Isn't that only the number of packets dropped by the BPF filter due to
the inability of it to process the packets fast enough?
Side hypothesis: using tcpdump on the same machine that netperf is
receiving on will cause you to drop more packets on a sufficently fast
enough link to bog down the machine.
Anyways I was under the impression that he wanted the number of packets
dropped either before being received by the machine or dropped by the
machine due to lack of buffer space or ability to process through the
stack. The latter can probably be found in a stats counter the OS or
driver keeps; though I don't know how to get at it on a given OS.
Greg