MLNX_OFED Features Verbs and Capabilities Flow Steering

Flow steering defines the concept of domain and priority. Each domain represents a user agent that can attach a flow. The domains are prioritized. A higher priority domain will always supersede a lower priority domain when their flow specifications overlap. Setting a lower priority value will result in a higher priority.
In addition to the domain, there is a priority within each of the domains. Each domain can have at most 2^12 priorities in accordance with its needs.
The following are the domains at a descending order of priority:

User Verbs allows a user application QP to be attached to a specified flow when using ibv_exp_create_flow and ibv_exp_destroy_flow verbs

- ibv_exp_create_flow
  
  struct ibv_exp_flow *ibv_exp_create_flow(struct ibv_qp *qp, struct ibv_exp_flow_attr
  
  *flow)
  
  Input parameters:
  - struct ibv_qp - the attached QP.
  - struct ibv_exp_flow_attr - attaches the QP to the flow specified. The flow contains mandatory control parameters and optional L2, L3 and L4 headers. The optional headers are detected by setting the size and num_of_specs fields:
    struct ibv_exp_flow_attr can be followed by the optional flow headers structs:
    
    struct ibv_exp_flow_spec_ib
    
    struct ibv_exp_flow_spec_eth
    
    struct ibv_exp_flow_spec_ipv4
    
    struct ibv_exp_flow_spec_tcp_udp
    
    struct ibv_exp_flow_spec_ipv6
    
    Note: ipv6 is applicable for ConnectX®-4 and ConnectX®-4 Lx only.
    
    For further information, please refer to the ibv_exp_create_flow man page.
    
    Be advised that as of MLNX_OFED v2.0-3.0.0, the parameters (both the value and the mask) should be set in big-endian format.
    
    Each header struct holds the relevant network layer parameters for matching. To enforce the match, the user sets a mask for each parameter.
    The mlx5 driver supports partial masks. The mlx4 driver supports the following masks:
    - All one mask - include the parameter value in the attached rule
      Note: Since the VLAN ID in the Ethernet header is 12bit long, the following parameter should be used: flow_spec_eth.mask.vlan_tag = htons(0x0fff)
    - All zero mask - ignore the parameter value in the attached rule

When setting the flow type to NORMAL, the incoming traffic will be steered according to the rule specifications. ALL_DEFAULT and MC_DEFAULT rules options are valid only for Ethernet link type since InfiniBand link type packets always include QP number.
For further information, please refer to the relevant man pages.

Flow steering is a model which steers network flows based on flow specifications to specific QPs. Those flows can be either unicast or multicast network flows. In order to maintain flexibility, domains and priorities are used. Flow steering uses a methodology of flow attribute, which is a combination of L@-L4 flow specifications, a destination QP and a priority. Flow steering rules may be inserted either by using ethtool or by using InfiniBand verbs. The verbs abstraction uses a different terminology from the flow attribute (ibv_flow_attr), defined by a combination of specifications (struct ibv_flow_spec_*).

Flow Steering Experimental vs. RDMA-Core Verbs and Capabilities

Experimental Verbs		RDMA-Core
Verbs
ibv_exp_create_flow		ibv_create_flow
	IBV_EXP_FLOW_ATTR_*		IBV_FLOW_ATTR
	IBV_EXP_FLOW_ATTR_FLAGS_ALLOW_LOOP_BACK		IBV_FLOW_ATTR_FLAGS_ALLOW_LOOP_BACK
	IBV_EXP_FLOW_SPEC_ETH		IBV_FLOW_SPEC_ETH
	IBV_EXP_FLOW_SPEC_IB		Not supported by RDMA-CORE
	IBV_EXP_FLOW_SPEC_IPV4		IBV_FLOW_SPEC_IPV4
	IBV_EXP_FLOW_SPEC_IPV6		IBV_FLOW_SPEC_IPV6
	IBV_EXP_FLOW_SPEC_IPV4_EXT		IBV_FLOW_SPEC_IPV4_EXT
	IBV_EXP_FLOW_SPEC_IPV6_EXT		IBV_FLOW_SPEC_IPV6
	IBV_EXP_FLOW_SPEC_TCP		IBV_EXP_FLOW_SPEC_TCP
	IBV_EXP_FLOW_SPEC_UDP		IBV_FLOW_SPEC_UDP
	IBV_EXP_FLOW_SPEC_VXLAN_TUNNEL		IBV_FLOW_SPEC_VXLAN_TUNNEL
	IBV_EXP_FLOW_SPEC_INNER		IBV_FLOW_SPEC_INNER
	IBV_EXP_FLOW_SPEC_ACTION_TAG		IBV_FLOW_SPEC_ACTION_TAG
	IBV_EXP_FLOW_SPEC_ACTION_DROP		IBV_FLOW_SPEC_ACTION_DROP
	Ibv_exp_flow_spec_*		Ibv_flow_spec_*
	Ibv_exp_destroy_flow		Ibv_destroy_flow
Capabilities
IBV_EXP_DEVICE_MANAGED_FLOW_STEERING		IBV_DEVICE_MANAGED_FLOW_STEERING

ibv_create_flow mlx5dv_create_flow

参考

https://docs.mellanox.com/display/rdmacore50/Flow+Steering

https://docs.mellanox.com/display/MLNXOFEDv461000/Flow+Steering