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DPU Gateway Interface Configuration

Overview

In DPU (Data Processing Unit) host mode deployments, OVN-Kubernetes supports automatic gateway interface resolution from PCI address. This feature is particularly useful when the management port is a Virtual Function (VF) and you want to automatically select the corresponding Physical Function (PF) interface as the gateway.

Background

In DPU deployments, the host typically has access to Virtual Functions (VFs) for management purposes, while the Physical Functions (PFs) are used for external connectivity. The "derive-from-mgmt-port" feature allows OVN-Kubernetes to automatically discover and configure the appropriate PF interface as the gateway interface based on the VF used for the management port.

How It Works

When configured with --gateway-interface=derive-from-mgmt-port, OVN-Kubernetes performs the following steps:

  1. Management Port Resolution: Gets the management port network device name (specified by --ovnkube-node-mgmt-port-netdev)
  2. VF PCI Address Retrieval: Retrieves the PCI address of the management port device (VF)
  3. PF PCI Address Resolution: Gets the Physical Function (PF) PCI address from the Virtual Function (VF) PCI address
  4. Network Device Discovery: Retrieves all network devices associated with the PF PCI address
  5. Interface Selection: Selects the first available network device as the gateway interface

Configuration

Command Line Options

--ovnkube-node-mode=dpu-host
--ovnkube-node-mgmt-port-netdev=pf0vf0
--gateway-interface=derive-from-mgmt-port

Configuration File

[OvnKubeNode]
mode=dpu-host
mgmt-port-netdev=pf0vf0

[Gateway]
interface=derive-from-mgmt-port

Helm Configuration

ovnkube-node:
  mode: dpu-host
  mgmtPortNetdev: pf0vf0

gateway:
  interface: derive-from-mgmt-port

Example Scenario

Consider a DPU setup with the following configuration:

  • Management port device: pf0vf0 (Virtual Function)
  • VF PCI address: 0000:01:02.3
  • PF PCI address: 0000:01:00.0
  • Available PF interfaces: eth0, eth1

With --gateway-interface=derive-from-mgmt-port, OVN-Kubernetes will:

  1. Start with the management port device pf0vf0
  2. Get its PCI address 0000:01:02.3
  3. Resolve the PF PCI address to 0000:01:00.0
  4. Find all network devices associated with PF 0000:01:00.0: eth0, eth1
  5. Select eth0 (first device) as the gateway interface

Requirements

Hardware Requirements

  • SR-IOV capable network interface card
  • Virtual Function (VF) and Physical Function (PF) setup
  • Management port configured as a VF

Software Requirements

  • SR-IOV utilities available on the system
  • OVN-Kubernetes running in DPU host mode
  • Proper VF/PF driver support

Configuration Requirements

  • Must be used in DPU host mode (--ovnkube-node-mode=dpu-host)
  • Management port netdev must be specified (--ovnkube-node-mgmt-port-netdev)
  • Gateway interface must be set to derive-from-mgmt-port

Error Handling

The system will return an error in the following scenarios:

No Network Devices Found

no netdevs found for pci address 0000:01:00.0

Cause: The PF PCI address doesn't have any associated network devices.

Resolution: Verify that the PF has network interfaces configured and are visible to the system.

PCI Address Resolution Failure

failed to get PCI address

Cause: Unable to retrieve the PCI address from the management port device.

Resolution: Ensure the management port device exists and is properly configured.

PF PCI Address Resolution Failure

failed to get PF PCI address

Cause: Unable to resolve the PF PCI address from the VF PCI address.

Resolution: Verify SR-IOV configuration and driver support.

Network Device Discovery Failure

failed to get network devices

Cause: Unable to retrieve network devices associated with the PF PCI address.

Resolution: Check SR-IOV utilities and system configuration.

Troubleshooting

Verify SR-IOV Configuration

# Check if SR-IOV is enabled
lspci | grep -i ethernet

# Check VF configuration
ip link show

# Check PF/VF relationship
ls /sys/bus/pci/devices/*/virtfn*

Verify Management Port Device

# Check if management port device exists
ip link show pf0vf0

# Check PCI address
ethtool -i pf0vf0 | grep bus-info

Debug PCI Address Resolution

# Get VF PCI address
cat /sys/class/net/pf0vf0/device/address

# Get PF PCI address (if available)
cat /sys/class/net/pf0vf0/device/physfn/address

Integration with Existing Features

Gateway Accelerated Interface

The "derive-from-mgmt-port" feature is used in conjunction with management interface to select the appropriate gateway accelerated interface.

The management port can be specified through one of the following options: 

  --ovnkube-node-mgmt-port-netdev)
    OVNKUBE_NODE_MGMT_PORT_NETDEV=$VALUE


  --ovnkube-node-mgmt-port-dp-resource-name)
    OVNKUBE_NODE_MGMT_PORT_DP_RESOURCE_NAME=$VALUE

OVNKUBE_NODE_MGMT_PORT_DP_RESOURCE_NAME has priority over OVNKUBE_NODE_MGMT_PORT_NETDEV and it is easier to use since it points to a SRIOV Device Plugin pool name.

Multiple Network Support

This feature works with multiple network support and can be used in environments where pods have multiple interfaces connected to different networks.

Limitations

  • Only available in DPU host mode
  • Requires SR-IOV capable hardware
  • Limited to the first available network device from the PF
  • Depends on proper VF/PF driver support
  • May not work with all SR-IOV implementations

Future Enhancements

Potential improvements to this feature could include:

  • Support for selecting specific network devices based on criteria
  • Integration with device plugin resources
  • Support for multiple gateway interfaces
  • Enhanced error reporting and diagnostics
  • Support for non-SR-IOV hardware configurations