lkml.org 
[lkml]   [2012]   [Sep]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[ 025/218] tcp: fix cwnd reduction for non-sack recovery
    Date
    3.4-stable review patch.  If anyone has any objections, please let me know.

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


    From: Yuchung Cheng <ycheng@google.com>

    [ Upstream commit 7c4a56fec379ac0d7754e0d4da6a7361f1a4fe64 ]

    The cwnd reduction in fast recovery is based on the number of packets
    newly delivered per ACK. For non-sack connections every DUPACK
    signifies a packet has been delivered, but the sender mistakenly
    skips counting them for cwnd reduction.

    The fix is to compute newly_acked_sacked after DUPACKs are accounted
    in sacked_out for non-sack connections.

    Signed-off-by: Yuchung Cheng <ycheng@google.com>
    Acked-by: Nandita Dukkipati <nanditad@google.com>
    Acked-by: Neal Cardwell <ncardwell@google.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    ---
    net/ipv4/tcp_input.c | 15 +++++++--------
    1 file changed, 7 insertions(+), 8 deletions(-)

    --- a/net/ipv4/tcp_input.c
    +++ b/net/ipv4/tcp_input.c
    @@ -3037,13 +3037,14 @@ static void tcp_update_cwnd_in_recovery(
    * tcp_xmit_retransmit_queue().
    */
    static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked,
    - int newly_acked_sacked, bool is_dupack,
    + int prior_sacked, bool is_dupack,
    int flag)
    {
    struct inet_connection_sock *icsk = inet_csk(sk);
    struct tcp_sock *tp = tcp_sk(sk);
    int do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) &&
    (tcp_fackets_out(tp) > tp->reordering));
    + int newly_acked_sacked = 0;
    int fast_rexmit = 0, mib_idx;

    if (WARN_ON(!tp->packets_out && tp->sacked_out))
    @@ -3103,6 +3104,7 @@ static void tcp_fastretrans_alert(struct
    tcp_add_reno_sack(sk);
    } else
    do_lost = tcp_try_undo_partial(sk, pkts_acked);
    + newly_acked_sacked = pkts_acked + tp->sacked_out - prior_sacked;
    break;
    case TCP_CA_Loss:
    if (flag & FLAG_DATA_ACKED)
    @@ -3124,6 +3126,7 @@ static void tcp_fastretrans_alert(struct
    if (is_dupack)
    tcp_add_reno_sack(sk);
    }
    + newly_acked_sacked = pkts_acked + tp->sacked_out - prior_sacked;

    if (icsk->icsk_ca_state <= TCP_CA_Disorder)
    tcp_try_undo_dsack(sk);
    @@ -3695,7 +3698,6 @@ static int tcp_ack(struct sock *sk, cons
    int prior_packets;
    int prior_sacked = tp->sacked_out;
    int pkts_acked = 0;
    - int newly_acked_sacked = 0;
    int frto_cwnd = 0;

    /* If the ack is older than previous acks
    @@ -3768,8 +3770,6 @@ static int tcp_ack(struct sock *sk, cons
    flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una);

    pkts_acked = prior_packets - tp->packets_out;
    - newly_acked_sacked = (prior_packets - prior_sacked) -
    - (tp->packets_out - tp->sacked_out);

    if (tp->frto_counter)
    frto_cwnd = tcp_process_frto(sk, flag);
    @@ -3783,7 +3783,7 @@ static int tcp_ack(struct sock *sk, cons
    tcp_may_raise_cwnd(sk, flag))
    tcp_cong_avoid(sk, ack, prior_in_flight);
    is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP));
    - tcp_fastretrans_alert(sk, pkts_acked, newly_acked_sacked,
    + tcp_fastretrans_alert(sk, pkts_acked, prior_sacked,
    is_dupack, flag);
    } else {
    if ((flag & FLAG_DATA_ACKED) && !frto_cwnd)
    @@ -3798,7 +3798,7 @@ static int tcp_ack(struct sock *sk, cons
    no_queue:
    /* If data was DSACKed, see if we can undo a cwnd reduction. */
    if (flag & FLAG_DSACKING_ACK)
    - tcp_fastretrans_alert(sk, pkts_acked, newly_acked_sacked,
    + tcp_fastretrans_alert(sk, pkts_acked, prior_sacked,
    is_dupack, flag);
    /* If this ack opens up a zero window, clear backoff. It was
    * being used to time the probes, and is probably far higher than
    @@ -3818,8 +3818,7 @@ old_ack:
    */
    if (TCP_SKB_CB(skb)->sacked) {
    flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una);
    - newly_acked_sacked = tp->sacked_out - prior_sacked;
    - tcp_fastretrans_alert(sk, pkts_acked, newly_acked_sacked,
    + tcp_fastretrans_alert(sk, pkts_acked, prior_sacked,
    is_dupack, flag);
    }




    \
     
     \ /
      Last update: 2012-09-29 01:01    [W:4.042 / U:0.248 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site