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

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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