Steps to share internet with BeagleBone Black using USB from OS X - networking

Question

Already tried:
Connect the BBB with USB to iMac
Share internet with the board from System Preferences->Sharing
ssh to the board and then try to udhcp -i usb0
This is what it says:
udhcpc (v1.20.2) started
Gets stuck and I get and error: Write failed: Broken pipe
ssh exits
Any clues?

Answer 1

After some try-and-erroring, here's what worked for me:
1. Watch this video: http://www.youtube.com/watch?v=Cf9hnscbSK8
2. If your BBB was shipped after November 2013, instead of screen /dev/tty.usb*B 115200 use screen /dev/tty.usb* 115200 and actually you need to go to the /dev directory and check which of the tty.usbXXX is available for your BBB and screen it. In my case it was tty.usb131 for example
3. You continue the steps just like in the video until opkg update which would be the thing you need to do over the internet
And that it's all about it.

Answer 2

Your SSH session is getting stuck because you're connected to usb0 and the udhcpc command changed the IP address for it! At this point there's nothing listening on the other end of your ssh session, so your local computer's ssh client eventually fails with the broken pipe error and exits.
An obvious workaround is to connect via tty.usbserial instead of ssh to the IP address. You'd think the usb port's assigned IP shouldn't be changing though. Read on to understand what's happening.
Most people using a BBB for the first time attach them directly to their Internet connected computer using the supplied USB cable. It's exactly what the BBBs designers intended for you to do, and they've done a fantastic job with the BBBs startup web page.
That host computer shares it connection differently though depending on whether it's Windows, OS X or Linux, and how you do it varies depending on the version of the OS you're running.
Derek Molloy (Exploring BeagleBone) and Jason Kridner (Youtube OS X Beaglebone video) provide some fairly detailed instructions to use host based Internet sharing with your BBB. The Linux and Windows instructions are still good, but they need to update the OS X info for Yosemite - Apple switched their NAT and firewall software to pf from ipfw and natd. If you try running udhcpc like Jason did in his vid it doesn't work the same way as his did.
So back to your BBB SSH problem with OS X Yosemite. Here's how to see what's going on: Connect to the BBB using a serial/FTDI cable, then check the ip config of usb0 for the beaglebone.
beaglebone:~# ifconfig -a usb0
usb0 Link encap:Ethernet HWaddr 0e:be:ff:00:ff:00 inet addr:192.168.7.2
Bcast:192.168.7.3 Mask:255.255.255.252
confirm you can ping the host that's sharing it's Internet connection
beaglebone:~# ping 192.168.7.1
PING 192.168.7.1 (192.168.7.1) 56(84) bytes of data.
64 bytes from 192.168.7.1: icmp_req=1 ttl=64 time=0.681 ms
64 bytes from 192.168.7.1: icmp_req=2 ttl=64 time=0.533 ms
^C
try reaching an Internet IP (google dns)
beaglebone:~# ping 8.8.8.8
connect: Network is unreachable
check routes and confirm there's no default route out, which is why the ping above failed (a USB connected BBB has a 192.168.7.0/30 network setup by default, so it can only reach 192.168.7.0, .1, .2 and .3 addresses).
beaglebone:~# netstat -rn
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
192.168.7.0 0.0.0.0 255.255.255.252 U 0 0 0 usb0
so if you run udhcpc it will add the missing route for you. you could also just add the route directly, but you need to setup dns as well, and with OS X Internet sharing it won't work without also changing the BBB's IP address - see links at end of this post)
beaglebone:~# udhcpc -i usb0
udhcpc (v1.20.2) started
Sending discover...
Sending discover...
and here is where udhcpc changes the IP instead of just re-using 192.168.7.2. The new IP is compatible with the IP range used by OS X Internet Sharing, so that may be why the DHCP server is returning it.
Sending select for 192.168.2.34...
Lease of 192.168.2.34 obtained, lease time 85536
udhcpc then throws an error because there's no default route to delete
/etc/udhcpc/default.script: Resetting default routes
SIOCDELRT: No such process
udhcpc then adds the default route - note carefully it's an OS X Internet Sharing 192.168.2 address, not the original 192.168.7.
/etc/udhcpc/default.script: Adding DNS 192.168.2.1
everything worked, so you can see the new route and successfully ping an external IP now
beaglebone:~# netstat -rn
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
0.0.0.0 192.168.2.1 0.0.0.0 UG 0 0 0 usb0
192.168.2.0 0.0.0.0 255.255.255.0 U 0 0 0 usb0
beaglebone:~# ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_req=1 ttl=53 time=4.08 ms
64 bytes from 8.8.8.8: icmp_req=2 ttl=53 time=3.59 ms
^C
There are a couple of blog posts that show how to set this up permanently:
Sharing OS X Internet Connection over USB to BeagleBone Black
and
Changing usb0 IP address on the BeagleBone Black