Syslinux - Nov 2013 - IPMI serial over lan disconnects seem to trigger extlinux reboots

Hi,

I hope somebody can help me with this problem.  I don't know whether
it's a problem with my configuration or a bug or feature in extlinux.
I am using an IPMI 2.0 serial-over-lan console to connect to a system
with an Intel S3200SHL motherboard.  The first line of my extlinux.conf
file looks like this:
   serial 0 57600 0x003
I am using ipmitool to access the console, like so:
   ipmitool -f /etc/ipmi.passwd -U <user> -I lanplus -H <host> sol
activate

I just converted this system from grub 0.97 to extlinux 4.05.  The IPMI BMC
software on this system is pretty flaky.  The IPMI serial-over-lan session
disconnects frequently, particularly during the boot process.  After converting
to extlinux, it looks to me as if the extlinux loader reboots the system
whenever the IPMI serial console disconnects.  This often happens while
extlinux is loading the kernel or the initrd.  As a result, it can reboot
itself many times before it gets lucky and makes it far enough to hand off
control to the kernel.  Once the kernel takes over, there is no problem -- it
doesn't mind the disconnects.

This problem did not occur with grub.  My question is whether there is some
serial flag configuration that would tell extlinux to ignore the disconnects,
or would it require a patch to the software to achieve that?
It is not obvious to me from reading the description of the serial flag
values whether I could somehow fix the problem that way.  I tried searching
the source code, but I was unable to find the relevant bits.

Does anybody know how to solve this problem?

Thanks,
Andy

On 11/11/2013 05:38 PM, Andrew J. Schorr wrote:
> Hi,
> 
> I hope somebody can help me with this problem.  I don't know whether
> it's a problem with my configuration or a bug or feature in extlinux.
> I am using an IPMI 2.0 serial-over-lan console to connect to a system
> with an Intel S3200SHL motherboard.  The first line of my extlinux.conf
> file looks like this:
>    serial 0 57600 0x003
> I am using ipmitool to access the console, like so:
>    ipmitool -f /etc/ipmi.passwd -U <user> -I lanplus -H <host>
sol activate
> 
> I just converted this system from grub 0.97 to extlinux 4.05.  The IPMI BMC
> software on this system is pretty flaky.  The IPMI serial-over-lan session
> disconnects frequently, particularly during the boot process.  After
converting
> to extlinux, it looks to me as if the extlinux loader reboots the system
> whenever the IPMI serial console disconnects.  This often happens while
> extlinux is loading the kernel or the initrd.  As a result, it can reboot
> itself many times before it gets lucky and makes it far enough to hand off
> control to the kernel.  Once the kernel takes over, there is no problem --
it
> doesn't mind the disconnects.
> 
> This problem did not occur with grub.  My question is whether there is some
> serial flag configuration that would tell extlinux to ignore the
disconnects,
> or would it require a patch to the software to achieve that?
> It is not obvious to me from reading the description of the serial flag
> values whether I could somehow fix the problem that way.  I tried searching
> the source code, but I was unable to find the relevant bits.
> 
> Does anybody know how to solve this problem?
> 
There is no reason by Syslinux would reboot the system on a serial
disconnect.  There could be a bug, of course; now, Syslinux 4.05 is
pretty old so unless you can reproduce this on a current version that
would be useful.

The other option is that there is something in the IPMI BC that causes
the reboots which happens on Syslinux and not Grub for some reason.

You may want to turn serial interrupts on (serial 0 57600 0x00b) and see
if that makes any difference.

	-hpa

Hi,

Thanks for your help.

On Mon, Nov 11, 2013 at 08:00:47PM -0800, H. Peter Anvin
wrote:
> There is no reason by Syslinux would reboot the system on a serial
> disconnect.  There could be a bug, of course; now, Syslinux 4.05 is
> pretty old so unless you can reproduce this on a current version that
> would be useful.
I am using 4.05 because that's what's packaged in the latest Fedora
release (Fedora 19 in my case).  I wonder why they are using such an
old version.  I will take a look at how difficult it would be to build
the latest version on Fedora.
> The other option is that there is something in the IPMI BC that causes
> the reboots which happens on Syslinux and not Grub for some reason.
That could well be the case.  I am just speculating about the cause.  I really
do not know what is going wrong.  There is some kind of bad interaction
occurring during the load of the initramfs.  If I disable the IPMI serial
console session, the system boots fine.  So it must be some strange interaction
between the IPMI BMC and Syslinux.  
> You may want to turn serial interrupts on (serial 0 57600 0x00b) and see
> if that makes any difference.
I tried that, but it did not help.  The system still tends to reboot while
loading the initramfs.

Thanks,
Andy