[Click] Kernel NULL pointer dereference when forwarding packets

[George Ioannidis]

Hello,

I am trying to run a simple Click kernel module which captures all
packets from interface *gbe0* and forwards them to the interface *gbe1*;
these are 10 Gigabit Intel Network cards.

My issue is that I get a NULL pointer dereference when I forward
packets, even with a very simple configuration.

Setup of *host A*:

    *Click version*: 2.1 (latest from github), kernel module

    *Configuration*: FromDevice(gbe0, PROMISC true) -> Queue(10000) ->
    ToDevice(gbe1);

    *kernel*: 3.2.0-39-generic x86_64 GNU/Linux.
    *Distro*: Ubuntu 12.04.2 LTS

    *Ethernet card*: [detailed in the *attachment*]
    84:00.1 Ethernet controller: Intel Corporation 82599EB 10-Gigabit
    SFI/SFP+ Network Connection (rev 01)
            Subsystem: Intel Corporation Ethernet Server Adapter X520-2
            Kernel driver in use: ixgbe
            Kernel modules: ixgbe


*Test*: another machine, host B, is connected directly to host A.
Userspace click also runs on *host B* with the following configuration:

    RandomSource( LENGTH 1514 ) -> ToDevice(gbe0);

So, the simple packet flow should be the following: Host_B [gbe0] ->
Host_A [gbe0] -> Host_A [gbe1]

*Kernel panic* produced at host A, 10-20 seconds after the experiment
starts: [full log in the *attachment*]

    [ 1907.823186] BUG: unable to handle kernel NULL pointer dereference
    at 0000000000000040
    [ 1907.870136] IP: [<ffffffffa00f8b84>]
    ixgbe_xmit_frame_ring+0x54/0x390 [ixgbe]

For 10-20 seconds, the experiment runs and packets are indeed forwarded
from gbe0 -> gbe1.

Do you have any ideas about what the problem could be?

Best Regards,
George
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