mac geekery

There are plenty of tips for this on other sites, but I couldn’t get any of them to work. Many were written in the Year of the Jaguar, and Bluetooth has changed much in OS X since those halcyone days. It only took a little toying to get it going, though.

In the Bluetooth prefpane’s sharing tab, make a new Serial Port Service and name it bt-ppp and make it an RS-232 device. Then, create the following script. If it’s on, disable internet sharing in the Sharing prefpane.

The script below starts pppd on the new Bluetooth serial device you’ve created, then sets up IP forwarding, NAT, and the like. The en0 can be replaced with en1 if your primary net connection is AirPort. You can change the IP listed to something appropriate for your network, as well. If you put it in the range of IPs you’re already using for your home network, natd is smart enough to work as a router instead of a gateway. Run as root (for the love of all that is holy and just, use sudo instead of su).

/usr/sbin/pppd /dev/tty.bt-ppp 115200 noauth local passive proxyarp asyncmap 0 silent persist :10.1.1.25 &
/usr/sbin/sysctl -w net.inet.ip.forwarding=1
/usr/sbin/natd -same_ports -use_sockets -log -deny_incoming -interface en0
/sbin/ipfw add divert natd ip from any to any via en0

All that’s left is to configure your handheld (or another computer, really) to pair, connect a PPP session, and don’t use authentication (pairing handles that, for our needs).