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

[Jay Vosburgh]

Andy Whitcroft <apw at canonical.com> wrote:

>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
>
>Actually these are both in mainline now, as of v3.19-rc3.
>
>> 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
>
>Both seems to be trivial backports from those originals, and as such
>seem acceptable.  Depending on the severity of the symtoms, it is not
>clear to me if these are just annoying traces or data is being lost at
>the same time, we could take these in advance of them going to -stable.
>Also these probabally should go to -stable :).  I think davem handles
>this differently to everyone else of course, so they may be in plan for
>-stable already.

	The ultimate impact is that (a) traffic to a VM or container
ends up being checksummed in software, and (b) the kernel dmesg fills up
with big scary-looking stack traces.

	Yes, I'll be submitting a -stable request to netdev.  I just got
verification from the customer that the patches fix the problem and I
did the SRU first to get that rolling.

>Overall:
>
>Acked-by: Andy Whitcroft <apw at canonical.com>
>
>-apw

[... combining replies ...]
>And while I am thinking about it, if this is needed on Trusty, I assume
>that Utopic and the lts-backport thereof are also affected?  I assume we
>should be patching there too?  Again hopefully this will come out via
>stable.  I've nominated the bug to the various packages and series that
>seem relevant, and marked it up for commit tracking (so if they come in
>via stable it will also get closed out).

	Yes, the later releases should also need the patches, but there
is no rush there.

	-J

---
	-Jay Vosburgh, jay.vosburgh at canonical.com