Port mirroring - pfsense in Proxmox

[MH5Dx]

Hi,

I installed pfsense in proxmox and redirect all the traffic "coming from proxmox/internet" to an interface called vmbr1 on the WAN side of pfsense.

I would like to install Security Onion IDS (in a VM under proxmox) in the "LAN" part of pfsense and monitor vmbr1 traffic.

On my point of view, I need to get a span port (or similar) on vmbr1, sending this traffic copy to an interface on the LAN side of my pfsense in order to be read by Security Onion VM.

Nevertheless, at the moment, I don't know how to do that. Any idea?

Of course, there should be Dup-to but not so well documented if not wrong...
Also, should be possible eventually with IPtables mantrap but not so nice also...

A process inside pfsense would be welcome.
I supposed to create a span interface on WAN side and then copy again traffic to an interface on LAN ?

Thanks in advance for your attention and answer.