prior to kernel 2.6.12 drops were being reported in some
cases when no actual drop occurred. This was because RNBC was being
counted as a drop when it is in fact just notification of buffer congestion.
However the fix mapped MPC (missed packet count) to 3 kernel
stats as can be seen below. The problem with this is that rx_dropped + rx_missed
are added for the drop column reported in /proc/net/dev.
I.E any actual drops would be double counted.

--- e1000_main.c	2005-05-17 21:31:44.000000000 +0000
+++ e1000_main_drops.c	2005-07-27 15:29:43.000000000 +0000
@@ -2639,11 +2639,9 @@
 		adapter->stats.crcerrs + adapter->stats.algnerrc +
 		adapter->stats.rlec + adapter->stats.mpc + 
 		adapter->stats.cexterr;
-	adapter->net_stats.rx_dropped = adapter->stats.mpc;
 	adapter->net_stats.rx_length_errors = adapter->stats.rlec;
 	adapter->net_stats.rx_crc_errors = adapter->stats.crcerrs;
 	adapter->net_stats.rx_frame_errors = adapter->stats.algnerrc;
-	adapter->net_stats.rx_fifo_errors = adapter->stats.mpc;
 	adapter->net_stats.rx_missed_errors = adapter->stats.mpc;
 
 	/* Tx Errors */