How to change the “Connection: Keep-Alive” header to lowercase “keep-alive” in C#
How to change the “Connection: Keep-Alive” header to lowercase “keep-alive” in C#
I am sending some requests to a host which keeps rejecting my requests because of the Connection header in my requests. I need to change it to lowercase. I have the exact same issue as described in this question. However, that question is 3 years old, so I was wondering if there is a solution to this problem now?
Connection
The answer there talks about using reflection to remove the header first before setting it again in lower-case. Can someone explain how do I achieve that? Thanks.
@user2864740 No. "Some common headers are considered restricted and are either exposed directly by the API (such as Content-Type) or protected by the system and cannot be changed." Unfortunately,
Connection is one such header.– Anon
Jun 30 at 20:49
Connection
1 Answer
1
Stop and read this solution using reflection on ChangeInternal, which is probably a 'sufficient' level of reflection. When using it, do not set Connection via the property.
ChangeInternal
"And let's never speak of this again.."
private static void SetHeaderRestriction(string name, bool restricted) {
var hInfoPi = typeof(WebHeaderCollection)
.GetField("HInfo", BindingFlags.NonPublic | BindingFlags.Static);
var headerInfoTableType = hInfoPi.GetValue(null).GetType();
var headerInfoHashPi = headerInfoTableType
.GetField("HeaderHashTable", BindingFlags.NonPublic | BindingFlags.Static);
// Internal cache singleton of header info / restriction data
var headerInfoHash = (Hashtable)headerInfoHashPi.GetValue(null);
var connectionHeaderInfo = headerInfoHash["Connection"];
// IsRequestRestricted is 'readonly', but reflection can trump.
// An alternative would be to [temporarily] replace the entry entirely.
var restrictedPi = connectionHeaderInfo.GetType()
.GetField("IsRequestRestricted", BindingFlags.NonPublic | BindingFlags.Instance);
restrictedPi.SetValue(connectionHeaderInfo, restricted);
}
void Main()
{
var wr = (HttpWebRequest)WebRequest.Create("http://www.google.com");
SetHeaderRestriction("Connection", false);
wr.Headers["Connection"] = "keep-alive";
SetHeaderRestriction("Connection", true);
wr.Connection.Dump(); // "keep-alive"
((HttpWebResponse)wr.GetResponse()).StatusCode.Dump(); // OK
}
This code executes in LINQPad (which is where Dump() comes from) and .NET 4.7.1. YMMV.
Dump()
I am using HTTPWebRequest class and setting the headers using the Headers property. With your code, I see "Connection: keep-alive, Keep-Alive" in Fiddler, despite not using the Connection property anywhere in my code.
– Anon
Jul 1 at 7:40
Interesting. There must be something in the bowls of generating the request later sigh.
– user2864740
Jul 1 at 9:07
@Anon What happens if setting
wr.KeepAlive = false before assigning the header value? The default of the property is true. The "Keep-Alive" part of the header is coming in later, but should not be added if 'disabled' via the property.– user2864740
Jul 1 at 9:09
wr.KeepAlive = false
If I set
request.KeepAlive = false before assigning the header value, I get Connection: keep-alive, Close in the request header.– Anon
Jul 1 at 9:21
request.KeepAlive = false
Connection: keep-alive, Close
@Anon Ahh, per referencesource.microsoft.com/#system/net/system/Net/…
KeepAlive must be false and IsVersionHttp10 must be true or else "Keep-Alive" and/or "Close" will be added when preparing the request headers. However, that will also use "1.0" in the request elsewhere yuck!!! - what about using HttpClient? Is that more 'amendable'?– user2864740
Jul 1 at 19:11
KeepAlive
IsVersionHttp10
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– Simon Price
Jun 30 at 20:21