.TH "libnvmf_tid_set_identity" 9 "libnvmf_tid_set_identity" "October 2026" "libnvme API manual" LINUX
.SH NAME
libnvmf_tid_set_identity \- Set the subsystem and host identity together.
.SH SYNOPSIS
.B "int" libnvmf_tid_set_identity
.BI "(struct libnvmf_tid *tid "  ","
.BI "const char *subsysnqn "  ","
.BI "const char *hostnqn "  ","
.BI "const char *hostid "  ");"
.SH ARGUMENTS
.IP "tid" 12
The transport ID.
.IP "subsysnqn" 12
Subsystem NQN, or NULL to leave it unchanged.
.IP "hostnqn" 12
Host NQN, or NULL to leave it unchanged.
.IP "hostid" 12
Host Identifier, or NULL to leave it unchanged (or derive it).
.SH "DESCRIPTION"
Identity is applied after addressing -- which subsystem, and which host
persona, are decided by context.  A NULL argument leaves that field as-is,
which is why the three are set through one call rather than per-field
setters (addressing has none: it is construction-only).

hostid is never left to chance: when no hostid is set but the resulting
hostnqn carries a UUID (nqn.2014-08.org.nvmexpress:uuid:<X>), the hostid is
derived from it -- the deterministic, per-host value (TP4126), never a
random one.  A hostid without a hostnqn is rejected: one host is one
(hostnqn, hostid) pair.
.SH "RETURN"
0 on success; -EINVAL for a NULL \fItid\fP or a hostid without a hostnqn;
-ENOMEM on allocation failure.