Merge branch 'tcp-add-4-new-stats'

Wei Wang says:

====================
tcp: add 4 new stats

This patch series adds 3 RFC4898 stats:
1. tcpEStatsPerfHCDataOctetsOut
2. tcpEStatsPerfOctetsRetrans
3. tcpEStatsStackDSACKDups
and an addtional stat to record the number of data packet reordering
events seen:
4. tcp_reord_seen

Together with the existing stats, application can use them to measure
the retransmission rate in bytes, exclude spurious retransmissions
reflected by DSACK, and keep track of the reordering events on live
connections.
In particular the networks with different MTUs make bytes-based loss stats
more useful. Google servers have been using these stats for many years to
instrument transport and network performance.

Note: The first patch is a refactor to add a helper to calculate
opt_stats size in order to make later changes cleaner.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>