Junio C Hamano <gitster@xxxxxxxxx> writes:
> And the unexpected discrepancy is reported by find_symref() as
> fatal. The server side dies, and somehow that fact is lost between
> the upload-pack process and the client and somebody in the middle
> (e.g. fastcgi interface or nginx webserver on the server side, or
> the remote-curl helper on the client side) keeps the "git fetch"
> process waiting.
>
> So there seem to be two issues.
>
> - Because of the unlocked read, find_symref() can observe an
> inconsistent state. Perhaps it should be updated not to die but
> to retry, expecting that transient inconsistency will go away.
>
> - A fatal error in upload-pack is not reported back to the client
> to cause it exit is an obvious one, and even if we find a way to
> make this fatal error in find_symref() not to trigger, fatal
> errors in other places in the code can trigger the same symptom.
I wonder if the latter is solved by recent patch 296b847c0d
("remote-curl: don't hang when a server dies before any output",
2016-11-18) on the client side.
-- >8 --
From: David Turner <dturner@xxxxxxxxxxxx>
Date: Fri, 18 Nov 2016 15:30:49 -0500
Subject: [PATCH] remote-curl: don't hang when a server dies before any output
In the event that a HTTP server closes the connection after giving a
200 but before giving any packets, we don't want to hang forever
waiting for a response that will never come. Instead, we should die
immediately.
One case where this happens is when attempting to fetch a dangling
object by its object name. In this case, the server dies before
sending any data. Prior to this patch, fetch-pack would wait for
data from the server, and remote-curl would wait for fetch-pack,
causing a deadlock.
Despite this patch, there is other possible malformed input that could
cause the same deadlock (e.g. a half-finished pktline, or a pktline but
no trailing flush). There are a few possible solutions to this:
1. Allowing remote-curl to tell fetch-pack about the EOF (so that
fetch-pack could know that no more data is coming until it says
something else). This is tricky because an out-of-band signal would
be required, or the http response would have to be re-framed inside
another layer of pkt-line or something.
2. Make remote-curl understand some of the protocol. It turns out
that in addition to understanding pkt-line, it would need to watch for
ack/nak. This is somewhat fragile, as information about the protocol
would end up in two places. Also, pkt-lines which are already at the
length limit would need special handling.
Both of these solutions would require a fair amount of work, whereas
this hack is easy and solves at least some of the problem.
Still to do: it would be good to give a better error message
than "fatal: The remote end hung up unexpectedly".
Signed-off-by: David Turner <dturner@xxxxxxxxxxxx>
Signed-off-by: Junio C Hamano <gitster@xxxxxxxxx>
---
remote-curl.c | 8 ++++++++
t/t5551-http-fetch-smart.sh | 30 ++++++++++++++++++++++++++++++
2 files changed, 38 insertions(+)
diff --git a/remote-curl.c b/remote-curl.c
index f14c41f4c0..ee4423659f 100644
--- a/remote-curl.c
+++ b/remote-curl.c
@@ -400,6 +400,7 @@ struct rpc_state {
size_t pos;
int in;
int out;
+ int any_written;
struct strbuf result;
unsigned gzip_request : 1;
unsigned initial_buffer : 1;
@@ -456,6 +457,8 @@ static size_t rpc_in(char *ptr, size_t eltsize,
{
size_t size = eltsize * nmemb;
struct rpc_state *rpc = buffer_;
+ if (size)
+ rpc->any_written = 1;
write_or_die(rpc->in, ptr, size);
return size;
}
@@ -659,6 +662,8 @@ static int post_rpc(struct rpc_state *rpc)
curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, rpc_in);
curl_easy_setopt(slot->curl, CURLOPT_FILE, rpc);
+
+ rpc->any_written = 0;
err = run_slot(slot, NULL);
if (err == HTTP_REAUTH && !large_request) {
credential_fill(&http_auth);
@@ -667,6 +672,9 @@ static int post_rpc(struct rpc_state *rpc)
if (err != HTTP_OK)
err = -1;
+ if (!rpc->any_written)
+ err = -1;
+
curl_slist_free_all(headers);
free(gzip_body);
return err;
diff --git a/t/t5551-http-fetch-smart.sh b/t/t5551-http-fetch-smart.sh
index 1ec5b2747a..43665ab4a8 100755
--- a/t/t5551-http-fetch-smart.sh
+++ b/t/t5551-http-fetch-smart.sh
@@ -276,6 +276,36 @@ test_expect_success 'large fetch-pack requests can be split across POSTs' '
test_line_count = 2 posts
'
+test_expect_success 'test allowreachablesha1inwant' '
+ test_when_finished "rm -rf test_reachable.git" &&
+ server="$HTTPD_DOCUMENT_ROOT_PATH/repo.git" &&
+ master_sha=$(git -C "$server" rev-parse refs/heads/master) &&
+ git -C "$server" config uploadpack.allowreachablesha1inwant 1 &&
+
+ git init --bare test_reachable.git &&
+ git -C test_reachable.git remote add origin "$HTTPD_URL/smart/repo.git" &&
+ git -C test_reachable.git fetch origin "$master_sha"
+'
+
+test_expect_success 'test allowreachablesha1inwant with unreachable' '
+ test_when_finished "rm -rf test_reachable.git; git reset --hard $(git rev-parse HEAD)" &&
+
+ #create unreachable sha
+ echo content >file2 &&
+ git add file2 &&
+ git commit -m two &&
+ git push public HEAD:refs/heads/doomed &&
+ git push public :refs/heads/doomed &&
+
+ server="$HTTPD_DOCUMENT_ROOT_PATH/repo.git" &&
+ master_sha=$(git -C "$server" rev-parse refs/heads/master) &&
+ git -C "$server" config uploadpack.allowreachablesha1inwant 1 &&
+
+ git init --bare test_reachable.git &&
+ git -C test_reachable.git remote add origin "$HTTPD_URL/smart/repo.git" &&
+ test_must_fail git -C test_reachable.git fetch origin "$(git rev-parse HEAD)"
+'
+
test_expect_success EXPENSIVE 'http can handle enormous ref negotiation' '
(
cd "$HTTPD_DOCUMENT_ROOT_PATH/repo.git" &&
--
2.11.0-442-g0c85c54a77