Re: FreeBSD 10-RC4: Got crash in igb driver

All,

I work with Jack on FreeBSD network drivers, and we have a patch that we
think might fix this problem. It re-implements the header pull-up code that
was in the driver pre-2.4.0, but with IPv6 support. Alexandre, could you
apply this patch to the igb version in HEAD and try it out on your network?
We can't replicate your setup here.

If it solves your problem, then the next step would be to port the patch to
the ixgbe driver since, as Yonghyeon noted, it looks like that driver will
encounter the same problem. We could then modify em to add IPv6 offload
support as well.

Thanks,

---
- Eric Joyner

On Fri, Jan 10, 2014 at 02:35:29PM +0400, Gleb Smirnoff wrote:
>   Yonghyeon,
>
> On Fri, Jan 10, 2014 at 10:21:14AM +0900, Yonghyeon PYUN wrote:
> Y> > I experience some troubles with the igb device driver on FreeBSD
10-RC4.
> Y> >
> Y> > The kernel make a pagefault in the igb_tx_ctx_setup function when
accessing to
> Y> > a IPv6 header.
> Y> >
> Y> > The network configuration is the following:
> Y> >  - box acting as an IPv6 router
> Y> >  - one interface with an IPv6 (igb0)
> Y> >  - another interface with a vlan, and IPv6 on it (vlan0 on igb1)
> Y> >
> Y> > Vlan Hardware tagging is set on both interfaces.
> Y> >
> Y> > The packet that cause the crash come from igb0 and go to vlan0.
> Y> >
> Y> > After investigation, i see that the mbuf is split in two. The first
one carry
> Y> > the ethernet header, the second, the IPv6 header and data payload.
> Y> >
> Y> > The split is due to the "m_copy" done in ip6_forward, that make the
mbuf not
> Y> > writable and the "M_PREPEND" in ether_output that insert the new
mbuf before
> Y> > the original one.
> Y> >
> Y> > The kernel crashes only if the newly allocated mbuf is at the end of
a memory
> Y> > page, and no page is available after this one. So, it's extremly
rare.
> Y> >
> Y> > I inserted a "KASSERT" into the function (see attached patch) to
check this
> Y> > behavior, and it raises on every IPv6 forwarded packet to the vlan.
The
> Y> > problem disapear if i remove hardware tagging.
> Y> >
> Y> > In the commit 256200, i see that pullups has been removed. May it be
related ?
> Y>
> Y> I think I introduced the header parsing code to meet controller
> Y> requirement in em(4) and Jack borrowed that code in the past but it
> Y> seems it was removed in r256200.  It seems igb_tx_ctx_setup()
> Y> assumes it can access ethernet/IP/TCP/UDP headers in the first mbuf
> Y> of the chain.
> Y> This looks wrong to me.
>
> Can you please restore the important code in head ASAP? Although crashes
happen
> only when the mbuf is last in a page and page isn't mapped, we read
thrash from
> next allocation on almost every packet.
>

It seems other Intel ethernet drivers except em(4) have similar
issues.  I didn't check recent Intel controllers/drivers for long
time so I don't know details on hardware requirements of
offloading.
Since Jack is very responsive and has hardwares to verify, he would
be more appropriate person to handle these issues.
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