boringtun: Slow work during testing on VM

Hi 👋

I wanted to add mDNS support for wireguard and decided to take userspace module for it. But during the test I found the strange thing that the bandwidth dropped a lot and the ping increased in boringtun. This does not happen when switching to kernel or Go implementation (just switch WG_QUICK_USERSPACE_IMPLEMENTATION).

The latest version is used as mentioned in the README. This appeared after some time of testing. In the beginning everything was fine. As you can see the CPU is not busy.

vagrant@wgserver:~$ boringtun-cli -V
boringtun 0.6.0

vagrant@wgserver:~$ rustup -V
rustup 1.26.0 (5af9b9484 2023-04-05)
info: This is the version for the rustup toolchain manager, not the rustc compiler.
info: The currently active `rustc` version is `rustc 1.70.0 (90c541806 2023-05-31)`

vagrant@wgserver:~$ hostnamectl
 Static hostname: wgserver
 Pretty hostname: wg_server
       Icon name: computer-vm
         Chassis: vm 🖴
      Machine ID: 794e8af11ca343c3ac86176f4506a03e
         Boot ID: 5c51191b3166487ea3d9dad3aa1ec591
  Virtualization: oracle
Operating System: Ubuntu 23.04
          Kernel: Linux 6.2.0-24-generic
    Architecture: x86-64
 Hardware Vendor: innotek GmbH
  Hardware Model: VirtualBox
Firmware Version: VirtualBox

P.S. Maybe I should also mention in the README that WG_QUICK_USERSPACE_IMPLEMENTATION parameter doesn’t work without fixes because it doesn’t go into basic mode inside if

~ Sergei