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    Subject[PATCH 4.14 072/146] tcp_bbr: reset long-term bandwidth sampling on loss recovery undo
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Neal Cardwell <ncardwell@google.com>


    [ Upstream commit 600647d467c6d04b3954b41a6ee1795b5ae00550 ]

    Fix BBR so that upon notification of a loss recovery undo BBR resets
    long-term bandwidth sampling.

    Under high reordering, reordering events can be interpreted as loss.
    If the reordering and spurious loss estimates are high enough, this
    can cause BBR to spuriously estimate that we are seeing loss rates
    high enough to trigger long-term bandwidth estimation. To avoid that
    problem, this commit resets long-term bandwidth sampling on loss
    recovery undo events.

    Signed-off-by: Neal Cardwell <ncardwell@google.com>
    Reviewed-by: Yuchung Cheng <ycheng@google.com>
    Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/ipv4/tcp_bbr.c | 1 +
    1 file changed, 1 insertion(+)

    --- a/net/ipv4/tcp_bbr.c
    +++ b/net/ipv4/tcp_bbr.c
    @@ -878,6 +878,7 @@ static u32 bbr_undo_cwnd(struct sock *sk

    bbr->full_bw = 0; /* spurious slow-down; reset full pipe detection */
    bbr->full_bw_cnt = 0;
    + bbr_reset_lt_bw_sampling(sk);
    return tcp_sk(sk)->snd_cwnd;
    }


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