Re: [PATCH v2 5/8] Documentation: add Packfile URIs design doc

From: Jonathan Nieder <jrnieder@gmail.com>
Date: Apr 23, 2019, 22:11 UTC
Message-ID: <20190423221159.GA98980@google.com>
In-Reply-To: <20190423053130.GA13162@sigill.intra.peff.net>

Hi,

Jeff King wrote:

> On Fri, Mar 08, 2019 at 01:55:17PM -0800, Jonathan Tan wrote:

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>> +If the 'packfile-uris' feature is advertised, the following argument
>> +can be included in the client's request as well as the potential
>> +addition of the 'packfile-uris' section in the server's response as
>> +explained below.
>> +
>> +    packfile-uris <comma-separated list of protocols>
>> +	Indicates to the server that the client is willing to receive
>> +	URIs of any of the given protocols in place of objects in the
>> +	sent packfile. Before performing the connectivity check, the
>> +	client should download from all given URIs. Currently, the
>> +	protocols supported are "http" and "https".
>
> This negotiation seems backwards to me, because it puts too much power
> in the hands of the server.

Thanks. Forgive me if this was covered earlier in the conversation, but why do we need more than one protocol at all here? Can we restrict this to only-https, all the time?

[...]

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> The problem I see is that the client doesn't get to vet the list of
> URIs; it only gets to specify a protocol match. But there are many other
> reasons it might want to reject a URI: we don't like the protocol, the
> domain name is on a blacklist (or not on a whitelist), the domain name
> can't resolve, we can't make a TCP connection to the server, we can't
> successfully fetch the pack.

Christian mentioned this desire to vet URIs before, and I'll admit I found it hard to imagine a use case. Why can't it work like e.g. <frame> on the web, where if you don't like that domain, then you don't get to access the page? From a server operator's point of view, if you want to support a second URI that more clients support, why wouldn't you just always use that second URI instead of making clients choose?

Thanks and hope that helps, Jonathan