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

On Wed, Jun 28, 2006 at 03:24:37PM +0100, Keir Fraser wrote:
> Adding new fields on the end of the existing structure is limiting. 
> Maybe we could chain extra info structures by declaring 
> NETTXF_extra_info in the leading request, then have a sequence of 
> netif_tx_extras, each of which is a discriminated union (so a 
> NETEXTRA_* type field, a flag indicating if this is the last extra-info 
> for this packet, plus a union)?

Good idea.  I've changed the interface to do exactly that.
> Many NICs support TSO so there should be support in network stacks 
> other than Linux. What about *BSD, Solaris, and Windows?

They should be able to use the GSO interface and simply always set
gso_type to XEN_GSO_TCPV4.
> Yes, we want them, and explicit code in netfront/netback to convert 
> between Linux gso types and 'wire' gso types. Even if they are 
> initially the same!


> Another question: why are gso_size and gso_segs both required? Surely 
> those, plus the overall request size, are redundant. e.g., shouldn't 
> gso_segs = tot_size / gso_size (rounded up)?

For TSO, gso_segs can be easily determined from the packet and gso_size.
However, for GSO, we don't know the packet header length so the same is
not true.

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