If a community uses different vpn providers, they typically
assume the same MTU for the wan device underneath the VPN. As
different VPN providers however have different overhead, the MTU
of the VPN device differs for each provider. Therefore this
commit makes the MTU of the VPN device provider specific.
This has two advantages:
1. The same site.conf can used to bake firmwares for different
VPN providers (only by selecting a diferent vpn feature in the
site.mk).
2. We are coming closer to the option of integrating multiple VPN
providers into one firmware.
The address of the vpn interface is calculated in the style of
modified EUI-64, based on a virtual mac address. This virtual mac
address consists of 0x00 as first byte and the other five bytes
are taken from the first bytes of md5sum(base64 encoded public key).
The algorithm was taken by the ffmuc, with a slight difference. ffmuc
calculated the result of md5sum(base64 encoded public key + '\n')
which was interpreted as accidential fault and therefore dropped.
Example:
- Public-Key: "gP3VJnTTvnQut+z4O+m0N9RgMyXbgyUbUkF3E3TKX2w="
- Address: "fe80::02ca:b8ff:fedc:2eb3"
The following interfaces are used for wireguard:
- wg_mesh -> wireguard interface
- mesh-vpn -> vxlan iface on top of wg_mesh
If you use this new feature, make sure the NTP servers in your site
config are publicly reachable. This is necessary, since wireguard
requires correct time before the vpn connection is established.
Therefore gluon performs ntp time synchronisation via WAN before it
establishes the vpn connection. Therefore the NTP servers have to
be publicly reachable (and not only via mesh).
