LAVA Hacking Sessions

A LAVA hacking session is a special lava-test-shell test that provides interactive ssh access to a LAVA device inside a defined test environment. This support differs from the normal LAVA SSH protocol support in that the job waits for a real user to log in, instead of using an ssh connection to run a test shell.

Assumptions

  • The user has TCP/IP access to the device (this may require a VPN or other access if firewalls exist between the user and the device).
  • The test job deployment raises a usable networking interface.

Limitations

The session connection is SSH, not serial. This can change the way that certain operations run within the session compared to an automated test job. In particular, the MultiNode API does not operate either within a hacking session or between two hacking sessions. A test definition which runs either before or after the hacking session will be able to use the full MultiNode API.

Device requirements

Some devices may need parameters to configure the network correctly to allow the user to log in to the hacking session. e.g. QEMU jobs need to setup a tap device:

context:
  arch: amd64
  netdevice: tap

Definitions

There are test definitions for hacking sessions provided by the LAVA developers at https://git.linaro.org/lava-team/hacking-session.git . Currently the following definitions are supported:

  • hacking-session-debian.yaml - Run the hacking session on a Debian or Ubuntu filesystem. The package openssh-server will be installed using the package manager if not already installed in the test image. The test image must raise a network interface automatically (this can be done with lava_command_run, see example).
  • hacking-session-fedora.yaml - Run the hacking session on a Fedora filesystem. The package openssh-server will be installed using the package manager if not already installed in the test image. The test image must raise a network interface automatically (this can be done with lava_command_run, see example).
  • hacking-session-oe.yaml - Run the hacking session on an Open Embedded filesystem. openssh-server must be installed in the test image, as it cannot easily be installed afterwards.

Parameters

There are several extra parameters to set when using these test definitions, some optional:

  • PUB_KEY: A plain-text string containing the ssh public key(s) you wish to use when connecting to the device
  • GATEWAY: (optional) The gateway for the network the test device is on. This only needs to be set if the test is unable to determine the gateway correctly - check with your LAVA admins
  • IRC_USER: (optional) IRC nick - this user will be alerted when the hacking session is ready for a connection with a private IRC message containing the details of how to connect to the session. (Debian hacking sessions only.)
  • IRC_SERVER: (optional) The IRC network to use for notifications, used if IRC_USER is also set. This defaults to irc.freenode.net

Starting a Hacking Session

  • Create a test job with your desired target and image
  • Add a lava-test-shell action at the point where you want hacking access:
- test:
      failure_retry: 3
      name: kvm-basic-hacking-session
      timeout:
        minutes: 5
      definitions:
       - repository: https://git.linaro.org/lava-team/hacking-session.git
         from: git
         path: hacking-session-debian.yaml
         name: hacking
         parameters:
            "IRC_USER": "TYPE YOUR IRC NICK HERE"
            "PUB_KEY": "PASTE_PUBKEY(S) HERE"

It is possible to include multiple hacking sessions in the same job, even interleaved with other test actions.

As an alternative to an IRC message like this example, it is also possible to configure notification such that email will be sent when the job starts running. For more information, see User specified notifications.

See also

Hacking Session timeouts and Timeouts for clarification of the timeout support.

Connecting to a Hacking Session

The hacking session test definition will log the ssh command line needed for connection into the LAVA log file. To access the log file, you can use a web browser; navigate to your hacking session and scroll to the end of the job to see this command line, For an example see:

SSH tunnels

If your test device is located on a remote network, you may need to gain access via an ssh tunnel. If so:

  1. verify your SSH key is setup and configured to connect:

    ~# ssh -T username@example.com
    
  2. Modify your SSH config to allow agent forwarding:

    Host example.com
       ForwardAgent yes
    

lava-test-shell helper functions in a hack session

Once logged in to the hacking session, the lava-test-shell helper functions can be found on the test device in the directory /lava/bin

Record text to the LAVA log

During a hacking session, LAVA listens to the primary serial connection for the duration of the hacking session. From within the test device, any text you echo to that serial connection will therefore be recorded within LAVA. You may need to work out the correct device name for this connection, for example by looking at the CONSOLE setting in /proc/cmdline.

