[PATCH net-next 0/2] tcp: improve handling of DSACK covering multiple segments

[Priyaranjan Jha <priyarjha@google.com>]

Currently, while processing DSACK, we assume DSACK covers only one
segment. This leads to significant underestimation of no. of duplicate
segments with LRO/GRO. Also, the existing SNMP counters, TCPDSACKRecv
and TCPDSACKOfoRecv, make similar assumption for DSACK, which makes them
unusable for estimating spurious retransmit rates.

This patch series fixes the segment accounting with DSACK, by estimating
number of duplicate segments based on: (DSACKed sequence range) / MSS.
It also introduces a new SNMP counter, TCPDSACKRecvSegs, which tracks
the estimated number of duplicate segments.

Priyaranjan Jha (2):
  tcp: fix segment accounting when DSACK range covers multiple segments
  tcp: add SNMP counter for no. of duplicate segments reported by DSACK

 include/uapi/linux/snmp.h |  1 +
 net/ipv4/proc.c           |  1 +
 net/ipv4/tcp_input.c      | 81 ++++++++++++++++++++++-----------------
 3 files changed, 47 insertions(+), 36 deletions(-)

-- 
2.27.0.389.gc38d7665816-goog