Re: [Xen-devel] [0/5] [NET]: Add TSO support

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 29 Jun 2006, at 13:46, Herbert Xu wrote:

> > What if gso_segs, or any other gso parameter (e.g., type), is set
> > incorrectly? The backend cannot trust frontend clients, so I'm rather
> > worried that we could make the backend network stack crash!
> gso_type is a key so the OS (Linux) must deal with all possible values.
> Any packet with a protocol or feature bit that it does not recognise
> will be dropped.
>
> However, you have a very good point regarding gso_segs.  I'll change it
> so that it is always recalculated for SKB_GSO_DODGY packets.
If you can recalculate it, why is the field required at all (both in 
the skbuff and in the netif_tx_extra)? You previously said it was 
needed because it can't be recalculated (until you get to the 
segmentation code, which may be very late in packet processing).
We could calculate gso_segs for TCPv4 in netback, which is all we care 
about right now.
 -- Keir


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