[syslinux] pxelinux implementation questions

[Alexander Sack]

First off, thank you for the responses.  I have some follow questions.

> > 1)  Why does pxelinux create UDP packets from scratch instead of use the
> > Intel PXE TFTP OPEN/CLOSE/READ calls?  I'm assuming this is to support
> > TFTP options like tsize right?  Did earlier versions of pxelinux use the
> > TFTP calls directly?
> > 
> 
> Because they're largely useless.  They have too many limitations -- only 
> one transaction at one time, must go into contiguous memory, and they 
> will write to the screen and read from the keyboard (there are ways 
> you're *supposed* to be able to override that, but they frequently don't 
> work.)

What do you mean by it "must go into contiguous memory"?  What happens
if you change the buffer address on the fly?  It won't work?

> > 2)  How big of an image can pxelinux download (minus memory constraints)?  
> > My understanding is that tftp packet numbers are from 0-65535 yielding a 
> > maximum size of 32MB.  Yet, from the revision history, it seems pxelinux 
> > can handle bigger images?  (I don't see any wrap around handling though
> > I maybe not looking hard enough in seachdir() - from the looks of it,
> > the only way I can see pxelinux downloading a bigger image is if the
> > tftp_blksize is negotiated greater than 512, right?)
> 
> Nope.  After FFFF follows 0000.

Okay, then can pxelinux handle initrd's bigger than 32MB?  

I remember in the archives you stating that it can handle bigger images
minus kernel initrd bugs (external to pxelinux):

http://www.zytor.com/pipermail/syslinux/2002-January/000008.html

Is this still true?  From the code, it looks like you will handle
different block sizes other than 512 if negotiated.  That would allow
initrd's greater than 32MB right?

> > 3)  Why does pxelinux require tsize?  Does it make a difference what
> > size the file is as long as the last packet returns < 512?
> 
> PXELINUX wants to know the size of the file before it downloads it.

Okay, I wasn't criticizing pxelinux, I am just trying to
understand why add the extra overhead and pervent other tftp dameons
from working with pxelinux?  That's all!  :-)!

Thanks!

-aps

-- 
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