git: tcp: Ignore duplicate ACK carries useless DSACK

[Sepherosa Ziehau <sephe@xxxxxxxxxxxxxxxxxxxxxxx>]

commit 6c1bbf5766c410de3848fb56450d02cca103cb73
Author: Sepherosa Ziehau <sephe@dragonflybsd.org>
Date:   Thu May 3 16:37:17 2012 +0800

    tcp: Ignore duplicate ACK carries useless DSACK
    
    This mainly used to avoid unnecessary early retransmit and fast
    retransmit as show in the following two dumps:
    http://leaf.dragonflybsd.org/~sephe/early.xpl (~4.8sec)
    http://leaf.dragonflybsd.org/~sephe/fast.xpl (~12.35sec)

Summary of changes:
 sys/netinet/tcp_input.c |   35 +++++++++++++++++++++++++++++++----
 sys/netinet/tcp_sack.c  |   19 ++++++++++++++-----
 sys/netinet/tcp_var.h   |    2 ++
 3 files changed, 47 insertions(+), 9 deletions(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/6c1bbf5766c410de3848fb56450d02cca103cb73


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