[Qemu-devel] difference between receive_raw() and receive() NetClientInfo methods ?

[Luigi Rizzo]

Can someone clarify what is the difference between the two methods

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eceive_raw() and receive() in NetClientInfo ?

 

tap seems to be the only backend actually implementing receive_raw(),

but apart from prepending a vnet_hdr i cannot tell what is this for,

and whether receive_raw() is a custom addon for tap, or it can be used

by other backends to implement different features.

The reason I am asking is that we are working on a "fewer copies"

path between guests, and one of the things we need is an

asynchronous "receive" so that a backend can notify the frontend

when a buffer has been actually consumed.

Right now nc->info->receive() and friends are all synchronous,

and there is no mechanism to support asynchronous completion,

which forces the backend to make a copy if it cannot

complete the request inline.

Hence i probably need to add another method to NetClientInfo

so that the frontend can register the callback, or pass it to

the backend together with the buffer/iov

 

thanks

luigi