Re: HTTP/3 CONNECT requests, body, and trailers

On 2026-02-04 20:39, Martin Thomson wrote:
> RFC 9114 says:
> 
>> The request stream remains open at the end of the request to carry the data to be transferred. A CONNECT request that does not conform to these restrictions is malformed.
> 
> -- https://datatracker.ietf.org/doc/html/rfc9114#section-4.4-5
> 
> Reading on a little more, it's clear that the request we're talking about isn't a normal "headers, body, trailers" request, but you might be forgiven for starting to think otherwise.
> 
> Would it be worth an editorial erratum? I'd suggest the addition:

>> A CONNECT request consists of a header block only, it cannot
>> contain a body; similarly a CONNECT response consists of a header
>> block only. [...]

A CONNECT response other than 2xx may include a body, right? For 
example, a proxy may explain why it denied a particular CONNECT request.

Popular browsers refuse to share such proxy-generated CONNECT error 
response bodies with users, but the reasons behind that refusal are 
rooted in UI/UX concerns, rather than protocol limitations AFAICT.


HTH,

Alex.

Received on Thursday, 5 February 2026 18:56:21 UTC