An iSCSI Targets offers storage via iSCSI to a network. An Initiator connects to a target to use the storage on the target.
Device Drivers ---> <M> Generic Target Core Mod (TCM) and ConfigFS Infrastructure ---> <M> TCM/IBLOCK Subsystem Plugin for Linux/BLOCK <M> TCM/FILEIO Subsystem Plugin for Linux/VFS <M> Linux-iSCSI.org iSCSI Target Mode Stack
The configuration tool is called targetcli and is included in two packages: sys-block/targetcli or sys-block/targetcli-fb (free-branch). The free-branch version is more up-to-date, so this page assumes that one.
emerge --ask sys-block/targetcli-fb