This is easy to do with openbsd. You create/modify 6 files and
reboot:

hostname.le0
dhcp NONE NONE NONE

hostname.hme0
inet 192.168.1.1 255.255.255.0

hostname.hme1
up

hostname.hme2
up

hostname.hme3:
up

bridgename.bridge0:
add hme0
add hme1
add hme2
add hme3
up

The IP address is assigned to one nic in the bridge. You do not
assign the IP address to the bridge itself.

PF will still filter the bridge interfaces, and pf.conf can be
confusing when you are trying to block packets for the bridge, so if
you have trouble and have a default block, try putting this in pf.conf
for testing:
pass quick log on { hme0 hme1 hme2 hme3 } keep state

and then monitor with tcpdump -nei pflog0