what about auditing and its logs? I would use auditing records and would regulary map IPs of coming sessions with its PIDs (lsof) ... then compare autid PID actions with lsof records to get answer...
you cannot check physical SEA interface from the LPAR. LPAR itself cannot see if the SEA (VIOS) interface does (not) have a link.
Only the way is using ping test to the default gateway ... it...