Re: Mopd which works with ELF and a.out in Linux and can netboot ULTRIX

["Maciej W. Rozycki" <macro%linux-mips.org@localhost>]

On Wed, 28 Oct 2020, David Brownlee wrote:

> > > I've committed the pfInit and 1k/4k changes.
> > > One quick question on the mid 0 change - should the N_BADMAG (ex) &&
> > > N_BADMAG (ex_swap)) check be conditionalised on mid 0?
> >
> > I don't think the N_BADMAG (ex) check should be conditional, because it
> > seems all a.out files should have magic numbers there, which are the
> > same across different operating systems. Anyways, if some foreign a.out
> > files used different magic numbers, mopd couldn't tell if the file is
> > OMAGIC or NMAGIC, which could cause problems. So it seems best to reject
> > such files.
> 
> Ah, yes, now I actually read the code, that makes more sense :)

 For the record: some 20 years ago I was in a need for a usable `mopd' 
daemon under Linux, so I grabbed whatever sources were available, cleaned 
some stuff up, added proper packet socket level (data link layer level) 
multicast support (no need for allmulti or promiscuous operation), added 
FDDI support, i.e. SNAP frame essentially (so that I could boot my 
DECstations over DEFZA and DEFTA interfaces, which do support it), and 
finally added ELF support so that I didn't have to go through hoops to 
boot ELF images.

 I continue using this stuff to this day (most recently earlier this 
month), although there are a couple shortcomings, most notably if an 
interface `mopd' listens on goes down then the daemon dies and has to be 
restarted (I guess a socket error isn't handled correctly; proper event 
handling would have to be added for interfaces going down and up, so that 
multicast group membership is correctly maintained over the interfaces 
listened on, which is all by default).

 Regrettably I was unable to find any package maintainer or proper 
upstream sources, so my patches were never submitted anywhere, but I 
packaged them into the RPM format (one of the two major Linux package 
formats) in the source and a couple of binary forms and published on my 
FTP site, in addition to loose patches.  This stuff is still online, so if 
anyone is interested, please feel free to have a look at:

<ftp://ftp.linux-mips.org/pub/linux/mips/people/macro/mopd/>

 I'll be happy to have this stuff upstreamed too even now after those 20 
years if there's still something missing from whatever `mopd' sources are 
considered the reference these days.

  Maciej