[tcp-dsack] interface for retrieving dsack information

Hi,

I'm trying to count the number of unnecessary retransmissions for a
tcp connection. DSACK reports the receipt of duplicate segment to
sender, so I plan to count the duplicate transmissions reported by
DSACK as unnecessary retransmissions. My question is if there is a
nice interface, like tcp_info, which can be used for retrieving the
number of duplicate transmissions from DSACK? tcp_info structure
doesn't include such information.

Thanks a lot.

Yinglin