Strangeness with ipconfig

[Michael Prokop]

* Alex Meyer <alex at thefind.com> [Mon Apr 05, 2010 at 05:03:34PM -0700]:

> Unfortunately, I'm running into difficulty.  It seems that the
> transition to using debian live has led to a problem in my situation.
> In my case, the problem is a very long hang waiting for a DHCP response.

> This is actually the third round of DHCP.  First is PXE from the BIOS,
> then it appears that the kernel does DHCP right before 'Freeing unused
> kernel memory'.  Finally, after 'Running /scripts/live-premount'
> finishes, a userspace DHCP attempt is made, but it hangs for many minutes.

> I've been fishing around in the initrd trying to debug this.  I think
> I've found a workaround, but it pains me to think about the implications.

> Basically, to debug what was going on, I copied the 'strace' binary into
> the initrd.  Then, I changed scripts/live around line 707 to this:

>   strace -f ipconfig ${DEVICE} | tee /netboot.config

> I was hoping to see a clue as to what was going wrong.  I already knew
> from tcpdump that the DHCP server was receiving the requests and sending
> replies.  Instead, I saw everything working perfectly with no hangs.
> So, as a hack, I changed the line to:

>   strace -o /dev/null ipconfig ${DEVICE} | tee /netboot.config

> And now everything works as it should.  Of course, now I need a
> custom-mangled initrd.  And now I wonder what this ipconfig binary is

The ipconfig binary is an ELF executable from klibc-utils
(/usr/lib/klibc/bin/ipconfig).

> and why it's so unreliable for me.  I assume that running it in strace
> changes some aspects of timing and/or memory layout, thereby avoiding a
> bug in it.

> When I take out the strace, it goes back to not working.  The DHCP
> server sends the responses and usually gets an ICMP port unreachable
> packet for UDP port 68.  This leads me to believe that ipconfig doesn't
> properly set up its networking when run outside of strace.

> My environment is i386.  The target machine is a recent two-core Intel box.

> Can anyone help me get things working without this hack?

Can you please provide us the output of:

  dpkg --list initramfs-tools live-initramfs klibc-utils

from the system you're trying to boot?
Which kernel version are you using?

To start further debugging: does using

  http://deb.grml.org/pool/main/l/live-initramfs/live-initramfs_1.177.1-1grml.03_all.deb
  http://deb.grml.org/pool/main/i/initramfs-tools/initramfs-tools_0.93.4-grml02_all.deb

and/or the grml-kernel help? Instructions available at:

  http://faiwiki.informatik.uni-koeln.de/index.php/Grml_Kernel

(notice that kernel 2.6.33-grml[64] is available already.)

regards,
-mika-
-- 
http://michael-prokop.at/  || http://adminzen.org/
http://grml-solutions.com/ || http://grml.org/
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