Currently writing an API that accepts files using multipart/form-data. Below are my settings in Web.config. IIS is set to 1.0737GB limit and .NET is set to a 1.0485GB limit.
<httpRuntime requestValidationMode="2.0" maxRequestLength="1048576" executionTimeout="1000000" targetFramework="4.7.1" />
<requestFiltering>
<requestLimits maxAllowedContentLength="1073741824" />
</requestFiltering>
When I upload a file around 1.5-2GB in size I get a 404 back as described in the Microsoft documentation linked below. This is my expected response from the server. But, when I upload a much larger file, around 2.5GB+, I get a 400 Bad Request instead. I have been looking around for documentation to describe why this would happen and why I would not expect to always see a 404 instead, but have found nothing stating a 400 could be returned. The only difference between the requests is the files attached, nothing else is changed. To make the larger file size I also just zipped two of the original file that throws the 404 together. As additional details, the endpoint is covered in Unit and Integration tests that verify normal use case functionality. The endpoint works when manually tested with files below the IIS/.NET set limits. This behavior has also been seen when manually tested with a C# library project as well as Postman. Any help is greatly appreciated, thanks in advance!
https://docs.microsoft.com/en-us/iis/configuration/system.webserver/security/requestfiltering/
Clarification on my use case: A clarification is that I'm not trying to increase the size limit of my requests, I just need to make sure anything over the size limit returns the same error. The documentation that will be publicly available needs to state the return value in case of error and currently it can be either a 404 or a 400 and I can't explain explicitly why in the documentation yet.
