Re: LRO disable warnings on kernel 2.6.38

[Eric Dumazet <eric.dumazet@gmail.com>]

Le lundi 21 mars 2011 à 10:21 +0100, Jesper Dangaard Brouer a écrit :
> On Fri, 2011-03-18 at 09:18 -0700, Alexander Duyck wrote:
> > On 3/18/2011 4:12 AM, Jesper Dangaard Brouer wrote:
> > > Hi
> > >
> > > I'm seeing the LRO disable warnings using kernel 2.6.38:
> [...]
> > >
> > The error doesn't make any sense for igb to be triggering since it 
> > doesn't support setting the NETIF_F_LRO flag in the 2.6.38 kernel.
> > 
> > By any chance are there any ixgbe or other interfaces in the system?  I 
> > would suspect the error to come from a driver that at least contains the 
> > NETIF_F_LRO flag.
> 
> The servers actually also have a four port semi-build in NIC (its a PCIe
> slot with an extra connector, most likely for controlling the LEDs).  I
> don't use that NIC as it (1) caused kernel panics on 2.6.35, (2) needs a
> firmware blob, (3) reading through the driver code (at some point in
> time) they didn't implement multiqueue support correctly.
> 
> So lets blame that driver ;-)
> 
> lspci-info:
>  Ethernet controller: NetXen Incorporated NX3031 Multifunction 1/10-Gigabit Server Adapter (rev 42)
> 
> driver info via ethtool:
> # ethtool -i eth01
>  driver: netxen_nic
>  version: 4.0.75
>  firmware-version: 4.0.530
>  bus-info: 0000:06:00.3
> 
> The strange part is that my pre-prod server also have a netxen_nic, but
> it does not result in a WARN being tricked... 
> 
> The pre-prod server do have a different firmware version.
> # ethtool -i eth01
>  driver: netxen_nic
>  version: 4.0.75
>  firmware-version: 4.0.406
>  bus-info: 0000:06:00.0
> 
> (I have pulled the NIC out of some of the prod server, due to the risk
> of a kernel panic on the old kernel.  As operations have taken over the
> deployment process, these NICs are still in.  Guess I'll ask them to
> blacklist the driver, so they don't see the warn stacktrace, they get so
> nervous when they see stuff like that ;-))
> 

Well, this warning can be ignored since these NIC dont receive packets
to be forwarded in your setup.

I would say netxen_nic_set_flags() is buggy : It rejects data if other
flag than ETH_FLAG_LRO is set.

if (data & ~ETH_FLAG_LRO)
	return -EINVAL;

Brought by commit ef2519b1dd39940 (netxen: fail when try to setup
unsupported features) later corrected by commit 97d1935a61b7fe7a65f98f
(Make ethtool_ops::set_flags() return -EINVAL for unsupported flags)

Since this drivers asserts NETIF_F_HW_VLAN_TX (mirroring
ETH_FLAG_TXVLAN), ethtool_op_get_flags() can return more than
ETH_FLAG_LRO.

dev_disable_lro() then calls netxen_nic_set_flags() with ETH_FLAG_TXVLAN
-> -EINVAL, and ETH_FLAG_LRO stay ORed in dev->features -> WARNING