参考链接：

• https://learn.microsoft.com/zh-cn/aspnet/core/host-and-deploy/proxy-load-balancer

• https://www.cnblogs.com/wswind/p/11065038.html

• https://imququ.com/post/x-forwarded-for-header-in-http.html

• https://www.nginx.com/resources/wiki/start/topics/examples/forwarded/

Net Core Header 转接头替换方案

nginx等代理服务器在转发时，会使用X-Forwarded-For 请求头。该请求头会记录从请求者ip到层层代理服务器ip的信息。

asp.net core 在使用转发服务器后，官方文档说需要使用中间件设置XForwardedFor与XForwardedProto

https://learn.microsoft.com/zh-cn/aspnet/core/host-and-deploy/proxy-load-balancer

app.UseForwardedHeaders(new ForwardedHeadersOptions
{
    ForwardedHeaders = ForwardedHeaders.XForwardedFor | ForwardedHeaders.XForwardedProto
});

app.UseAuthentication();

使用X-Forwarded-For会更新 HttpContext.Connection.RemoteIpAddress
使用X-Forwarded-Proto会更新 HttpContext.Request.Scheme
使用X-Forwarded-Host会更新 HttpContext.Request.Host

此配置只对Nginx与项目同时部署在同一台server（本机localhost）时有效，多台server需在项目中配置代理的IP地址才能有效的替换转接头信息，代码如下：

app.UseForwardedHeaders(new ForwardedHeadersOptions
{
    ForwardedHeaders = ForwardedHeaders.XForwardedFor | ForwardedHeaders.XForwardedProto,
    KnownProxies = { IPAddress.Parse("172.17.0.0") }
});

也可通过KnownNetworks属性配置代理地址范围。

附nginx 配置

 location / {
        proxy_pass         http://localhost:5000;
        proxy_http_version 1.1;
        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;
    }