understanding network split device drivers

[Diwaker Gupta <diwaker.lists@gmail.com>]

I'm trying to understand the architecture for I/O devices (in particular, the
network drivers) in Xen. I know the broad design and structure of the split
devices drivers. The following picture will hopefully make it easier for
people to answer my questions:

                dom-0                          dom-1
------------------------------------     --------------
    device driver        backend   |     |   frontend
                   ==>             | ==> |
    (eg: e1000)       (eg: netback)|     |(eg: netfront)
------------------------------------     --------------
                  ||                  
                  \/                  
             (questions!!)


I'm not very knowledgeable on the linux networking stack, so bear with me if I
ask something obvious.

o where and how is this pipelining (between the actual device driver and the
backend) set up in the code? 

o is it something xen specific, or is it done via standard linux networking? 

o is there some buffer/queue between the backend and the actual device driver? 

o does the backend get any kind of notification from the hardware in case the
send/recv fails (since IIUC netback queues requests asynchronous processing)

o where exactly do the bridge utils fit in this picture?

TIA
Diwaker
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