我今天遇到了一个坑,我的服务器在经过了 Nginx 之后,发送的 POST 请求,如果请求里面有 Body 内容,那么 Kestrel 将会返回 400 错误,同时也不会经过任何的中间件
在 HTTP 的标准里面,在 HTTP 协议提供了一种特殊的机制,这一机制允许将一个已建立的连接升级成新的、不相容的协议。由客户端发起给服务端询问可以服务器端选择是否要升级到新协议,这个机制可以做到如客户端使用HTTP/1.1去连接服务器端,询问服务器端是否能升级到HTTP2甚至是WebSockets协议。而这个机制的做法如 mozilla 协议升级机制 文档所说,在客户端请求的时候将会添加两个额外的 Header 内容:
Connection: Upgrade 设置 Connection 头的值为 “Upgrade” 来指示这是一个升级请求
Upgrade: protocols Upgrade 头指定一项或多项协议名,按优先级排序,以逗号分隔
一个典型的包含升级请求的例子差不多是这样的:
Upgrade: example/1, foo/2
而在我这边其实是为了让 Nginx 支持 WebSockets 协议,如 nginx 反向代理websocket – A Blog 所说方法,配置如下
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
可以看到这里的锅就是,无论是否有配置 Upgrade 的内容,都给 Connection 加上了 upgrade 的内容
咱可以来写一个简单的 demo 程序,尝试在 ASP.NET Core 应用发送一个 POST 请求,这个请求里面包含了这两个 Header 信息,如下面代码
var httpClient = new HttpClient ();
httpClient.DefaultRequestHeaders. Clear ();
httpClient.DefaultRequestHeaders. Add ( " Upgrade " , "" );
httpClient.DefaultRequestHeaders. Add ( " Connection " , " Upgrade " );
这个 demo 代码放在gitee 欢迎大家访问
这个 demo 里面,可以看到只有使用 UseExceptionHandler 的如下重载方法才会进入,而其他的重载方法进入失败
app. UseExceptionHandler ( builder =>
从输出的日志里面可以看到下面代码
dbug: Microsoft.AspNetCore.Server.Kestrel[39]
Connection id "0HM5U310J8F34" accepted.
dbug: Microsoft.AspNetCore.Server.Kestrel[1]
Connection id "0HM5U310J8F34" started.
dbug: Microsoft.AspNetCore.Server.Kestrel[17]
Connection id "0HM5U310J8F34" bad request data: "Requests with 'Connection: Upgrade' cannot have content in the request body."
Microsoft.AspNetCore.Server.Kestrel.Core.BadHttpRequestException: Requests with 'Connection: Upgrade' cannot have content in the request body.
at Microsoft.AspNetCore.Server.Kestrel.Core.BadHttpRequestException.Throw(RequestRejectionReason reason)
at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.Http1MessageBody.For(HttpVersion httpVersion, HttpRequestHeaders headers, Http1Connection context)
at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.Http1Connection.CreateMessageBody()
at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpProtocol.ProcessRequests[TContext](IHttpApplication`1 application)
at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpProtocol.ProcessRequestsAsync[TContext](IHttpApplication`1 application)
也就是说开启调试模式的日志,可以了解到输出了 Requests with 'Connection: Upgrade' cannot have content in the request body.
的内容。开启日志的方法就是在 appsettings.json 和 appsettings.Development.json 设置日志等级为 Debug 就可以
而这个问题,官方也有收到反馈,请看 “Connection: upgrade” causes 400 error that never reaches application code. Triggered by common nginx config. · Issue #17081 · dotnet/aspnetcore
虽然这样做是不符合规范的,但是用的人多了,也就约定俗成了。而 Kestrel 比较严格的遵守标准却在此时挖了一个坑。最近有一个 PR 是允许忽略掉加上 upgrade 在 POST 带上 Body 的逻辑合入到 dotnet core 2.1 和 dotnet core 3.1 和 dotnet 5.0 版本,也许在你看到这个博客的时候,咱的应用其实能做到默认支持的
而其实在官方文档里面也给出了推荐的 Nginx 的配置,如下,但是如下配置可是会给 websocket 挖坑的哦,详细请看 nginx 反向代理websocket – A Blog
server_name example.com *.example.com;
proxy_pass http://localhost:5000;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection keep-alive;
proxy_set_header Host $host;
proxy_cache_bypass $http_upgrade;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto $scheme;
可以看到在官方的配置里面给 Connection 配置的是 keep-alive 哈,但如果需要支持 websocket 如 signalr 技术,此时的配置如下
map $http_connection $connection_upgrade {
"~*Upgrade" $http_connection;
server_name example.com *.example.com;
# Configure the SignalR Endpoint
proxy_pass http://localhost:5000;
# Configuration for WebSockets
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection $connection_upgrade;
# Configuration for ServerSentEvents
# Configuration for LongPolling or if your KeepAliveInterval is longer than 60 seconds
proxy_set_header Host $host;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto $scheme;
上面核心的配置是通过 http_connection
变量来决定 connection_upgrade
变量的内容。如果有 Upgrade 的,那么也在 Connection 上加上 Upgrade 的,否则就使用 keep-alive 作为内容
map $http_connection $connection_upgrade {
"~*Upgrade" $http_connection;
特别感谢 lsj 的协助,以及运维小伟大佬的方法
而我现在还有一个问题,我可以如何在遇到这样的问题的时候,通过我的应用的日志了解到
更多请看
“Connection: upgrade” causes 400 error that never reaches application code. Triggered by common nginx config. · Issue #17081 · dotnet/aspnetcore
[5.0] Allow/ignore upgrades with bodies by Tratcher · Pull Request #28896 · dotnet/aspnetcore
[3.1] Allow/ignore upgrades with bodies by Tratcher · Pull Request #28907 · dotnet/aspnetcore
[2.1] Allow/ignore upgrades with bodies by Tratcher · Pull Request #28908 · dotnet/aspnetcore
nginx 反向代理websocket – A Blog
Configure ASP.NET Core to work with proxy servers and load balancers
Host ASP.NET Core on Linux with Nginx
协议升级机制 - HTTP
Connection - HTTP
Kestrel returns 400 before reaching any of my code · Issue #4726 · dotnet/aspnetcore
How to log automatic 400 responses on model validation errors · Issue #12157 · dotnet/AspNetCore.Docs
Configure options for the ASP.NET Core Kestrel web server
Handle errors in ASP.NET Core
c# - How to auto log every request in .NET Core WebAPI? - Stack Overflow
原文链接: http://blog.lindexi.com/post/ASP.NET-Core-%E5%9B%A0%E4%B8%BA-Nginx-%E9%85%8D%E7%BD%AE-Connection-%E4%B8%BA-Upgrade-%E5%AF%BC%E8%87%B4-Kestrel-%E8%BF%94%E5%9B%9E-400-%E9%94%99%E8%AF%AF
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