Re: [PATCH] xen-netfront: Fix handling packets on compound pages with skb_segment

From: David Miller
Date: Sat Aug 02 2014 - 18:33:43 EST


From: Wei Liu <wei.liu2@xxxxxxxxxx>
Date: Fri, 1 Aug 2014 12:02:46 +0100

> On Thu, Jul 31, 2014 at 01:25:20PM -0700, David Miller wrote:
>> If you were to have a 64-slot TX queue, you ought to be able to handle
>> this theoretical 51 slot SKB.
>
> There's two problems:
> 1. IIRC a single page ring has 256 slots, allowing 64 slots packet
> yields 4 in-flight packets in worst case.
> 2. Older netback could not handle this large number of slots and it's
> likely to deem the frontend malicious.
>
> For #1, we don't actually care that much if guest screws itself by
> generating 64 slot packets. #2 is more concerning.

How many slots can the older netback handle?
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