pxelinux chain to iPXE no more network devices

[mimiko]

After digging into the problem I've found that the problem is the missing driver in ipxe.krn for the Atheros AR8131 rev.C network card (1969:1063).
So until a driver for this card will be available in ipxe with the help of robinsmidsrod in IRC a workaround is to load first undionly.kpxe, chain to pxelinux.0 and call gpxecmd.c32 to get back to ipxe and load the stuff.
Eample:
dhcpd.conf contains:
if exists user-class and option user-class = "iPXE" { filename "/undionly.ipxe"; } else { filename "undionly.kpxe"; }

/undionly.ipxe contains:
#!ipxe
ifopen
chain tftp://${next-server}/pxelinux.0

pxelinux.cfg/default contains:
LABEL Shell
KERNEL gpxecmd.c32
append imgfree pxelinux.0 && shell

LABEL Windows Recovery Enviroment
KERNEL gpxecmd.c32
append imgfree pxelinux.0 && kernel http://tftp.ex.com/x86/wimboot && initrd http://tftp.ex.com/x86/bcd BCD && initrd http://tftp.ex.com/x86/boot.sdi boot.sdi && initrd http://tftp.ex.comx64/winre-win_7_x86.wim boot.wim && boot

LABEL Abort
KERNEL gpxecmd.c32
append exit

LABEL MemTest
KERNEL gpxecmd.c32
append imgfree pxelinux.0 && chain http://tftp.ex.com/tools/memtest/memtest.0 || reboot



Keep in mind that `append` command in pxelinux.cfg/default must definatly be in lower case, otherwise it want work and menu will be shown again.