Beta: Kestrel engine no longer adds the Via header to passed-through requests

Description

The Kestrel engine in the beta doesn't add the Via header to requests that Dev Proxy passes through to the origin. v3.3.1 adds it.

The header was added on purpose in #83 so that APIs can see that traffic went through Dev Proxy. In v3.3.1 it's set on every passed-through request:

dev-proxy/DevProxy/Proxy/ProxyEngine.cs

Lines 582 to 587 in 8dbf5e2

    
           // We only need to set the proxy header if the proxy has not set a response and the request is going to be sent to the target. 
        
           if (!proxyRequestArgs.ResponseState.HasBeenSet) 
        
           { 
        
               _logger?.LogRequest("Passed through", MessageType.PassedThrough, new LoggingContext(e)); 
        
               AddProxyHeader(e.HttpClient.Request); 
        
           }

dev-proxy/DevProxy/Proxy/ProxyEngine.cs

Line 835 in 8dbf5e2

private static void AddProxyHeader(Request r) => r.Headers?.AddHeader("Via", $"{r.HttpVersion} dev-proxy/{ProxyUtils.ProductVersion}");

AddProxyHeader was removed in the Kestrel migration (#1854), and UpstreamForwarder only copies the client's headers:

dev-proxy/DevProxy.Proxy.Kestrel/Internal/UpstreamForwarder.cs

Lines 30 to 57 in 43b3724

    
           public async Task<OriginResponse> ForwardAsync(IHttpRequest request, CancellationToken ct) 
        
           { 
        
               using var outgoing = new HttpRequestMessage(new HttpMethod(request.Method), request.RequestUri); 
        
               ByteArrayContent? content = null; 
        
               if (request.HasBody) 
        
               { 
        
                   content = new ByteArrayContent(request.Body.ToArray()); 
        
                   outgoing.Content = content; 
        
               } 
        
               var requestConnectionHeaders = GetConnectionHeaderNames(request.Headers); 
        
               foreach (var header in request.Headers) 
        
               { 
        
                   if (IsHopByHop(header.Name) 
        
                       || requestConnectionHeaders.Contains(header.Name) 
        
                       || string.Equals(header.Name, "Host", StringComparison.OrdinalIgnoreCase) 
        
                       || string.Equals(header.Name, "Expect", StringComparison.OrdinalIgnoreCase) 
        
                       || string.Equals(header.Name, "Content-Length", StringComparison.OrdinalIgnoreCase)) 
        
                   { 
        
                       continue; 
        
                   } 
        
                   if (!outgoing.Headers.TryAddWithoutValidation(header.Name, header.Value)) 
        
                   { 
        
                       _ = content?.Headers.TryAddWithoutValidation(header.Name, header.Value); 
        
                   } 
        
               }

RFC 9110 also says that a proxy MUST send an appropriate Via header in each message that it forwards: https://www.rfc-editor.org/rfc/rfc9110#section-7.6.3

Expected behaviour

Passed-through requests include Via: <http-version> dev-proxy/<version>, for example Via: 1.1 dev-proxy/4.0.0, like in v3.3.1. The header is appended to any existing Via value.

Actual behaviour

Requests reach the origin without a Via header.

Steps to reproduce

Start the beta with urlsToWatch set to https://httpbin.org/* and no plugins that set a response.
Run curl -x http://127.0.0.1:8000 -k https://httpbin.org/headers
The echoed headers don't include Via. With v3.3.1 they include Via: 1.1 dev-proxy/3.3.1.

Dev Proxy Version

4.0.0-beta.9 (main @ 43b3724). Not affected: v3.3.1.

Additional Info

Plugins don't see the header in the beta either, so recorded traffic changes. For example, the generated .http file samples in the docs show a Via: 1.1 dev-proxy/... line.

Add Via header to passed-through requests in Kestrel engine. Closes d…

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Beta: Kestrel engine no longer adds the Via header to passed-through requests #1948

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Dev Proxy Version

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	// We only need to set the proxy header if the proxy has not set a response and the request is going to be sent to the target.
	if (!proxyRequestArgs.ResponseState.HasBeenSet)
	{
	_logger?.LogRequest("Passed through", MessageType.PassedThrough, new LoggingContext(e));
	AddProxyHeader(e.HttpClient.Request);
	}

	public async Task<OriginResponse> ForwardAsync(IHttpRequest request, CancellationToken ct)
	{
	using var outgoing = new HttpRequestMessage(new HttpMethod(request.Method), request.RequestUri);

	ByteArrayContent? content = null;
	if (request.HasBody)
	{
	content = new ByteArrayContent(request.Body.ToArray());
	outgoing.Content = content;
	}

	var requestConnectionHeaders = GetConnectionHeaderNames(request.Headers);
	foreach (var header in request.Headers)
	{
	if (IsHopByHop(header.Name)
	\|\| requestConnectionHeaders.Contains(header.Name)
	\|\| string.Equals(header.Name, "Host", StringComparison.OrdinalIgnoreCase)
	\|\| string.Equals(header.Name, "Expect", StringComparison.OrdinalIgnoreCase)
	\|\| string.Equals(header.Name, "Content-Length", StringComparison.OrdinalIgnoreCase))
	{
	continue;
	}

	if (!outgoing.Headers.TryAddWithoutValidation(header.Name, header.Value))
	{
	_ = content?.Headers.TryAddWithoutValidation(header.Name, header.Value);
	}
	}

Beta: Kestrel engine no longer adds the Via header to passed-through requests #1948

Description

Description

Expected behaviour

Actual behaviour

Steps to reproduce

Dev Proxy Version

Additional Info

Activity

Metadata

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