Re: Using network informations from PXE as grub2 enviroment variables

[Seth Goldberg]

Quoting Vladimir 'phcoder' Serbinenko, who wrote the following on Fri, 16...:

> Seth Goldberg wrote:
> > Hi,
> >
> > Quoting Pavel Pisa, who wrote the following on Fri, 16 Oct 2009:
> >
> > > > > Nobody can't use options 150 from DHCP, because GRUB2 don't have any
> > > > > driver for network adapters. Network task are done only through
> > > > > adapters PXE firmware. PXE passes informations only about IP
> > > > > addresses, but no DHCP options.
> >
> >   Not true -- all DHCP options are available by inspecting the cached
> > DHCPACK that is available from a call to PXE firmware.  This is a
> > stable interface and works quite well.  In fact, we enhanced the
> > Legacy GRUB we use in Solaris to pass the entire DHCPACK via the
> > multiboot structure (albeit in a non-standard way -- and I'd like to
> > rectify that by including the DHCPACK in the multiboot structure
> > explicitly) so it can be used by the kernel.
> Since you are familiar with networking and PXE could you make a
> multiboot amendment proposal? It has to be
> (a) expandable to new network interfaces (not only PXE), it includes the
> necessity of passing info pertatining to multiple adapters and a way to
> match this info to adapters (I think MAC is good for this)
> (b) possibility to add custom information, not only what is specified by
> DHCP standard. Vendor info encapsulation is perhaps a way. I'm not sure
> we'll ever need this but I would like to have this possibility if we
> ever need it

 We'll need a flag bit indicating the presence of network boot information. 
After that, define a field that's a pointer to a structure of the form:

struct netbootinfo {
        int     type;   /* 0 = PXE; 1 = RARP/BOOTP */
        void    *data;  /* Pointer to the boot-protocol-specific data */
                        /* In the PXE case, that's a DHCPACK frame; */
                        /* In the RARP/BOOTP case, it's a BOOTP reply */

        struct netbootinfo *next;       /* Link to next netbootinfo structure */
};

  I know you don't like linked lists/pointers in the multiboot structure, so 
we can specify an array of these structures, but that's a bit inefficient (and 
embedding a union of types could waste even more space).

 --S