Configuring Git Protocol v2

Version history

Git protocol v2 improves the v1 wire protocol in several ways and is enabled by default in GitLab for HTTP requests. In order to enable SSH, further configuration is needed by the administrator.

More details about the new features and improvements are available in the Google Open Source Blog and the protocol documentation.

Requirements

From the client side, git v2.18.0 or newer must be installed.

From the server side, if we want to configure SSH we need to set the sshd server to accept the GIT_PROTOCOL environment.

In installations using GitLab Helm Charts and All-in-one Docker image, the SSH service is already configured to accept the GIT_PROTOCOL environment. Users need not do anything more.

For Omnibus GitLab and installations from source, update the SSH configuration of your server manually by adding this line to the /etc/ssh/sshd_config file: 

AcceptEnv GIT_PROTOCOL

Once configured, restart the SSH daemon for the change to take effect: 

# CentOS 6 / RHEL 6
sudo service sshd restart

# All other supported distributions
sudo systemctl restart ssh

Instructions

In order to use the new protocol, clients need to either pass the configuration -c protocol.version=2 to the Git command, or set it globally: 

git config --global protocol.version 2

HTTP connections

Verify Git v2 is used by the client: 

GIT_TRACE_CURL=1 git -c protocol.version=2 ls-remote https://your-gitlab-instance.com/group/repo.git 2>&1 | grep Git-Protocol

You should see that the Git-Protocol header is sent: 

16:29:44.577888 http.c:657              => Send header: Git-Protocol: version=2

Verify Git v2 is used by the server: 

GIT_TRACE_PACKET=1 git -c protocol.version=2 ls-remote https://your-gitlab-instance.com/group/repo.git 2>&1 | head

Example response using Git protocol v2: 

$ GIT_TRACE_PACKET=1 git -c protocol.version=2 ls-remote https://your-gitlab-instance.com/group/repo.git 2>&1 | head
10:42:50.574485 pkt-line.c:80           packet:          git< # service=git-upload-pack
10:42:50.574653 pkt-line.c:80           packet:          git< 0000
10:42:50.574673 pkt-line.c:80           packet:          git< version 2
10:42:50.574679 pkt-line.c:80           packet:          git< agent=git/2.18.1
10:42:50.574684 pkt-line.c:80           packet:          git< ls-refs
10:42:50.574688 pkt-line.c:80           packet:          git< fetch=shallow
10:42:50.574693 pkt-line.c:80           packet:          git< server-option
10:42:50.574697 pkt-line.c:80           packet:          git< 0000
10:42:50.574817 pkt-line.c:80           packet:          git< version 2
10:42:50.575308 pkt-line.c:80           packet:          git< agent=git/2.18.1

SSH Connections

Verify Git v2 is used by the client: 

GIT_SSH_COMMAND="ssh -v" git -c protocol.version=2 ls-remote ssh://git@your-gitlab-instance.com/group/repo.git 2>&1 |grep GIT_PROTOCOL

You should see that the GIT_PROTOCOL environment variable is sent: 

debug1: Sending env GIT_PROTOCOL = version=2

For the server side, you can use the same examples from HTTP, changing the URL to use SSH.

Observe Git protocol version of connections

To observe what Git protocol versions are being used in a production environment, you can use the following Prometheus query: 

sum(rate(gitaly_git_protocol_requests_total[1m])) by (grpc_method,git_protocol,grpc_service)

You can view what Git protocol versions are being used on GitLab.com at https://dashboards.gitlab.com/d/pqlQq0xik/git-protocol-versions.