ASP.NET Core跨平台技术内幕( 二 ) _ASP.NET

ACM转发的请求，会携带名为MS-ASPNETCORE-TOKEN:******的Request Header,以便dotnet.exe对比研判。

③ 利用ForwardedHeaderMiddleware中间件保存原始请求信息

linux平台部署需要手动启用ForwardedHeader middleware https://docs.microsoft.com/en-us/aspnet/core/host-and-deploy/proxy-load-balancer?view=aspnetcore-3.1

源码快速验证：
namespace Microsoft.AspNetCore.Hosting{ public static class WebHostBuilderIISExtensions { // These are defined as ASPNETCORE_ environment variables by IIS's AspNetCoreModule. private static readonly string ServerPort = "PORT"; private static readonly string ServerPath = "APPL_PATH"; private static readonly string PairingToken = "TOKEN"; private static readonly string IISAuth = "IIS_HTTPAUTH"; private static readonly string IISWebSockets = "IIS_WEBSOCKETS_SUPPORTED"; /// <summary> /// Configures the port and base path the server should listen on when running behind AspNetCoreModule. /// The app will also be configured to capture startup errors. public static IWebHostBuilder UseIISIntegration(this IWebHostBuilder hostBuilder) { var port = hostBuilder.GetSetting(ServerPort) ?? Environment.GetEnvironmentVariable($"ASPNETCORE_{ServerPort}"); var path = hostBuilder.GetSetting(ServerPath) ?? Environment.GetEnvironmentVariable($"ASPNETCORE_{ServerPath}");

 var pairingToken = hostBuilder.GetSetting(PairingToken) ?? Environment.GetEnvironmentVariable($"ASPNETCORE_{PairingToken}");

var iisAuth = hostBuilder.GetSetting(IISAuth) ?? Environment.GetEnvironmentVariable($"ASPNETCORE_{IISAuth}");

 var websocketsSupported = hostBuilder.GetSetting(IISWebSockets) ?? Environment.GetEnvironmentVariable($"ASPNETCORE_{IISWebSockets}");

bool isWebSocketsSupported; if (!bool.TryParse(websocketsSupported, out isWebSocketsSupported)) { // If the websocket support variable is not set, we will always fallback to assuming websockets are enabled. isWebSocketsSupported = (Environment.OSVersion.Version >= new Version(6, 2)); } if (!string.IsOrEmpty(port) && !string.IsOrEmpty(path) && !string.IsOrEmpty(pairingToken)) { // Set flag to prevent double service configuration hostBuilder.UseSetting(nameof(UseIISIntegration), true.ToString); var enableAuth = false; if (string.IsOrEmpty(iisAuth)) { // back compat with older ANCM versions enableAuth = true; } else { // Lightup a new ANCM variable that tells us if auth is enabled. foreach (var authType in iisAuth.Split(new[] { ';' }, StringSplitOptions.RemoveEmptyEntries)) { if (!string.Equals(authType, "anonymous", StringComparison.OrdinalIgnoreCase)) { enableAuth = true; break; } } } var address = "http://127.0.0.1:" + port; hostBuilder.CaptureStartupErrors(true); hostBuilder.ConfigureServices(services => { // Delay register the url so users don't accidentally overwrite it. hostBuilder.UseSetting(WebHostDefaults.ServerUrlsKey, address); hostBuilder.PreferHostingUrls(true); services.AddSingleton<IServerIntegratedAuth>(_ => new ServerIntegratedAuth { IsEnabled = enableAuth, AuthenticationScheme = IISDefaults.AuthenticationScheme }); services.AddSingleton<IStartupFilter>(new IISSetupFilter(pairingToken, new PathString(path), isWebSocketsSupported)); services.Configure<ForwardedHeadersOptions>(options => { options.ForwardedHeaders = ForwardedHeaders.XForwardedFor | ForwardedHeaders.XForwardedProto; }); services.Configure<IISOptions>(options => { options.ForwardWindowsAuthentication = enableAuth; }); services.AddAuthenticationCore; }); } return hostBuilder; } }}总结
ASP.NET Core跨平台的核心在于程序内置Kestrel HTTP通信组件，解耦web服务器差异；依平台特性约定Http通信细节。
本文从框架设计初衷、进程模型、组件交互验证我对ASP.NET Core跨平台特性的理解。
+ CentOS上部署ASP.NET Core完整版请参考：https://