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

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 29 Jun 2006, at 01:20, Herbert Xu wrote:

> > 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.
Each segment will need a header though, I'd imagine, so whoever does 
the segmentation needs to know the packet header length? Maybe I'm just 
confused. :-) Could you briefly explain what the inter-domain data 
format would be (e.g., is there a header, etc.), and gso_{size,segs}, 
for some arbitrary IP-encapsulated protocol? And how that information 
would be used to perform segmentation in the backend domain? Is the 
segmentation algorithm any different at all when the protocol is 
specifically TCPv4? I'd like to add some documentation of all this to 
netif.h when I have it clear in my head.
The patches you sent look fine. I'd really like to understand this 
stuff before turning it on though.
 -- Keir


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