Issues with git clone over HTTP/2 and closed connections

["David Härdeman" <david@hardeman.nu>]

Hi,

I just tried to clone a repo from a server over HTTPS, which failed with a message like this:

  error:  (curl_result = 55, http_code = 0, sha1 = <XYZ>
  error: Unable to find <XYZ> under https://example.com/myrepo.git
  Fetching objects: 20790, done.
  Cannot obtain needed tree <XYZ>
  while processing commit <ABC>
  error: fetch failed.

Every time I retried cloning, <XYZ> and <ABC> changed, but the error message was the same.

By running "GIT_CURL_VERBOSE=1 git clone https://example.com/myrepo.git", I noticed that:

  a) HTTP/2 was being used; and
  b) just before the error the server returned a GOAWAY [1]:
     "== Info: received GOAWAY, error=0, last_stream=1999"

On the client side I'm using Debian Unstable (libcurl 8.3.0, git 2.40.1), and the server is running Debian Stable (nginx 1.22.1-9).

nginx will, by default, close HTTP/2 connections after "http2_max_requests", (default: 1000, i.e. 1999 streams, note that the error message above says last_stream=1999) and it seems that it is using GOAWAY to do so, which seems to confuse git/libcurl.

And sure enough, after running "git config --global http.version HTTP/1.1" on the client and trying again, the "git clone" was successful (I'm guessing I could/should also bump http2_max_requests on the server).

From what I understand, git should close the connection, try to open a new one and resume the clone operation before erroring out (because the GOAWAY message could mean anything).

Is this a known bug and is it something that would need to be fixed in libcurl or in git?

Cheers,
David

PS. Not subscribed, please CC: me on any replies.

[1] https://www.rfc-editor.org/rfc/rfc7540#section-6.8
[2] http://nginx.org/en/docs/http/ngx_http_v2_module.html#http2_max_requests