Invalid handshake initiation after peer reboot: bug?

[Jason A. Donenfeld]

Hi Eicke,

It could be a customer's network is mangling packets or something,
though that seems least likely. More probably, if you're dealing with
tiny devices, might it be that they don't have a real time clock
battery? WireGuard relies on a timestamp counter always moving
forward. It doesn't have to be accurate, but it just can't move
backwards. So you might try syncing your OpenWRT router to some
network time server of sorts before initiating a WireGuard handshake.

Jason