[RFC,net-next,v2,0/2] net: flow_offload: add support for per action hw stats

Message

Oz Shlomo Oct. 3, 2022, 6:17 a.m. UTC

There are currently two mechanisms for populating hardware stats:
1. Using flow_offload api to query the flow's statistics.
   The api assumes that the same stats values apply to all
   the flow's actions.
   This assumption breaks when action drops or jumps over following
   actions.
2. Using hw_action api to query specific action stats via a driver
   callback method. This api assures the correct action stats for
   the offloaded action, however, it does not apply to the rest of the
   actions in the flow's actions array, as elaborated below.

The current hw_action api does not apply to the following use cases:
1. Actions that are implicitly created by filters (aka bind actions).
   In the following example only one counter will apply to the rule:
   tc filter add dev $DEV prio 2 protocol ip parent ffff: \
        flower ip_proto tcp dst_ip $IP2 \
        action police rate 1mbit burst 100k conform-exceed drop/pipe \
        action mirred egress redirect dev $DEV2
  
2. Action preceding a hw action.
   In the following example the same flow stats will apply to the sample and
   mirred actions:
    tc action add police rate 1mbit burst 100k conform-exceed drop / pipe
    tc filter add dev $DEV prio 2 protocol ip parent ffff: \
        flower ip_proto tcp dst_ip $IP2 \
        action sample rate 1 group 10 trunc 60 pipe \
        action police index 1 \
        action mirred egress redirect dev $DEV2
        
3. Meter action using jump control.
   In the following example the same flow stats will apply to both
   mirred actions:
    tc action add police rate 1mbit burst 100k conform-exceed jump 2 / pipe
    tc filter add dev $DEV prio 2 protocol ip parent ffff: \
        flower ip_proto tcp dst_ip $IP2 \
        action police index 1 \
        action mirred egress redirect dev $DEV2
        action mirred egress redirect dev $DEV3

This series provides the platform to query per action stats for in_hw flows.

The first patch is a preparation patch

The second patch extends the flow_offload api to return stats array corresponding
to the flow's actions list.
The api populates all the actions' stats in a single callback invocation.
It also allows drivers to avoid per-action lookups by maintain pre-processed
array of the flow's action counters.

Note that this series does not change the existing functionality, thus preserving
the current stats per flow design.

Mellanox driver implementation of the proposed api will follow the rfc discussion.

-----

v1 -> v2:
- Change flow_offload action stats to a static array
- Assign action_cookie to flow_offload actions
- Use action cookie to dereference the action to be updated
- Remove single action update

Oz Shlomo (1):
  net: flow_offload: add action stats api

Roi Dayan (1):
  net: sched: Pass flow_stats instead of multiple stats args

 include/net/flow_offload.h | 10 ++++++++++
 include/net/pkt_cls.h      | 27 ++++++++++++++++++++-------
 net/sched/cls_api.c        |  1 +
 net/sched/cls_flower.c     |  8 ++------
 net/sched/cls_matchall.c   |  6 +-----
 5 files changed, 34 insertions(+), 18 deletions(-)