lkml.org 
[lkml]   [2015]   [Apr]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 3.10 05/31] tcp: fix FRTO undo on cumulative ACK of SACKed range
    Date
    3.10-stable review patch.  If anyone has any objections, please let me know.

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

    From: Neal Cardwell <ncardwell@google.com>

    [ Upstream commit 666b805150efd62f05810ff0db08f44a2370c937 ]

    On processing cumulative ACKs, the FRTO code was not checking the
    SACKed bit, meaning that there could be a spurious FRTO undo on a
    cumulative ACK of a previously SACKed skb.

    The FRTO code should only consider a cumulative ACK to indicate that
    an original/unretransmitted skb is newly ACKed if the skb was not yet
    SACKed.

    The effect of the spurious FRTO undo would typically be to make the
    connection think that all previously-sent packets were in flight when
    they really weren't, leading to a stall and an RTO.

    Signed-off-by: Neal Cardwell <ncardwell@google.com>
    Signed-off-by: Yuchung Cheng <ycheng@google.com>
    Fixes: e33099f96d99c ("tcp: implement RFC5682 F-RTO")
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/ipv4/tcp_input.c | 7 ++++---
    1 file changed, 4 insertions(+), 3 deletions(-)

    --- a/net/ipv4/tcp_input.c
    +++ b/net/ipv4/tcp_input.c
    @@ -3076,10 +3076,11 @@ static int tcp_clean_rtx_queue(struct so
    if (seq_rtt < 0) {
    seq_rtt = ca_seq_rtt;
    }
    - if (!(sacked & TCPCB_SACKED_ACKED))
    + if (!(sacked & TCPCB_SACKED_ACKED)) {
    reord = min(pkts_acked, reord);
    - if (!after(scb->end_seq, tp->high_seq))
    - flag |= FLAG_ORIG_SACK_ACKED;
    + if (!after(scb->end_seq, tp->high_seq))
    + flag |= FLAG_ORIG_SACK_ACKED;
    + }
    }

    if (sacked & TCPCB_SACKED_ACKED)



    \
     
     \ /
      Last update: 2015-04-26 16:21    [W:4.259 / U:0.020 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site