OpenSSH 4.2p1 over IPv6 results in TCP checksum error

J. K. Cliburn jcliburn at
Tue Dec 20 01:11:19 UTC 2005

On 12/19/05, Daniel Roesen <dr at> wrote:
> On Tue, Nov 08, 2005 at 07:54:34AM -0600, Jay Cliburn wrote:
> > Has anyone successfully used the standard FC4 x86_64 RPM version of ssh (
> > v4.2p1) to connect over IPv6? My attempts result in a TCP checksum error
> > when the client sends the ssh protocol assertion.
> Did you solve this problem? If so, what was the cause? If not, are you
> using an Intel Gigabit Ethernet NIC (e1000)?

Ah yes...  Fond memories of pulling my hair out late at night,
whistling down empty holes, unanswered cries for help in the IPv6

Turned out to be a kernel module bug for my via-velocity gigabit
ethernet NIC.   The VIA Velocity 6122 gigabit chip doesn't support
offloaded TCP checksumming under IPv6, but the via-velocity driver
distributed with Fedora doesn't make any provision for that -- it
assumes offloaded TCP checksumming is always appropriate, no matter
the protocol.

I filed a bug over at bugzilla.


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