Re: RFC 9113 and :authority header field

[Martin Thomson <[e-mail]>]

On Thu, Jun 30, 2022, at 05:42, David Schinazi wrote:
> <<An intermediary that forwards a request over HTTP/2 MUST construct an 
> ":authority" pseudo-header field using the authority information from 
> the control data of the original request, unless the original request's 
> target URI does not contain authority information (in which case it MUST NOT generate ":authority").>>

Note the restoration of the final missing parenthetical.

> Am I misunderstanding something?

The distinction here is between requests that a client creates for itself and requests that it is forwarding.

The interpretation from Stefan is right: if you forward a request that only has Host and not :authority (perhaps because it came in HTTP/1.1) then you include "host" and not ":authority" in HTTP/2.

Consider also that not every HTTP/2 client conforms to RFC 9113; there are a number that conform to the language in RFC 7540.

(If your next point is that this could be clearer in the spec, I'm not going to disagree with you.)