Kestrel server slow on “bad request data”

Question

I have an IOT device (black box, can't reprogram it) that sends http POST requests (136 bytes of JSON, a string) over wired ethernet to my .NET core 2.2 very simple server console application. I just output the string to the console.

    [HttpPost]
    public void Post([FromBody] RootObject root)
    {
        string adv = root.prt;
        Console.WriteLine(adv);
    }

I get to display less than 1 line per second, sometimes 2.

Using Fiddler as a reverse proxy, instead I receive between 5 and 10 http req per second, that is the correct behavior of the device.

So I enabled Information logs, and get this, every second, with that "Invalid request line" error:

info: Microsoft.AspNetCore.Hosting.Internal.WebHost[1]
      Request starting HTTP/1.1 POST http://192.168.0.92/api/values application/json 136
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[0]
      Executing endpoint 'BluepycWeb.Controllers.ValuesController.Post (BluepycWeb)'
info: Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker[1]
      Route matched with {action = "Post", controller = "Values"}. Executing action BluepycWeb.Controllers.ValuesController.Post (BluepycWeb)
02003F002293831000010033FF0006EFAA256B6D1A001E010201061AFF4C000215476C6F62616C2D54616700000000000000000000CD0101CC0001FF001FCC
info: Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker[1]
      Executing action method BluepycWeb.Controllers.ValuesController.Post (BluepycWeb) with arguments (BluepycWeb.Controllers.RootObject) - Validation state: Valid
info: Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker[2]
      Executed action method BluepycWeb.Controllers.ValuesController.Post (BluepycWeb), returned result Microsoft.AspNetCore.Mvc.EmptyResult in 0.2158ms.
info: Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker[2]
      Executed action BluepycWeb.Controllers.ValuesController.Post (BluepycWeb) in 9.4032ms
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[1]
      Executed endpoint 'BluepycWeb.Controllers.ValuesController.Post (BluepycWeb)'
info: Microsoft.AspNetCore.Hosting.Internal.WebHost[2]
      Request finished in 24.5625ms 200
info: Microsoft.AspNetCore.Server.Kestrel[17]
      Connection id "0HLMO99UNQBGM" bad request data: "Invalid request line: '\x0D\x0A'"
Microsoft.AspNetCore.Server.Kestrel.Core.BadHttpRequestException: Invalid request line: '\x0D\x0A'
   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpParser`1.RejectRequestLine(Byte* requestLine, Int32 length)
   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpParser`1.GetUnknownMethod(Byte* data, Int32 length, Int32& methodLength)
   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpParser`1.ParseRequestLine(TRequestHandler handler, Byte* data, Int32 length)
   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpParser`1.ParseRequestLine(TRequestHandler handler, ReadOnlySequence`1& buffer, SequencePosition& consumed, SequencePosition& examined)
   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpParser`1.Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.IHttpParser<TRequestHandler>.ParseRequestLine(TRequestHandler handler, ReadOnlySequence`1& buffer, SequencePosition& consumed, SequencePosition& examined)
   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.Http1Connection.TakeStartLine(ReadOnlySequence`1 buffer, SequencePosition& consumed, SequencePosition& examined)
   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.Http1Connection.ParseRequest(ReadOnlySequence`1 buffer, SequencePosition& consumed, SequencePosition& examined)
   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.Http1Connection.TryParseRequest(ReadResult result, Boolean& endConnection)
   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)

If I send the same JSON paylod through Postman continuosly, no errors, no delays. That error, that I don't know how to avoid nor by what is originated (but it seems it doesn't distub Fiddler) seems to hang my server for a second.

Any suggestion on how can I solve this problem? Discard/correct the error? Keep the error but not slowing down the data receive?

UPDATE: Hosting with IISExpress, no problem, no "Invalid request line: '\x0D\x0A'" error, very fast. Problem is only using Kestrel.

Thanks!

Answer 1

Yesterday I had same issue with my ASP .NETCore service. Then realized I was sending HTTPS requests to my Kestrel server while it isn't configured to listen at HTTPS protocol, that's why Kestrel complaining.

If you want to use HTTPS in your kestrel you have multiple options to configure it, for example :

With assigned server certificate :

var host = new WebHostBuilder() .UseKestrel(options => options.Listen(IPAddress.Any, 443, listenOptions => listenOptions.UseHttps("MyCert.pfx")))

With multiple hostnames and certificates :

public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
WebHost.CreateDefaultBuilder(args)
    .UseStartup<Startup>()
    .ConfigureKestrel((context, options) =>
    {
        options.ListenAnyIP(5005, listenOptions =>
        {
            listenOptions.UseHttps(httpsOptions =>
            {
                var localhostCert = CertificateLoader.LoadFromStoreCert(
                    "localhost", "My", StoreLocation.CurrentUser, 
                    allowInvalid: true);
                var exampleCert = CertificateLoader.LoadFromStoreCert(
                    "example.com", "My", StoreLocation.CurrentUser, 
                    allowInvalid: true);
                var subExampleCert = CertificateLoader.LoadFromStoreCert(
                    "sub.example.com", "My", StoreLocation.CurrentUser, 
                    allowInvalid: true);
                var certs = new Dictionary<string, X509Certificate2>(
                    StringComparer.OrdinalIgnoreCase);
                certs["localhost"] = localhostCert;
                certs["example.com"] = exampleCert;
                certs["sub.example.com"] = subExampleCert;

                httpsOptions.ServerCertificateSelector = (connectionContext, name) =>
                {
                    if (name != null && certs.TryGetValue(name, out var cert))
                    {
                        return cert;
                    }

                    return exampleCert;
                };
            });
        });
    });