[SRU][Trusty][PATCH 0/2] fix "hw csum failure" errors

[Luis Henriques]

On Thu, Jan 15, 2015 at 06:04:06PM -0800, Jay Vosburgh wrote:
> 
> BugLink: https://bugs.launchpad.net/bugs/1409123
> 
> SRU Justification
> 
> Impact: Certain network topologies using VXLAN with certain network
> cards will experience "hw csum failure" errors in the kernel log
> 
> 	"Certain network toplogies" is VXLAN tunneled network between
> two containers or VMs on separate hosts.
> 
> 	"Certain network cards" are at least enic and sky2.  This
> probably includes any other device that performs CHECKSUM_COMPLETE
> receive checksum offload.
> 
> Fix: backport the following two commits from current net-next
> 
> commit 17e96834fd35997ca7cdfbf15413bcd5a36ad448
> Author: Govindarajulu Varadarajan <_govind at gmx.com>
> Date:   Thu Dec 18 15:58:42 2014 +0530
> 
>     enic: fix rx skb checksum
> 
> commit 2c26d34bbcc0b3f30385d5587aa232289e2eed8e
> Author: Jay Vosburgh <jay.vosburgh at canonical.com>
> Date:   Fri Dec 19 15:32:00 2014 -0800
> 
>     net/core: Handle csum for CHECKSUM_COMPLETE VXLAN forwarding
>

Thank you Jay.  These 2 patches have already been queued for the
stable kernels 3.16.y-ckt and 3.13.y-ckt, which means they will soon
be included in Utopic and Trusty kernels.

Cheers,
--
Luís

> Testcase:
> 
> [ 4297.761899] eth0: hw csum failure
> [...]
> [ 4297.765223] Call Trace:
> [ 4297.765224]  <IRQ>  [<ffffffff8172f026>] dump_stack+0x46/0x58
> [ 4297.765235]  [<ffffffff8162ba52>] netdev_rx_csum_fault+0x42/0x50
> [ 4297.765238]  [<ffffffff8161c1a0>] ? skb_push+0x40/0x40
> [ 4297.765240]  [<ffffffff8162325c>] __skb_checksum_complete+0xbc/0xd0
> [ 4297.765243]  [<ffffffff8168c602>] tcp_v4_rcv+0x2e2/0x950
> [ 4297.765246]  [<ffffffff81666ca0>] ? ip_rcv_finish+0x360/0x360
> 
> 	These are reliably reproduced in a network topology of:
> 
> container:eth0 == host(OVS VXLAN on VLAN) == bond0 == eth0 (sky2) -> switch
> 
> 	When VXLAN encapsulated traffic is received from a similarly
> configured peer, the above warning is generated in the receive processing
> of the encapsulated packet.  Note that the warning is associated with the
> container eth0.
> 
> 
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