(final design)
MRT_API_CONFIG(BW_UPCALL) rc=0 api=0x200
MRT_ADD_VIF rc=0
MRT_ADD_MFC rc=0
racing adders(4) vs delers(4x10ms) for 200 seconds...
no panic in 200 seconds
(earlier designs: 240s two-thread; 150k/300k burst cycles with
 'adder: 120000 meters installed / traffic: 600 packets injected';
 none panicked; one burst run wedged ssh for ~4 minutes on the
 self-sustaining upcall-storm - see VERDICT.md)