Subject: Re: [Bugme-new] [Bug 16529] New: xennet driver crashes when using with pseudowire aka l2tpv3

From: Jeremy Fitzhardinge <[email-masked]>
Date: Wed, 25 Aug 2010 15:56:12 -0700

On 08/25/2010 03:31 PM, Andrew Morton wrote:
> (switched to email.  Please respond via emailed reply-to-all, not via the
> bugzilla web interface).
>
> On Fri, 6 Aug 2010 12:46:18 GMT
> [email-masked] wrote:
>
>> https://bugzilla.kernel.org/show_bug.cgi?id=16529
>>
>>            Summary: xennet driver crashes when using with pseudowire aka
>>                     l2tpv3
>>            Product: Networking
>>            Version: 2.5
>>     Kernel Version: 2.6.35
>>           Platform: All
>>         OS/Version: Linux
>>               Tree: Mainline
>>             Status: NEW
>>           Severity: normal
>>           Priority: P1
>>          Component: Other
>>         AssignedTo: [email-masked]
>>         ReportedBy: [email-masked]
>>         Regression: No
>>
>>
>> I tried to use use the new l2tpv3 implementation on two xen domU's but one of
>> them is crashing when the first l2tpv3 packet is received.
>>
>> As a great man mentioned: 
>> --
>> guessing that eth_type_trans() has tried to pull an ethernet header from
>> the skb and has run off the end, which suggests an issue with the skb
>> that was passed up. Does the ethernet driver do proper alignment of data
>> in its skbs? Perhaps it doesn't allocate as much headroom as other
>> drivers? Perhaps the L2TP code assumes things about the skb that aren't
>> valid..
>> --
>> Here is a link for the setup
>> http://www.pastebin.org/445975
>> and here a link with more details about the crash http://pastebin.org/449221

Please attach these to the bug or something; pastebin is not working for
me at the moment.

>> According the the hints from James Chapmann we tried generic x86 with a
>> different nic driver like e1000 and this works without any problem. 
>>
>> Iam using OpenWrt to create the system images. To speed up the process i would
>> prepare Xen images, make them available or whatever is wished because
>> pseudowire is already ready in OpenWrt Trunk so that every man also with "price
>> sensitivy" hardware can use it.
>>
> Seems to be a problem with xennet afacit?

Possibly.  What's a l2tpv3 and what does it do differently from other
protocols?

    J