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    Subject[143/262] tcp: properly update lost_cnt_hint during shifting
    3.0-stable review patch.  If anyone has any objections, please let me know.

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


    From: "Yan, Zheng" <zheng.z.yan@intel.com>

    [ Upstream commit 1e5289e121372a3494402b1b131b41bfe1cf9b7f ]

    lost_skb_hint is used by tcp_mark_head_lost() to mark the first unhandled skb.
    lost_cnt_hint is the number of packets or sacked packets before the lost_skb_hint;
    When shifting a skb that is before the lost_skb_hint, if tcp_is_fack() is ture,
    the skb has already been counted in the lost_cnt_hint; if tcp_is_fack() is false,
    tcp_sacktag_one() will increase the lost_cnt_hint. So tcp_shifted_skb() does not
    need to adjust the lost_cnt_hint by itself. When shifting a skb that is equal to
    lost_skb_hint, the shifted packets will not be counted by tcp_mark_head_lost().
    So tcp_shifted_skb() should adjust the lost_cnt_hint even tcp_is_fack(tp) is true.

    Signed-off-by: Zheng Yan <zheng.z.yan@intel.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
    ---
    net/ipv4/tcp_input.c | 4 +---
    1 file changed, 1 insertion(+), 3 deletions(-)

    --- a/net/ipv4/tcp_input.c
    +++ b/net/ipv4/tcp_input.c
    @@ -1380,9 +1380,7 @@ static int tcp_shifted_skb(struct sock *

    BUG_ON(!pcount);

    - /* Tweak before seqno plays */
    - if (!tcp_is_fack(tp) && tcp_is_sack(tp) && tp->lost_skb_hint &&
    - !before(TCP_SKB_CB(tp->lost_skb_hint)->seq, TCP_SKB_CB(skb)->seq))
    + if (skb == tp->lost_skb_hint)
    tp->lost_cnt_hint += pcount;

    TCP_SKB_CB(prev)->end_seq += shifted;



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