From: Stefan Beller <sbeller@google.com>
To: Jeff King <peff@peff.net>
Cc: Junio C Hamano <gitster@pobox.com>,
"git@vger.kernel.org" <git@vger.kernel.org>,
Duy Nguyen <pclouds@gmail.com>
Subject: Re: [RFC/WIP PATCH 11/11] Document protocol version 2
Date: Mon, 1 Jun 2015 16:14:15 -0700 [thread overview]
Message-ID: <CAGZ79kaRTLX7eBCOA=yQHVwcN-H-o_aZFfQ1gw7Nx-NC82pbag@mail.gmail.com> (raw)
In-Reply-To: <20150529222120.GB15678@peff.net>
On Fri, May 29, 2015 at 3:21 PM, Jeff King <peff@peff.net> wrote:
> On Fri, May 29, 2015 at 02:52:14PM -0700, Junio C Hamano wrote:
>
>> > Currently we can do a = as part of the line after the first ref, such as
>> >
>> > symref=HEAD:refs/heads/master agent=git/2:2.4.0
>> >
>> > so I thought we want to keep this.
>>
>> I do not understand that statement.
>>
>> Capability exchange in v2 is one packet per cap, so the above
>> example would be expressed as:
>>
>> symref=HEAD:refs/heads/master
>> agent=git/2:2.4.0
>>
>> right? Your "keyvaluepair" is limited to [a-z0-9-_=]*, and neither
>> of the above two can be expressed with that, which was why I said
>> you need two different set of characters before and after "=". Left
>> hand side of "=" is tightly limited and that is OK. Right hand side
>> may contain characters like ':', '.' and '/', so your alphabet need
>> to be more lenient, even in v1 (which I would imagine would be "any
>> octet other than SP, LF and NUL").
I think the recent issue with the push certificates shows that having arbitrary
data after the = is a bad idea. So we need to be very cautious when to allow
which data after the =.
I'll try split up the patch.
>
> Yes. See git_user_agent_sanitized(), for example, which allows basically
> any printable ASCII except for SP.
>
> I think the v2 capabilities do not even need to have that restriction.
> It can allow arbitrary binary data, because it has an 8bit-clean framing
> mechanism (pkt-lines). Of course, that means such capabilities cannot be
> represented in a v1 conversation (whose framing mechanism involves SP
> and NUL). But it's probably acceptable to introduce new capabilities
> which are only available in a v2 conversation. Old clients that do not
> understand v2 would not understand the capability either. It does
> require new clients implementing the capability to _also_ implement v2
> if they have not done so, but I do not mind pushing people in that
> direction.
>
> The initial v2 client implementation should probably do a few cautionary
> things, then:
>
> 1. Do _not_ fold the per-pkt capabilities into a v1 string; that loses
> the robust framing. I suggested string_list earlier, but probably
> we want a list of ptr/len pair, so that it can remain NUL-clean.
>
> 2. Avoid holding on to unknown packets longer than necessary. Some
> capability pkt-lines may be arbitrarily large (up to 64K). If we do
> not understand them during the v2 read of the capabilities, there
> is no point hanging on to them. It's not _wrong_ to do so, but just
> inefficient; if we know that clients will just throw away unknown
> packets, then we can later introduce new packets with large data,
> without worrying about wasting the client's resources.
>
> I suspect it's not that big a deal either way, though. I have no
> plans for sending a bunch of large packets, and anyway network
> bandwidth is probably more precious than client memory.
