...
$/Micrium/Software/uC-TCPIP-V2/App/NDIT/Source/ndit_mcast.h
When using µCµC/OS-II:
$/Micrium/Software/uC-IPerf/Source/uCOS-II.c
...
$/Micrium/Software/uC-TCPIP-V2/App/NDIT/OS/uCOS-II/ndit_mcast_os.c
Or when using µCµC/OS-III:
$/Micrium/Software/uC-IPerf/Source/uCOS-III.c
...