ipv6 activity causing system hang in kernel 2.4.4

[Tim Haynes]

[I can't see evidence of this being reported before; apols if I'm
 wrong. Please also Cc: me as I only read l-k intermittently but would
 like to help out more.]

Hi,

I've been making very tentative forays into IPv6. However, in my simple
experiments thus far I appear to have located a bug:

1/ configure 2 machines with site-local IP#s - I'm using 
ifconfig eth0 inet6 add fec0:1234:5:6::n 
2/ flood-ping from one to the other
3/ after about 15s, watch one box hang, needing magic-sysreq or hard reset

This is only with kernel 2.4.4; 2.4.2, 2.4.3 and NetBSD boxes are not
affected. It is independent of platform; I've reproduced it at will on a
lowly p75, an athlon, a p3-800 and on a powerbook/PPC.

All kernels are compiled to have ipv6 modular, netfilter modular...
everything with which I'm playing, modular.

Compiler versions:
| zsh, 12:06AM % gcc -v
| Reading specs from /usr/lib/gcc-lib/powerpc-linux/2.95.4/specs
| gcc version 2.95.4 20010319 (Debian prerelease)
| zsh, 12:06AM % gcc -v
| Reading specs from /usr/lib/gcc-lib/i386-linux/2.95.4/specs
| gcc version 2.95.4 20010319 (Debian prerelease)
(I'm tracking Debian/Unstable here.)

I have tcpdump logs ( - they're 570K
apiece); the `victim' machine receives nothing but ping-requests and sends
nothing but ping-replies until the file is truncated; the surviving box
sends nothing but requests and receives nothing but replies until it
becomes requests-only. (IOW there is no evidence of ARP, fragmentation
traffic, only the pings.)

The Changelog lists an `IPv6 packet re-assembly fix' in -pre2; my
suspicions lie in this area or with my compiler.

If there's anything else I can provide by way of diagnostics, please let me
know.

Cheers,

~Tim
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Re: Kernel Panic Linux 2.4.3 RH7

[Tim Haynes]

<[EMAIL PROTECTED]> writes:

> Machine has been locking up between 0-3 times a day sporadically. Nothing
> predictable about it. Hadn't locked up for 3 days, and locked 3x today,
> the last 2 times within 20 minutes of each other. Had run stable with
> 2.2.18, and was running fairly stable on 2.4.3 up until about last week.
> (might be coincidence, or not, but seems to happen when I am on IRC --
> DOS?, nothing in log files or firewall logs however)
> 
> Machine info:
> 
> RedHat 7, Intel Celeron 450, 256Meg ECC PC100 DRAM, 1 15G IDE (/usr,
> /tmp, /home, /var, swap ), 1 2G SCSI (/, /boot, swap) HDD, 2 identical
> tulip chipset eth cards.
[snip]
> 
> Mismatch in TCPACCEPT IN=ETH0 OUT= MAC= 00:00:e8:24:53
[snip]
> (stack information skipped, if you need it let me know and I will write it
> all down the next time)
> 
> Process: swapper (pid0, stack page c02dl000)
[snip]

Take your pick from one or more of the following:
a) dodgy RAM - less likely if a different set of RAM has also had
   the problem;
b) a faulty network card - a tulip (Netgear FA310TX) reliably caused me
   a hang ~6 months ago, so there is a precedent;
c) overheating - see if, left to its own devices, the hangs become
   more frequent the longer the box is left on; also implement
   lm_sensors and keep an eye on the CPU temperature if possible;
d) RH7 alert: did you use kgcc to build the kernel?
e) Something totally else :8)

HTH,

~Tim
-- 
   10:32pm  up 3 days, 46 min, 10 users,  load average: 0.18, 0.10, 0.08
[EMAIL PROTECTED] |Clouds cross the black moonlight,
http://piglet.is.dreaming.org |Rushing on down to the sound 
  |of a turning world   
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Re: Ideas for the oom problem

[Tim Haynes]

On Wed, Mar 28, 2001 at 06:33:04PM -0500, Hacksaw wrote:

> > Anyone working as root is (sorry) an idiot! root's processes are normally
> > quite system-relevant and so they should never be killed, if we can avoid 
> > it.
> 
> The real world intrudes. Root sometimes needs to look at documentation,
> which, these days is often available as html. Sometimes it's only as html.
> And people in a panic who aren't trained sys-admins aren't going to remember
> to log in as someone else.

Why are they logged in as root in the first place? Is there something they
can't do over sudo?
I definitely remember seeing a document saying `if you find yourself needing to
`man foo', do it in another terminal as your non-root self'; it might or might
not've been the SAG.

In any case, what happened to `if you use this rope you will hang yourself'?
There has to be a point where you abandon catering for all kinds of fool and
get on with writing something useful, I think.

> I completely agree that doing general work as root is a bad idea. I do most
> root things via sudo. It sure would be nice if all the big dists supplied it
> (Hey, RedHat! You listening?) as part of their normal set.

RH have been listening since v7.0.

~Tim
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