RFR 15 8243099: SO_INCOMING_NAPI_ID support

[Daniel Fuchs]

Hi Vladimir,

On 06/05/2020 00:36, Ivanov, Vladimir A wrote:
> I was failed to get non-zero value for the ServerSocket and according to clarification from the network experts:
> " NAPI IDs is not marked on listening sockets. A listening socket can accept multiple connections coming on different queues. So even if we do it, it can keep changing and we don't see a use case for it. Once a connection is accepted, accepted or the child socket will return a valid NAPI id."
> 
> So seems the listener sockets will have this as zero.

Thanks for this clarifications! Could you also clarify how
this is supposed to work with UDP sockets?

I mean - does the socket needs to be connected to make
the best use of this feature?

If not connected, will a listening UDP socket always be
assigned to the same device queue regardless of the source
of the datagrams it receives or might the device queue id
change with each incoming packet depending on its source?

I am especially intrigued by the case where a DatagramSocket
is bound to the wildcard address and as such potentially
able to receive datagrams comming through any active NIC.

best regards,

-- daniel