My BeagleBone Black is connected via USB to my Linux laptop (Ubuntu 17.10). The BBB is able to connect to the Internet via my laptop forwarding traffic through the WiFi interface.
BBB <-- USB --> Laptop <-- WiFi --> Internet
I got this working 6 months ago but had a really hard time recreating those steps yesterday. I’ve noted what I did in this GitHub Gist in case it helps anyone else (and myself in the future 
https://gist.github.com/pdp7/d2711b5ff1fbb000240bd8337b859412