Directories: oskit/boot/ofwboot
Target: ofwboot
Documentation: none
Original Code Source:
	Flux Research Group, University of Utah.
	Derived from PXE boot loader (oskit/boot/pxe).
Description:

Like oskit/boot/pxe, this is a simple first-stage boot loader which
speaks ``bootinfo'', a custom UDP protocol, to a remote server to determine
what to boot next.  ofwboot is intended to be loaded via TFTP directly
from the OpenFirmware; i.e., it is the boot file specified in the BOOTP
or DHCP configuration file.  As such, it should be ``wrapped'' using the
mkofwimage utility.  The ofwboot.image target in the Makefile does this.

ofwboot works by issuing an OpenFirmware boot command with the bootinfo-
provided kernel and command line as the bootspec argument.  Hence, the
kernel specified via bootinfo itself needs to be a mkofwimage-wrapped
OSKit kernel, or other kernel which knows how to interact with OpenFirmware
(e.g., a NetBSD or ARM/Linux kernel).

Once the ofwboot kernel is running, it will query our own little bootinfo
server to find out what to do next.  The protocol is very simple, sending
a UDP packet to a port defined in oskit/boot/bootwhat.h, which returns a
packet. How you implement that server is up to you, but as a trivial example
of how to get started, see oskit/boot/pxe/bootinfo/bootinfo.c.

Notes

* Requires a BOOTP (or DHCP) server to acquire its host information.

* Uses a simple UDP/IP implementation which doesn't support IP fragmentation.

* This program should be extended to boot multiboot-complient kernels
  directly (i.e., by loading and jumping to them) rather than by rebooting
  the machine.