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When upload-pack sees a "have" line in the v0 protocol, it immediately calls got_oid() with its argument and potentially produces an ACK response. In the v2 protocol, we simply record the argument in an oid_array, and only later process all of the "have" objects by calling the equivalent of got_oid() on the contents of the array. This makes some sense, as v2 is a pure request/response protocol, as opposed to v0's asynchronous negotiation phase. But there's a downside: a client can send us an infinite number of garbage "have" lines, which we'll happily slurp into the array, consuming memory. Whereas in v0, they are limited by the number of objects in the repository (because got_oid() only records objects we have ourselves, and we avoid duplicates by setting a flag on the object struct). We can make v2 behave more like v0 by also calling got_oid() directly when v2 parses a "have" line. Calling it early like this is OK because got_oid() itself does not interact with the client; it only confirms that we have the object and sets a few flags. Note that unlike v0, v2 does not ever (before or after this patch) check the return code of got_oid(), which lets the caller know whether we have the object. But again, that makes sense; v0 is using it to asynchronously tell the client to stop sending. In v2's synchronous protocol, we just discard those entries (and decide how to ACK at the end of each round). There is one slight tweak we need, though. In v2's state machine, we reach the SEND_ACKS state if the other side sent us any "have" lines, whether they were useful or not. Right now we do that by checking whether the "have" array had any entries, but if we record only the useful ones, that doesn't work. Instead, we can add a simple boolean that tells us whether we saw any have line (even if it was useless). This lets us drop the "haves" array entirely, as we're now placing objects directly into the "have_obj" object array (which is where got_oid() put them in the long run anyway). And as a bonus, we can drop the secondary "common" array used in process_haves_and_send_acks(). It was essentially a copy of "haves" minus the objects we do not have. But now that we are using "have_obj" directly, we know everything in it is useful. So in addition to protecting ourselves against malicious input, we should slightly lower our memory usage for normal inputs. Note that there is one user-visible effect. The trace2 output records the number of "haves". Previously this was the total number of "have" lines we saw, but now is the number of useful ones. We could retain the original meaning by keeping a separate counter, but it doesn't seem worth the effort; this trace info is for debugging and metrics, and arguably the count of common oids is at least as useful as the total count. Reported-by: Benjamin Flesch <benjaminflesch@icloud.com> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Git - fast, scalable, distributed revision control system
Git is a fast, scalable, distributed revision control system with an unusually rich command set that provides both high-level operations and full access to internals.
Git is an Open Source project covered by the GNU General Public License version 2 (some parts of it are under different licenses, compatible with the GPLv2). It was originally written by Linus Torvalds with help of a group of hackers around the net.
Please read the file INSTALL for installation instructions.
Many Git online resources are accessible from https://git-scm.com/ including full documentation and Git related tools.
See Documentation/gittutorial.txt to get started, then see
Documentation/giteveryday.txt for a useful minimum set of commands, and
Documentation/git-<commandname>.txt for documentation of each command.
If git has been correctly installed, then the tutorial can also be
read with man gittutorial or git help tutorial, and the
documentation of each command with man git-<commandname> or git help <commandname>.
CVS users may also want to read Documentation/gitcvs-migration.txt
(man gitcvs-migration or git help cvs-migration if git is
installed).
The user discussion and development of Git take place on the Git mailing list -- everyone is welcome to post bug reports, feature requests, comments and patches to git@vger.kernel.org (read Documentation/SubmittingPatches for instructions on patch submission and Documentation/CodingGuidelines).
Those wishing to help with error message, usage and informational message
string translations (localization l10) should see po/README.md
(a po file is a Portable Object file that holds the translations).
To subscribe to the list, send an email to git+subscribe@vger.kernel.org (see https://subspace.kernel.org/subscribing.html for details). The mailing list archives are available at https://lore.kernel.org/git/, https://marc.info/?l=git and other archival sites.
Issues which are security relevant should be disclosed privately to the Git Security mailing list git-security@googlegroups.com.
The maintainer frequently sends the "What's cooking" reports that list the current status of various development topics to the mailing list. The discussion following them give a good reference for project status, development direction and remaining tasks.
The name "git" was given by Linus Torvalds when he wrote the very first version. He described the tool as "the stupid content tracker" and the name as (depending on your mood):
- random three-letter combination that is pronounceable, and not actually used by any common UNIX command. The fact that it is a mispronunciation of "get" may or may not be relevant.
- stupid. contemptible and despicable. simple. Take your pick from the dictionary of slang.
- "global information tracker": you're in a good mood, and it actually works for you. Angels sing, and a light suddenly fills the room.
- "goddamn idiotic truckload of sh*t": when it breaks