On 9/26/19 9:28 AM, Ori Kam wrote:
This patch set implements the hairpin feature.
The hairpin feature was introduced in RFC[1]
The hairpin feature (different name can be forward) acts as "bump on the wire",
meaning that a packet that is received from the wire can be modified using
offloaded action and then sent back to the wire without application intervention
which save CPU cycles.
The hairpin is the inverse function of loopback in which application
sends a packet then it is received again by the
application without being sent to the wire.
The hairpin can be used by a number of different NVF, for example load
balancer, gateway and so on.
As can be seen from the hairpin description, hairpin is basically RX queue
connected to TX queue.
Is it just a pipe or RTE flow API rules required?
If it is just a pipe, what about transformations which could be useful
in this
case (encaps/decaps, NAT etc)? How to achieve it?
If it is not a pipe and flow API rules are required, why is peer information
required?
During the design phase I was thinking of two ways to implement this
feature the first one is adding a new rte flow action. and the second
one is create a special kind of queue.
The advantages of using the queue approch:
1. More control for the application. queue depth (the memory size that
should be used).
But it inherits many parameters which are not really applicable to hairpin
queues. If all parameters are applicable, it should be explained in the
context of the hairpin queues.
2. Enable QoS. QoS is normaly a parametr of queue, so in this approch it
will be easy to integrate with such system.
Could you elaborate it.
3. Native integression with the rte flow API. Just setting the target
queue/rss to hairpin queue, will result that the traffic will be routed
to the hairpin queue.
It sounds like queues are not required for flow API at all.
If the goal is to send traffic outside to specified physical port,
just specify it as an flow API action. That's it.
4. Enable queue offloading.
Which offloads are applicable to hairpin queues?
Each hairpin Rxq can be connected Txq / number of Txqs which can belong to a
different ports assuming the PMD supports it. The same goes the other
way each hairpin Txq can be connected to one or more Rxqs.
This is the reason that both the Txq setup and Rxq setup are getting the
hairpin configuration structure.
From PMD prespctive the number of Rxq/Txq is the total of standard
queues + hairpin queues.
To configure hairpin queue the user should call
rte_eth_rx_hairpin_queue_setup / rte_eth_tx_hairpin_queue_setup insteed
of the normal queue setup functions.
The hairpin queues are not part of the normal RSS functiosn.
To use the queues the user simply create a flow that points to RSS/queue
actions that are hairpin queues.
The reason for selecting 2 new functions for hairpin queue setup are:
1. avoid API break.
2. avoid extra and unused parameters.
This series must be applied after series[2]
[1]
https://inbox.dpdk.org/dev/1565703468-55617-1-git-send-email-or...@mellanox.com/
[2]
https://inbox.dpdk.org/dev/1569398015-6027-1-git-send-email-viachesl...@mellanox.com/
[snip]
