Filter Based Vrouter Dropstats

This blueprint proposes to enhance the dropstats utility in vrouter. Currently, the vrouter keeps counters (a counter per reason for drop) globally. E.g., a dropped packet in any of the overlay networks at the vrouter causes the same set of counters to be incremented. This proposal is to be able to set a filter so that the counters get incremented only when a packet matching the filter is dropped.

The existing global counters continue to work as before. The user space dropstats utility provides the ability to register and unregister a filter. A filter is a tuple consisting of the following:
+ source and destination ips
+ source and destination ports
+ transport protocol
+ vrf id

Any of the elements of the tuple may be left unspecified during registration. Any unspecified part is treated like a wild card.

When a filter is registered the vrouter kernel module begins tracking the filter specific statistics for dropped packets. When the filter is unregistered, the counters are cleared. Subsequent registration will begin counting from zero.