On Fri, May 29, 2015 at 3:21 PM, Jeff King <p...@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 -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
