TCP traffic in ipip tunnel inside wireguard connection

[Jason A. Donenfeld]

Hi Ivan,

I'll try to reproduce in order to determine whether or not there's a
checksum bug with nested tunnels. However, all of this seems quite
unnecessary:

Just set allowed-ips to be your /30 for each peer. If you need one to
be 0.0.0.0/0 at one time or another, you can change these at runtime.
Alternatively, if you _must_ have multiple 0.0.0.0/0 just use two
different wireguard interfaces running on different UDP ports, and
then you'll have the full power of the ordinary linux routing table
for this sort of craziness.

Jason