jail_git="fc00::168:13"
jail_net="192.168.0.1/24"
# ...
nat on $ext_if inet from $jail_net to any -> $ext_if:0
nat on $ext_if inet6 from $jail_git to any -> $ext_if:0
rdr pass on $ext_if proto tcp from any to ($ext_if) port 9418 -> 192.168.0.13 port 9418
rdr pass on $ext_if inet6 proto tcp from any to ($ext_if) port 9418 -> $jail_git port 9418