An iPEX menu for openwrt box with extension support

openwrt.ipxe

#!ipxe
# dhcp

set advanced-server 192.168.9.9
set advanced-menu tftp://${advanced-server}/main.ipxe

# Some menu defaults
set menu-timeout 10000
set submenu-timeout ${menu-timeout}
set menu-default ubuntu1804_live

:start
menu iPXE boot menu
item --key b    other                   Others
item --gap --                   ---------------------------- Installers ----------------------------------
item --key u    ubuntu1804_inst         Install Ubuntu 18.04 (AMD64)
item --key d    debian10_inst           Install Debian 10 (AMD64)
item --gap --                   ------------------------- Advanced options -------------------------------
item --key s    shell                   Drop to iPXE shell
item            reboot                  Reboot
item
item --key x    exit                    Exit iPXE and continue BIOS boot
choose --timeout ${menu-timeout} --default ${menu-default} selected || goto cancel
set menu-timeout 0
goto ${selected}

:cancel
echo You cancelled the menu, dropping you to a shell

:shell
echo Type 'exit' to get the back to the menu
shell
set menu-timeout 0
set submenu-timeout 0
goto start

:reboot
reboot

:exit
exit

###
### Custom menu entries
###

:other
set prev-server ${next-server}
set next-server ${advanced-server}
kernel ${advanced-menu}
boot
set next-server ${prev-server}
goto start

:ubuntu1804_inst                                                                                                                                                                                                                             kernel http://archive.ubuntu.com/ubuntu/dists/bionic-updates/main/installer-amd64/current/images/netboot/ubuntu-installer/amd64/linux                                                                                                        initrd http://archive.ubuntu.com/ubuntu/dists/bionic-updates/main/installer-amd64/current/images/netboot/ubuntu-installer/amd64/initrd.gz                                                                                                    boot                                                                                                                                                                                                                                         goto start                                                                                                                                                                                                                                   
:debian10_inst
kernel http://ftp.debian.org/debian/dists/stable/main/installer-amd64/current/images/netboot/debian-installer/amd64/linux
initrd http://ftp.debian.org/debian/dists/stable/main/installer-amd64/current/images/netboot/debian-installer/amd64/initrd.gz
boot
goto start