Syslinux - Jul 2019 - PXELINUX gets stuck when receiving non-PXE traffic

On 7/18/19 10:30 AM, Michael Stapelberg via Syslinux
wrote:
>>>
>>> Is the same behavior present when testing with other versions? I
would
>>> suggest trying 6.04-pre1, and/or the binaries from Debian Sid / 
>>> Unstable (which are more up-to-date than official upstream
6.04-pre1).
>>> Please note that you need to replace _all_ binaries (e.g. *.c32),
not
>>> just lpxelinux.0, from the same exact build/version/package.
> 
> Thanks for letting me know. I have repeated my tests with 6.04-pre1 and
> Debian unstable?s 3:6.04~git20190206.bf6db5b4+dfsg1-1. Both versions
> exhibit the same problem.
> 
>> Indeed; it would also be a good idea to test both pxelinux.0 and
lpxelinux.0.
>> They access the PXE stack in very different ways, so it is a good idea
to
>> check both.
> 
> I can confirm that using pxelinux.0 instead of lpxelinux.0 does indeed
> work in my setup! I will switch to pxelinux.0 for the time being.
> 
> I tried enabling debug output by using:
> 
> echo 'GCCWARN += -DDEBUG_PORT=0x3f8 -DCORE_DEBUG=1' >>
mk/devel.mk
> 
> ?but unfortunately I don?t see any additional messages on the serial
> console except for the initial message:
> 
> PXELINUX 6.04 lwIP  Copyright (C) 1994-2015 H. Peter Anvin et al
> 
> Do you happen to know off-head what might be wrong here? As a quick
> reminder, the hardware I?m running this on is a
> https://pcengines.ch/apu2c4.htm
> 
Hi,

lpxelinux.0 interacts with the network ROM in a completely different way than
pxelinux.0.  In general, the method used by pxelinux.0 is likely to be *far*
more reliable given the crazy variety of PXE ROMs out there; however, it can
inherently only use UDP and therefore only supports TFTP. For that reason, I
strongly recommend that people use lpxelinux.0 only if you intend to boot from
a non-TFTP protocol (i.e. HTTP or FTP.)

	-hpa

On 7/18/19 6:18 PM, H. Peter Anvin wrote:
> 
> Hi,
> 
> lpxelinux.0 interacts with the network ROM in a completely different way
than
> pxelinux.0.  In general, the method used by pxelinux.0 is likely to be
*far*
> more reliable given the crazy variety of PXE ROMs out there; however, it
can
> inherently only use UDP and therefore only supports TFTP. For that reason,
I
> strongly recommend that people use lpxelinux.0 only if you intend to boot
from
> a non-TFTP protocol (i.e. HTTP or FTP.)
> 
That being said, I have to say I'm surprised that iPXE would have that
problem
(seeing that it apparently uses iPXE as its PXE ROM.)

[Michael: this is with regards to this system:
https://pcengines.ch/apu2c4.htm; it apparently fails with syslinux in UNDI
mode (lpxelinux.0).]

	-hpa

> On 7/18/19 6:18 PM, H. Peter Anvin wrote:
> > 
> > Hi,
> > 
> > lpxelinux.0 interacts with the network ROM in a completely different
> > way than pxelinux.0.  In general, the method used by pxelinux.0 is
> > likely to be *far* more reliable given the crazy variety of PXE ROMs
> > out there; however, it can inherently only use UDP and therefore only
> > supports TFTP. For that reason, I strongly recommend that people use
> > lpxelinux.0 only if you intend to boot from a non-TFTP protocol (i.e.
> > HTTP or FTP.)
> > 
> 
> That being said, I have to say I'm surprised that iPXE would have that
> problem (seeing that it apparently uses iPXE as its PXE ROM.)
> 
> [Michael: this is with regards to this system:
> https://pcengines.ch/apu2c4.htm; it apparently fails with syslinux in
> UNDI mode (lpxelinux.0).]
 
 
IDK why a failure in the the interaction between iPXE and Syslinux 
would be such a surprise.

A reminder (note: "AFAIK, then nothing happened with them" is still 
current, and updating lwip in Syslinux has not been done either, 
AFAICR):

 https://www.syslinux.org/archives/2017-June/025815.html 

Considering that at least 3 of Michael Brown's patches sent to Syslinux 
were effectively ignored, I wouldn't be surprised if he doesn't reply 
to this new email thread (but I hope he does).

Regards,
Ady.