Debian - Hamachi taking over default IP routing
I've been using Hamachi on a BeagleBone Black as it's a great way to make a small portable device externally accessible. Specifically I'm using the latest ARM Beta version, logmein-hamachi_2.1.0.203-1_armhf.deb.
With hamachi running, its IP routing entries (via route command) are simply:
25.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 ham0 link-local 0.0.0.0 255.255.0.0 U 0 0 0 ham0
On a few occasions though I have had it add an additional route show up:
default 0.0.0.0 0.0.0.0 U 0 0 0 ham0
This supersedes the default internet route out the devices Ethernet connection, making it go to the Hamachi connection instead which isn't providing internet access (only a mesh network between devices). By trying to put internet communication through the Hamachi network all internet access fails, including to Hamachi servers, and so the device drops from the Hamachi network and has to be fixed by manually adding the default Ethernet route back in (route add default gw [gateway_port] eth0).
This looks like an odd bug in the current beta version. I'm not familiar enough with Linux routing to understand if there's a way I can stop this from happening, so for now I've just made a workaround script to remake my internet route if Hamachi tries to take over.
I think I may have discovered the source of the problem, which was connman that was managing networks on my device. In some cases after a power cycle of a larger system, the BeagleBone could finish restarting faster than the device that was providing its ethernet connectivity to the internet. connman would see no ethernet available, then try and set up Hamachi as the main internet source instead. It wouldn't switch back to ethernet once it was available.
The solution was to edit the file /etc/connman/main.conf and add Hamachi's 'ham0' interface to the list of interfaces connman would ignore.
