upload-pack: use PARSE_OBJECT_SKIP_HASH_CHECK in more places
In commit 0bc2557951 (upload-pack: skip parse-object re-hashing of
"want" objects, 2022-09-06), we optimized the parse_object() calls for
v2 "want" lines from the client so that they avoided parsing blobs, and
so that they used the commit-graph rather than parsing commit objects
from scratch.
We should extend that to two other spots:
1. We parse "have" objects in the got_oid() function. These won't
generally be non-commits (unlike "want" lines from a partial
clone). But we still benefit from the use of the commit-graph.
2. For v0, the "want" lines are parsed in receive_needs(). These are
also less likely to be non-commits because by default they have to
be ref tips. There are config options you might set to allow
non-tip objects, but you'd mostly do so to support partial clones,
and clients recent enough to support partial clone will generally
speak v2 anyway.
So I don't expect this change to improve performance much for day-to-day
operations. But both are possible denial-of-service vectors, where an
attacker can waste our time by sending over a large number of objects to
parse (of course we may waste even more time serving a pack to them, but
we try as much as possible to optimize that in pack-objects; we should
do what we can here in upload-pack, too).
With this patch, running p5600 with GIT_TEST_PROTOCOL_VERSION=0 shows
similar results to what we saw in 0bc2557951 (which ran with the v2
protocol by default). Here are the numbers for linux.git:
Test HEAD^ HEAD
-----------------------------------------------------------------------------
5600.3: checkout of result 50.91(87.95+2.93) 41.75(79.00+3.18) -18.0%
Or for a more extreme (and malicious) case, we can claim to "have" every
blob in git.git over the v0 protocol:
$ {
echo "0032want $(git rev-parse HEAD)"
printf 0000
git cat-file --batch-all-objects --batch-check='%(objectname) %(objecttype)' |
perl -alne 'print "0032have $F[0]" if $F[1] eq "blob"'
} >input
$ time ./git.old upload-pack . <input >/dev/null
real 0m52.951s
user 0m51.633s
sys 0m1.304s
$ time ./git.new upload-pack . <input >/dev/null
real 0m0.261s
user 0m0.156s
sys 0m0.105s
(Note that these don't actually compute a pack because of the hacky
protocol usage, so those numbers are representing the raw blob-parsing
effort done by upload-pack).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/upload-pack.c b/upload-pack.c
index 3970bb9..b721155 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -469,7 +469,8 @@ static void create_pack_file(struct upload_pack_data *pack_data,
static int do_got_oid(struct upload_pack_data *data, const struct object_id *oid)
{
int we_knew_they_have = 0;
- struct object *o = parse_object(the_repository, oid);
+ struct object *o = parse_object_with_flags(the_repository, oid,
+ PARSE_OBJECT_SKIP_HASH_CHECK);
if (!o)
die("oops (%s)", oid_to_hex(oid));
@@ -1148,7 +1149,8 @@ static void receive_needs(struct upload_pack_data *data,
free(client_sid);
}
- o = parse_object(the_repository, &oid_buf);
+ o = parse_object_with_flags(the_repository, &oid_buf,
+ PARSE_OBJECT_SKIP_HASH_CHECK);
if (!o) {
packet_writer_error(&data->writer,
"upload-pack: not our ref %s",
