeat;
private readonly IListenHandler listenHandler;
private readonly GeneralLogger logger;
private bool _hasStarted;
private int _stopping;
private readonly SemaphoreSlim _bindSemaphore = new SemaphoreSlim(initialCount: 1);
private readonly CancellationTokenSource _stopCts = new CancellationTokenSource();
private readonly TaskCompletionSource _stoppedTcs = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
private IDisposable? _configChangedRegistration;
public VKServer(ITransportManager transportManager, IHeartbeat heartbeat, IListenHandler listenHandler, GeneralLogger logger)
{
this.transportManager = transportManager;
this.heartbeat = heartbeat;
this.listenHandler = listenHandler;
this.logger = logger;
}
public async Task StartAsync(CancellationToken cancellationToken)
{
try
{
if (_hasStarted)
{
throw new InvalidOperationException("Server already started");
}
_hasStarted = true;
await listenHandler.InitAsync(cancellationToken);
heartbeat.StartHeartbeat();
await BindAsync(cancellationToken).ConfigureAwait(false);
}
catch
{
Dispose();
throw;
}
}
private async Task BindAsync(CancellationToken cancellationToken)
{
await _bindSemaphore.WaitAsync(cancellationToken).ConfigureAwait(false);
try
{
if (_stopping == 1)
{
throw new InvalidOperationException("Server has already been stopped.");
}
IChangeToken? reloadToken = listenHandler.GetReloadToken();
await listenHandler.BindAsync(transportManager, _stopCts.Token).ConfigureAwait(false);
_configChangedRegistration = reloadToken?.RegisterChangeCallback(TriggerRebind, this);
}
finally
{
_bindSemaphore.Release();
}
}
private void TriggerRebind(object? state)
{
if (state is VKServer server)
{
_ = server.RebindAsync();
}
}
private async Task RebindAsync()
{
await _bindSemaphore.WaitAsync();
IChangeToken? reloadToken = null;
try
{
if (_stopping == 1)
{
return;
}
reloadToken = listenHandler.GetReloadToken();
await listenHandler.RebindAsync(transportManager, _stopCts.Token).ConfigureAwait(false);
}
catch (Exception ex)
{
logger.UnexpectedException("Unable to reload configuration", ex);
}
finally
{
_configChangedRegistration = reloadToken?.RegisterChangeCallback(TriggerRebind, this);
_bindSemaphore.Release();
}
}
public async Task StopAsync(CancellationToken cancellationToken)
{
if (Interlocked.Exchange(ref _stopping, 1) == 1)
{
await _stoppedTcs.Task.ConfigureAwait(false);
return;
}
heartbeat.StopHeartbeat();
_stopCts.Cancel();
await _bindSemaphore.WaitAsync().ConfigureAwait(false);
try
{
await listenHandler.StopAsync(transportManager, cancellationToken).ConfigureAwait(false);
await transportManager.StopAsync(cancellationToken).ConfigureAwait(false);
}
catch (Exception ex)
{
_stoppedTcs.TrySetException(ex);
throw;
}
finally
{
_configChangedRegistration?.Dispose();
_stopCts.Dispose();
_bindSemaphore.Release();
}
_stoppedTcs.TrySetResult();
}
public void Dispose()
{
StopAsync(new CancellationToken(canceled: true)).GetAwaiter().GetResult();
}
}

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如何实现 socks5

socks5 代理协议已经有很多文章说明，这里不再赘述，想了解的可以参见https://zh.wikipedia.org/wiki/SOCKS
这里列举一下核心实现

