Correct syntax of a HTTP 100 Continue response

Question

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

I searched on the web for a while and had a look at different implementations. However, there is one thing I'm not sure of. what is the correct syntax of a 100 Continue message? Several sources claim, that this must be a single response line without any further header lines. However, I can't find that in the RFC 2616 reflected. 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 only of the Status-Line and optional headers, and is terminated by an empty line. There are no required headers for this class of status code. ..."