This is a Solaris SCSI Target Mode Framework.

The main part is the libstmf library.

Functions in this library provide configuration management of the SCSI Target
Mode Framework (STMF), allowing clients to manage the provisioning of logical
units and targets to the initiator clients of the framework.

stmfadm binary is a command line interface to the libstmf libstmf.
svc-stmf binary is a daemon for storing settings and restoring on boot.

This sources was taken from the illumos project https://www.illumos.org