curl / Mailing Lists / curl-library / Single Mail
Buy commercial curl support from WolfSSL. We help you work out your issues, debug your libcurl applications, use the API, port to new platforms, add new features and more. With a team lead by the curl founder himself.

Re: are ALPN values desirable command line options?

From: Stefan Eissing via curl-library <>
Date: Tue, 24 Oct 2023 09:00:13 +0200

> Am 24.10.2023 um 00:32 schrieb Stephen Farrell via curl-library <>:
> Hiya,
> On 23/10/2023 07:51, Daniel Stenberg wrote:
>> Are there actually cases where sending in a custom ALPN is likely to
>> be the right thing for a user to get a transfer going? I have not
>> heard of any such cases before.
> On 23/10/2023 08:44, Stefan Eissing wrote:
>> For this to work, curl needs to know the ALPN protocol. Because otherwise, it does not know how to talk to the server or understand
>> the answer. If one would specify "--alpn xyz" what should curl do
>> when "xyz" as negotiated?
> I'm sensing skepticism:-) But that's fine. I don't actually know if

Well, "skepticism" insofar as I fail to imagine how it should work. ;) Maybe you could describe what curl should do in such a case?

> there are many sites that really need an ALPN ID that's not tied to
> the HTTP version. I looked at the registry [1] and not many IDs seem
> to me to be both relevant to curl and where there's likely a benefit
> for the client in sending - maybe "acme-tls/1" but not sure.
> I do agree that the niche use-case I mentioned in the original mail
> wouldn't really justify adding such an option all by itself.
> That said, I'll ask a few people at the IETF meeting in a couple of
> weeks and see if there's more to it than that.
> If not, it's fine that this topic also fades away like the other
> from today (have to say, I liked Mark's phrasing of that one:-)
> Cheers,
> S.
> [1]
> <OpenPGP_0xE4D8E9F997A833DD.asc>--
> Unsubscribe:
> Etiquette:

Received on 2023-10-24