This program read xl2tpd log file and show status icon in system tray.
To compile it name file main.cpp and execute command in terminal.

    g++ `pkg-config --cflags --libs gtk+-2.0` main.cpp -o xl2tpd-tray-icon

then copy xl2tpd-tray-icon to directory /usr/bin

then copy 4 image files (connect.png, disconnect.png, online.png, offline.png)
to directory /usr/share/xl2tpd-tray-icon

then make file /etc/xdg/autostart/xl2tpd-tray-icon.desktop with content

    [Desktop Entry]
    Name=xl2tpd-tray-icon
    Exec=xl2tpd-tray-icon
    Terminal=false
    Type=Application
    X-GNOME-Autostart-enabled=true

after reboot program will start automatically.

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Images are from Openclipart (Creative Commons Zero 1.0 Public Domain License)
and Pixabay (Free for commerical use. No attribution required)

https://openclipart.org/detail/198745/mono-tool-offline-mode-off
https://openclipart.org/detail/198746/mono-tool-offline-mode-on
https://pixabay.com/en/connection-broken-network-98523/
https://pixabay.com/en/network-computer-workstations-lan-98522/