sshd consuming 100% of cpu

I am having real problems with sshd on one of my machines. Some of the
connections have sshd on the server running at max cpu rate(99% CPU)
I am running of DEBUG3 and the last thing sshd reports is
Jun 11 18:55:01 info sshd[31269]: debug3: Normalising mapped IPv4 in IPv6 address

After that it is 99% CPU and totally ceasing communication witht eh remote
client. Furthermore, if I do an strace of that running IP and get nothing
coming out. Ie, it seems to have gone into an internal loop.
That IPV6 seems to be common to all(?) of the situations.

If I do lsof sometimes the socket is recognized as an IP connection
eg
sshd 31058 root 3u IPv6 2200693 TCP info.physics.ubc.ca:ssh->modemcable226.220-203-24.mc.videotron.ca:58268
(CLOSE_WAIT)

and sometimes the socket protocol is not recognized.

This is running openssh-4.7p1-9.1mdv on a 2007.0 Mandriva system, but this
problem occured to start with openssh-server-4.5p1-0.3mdv.

It also occurs only on one machine. The other machines seem to have no
trouble.

Any hints as to how to track this down?

On Wed, 11 Jun 2008 22:32:17 -0400, Unruh <unruh-(E-Mail Removed)> wrote:

> That IPV6 seems to be common to all(?) of the situations.

I'd try disabling ipv6. Add
IPV6INIT=no
IPV6TO4INIT=no
to all ifcfg-$interface files in /etc/sysconfig/network-scripts and add
alias net-pf-10 off
to /etc/modprobe.conf

Regards, Dave Hodgins

--
Change nomail.afraid.org to ody.ca to reply by email.
(nomail.afraid.org has been set up specifically for
use in usenet. Feel free to use it yourself.)

On Thu, 12 Jun 2008 02:32:17 +0000, Unruh wrote:

> I am having real problems with sshd on one of my machines. Some of the
> connections have sshd on the server running at max cpu rate(99% CPU) I
> am running of DEBUG3 and the last thing sshd reports is Jun 11 18:55:01
> info sshd[31269]: debug3: Normalising mapped IPv4 in IPv6 address
>
> After that it is 99% CPU and totally ceasing communication witht eh
> remote client. Furthermore, if I do an strace of that running IP and get
> nothing coming out. Ie, it seems to have gone into an internal loop.
> That IPV6 seems to be common to all(?) of the situations.
>
> If I do lsof sometimes the socket is recognized as an IP connection eg
> sshd 31058 root 3u IPv6 2200693 TCP
> info.physics.ubc.ca:ssh->modemcable226.220-203-24.mc.videotron.ca:58268
> (CLOSE_WAIT)
>
> and sometimes the socket protocol is not recognized.
>
>

you can ssh from a machine back into itself. i dont know why the daemon
itself would be hitting 99% though. Maybe sshd is starting some
subprocess to help with something. is top or whatever showing all the
children of that process?