Provide a function that maps packet's rss hash to a cpu that should handle
it. This function is needed to find appropriate src port for outgoing
tcp/udp connection. Use this function to forward de-fragmented ip packet
to avoid one extra hop too.
This patch introduce a logic to divide cpus between available hw queue
pairs. Each cpu with hw qp gets a set of cpus to distribute traffic
to. The algorithm doesn't take any topology considerations into account yet.
Instead of forward() deciding packet destination make it collect input
for RSS hash function depending on packet type. After data is collected
use toeplitz hash function to calculate packet's destination.
This patch adds new class distributed_device which is responsible for
initializing HW device and it is shared between all cpus. Old device
class responsibility becomes managing rx/tx queue pair and it is local
per cpu. Each cpu have to call distributed_device::init_local_queue() to
create its own device. The logic to distribute cpus between available
queues (in case there is no enough queues for each cpu) is in the
distributed_device currently and not really implemented yet, so only one
queue or queues == cpus scenarios are supported currently, but this can
be fixed later.
The plan is to rename "distributed_device" to "device" and "device"
to "queue_pair" in later patches.
Currently each cpu creates network device as part of native networking
stack creation and all cpus create native networking stack independently,
which makes it impossible to use data initialized by one cpu in another
cpu's networking device initialization. For multiqueue devices often some
parts of an initialization have to be handled by one cpu and all other
cpus should wait for the first one before creating their network devices.
Even without multiqueue proxy devices should be created after master
device is created so that proxy device may get a pointer to the master
at creation time (existing code uses global per cpu device pointer and
assume that master device is created on cpu 0 to compensate for the lack
of ordering).
This patch makes it possible to delay native networking stack creation
until network device is created. It allows one cpu to be responsible
for creation of network devices on multiple cpus. Single queue device
initialize master device on one cpu and call other cpus with a pointer
to master device and its cpu id which are used in proxy device creation.
This removes the need for per cpu device pointer and "master on cpu 0"
assumption from the code since now master device and slave devices know
about each other and can communicate directly.
Some packets, like arp replies, are broadcast to all cpus for handling,
but only packet structure is copied for each cpu, the actual packet data
is the same for all of them. Currently networking stack mangles a
packet data during its travel up the stack while doing ntoh()
translations which cannot obviously work for broadcaster packets. This
patches fixes the code to not modify packet data while doing ntoh(), but
do it in a stack allocated copy of a data instead.
Classifier returns what cpu a packets should be processed on. It may
return special broadcast identifier. The patch includes classifier for
tcp, udp and arp. Arp classifier broadcasts arp reply to all cpus. Default
classifier does not forward packet.
Will need it later to handle forwarded packets. Also save net::device
pointer in thread local variable to get to device instance easily. When
we ill have more then one device per cpu we will have to change to
something more sophisticated.
If an L3 packet receiver is not able to register itself as a packet receiver
after processing a packet, or if it is simply not dispatched quickly enough,
then we will drop packets.
Add a queue at the protocol layer to buffer those packets.
