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

On Fri, Jan 10, 2014 at 09:37:33AM +0100, Fabien Thomas wrote:
> 
> Le 10 janv. 2014 ? 02:21, Yonghyeon PYUN <pyunyh_at_gmail.com> a ?crit :
> 
> > On Thu, Jan 09, 2014 at 04:06:09PM +0100, Alexandre Martins wrote:
> >> Dear,
> >> 
> >> I experience some troubles with the igb device driver on FreeBSD 10-RC4.
> >> 
> >> The kernel make a pagefault in the igb_tx_ctx_setup function when accessing to 
> >> a IPv6 header.
> >> 
> >> The network configuration is the following:
> >> - box acting as an IPv6 router
> >> - one interface with an IPv6 (igb0)
> >> - another interface with a vlan, and IPv6 on it (vlan0 on igb1)
> >> 
> >> Vlan Hardware tagging is set on both interfaces.
> >> 
> >> The packet that cause the crash come from igb0 and go to vlan0.
> >> 
> >> After investigation, i see that the mbuf is split in two. The first one carry 
> >> the ethernet header, the second, the IPv6 header and data payload.
> >> 
> >> The split is due to the "m_copy" done in ip6_forward, that make the mbuf not 
> >> writable and the "M_PREPEND" in ether_output that insert the new mbuf before 
> >> the original one.
> >> 
> >> The kernel crashes only if the newly allocated mbuf is at the end of a memory 
> >> page, and no page is available after this one. So, it's extremly rare.
> >> 
> >> I inserted a "KASSERT" into the function (see attached patch) to check this 
> >> behavior, and it raises on every IPv6 forwarded packet to the vlan. The 
> >> problem disapear if i remove hardware tagging.
> >> 
> >> In the commit 256200, i see that pullups has been removed. May it be related ?
> >> 
> > 
> > I think I introduced the header parsing code to meet controller
> > requirement in em(4) and Jack borrowed that code in the past but it
> > seems it was removed in r256200.  It seems igb_tx_ctx_setup()
> > assumes it can access ethernet/IP/TCP/UDP headers in the first mbuf
> > of the chain.
> > This looks wrong to me.
> 
> Instead of patching each driver with pullup code we can add a generic pullup code ?
> - get the contiguous protocol requirement (L2, L3, L4) from underlying driver.
> - do the pullup
> 

I believe Andre already planned that and he would be working on
removing home-grown header parser implemented in drivers.

> > 
> >> Can you confirm the problem ?
> >> 
> > 
> > Probably Jack can tell more about change made in r256200.  It's not
> > easy for me to verify correctness of igb(4) at this moment.
> > 
> >> Best regards
> >> 
> >> -- 
> >> Alexandre Martins
> >> NETASQ -- We secure IT
>