Valid HTTP 100 Continue Response Syntax

Question

For me, one of the weakest points of the HTTP 1.1 RFC and various implementations is how to deal with 100 Continue headers.

I searched the Internet for a while and looked at various implementations. However, there is one thing I'm not sure about. What is the correct syntax for a 100 Continue message? Several sources claim this should be the only response line without any additional header lines. However, I cannot find this in RFC 2616. So, what is right?

HTTP/1.1 100 Continue 

or

 HTTP/1.1 100 Continue [Additional Headers…] 

?

Answer 1

RFC 2616, Section 10.1 : “This class of status code indicates a provisional response, consisting of only status lines and additional headers, and ends with an empty line. There are no required headers for this class of status code ...”