need API to get DPU `hostnqn`

[glimchb]

in CSI, for example, we need DPU host NQN before DPU can establish remote backend connectivity to the storage targets

this is needed so we can allow those hosts to connect to the target. assuming allow_any is not an option see example nvmf_subsystem_add_host here https://spdk.io/doc/jsonrpc.html#rpc_nvmf_subsystem_add_host

so we need new API that can either return us the generated by DPU hostnqn or a new API to set hostnqn to the DPU

[jainvipin]

Well #133 had proposed following parameters for the device itself, host_nqn was one of them

message NvmeIniDevSpec {
  // (mandatory) initiator device object key.
  types.ObjectKey nvme_ini_dev_key    = 1;
  // (mandatory) unique NQN identifer for the host, used in fabric connect to
  // the NVMe-oF target
  bytes        host_nqn             = 2;
  // (mandatory) unique host ID, used in fabric connect to the NVMe-oF target.
  bytes        host_id              = 3;
}

[jainvipin]

But again, this is DPU device specific thing, not a backend property. I am not sure if #216 is a fix to this issue. What we may need is Device Initialization API vs. tucking in host_nqn in the backend proto

[glimchb]

Device Initialization is not a good place if we want to support multiple NQNs per DPU and then use different hostNQNs when we connect to different targets so we need that in BackEnd APIs and not init

[glimchb]

if we follow nvme-cli in linux, we see the same.

there are default /etc/nvme/hostnqn and /etc/nvme/hostid but you can also specify hostid and hostnqn during connect command to override default:

 nvme connect --help
Usage: nvme connect <device> [OPTIONS]

Connect to NVMeoF subsystem

Options:
  [  --transport=<LIST>, -t <LIST> ]    --- transport type
  [  --nqn=<LIST>, -n <LIST> ]          --- nqn name
  [  --traddr=<LIST>, -a <LIST> ]       --- transport address
  [  --trsvcid=<LIST>, -s <LIST> ]      --- transport service id (e.g. IP
                                            port)
  [  --host-traddr=<LIST>, -w <LIST> ]  --- host traddr (e.g. FC WWN's)
  [  --hostnqn=<LIST>, -q <LIST> ]      --- user-defined hostnqn
  [  --hostid=<LIST>, -I <LIST> ]       --- user-defined hostid (if default
                                            not used)
  [  --nr-io-queues=<LIST>, -i <LIST> ] --- number of io queues to use
                                            (default is core count)
  [  --nr-write-queues=<LIST>, -W <LIST> ] --- number of write queues to use
                                            (default 0)
  [  --nr-poll-queues=<LIST>, -P <LIST> ] --- number of poll queues to use
                                            (default 0)
  [  --queue-size=<LIST>, -Q <LIST> ]   --- number of io queue elements to
                                            use (default 128)
  [  --keep-alive-tmo=<LIST>, -k <LIST> ] --- keep alive timeout period in
                                            seconds
  [  --reconnect-delay=<LIST>, -c <LIST> ] --- reconnect timeout period in
                                            seconds
  [  --ctrl-loss-tmo=<LIST>, -l <LIST> ] --- controller loss timeout period in
                                            seconds
  [  --duplicate_connect, -D ]          --- allow duplicate connections
                                            between same transport host and
                                            subsystem port
  [  --disable_sqflow, -d ]             --- disable controller sq flow
                                            control (default false)
  [  --hdr_digest, -g ]                 --- enable transport protocol header
                                            digest (TCP transport)
  [  --data_digest, -G ]                --- enable transport protocol data
                                            digest (TCP transport)