internal class Socks5Middleware : ITcpProxyMiddleware
{
private readonly IDictionary<byte, ISocks5Auth> auths;
private readonly IConnectionFactory tcp;
private readonly IHostResolver hostResolver;
private readonly ITransportManager transport;
private readonly IUdpConnectionFactory udp;
public Socks5Middleware(IEnumerable<ISocks5Auth> socks5Auths, IConnectionFactory tcp, IHostResolver hostResolver, ITransportManager transport, IUdpConnectionFactory udp)
{
this.auths = socks5Auths.ToFrozenDictionary(i => i.AuthType);
this.tcp = tcp;
this.hostResolver = hostResolver;
this.transport = transport;
this.udp = udp;
}
public Task InitAsync(ConnectionContext context, CancellationToken token, TcpDelegate next)
{
// 识别是否为 socks5 路由
var feature = context.Features.Get<IL4ReverseProxyFeature>();
if (feature is not null)
{
var route = feature.Route;
if (route is not null && route.Metadata is not null
&& route.Metadata.TryGetValue("socks5", out var b) && bool.TryParse(b, out var isSocks5) && isSocks5)
{
feature.IsDone = true;
return Proxy(context, feature, token);
}
}
return next(context, token);
}
public Task<ReadOnlyMemory<byte>> OnRequestAsync(ConnectionContext context, ReadOnlyMemory<byte> source, CancellationToken token, TcpProxyDelegate next)
{
return next(context, source, token);
}
public Task<ReadOnlyMemory<byte>> OnResponseAsync(ConnectionContext context, ReadOnlyMemory<byte> source, CancellationToken token, TcpProxyDelegate next)
{
return next(context, source, token);
}
private async Task Proxy(ConnectionContext context, IL4ReverseProxyFeature feature, CancellationToken token)
{
var input = context.Transport.Input;
var output = context.Transport.Output;
// 1. socks5 认证
if (!await Socks5Parser.AuthAsync(input, auths, context, token))
{
context.Abort();
}
// 2. 获取 socks5 命令请求
var cmd = await Socks5Parser.GetCmdRequestAsync(input, token);
IPEndPoint ip = await ResolveIpAsync(context, cmd, token);
switch (cmd.Cmd)
{
case Socks5Cmd.Connect:
case Socks5Cmd.Bind:
// 3. 如果为tcp代理，则会在此分支处理，以命令请求中的地址建立tcp链接
ConnectionContext upstream;
try
{
upstream = await tcp.ConnectAsync(ip, token);
}
catch
{ // 为了简单，这里异常没有详细分区各种情况
await Socks5Parser.ResponeAsync(output, Socks5CmdResponseType.ConnectFail, token);
throw;
}
// 4. 服务tcp建立成功，通知 client
await Socks5Parser.ResponeAsync(output, Socks5CmdResponseType.Success, token);
var task = await Task.WhenAny(
context.Transport.Input.CopyToAsync(upstream.Transport.Output, token)
, upstream.Transport.Input.CopyToAsync(context.Transport.Output, token));
if (task.IsCanceled)
{
context.Abort();
}
break;
case Socks5Cmd.UdpAssociate:
// 3. 如果为udp代理，则会在此分支处理，建立临时 udp 代理服务地址
var local = context.LocalEndPoint as IPEndPoint;
var op = new EndPointOptions()
{
EndPoint = new UdpEndPoint(local.Address, 0),
Key = Guid.NewGuid().ToString(),
};
try
{
var remote = context.RemoteEndPoint;
var timeout = feature.Route.Timeout;
op.EndPoint = await transport.BindAsync(op, c => ProxyUdp(c as UdpConnectionContext, remote, timeout), token);
// 5. tcp 关闭时需要关闭临时 udp 服务
context.ConnectionClosed.Register(state => transport.StopEndpointsAsync(new List<EndPointOptions>() { state as EndPointOptions }, CancellationToken.None).ConfigureAwait(false).GetAwaiter().GetResult(), op);
}
catch
{
await Socks5Parser.ResponeAsync(output, Socks5CmdResponseType.ConnectFail, token);
throw;
}
// 4. 服务udp建立成功，通知 client 临时udp地址
await Socks5Parser.ResponeAsync(output, op.EndPoint as IPEndPoint, Socks5CmdResponseType.Success, token);
break;
}
}
private async Task ProxyUdp(UdpConnectionContext context, EndPoint remote, TimeSpan timeout)
{
using var cts = CancellationTokenSourcePool.Default.Rent(timeout);
var token = cts.Token;
// 这里用为了简单同一个临时地址即监听client 也处理服务端 response，通过端口比较区分，当然这样存在一定安全问题
if (context.RemoteEndPoint.GetHashCode() == remote.GetHashCode())
{
var req = Socks5Parser.GetUdpRequest(context.ReceivedBytes);
IPEndPoint ip = await ResolveIpAsync(req, token);
// 请求服务，解包原始请求
await udp.SendToAsync(context.Socket, ip, req.Data, token);
}
else
{
// 服务response，封包
await Socks5Parser.UdpResponeAsync(udp, context, remote as IPEndPoint, token);
}
}
private async Task<IPEndPoint> ResolveIpAsync(ConnectionContext context, Socks5Common cmd, CancellationToken token)
{
IPEndPoint ip = await ResolveIpAsync(cmd, token);
if (ip is null)
{
await Socks5Parser.ResponeAsync(context.Transport.Output, Socks5CmdResponseType.AddressNotAllow, token);
context.Abort();
}
return ip;
}
private async Task<IPEndPoint> ResolveIpAsync(Socks5Common cmd, CancellationToken token)
{
IPEndPoint ip;
if (cmd.Domain is not null)
{
var ips = await hostResolver.HostResolveAsync(cmd.Domain, token);
if (ips.Length > 0)
{
ip = new IPEndPoint(ips.First(), cmd.Port);
}
else
ip = null;
}
else if (cmd.Ip is not null)
{
ip = new IPEndPoint(cmd.Ip, cmd.Port);
}
else
{
ip = null;
}
return ip;
}
}

复制代码

如此大家可以看到大家无需疯狂 while(true) { await socket.Receive... }, 减轻了很多大家负担

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