Loopback Indicator question for all

[oulijun <oulijun@xxxxxxxxxx>]

Hi, all
  I have been reviewing the Loopback Indicator definition and usecase with IB Specification Vol
Vol 1-Release-1.3-2015-03-03.pdf and Annex A16:RDMA over ConvergedEthernet (RoCE).pdf

  The protocol specifies:
  o10-6.2-1.1: If the CI supports the Loopback Indicator, the CI shall report
it through the Query HCA Verb. The CI shall accept the Loopback Indicator
as an input modifier to the Create Address Handle, Modify Address
Handle, Modify QP and Modify EEC verbs

  I have checked the create address handle verbs' input modifier.
  struct rdma_ah_attr {
	struct ib_global_route	grh;
	u8			sl;
	u8			static_rate;
	u8			port_num;
	u8			ah_flags;
	enum rdma_ah_attr_type type;
	union {
		struct ib_ah_attr ib;
		struct roce_ah_attr roce;
		struct opa_ah_attr opa;
	};
};

and the verb for create ah in protocol specification.
input modifiers:
   ...
   ...
   • Loopback Indicator (if the HCA supports Loopback Indicator
on Address Handles). DLID and Loopback Indicator are mutually
exclusive.
   ...

   I don't see why defined the loopback indicator and expose for app?
   I understand that the loopback indicator should be gived by ofed, the
user can configue it. Any other understand?

thanks
Lijun ou

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