ipfw2/dummynet set new mss on thy fly

Thomas Vogt turbo23 at gmx.net
Fri Feb 6 16:24:17 PST 2004


Is it possible to modify the mss with ipfw2/dummynet? This is necessary 
to fix wrong window implementations for example for adsl providers.

Something like "modify mss=1452 tcp from any to any out recv em0 xmit 
em1 tcpflags syn". (Of course this string is wrong, it's just to give 
you an impression).

I know there is tcpmssd port but it uses divert. I've to modify every 
packet on gigabit lan (at least 200mb/s traffic). So tcpmssd is a bit to 

We already have a ipfw1 patch and It's not that difficult to port it to 
ipfw2. But I'm not sure if ipfw2/dummynet already have something similar 
implemented by default.
Any hints?


More information about the freebsd-ipfw mailing list