Yes, you're reading this right. I've managed to build iptables.o, ipt_*.o, iptable_filter.o, iptable_nat.o, ip_conntrack.o and the like for my Motorola A780 cellphone.
As of now, there's not really all that much need for it... but when I start running dozens of applications on the device, I better make sure to have a decent packet filter to the GPRS/HSCSD world.
But even then, in theory it should now be possible to NAT between the GPRS device one one side, and the usb-lan on the other side. Maybe I should try to bring my whole home network online via the A780 :)
OTOTH this doesn't fix the various security issues on the horizon. The A780 apparently ships zlib-1.1.3. I don't even know how many security vulnerabilities were fixed since then...