AddProxySupport on .NET Framework not working with UseForwardedHeaders

[gumbarros]

Describe the bug

As described in this issue , UseForwardedHeaders is not working, my website is displaying the subroute instead of the original request. I don't know if this is a SystemWebAdapter issue or YARP issue, please close this issue if it is 100% YARP related.

To Reproduce

Host in IIS a .NET Core website on www.site.com
Host in IIS a .NET Framework website on www.site.com/subapplication
Create a simple /Login route on .NET Framework website.
Add to .NET Framework website global.asax.vb:

   Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs)
        RegisterSystemWebAdapters()
        
        Log.AddInfo("Sistema Dansales Web Iniciado...")
        
        AreaRegistration.RegisterAllAreas()
        RegisterRoutes(RouteTable.Routes)
        RegisterGlobalFilters(GlobalFilters.Filters)

        AntiForgeryConfig.UniqueClaimTypeIdentifier = ClaimsIdentity.DefaultNameClaimType
    End Sub

    Private Sub RegisterSystemWebAdapters()
        AddSystemWebAdapters() _
        .AddProxySupport(Sub(options)
                                               options.UseForwardedHeaders = True
                                       End Sub)
     End Sub

Go to www.site.com

Expected:
www.site.com/Login

Actual:
www.site.com/subapplication/Login

Technical Info

ASP.NET Framework Application:

• Technologies and versions used: MVC + WebForms
• .NET Framework Version: 4.8
• Windows Version: Server 2012

ASP.NET Core Application:

• Targeted .NET version: 6.0
• .NET SDK version: 6.0

Why this is a migration problem

Because we have 100+ references using this getter:

        /// <summary>
        /// Captura a URL base do sistema
        /// </summary>
        /// <returns>URL</returns>
        /// <remarks>Lucio Pelinson 11-02-2009 / Gustavo Barros 24-08-2022</remarks>
        public static string PATH
        {
            get
            {
                var request = HttpContext.Current.Request;
                var helper = new UrlHelper(request.RequestContext);
                return string.Format("{0}://{1}{2}", request.Url.Scheme, request.Url.Authority, helper.Content("~"));
            }
        }

This causes many hyperlinks created with this getter to wrongly redirect only to the .NET Framework site instead of the Core one, but it don't happen when we use www.site.com/Login, only when we use www.site.com/subapplication/Login.

[twsouthwick]

Yes, the virtual path needs to be the same for this set up to work. Otherwise things like routing just don't work well. I'm happy to hear if someone is able to make it work, but I've gone down that rabbit hole and am fairly convinced that the path of the application needs to be the same.

I'm going to leave this open so we can ensure this is documented.

[gumbarros]

@twsouthwick thanks for the response! Is this the recommended structure? When I open /devCore, my site is still displaying /dev 😢

[twsouthwick]

@gumbarros I'm not an IIS expert, so I may not be interpreting that screenshot fully - please correct me if my understanding here is wrong.

It appears that you have dev and devCore as separate applications within the same site. Instead, you'll want to set it up so that they are on different sites. They can still have the same virtual directory/application structure, but the names of those must match.

[gumbarros]

@twsouthwick thank you very much! Solved my problem. For anyone with difficulties:



Just set the two websites with the same folder name.
The port 88 is the .NET Framework one, it's being hosted as localhost only. Edited appsettings.json to:

  "ReverseProxy": {
    "Routes": {
      "fallbackRoute": {
        "ClusterId": "fallbackCluster",
        "Order": "1",
        "Match": {
          "Path": "{**catch-all}"
        }
      }
    },
    "Clusters": {
      "fallbackCluster": {
        "Destinations": {
          "fallbackApp": {
            "Address": "http://localhost:8088/dev/"
          }
        }
      }
    }
  }

.NET Core app now reverse proxy to the .NET Framework localhost.
Also edited PATH getter to prevent localhost being displayed in hrefs and CSS files to the client.

        /// <summary>
        /// Captura a URL base do sistema
        /// </summary>
        /// <returns>URL</returns>
        /// <remarks>Lucio Pelinson 11-02-2009 / Gustavo Barros 24-08-2022</remarks>
        public static string PATH
        {
            get
            {
                var request = HttpContext.Current.Request;
                var helper = new UrlHelper(request.RequestContext);
                return helper.Content("~");
            }
        }

Congratulations to everyone on this project, everything working like a charm.