Introduce VPN support.

This change sets up the basic routing rules for VPNs. It doesn't yet handle UID
ranges (that are meant to apply to the VPN) correctly. That's forthcoming in
other CLs.

Bug: 15409918
Change-Id: I284de04f176dcf6ba702361de6a614266256d04e
8 files changed
tree: 05690f59e4158475a99fe9220191c3282c9f0981
  1. client/
  2. include/
  3. server/