Add ability to set MAC address of adapter

[Antoine-Gicquel]

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Description

It would be nice to make use of qemu's ability to set the mac address of a netdev. I think it would involve adding parameters in builder/qemu/step_run.go, and should be pretty straightforward. I currently am not skilled enough in Go / not familiar enough with the internals of Packer to feel confident about implementing this feature myself, but I would be pleased to help or to be guided at low level (like telling me which files to change precisely etc).

Use Case(s)

I would need it in order to control which IP address is given to the guest VM on a bridge (using dnsmasq for DHCP).

Potential configuration

source "qemu" "example" {
...
net_bridge = "virbr0"
net_mac = "00:00:00:00:00:00"
...
}

Potential References

Qemu documentation on setting a mac address with -netdev and -device ?

[Antoine-Gicquel]

For now, I found a hacky workaround, setting net_device like so :
net_device = "virtio-net,mac=00:00:00:00:00:00"

It uses builder/qemu/step_run.go, line 252, to inject the argument in the qemu-system command.