As an example, in a QEMU test, the device name will be /dev/ttyS0. From within the hacking session:

root@kvm01:~# echo "This is a test statement" > /dev/ttyS0

will output to the LAVA log like:

This is a test statement

There is an example of this online at https://validation.linaro.org/scheduler/job/116632/log_file#L_5_12

Stopping a Hacking Session

During a hacking session, your test device can’t be used for other tasks. This will block other users who may want to run tests using the device. For that reason, your session is monitored for Hacking Session timeouts, or you can complete your session immediately:

  • Log out of your session (you can avoid closing the session on logout using the Continuing a Hacking Session support).
  • Cancel the job in the LAVA using the link in the job detail or job log pages.
  • Stop - Use the helper function stop_hacking from the command line within the hacking session

Note

Cancel will end the entire job immediately. Use stop_hacking to close the session and complete normal job processing that may be defined after the hacking session.

Hacking Session timeouts

Note

This behaviour changed after a session at Connect HKG15

All hacking sessions will time out after 1 hour if a login has not been detected. If an IRC_USER is specified, another IRC private messages will be sent to that user explaining the termination.

The timer is running for the lifetime of the hacking session, so if you use Continuing a Hacking Session and logout, you will still need to log back in within one hour.

The session will timeout, regardless of activity, when the top-level timeout specified in the job is reached.

This support is separate from the Timeouts handling of the test job.

Continuing a Hacking Session

If you want to be able to log out of a hacking session and log back in within the inactivity timeout, call the continue_hacking script from the command line within the hacking session. The hacking session is still monitored for Hacking Session timeouts, so do remember to log back in.

Multiple hacking sessions

It is possible to use secondary connections to allow more than one person to have a hacking session on a device. Depending on how the test job is designed, it is possible to have two hacking sessions into the same machine or to contain each hacking session within a separate virtual machine. The secondary connection acts exactly as a second root login to the device, so it is up to the test writer to handle possible collisions between the sessions. It is possible to have multiple hacking sessions per person or one hacking session each for multiple users. Secondary connections separate each session as a single node in the MultiNode group.

Note

The MultiNode API does not support the synchronisation or message sending primitives inside hacking sessions. Interactive users are required to exchange information between users in other means, either by using common files on a shared filesystem or other external methods like email or IRC.

Sharing a single device

The basis of a test job to share a device between multiple hacking sessions is the same as any other secondary connection test job on that device, all that changes is the test definition.

If using multiple users on a single device, it will be necessary to create a role for each user in the MultiNode group. This allows a separate test definition for each role, including details of the public SSH key and IRC nick of the user who will be able to use that session. Each hacking session test definition will notify the specified user individually, when that session is ready.

The count specified in the MultiNode group determines how many secondary connections are made using any one role. For one session per user, the count for each role would be one with the number of roles determining the number of users.

Note

Remember: this test job will result in multiple individuals all having a root user login on the device at the same time. Users must co-operate and consider that some tasks (like installing new packages) will prevent other users from doing their tasks at the same time. It is exactly the same as giving multiple people SSH access to a server and giving all those users sudo privileges - the users need to work together.

Separating users using virtual machines

If users are to be separated within virtual machines, one test definition will be responsible for starting each of those machines and this definition will have full control of the QEMU command line for each machine. (It is therefore possible to launch virtual machines of different architectures or configurations for specific purposes.)

Notifying users in this situation is more difficult but the existing support within the standard hacking session can be re-used as it is simply a script being called with parameters from the test job. In particular, the notification will have to allow for declaring the IP address of the virtual machine for each user.

Caution

Separating hacking sessions into virtual machines is a more complex task and requires a lot of setup on the device. Consider if it is really necessary for each user to be on this one device at the same time or whether the separation between users would be better done with separate hacking session test jobs. Remember, users may not be able to share data or files across different virtual machines on one device. This method is not a workaround for a lack of hardware of a particular type of device.

In particular, pay attention to:

  • Identify unique MAC addresses for each virtual machine and check with the lab admins to ensure that these do not clash with any other device on the lab network.
  • Setup the bridging on the device before starting any virtual machines so that the machine will get an IP address which is visible to the user.

Start by creating a test job which can launch multiple virtual machines and identify the IP address of each machine. The exact mechanisms used to obtain this information will vary by use case. The IP address is then passed back to the dispatcher to initiate the secondary connection into the running virtual machine. The hacking session can then start as normal inside that virtual machine.

See also

Delaying the start of a job using Multinode for more information on creating a test job which can delay starting the secondary connections until the first test job has successfully launched the virtual machines.