Administering VLANd support in LAVA

Mandatory Constraints

VLANd is a daemon to support virtual local area networks. It can be used alone and can also be used within LAVA. VLANd is a specialised tool and the LAVA support cannot and will not protect against misconfiguration causing the network to become unusable. Admins require careful consideration of the risks and time to manually prepare a configuration map of the entire LAVA instance, including the physical layout of the switches, all cables connected to all of those switches and all the devices of that instance (not just test devices). These constraints must all be met and can be summarised as:

Single set of switches

All devices and all dispatchers must be on a single set of physical switches. These virtual networks are local, no other topology is supported.

Switches must have drivers in vland

Switches which are expected to support a VLAN must have driver support in VLANd.

Accurate map of network topology

The physical topology of the LAN needs to be manually mapped and translated into the device dictionary of the LAVA instance. This information must be maintained and updated manually whenever the network topology is changed.

The map must be complete and cover the identity of the switches and all the port number(s) for all connections to those switches. It is strongly recommended that administrators use the VLANd administration interface to lock ports for devices that are not expected to be controlled in LAVA tests, such as PDUs and the dispatcher itself. This will ensure that mistakes in test configuration cannot alter connections to those devices which might break the network.

The network map consists of:

  • The identity of the switch and the port to which each interface of each device under test is connected.

  • The MAC address and full sysfs path of the network interface of each supported device. The /sys/ path should not include the current interface name (eth0 etc.) as this can be changed with a different userspace. e.g.

    /sys/devices/platform/ocp/4a100000.ethernet/net/
    
  • The list of unique interface names for network interfaces on the device. This may be something like eth0, eth1, etc., but the names used here will not necessarily match up with the names that show up when the device is actually running due to ordering issues when Linux boots. To remove any possible confusion here, it is therefore recommended to not use the eth0/eth1 names here.

  • The interface tags to describe each interface of each device. See VLANd and interface tags in LAVA. These tags will be useful information for test writers to know, and will be used when selecting devices and interfaces to match test definitions. Useful properties to list here may include things like supported link speeds (100M, 1G, 10G etc.), device manufacturer (Intel, Realtek, etc.), physical interface type (RJ45, SFP, etc.) - whatever test writers are going to care about.

Identification of primary interfaces

Devices may have requirements that booting can only use certain interfaces (which may be considered as primary), e.g. bootloaders may lack the ability to detect and/or use a network interface which uses a USB network converter when a physical ethernet port is also fitted. If the physical ethernet port is put onto a VLAN, the bootloader may be unable to raise a network interface. Test writers need to be able to know which interfaces should be typically be avoided and lab admins can choose different methods for this support. See VLANd and interface tags in LAVA.

  • Not specifying tags for primary interfaces or
  • Specifying only a special tag which test writers should normally avoid using.

The method chosen needs to fit with the Accurate map of network topology and the particular use cases within each lab and LAN. See also Requirement for multiple interfaces.

Additional advice

In addition, the following advice is strongly recommended:

  • Admins should keep the device dictionary data in VCS and keep those copies synchronised with the database.
  • Admins need to use the XML-RPC support to periodically verify that all the devices have the correct configuration.
  • Admins need to ensure that any locked ports are re-established should there be a power outage, maintenance window or other cause of switches being reset or reconfigured.
  • Admins need to record the interfaces which may be considered primary for each device. See Identification of primary interfaces.

These items are an extension of the admin requirements for PDU ports and connection commands and are to be considered in the same way. Any time that any cables are moved around in the physical world, there will need to be a software change, preferably in VCS and also in the database of the LAVA instance.

Example device dictionary

This example uses a non-existent vland.yaml template and imaginary sysfs locations. Real datasets must extend a known template, typically the device type template which itself extends the base template.

{% extends 'vland.yaml' %}
{% set interfaces = ['iface0', 'iface1'] %}
{% set sysfs = {
'iface0': "/sys/devices/pci0000:00/0000:00:19.0/net/",
'iface1': "/sys/devices/pci0000:00/0000:00:1c.1/0000:03:00.0/net/"} %}
{% set mac_addr = {'iface0': "f0:de:f1:46:8c:21", 'iface1': "00:24:d7:9b:c0:8c"} %}
{% set tags = {'iface0': ['1G', '10G'], 'iface1': ['1G']} %}
{% set map = {'iface0': {'switch2': 5}, 'iface1': {'switch1': 7}} %}

This dictionary defines two interfaces belonging to the relevant device. It uses python syntax to map each of those interfaces to values which need to be extracted from the device itself:

  • sysfs: the full path in /sys to the device providing the interface.
  • mac_addr: the MAC address of each interface - if the device is incapable of retaining the same MAC address across power resets, the test writer will need to use the sysfs information to work out which interface is which.
  • tags: tags are used to select which devices of a particular device type can be assigned to the LAVA job. Although the link speed is the most common value to be used, it could also be anything else which differs between otherwise similar devices. See VLANd and interface tags in LAVA. Tags are expressed as a python dictionary of python lists.
  • map: the switch and port map - the IP address or hostname of the switch and the port on that switch from which there is a direct cable to the physical port declared in the sysfs entry.

Viewing the network map

Device information can be viewed using XML-RPC using the system.pipeline_network_map request. The function collates all the vland information from pipeline devices to create a complete map, then return YAML data for all switches or a specified switch.

switches:
  '192.168.0.2':
  - port: 5
    device:
      interface: iface0
      sysfs: "/sys/devices/pci0000:00/0000:00:19.0/net/"
      mac: "f0:de:f1:46:8c:21"
      hostname: bbb1