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Re: HTTP/3 options

From: Stefan Eissing via curl-library <>
Date: Wed, 4 Jan 2023 11:04:23 +0100

> Am 04.01.2023 um 10:50 schrieb Daniel Stenberg <>:
> On Wed, 4 Jan 2023, Stefan Eissing wrote:
>> And then there are the cases where someone really wants to nail it down. That is what we are talking here, I guess. Ultimately, what is given on the command line is converted by curl into TCP and/or QUIC and the ALPN list for the connection (ignoring the http: cases). For people who really want to control this, specifying the ALPN list on the command line seems the best option. Someone might want to check if a server is willing to negotiate "h3-29", for example.
> I actually don't think we've had users ask for this level of fiddling in the past.
> If we would allow that, I imagine we need to provide a mapping as well. Like send APLN XXX and if agreed to, treat it as if it is YYYY. If not, curl itself would need to know that "h3-moonbase" is that new magic h3 attempt I work on in secret, possibly by making assumptions about how the id is created.

I think we need to deal with those values found in HTTPS records. If we want to expose that on the command line is another thing. agreed.

> Something like:
> --alpn-pref h3-29=h3
> I am however not convinced that we need to go that route unless a user actually steps forward and explains a use case for this.
>> Besides that, we are talking about usability, e.g. making it easy to specify a common ALPN list. Currently, we have implied ALPNs (**):
>> - "--http1.1" -> ALPN "http/1.1"
>> - "--http2" -> ALPN "h2,http/1.1"
>> - "--http3" -> ALPN "h3" (*experimental, changeable)
>> - none -> ALPN "h2,http/1.1" (used to be only "http/1.1" when h2 was experimental)
>> - future none -> ALPN "h3,h2,http/1.1" (once, h3 leaves experimental)
>> right?
> Yes, in practise that is what we are talking about. My thinking is however that the term alpn is too esoteric and unknown for users of the tool and therefore I rather expose and talk about this in the terms of "HTTP versions". A little simplified, but I think it can work.


  --proto h3,h2
  --proto http3,http2
  --proto http1-3

work here?

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Received on 2023-01-04