[syslinux] PXELINUX gets stuck when receiving non-PXE traffic

Michael Stapelberg michael+syslinux at stapelberg.ch
Thu Jul 18 10:30:02 PDT 2019

Hi hpa, Ady,

hpa at zytor.com (H. Peter Anvin) writes:

> On 6/6/19 8:16 AM, Ady Ady via Syslinux wrote:
>>> the PXELINUX log line is
>>> printed (PXELINUX 6.04 lwIP 6.04-pre3 Copyright (C) 1994-2015 H. Peter
>>> Anvin et al),
>> (snip)
>> FWIW, the official binaries from 6.04-pre2 and 6.04-pre3 are not good 
>> for troubleshooting.
>> 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


Best regards,

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