ssh - Disconnecting: Corrupted MAC on input.

[Scott J. Henson]

jd list wrote:
> Hi.  I've had dapper drake installed for a few weeks now (dell
> dimension 8600 1GB RAM, 2.8Ghz proc) and has been working great.  Have
> to use it alot to RDP into my windows work machine, using SSH and port
> forwarding, which also worked fine...until today.
> 
> I decided to test out the ipsec client from ncp.de, and while i was
> connecting into my work machine, only over SSH, to get the key
> information for my VPN client, i got an error "Disconnecting:
> Corrupted MAC on input".  I metion this client because this worked
> perfectly well before I installed it.
> 
> Have since tried to uninstall the ncp client and reboot but to no
> avail still get the same error.  I can stay ssh'd into a terminal for
> about 10 minutes, but when using tsclient to RDP its almost immediate.
> 
> Any thoughts on a solution would be greatly appreciated.  Is there
> anyway in ubuntu to simply reinstall all the network drivers...was
> kind of hoping something like that would fix it.  I've recently gotten
> the install just were i need it so i never have to boot into
> windows...and would like to avoid a reinstall.
> 

The Corrupted MAC is a checksum.  Its a little more accurate 
than the standard TCP checksums.  We see this sometimes on 
machines with ethernet cards that are going bad.  Were you 
trying to connect over the vpn?

As for reinstalling your network drivers, its:

apt-get install --reinstall linux-image-`uname -r`

Though I'm not sure that will solve your problem.  You'll 
probably have to reboot to make sure its reloaded.

 From rereading what you said it would seem as though the 
ncp client installs a kernel module of some sort that is 
hooking into the tcp layer and screwing with stuff.  Youll 
have to rmmod it and keep it from loading(delete it from the 
file system?).  You can find it with lsmod and it should 
live somewhere in /lib/modules/`uname -r`/kernel/. 
Reinstalling the kernel as above won't get ride of any 
modules laying around, as dpkg won't delete stuff it doesn't 
know about.  You can probably find the name of the module in 
ncp's documentation.  I would recommend starting there.