lkl: add lkl_if_set_mac to support set MAC address on the interface

[clingfei]

Currently, we can only set the MAC address when using lkl_netdev_add to add a new network device. Otherwise, it will generate a random one through eth_hw_addr_random.

It would be more flexible to support dynamically MAC address configuration.

[tavip]

LGTM, thanks @clingfei !

[clingfei]

Thanks for your review @tavip!

The previous commit caused checkpatch.sh to fail, and I have fixed this issue in the latest commit.

[thehajime]

thanks @clingfei for the patch.

I was wondering if we can change an interface created with dpdk device, which has a configuration to the underlying part.

https://github.com/lkl/linux/blob/master/tools/lkl/lib/virtio_net_dpdk.c#L452

[clingfei]

I was wondering if we can change an interface created with dpdk device, which has a configuration to the underlying part.

https://github.com/lkl/linux/blob/master/tools/lkl/lib/virtio_net_dpdk.c#L452

Currently, we can only change the LKL guest interface, not the DPDK device. If we want to change the interface for the backend, maybe we should add a set_mac for lkl_dev_net_ops and call some DPDK setter function.

Moreover, in the current DPDK config path, the auto-detected DPDK MAC takes precedence over iface->ifmac_str because config.c checks the DPDK-filled mac buffer before parsing the configured MAC. I think this also supports modifying only the guest interface without affecting the DPDK device interface.