[5.2.1-RC, IPFW] Traffic Shaping

[Jaco van Tonder]

Hi all,

I am using FreeBSD 5.2.1-RC + IPFW2 + DUMMYNET to do traffic shaping.
This works well for my setup.
I have the following configuration:
The machine has 2 NIC's, xl0, dc0. The kernel is configured to do 
bridging. The bridged
packets is passed to IPFW (net.link.ether.bridge.ipfw=1).

I shape traffic this way:
The bridge is setup between a router and an internal mail server.
I am limiting bandwith using the following rules:
pipe 1 config bw 16KBytes/s
pipe 2 config bw 12KBytes/s

and then:

add pipe 1 tcp from any to any 25  (limit incoming traffic towards smtp)
add pipe 2 tcp from any 110 to any (limit outgoing traffic from pop3)

Yesterday, while browsing through Absolute BSD by Michael Lucas I read 
an interesting part:
You cannot shape incoming traffic the way that I do at the moment.

Now, my question:
How can I limit the incoming traffic towards my smtp server properly?

Any advice would be apreciated.

Thank you,
Regards
Jaco van Tonder