Problem creating a bond in active backup mode on Virtual Functions on Intel X710 network controller

["Pandey, Utkarsh" <Utkarsh.Pandey@hughes.com>]

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Hello,
We have two X710 network interfaces (physical functions) PF1 and PF2 and creating one virtual functions (VF) on each of them (say VF1 and VF2 respectively).
We are creating a bond between the two VFs (VF1 and VF2 belonging to PF1 and PF2 respectively), in active-backup mode using EAL arguments and assigning a bond mac address.
Initially VF1 is the primary slave and VF2 is the backup.
We have been successful in using this bond interface to send and receive packets.

However, when we test for redundancy, we are running into a problem described as follows:
1. Initially the bond interface is able to send network packets using the primary slave.
2. The primary slave (VF1) is brought down by bringing down the physical functions (PF1) corresponding to the primary slave.
3. The backup VF (VF2) becomes the primary slave and the bond interface continues to transmit packets.
4. Some time later, the original primary slave (VF1) is re-enabled and the current slave (VF2) is brought down.
5. The primary slave for the bond interface changes back to the initial interface (VF1). However, at this point, the packet transmission stops.

Experiment Details:
1. DPDK 21.05 is used.
2. The physical functions are bound to i40e driver and the virtual functions are bound to the vfio-pci driver.
3. The VFs were not assigned a MAC address through the PF manually.
4. Trust mode was set to "On" for both the VFs.

A similar experiment performed on the Physical Function does not show this issue and the primary slave switches back and forth as the interfaces are disabled and re-enabled.

Is it possible to create a bond on Virtual Functions in the active-backup mode?

Thanks,
Utkarsh Pandey.

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