That's very sensible thoughts after rereading this email. The version
I'll be sending out today will not follow those suggestions though. :(
>
> -Peff
next prev parent reply other threads:[~2015-06-01 23:14 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-26 22:01 [RFC/WIP PATCH 00/11] Protocol version 2, again! Stefan Beller
2015-05-26 22:01 ` [RFC/WIP PATCH 01/11] upload-pack: make client capability parsing code a separate function Stefan Beller
2015-05-26 22:01 ` [RFC/WIP PATCH 02/11] upload-pack: only accept capabilities on the first "want" line Stefan Beller
2015-05-26 22:17 ` Junio C Hamano
2015-05-26 22:20 ` Stefan Beller
2015-05-26 22:01 ` [RFC/WIP PATCH 03/11] upload-pack: move capabilities out of send_ref Stefan Beller
2015-05-26 22:01 ` [RFC/WIP PATCH 04/11] upload-pack-2: Implement the version 2 of upload-pack Stefan Beller
2015-05-27 2:30 ` Eric Sunshine
2015-05-27 6:35 ` Jeff King
2015-05-27 17:30 ` Eric Sunshine
2015-05-27 20:14 ` Jeff King
2015-05-27 17:40 ` Stefan Beller
2015-05-27 20:34 ` Jeff King
2015-05-27 20:45 ` Stefan Beller
2015-05-27 21:46 ` Jeff King
2015-05-26 22:01 ` [RFC/WIP PATCH 05/11] transport: add infrastructure to support a protocol version number Stefan Beller
2015-05-27 6:39 ` Jeff King
2015-05-27 19:01 ` Stefan Beller
2015-05-27 20:17 ` Jeff King
2015-05-27 19:10 ` Junio C Hamano
2015-05-26 22:01 ` [RFC/WIP PATCH 06/11] remote.h: add get_remote_capabilities, request_capabilities Stefan Beller
2015-05-27 3:25 ` Eric Sunshine
2015-05-27 6:50 ` Jeff King
2015-05-27 17:19 ` Eric Sunshine
2015-05-27 20:09 ` Jeff King
2015-05-27 6:45 ` Jeff King
2015-05-29 19:39 ` Stefan Beller
2015-05-29 22:08 ` Jeff King
2015-05-26 22:01 ` [RFC/WIP PATCH 07/11] fetch-pack: use the configured transport protocol Stefan Beller
2015-05-26 22:19 ` Junio C Hamano
2015-05-26 22:23 ` Stefan Beller
2015-05-27 6:53 ` Jeff King
2015-05-26 22:01 ` [RFC/WIP PATCH 08/11] transport: connect_setup appends protocol version number Stefan Beller
2015-05-26 22:21 ` Junio C Hamano
2015-05-26 22:31 ` Stefan Beller
2015-05-27 5:09 ` Junio C Hamano
2015-05-27 6:56 ` Jeff King
2015-05-27 3:33 ` Eric Sunshine
2015-05-27 7:02 ` Jeff King
2015-05-26 22:01 ` [RFC/WIP PATCH 09/11] transport: get_refs_via_connect exchanges capabilities before refs Stefan Beller
2015-05-27 5:37 ` Eric Sunshine
2015-05-27 7:06 ` Jeff King
2015-05-26 22:01 ` [RFC/WIP PATCH 10/11] t5544: add a test case for the new protocol Stefan Beller
2015-05-27 5:34 ` Eric Sunshine
2015-05-27 7:12 ` Jeff King
2015-05-26 22:01 ` [RFC/WIP PATCH 11/11] Document protocol version 2 Stefan Beller
2015-05-29 20:35 ` Junio C Hamano
2015-05-29 21:36 ` Stefan Beller
2015-05-29 21:52 ` Junio C Hamano
2015-05-29 22:21 ` Jeff King
2015-06-01 23:14 ` Stefan Beller [this message]
2015-06-01 23:40 ` Stefan Beller
2015-06-04 13:18 ` Jeff King
2015-06-04 17:01 ` Junio C Hamano
2015-06-02 17:06 ` Junio C Hamano
2015-05-27 6:18 ` [RFC/WIP PATCH 00/11] Protocol version 2, again! Jeff King
2015-05-27 7:08 ` Jeff King
2015-06-01 17:49 ` Stefan Beller
2015-06-02 10:10 ` Duy Nguyen
2015-06-04 13:09 ` Jeff King
2015-06-04 16:44 ` Stefan Beller
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